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RSS2014 Vol. 33, No. 7
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2014, 33(7): 953-956.
doi: 10.13433/j.cnki.1003-8728.2014.0701
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Abstract:
Against the impact of foundation vibration on the dynamic performance of an asymmetric hydraulic cylinderduring the process of TBM' s rock break and excavation, the mathematical model of dynamic responses of theasymmetric hydraulic cylinder under the foundation vibration condition was built, and the dynamic characteristicsunder different foundation vibration parameters were simulated and analyzed. The simulation results show that: thefoundation vibration reduces the dynamic stability of the hydraulic cylinder, and when the combinations of vibrationamplitude and frequency are (3 mm, 50 Hz),(5 mm, 40 Hz) and (8 mm, 30 Hz), the amplitude of the pressurefluctuation of the hydraulic cylinder is approximately 10% of rod chamber's stable pressure value 20 MPa withoutfoundation vibration, reaching the allowed critical pressure fluctuation amplitude of the hydraulic cylinder's normalwork; the trend of piston displacement's fluctuation is consistent with the pressure's fluctuation, and fluctuation'samplitude is positively correlated with vibration amplitude or frequency. These results provide the basis for reducingthe foundation vibration's impact on the dynamic characteristics of the hydraulic cylinder.
Against the impact of foundation vibration on the dynamic performance of an asymmetric hydraulic cylinderduring the process of TBM' s rock break and excavation, the mathematical model of dynamic responses of theasymmetric hydraulic cylinder under the foundation vibration condition was built, and the dynamic characteristicsunder different foundation vibration parameters were simulated and analyzed. The simulation results show that: thefoundation vibration reduces the dynamic stability of the hydraulic cylinder, and when the combinations of vibrationamplitude and frequency are (3 mm, 50 Hz),(5 mm, 40 Hz) and (8 mm, 30 Hz), the amplitude of the pressurefluctuation of the hydraulic cylinder is approximately 10% of rod chamber's stable pressure value 20 MPa withoutfoundation vibration, reaching the allowed critical pressure fluctuation amplitude of the hydraulic cylinder's normalwork; the trend of piston displacement's fluctuation is consistent with the pressure's fluctuation, and fluctuation'samplitude is positively correlated with vibration amplitude or frequency. These results provide the basis for reducingthe foundation vibration's impact on the dynamic characteristics of the hydraulic cylinder.
2014, 33(7): 957-960.
doi: 10.13433/j.cnki.1003-8728.2014.0702
Abstract:
A novel drive train for wind turbines with stepless speed regulation is studied in this paper. The noveldrive train consists of a planetary gear train and a hydrodynamic torque converter with adjustable guide blades. Thenonlinear dynamic mathematical model of the novel drive train with wind turbine is established on the basis ofhydrodynamics energy head theory. A fuzzy PID controller applied to the system is designed based on fuzzy theoryand PID control theory. Numerical simulation of the fuzzy PID controller is carried out by using MATLAB/SIMULINK softwre. Compared with the effect of the traditional PID controller, the fuzzy PID controller hasadvantages with higher precision and smaller overshoot. The results also indicate that the novel drive train based onfuzzy PID control can successfully realize stepless speed regulation with good stability and reliability. The hightransmission efficiency of the system is also proved.
A novel drive train for wind turbines with stepless speed regulation is studied in this paper. The noveldrive train consists of a planetary gear train and a hydrodynamic torque converter with adjustable guide blades. Thenonlinear dynamic mathematical model of the novel drive train with wind turbine is established on the basis ofhydrodynamics energy head theory. A fuzzy PID controller applied to the system is designed based on fuzzy theoryand PID control theory. Numerical simulation of the fuzzy PID controller is carried out by using MATLAB/SIMULINK softwre. Compared with the effect of the traditional PID controller, the fuzzy PID controller hasadvantages with higher precision and smaller overshoot. The results also indicate that the novel drive train based onfuzzy PID control can successfully realize stepless speed regulation with good stability and reliability. The hightransmission efficiency of the system is also proved.
2014, 33(7): 961-964.
doi: 10.13433/j.cnki.1003-8728.2014.0703
Abstract:
For obtaining the mechanism of the ultrasonic vibration honing grinding, the cavitation bubble dynamicsin the ultrasonic vibration honing grinding zone is studied in this paper, regarding the grinding fluid as the workmedium. The motion process of cavitation bubble which is greater than the initial radius is defined as isothermalprocess, and which is less than the initial radius is as adiabatic process. Based on rayleigh-Plesset equation, thedynamic model of single cavitation bubble in the ultrasonic honing was established. The model was simulated byusing 4-5 runge-Kutta method, and the simulation results were compared with those of the dynamics model in thetraditional ultrasonic field. The result shows that the amplitude of the cavitation bubble in the grinding zone ofultrasonic honing is larger, but the frequency is slower, and its movement law is comparatively stable.
For obtaining the mechanism of the ultrasonic vibration honing grinding, the cavitation bubble dynamicsin the ultrasonic vibration honing grinding zone is studied in this paper, regarding the grinding fluid as the workmedium. The motion process of cavitation bubble which is greater than the initial radius is defined as isothermalprocess, and which is less than the initial radius is as adiabatic process. Based on rayleigh-Plesset equation, thedynamic model of single cavitation bubble in the ultrasonic honing was established. The model was simulated byusing 4-5 runge-Kutta method, and the simulation results were compared with those of the dynamics model in thetraditional ultrasonic field. The result shows that the amplitude of the cavitation bubble in the grinding zone ofultrasonic honing is larger, but the frequency is slower, and its movement law is comparatively stable.
2014, 33(7): 965-970.
doi: 10.13433/j.cnki.1003-8728.2014.0704
Abstract:
For the structure feature of myoelectric controlled prosthetic hand (MCPH), the factors to impact thegrasping ability of MCPH were analyzed. Based on the analysis results, the finite element model of the MCPHsystem was established using the MSC/Nastran software. Topology optimization for the MCPH structure wasperformed with the constraints of weight and volume of the structural system by using the minimum structural strainenergy as the objective function. Based on the optimization results, the dynamic characteristics, the force-energycoupling relationship and the transient response excited by an external shock loads transferred from the dynamicresponse of transmission system were analyzed. The results show that the shock, vibration and the reaction time ofthe optimized MCPH are reduced and the grasping reliability has been significantly improved.
For the structure feature of myoelectric controlled prosthetic hand (MCPH), the factors to impact thegrasping ability of MCPH were analyzed. Based on the analysis results, the finite element model of the MCPHsystem was established using the MSC/Nastran software. Topology optimization for the MCPH structure wasperformed with the constraints of weight and volume of the structural system by using the minimum structural strainenergy as the objective function. Based on the optimization results, the dynamic characteristics, the force-energycoupling relationship and the transient response excited by an external shock loads transferred from the dynamicresponse of transmission system were analyzed. The results show that the shock, vibration and the reaction time ofthe optimized MCPH are reduced and the grasping reliability has been significantly improved.
2014, 33(7): 971-974.
doi: 10.13433/j.cnki.1003-8728.2014.0705
Abstract:
The two new approximation algorithms are proposed to compute structural system reliability. After thelimit state of each failure mode is transformed to the random event, the first new method called successiveaccumulated computation method is derivated based on the event probability computation method. The other systemreliability estimation method is realized by building an equivalent linear failure mode of each system failure modestep by step, known as successive equivalent failure mode method. In the two methods above, the failureprobability of structural system is evaluated through the first-dimension and second-dimension standard normaldistribution functions without complex calculation effort. Compared with the some current methods, theircomputational efficiency is improved greatly. Finally examples show that the given two methods are simply, highefficiency and precise enough.
The two new approximation algorithms are proposed to compute structural system reliability. After thelimit state of each failure mode is transformed to the random event, the first new method called successiveaccumulated computation method is derivated based on the event probability computation method. The other systemreliability estimation method is realized by building an equivalent linear failure mode of each system failure modestep by step, known as successive equivalent failure mode method. In the two methods above, the failureprobability of structural system is evaluated through the first-dimension and second-dimension standard normaldistribution functions without complex calculation effort. Compared with the some current methods, theircomputational efficiency is improved greatly. Finally examples show that the given two methods are simply, highefficiency and precise enough.
2014, 33(7): 975-981.
doi: 10.13433/j.cnki.1003-8728.2014.0706
Abstract:
The damping lashing wire method used widely in gas turbine blade vibration reduction is introduced tothe TrT blade in this study. A variety of the models with different cylindrical damping lashing wire structures areestablished. Their mechanical properties are obtained through analyses. Based on the static analysis result of eachmodel, the most ideal damping structure is chosen. Since the key locations such as lashing wire hole, transitionalsurfaces and the groove faces of the two-stage tendon teeth, are probably sensitive to stress, the slicing analyses aregiven focused on them. Secondly, the curves of the lashing wire diameters of the hole and their locations are drawnby using the least square method with the calculated results. Finally, the mechanical characteristics of all dampingstructures are considered comprehensively and the damping structure that has the optimum mechanical property isobtained by using the weighting evaluation method.
The damping lashing wire method used widely in gas turbine blade vibration reduction is introduced tothe TrT blade in this study. A variety of the models with different cylindrical damping lashing wire structures areestablished. Their mechanical properties are obtained through analyses. Based on the static analysis result of eachmodel, the most ideal damping structure is chosen. Since the key locations such as lashing wire hole, transitionalsurfaces and the groove faces of the two-stage tendon teeth, are probably sensitive to stress, the slicing analyses aregiven focused on them. Secondly, the curves of the lashing wire diameters of the hole and their locations are drawnby using the least square method with the calculated results. Finally, the mechanical characteristics of all dampingstructures are considered comprehensively and the damping structure that has the optimum mechanical property isobtained by using the weighting evaluation method.
2014, 33(7): 982-986.
doi: 10.13433/j.cnki.1003-8728.2014.0707
Abstract:
Aiming to improve the dynamic and static characteristics of the machining center column, the multiobjective topology optimization model is established by handling the objectives, maximizing static stiffness andmaximizing the first two order frequencies, with the manner of compromise programming method and efficacycoefficient method based on the modal analysis and the static analysis which are analyzed by using FEM. The multiobjective topology optimization analysis is performed by using ANSYS, and the modal analysis and the staticanalysis are performed on the column again after the column structure is improved based on the optimal distributionof the column structural materials and the design experience of column. The result shows that the mass of thecolumn is decreased and the static and dynamic characteristics are improved significantly.
Aiming to improve the dynamic and static characteristics of the machining center column, the multiobjective topology optimization model is established by handling the objectives, maximizing static stiffness andmaximizing the first two order frequencies, with the manner of compromise programming method and efficacycoefficient method based on the modal analysis and the static analysis which are analyzed by using FEM. The multiobjective topology optimization analysis is performed by using ANSYS, and the modal analysis and the staticanalysis are performed on the column again after the column structure is improved based on the optimal distributionof the column structural materials and the design experience of column. The result shows that the mass of thecolumn is decreased and the static and dynamic characteristics are improved significantly.
2014, 33(7): 987-991.
doi: 10.13433/j.cnki.1003-8728.2014.0708
Abstract:
In this paper, in view of the asynchrony issue between excitation and response of the transmissionsystem, the system dynamic error caused by the flexible shaft which is suspended in the gear box of a 1. 5 MW windturbine was investigated considering the flexibility of the components. The numerical recursive model wasestablished by using D' Alembert' s principle firstly, then simulation and analysis were carried out based on thismodel by using MATLAB software, and an equivalent system was also adopted for comparison and verification. Theresults show that the dynamic error is not only related to the inherent parameters of system but also the external loadimposed on the system; The dynamic errors are consist of synchronization error component and free vibration errorcomponent, and the latter can cause a random fluctuations of the gears. However, the dynamic errors can becompensated partly if the stiffness coefficient of the flexible shaft is increased, and then the stability and accuracy oftransmission system can be improved.
In this paper, in view of the asynchrony issue between excitation and response of the transmissionsystem, the system dynamic error caused by the flexible shaft which is suspended in the gear box of a 1. 5 MW windturbine was investigated considering the flexibility of the components. The numerical recursive model wasestablished by using D' Alembert' s principle firstly, then simulation and analysis were carried out based on thismodel by using MATLAB software, and an equivalent system was also adopted for comparison and verification. Theresults show that the dynamic error is not only related to the inherent parameters of system but also the external loadimposed on the system; The dynamic errors are consist of synchronization error component and free vibration errorcomponent, and the latter can cause a random fluctuations of the gears. However, the dynamic errors can becompensated partly if the stiffness coefficient of the flexible shaft is increased, and then the stability and accuracy oftransmission system can be improved.
2014, 33(7): 992-995.
doi: 10.13433/j.cnki.1003-8728.2014.0709
Abstract:
A mechanical model of multi-bearing rotor system was established, in which the torque excitation andcoupling stiffness of the multi-bearing rotor system were considered. The sensitivity equation of bearing load of rotorsystem to torque excitation was derived by using the transfer matrix method, and the sensitivity matrix of the bearingload to torque excitation was solved. Taking a linear torque excitation as example, the transfer characteristics oflinear torque excitation in multi-bearing rotor system was studied. The results indicated that the varieties of thebearing loads to the same torque excitation in X and Y directions were different. The change amount of the bearingload became larger when the support closes to the location of the torque excitation. The phenomenon of suddenincrease of the bearing load appeared at the position away from the torque excitation.
A mechanical model of multi-bearing rotor system was established, in which the torque excitation andcoupling stiffness of the multi-bearing rotor system were considered. The sensitivity equation of bearing load of rotorsystem to torque excitation was derived by using the transfer matrix method, and the sensitivity matrix of the bearingload to torque excitation was solved. Taking a linear torque excitation as example, the transfer characteristics oflinear torque excitation in multi-bearing rotor system was studied. The results indicated that the varieties of thebearing loads to the same torque excitation in X and Y directions were different. The change amount of the bearingload became larger when the support closes to the location of the torque excitation. The phenomenon of suddenincrease of the bearing load appeared at the position away from the torque excitation.
2014, 33(7): 996-999.
doi: 10.13433/j.cnki.1003-8728.2014.0710
Abstract:
The layout of locating points can effectively reduce the deformation of sheet metal assemblies in thenormal direction. To contrapose the traditional locating point configuration optimization that only focuses on thedeformation of parts under a given force, an assembly model of sheet metal parts was constructed based on finiteelement theory, which considered the combined impact of part deformation under a given force and locating pointposition. Influence coefficient matrix was built by using the influence coefficient method, and a mathematicaloptimization model was created by taking the least absolute value of influence coefficient as objective function.Finally, the genetic algorithm (GA) is used to seek the optima of the model, and a new method of sampling withconsideration of boundary and fixture point is presented to improve uniformity of the initial point of the algorithm.The calculation results show that the influence coefficient of deviation source to assembly error reduced 90 percentcompared with that before optimization.
The layout of locating points can effectively reduce the deformation of sheet metal assemblies in thenormal direction. To contrapose the traditional locating point configuration optimization that only focuses on thedeformation of parts under a given force, an assembly model of sheet metal parts was constructed based on finiteelement theory, which considered the combined impact of part deformation under a given force and locating pointposition. Influence coefficient matrix was built by using the influence coefficient method, and a mathematicaloptimization model was created by taking the least absolute value of influence coefficient as objective function.Finally, the genetic algorithm (GA) is used to seek the optima of the model, and a new method of sampling withconsideration of boundary and fixture point is presented to improve uniformity of the initial point of the algorithm.The calculation results show that the influence coefficient of deviation source to assembly error reduced 90 percentcompared with that before optimization.
2014, 33(7): 1000-1007.
doi: 10.13433/j.cnki.1003-8728.2014.0711
Abstract:
Semi-active dynamic vibration absorbers have been widely applied to control the vibration in dynamicsfor their obvious merits in cost, reliability and power consumption in comparison with the active absorbers. So far,to adjust the stiffness is the main technological measure which determines the performance of the absorber. Thispaper makes a survey on the research status of varied stiffness technologies with analysis of working principles andcomparison of their performances in variant range of stiffness and responding speed as well as reliability. A variedstiffness device of simple structure is also presented.
Semi-active dynamic vibration absorbers have been widely applied to control the vibration in dynamicsfor their obvious merits in cost, reliability and power consumption in comparison with the active absorbers. So far,to adjust the stiffness is the main technological measure which determines the performance of the absorber. Thispaper makes a survey on the research status of varied stiffness technologies with analysis of working principles andcomparison of their performances in variant range of stiffness and responding speed as well as reliability. A variedstiffness device of simple structure is also presented.
2014, 33(7): 1008-1012.
doi: 10.13433/j.cnki.1003-8728.2014.0712
Abstract:
Measurement uncertainty is one of the most import parts of Geometrical Product Specifications (GPS)uncertainty, it will generate a region of uncertainty and affect the judgment of qualified and unqualified products.This paper proposes new rules to judge the products on the basis of measurement uncertainty. It is based on ISO/TS14253-1. Against the traditional rules, which has considered pure data can be produced in inspection systems, thispaper applies measurement uncertainty in automatic inspections. This paper takes the machine developed by thelaboratory as the experiment platform, inspects the end gap of piston ring based on the traditional rules and the newrules respectively. According to the experimental results, automatic inspections based on measurement uncertaintycan effectively reduce the misjudgments.
Measurement uncertainty is one of the most import parts of Geometrical Product Specifications (GPS)uncertainty, it will generate a region of uncertainty and affect the judgment of qualified and unqualified products.This paper proposes new rules to judge the products on the basis of measurement uncertainty. It is based on ISO/TS14253-1. Against the traditional rules, which has considered pure data can be produced in inspection systems, thispaper applies measurement uncertainty in automatic inspections. This paper takes the machine developed by thelaboratory as the experiment platform, inspects the end gap of piston ring based on the traditional rules and the newrules respectively. According to the experimental results, automatic inspections based on measurement uncertaintycan effectively reduce the misjudgments.
2014, 33(7): 1013-1017.
doi: 10.13433/j.cnki.1003-8728.2014.0713
Abstract:
In order to accurately and efficiently evaluate the straightness error, a hybrid optimization algorithm,combining the least squares algorithm and artificial fish swarm algorithm (LS-AFSA) was presented. First, theleast squares line through the center of the measured points was obtained through the improved least squaresalgorithm and the initial solutions of AFSA were randomly generated in the neighboring line vector. Then the axisapproaching the minimum enclosure cylinder was obtained by using the AFSA algorithm via rotation approachingstrategy. A mutation and eliminated mechanism was applied in classic AFSA algorithm to improve the behavior ofartificial fish and the precision and convergence speed of the AFSA were increased. Finally, the experiment alresults show that the present hybrid optimization algorithm has higher accuracy than that via genetic and otheralgorithm, and does more appropriate for precisely evaluating the spatial straightness error.
In order to accurately and efficiently evaluate the straightness error, a hybrid optimization algorithm,combining the least squares algorithm and artificial fish swarm algorithm (LS-AFSA) was presented. First, theleast squares line through the center of the measured points was obtained through the improved least squaresalgorithm and the initial solutions of AFSA were randomly generated in the neighboring line vector. Then the axisapproaching the minimum enclosure cylinder was obtained by using the AFSA algorithm via rotation approachingstrategy. A mutation and eliminated mechanism was applied in classic AFSA algorithm to improve the behavior ofartificial fish and the precision and convergence speed of the AFSA were increased. Finally, the experiment alresults show that the present hybrid optimization algorithm has higher accuracy than that via genetic and otheralgorithm, and does more appropriate for precisely evaluating the spatial straightness error.
2014, 33(7): 1018-1022.
doi: 10.13433/j.cnki.1003-8728.2014.0714
Abstract:
As a core component of electric spindle, ceramic ball bearings as well as its structure parameters play acritical role to the static stiffness of spindle. The impacts of contact angle and preload of ceramic ball bearing on thestatic stiffness of high-speed grinding motorized spindle are studied in this article using finite element method andsimulation skills based on angular contact ball bearing stiffness computational formula. The three-dimensional finiteelement model of the spindle-bearing system is built. radial deformations of spindle front-end and the spindle staticstiffness with various contact angles and bearing preloads are obtained. The fitting curves and formulas, whichcould be benefit to electronic spindle bear selection and structure parameters design, are figured out according tothe simulated results.
As a core component of electric spindle, ceramic ball bearings as well as its structure parameters play acritical role to the static stiffness of spindle. The impacts of contact angle and preload of ceramic ball bearing on thestatic stiffness of high-speed grinding motorized spindle are studied in this article using finite element method andsimulation skills based on angular contact ball bearing stiffness computational formula. The three-dimensional finiteelement model of the spindle-bearing system is built. radial deformations of spindle front-end and the spindle staticstiffness with various contact angles and bearing preloads are obtained. The fitting curves and formulas, whichcould be benefit to electronic spindle bear selection and structure parameters design, are figured out according tothe simulated results.
2014, 33(7): 1023-1026.
doi: 10.13433/j.cnki.1003-8728.2014.0715
Abstract:
A concept called “key behavioral state” was first introduced specifically for machines with adaptablefunctions. Then a weighted digraph model about the behavioral process of the functional transformation of adaptablefunction machines was proposed. Based on this model, an identification matrix of key behavioral states wasdeveloped, whereby three criterions, including the fastest responsibility criterion, the biggest comfort criterion, aswell as the biggest degree criterion were presented to identify the key behavioral state of functionally adaptablemachine. At the same time, the general process about identifying the key behavioral state was summarized. At last,a case study of the multi-function pliers was used to explain the meaning of the key behavioral state and thefeasibility of the proposed methods.
A concept called “key behavioral state” was first introduced specifically for machines with adaptablefunctions. Then a weighted digraph model about the behavioral process of the functional transformation of adaptablefunction machines was proposed. Based on this model, an identification matrix of key behavioral states wasdeveloped, whereby three criterions, including the fastest responsibility criterion, the biggest comfort criterion, aswell as the biggest degree criterion were presented to identify the key behavioral state of functionally adaptablemachine. At the same time, the general process about identifying the key behavioral state was summarized. At last,a case study of the multi-function pliers was used to explain the meaning of the key behavioral state and thefeasibility of the proposed methods.
2014, 33(7): 1027-1030.
doi: 10.13433/j.cnki.1003-8728.2014.0716
Abstract:
CMP (chemical mechanical polishing) experiments of sapphire substrates were carried out by usinghome-made slurry in order to study the effect of chelating agent on chemical mechanical polishing quality ofsapphire. The comprehensive effects of the polishing down force, pH value, SiO2 concentration, the species andthe concentration of chelating agent as well as particle concentration on the material removal rate (Mrr) wereinvestigated in detail. The surface of the polished sapphire was characterized by D5A-type multi-mode scanningprobe microscope. The experimental results reveal that Mrr can reach 35. 3 nm/min and the surface roughnessaverage (ra) can reach 0. 1 nm under the following CMP conditions: the down pressure force is 7 psi, polishingrotation speed is 50 r/min, polishing liquid is 60 mL/min; and ingredients of slurry: SiO2 concentration is 5%(mass fraction), pH = 12. 0, and chelating agent Ⅰ concentration is 1. 25%.
CMP (chemical mechanical polishing) experiments of sapphire substrates were carried out by usinghome-made slurry in order to study the effect of chelating agent on chemical mechanical polishing quality ofsapphire. The comprehensive effects of the polishing down force, pH value, SiO2 concentration, the species andthe concentration of chelating agent as well as particle concentration on the material removal rate (Mrr) wereinvestigated in detail. The surface of the polished sapphire was characterized by D5A-type multi-mode scanningprobe microscope. The experimental results reveal that Mrr can reach 35. 3 nm/min and the surface roughnessaverage (ra) can reach 0. 1 nm under the following CMP conditions: the down pressure force is 7 psi, polishingrotation speed is 50 r/min, polishing liquid is 60 mL/min; and ingredients of slurry: SiO2 concentration is 5%(mass fraction), pH = 12. 0, and chelating agent Ⅰ concentration is 1. 25%.
2014, 33(7): 1031-1035.
doi: 10.13433/j.cnki.1003-8728.2014.0717
Abstract:
To verify the correctness of the slotting model for external elliptic gears, and to compare the toothaccuracy slotted with multiple schemes, several 3D-simulational mathematical models of slotting elliptic gears andslotting cutter were built by using MATLAB software based on the meshing principle of non-circular gears. Severalsimulation schemes including equal arc-length of workpiece, equal rotary-angle of workpiece, equal polar-angle ofworkpiece in plane, extra rotation of workpiece, extra rotation of slotting cutter and no extra rotation along axle werebuilt. The tool path of each scheme was simulated, which shows that the mathematical models and simulationtechniques of slotting elliptic gears are correct and feasible. The scheme of equal arc-length of workpiece has thehighest accuracy with the same efficiency and tooth accuracy only depends on motion pattern in plane under thesame stroke speed of slotting cutter.
To verify the correctness of the slotting model for external elliptic gears, and to compare the toothaccuracy slotted with multiple schemes, several 3D-simulational mathematical models of slotting elliptic gears andslotting cutter were built by using MATLAB software based on the meshing principle of non-circular gears. Severalsimulation schemes including equal arc-length of workpiece, equal rotary-angle of workpiece, equal polar-angle ofworkpiece in plane, extra rotation of workpiece, extra rotation of slotting cutter and no extra rotation along axle werebuilt. The tool path of each scheme was simulated, which shows that the mathematical models and simulationtechniques of slotting elliptic gears are correct and feasible. The scheme of equal arc-length of workpiece has thehighest accuracy with the same efficiency and tooth accuracy only depends on motion pattern in plane under thesame stroke speed of slotting cutter.
2014, 33(7): 1036-1039.
doi: 10.13433/j.cnki.1003-8728.2014.0718
Abstract:
The simulation for three dimensional milling process based on finite element method has greatsignificance for improving process parameters and realizing high efficiency and high quality machining. In thispaper, a three dimensional finite element model for milling Ti6Al4V alloy workpiece which was closer to the actualmilling process was developed. The formation process of chip was simulated, and its morphology was similar withthe experimented chip morphology. The contours for stress and temperature of workpiece and the cutting forcesunder various milling speeds were simulated with this model. Milling force experiments were carried out under thesame cutting conditions as those of the simulations. The correctness of the simulation model was verified by the goodagreement between the simulated results and the experimental results, and the presented model cn be further usedin the optimization of milling parameters.
The simulation for three dimensional milling process based on finite element method has greatsignificance for improving process parameters and realizing high efficiency and high quality machining. In thispaper, a three dimensional finite element model for milling Ti6Al4V alloy workpiece which was closer to the actualmilling process was developed. The formation process of chip was simulated, and its morphology was similar withthe experimented chip morphology. The contours for stress and temperature of workpiece and the cutting forcesunder various milling speeds were simulated with this model. Milling force experiments were carried out under thesame cutting conditions as those of the simulations. The correctness of the simulation model was verified by the goodagreement between the simulated results and the experimental results, and the presented model cn be further usedin the optimization of milling parameters.
2014, 33(7): 1040-1044.
doi: 10.13433/j.cnki.1003-8728.2014.0719
Abstract:
In accordance with the requirement of opposed-piston hydraulic free piston engine (OPHFPE), wedesigned a new form of solenoid valve with large flow and quick response, and the factors affecting the dynamicresponse of the valve are emphatically researched and analyzed. A finite element model of the solenoid valve,providing the basis for analysis, is established by Ansoft Maxwell. Meanwhile the experimental facility has alsobeen set up. The accuracy of the valve model can be testified by comparing simulation data and experimental data.The results show that the maximum deviation is 0. 67 ms in closing process and 0. 38 ms in opening process. Itindicates that the primary influence factors include shielding magnetism cushion, magnetic material and spring pretightening force, the secondary influence factor is the free lift owing to its influence center on open response, andthe tertiary one is the mass of the moving parts.
In accordance with the requirement of opposed-piston hydraulic free piston engine (OPHFPE), wedesigned a new form of solenoid valve with large flow and quick response, and the factors affecting the dynamicresponse of the valve are emphatically researched and analyzed. A finite element model of the solenoid valve,providing the basis for analysis, is established by Ansoft Maxwell. Meanwhile the experimental facility has alsobeen set up. The accuracy of the valve model can be testified by comparing simulation data and experimental data.The results show that the maximum deviation is 0. 67 ms in closing process and 0. 38 ms in opening process. Itindicates that the primary influence factors include shielding magnetism cushion, magnetic material and spring pretightening force, the secondary influence factor is the free lift owing to its influence center on open response, andthe tertiary one is the mass of the moving parts.
2014, 33(7): 1045-1048.
doi: 10.13433/j.cnki.1003-8728.2014.0720
Abstract:
The performance of small bore swirl chamber diesel engine in China is not well, especially the emissionand the stability at low idling speed which become the pressing issue in internal combustion factories. Presently thevital problem lays that the oversize of needle lift and flow area of the ZS4S1 nozzle make the needle cannot open up,which leads to the low injection pressure and poor performance of fuel oil atomization. Taking 170F diesel enginefor example, the fuel injection system of the prototype is optimized in this study to improve the engine overallperformances. According the fuel quantity of per-cycle, this paper uses HYDSIM software to simulate the injectionprocess with different plans, and designs new characteristics of fuel flow and new nozzle. The experiments of newnozzle and ZS4S1 nozzle in prototype show that: in rated power, the fuel consumption rate has decreased nearly13%, the smoke has dropped 80%; the idling speed has declined to 950 r/min from 1 700 r/min.
The performance of small bore swirl chamber diesel engine in China is not well, especially the emissionand the stability at low idling speed which become the pressing issue in internal combustion factories. Presently thevital problem lays that the oversize of needle lift and flow area of the ZS4S1 nozzle make the needle cannot open up,which leads to the low injection pressure and poor performance of fuel oil atomization. Taking 170F diesel enginefor example, the fuel injection system of the prototype is optimized in this study to improve the engine overallperformances. According the fuel quantity of per-cycle, this paper uses HYDSIM software to simulate the injectionprocess with different plans, and designs new characteristics of fuel flow and new nozzle. The experiments of newnozzle and ZS4S1 nozzle in prototype show that: in rated power, the fuel consumption rate has decreased nearly13%, the smoke has dropped 80%; the idling speed has declined to 950 r/min from 1 700 r/min.
2014, 33(7): 1049-1052.
doi: 10.13433/j.cnki.1003-8728.2014.0721
Abstract:
In this paper, the wind pressure on a phased array antenna in atmospheric boundary layer has beensimulated based on the reynolds-averaged N-S equations and reynolds stress equation model (rSM), and thecharacteristics of the wind pressure distribution has been analyzed. Based on the above-analyzed, the influence lawsof wind loads caused by wind direction and elevation angle are studied, and which is compared with the tested dataobtained via industrial wind-tunnel. The calculated results show that the change law of motional wind loads on theantenna in atmospheric boundary layer is in an agreement with the tested, but there are some differences of windloads on the antenna between the calculated with the tested via wind-tunnel for the differences power law of windprofile. Furthermore, the influence law of wind loads on the antenna in atmospheric boundary layer caused byelevation angle has been calculated. Through the computation for the wind pressure and wind loads on the antenna,the change law of wind loads during rotation is obtained. Therefore, the present results have a widespreaduniversality and important application value in engineereing.
In this paper, the wind pressure on a phased array antenna in atmospheric boundary layer has beensimulated based on the reynolds-averaged N-S equations and reynolds stress equation model (rSM), and thecharacteristics of the wind pressure distribution has been analyzed. Based on the above-analyzed, the influence lawsof wind loads caused by wind direction and elevation angle are studied, and which is compared with the tested dataobtained via industrial wind-tunnel. The calculated results show that the change law of motional wind loads on theantenna in atmospheric boundary layer is in an agreement with the tested, but there are some differences of windloads on the antenna between the calculated with the tested via wind-tunnel for the differences power law of windprofile. Furthermore, the influence law of wind loads on the antenna in atmospheric boundary layer caused byelevation angle has been calculated. Through the computation for the wind pressure and wind loads on the antenna,the change law of wind loads during rotation is obtained. Therefore, the present results have a widespreaduniversality and important application value in engineereing.
2014, 33(7): 1053-1057.
doi: 10.13433/j.cnki.1003-8728.2014.0722
Abstract:
A new typed positioning mechanism was described, which can promote the accuracy of ultra short baseline (USBL) acoustic positioning system. The mechanism adopts dual-shaft multi-row chain structure for powertransmission, using linear guideway for guidance and positioning of the spindle and employ large self-sealing plainbearings for directional. The finite element method is used to make sure that the deflection angle is less than 0. 1皏ia ANSYS, which is far less than 1皌hat is the current deflection angle, while the positioning spindle out of thehull 3 meters and the hull's speed not more than 6 knots. And also the positioning accuracy is less than 0. 2 mm.The onshore test confirms the reliability and maintenance of the mechanism. It is provided that the accuracy of themechanism improves the overall positioning accuracy of the USBL.
A new typed positioning mechanism was described, which can promote the accuracy of ultra short baseline (USBL) acoustic positioning system. The mechanism adopts dual-shaft multi-row chain structure for powertransmission, using linear guideway for guidance and positioning of the spindle and employ large self-sealing plainbearings for directional. The finite element method is used to make sure that the deflection angle is less than 0. 1皏ia ANSYS, which is far less than 1皌hat is the current deflection angle, while the positioning spindle out of thehull 3 meters and the hull's speed not more than 6 knots. And also the positioning accuracy is less than 0. 2 mm.The onshore test confirms the reliability and maintenance of the mechanism. It is provided that the accuracy of themechanism improves the overall positioning accuracy of the USBL.
Optimal Design of the rotating Device of AB Shaft Mechanisms in the Large radio Telescope Feed Cabin
2014, 33(7): 1058-1061.
doi: 10.13433/j.cnki.1003-8728.2014.0723
Abstract:
Aiming at the rotation device of the AB shaft mechanisms in large radio telescope feed cabin, we analyzed thereasons of large driving torque on AB shaft. Based on the design of the AB shaft mechanisms, starting from driving torqueof A shaft and B shaft, the position of rotation center was redesigned and achieved the optimal design of the rotationdevice of AB shaft mechanisms. The deformations of the AB shaft mechanisms before and after optimal design areobtained, respectively, by finite element analysis. The results showed that the maximum deformation of the AB shaftmechanisms was reduced, and the effectiveness of the optimal design was verified. The study provides a significantreference for the optimal design of the AB shaft mechanisms.
Aiming at the rotation device of the AB shaft mechanisms in large radio telescope feed cabin, we analyzed thereasons of large driving torque on AB shaft. Based on the design of the AB shaft mechanisms, starting from driving torqueof A shaft and B shaft, the position of rotation center was redesigned and achieved the optimal design of the rotationdevice of AB shaft mechanisms. The deformations of the AB shaft mechanisms before and after optimal design areobtained, respectively, by finite element analysis. The results showed that the maximum deformation of the AB shaftmechanisms was reduced, and the effectiveness of the optimal design was verified. The study provides a significantreference for the optimal design of the AB shaft mechanisms.
2014, 33(7): 1062-1066.
doi: 10.13433/j.cnki.1003-8728.2014.0724
Abstract:
Expandable liner hanger sets in the casing and hangs liners by expanding mental hanger body.Expansion force is a key technical index for liner hanger. In this paper, the key factors that affect the expansionforce such as expandable cone angle, body structure, and frictional coefficient between cone and body are computedby using LS-DYNA. And the computation results are tested nearly accurately by expansion experiments andmetallographic observation. Characteristics and rules that affect expansion force are obtained by numerical computation,which provide an important reference to choose material and optimize structural design of expandable liner hanger.
Expandable liner hanger sets in the casing and hangs liners by expanding mental hanger body.Expansion force is a key technical index for liner hanger. In this paper, the key factors that affect the expansionforce such as expandable cone angle, body structure, and frictional coefficient between cone and body are computedby using LS-DYNA. And the computation results are tested nearly accurately by expansion experiments andmetallographic observation. Characteristics and rules that affect expansion force are obtained by numerical computation,which provide an important reference to choose material and optimize structural design of expandable liner hanger.
2014, 33(7): 1067-1070.
doi: 10.13433/j.cnki.1003-8728.2014.0725
Abstract:
High energy consumption, low-level efficiency, and high production cost were the main problems whenbeam-pumping unit was used in production, and the energy retro-flow occurred when the rod fall due to own weightin the down stroke made the motor in a state of electric power generating. Based on the theories of mechanisminnovation and parallel mechanism, a new design to use beam unit match was put forward in order to resolve theabove problems. The present method realized the positive transfer of the energy, and made the best use of theenergy because the energy retro-flow produced by one beam unit was transferred to another one through the crank.It increased production efficiency because one circle of the crank produced two working strokes in the beam unitmatch. The torque characteristic parameters were obtained by the computer calculation. Comparing with theconventional pumping unit and heterogeneous one, the match-use of the pumping unit handles the problem moreeffectively. The present method can be realized by partly modifying the equipment without obsoleting the exitingequipment and the need of overlapping investment.
High energy consumption, low-level efficiency, and high production cost were the main problems whenbeam-pumping unit was used in production, and the energy retro-flow occurred when the rod fall due to own weightin the down stroke made the motor in a state of electric power generating. Based on the theories of mechanisminnovation and parallel mechanism, a new design to use beam unit match was put forward in order to resolve theabove problems. The present method realized the positive transfer of the energy, and made the best use of theenergy because the energy retro-flow produced by one beam unit was transferred to another one through the crank.It increased production efficiency because one circle of the crank produced two working strokes in the beam unitmatch. The torque characteristic parameters were obtained by the computer calculation. Comparing with theconventional pumping unit and heterogeneous one, the match-use of the pumping unit handles the problem moreeffectively. The present method can be realized by partly modifying the equipment without obsoleting the exitingequipment and the need of overlapping investment.
2014, 33(7): 1071-1073.
doi: 10.13433/j.cnki.1003-8728.2014.0726
Abstract:
A new system for inspecting the mature of winter jujube is developed. This automatic inspection systemis composed of an automatic uploading and cutting device, a light source, a CCD camera, a data acquisitionboards, the winter jujube sorter, a controllers, a computer and other hardware and software for image collecting andprocessing. The implementation process of the system are as follows: the controller controls the operation of astepper motor by a mesh belt and the winter jujubes are evenly transported to the stand of the winter jujube sorter,the CCD camera collect a image of winter jujube every two seconds, the motor will stops running during the imageacquisition. The rGB image is transformed into the HIS model space. Then the H component of the HIS model isused to description the color features of the winter jujube. The test results show that the correct rate of identificationis 90% and it can meet the automatic sorting requirements.
A new system for inspecting the mature of winter jujube is developed. This automatic inspection systemis composed of an automatic uploading and cutting device, a light source, a CCD camera, a data acquisitionboards, the winter jujube sorter, a controllers, a computer and other hardware and software for image collecting andprocessing. The implementation process of the system are as follows: the controller controls the operation of astepper motor by a mesh belt and the winter jujubes are evenly transported to the stand of the winter jujube sorter,the CCD camera collect a image of winter jujube every two seconds, the motor will stops running during the imageacquisition. The rGB image is transformed into the HIS model space. Then the H component of the HIS model isused to description the color features of the winter jujube. The test results show that the correct rate of identificationis 90% and it can meet the automatic sorting requirements.
2014, 33(7): 1074-1078.
doi: 10.13433/j.cnki.1003-8728.2014.0727
Abstract:
Ultrasonic inspection is widely used in quality detection of solder joint of white body. There is the lowefficiency of traditional ultrasonic inspection for solder joint. The solder joints are selected only according to theroad test and experience, which takes long time and is lack of the theory of selection method. Focusing in car, themethod of selecting key spot area is proposed, meanwhile the traditional detection method is optimized, and theidear for selecting the key areas in solder joint is stated. By using CAE tool, the strength and impacted performancefor the vehicle performance is analyzed, the solder joints located in the areas that with the high stress and highenergy absorption in collision processes are detected, the results show that the method reduces the number of solderjoints to be detected and meets the main performance of body.
Ultrasonic inspection is widely used in quality detection of solder joint of white body. There is the lowefficiency of traditional ultrasonic inspection for solder joint. The solder joints are selected only according to theroad test and experience, which takes long time and is lack of the theory of selection method. Focusing in car, themethod of selecting key spot area is proposed, meanwhile the traditional detection method is optimized, and theidear for selecting the key areas in solder joint is stated. By using CAE tool, the strength and impacted performancefor the vehicle performance is analyzed, the solder joints located in the areas that with the high stress and highenergy absorption in collision processes are detected, the results show that the method reduces the number of solderjoints to be detected and meets the main performance of body.
2014, 33(7): 1079-1082.
doi: 10.13433/j.cnki.1003-8728.2014.0728
Abstract:
Based on the related performance test methods and standards of automotive radiator, a high-precisionperformance test bench was designed. The heat transfer rate in the range from 0. 96 to 1. 00 for both sides issuperior to the criteria of test stands standard. The complete mathematical model fore louvered fin automotiveradiator has been established on the basis of the analyzed and tested results, the simulation program and simulationmodel have been compiled with Matlab by using an iterative algorithm according to the gauge length to determinethe discharge state of automotive radiator. It was proved that the simulation results were in a good agreement withthe tested results, the heat exchange relative error of air-side was less than 4. 5 %, the heat exchange relative errorof medium-side was less than 4. 7%, the pressure drop relative error of air-side was less than 7. 6%, the pressuredrop relative error of medium-side was less than 9. 5%.
Based on the related performance test methods and standards of automotive radiator, a high-precisionperformance test bench was designed. The heat transfer rate in the range from 0. 96 to 1. 00 for both sides issuperior to the criteria of test stands standard. The complete mathematical model fore louvered fin automotiveradiator has been established on the basis of the analyzed and tested results, the simulation program and simulationmodel have been compiled with Matlab by using an iterative algorithm according to the gauge length to determinethe discharge state of automotive radiator. It was proved that the simulation results were in a good agreement withthe tested results, the heat exchange relative error of air-side was less than 4. 5 %, the heat exchange relative errorof medium-side was less than 4. 7%, the pressure drop relative error of air-side was less than 7. 6%, the pressuredrop relative error of medium-side was less than 9. 5%.
2014, 33(7): 1083-1086.
doi: 10.13433/j.cnki.1003-8728.2014.0729
Abstract:
The nonlinear dynamical equations of the motor tilted support system excited by half-sine pulse wereestablished considering its vulnerable part. The shock responses were obtained numerically using runge-Kuttamethod. To evaluate the shock characteristics of the vulnerable part, a new concept of three-dimensional shockresponse spectra is proposed, which is defined as the ratio of the maximum shock acceleration response of thevulnerable part to the peak value of pulse excitation, the dimensionless pulse duration and the frequency ratio ofsystem were two basic parameters of the three-dimensional shock response spectra. Based on the numerical simulationresults, the effects of the amplitude of pulse excitation, the angle of the tilted support spring and the mass ratio on theshock response spectra are discussed. It is shown that of the amplitude of pulse, the angle of the tilted support springand the frequency ratio of the system have remarkable effects on the shock response peak of the vulnerable part, Toincrease the frequency ratio of the system can obviously reduce the maximum shock response acceleration of thevulnerable part, and it can also be reduced by increasing mass ratio in the case of low frequency ratio. The results ofthe present study provides theoretical foundation for the design of shock absorber of the motor tilted support system.
The nonlinear dynamical equations of the motor tilted support system excited by half-sine pulse wereestablished considering its vulnerable part. The shock responses were obtained numerically using runge-Kuttamethod. To evaluate the shock characteristics of the vulnerable part, a new concept of three-dimensional shockresponse spectra is proposed, which is defined as the ratio of the maximum shock acceleration response of thevulnerable part to the peak value of pulse excitation, the dimensionless pulse duration and the frequency ratio ofsystem were two basic parameters of the three-dimensional shock response spectra. Based on the numerical simulationresults, the effects of the amplitude of pulse excitation, the angle of the tilted support spring and the mass ratio on theshock response spectra are discussed. It is shown that of the amplitude of pulse, the angle of the tilted support springand the frequency ratio of the system have remarkable effects on the shock response peak of the vulnerable part, Toincrease the frequency ratio of the system can obviously reduce the maximum shock response acceleration of thevulnerable part, and it can also be reduced by increasing mass ratio in the case of low frequency ratio. The results ofthe present study provides theoretical foundation for the design of shock absorber of the motor tilted support system.
2014, 33(7): 1087-1090.
doi: 10.13433/j.cnki.1003-8728.2014.0730
Abstract:
Focusing on the secondary regulation simulation loading system for the vehicle's wheels and transmissionbridges, it is found that there is the strong coupling effects in its velocity control system and torque control system,mainly including hydraulic coupling and mechanical coupling. The system control accuracy is significantly reducedand the coupling interferences seriously affect the system performance. In order to eliminate the couplinginterference between the subsystems, two methods were presented, one is to add a decoupling element and thedecoupling control of the system is achieved by solving the decoupling element; The another is to add a robustcontrol compensator and the decoupling control of the system is achieved by robust control. Simulation results showthat good effect on the mechanical coupling is obtained by adding decoupling element, but there is no effect on thepressure interference, while the robust control can not only suppress the mechanical fluctuation, but also suppressthe pressure fluctuation interference greatly.
Focusing on the secondary regulation simulation loading system for the vehicle's wheels and transmissionbridges, it is found that there is the strong coupling effects in its velocity control system and torque control system,mainly including hydraulic coupling and mechanical coupling. The system control accuracy is significantly reducedand the coupling interferences seriously affect the system performance. In order to eliminate the couplinginterference between the subsystems, two methods were presented, one is to add a decoupling element and thedecoupling control of the system is achieved by solving the decoupling element; The another is to add a robustcontrol compensator and the decoupling control of the system is achieved by robust control. Simulation results showthat good effect on the mechanical coupling is obtained by adding decoupling element, but there is no effect on thepressure interference, while the robust control can not only suppress the mechanical fluctuation, but also suppressthe pressure fluctuation interference greatly.
2014, 33(7): 1091-1094.
doi: 10.13433/j.cnki.1003-8728.2014.0731
Abstract:
The fatigue life prediction accuracy for structures based on existing fatigue damage models needs to beimproved further due to the applications of some experience data. In this paper, a new fatigue life prediction modelis presented based on the fatigue load spectrum technique with fatigue loading of virtual equal interval length, andalso calculating the fatigue life through the idea of MINEr. This model is verified through the theoretical andsimulation analysis. Example applications show that the accuracy and credibility of life prediction results of the newmodel have been improved.
The fatigue life prediction accuracy for structures based on existing fatigue damage models needs to beimproved further due to the applications of some experience data. In this paper, a new fatigue life prediction modelis presented based on the fatigue load spectrum technique with fatigue loading of virtual equal interval length, andalso calculating the fatigue life through the idea of MINEr. This model is verified through the theoretical andsimulation analysis. Example applications show that the accuracy and credibility of life prediction results of the newmodel have been improved.
2014, 33(7): 1095-1097.
doi: 10.13433/j.cnki.1003-8728.2014.0732
Abstract:
The aim of the present work is focused on wing-store flutter problem, which is dependence on four typesof design parameters. The structural dynamics models of pylon and store are first established and combined with awing model to build the wing-store flutter model. Compared with the clean wing model, the flutter speed computedfrom the wing-store model decreases up to approximately 50%. Four types of special design parameters areinvestigated for their influence on the wing-store flutter characteristics, namely, the wing fuel tank state, pylonstiffness, chord-wise and span-wise station of the store. Only one of these design parameters is changed in theparametric study each time. Finally, influence of these parameters on the wing-store flutter characteristics isevaluated and some advices are proposed to improve the wing-store flutter characteristics.
The aim of the present work is focused on wing-store flutter problem, which is dependence on four typesof design parameters. The structural dynamics models of pylon and store are first established and combined with awing model to build the wing-store flutter model. Compared with the clean wing model, the flutter speed computedfrom the wing-store model decreases up to approximately 50%. Four types of special design parameters areinvestigated for their influence on the wing-store flutter characteristics, namely, the wing fuel tank state, pylonstiffness, chord-wise and span-wise station of the store. Only one of these design parameters is changed in theparametric study each time. Finally, influence of these parameters on the wing-store flutter characteristics isevaluated and some advices are proposed to improve the wing-store flutter characteristics.
2014, 33(7): 1098-1100.
doi: 10.13433/j.cnki.1003-8728.2014.0733
Abstract:
Sliding wear behavior of 20CrMnTi steel by different heat treatment processes was comparatively studiedon a SrV Ⅳ oscillating friction and wear tester, and the wear mechanism was analyzed. It was shown that: underthe experimental conditions, after carbonitriding + cryogenic treatment + low temperature tempering processing,the sample has the highest surface hardness, which is 842HV0. 2. The sample microstructure is temperedmartensite + carbides + a very small amount of residual austenite. This new technology has been adopted tosuccessfully solve the premature wear failure of small modulus gear in a factory.
Sliding wear behavior of 20CrMnTi steel by different heat treatment processes was comparatively studiedon a SrV Ⅳ oscillating friction and wear tester, and the wear mechanism was analyzed. It was shown that: underthe experimental conditions, after carbonitriding + cryogenic treatment + low temperature tempering processing,the sample has the highest surface hardness, which is 842HV0. 2. The sample microstructure is temperedmartensite + carbides + a very small amount of residual austenite. This new technology has been adopted tosuccessfully solve the premature wear failure of small modulus gear in a factory.
2014, 33(7): 1101-1104.
doi: 10.13433/j.cnki.1003-8728.2014.0734
Abstract:
Porosity breaks continuity of casting, stress concentration and fatigue crack propagation source are easyto occur in these positions. However representation of casting defect features is very constructive, which can' tconstruct the mechanical model containing defects. Aiming at the loader, the heterogeneity grid model with castingdefects has established based on the finite element mesh transmission with defects information superpositionalgorithm, then structure and fatigue comparative analysis of the rocker casting with and without defects has beenconducted. The present results indicate that defects can form local stress concentration under the same loadingconditions. And also the low fatigue life will appear in the around casting defects, the casting defect has reducedthe fatigue life of the rocker casting by one third.
Porosity breaks continuity of casting, stress concentration and fatigue crack propagation source are easyto occur in these positions. However representation of casting defect features is very constructive, which can' tconstruct the mechanical model containing defects. Aiming at the loader, the heterogeneity grid model with castingdefects has established based on the finite element mesh transmission with defects information superpositionalgorithm, then structure and fatigue comparative analysis of the rocker casting with and without defects has beenconducted. The present results indicate that defects can form local stress concentration under the same loadingconditions. And also the low fatigue life will appear in the around casting defects, the casting defect has reducedthe fatigue life of the rocker casting by one third.
2014, 33(7): 1105-1110.
doi: 10.13433/j.cnki.1003-8728.2014.0735
Abstract:
The frequency control method for stall flutter suppression with synthetic jet actuators (SJA) wasproposed. The dynamics equation for high-aspect-ratio composite wing was established. The characteristics of thetraditional flutter of the composite wing were analyzed, and it is found that critical flutter speed was above thecruising speed. Therefore, the amplitude-frequency characteristic of the stall flutter was discussed in detail.Furthermore, the stall flutter suppression strategy was presented with the principle of disturbing the vortex sheddingfrequencies on the wingspan with synthetic jet actuators (SJA) to keep away from the natural frequency of the wing.The feasibility of the proposed method was numerically verified by taking the stall flutter suppression of aNACA0012 airfoil as a case study. The results show that the flutter amplitude is decreased significantly.
The frequency control method for stall flutter suppression with synthetic jet actuators (SJA) wasproposed. The dynamics equation for high-aspect-ratio composite wing was established. The characteristics of thetraditional flutter of the composite wing were analyzed, and it is found that critical flutter speed was above thecruising speed. Therefore, the amplitude-frequency characteristic of the stall flutter was discussed in detail.Furthermore, the stall flutter suppression strategy was presented with the principle of disturbing the vortex sheddingfrequencies on the wingspan with synthetic jet actuators (SJA) to keep away from the natural frequency of the wing.The feasibility of the proposed method was numerically verified by taking the stall flutter suppression of aNACA0012 airfoil as a case study. The results show that the flutter amplitude is decreased significantly.
2014, 33(7): 1111-1116.
doi: 10.13433/j.cnki.1003-8728.2014.0736
Abstract:
In order to rapidly and accurately forecast man-hour of aircraft structure parts without NC programs, amethod for forecasting man-hour based on the features and genetic algorithm are proposed in this paper. A databaseis established according to the influencing factors refined here which determine the man-hour of every feature. Thismethod combines back propagation (BP) neural network with genetic algorithm to deal with the defects of thesteepest descent in slowly converging, easily immerging in partial minimum frequently and difficultly determiningthe optimal parameters. A total of 5 structures of neural networks are established with regard to typical processingtechnology of aircraft structure parts. Man-hour of every machining feature is forecasted by using correspondingstructure, the total of which form the whole man-hour of the parts. The simulation result shows high practical valueof this method with error below 5%.
In order to rapidly and accurately forecast man-hour of aircraft structure parts without NC programs, amethod for forecasting man-hour based on the features and genetic algorithm are proposed in this paper. A databaseis established according to the influencing factors refined here which determine the man-hour of every feature. Thismethod combines back propagation (BP) neural network with genetic algorithm to deal with the defects of thesteepest descent in slowly converging, easily immerging in partial minimum frequently and difficultly determiningthe optimal parameters. A total of 5 structures of neural networks are established with regard to typical processingtechnology of aircraft structure parts. Man-hour of every machining feature is forecasted by using correspondingstructure, the total of which form the whole man-hour of the parts. The simulation result shows high practical valueof this method with error below 5%.
