Contact reactions of guide surfaces of assembly interfaces lead to the decreasing of theirs lateral and angular misalignments. The focus of this paper is the development of algorithms for computation of guide surfaces...Contact reactions of guide surfaces of assembly interfaces lead to the decreasing of theirs lateral and angular misalignments. The focus of this paper is the development of algorithms for computation of guide surfaces contact forces with acceptable engineering accuracy for real time simulation of assembly operations. Therefore, each complex guide surface is described as a set of contacting elements. Each contacting element for one＇s part can be represented by a finite set of geometric primitives which geometry is described by low order algebraic equations. So contact conditions and geometric parameters for all pairs of primitives are determined by analytical expressions. Math models are developed for two classes of contact interaction. The first class includes all cases when each contacting surface has several degrees of freedom of motion. Therefore, contact reactions introduced into differential equations of motion are calculated by using contacting elements penetrations, stiffness and damping parameters. The second class corresponds to all cases when one of contacting surfaces has insignificant inertia and only one degree of freedom of relative displacement counteracted by a spring. Here contact reactions are calculated from spring tension with any practical accuracy. This is very useful in some practical applications. Presented algorithms provide real time simulation together with some approaches for reduction of redundant comnutations.展开更多
In order to determine the dynamic stress intensity factors(DSIFs)for a single edge crack at the center hole of a finite plate under a compressive step loading parallel to the crack,the finite element method was employ...In order to determine the dynamic stress intensity factors(DSIFs)for a single edge crack at the center hole of a finite plate under a compressive step loading parallel to the crack,the finite element method was employed to solve the cracked plate problem.The square-root stress singularity around the crack tip was simulated by quarter point singular elements collapsed by 8-node two-dimensional isoparametric elements.The DSIFs with and without considering crack face contact situations were evaluated by using the displacement correlation technique,and the influence of contact interaction between crack surfaces on DSIFs was investigated.The numerical results show that if the contact interaction between crack surfaces is ignored,the negative mode I DSIFs may be obtained and a physically impossible interpenetration or overlap of the crack surfaces will occur.Thus the crack face contact has a significant influence on the mode I DSIFs.展开更多
A comprehension of railway dynamic behavior implies the measure of wheel-rail contact forces which are affected by disturbances and errors that are often difficult to be quantified. In this study, a benchmark test cas...A comprehension of railway dynamic behavior implies the measure of wheel-rail contact forces which are affected by disturbances and errors that are often difficult to be quantified. In this study, a benchmark test case is proposed, and a bogie with a layout used on some European locomotives such as SIEMENS El90 is studied. In this layout, an additional shaft on which brake disks are installed is used to transmit the braking torque to the wheelset through a single-stage gearbox. Using a mixed approach based on finite element techniques and statistical considerations, it is possible to evaluate an optimal layout for strain gauge positioning and to optimize the measurement system to diminish the effects of noise and disturbance. We also conducted preliminary evaluations on the precision and frequency response of the proposed system.展开更多
The effect of open porosity of Y2O3ceramic on the apparent contact angle and interaction between molten Ti47 Al alloy and Y2O3ceramic substrates under pure Ar was investigated by using a sessile drop method at 1600 &#...The effect of open porosity of Y2O3ceramic on the apparent contact angle and interaction between molten Ti47 Al alloy and Y2O3ceramic substrates under pure Ar was investigated by using a sessile drop method at 1600 °C. As the open porosity increased from 9.6% to 30.3%, the spreading rate of molten Ti47 Al alloys on Y2O3ceramic substrates reduced from 2.3 to 1.1°/s; meanwhile, the final equilibrium contact angles increased from 55.8° to 63.6°. The microstructure observations revealed that with increasing the open porosity of the Y2O3substrates, the thickness of sand adhesion at the interfaces of the alloy droplets increased from 5.4 to 15.7 lm, and ceramic particles in the alloy matrix increased as well. The increasing contact area between the molten alloy and the substrate played a dominant role in determining the interaction on Ti Al/Y2O3interface.展开更多
This paper uses a mathematical method to develop an analytical solution to the local buckling behaviour of long rectangular plates resting on tensionless elastic Winkler foundations and under combined uniform longitud...This paper uses a mathematical method to develop an analytical solution to the local buckling behaviour of long rectangular plates resting on tensionless elastic Winkler foundations and under combined uniform longitudinal uniaxial compressive and uniform in-plane shear loads. Fitted formulas are derived for plates with clamped edges and simplified supported edges. Two examples are given to demonstrate the application of the current method： one is a plate on tensionless spring foundations and the other is the contact between the steel sheet and elastic solid foundation. Finite element （FE） analysis is also conducted to validate the analytical results. Good agreement is obtained between the current method and FE analysis.展开更多
A numerical–analytical approach is described to investigate the process of impact interaction between a long smooth rigid body and the surface of a circular cylindrical cavity in elastic space. A non-stationary mixed...A numerical–analytical approach is described to investigate the process of impact interaction between a long smooth rigid body and the surface of a circular cylindrical cavity in elastic space. A non-stationary mixed initial boundary value problem is formulated with a priori unknown boundaries moving with variable velocity. The problem is solved using the methods of the theory of integral transforms, expansion of desired variables into a Fourier series, and the quadrature method to reduce the problem to solving a system of linear algebraic equations at each time step. Some concrete numerical computations are presented.The cylindrical body mass and radius impact on the proile of the transient process of contact interaction has been analysed.展开更多
Soft pneumatic robotic grippers have found extensive applica-tions across various engineering domains,which prompts active research due to their splendid compliance,high flex-ibility,and safe human-robot interaction o...Soft pneumatic robotic grippers have found extensive applica-tions across various engineering domains,which prompts active research due to their splendid compliance,high flex-ibility,and safe human-robot interaction over conventional stiff counterparts.Previously simplified rod-based models prin-cipally focused on clarifying overall large deformation and bending postures of soft grippers from static or quasi-static perspectives,whereas it is challenging to elaborate grasping characteristics of soft grippers without considering contact interaction and nonlinear large deformation behaviors.To address this,based on absolute nodal coordinate formulation(ANCF),comprehensively allowing for structural complexity,geometric,material and boundary nonlinearities,and incorpor-ating Coulomb’friction law with a multiple-point contact method,we put forward an effective nonlinear dynamic mod-eling approach for exploring grasping capability of soft grip-per.Moreover,we solved the established dynamic equations using Generalized-αscheme,and conducted thorough numer-ical simulation analysis on a three-jaw soft pneumatic gripper(SPG)in terms of grasping configurations,displacements and contact forces.The proposed dynamic approach can accurately both describe complicated deformed configurations along with stress distribution and provide a feasible solution to simulate grasping targets,whose effectiveness and precision were analyzed theoretically and verified experimentally,which may shed new light on devising and optimizing other multi-functional SPGs.展开更多
文摘Contact reactions of guide surfaces of assembly interfaces lead to the decreasing of theirs lateral and angular misalignments. The focus of this paper is the development of algorithms for computation of guide surfaces contact forces with acceptable engineering accuracy for real time simulation of assembly operations. Therefore, each complex guide surface is described as a set of contacting elements. Each contacting element for one＇s part can be represented by a finite set of geometric primitives which geometry is described by low order algebraic equations. So contact conditions and geometric parameters for all pairs of primitives are determined by analytical expressions. Math models are developed for two classes of contact interaction. The first class includes all cases when each contacting surface has several degrees of freedom of motion. Therefore, contact reactions introduced into differential equations of motion are calculated by using contacting elements penetrations, stiffness and damping parameters. The second class corresponds to all cases when one of contacting surfaces has insignificant inertia and only one degree of freedom of relative displacement counteracted by a spring. Here contact reactions are calculated from spring tension with any practical accuracy. This is very useful in some practical applications. Presented algorithms provide real time simulation together with some approaches for reduction of redundant comnutations.
基金Sponsored by the National Natural Science Foundation of China(Grant No.10272036)
文摘In order to determine the dynamic stress intensity factors(DSIFs)for a single edge crack at the center hole of a finite plate under a compressive step loading parallel to the crack,the finite element method was employed to solve the cracked plate problem.The square-root stress singularity around the crack tip was simulated by quarter point singular elements collapsed by 8-node two-dimensional isoparametric elements.The DSIFs with and without considering crack face contact situations were evaluated by using the displacement correlation technique,and the influence of contact interaction between crack surfaces on DSIFs was investigated.The numerical results show that if the contact interaction between crack surfaces is ignored,the negative mode I DSIFs may be obtained and a physically impossible interpenetration or overlap of the crack surfaces will occur.Thus the crack face contact has a significant influence on the mode I DSIFs.
文摘A comprehension of railway dynamic behavior implies the measure of wheel-rail contact forces which are affected by disturbances and errors that are often difficult to be quantified. In this study, a benchmark test case is proposed, and a bogie with a layout used on some European locomotives such as SIEMENS El90 is studied. In this layout, an additional shaft on which brake disks are installed is used to transmit the braking torque to the wheelset through a single-stage gearbox. Using a mixed approach based on finite element techniques and statistical considerations, it is possible to evaluate an optimal layout for strain gauge positioning and to optimize the measurement system to diminish the effects of noise and disturbance. We also conducted preliminary evaluations on the precision and frequency response of the proposed system.
基金support of the‘‘National Science&Technology Pillar Program of China’’project of PR China(No.2013BAB11B04)the National Natural Science Foundation of China(Grant No.51404017)the State Key Laboratory of Refractories and Metallurgy,Wuhan University of Science and Technolog
文摘The effect of open porosity of Y2O3ceramic on the apparent contact angle and interaction between molten Ti47 Al alloy and Y2O3ceramic substrates under pure Ar was investigated by using a sessile drop method at 1600 °C. As the open porosity increased from 9.6% to 30.3%, the spreading rate of molten Ti47 Al alloys on Y2O3ceramic substrates reduced from 2.3 to 1.1°/s; meanwhile, the final equilibrium contact angles increased from 55.8° to 63.6°. The microstructure observations revealed that with increasing the open porosity of the Y2O3substrates, the thickness of sand adhesion at the interfaces of the alloy droplets increased from 5.4 to 15.7 lm, and ceramic particles in the alloy matrix increased as well. The increasing contact area between the molten alloy and the substrate played a dominant role in determining the interaction on Ti Al/Y2O3interface.
文摘This paper uses a mathematical method to develop an analytical solution to the local buckling behaviour of long rectangular plates resting on tensionless elastic Winkler foundations and under combined uniform longitudinal uniaxial compressive and uniform in-plane shear loads. Fitted formulas are derived for plates with clamped edges and simplified supported edges. Two examples are given to demonstrate the application of the current method： one is a plate on tensionless spring foundations and the other is the contact between the steel sheet and elastic solid foundation. Finite element （FE） analysis is also conducted to validate the analytical results. Good agreement is obtained between the current method and FE analysis.
文摘A numerical–analytical approach is described to investigate the process of impact interaction between a long smooth rigid body and the surface of a circular cylindrical cavity in elastic space. A non-stationary mixed initial boundary value problem is formulated with a priori unknown boundaries moving with variable velocity. The problem is solved using the methods of the theory of integral transforms, expansion of desired variables into a Fourier series, and the quadrature method to reduce the problem to solving a system of linear algebraic equations at each time step. Some concrete numerical computations are presented.The cylindrical body mass and radius impact on the proile of the transient process of contact interaction has been analysed.
基金supported by Natural Science Foundation of Zhejiang Province (Grant No.LQ22A020003)National Natural Science Foundation of China (Grant No.52075499)for which all authors are grateful.
文摘Soft pneumatic robotic grippers have found extensive applica-tions across various engineering domains,which prompts active research due to their splendid compliance,high flex-ibility,and safe human-robot interaction over conventional stiff counterparts.Previously simplified rod-based models prin-cipally focused on clarifying overall large deformation and bending postures of soft grippers from static or quasi-static perspectives,whereas it is challenging to elaborate grasping characteristics of soft grippers without considering contact interaction and nonlinear large deformation behaviors.To address this,based on absolute nodal coordinate formulation(ANCF),comprehensively allowing for structural complexity,geometric,material and boundary nonlinearities,and incorpor-ating Coulomb’friction law with a multiple-point contact method,we put forward an effective nonlinear dynamic mod-eling approach for exploring grasping capability of soft grip-per.Moreover,we solved the established dynamic equations using Generalized-αscheme,and conducted thorough numer-ical simulation analysis on a three-jaw soft pneumatic gripper(SPG)in terms of grasping configurations,displacements and contact forces.The proposed dynamic approach can accurately both describe complicated deformed configurations along with stress distribution and provide a feasible solution to simulate grasping targets,whose effectiveness and precision were analyzed theoretically and verified experimentally,which may shed new light on devising and optimizing other multi-functional SPGs.
