Ti6A14V钛合金由于耐热性高、比刚度、比强度高以及抗腐蚀性能强等诸多优点而被广泛应用于航空、航天、海洋和汽车等领域。钛合金高速切削加工过程中涉及到高应变率、高速、大变形、高温差以及复杂的相变过程,因此对于钛合金高速切削加工中的力学过程很难进行精确的解析计算,目前多停留在有限元法计算阶段。常规的拉格朗日有限元法在高速切削数值模拟过程中常遇到网格严重扭曲和畸变的情况,这将使得计算步长过小或者出现单元负体积现象,并导致计算工作量大增,甚至造成计算终止。在有限元法中如果人为限制单元网格的变形程度将影响到计算结果的精确度,甚至使计算结果失真。为了克服有限元法在计算过程中出现的网格畸变的弱点,近几年来国际上许多著名的计算力学学者发展了无网格方法。质点类无网格法不存在数值模拟过程中的网格畸变问题,其中光滑粒子质点法SPH(Smoothed Particle Hydrodynamics)和物质点法MPM(Material Point Method)已经在诸多工程领域获得了广泛的应用。物质点法(MPM)具有欧拉法与拉格朗日法的优点,其在固体力学的高应变率、高速和大变形等数值模拟方面更是得到了非常成功的应用,非常有利于模拟计算高速切削过程。本文在物质点(MPM)接触算法基础上,开发出包含热传导计算的物质点算法程序和相变计算的物质点算法程序,结合修正的Johnson-Cook热粘塑性本构模型对钛合金高速切削过程进行数值模拟,并将不同切削厚度与不同切削速度情况下的数值模拟结果与实验数据进行对比和讨论,发现二者基本吻合,从而证实在考虑热传导及重结晶影响下利用物质点法对高速切削进行数值模拟的有效性。
In this report,the stability of the moving least squares(MLS)approximation is *** is shown that the stability deteriorates severely as the nodal spacing ***,a stabilized MLS approximation is *** stability and error es...
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In this report,the stability of the moving least squares(MLS)approximation is *** is shown that the stability deteriorates severely as the nodal spacing ***,a stabilized MLS approximation is *** stability and error estimates of the stabilized MLS approximation are derived theoretically and verified *** stabilized MLS approximation is further introduced into the element-free Galerkin(EFG)method to produce a stabilized EFG *** analysis of the stabilized EFG method is provided for boundary value problems with mixed boundary *** examples are finally given to demonstrate the theoretical results.
An additional feature for modelling cracks in Material Point Method(MPM)is *** new method,called extended Material Point Method(XMPM),enriches the nodal degree of freedom based on the idea of extended Finite Eleme...
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An additional feature for modelling cracks in Material Point Method(MPM)is *** new method,called extended Material Point Method(XMPM),enriches the nodal degree of freedom based on the idea of extended Finite Element Method(XFEM).This technique allows the crack problem,which are displacement and velocity discontinuous,to be simulated by only one set of background grid mesh,and so multigrid or multiple velocity fields is not *** easily tracking the crack surface,Level Set Method(LSM)is introduced in MPM *** crack moves with the material points physically and the LSM function value is mapped to the grid nodes from particles in each time step,which finds the nodes to be enriched *** experiments for stress fields distribution and fracture parameters calculation are provided to demonstrate the accuracy of *** the results agree well with analytical solutions and that of other numerical *** is developed for two-dimensional applications but it will be easily extended to three-dimension.
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