Robust explicit computational strategies based on penalty method for large-deformation impact problems
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摘要: 为了提高基于罚函数法的显式有限元对大变形接触-碰撞问题仿真的精确性和健壮性,基于前增量位移时间中心差分发展了一种新的大变形接触非侵入算法。将动力方程求解步分解为不考虑接触的预估步与考虑接触的修正步,在当前时刻利用罚函数法施加接触惩罚力,使其满足非侵入条件,从而提高显式接触计算的精确性;为实现在仅能获得下一时刻位移的情况下精确计算下一时刻大变形内力,基于任意参考构型大变形理论将动力学方程内力项映射到已知的构型求解,避免使用相关物理量的中间构型近似值,从而降低大变形计算引入的数值误差。更严格的几何非线性以及接触算法可有效抑制实体间的非物理穿透以及大变形碰撞过程中的单元畸变,提高计算程序的健壮性。通过对典型碰撞及侵彻算例进行仿真并与商业软件结果对比,验证了本文所发展的大变形接触-碰撞显式算法的正确性,同时证明其在高速大变形碰撞仿真方面比基于蛙跳格式中心差分和罚函数法的经典接触-碰撞算法更加健壮。
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关键词:
Abstract: To improve the accuracy and robustness of the explicit FEM algorithm based on penalty method for simulating large deformation contact-impact problem, a new large-deformation non-penetration contact algorithm based on forward incremental displacement central difference (FIDCD) was developed. On the one hand, according to FIDCD, the solving step of the dynamic equation was decomposed into an estimated step without considering contact and a correction step considering contact constraint. At the current moment, a contact force was applied thorough the penalty method to make the deformation of entities satisfy the non-penetration condition. The contact force was calculated by a soft constraint penalty stiffness, which helped to maintain stability of contact localization. It enhanced the numerical accuracy of the explicit contact computation. On the other hand, to accurately calculate the large-deformation internal force of the next moment while only obtaining the displacement, the internal force term of the dynamic equation was mapped to a known configuration for solution based on the arbitrary reference configurations (ARC) theory. It avoided using the values of variables at intermediate configuration to approximate them, thereby improving the numerical accuracy of the large deformation computation. More rigorous contact algorithms and geometric nonlinear solution strategy can effectively suppress mesh distortion and non-physical penetration between entities during large-deformation impact simulation. This thus improved the robustness of the new explicit algorithm. Finally, the computational program written according to the new developed algorithm was applied to simulate several impact and penetration examples with different impact velocities. By comparing the simulation results with those obtained from commercial software, the correctness of the developed algorithm and computational program was verified. At the same time, it can also be proven that the algorithm proposed is more robust in simulating high-speed and large-deformation impact problems than the classical explicit contact-impact algorithm based on the frog jump center difference scheme combining with penalty method.-
Key words:
- contact-impact /
- explicit FEM /
- contact algorithm /
- geometric large deformation /
- penalty method
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