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Transient Impact Analysis of Elastic-plastic Beam with Strain-Rate Sensitivity
International Journal of Impact Engineering ( IF 5.1 ) Pub Date : 2021-03-17 , DOI: 10.1016/j.ijimpeng.2021.103865
Qiming Hao , Xiaochun Yin , Pengbo Qian , Hui Wang , Huaiping Ding , Bo Yu , Qingming Deng , Xiaoyun Dong , Xiaoli Qi

The impact response of an elastic-plastic beam is highly complicated in nonlinear transient dynamics especially when the material's plasticity is strain rate dependent. To reduce the efforts required for the computational analysis, an analytical-numerical model (hybrid model) is proposed for the analysis of the transient response of the beam to sphere impact. The model couples two sub-models, a combined discretization model and a refined contact model. Both the sub-models incorporate the material strain rate dependence. The combined discretization model discretizes the beam in length direction by a dynamic substructure technique and in thickness direction by a finite difference technique to capture the beam wave propagations along the length and the stress variations along the thickness. The refined contact model extends the BD model [1] to sphere-beam impacts by introducing a new representative contact strain rate and a new unloading law to avoided the force discontinuity at the inception of unloading. The hybrid model is validated by the laboratory test performed for low-velocity impacts and by the three-dimensional finite element (FE) analysis implemented for moderate-velocity and moderate high-velocity impacts. The validations show that the hybrid model is accurate, highly efficient and suitable for the parametric study, especially for the study of impact-induced wave effects. By using the hybrid model, tests and FE analyses, the influences of the material strain rate sensitivity are investigated by comparing to the results of elastic plastic impact simulations ignoring the effect of strain rate. It is found that the influence of the strain rate dependence on the contact force-indentation relation is significant even in the low-velocity impacts. The influences of the strain rate dependence on the contact duration and maximum contact force are small, even for the impact velocity up to 30 m/s. The influences of the strain rate dependence on other impact responses are small in the low-velocity impacts, and increase with increasing of the impact velocity. A parametric analysis is conducted to investigate the effects of the impact conditions on the contact duration and coefficient restitution. Their map structures are complicated, depending upon the mass ratio and the impact position. A jumping/falling phenomenon for the variations of the contact duration and coefficient of restitution is found, which are caused by the multiple impacts.



中文翻译:

应变速率敏感性的弹塑性梁的瞬态冲击分析

在非线性瞬态动力学中,尤其是当材料的可塑性取决于应变率时,弹塑性梁的冲击响应非常复杂。为了减少计算分析所需的工作量,提出了一种解析数值模型(混合模型)来分析光束对球体撞击的瞬态响应。该模型耦合了两个子模型,即组合离散模型和精细联系模型。这两个子模型都包含了材料应变率的依赖性。组合离散化模型通过动态子结构技术将梁在长度方向上离散化,并通过有限差分技术在厚度方向上将梁离散化,以捕获沿长度方向的束波传播和沿厚度方向的应力变化。改进的接触模型通过引入新的代表性接触应变率和新的卸荷规律,将BD模型[1]扩展到球梁碰撞,从而避免了在卸荷开始时力的不连续性。通过对低速撞击进行的实验室测试以及对中速和中速撞击实施的三维有限元(FE)分析验证了混合模型。验证表明,该混合模型准确,高效且适用于参数研究,尤其适用于冲击波效应的研究。通过使用混合模型,测试和有限元分析,通过与忽略应变率影响的弹性塑性冲击模拟结果进行比较,研究了材料应变率敏感性的影响。发现即使在低速冲击中,应变率依赖性对接触力-压痕关系的影响也是显着的。即使对于高达30 m / s的冲击速度,应变率对接触持续时间和最大接触力的影响也很小。在低速冲击中,应变率对其他冲击响应的影响很小,并且随着冲击速度的增加而增加。进行参数分析以研究冲击条件对接触持续时间和系数恢复的影响。它们的地图结构很复杂,取决于质量比和撞击位置。发现了接触持续时间和恢复系数变化的跳跃/下降现象,这是由多种影响引起的。

更新日期:2021-04-01
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