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首页> 外文会议>Fourth International Conference on Materials Processing Defects; Sep 24-26, 2002; Cachan, France >Computational Characterization of Micro- to Macroscopic Mechanical Behaviour and Damage of Polymer containing Second-phase Particles
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Computational Characterization of Micro- to Macroscopic Mechanical Behaviour and Damage of Polymer containing Second-phase Particles

机译：包含第二相颗粒的聚合物的微观至宏观力学行为和损伤的计算表征

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摘要

Computational simulations employing a plane-strain unit cell model containing soft rubber particles clarified the effect of stiffness and size of rubber particles, macroscopic strain ratio, and the direction of the unit cell, on the cavitation behavior in the rubber particles and the onset of shear bands and their propagations in the polymer. Also, the relationships between these phenomena and the maximum mean stress in the polymer that directly affects the onset of crazing was investigated. The following is a summary of the results. 1) Regardless of the changes of the parameters in the present investigation, the relations related to the average normal stress versus volume change of the particles are cast into a characteristic single line. 2) The maximum mean stress appears near the front of the shear band for insufficient growth of the shear band connecting the particles and it appears at the inflection point of the inclination of the shear band for the sufficiently developed shear band connecting the particles. The latter point corresponds to the intersection point of the shear bands. 3) Soft rubber particles promote the onset of shear bands connecting the particles and the growth of holes in the particles that lower the maximum value of the mean stress in the polymer. 4) The increase of macroscopic strain ratio results in the increase of volumetric strain of particles, which promotes the plastic deformation of the polymer and the onset of macroscopic yielding with a lower value of yield stress. Due to the high triaxiality of the macroscopic stress, the mean stress in the polymer increases when the strain ratio increases. 5) The volumetric strain of the small particles increases first and the formation of a high-strain-rate region and its propagation are marked near the small particles. The small particles contributes to increase the maximum mean stress in the polymer for the case of a small strain ratio, while regardless of the size of the particles the maximum mean stress is kept almost unchanged for the case with a large strain ratio. The computational strategy employing the homogenization method and the finite element method provides the homogenized constitutive equation accounting all microscopic deformation behavior in the unit cell subjected to macroscopically uniform deformation so that it is straight forward to introduce thus obtained constitutive equations at each material point for macroscopically nonuniform deformation as observed in the forming processes. However, in the present investigation, the cavitation is modeled by introducing small holes in the particles, therefore, onset and growth of cavity is controlled by the deformation behavior of particles and surrounding polymer. To clarify the absolute size effect on controlling cavitation, a suitable length scale should be considered through the introduction of volume strain energy as well as surface energy (Bucknall, 1994). The size of particles may affect the interaction of heterogeneous particles as well, which requires further study.
机译：使用包含软橡胶颗粒的平面应变晶胞模型进行的计算模拟阐明了橡胶颗粒的刚度和大小，宏观应变比以及晶胞的方向对橡胶颗粒中的空化行为和剪切开始的影响带及其在聚合物中的传播。同样，研究了这些现象与直接影响开裂开始的聚合物中最大平均应力之间的关系。以下是结果摘要。 1）无论本研究中的参数如何变化，与平均法向应力与颗粒体积变化相关的关系都被转换为特征单线。 2）最大平均应力出现在剪切带的前端附近，这是因为连接颗粒的剪切带的生长不足，并且最大平均应力出现在剪切带的倾斜度的拐点处，该剪切带的倾斜度足以使连接颗粒的剪切带充分发展。后一点对应于剪切带的交点。 3）软橡胶颗粒促进连接颗粒的剪切带的产生和颗粒中孔的生长，从而降低了聚合物中平均应力的最大值。 4）宏观应变比的增加导致颗粒的体积应变的增加，这促进了聚合物的塑性变形和宏观屈服的开始，而屈服应力的值较低。由于宏观应力的高三轴性，当应变比增加时，聚合物中的平均应力增加。 5）小颗粒的体积应变首先增加，并且在小颗粒附近标记了高应变率区域的形成及其传播。对于小应变率的情况，小颗粒有助于增加聚合物中的最大平均应力，而对于大应变率的情况，不管颗粒的尺寸如何，最大平均应力几乎保持不变。采用均质化法和有限元法的计算策略提供了均质化本构方程，考虑了宏观均匀变形的晶胞中所有微观变形行为，因此很容易在每个材料点引入由此获得的本构方程，以实现宏观不均匀在成型过程中观察到的变形。但是，在目前的研究中，通过在颗粒中引入小孔来模拟空化，因此，空洞的发生和生长受颗粒和周围聚合物的变形行为控制。为了阐明绝对尺寸对控制空化的影响，应该通过引入体积应变能以及表面能来考虑合适的长度尺度（Bucknall，1994）。颗粒的大小也可能影响异质颗粒的相互作用，这需要进一步研究。

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