A comparative study of rheology MSD models whose structures are lattice and truss
A comparative study of rheology MSD models whose structures are lattice and truss
复制标题
DOI：
10.1109/iros.2004.1390008
复制
发表时间：
2004-09
期刊：
影响因子：
--
通讯作者：
R. Nogami;H. Noborio;S. Tomokuni;S. Hirai
中科院分区：
文献类型：
--
作者：
R. Nogami;H. Noborio;S. Tomokuni;S. Hirai
在本文中，我们比较了 MSD（质量-弹簧-阻尼器）粒子模型的两种主要结构。一种是晶格（六面体）结构，另一种是桁架（四面体）结构。它们（特别是桁架结构）经常用于表示弹性和/或粘弹性物体。 MSD模型有效地计算了上述材料的形状变形。此外，为了保持每次变形的形状精度，我们在捕获真实流变对象的许多表面点下仔细校准了基本MSD单元中Voigt部分的阻尼器和弹簧系数以及其他部分的阻尼器系数。遗传算法用于概率校准。经过比较，我们得到以下性质：（1）晶格结构用于计算力传播的单元太多。因此，它借助局部（前馈）体积常数条件精确地引导形状变形。 (2)桁架结构没有足够的单元来传播内力，因此，为了通过扩展其虚拟流变对象来保持合理的体积，我们需要全局（反馈）体积恒定条件。 (3)全局条件虽然耗时，但可以直接控制虚拟流变对象的总体积。另一方面，本地的速度很快，但直接仅扩展虚拟对象的一部分（体素）。因此，具有局部条件的点阵结构的体积和形状优于包括全局条件的桁架结构。 (4) 点阵结构中的MSD单元数量大约是桁架结构中的两倍。因此，前一种计算大约比后一种计算慢两倍。与此相反，全局体积恒定条件严格地比局部体积慢两倍或慢。因此，具有局部条件的点阵结构的计算时间比具有全局条件的桁架结构的计算时间要短。综上所述，考虑到计算成本和形状精度，局部体积恒定条件的点阵结构是最好的。
In this paper, we compare two major structures of MSD (mass-spring-damper) particle models. One is the lattice (hexahedral) structure, and the other is the truss (tetrahedral) structure. They (especially, the truss structure) have been frequently used for representing elastic and/or visco-elastic object. The MSD model efficiently calculates shape deformation of the above materials. In addition, in order to maintain shape precision of each deformation, we carefully calibrate coefficients of damper and spring of Voigt part and a coefficient of damper of the other part in the basic MSD element under many surface points capturing a real rheologic object. A genetic algorithm is used for probabilistic calibration. After the comparison, we get the following properties: (1) the lattice structure has too many elements for calculating force propagation. Therefore, it precisely leads shape deformation with the help of the local (feedforward) volume constant condition. (2) The truss structure does not have enough elements for propagating internal forces, therefore, in order to keep a reasonable volume by expanding its virtual rheology object, we need the global (feedback) volume constant condition. (3) The global condition is time consuming, but can directly control the total volume of virtual rheology object. On the other hand, the local one is quick, but directly expands only a part (voxel) of the virtual object. Therefore, the volume and shape in the lattice structure with the local condition are better than those in the truss structure including the global one. (4) The number of MSD elements in the lattice structure is about two times larger than that in the truss one. Therefore, the former calculation is about two times slower than the latter one. As contrasted with this, the global volume constant condition is strictly two times or slower than the local one. As a result, calculation time of the lattice structure with the local condition is smaller than that of the truss structure with the global one. In conclusion, the lattice structure with the local volume constant condition is the best concerning to calculation cost and shape precision.