柔性绳索结构因质量轻、高柔性和可设计性强等特点,在航空航天及机器人等工程领域得到广泛应用.由于几何大变形与材料非线性等因素影响,利用非线性有限元等高精度方法分析这类柔性结构的动力学特性时,存在模型复杂、计算量大和难以高效...柔性绳索结构因质量轻、高柔性和可设计性强等特点,在航空航天及机器人等工程领域得到广泛应用.由于几何大变形与材料非线性等因素影响,利用非线性有限元等高精度方法分析这类柔性结构的动力学特性时,存在模型复杂、计算量大和难以高效仿真等问题.文章改进了起源于计算机图形学的XPBD(extended position based dynamics)算法,设计了新的约束函数与迭代方法,使其适用于柔性绳索结构的动力学仿真.主要贡献包括:引入旋转向量以更准确描述结构姿态,基于Cosserat弹性杆理论设计了更精确的约束函数,采用约束能量作为迭代收敛判据以提高仿真精度,提出分组求解约束的方法提高迭代计算效率.还以索-杆复合结构为例验证了改进算法的有效性:与ADAMS软件相比,改进算法具有更好的稳定性,且计算效率大致相当;与原XPBD算法相比,改进算法显著提高了求解精度.改进算法引入了旋转向量,使约束函数的设计更灵活,计算框架也更利于并行化,具有在复杂柔性结构动力学仿真中进一步应用的优势和潜力.展开更多
This paper presents a micromechanics-based Cosserat continuum model for microstructured granular materials.By utilizing this model,the macroscopic constitutive parameters of granular materials with different microstru...This paper presents a micromechanics-based Cosserat continuum model for microstructured granular materials.By utilizing this model,the macroscopic constitutive parameters of granular materials with different microstructures are expressed as sums of microstructural information.The microstructures under consideration can be classified into three categories:a medium-dense microstructure,a dense microstructure consisting of one-sized particles,and a dense microstructure consisting of two-sized particles.Subsequently,the Cosserat elastoplastic model,along with its finite element formulation,is derived using the extended Drucker-Prager yield criteria.To investigate failure behaviors,numerical simulations of granular materials with different microstructures are conducted using the ABAQUS User Element(UEL)interface.It demonstrates the capacity of the proposed model to simulate the phenomena of strain-softening and strain localization.The study investigates the influence of microscopic parameters,including contact stiffness parameters and characteristic length,on the failure behaviors of granularmaterials withmicrostructures.Additionally,the study examines themesh independence of the presented model and establishes its relationship with the characteristic length.A comparison is made between finite element simulations and discrete element simulations for a medium-dense microstructure,revealing a good agreement in results during the elastic stage.Somemacroscopic parameters describing plasticity are shown to be partially related to microscopic factors such as confining pressure and size of the representative volume element.展开更多
文摘柔性绳索结构因质量轻、高柔性和可设计性强等特点,在航空航天及机器人等工程领域得到广泛应用.由于几何大变形与材料非线性等因素影响,利用非线性有限元等高精度方法分析这类柔性结构的动力学特性时,存在模型复杂、计算量大和难以高效仿真等问题.文章改进了起源于计算机图形学的XPBD(extended position based dynamics)算法,设计了新的约束函数与迭代方法,使其适用于柔性绳索结构的动力学仿真.主要贡献包括:引入旋转向量以更准确描述结构姿态,基于Cosserat弹性杆理论设计了更精确的约束函数,采用约束能量作为迭代收敛判据以提高仿真精度,提出分组求解约束的方法提高迭代计算效率.还以索-杆复合结构为例验证了改进算法的有效性:与ADAMS软件相比,改进算法具有更好的稳定性,且计算效率大致相当;与原XPBD算法相比,改进算法显著提高了求解精度.改进算法引入了旋转向量,使约束函数的设计更灵活,计算框架也更利于并行化,具有在复杂柔性结构动力学仿真中进一步应用的优势和潜力.
基金the National Natural Science Foundation of China through Contract/Grant Numbers 12002245,12172263 and 11772237Chongqing Jiaotong University through Contract/Grant Number F1220038.
文摘This paper presents a micromechanics-based Cosserat continuum model for microstructured granular materials.By utilizing this model,the macroscopic constitutive parameters of granular materials with different microstructures are expressed as sums of microstructural information.The microstructures under consideration can be classified into three categories:a medium-dense microstructure,a dense microstructure consisting of one-sized particles,and a dense microstructure consisting of two-sized particles.Subsequently,the Cosserat elastoplastic model,along with its finite element formulation,is derived using the extended Drucker-Prager yield criteria.To investigate failure behaviors,numerical simulations of granular materials with different microstructures are conducted using the ABAQUS User Element(UEL)interface.It demonstrates the capacity of the proposed model to simulate the phenomena of strain-softening and strain localization.The study investigates the influence of microscopic parameters,including contact stiffness parameters and characteristic length,on the failure behaviors of granularmaterials withmicrostructures.Additionally,the study examines themesh independence of the presented model and establishes its relationship with the characteristic length.A comparison is made between finite element simulations and discrete element simulations for a medium-dense microstructure,revealing a good agreement in results during the elastic stage.Somemacroscopic parameters describing plasticity are shown to be partially related to microscopic factors such as confining pressure and size of the representative volume element.
