Sergey Korobeynikov – författare

This book provides readers with a deep understanding of the use of objective algorithms for integration of constitutive relations (CRs) for Hooke-like hypoelasticity based on the use of corotational stress rates. The purpose of objective algorithms is to perform the step-by-step integration of CRs using fairly large time steps that provide high accuracy of this integration in combination with the exact reproduction of superimposed rigid body motions. Since Hooke-like hypoelasticity is included as a component in CRs for elastic-inelastic materials (e.g., in CRs for elastic-plastic materials), the scope of these algorithms is not limited to hypoelastic materials, but extends to many other materials subjected to large deformations. The authors performed a comparative analysis of the performance of most currently available objective algorithms, provided some recommendations for improving the existing formulations of these algorithms, and presented new formulations of the so-called absolutely objective algorithms. The proposed book will be useful for beginner researchers in the development of economical methods for integrating elastic-inelastic CRs, as well as for experienced researchers, by providing a compact overview of existing objective algorithms and new formulations of these algorithms. The book will also be useful for developers of computer codes for implementing objective algorithms in FE systems. In addition, this book will also be useful for users of commercial FE codes, since often these codes are so-called black boxes and this book shows how to test accuracy of the algorithms of these codes for integrating elastic-inelastic CRs in modeling large rotations superimposed on the uniform deformation of any sample.

This book provides readers with a deep understanding of the principles for generating formulations of compressible isotropic hyperelastic material models based on formulations of incompressible material models. The reference high-performance incompressible isotropic hyperelastic material model is Ogden's model, for which the elastic energy is generally represented as the sum of elemental energies based on strain tensors from the Doyle–Ericksen family. For the sake of transparency, the study is confined to considering the elastic energy only for one term of this sum based on the Finger strain tensor corresponding to the well-known neo-Hookean material model. The book presents a systematic study of the performance of two known types of compressible generalization of the incompressible neo-Hookean material model. The first type of generalization is based on the development of volumetric-isochoric neo-Hookean models and involves the additive decomposition of the elastic energy into volumetric and isochoric parts. The second, simpler type of generalization, is based on the development of mixed neo-Hookean models that do not use this decomposition. Theoretical studies of model performance and simulations of some homogeneous deformations have shown that when using “good” volumetric functions, mixed and volumetric-isochoric models show similar performance in applications and have physically reasonable responses in extreme states, which is convenient for theoretical studies. However, compared to volumetric-isochoric models, mixed models allow the use of a wider set of volumetric functions with physically reasonable responses in extreme states. Another feature of mixed models is that they allow for simpler expressions for stresses and tangent stiffness tensors. This book is useful both for novice researchers in developing hyperelastic equations for compressible materials and for experienced researchers by providing a brief overview of methods for generating compressible hyperelastic formulations based on available incompressible hyperelastic formulations.