Preface: machine-learning approaches for computational mechanics

<正>Machine-learning(ML) approaches have gained significant attention in recent years for their potential to revolutionize various scientific research fields, including computational mechanics,materials science, and biomedical engineering. In the field of computational mechanics, various neural network models such as feedforward neural networks, convolutional neural networks,     

概说并行计算结构力学

基于向量机（ｖｅｃｔｏｒｃｏｍｐｕｔｅｒｓ）和并行机（ｐａｒａｌｌｅｌｃｏｍｐｕｔｅｒｓ）两大类并行计算机，对线性静力和动力问题，非线性静力和动力问题，本文概说了相应于这两大类并行机一般的求解方法。     

On the developments of computational mechanics

Meccanica - The impact of computational methods in structural mechanics has been enormously increasing in the last two decades. A new discipline, now labelled as Computational Mechanics, has...     

《计算力学》CAI多媒体课件的实践

结合《计算力学》课程的特点，将多媒体ＣＡＩ技术运用到实际教学中，在教学中取得良好的效果．     

ODE conversion techniques and their applications in computational mechanics

In this paper, a number of ordinary differential equation (ODE) conversion techniques for transformation of nonstandard ODE boundary value problems into standard forms are summarised, together with their applications to a variety of boundary value problems in computational solid mechanics, such as eigenvalue problem, geometrical and material nonlinear problem, elastic contact problem and optimal design problems through some simple and representative examples. The advantage of such approach is that various ODE boundary value problems in computational mechanics can be solved effectively in a unified manner by invoking a standard ODE solver. The project is supported by National Natural Science Foundation of China.     

Approaches in computational welding mechanics applied to additive manufacturing: Review and outlook

The development of computational welding mechanics (CWM) began more than four decades ago. The approach focuses on the region outside the molten pool and is used to simulate the thermo-metallurgical-mechanical behaviour of welded components. It was applied to additive manufacturing (AM) processes when they were known as weld repair and metal deposition. The interest in the CWM approach applied to AM has increased considerably, and there are new challenges in this context regarding welding. The current state and need for developments from the perspective of the authors are summarised in this study.     

Experimental mechanics and nuclear power

The generation of power from nuclear reactors contributes significantly to our energy supplies, and will be even more important in the future. The continued safety of these systems is primarily dependent upon the integrity of the structural elements which form the pressure boundary and which position the fuel and control elements. Experimental mechanics has contributed significantly to the development of present concepts and is contributing to the development phase of advanced concepts. The need for continued contributions of experimental mechanics to the operational phase has not been well recognized. This lecture discusses the contributions of experimental mechanics to nuclear power.     

The theory of static decay in computational mechanics

In this paper,a new mathematical form,matrix,continued fraction(MCF)isintroduced to describe the decay of effects of an equilibrant system of forces acting on asphere of an elastic body.By this way,the famous Saint-Venant’s principle is proved oftenbut not always valid in computational mechanics.     

Experimental mechanics in Israel

Experimental mechanics in the modern sense started to come to Israel only in the late fifties of the present century. At present, there are two groups of active foci: the universities on the one hand, and the research and development groups of the defense establishment on the other hand. In contrast to the United States and most European countries, there is presently little interest and requirement for experimental mechanics within private industry and within the government agencies which do not deal with defense related activities. Because of natural and demographic reasons, the bulk of activity in the field is carried out in two geographical areas: Tel-Aviv and Haifa. There are also secondary foci in Jerusalem, Rehovoth and Beer-Sheba. For technical reasons and because of physical limitations, only some topics are mentioned and no effort is made to cover everything interesting in experimental mechanics which is going on in Israel today. In most areas, we meet with optical methods, strain-gage applications, or special pickups and instrumentation, particularly for dynamic measurements.     

Unconstrained and Cauchy-Born-constrained atomistic systems: deformational and configurational mechanics

In this contribution, the deformational and configurational mechanics of (elastic) discrete atomistic systems in relation to their continuum counterparts are considered for the quasi-static case. Thereby, we firstly investigate the basic unconstrained case in the sense of lattice statics as a reference. Based on these results, we consider two Cauchy-Born-type constraints that (locally) describe the change of the position of atoms (between the material and the spatial configuration) in terms of either a linear or a quadratic map, respectively. Insertion of these kinematic constraints into the variation of the total potential energy of the unconstrained case renders eventually Cauchy-Born-type definitions for atomistic stresses and hyperstresses, for both deformational and configurational cases. In the continuum limit, these are the relevant continuum stresses and hyperstresses contributing to the local force balances of first- (classical) and second-order (non-classical) gradient continua (here first- and second-order gradient refers to the highest gradient of the deformation map characterizing the kinematics). It is emphasized that the atomistic and the Cauchy-Born-type configurational quantities represent novel and unexpected contributions. Among other things, they may be useful in assessing the singular or non-singular character of deformation fields at crack tips and comparing numerical estimates resulting from atomistic simulations with analytical predictions resulting from solutions of related boundary value problems for gradient continua.     

A stable fast marching scheme for computational fluid mechanics

A stable fast marching scheme has been developed for the solution of coupled parabolic partial differential equations such as the Navier–Stokes equations. The scheme was developed with the aid of a stability analysis. The implementation of the method in standard alternating direction implicit algorithms is straightforward. The scheme was tested on the problem of natural convection in a square cavity. The number of iterations required for convergence was significantly reduced compared to conventional methods.     

第五届计算力学世界大会(WCCM-V)简介

1会议概况 WCCM-V(Fifth World Congress on ComputationalMechanics,第五届计算力学世界大会)于2002年7月7-12日在奥地利首都维也纳召开.由维也纳技术大学主办,并由该校校长H.A.Mang教授出任会议的组织委员会主席.这是国际计算力学界4年一度的盛会,也是该学术界最重要的会议.     

Multi-wedge points and multi-wedge elements in computational mechanics: evaluation of exponent and angular distribution

There is growing interest in accounting for the internal structure of a material. This interest stimulates developing tools for the accurate evaluation of fields near common vertices of structural elements, in particular, grains. This paper presents a robust method to numerically evaluate the exponent which characterizes the asymptotic behaviour of stresses and displacements at a vertex of an arbitrary number of elastic wedges. The efficiency is achieved by

• (i)reduction of the problem to three-point matrix difference equations with appropriately normalized coefficients, and
• (ii)finding the roots of the determinant of the matrix by specially designed iterative and search procedures. This allows us to ensure convergence and not miss closely located significant roots.

Numerical calculations for systems of two and three wedges, studied by other authors previously, show that the results agree to at least five digits. A number of new examples for three and four wedges with and without cracks reveal that the multi-wedge systems, which have more than one root generating singular stresses, are not rare; quite commonly such roots are closely located. We emphasize that this fact has important implications for the development of singular multi-wedge elements, intended to increase the accuracy of the BEM and FEM.The appendices serve to re-examine and clarify the relation between properties of the matrix of the system, the asymptotic behaviour of stresses and displacements, and the number of stress intensity factors. It is shown that the necessary condition, established by Dempsey and Sinclair for the logarithmic multiplier to be present in the asymptotic formulae, is also sufficient.     

Theoretical, experimental and computational mechanics of fracture in constrained interlayers

The constraint of a thin silver interlayer is used to create high triaxial stresses to evaluate the applicability of theoretical models for ductile fracture. Rice and Tracey's model for cavity expansion under high triaxial states of stress and Huanget al.'s model for cavity instability were considered. The experimentally determined _m / _y values suggest that further investigation of the Huanget al. theory is warranted. Microstructural analysis revealed that multiple cavities were initially present in the silver interlayers, and the number and size of the cavities increased as failure was approached. Finite element analysis and experimental results showed excellent agreement in a computational determination of cavity instability. Thus, it appears that ductile fracture in constrained thin interlayers can be explained with unstable cavity growth.     

Mathematical and computational modeling of political systems

Nonlinear Dynamics - The aeroelastic behaviors of wing–pylon–store system have been researched for several decades. However, the effects of pylon–store system on the nonlinear...