基于有限元模拟的超声应力系数标定及分析*

应力系数的标定作为超声应力检测最为关键的环节,直接决定应力检测结果的准确性。传统的应力系数试验标定对于被测物的表面粗糙度、耦合剂厚度、声匹配块与被测物接触力等因素十分敏感,但缺少基本参照值。基于COMSOL建立多物理场耦合的超声应力检测模型,施加不同的拉伸载荷,计算临界折射纵波到达时间与不同应力值之间的关系,模拟标定45#钢的超声应力系数为13.7MPa/ns。单轴水平拉伸试验标定的45#钢应力系数为16.5MPa/ns。结果表明,通过两种方法标定的应力系数较为接近,试验标定的应力系数偏大,这是由于有限元方法能够消除试验过程中各种不确定因素对声时精确测量所造成的影响,能够更加纯粹的反映材料的声弹性效应,因此具有作为基础数据的参考价值。有限元方法作为传统试验方法的补充,可以减小试验标定数据的离散性,提高超声应力检测结果的可信度。     

STABILITY OF DISPLACEMENT TO THE SECOND FUNDAMENTAL PROBLEM IN PLANE ELASTICITY

In this article, by using the stability of Cauchy type integral when the smooth perturbation for integral curve and the Sobolev type perturbation for kernel density happen, we discuss the stability of the second fundamental problem in plane elasticity when the smooth perturbation for the boundary of the elastic domain （unit disk） and the Sobolev type perturbation for the displacement happen. And the error estimate of the displacement between the second fundamental problem and its perturbed problem is obtained.     

Stability of Displacement to the Second Fundamental Problem in Plane Elasticity

In this article, by using the stability of Cauchy type integral when the smooth perturbation for integral curve and the Sobolev type perturbation for kernel density happen, we discuss the stability of the second fundamental problem in plane elasticity when the smooth perturbation for the boundary of the elastic domain (unit disk) and the Sobolev type perturbation for the displacement happen. And the error estimate of the displacement between the second fundamental problem and its perturbed problem is obtained.     

独立学院数学课程体系的探索

为解决独立学院数学教学中能力强的学生"吃不饱",能力欠佳的学生"吃不消"的问题,提出了"基础+提高"统筹优化的数学课程体系."基础"模块的教学坚持为后续专业课服务,并穿插教书中"育人"理念;"提高"模块作为公共选修范畴,具有自主性、多元化特点,并突出人才培养的阶梯式发展.通过近5年的教学改革与实践,新课程体系有效地提高了学生学习数学的兴趣,降低了期末考试的不通过率,并造就一批有创新意识的人才.     

Novel procedure for complete in-plane composite characterization using a single T-shaped specimen

This paper deals with the direct identification of the in-plane elastic properties of orthotropic composite plates from heterogeneous strain fields. The shape of the tested specimen is that of a T subjected to a complex stress state. As a result, the entire set of unknown parameters is directly involved in the strain and displacement responses of the sample. No exact analytical solution is available for such a geometry, and a specific strategy is used to identify the different stiffness components from the whole-field displacements measured over the tested specimen with a suitable optical method. The paper focuses mainly on the experimental aspects of the procedure, and an example of mechanical characterization of a fabric-reinforced composite plate is given.     

Stability of the second fundamental problem under perturbation of the boundary curve in plane elasticity

Let the elastic domain be a disk, and its boundary the unit circle. By dint of the stability of Cauchy‐type integral with respect to the perturbation of integral curve, this paper discusses the stability of the complex stress functions to the second fundamental problem in plane elasticity when smooth perturbation happens for the boundary curve. Copyright © 2010 John Wiley & Sons, Ltd.     

二元超晶格弹性应力的能带理论计算

根据量子能带理论 ,采用经验赝势方法 ,对 (Pb) n/ (Bi) n,(Al) n/ (As) n 的假想简立方二元超晶格结构的弹性应力进行了计算 .结果表明弹性应力随超晶格周期λ的增加而迅速升高至一定大小后趋于稳定 ,且只有在周期较小时才同过渡金属氮化物超晶格硬度随周期的变化的趋势定性一致 ,为超晶格硬度随周期的变化提供了一种可能的解释     

Inequality constraints with elastic impacts in deformable bodies. The convex case

Summary The aim of the present paper is to present some new results for problems when impacts occur. We prove, in the framework of linear elastic body, certain equivalent form of the d'Alembert's principle, including velocity discontinuity. We show that the theorem of stationary action still holds as an inequality. The consideration of the variation of the unknown impact time implies for the impact problem certain new variational expressions in inequality form. Received 13 August 1998; accepted for publication 6 May 1999