16MnR钢缺口试样解理断裂行为研究

研究了低合金热轧钢16MnR缺口试样在$-196\,{^\circ}$C和$-130\,{^\circ}$C的解理断裂机 理. 拉伸试验、单、双缺口四点弯曲实验、断口形貌观察以及有限元分析结果表明, 缺口试 样发生解理断裂时均起裂于夹杂物粒子, 一种位于缺口根部前端(IC型), 另一种位于距缺口 根部较远的条形裂纹前端(SIC型); 且随温度升高, 起裂源的类型从$-196\,{^\circ}$C下的IC 型转变为$-130\,{^\circ}$C下的SIC型. 微裂纹均形核于夹杂物, 最终的断裂由铁素体晶粒尺 寸的微裂纹扩展控制. 缺口试样IC型解理断裂遵循裂纹形核条 件$\varepsilon_{\rm p} \ge \varepsilon_{\rm pc}$和裂纹扩展条件$\sigma_{yy} \ge \sigma_{f}$, 而SIC型解理断裂条件则演化为$\varepsilon_{\rm p}+\varepsilon_{\rm ps} \ge \varepsilon_{\rm pc}$和$\sigma_{yy} +\sigma_{yy{\rm s}} \ge \sigma_{f}$.     

A system of generalized variational inclusions involving generalized H(·, ·)-accretive mapping in real q-uniformly smooth Banach spaces

In this paper, we consider a class of accretive mappings called generalized H(·, ·)-accretive mappings in Banach spaces. We prove that the proximal-point mapping of the generalized H(·, ·)-accretive mapping is single-valued and Lipschitz continuous. Further, we consider a system of generalized variational inclusions involving generalized H(·, ·)-accretive mappings in real q-uniformly smooth Banach spaces. Using proximal-point mapping method, we prove the existence and uniqueness of solution and suggest an iterative algorithm for the system of generalized variational inclusions. Furthermore, we discuss the convergence criteria of the iterative algorithm under some suitable conditions. Our results can be viewed as a refinement and improvement of some known results in the literature.     

Comparison results for initial value problems of second-order impulsive integro-differential inclusions

In this paper, we present new maximum and minimum principles for the initial value problem for a class of second-order nonlinear impulsive integro-differential inclusions with discontinuous multivalued functions on the right hand side in a real Banach space. This allows us to lead on to the development of the comparison principle and monotone iterative technique for a nonlinear second-order impulsive integro-differential inclusion.     

Generic properties of multifunctions: Application to differential inclusions

We prove that almost all in Baire sense Caratheodory multifunctions in finite dimensional space are Kamke continuous. Further the main properties of differential inclusions with Kamke and one sided Kamke right-hand sides are studied.As a corollary we prove that for almost all optimal control problems, the relaxation and relaxation stability properties hold.     

Homogeneous feedback design of differential inclusions based on control Lyapunov functions

This paper is concerned with the stabilization of differential inclusions. By using control Lyapunov functions, a design method of homogeneous controllers for differential equation systems is first addressed. Then, the design method is developed to two classes of differential inclusions without uncertainties: homogeneous differential inclusions and nonhomogeneous ones. By means of homogeneous domination theory, a homogeneous controller for differential inclusions with uncertainties is constructed. Comparing to the existing results in the literature, an improved formula of homogeneous controllers is proposed, and the difficulty of the controller design for uncertain differential inclusions is reduced. Finally, two simulation examples are given to verify the preset design.     

On Stepanov almost-periodic oscillations and their discretizations

The relationship between Carathéodory almost-periodic (a.p.) solutions and their discretizations is clarified for differential equations and inclusions in Banach spaces. Our investigation was stimulated by an old result of Meisters [Proc. Am. Math. Soc. 10 (1959), pp. 113–119] about Bohr a.p. solutions which we generalize in several directions. Unlike for functions, Stepanov and Bohr a.p. sequences are shown to coincide. A particular attention is paid to purely (i.e. non-uniformly continuous) Stepanov a.p. solutions. Many ideas are explained in detail by means of examples illustrated.     

激光拉曼光谱测定流体包裹体成分研究进展

成矿流体研究是矿床学研究中的前沿地带,单个流体包裹体的成分分析更是其中的热点和难点,本文对现有的各种测试技术的优缺点进行了总结,揭示了各自的局限性。通过对与流体包裹体成分分析相关的激光拉曼分析技术的探索过程进行回顾和总结,试图对低温和常温下激光拉曼对流体包裹体成分分析的研究工作的方向进行展望：低温：(1)流体包裹体中常见水盐多元复杂体系的研究工作;(2)对天然流体包裹体成分进行定性、定量尝试;(3)目前常用的显微热台测包裹体盐度将第一次熔融温度作为低共熔温度的方法存在误差,应该做进一步研究;(4)低温下氯盐水合物的结构尚无定论。常温：(1)Fe3+,Zn2+,Cu2+等离子作为主要成矿金属离子在水溶液中与Cl-和H₂O是如何结合的;(2)NaCl,CaCl₂,MgCl₂,CuCl₂,ZnCl₂,FeCl₃含量高低造成水溶液拉曼光谱O—H伸缩振动区域(2 800～3 800 cm-1)的谱峰偏移的原因。     

Current understanding of ultra-high cycle fatigue

The fatigue life of numerous aerospace, locomotive, automotive and biomedical structures may go beyond 10⁸ cycles. Determination of long life fatigue behavior becomes extremely important for better understanding and design of the components and structures. Initially, before the invention of ultrasonic fatigue testing, most of the engineering materials were supposed to exhibit fatigue life up to 10⁷ cycles or less. This paper reviews current understanding of some fundamental aspects on the development of accelerated fatigue testing method and its application in ultra-high cycle fatigue, crack initiation and growth mechanisms of internal fracture, S-N diagram, fatigue limit and life prediction, etc.     

柔性电子封装结构中夹杂对延展性的影响分析

以岛-桥型柔性电子封装结构为研究对象,从封装材料中夹杂的刚度、位置、封装方式三个方面探讨了夹杂对柔性电子结构延展性的影响。有限元分析结果表明:随着夹杂刚度的增大,桥的最大主应变增大,整体结构最大延伸量可减小30%;夹杂埋藏位置越深,桥顶局部的整体应变水平越大,最大延伸量可减小20%;相对"硬"封装情形,相同的夹杂对"软"封装中桥的最大延伸量的影响更严重。本文所得结论对于柔性电子器件结构的设计和材料选用具有参考和指导意义。