喷丸处理对蒸汽发生器传热管材料抗应力腐蚀性能的影响

喷丸处理造成的表面压应力和强化层组织能够显著提高18-8型奥氏体不锈钢和 Incoloy 800 合金在氯化镁溶液中的抗应力腐蚀能力。但在260℃、含500—1000ppmCl-水中,或再添加1%H_2O_2的氧化性介质中,只有当喷丸强化层的完整性没有被破坏,表面仍保持压应力时,才能改善抗 Cl-应力腐蚀能力;当喷丸表面遭受大的变形,强化层的完整性受到拉应变和腐蚀破坏时,喷丸处理就不再显示积极作用。     

复合材料结构开孔分析第二部分：壳类开孔问题

本文对复合材料壳的一般方程组，考虑对称铺层情况，通过微分算子运算、仿真变换，化为4个独立的偏微分方程，从而得到标准的变态Bessel方程，求出其解析解。采用类似本文第一部分的保角映射方法，对开有方形孔和任意孔角半径壳，导得对孔边自由和刚性补强的两类问题的求解方程组。本文的理论分析结果与实验结果吻合良好。     

CONSIDERATIONS OF THE EFFECT OF RESIDUAL STRESSES ON FATIGUE OF WELDED ALUMINIUM ALLOY STRUCTURES

A new class of large, high-speed seagoing ferry-boat is under development for service around the world. The ships, which are built entirely of aluminium-alloy plate and stiffeners, show a propensity for fatigue cracking of the welded structure. Cracks may occur in both the hulls and the superstructure early in their 20-year service life. Early appearance of fatigue cracks is shown to result from the combined stress and strain fields set up in weld zones by the static residual stresses and cyclic loads, beyond the effects of weld and detail geometry.  A numerical example demonstrates that conventional methods of fatigue analysis overestimate the lifetime of the welded aluminium structure, while damage tolerance analysis based on fracture mechanics leads to improved prediction.     

Failure criteria for linear elastic materials with U-notches

This paper provides a simple, albeit accurate, criterion for prediction of the rupture loads of brittle, or quasi-brittle, U-notched samples, where linear elastic fracture mechanics is not applicable because blunted notches do not exhibit stress singularities. Good agreement is found between numerical predictions and experimental results. The results of fracture tests from 18 different ceramic materials and a polymer (at − 60°C) are summarized and are used as a reference for checking the fracture criterion. Seven fracture criteria are reviewed and it is shown that all can be recast into the proposed criterion.     

Stress intensity factor computation using the method of fundamental solutions

In this paper, we study the application of the method of fundamental solutions to the computation of stress intensity factors in linear elastic fracture mechanics. The displacements are approximated by linear combinations of the fundamental solutions of the Cauchy–Navier equations of elasticity and the leading terms for the displacement near the crack tip. The applicability of two formulations of the method is demonstrated on two mode I crack problems, where it is shown that accurate approximations for the stress intensity factors can be obtained with relatively few degrees of freedom. Parts of this work were undertaken while the first author was a Visiting Professor in the Department of Mathematical and Computer Sciences, Colorado School of Mines, Golden, Colorado 80401, U.S.A.     

Effect of Vacuum Impregnation-Dehydration on the Mechanical Properties of Apples

The effect of sucrose solution concentration and vacuum/atmospheric pressure periods on the mechanical properties of apples (Gala var.) was studied through a stress relaxation test. The empiric model proposed by Peleg was used to fit the curves and the parameters a (level of relaxation) and b (relaxation rate) were evaluated. The experimental results obtained in this study showed that vacuum impregnation conditions had a great influence on the final mechanical properties of the apples. The Peleg model fitted well the data from the stress relaxation curves and may be useful for assessing sample deformation resulting from the vacuum impregnation process.     

逐步回归分析计算程序

逐步回归法是多元线性回归分析中的一种常用方法。它的最大特点是能逐个地引进与某一工程指标关系最密切的因子。故它可以帮助人们在较广泛的函数类中,自动选出一种较好的表达式,从而大大节省了人的劳动。因此,在生产、科研与设计中得到了广泛应用。本文简单介绍了逐步回归分析计算的基本公式,程序结构以及程序的运行操作等,并用实例阐明了程序的操作步骤。     

影响铸铁热疲劳抗力的因素

在热交变应力的作用下，热疲劳是铸铁工件的主要失效形式之一。本文综述了影响铸铁热疲劳抗力的诸因素。     

开小圆孔圆柱壳在内压力作用下的应力集中

用一组简化的扁壳方程,分析了受内压作用下的圆柱壳在小圆孔边上的应力集中问题。类似于用薄扁壳方程分析柱壳圆孔附近应力集中的方法,求出了考虑横向剪切效应的应力集中系数的近似解析解及数值结果,由此得出了横向剪切效应对应力集中影响的一个新的特性。     

生长温度对CVD金刚石薄膜的影响

系统研究了ＣＶＤ金刚石薄膜成膜过程中生长温度对薄膜质量、生长率和力学性能的影响。研究结果表明：在典型沉积条件下，生长温度愈高、薄膜的晶体质量愈好；但薄膜的应力状况和附着性能变坏；在８００℃时，金刚石薄膜的生长速率最大。讨论了ＣＶＤ金刚石薄膜作为机械工具涂层的最佳生长温度。