中厚板热矫直工艺规程制定及优化策略

采用高效的优化方法对中厚板热矫直工艺规程展开研究,以最小矫直力为目标函数,以辊系压下量为设计变量,分别以矫直质量和曲率积分公式作为不等式和等式约束建立工艺规程优化模型并展开优化求解.优化计算结果与某钢厂的在线数据有较好的一致性,以此为基础研究某一具体品种的矫直力、曲率和矫直轨迹等规律,研究结果表明:3～7号辊的矫直力逼近单辊最大矫直力,且在3-7辊下轧件断面塑性百分比接近80%;轧件出口的平直度满足工程要求,横向残余应力能够控制在15MPa以内.     

九辊中厚板热矫直机故障分析及解决方案

根据河北钢铁集团舞钢公司九辊中厚板热矫直机应用现状,重点分析了我厂热矫机经常出现的故障,最后经过对故障了分析,改进设备不完善方面,很好的解决了问题。     

校直对厢形梁焊接残余应力的影响

介绍不同焊接工艺对厢桥梁焊接余应力的影响及校直前后的其残余应力的变化。     

焊接过程对焊接残余应力及残余变形的影响

采用热弹塑性有限元法，对直通焊和多人同时分段焊两种焊接过程的平板对接焊时焊接应力变形和圆柱壳板环缝的焊接变形进行比较，认为多人同时分段焊直通焊无论在降低焊接残余应力还是焊接残余变形都具有非常显著的效果。     

残余应力对金属疲劳强度的影响

残余应力对光滑试样高周疲劳极限的影响可以用Goodman关系来描述，但必须要得到残余应力作用系数m、合理地提取残余应力的表征值和区分开其它因素的影响。残余应力对缺口疲劳极限的作用大于对光滑试样的作用，是由于残余应力也存在应力集中现象，而且不易衰减。残余应力的应力集中系数不仅与缺口几何因素有关，还与材料特性有关。试验研究还表明，表层残余压应力对于承受轴向载荷且疲劳残纹萌生于表面的零件也十分有益。     

机械应力消除法对焊接残余应力的影响

焊后残留在结构中的焊接应力是影响整个结构寿命的关键,因此,控制和消除焊接应力成了焊接领域的热点议题。本文介绍了机械应力消除法对焊接残余应力的影响,通过两者之间的联系,总结提出有效控制残余应力的指导方法,以详实机械原理消除法与焊接残余应力的联动影响,进一步为焊接领域提供新的总结性方法论     

残余应力对储罐泄漏的影响

本文应用Ｘ射线法对不储槽及输送管道的残余应力进行了检测与分析。对焊缝、热影响区、母材等典型部位进行了重点测试，对热处理的效果进行了检测与评价，找出了储槽泄漏的原因。     

焊接工艺参数对Q345钢平板焊接残余应力的影响

为研究焊接工艺参数对Q345钢平板焊接残余应力的影响,对采用药芯焊丝半自动焊接后的8 mm厚平板焊缝结构进行仿真模拟,在经验数值范围内设置不同的焊接工艺参数值,分析平板在横向和厚度方向的焊接残余应力分布情况。研究结果表明:横向的最大焊接残余应力分布在热影响区,且随着焊接速度的增大和焊接层间温度的降低而降低;沿厚度方向的最大焊接残余应力为115.92 MPa,位于平板中间层,随着焊接速度的增大而先减小后增大;平板焊接在横向的残余应力远大于厚度方向的应力。根据焊接残余应力的变化情况,运用二元回归分析法对横向和厚度方向的最大焊接残余应力进行函数拟合与检验,并开展多因素拟合模型的分析,得到焊接速度和焊接层间温度对焊接残余应力的综合影响规律。通过研究残余应力的变化趋势可选定焊接残余应力最小时的工艺参数范围,实现焊接工艺参数优化。     

含焊接残余应力薄圆板结构自由振动近似解

研究焊接残余应力对薄圆板结构振动特性的影响,解决薄圆板结构振动中存在非均匀分布预应力问题.根据含预应力结构的应变-应力方程,建立含预应力薄圆板结构的运动控制方程.基于Rayleigh-Ritz法构造Lagrange能量泛函方程.将预应力和位移试函数展开成三角级数形式,对含预应力薄圆板结构的自由振动问题进行求解.以周边简...     

熔体温度对注射成型热塑性聚氨酯制件残余应力及外形精度的影响EI北大核心CSCD

采用光学双折射法研究注射成型过程中熔体温度对透明热塑性聚氨酯(TPU)弹性体平板制件残余应力的影响规律和作用机理。结果表明,TPU制件在近浇口区域的残余应力大于远浇口区域,整体残余应力随熔体温度上升而下降。通过对平行于熔体流动方向和垂直于熔体流动方向上的制件截面进行双折射测量发现,注射成型TPU制件具有明显的皮-芯结构和零应力层,且随熔体温度升高芯层厚度显著增加。残余应力分析结果表明在制件的芯层以流动残余应力为主,而皮层区域是流动残余应力和热残余应力叠加的结果。此外,制件的翘曲变形与残余应力的分布直接相关,TPU制件尺寸的改变主要是由于流动残余应力释放引起的。     

残余应力和粗糙度对叶片振动疲劳性能的影响

为了研究叶片表面完整性对其振动疲劳性能的影响,本文模拟分析了某型高温合金叶片在振动疲劳实验过程中的动力学应力响应,获得叶片共振时应力幅值随时间的变化规律,分析了残余应力和粗糙度对叶片振动疲劳寿命和疲劳极限的影响规律.结果表明:叶片共振过程中的应力响应幅值先增大后减小呈周期性变化,属于"拍"现象,满足关系σ=1 046sin(242.83t)sin(5 828t);叶片的振动疲劳极限和疲劳寿命均随残余应力和粗糙度的增大而减小,振动疲劳极限和残余应力之间的关系满足σfat=510.9-0.31-70.93σrest;而疲劳极限和粗糙度之间的关系则满足σfat=9.67R2roughness-70.93Rroughness+713.23.     

Effects of residual stress and shape of web plate on the fatigue life of railway wheels

Railway wheels have been one of the most critical components in a railway vehicle. Fatigue design of railway wheel is one of the most important factors. Damages on the wheel can be divided into three types, such as the contact fatigue of the tread, the thermal fatigue of the rim due to braking and the mechanical fatigue of the web plate. The railway wheel has the initial residual stress formed during the manufacturing process, and this residual stress changes due to the thermal stress induced by braking. In this study, we evaluated residual stress of web plate by heat treatment due to the manufacturing process and changes of residual stress by braking using finite element analysis. The cyclic stress history for fatigue analysis is determined by applying finite element method. The fatigue strength evaluations of the web plate are performed to investigate the effect of the residual stress.     

Superconvergent Patch Recovery for plate problems using statically admissible stress resultant fields

In this paper, we study an approach for recovery of an improved stress resultant field for plate bending problems, which then is used for a posteriori error estimation of the finite element solution. The new recovery procedure can be classified as Superconvergent Patch Recovery (SPR) enhanced with approximate satisfaction of interior equilibrium and natural boundary conditions. The interior equilibrium is satisfied a priori over each nodal patch by selecting polynomial basis functions that fulfil the point‐wise equilibrium equations. The natural boundary conditions are accounted for in a discrete least‐squares manner. The performance of the developed recovery procedure is illustrated by analysing two plate bending problems with known analytical solutions. Compared to the original SPR‐method, which usually underestimates the true error, the present approach gives a more conservative error estimate. Copyright © 1999 John Wiley & Sons, Ltd.     

Hybrid-Trefftz stress elements for plate bending

The hybrid-Trefftz stress element is used to emulate conventional finite elements for analysis of Kirchhoff and Mindlin-Reissner plate bending problems. The element is hybrid because it is based on the independent approximation of the stress-resultant and boundary displacement fields. The Trefftz variant is consequent on the use of the formal solutions of the governing Lagrange equation to approximate the stress-resultant field. In order to emulate conventional elements, nodal functions are used to approximate the displacements on the boundary of the element. Duality is used to set up the element solving system. The associated variational statements and conditions for existence and uniqueness of solutions are recovered. Triangular and quadrilateral elements are tested and characterized in terms of convergence, sensitivity to shear-locking, and shape distortion. Their relative performance is assessed using assumed strain Mixed Interpolation of Tensorial Components (MITC) elements and recently proposed Trefftz-based elements. This relative assessment is extended to a hypersingular problem to illustrate the effect of enriching the domain and boundary approximation bases.     

强化处理对GCr15钢球残余应力和微观组织的影响

实验研究了强化处理后钢球残余应力和微观组织的改变.本文研究了经强化处理后,钢球沿径向表面残余应力大小、残余奥氏体含量及硬度分布;用光学显微镜、扫描电子显微镜对经表面形变强化后的轴承钢球进行显微组织及裂纹观察.研究表明:轴承钢球次表层残余应力为压应力,随电解抛光深度的增加,逐渐会出现一个最大压应力的峰值,而后压应力值逐渐减小.强化处理过程中会发生应力诱发残余奥氏体转变为马氏体,但对压应力分布影响不大.将静态Herzt接触理论应用于钢球的动态碰撞强化中,分析探讨钢球裂纹的形成,与实验结果相一致,具有重要指导意义.     

An experimental study on residual stress relaxation in low-cycle fatigue of Inconel 718Plus

Residual stress relaxation induced by the application of mechanical loads is determined by the nature of residual stress, the elasto-plastic material properties, and the type of applied load. Despite the importance of the first load cycle, analytical models available in the literature generally assumed residual stress relaxation as a continuous process. Residual stress induced by machining on Inconel 718Plus superalloy cylindrical specimens was measured before and after the application of load cycles under strain control. Low-cycle fatigue tests were carried out at room temperature for different strain amplitudes, and X-ray diffraction measurements were performed before and after 10 and 100 cycles. A comprehensive analytical model was derived to describe the relaxation process associated with the initial cycles and that associated with the continuous application of load cycle, which is based on the plastic strain energy per cycle W and requires the evaluation of parameters that are only dependent on the material and not on the strain amplitude.     

The coupling effect of punch shape and residual stress on measuring adhesion work of membrane by pull-off test

The adhesion work of thin film, such as membrane, can be measured by pull-off test. In this kind of experiments, the residual stress in film due to pretension during sample preparation plays an important role in experimental results. Moreover, the effect of residual stress on results varies greatly depending on different punch shapes. The coupling effect of punch shape and residual stress is studied in the framework of plate theory and energy principle. The analytical expressions for the effect parameters are obtained on the basis of the energy criterion. From our study, it is found that the effect of residual stress is more significant for a circular punch than the one for a rectangular punch. For future pull-off experiments, the coupling effect should be taken into account and the rectangular punch instead of a circular punch should be prioritized in experiments to mitigate the effect of residual stress.