不锈钢切削残余应力实验研究

已加工表面残余应力是衡量零件加工表面质量的一个重要指标。针对目前缺乏对不锈钢切削残余应力研究的现状,通过实验研究切削冷却条件和切削参数对不锈钢加工残余应力的影响,并应用热力耦合理论进行分析。实验结果表明,不锈钢因切削产生的加工残余应力表现为拉应力,切削冷却条件和切削参数均对残余应力大小有影响,作用效果与切削液的冷却能力、渗透力及高温工作能力有关。     

焊接残余应力引起铣削加工变形的研究

焊接过程会产生残余应力,铣削加工后焊接残余应力释放和重新分布对铣削变形产生很大影响.为了研究残余应力释放和重新分布规律,采用有限元方法以最小焊接残余应力作为初始应力对铣削加工进行了数值模拟,获得了焊接试验件铣削加工残余应力和变形,并对焊接残余应力释放和重新分布以及加工变形进行了分析.     

切削加工表面残余应力的有限元计算

介绍了热-力耦合有限元理论对加工表面残余应力进行的预测和计算,并借助于有限元软件对切削过程进行仿真,得到了加工表面残余应力的分布规律。     

电解研磨复合加工对表面残余应力的影响

本文就电解研磨复合加工对表面残余应力的影响在理论分析的基础上通过试验进行了验证。     

高速铣削加工铝合金表面残余应力研究

基于Doelle—Hauk方法测量了铣削加工铝合金工件表面的残余应力状态,结果表明,应力主平面与试样表面基本平行,说明铣削加工铝合金表面的残余应力近似处于二维平面应力状态。在分析了织构对残余应力测试影响的基础上,采用X射线衍射法中的回摆法测量了铣削加工工件表面不同切削几何位置、不同转速下残余应力的分布规律。为了对残余应力的分布作出解释,采用Kisterler测试仪测试了不同主轴转速下切削力的变化规律;建立了双刃斜角切削有限元模型,得到了单个切屑形成时已加工工件表面的切削温度场。最后,从热力耦合的角度对残余应力的形成机理进行了研究。     

残余应力对切削加工精度的影响及消除

探讨了机械制造过程中残余应力的形成原因及对机械零部件切削加工精度的影响,通过对车削、铣削等常用机加工过程中残余应力的形成以及对加工品质、使用寿命、失效形式的分析,有针对性地采取了有效措施,减小残余应力的产生,消除残余应力,从而改善加工品质,提高工件的切削精度和使用寿命。     

车铣加工表面残余应力的研究

金属切削用量对工件的表面残余应力有着重要的影响.通过单因素正交车铣残余应力实验,研究了车铣加工65#钢时,分别改变切削速度vc和轴向进给量fa两个切削用量对已加工件表面残余应力的影响规律,并进行了理论分析.同时对比了车铣加工与一般车削加工的残余应力状态.研究结果表明随着切削速度vc的提高,工件表面残余拉应力随之增大,但当切削速度vc超过188.4 m/min时,工件表面残余拉应力急剧减小出现压应力;增大轴向进给量fa,工件表面残余压应力减小.     

切削加工表面残余应力研究综述

随着高性能制造技术的发展,对零部件的加工质量提出了更高的要求,已加工表面残余应力作为表面加工质量的重要指标,对机器零部件的使用性能有极大的影响。本文介绍已加工表面残余应力对零件使用性能的影响,论述了切削力和切削温度的研究现状及影响因素;综述了已加工表面残余应力的发展现状并阐述残余应力产生机理及其对表面机械性能的影响;总结了影响加工表面残余应力的因素,从而控制已加工表面残余应力,提高机械加工表面质量。     

切削加工残余应力的有限元分析

在切削加工中,为了提高已加工工件的表面质量,需要研究切削速度和进给量对已加工工件残余应力的影响规律。根据弹塑性有限元理论,利用有限元软件建立了切削模型,得到了不同切削速度和进给量下已加工工件的残余应力。结果表明,增大切削速度有利于增大深层压应力,同时也会增大表面拉应力;增大进给量有利于增大深层压应力,但对表面拉应力的影响无明显规律。     

切削中残余应力释放对工件加工变形影响研究

为了研究加工过程中毛坯初始残余应力的释放对加工变形的影响,在弹塑性理论的基础上,建立了三维铣削仿真加工变形场的有限元分析模型,利用位移约束转换和"单元生死"技术仿真了加工过程中工件装夹和材料的去除。通过仿真数据与实验数据相比较,结果表明:工件毛坯残余应力在铣削加工过程中对称释放有利于减小工件加工后变形。     

随焊氩气激冷控制铝/钢薄板残余应力与变形研究

针对铝/钢异种金属薄板焊接时容易产生残余应力与变形问题，提出采用随焊冷却氩气激冷对其进行控制。建立随焊氩气冷却激冷铝/钢异种金属熔钎焊的数值分析模型，研究不同冷却距离对残余应力和变形的控制效果，探究随焊激冷技术控制焊接变形与残余应力机理；同时，进行随焊激冷铝/钢异种金属熔钎焊试验，对焊接温度场、残余应力与变形进行测量，验证模型的准确性。结果表明，采用最优冷却距离（d=10 mm），进行随焊冷却氩气激冷焊接试验时，纵向残余拉应力峰值和残余压应力峰值分别减小42.1%和74.4%，横向残余拉应力峰值和残余压应力峰值分别降低11.3%和14.4%，铝板和钢板外边缘焊接变形量分别减小67.9%和69.5%。随焊冷却氩气激冷技术可有效控制铝/钢薄板焊接时产生的残余应力与变形。     

Residual stresses in cold-deformed thin items and sheet tempered metal

Using solutions of the mathematical theory of plasticity for a thin elastoplastic layer, four theoretically possible types of distributions of residual stresses over the thickness of cold-deformed items and tempered sheet metal are determined. The results are obtained by studying different types of diagrams presenting the dependence of the stress intensity on the deformation intensity. The obtained theoretical dependences are confirmed by experimental studies. The effect of the residual stresses on the mechanical properties and formability of sheet cold-rolled steel is considered.     

板材粘性介质压力成形粘性附着力影响因素试验研究

针对粘性介质压力成形过程是粘性介质与板材耦合的变形过程,不易确定板材在粘着应力作用下变形行为的情况,自行设计了粘性附着力拉伸试验装置,将粘着应力作为板材拉伸力,直接测量粘着应力对板材变形的作用。采用聚甲基乙烯基聚合物作为成形传力介质,初步研究了粘性附着力拉伸过程板材受到的粘性介质粘性附着力对板材变形的影响以及粘性附着力的影响因素。试验结果表明,增大板材表面压力差、提高粘性介质流动速度及提高粘性介质压力有利于提高粘性附着力的作用。研究结果可为合理利用粘性附着应力作用,提高板材成形性提供理论基础。     

金属带材少无毛刺精密分切加工新工艺分析

在分析金属带材分切加工过程及其主要缺陷和分切毛刺去除技术的基础上,提出将上下成对圆盘刀设置为轴向负间隙、径向正间隙,在分切过程中,金属板材表面形成剪切缺口但不分开,随后增设压力分断辊使残留材料层延性断裂分离,亦即"塑性剪切压迫分离"。通过设置上下圆盘刀间隙,使刃口作用区材料处于压应力状态而塑性剪切变形形成切口,再经分断辊压力作用,产生二次变形分离,实现少无毛刺精密分切加工。     

激光冲击钛合金板料的有限元模拟

激光冲击强化技术（LSP）是一种新型的表面处理技术,它利用激光冲击波作用靶材表面而产生残余压应力场.通过有限元软件模拟（FEM）可以分析激光冲击强化处理后靶材的残余压应力场分布,分析材料表面和深度方向的残余应力场的分布情况.先分析了材料的本构模型、激光冲击波的峰值压力的计算、有限元单元类型的选取、边界条件的处理等条件;再通过有限元软件ABAQUS对激光冲击TC4钛合金板料进行了数值模拟,分析了残余应力场的分布特点.     

Experimental study and computer simulation of fracture toughness of sheet metal after laser forming

Fracture toughness is one of the most important mechanical properties for sheet metal in many applications. However not enough attention has been paid to the effects of laser forming conditions on fracture toughness of sheet metal. This paper presents an integrated fracture toughness model to study fracture toughness of sheet metal after laser forming. Microstructure, distribution of residual stresses and geometry of sheet metal specimen are considered in the model. Results of residual stress from microstructure-integrated finite element modelling of laser forming are incorporated in the model. Low carbon steel is used in this paper to validate the model. The results from the fracture toughness study are found to be consistent with microstructure analysis .     

Continuous-forming method for three-dimensional surface parts combining rolling process with multipoint-forming technology

Flexible rolling is a novel forming process for three-dimensional surface parts, which combines the rolling process with multipoint-forming technology. This process employs a pair of forming rolls as a forming tool. By controlling the gap between the upper and lower forming rolls, residual stress caused by the longitudinal non-uniform elongation of sheet metal makes the sheet metal generate three-dimensional deformation. In this paper, the improvement of the process is introduced that the middle curve radius of the roll gap is much larger than the transverse curvature radius of the forming surface in the forming process. The forming roll rotates around its own axis easily because of the small bending deformation which is suitable for producing three-dimensional surface parts including the wide sheet metal with a relatively small transversal curvature radius. The forming principle is set forth, and corresponding formulations are presented. Finite element analysis model is established, and spherical and saddle surface are simulated. The forming precision and the causes of the shape errors are analyzed through simulated results. The experimental equipment is designed and their experimental results are obtained. Simulation results are in well agreement with the experimental results, which verifies the feasibility of using simulation to guide the experiment. The results of both numerical simulations and experiments show that the proposed process is a feasible and effective way of forming three-dimensional surface parts.     

薄板类零件加工变形的解决方法

薄板类零件在现代产品中的应用非常广泛,针对使用传统的加工工艺、加工设备加工薄板类零件,易造成零件变形的情况。先从薄板类零件变形的类型和原因着手分析,进而从加工工艺、加工技术条件、加工刀具、装夹方法几个方面研究薄板类零件加工变形的解决方法,从而达到减小加工变形的目的。     

激光冲击金属板料变形的 最小激光能量估算及其实验研究

介绍了激光冲击板料变形的机理和冲击波产生的原因,提出了激光冲击板料变形中激光－能量转换体－靶材系统的爆轰波压力估算式。根据此压力估算式和材料的动态屈服强度,对激光冲击板料变形中所需的最小激光能量进行了估算,板料厚度为0.5 mm,约束凹模孔径Φ20 mm,在光斑直径6 mm,脉宽25 ns条件下的不锈钢靶材变形所需的最低脉冲能量大约为11 J。实验结果表明估算的最小激光能量与板料变形所需的能量阈值基本一致,且板料变形量随激光能量的增加呈非线性增大。最小激光能量的估算以及能量与板料变形的实验研究为板料变形的精确控制和预测提供了理论依据。     

A new model for springback prediction in which the Bauschinger effect is considered

Springback prediction is an important issue for the sheet metal forming industry. Most sheet metal elements undergo a complicated cyclical deformation history during the forming process. For an accurate prediction of springback, the Bauschinger effect must be considered to determine accurately the internal stress distribution within the sheet metal after deformation. Based on the foundations for isotropic hardening and kinematic hardening, Mroz multiple surface model, plane strain assumptions, and experimental observations, a new incremental method and hardening model is proposed in this paper. This new model compares well with the experimental results for aluminum sheet metal undergoing multiple-bending processes. As is well known, aluminum is one of the most difficult sheet metals to simulate. The new hardening model proposed in this paper is not only a generic model for springback prediction but also a hardening model for sheet metal forming process simulation.