共查询到18条相似文献,搜索用时 140 毫秒
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采用数值模拟和试验相结合的方法比较研究了钛合金薄板常规钨极氩弧焊(TIG)及带热沉的TIG焊焊接过程中温度场的形态与演变历史。相对于预置温度场的静态焊接应力和变形控制技术,带热沉的TIG焊接技术又称动态控制低应力无变形焊接技术(DC-LSND,Dynamically controlled low stress no-distortion)。该技术中。在热源之后紧随起冷却作用的热沉装置。研究结果表明。采用DC-LSND技术在热沉附近形成了中间低两边高的马鞍形温度场,热沉作用部位存在温度低谷,该温度区冷却收缩造成对附近高温区的拉伸作用,使焊缝不协调应变减小,焊缝中的残余拉应力降低,防止了焊接变形的产生。对DC-LSND畸变温度场的研究是了解这种方法控制变形机理的前提。 相似文献
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采用切条应力释放法测量了钛合金TC4薄板常规钨极氩弧焊(GTAW)和动态控制低应力无变形GTAW对接试件中的纵向残余应力和纵向残余塑性应变的分布。测量结果表明,钛合金常规GTAW缝中残余拉应力峰值小于其母材屈服强度,焊缝附近存在残余压缩塑性应变;动态控制低应力无变形GTAW焊技术中热沉的冷却作用使得热源与热沉之间的高温金属承受强烈的拉伸作用,产生拉伸塑性变形,部分抵消了焊接过程中已产生的缩短的塑性变形,使得试件中纵向残余塑性应变减小,焊接残余拉应力峰值降低,残余压应力水平降低。切条应力释放法是一种简便有效的薄板焊后残余应力测量方法,能够满足工程应用的精度要求。 相似文献
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基于动态控制低应力无变形焊接法原理和搅拌摩擦焊特有的应力应变特点,设计开发了可应用于搅拌摩擦焊的单点式热沉和阵列式射流冲击热沉系统.通过两种不同热沉系统在铝合金搅拌摩擦焊中的对比研究,结果表明,单点式热沉虽然可以减小FSW焊接变形,但此种冷却方式会使接头性能大幅度下降,接头强度仅达到常规FSW的80%左右.经过改进的阵列式射流冲击热沉系统可以主动控制FSW过程中各个区域的温度分布,从而有效控制焊接过程的热弱塑性应力应变场,达到动态控制低应力无变形的焊接效果.焊缝氢含量的测试分析表明,阵列式射流冲击热沉系统可以改善接头的残余应力分布,防止冷却水侵入焊缝.带阵列式射流冲击热沉系统的搅拌摩擦焊技术可以实现低应力无变形焊接,且工艺适用性好,具有广阔的应用前景. 相似文献
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《中国有色金属学会会刊》2019,(4)
采用热-弹-塑性有限元法对铝/钢异种金属钨极惰性气体保护(TIG)焊辅助激光对接熔钎焊接(A-LWB)过程进行数值模拟,考虑材料非线性、几何非线性和加工硬化的影响,与单激光焊接(SLWB)过程中温度场、残余应力和焊后变形进行对比。结果表明:数值计算得到的热循环、残余应力和焊接变形与测量结果吻合较好,验证有限元计算方法的有效性。与SLWB相比,A-LWB使得焊缝横向上的高温分布范围变宽,降低焊缝处产生的横向拉应力,缩小焊缝处纵向拉应力的分布范围,在一定程度上减小焊后变形。 相似文献
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《机械制造文摘》2009,(1)
20091057关于焊接塑性应变的计算与讨论/方洪渊…//焊接学报.-2008,29(7):60~63采用数值模拟的方法计算了平板熔焊对接接头的纵向塑性应变的分布和动态演变过程。就目前学者所提出的焊缝存在的拉伸塑性应变的观点与传统的残余压缩塑性应变理论所存在的分歧,对比了考虑熔化现象和不考虑熔化现象两种情况,分析了焊缝中心和热影响区焊接准稳态时纵向塑性应变的变化规律。结果表明,考虑熔化现象和不考虑熔化现象纵向塑性应变结果基本相同,在焊接加热过程中所产生的压缩塑性应变始终大于冷却过程中所产生的拉伸塑性应变,在考虑熔化现象的情况下,其热影响区也始终处于压缩塑性应变状态,只是在移动热源经过后,其压缩塑性应变值在冷却的过程中有所减小。图8参1020091058焊接应力变形原理若干问题的探讨(二)/王者昌//焊接学报.-2008,29(7):69~72提出焊接残余应力形成和消除原理:焊接残余应力不是压缩塑性应变引起的,而是由于焊缝和近缝区金属在“力学熔点“及以下温度冷却收缩受阻产生的;消除焊接残余应力不是产生拉伸塑性应变以减少、抵消和补偿压缩塑性应变,而是将残余弹性应变转变为塑性应变;消除焊接残余应力并不是必须去除固有... 相似文献
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提出焊接残余应力形成和消除原理:焊接残余应力不是压缩塑性应变引起的,而是由于焊缝和近缝区金属在"力学熔点"及以下温度冷却收缩受阻产生的;消除焊接残余应力不是产生拉伸塑性应变以减少、抵消和补偿压缩塑性应变,而是将残余弹性应变转变为塑性应变;消除焊接残余应力并不是必须去除固有应变,部分去除或完全不去除固有应变也能完全消除残余应力.提出随焊后热精确控制应力变形焊接法,既可实现无应力焊接和无应力无变形焊接,也可实现适当压应力无变形焊接和较大压应力微变形焊接;并对传统方法与有限元法进行了分析比较. 相似文献
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Effects of distance between arc and heat sink on stress and distortion in DC-LSND welding technology
The characteristics of temperatures, stresses and strains fields have been studied numerically for a titanium alloy sheet welded with an improved gas tungsten arc welding method, in which a trailing spot heat sink is introduced to control the welding stress and distortion. The impinging jet model is employed to describe the internee heat transfer between the cooling media and the top suufuce of the workpiece. The influcnee of the distance between arc and heat sink is investigated. Results show that there is an ideal range of distance. Using the ideal distance, a low stress and no distortion welding structure can be derived. 相似文献
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《Science & Technology of Welding & Joining》2013,18(5):451-458
AbstractA stress and distortion mitigation technique for Gas Tungsten Arc Welding (GTAW) of titanium alloy Ti–6Al–4V thin sheet is presented. The proposed welding technique incorporates a trailing heat sink (an intense cooling source) with respect to the welding torch, and it is also called the Dynamically Controlled Low Stress No-Distortion (DC-LSND) technique. The development of this mitigation technique is based on both detailed welding process simulation using the advanced finite element technique and systematic laboratory experiments. The finite element method is used to investigate the detailed thermomechanical behaviour of the weld during conventional GTAW and DC-LSND GTAW. With detailed computational modelling, it is found that by the introduction of a heat sink at some distance behind the welding arc, a saddle shaped temperature field is formed as a result of the cooling effects of the heat sink; the lowest temperature exists in the zone where the heat sink is applied. High tensile action on the surrounding zone is generated by abrupt cooling and contraction of the metals beneath the heat sink, which increases the tensile plastic strain developed during the cooling process and decreases the compressive plastic strain developed in the heating process, and therefore mitigates the residual stresses and plastic strains within and near the weld. The experimental results confirmed the effectiveness of the DCLSND technique and the validity of the computational model. With a proper implementation of the DC-LSND technique, welding stress and distortion can be reduced or eliminated in welding titanium alloy Ti–6Al–4V thin sheet, while no appreciable detrimental effects are caused on the mechanical properties of welded joints by applying the heat sink in the GTAW process. 相似文献
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Y. Salehi Yegaie A. KermanpurM. Shamanian 《Journal of Materials Processing Technology》2010,210(13):1690-1701
A 3D thermo-mechanical simulation model was developed to predict distributions of temperature and residual stresses during the gas tungsten arc welding (GTAW) process with a heat sink for Monel 400 plates using finite element method. The model was validated against the experimental measurements of both temperature and released strain in the welded plates. Effects of heat input, pipe diameter and water flow rate in the heat sink welding process were investigated. The results showed that in the GTAW process with a heat sink, the high temperature region was only limited to the vicinity of heat source and the maximum temperature of the sample was much lower than that of conventional GTAW process. This resulted in a lower residual stresses and even compressive stresses near the weld zone. 相似文献
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Yuquan Guo Dongjiang WuGuangyi Ma Dongming Guo 《Journal of Materials Processing Technology》2014,214(12):2891-2899
A three-dimensional finite element model (FEM) was established to reveal the thermal-mechanical behaviors of pulsed laser welding (PLW) with and without trailing heat sink. Experiments were carried out to measure the welding temperature histories, residual distortions and solidification profiles. The simulation results agree well with the corresponding experimental measurements. The peak values of the temperature and transient longitudinal tensile stresses valleys in the weld increase as the cooling intensity increases from 5000 to 15,000 W/(m2 K), while those of the temperature and transient longitudinal compressive stresses near the weld decrease. The peak values of the longitudinal residual compressive stresses and plastic strains, and the maximum deflections in longitudinal and transverse direction decrease as the cooling intensity increases from 5000 to 15,000 W/(m2 K). The magnitudes of the transverse shrinkage distortions increase as the cooling intensity increases from 5000 to 15,000 W/(m2 K). The proper cooling intensity to reduce the residual stresses and distortions of the PLW with the trailing heat sink is detected at 10,000 W/(m2 K). The trailing heat sink is technically feasible for actual pulsed laser restraint welding in Hastelloy C-276 thin sheet structures. 相似文献
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《Journal of Materials Processing Technology》2014,214(6):1228-1235
A two pass butt welding of 6 mm mild steel plates was simulated using 3D finite element model using temperature and phase dependent material properties. Material phase transformations were simulated using suitable phase transformation kinetic models. Mechanical analysis is carried out using nodal temperature and phase proportions as input. Experiments were carried out using liquid nitrogen (LN2) as trailing heat sink. Trailing heat sink helped to reduce the residual stress in the fusion zone (FZ) and heat affected zone (HAZ) although distortions were found be increasing. A parametric study was conducted to study the effect of distance between weld arc and trailing heat sink. The heat sink closer to weld arc reduced both distortions and residual stresses. 相似文献
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H. Purmohamad A. Kermanpur M. Shamanian 《Journal of Materials Engineering and Performance》2010,19(1):13-21
The residual stresses developed during the circumferential butt gas tungsten arc welding (GTAW) process of Incoloy 800H pipes
were simulated using the finite element method. A decoupled thermostructural model was developed in three dimensions. The
element birth and death technique was used for the addition of filler material in the weld pool. The Goldak double ellipsoidal
model was used to simulate the distribution of arc heat during welding. The plastic behavior of the material was described
by Von Mises yield function and the bilinear kinematics hardening was assumed. To validate the thermostructural model, both
temperature and residual stress distributions within the pipes were measured using thermocouples and strain gages, respectively.
Good agreements were found between the experimental and simulation results. The model was then used to predict distribution
of residual stresses during the GTAW of Incoloy 800H pipes and to study effects of process parameters on the residual stresses. 相似文献