共查询到20条相似文献,搜索用时 26 毫秒
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Y. G. Duan Y. Vincent F. Boitout J. B. Leblond J. M. Bergheau 《Journal of Mechanical Science and Technology》2007,21(10):1700-1706
Prediction of welding residual distortions is more difficult than that of the microstructure and residual stresses. On the
one hand, a fine mesh (often 3D) has to be used in the heat affected zone for the sake of the sharp variations of thermal,
metallurgical and mechanical fields in this region. On the other hand, the whole structure is required to be meshed for the
calculation of residual distortions. But for large structures, a 3D mesh is inconceivable caused by the costs of the calculation.
Numerous methods have been developed to reduce the size of models. A local/global approach has been proposed to determine
the welding residual distortions of large structures. The plastic strains and the microstructure due to welding are supposed
can be determined from a local 3D model which concerns only the weld and its vicinity. They are projected as initial strains
into a global 3D model which consists of the whole structure and obviously much less fine in the welded zone than the local
model. The residual distortions are then calculated using a simple elastic analysis, which makes this method particularly
effective in an industrial context. The aim of this article is to present the principle of the local/global approach then
show the capacity of this method in an industrial context and finally study the definition of the local model. 相似文献
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Mohammad Riahi Hamidreza Nazari 《The International Journal of Advanced Manufacturing Technology》2011,55(1-4):143-152
Residual stress is lower in friction stir welding (FSW) compared with other melting weldment processes. This is due to being solid-state process in its nature. There are several advantages in utilizing stir welding process. Lower fluctuation and shrinkage in weldment metal-enhanced mechanical characteristics, less defects, and ability to weld certain metals otherwise impractical by other welding processes are to name just a few of these advantages. These have caused an ever increasing attention by the concerned to the process of FSW. In this investigation, three-dimensional numerical simulation of friction stir welding was concerned to study the impact of tool moving speed in relation with heat distribution as well as residual stress. Simulation was composed of two stages. Firstly, thermal behavior of the piece while undergoing the welding process was studied. Heat is generated due to the friction between tool and the piece being welded. In the second stage, attained thermal behavior of the piece from previous stage is considered as inlet heat of an elasto-plastic, thermo-mechanical model for the prediction of residual stress. Also, in the second stage, tool is eliminated and residual stress distribution is found after complete cooling of the piece and disassembly of the clamp. Material characteristic are introduced into the proposed model as temperature-dependent parameters. Obtained residual indicate that heat distribution along thickness varies and is asymmetrical enormously. Moreover, longitudinal residual stress in the weld which increases as speed of process and tool movement ascends. In the prediction of results of residual stress, only heat impact was studied. This was recognized as the main element causing minor difference in results obtained for simulation in comparison with that of actual experiment. 相似文献
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注塑制品残余应力数值模拟的研究 总被引:1,自引:0,他引:1
通过预测和优化注塑成形中的残余应力,可以提高注塑制品最终形状的尺寸稳定性和力学性能。采用线性粘弹性模型,计算了无定形热塑性材料在成形过程中由温度和压力引起的残余应力。该模型可以较好地反映成形过程中的应力松弛现象和保压压力对残余应力的影响。通过采用在时间上进行差分和在厚度方向进行分层处理的方法,结合注塑成形中的特定边界条件,建立了残余应力的数值计算方法,并采用该方法模拟计算了典型注塑件的残余应力。结果表明:在脱模时刻,制品的表层有着较大的拉应力,袁层以下存在着一个应力低谷,在制品中间区域存在着抛物线形的应力分布。 相似文献
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纳米结构WC/12Co涂层精密平面磨削表面残余应力有限元模拟与试验 总被引:1,自引:1,他引:0
对金刚石砂轮精密平面磨削纳米结构WC/12Co涂层的磨削表面残余应力进行有限元模拟,忽略相变影响,基于ANSYS平台,利用ANSYS参数设计语言完成建立模型、给定材料属性、划分单元、加载和求解整个过程。对纳米结构WC/12Co涂层表面磨削残余应力进行试验研究,通过改变磨削条件得到不同磨削条件下残余应力的变化规律。将试验结果与相同磨削条件下的有限元模拟结果进行对比,发现试验结果与有限元模拟结果是一致的,证明了有限元模型的正确性。 相似文献
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作为机械表面强化技术之一,喷丸强化使工件表层发生形变硬化,引入较高的残余压应力,减少了疲劳应力作用下微裂纹的萌生并抑制其扩展,从而显著提高零件的抗疲劳断裂和抗应力腐蚀开裂的能力。基于喷丸残余应力解析计算模型,从余弦函数模型、接触应力模型和球腔膨胀模型三个方面介绍喷丸强化残余应力的产生,进而对喷丸残余应力的仿真预测及影响规律进行论述。为了提高试件疲劳强度而引入的残余压应力会带来影响形位精度的变形,基于此阐述了喷丸残余应力对疲劳性能的影响及其在疲劳过程中的演化,同时论述了喷丸残余应力变形预测及控制的研究现状,最后对喷丸残余应力未来的研究内容与发展方向进行展望。 相似文献
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A. M. Pokrovskii O. A. Volokhovskaya V. G. Leshkovtsev G. Ya. Panovko 《Journal of Machinery Manufacture and Reliability》2007,36(3):302-307
A method to calculate pipeline survivability (operability of a part having cracks) taking into account residual welding stresses is proposed. This method allows one to determine the pipeline’s residual life, i.e., to make a conclusion whether the pipeline may be operated after ultrasonic testing detects cracklike defects of a certain size. 相似文献
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A study on natural aging behavior and mechanical properties of friction stir-welded AA6061-T6 plates
H. Jamshidi Aval S. Serajzadeh 《The International Journal of Advanced Manufacturing Technology》2014,71(5-8):933-941
Mechanical properties, microstructural events, residual stresses, and aging behavior of friction stir-welded AA6061-T6 were investigated in this work. Microstructural and mechanical characterizations of the friction stir-welded joints in as-welded and post-welded conditions were made by means of optical metallography, transmission electron microscopy, X-ray diffraction for determination of residual stresses, tensile testing, and hardness measurements. It was found that weld strength and hardness variations after welding are mainly dependent on the imposed heat input per unit length. Besides, the kinetics of natural aging in the welded samples was found to be noticeable within the first 14 days, and its effect decreases considerably in longer aging durations. The residual stress measurements show that subsequent natural aging leads to considerable relaxation of residual stress of about 22 MPa, while this effect is particularly significant in the stir zone and the thermomechanically affected zone. 相似文献
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针对大型复杂结构件有限元计算效率低下的问题,提出了分段移动温控体热源高效算法,并将该算法应用于挖掘机中框架非连续焊的分层逐项优化中,对分段移动温控体热源模型和逐点移动双椭球热源模型的计算效率进行了对比。结果表明,取对称焊与跳焊相结合的焊接方式所得到的焊接残余应力和角变形量最小,左右两侧立板处焊接残余应力峰值相较于原工艺方案,降幅率分别为38.46%和42.13%,降低效果显著;分段移动温控体热源模型与逐点移动双椭球热源模型模拟结果相比,两者得到的变形量变化趋势一致,计算精度相当,但前者计算效率显著要高。将模拟结果与测量结果进行对比,两者高度一致,验证了热源模型及优化工艺的准确性。 相似文献
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Eslam Ranjbarnodeh Siamak Serajzadeh Amir Hosein Kokabi Stefanie Hanke Alfons Fischer 《The International Journal of Advanced Manufacturing Technology》2011,55(5-8):649-656
In the present study, a thermo-elastic–plastic model was developed in order to evaluate the residual stresses in dissimilar automatic tungsten inert gas (TIG) welds between plain carbon steel CK4 and a ferritic stainless steel AISI409. The effect of welding heat input on the magnitude and the distribution of residual stresses was investigated and the results of simulation were validated by X-ray diffraction measurements. It is shown that the calculated residual stresses are in good agreement with the residual stresses determined experimentally. It was found that the magnitudes of stresses at the weld center line increases with increasing the welding speed. 相似文献
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After presenting general facts about Ni-based self-fluxing alloy coatings and describing the wear and corrosion studies in Part 1, Part 2 of the article deals with the review and systematization of the investigations on behavior of these coatings exposed to external mechanical loading (cracking behavior, adhesive strength, fatigue), residual stresses, and microstructure (particle state, phases, porosity, dilution, dissolution) considering the period from 2000 to 2013. The following deposition technologies are included: flame spraying, high-velocity oxy/air fuel spraying, detonation gun spraying, electric arc spraying, plasma spraying, plasma-transferred arc welding, and laser cladding. In addition to the review of investigations on microstructure and effects of external loading and residual stresses, reference is also given to papers describing the application of the Ni-based self-fluxing coatings, as well as to those in which these coatings were used as a reference material or an addition to obtain a composite coating. 相似文献
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钛合金大厚度试件电子束焊接残余应力有限元分析 总被引:2,自引:0,他引:2
基于热弹塑性有限元理论,建立了钛合金大厚度试件电子束移动热源的焊接残余应力三维数值分析模型,分析研究了厚度为75 mm的TC4电子束焊接试件残余应力分布规律。计算结果表明,大厚度电子束焊接试件在焊缝及其附近宽度约40 mm的范围内存在极其复杂残余应力,试件表面的焊缝及其附近20 mm左右的区域存在着对结构强度有利的横向残余压应力,但试件内部残余应力水平要高于表面的残余应力,尤其是在距起始和收尾端10mm及约1/4厚度处的区域,存在着三向的残余拉应力,且数值较高,对钛合金平板电子束焊接接头力学性能将具有重要影响,应引起足够的重视。钛合金平板电子束焊接残余应力的计算结果与实测结果基本一致。 相似文献
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Fanrong Kong S. Santhanakrishnan Radovan Kovacevic 《The International Journal of Advanced Manufacturing Technology》2013,68(9-12):2419-2430
The direct diode laser application has been found useful in the localized heat treatment of metal parts because of its wider beam and more uniform energy distribution with respect to other lasers with Gaussian-like energy distribution. In this study, an uncoupled thermomechanical finite element model is developed to study the temperature field and thermally induced stress evolution in high-strength dual phase (DP) 980 steel during its direct diode laser heat treatment. Thermal analysis results are experimentally validated through thermocouples and then input into a mechanical model as transient temperature loading in order to acquire the thermally induced stresses and strains. The effect of martensite phase transformation on residual stress distribution in heat-treated DP980 steel is considered. An X-ray diffraction technique is used to measure the residual stress distribution at the top surface of the heat-treated coupons of DP980 steel. The numerical results show that compressive stresses are located at the laser–material interaction zone. After heat treatment, tensile stresses are retained at the heat-treated DP980 steel coupons. There is qualitative agreement between the numerically predicted and experimentally measured residual stresses. The effect of the overlapping ratio on the residual stress and hardness of the heat-treated DP980 steel is also experimentally and numerically investigated. 相似文献
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Yang Du Huan Li Lijun Yang Chuanguang Luo 《Journal of Mechanical Science and Technology》2018,32(1):139-147
In order to avoid the deviation caused by calculating the residual stresses of welding joints with the release coefficients of the same parent metal, a new method has been proposed based on the properties of weld joints. Since the mechanical property of 2195-F Al alloy is close to that of 2219-T87 Al alloy Friction stir welding (FSW) joint, 2195-F Al alloy is selected as the substitute material of 2219-T87 Al alloy FSW joint in the calibration test. Release coefficients of 2195-F Al alloy and proper correction coefficient are used to calculate the residual stresses of 2219-T87 Al alloy FSW joints. Compared to the results calculated with release coefficients of its parent metal, it has been proved that the proposed correction method is more precise in residual stresses measurement of weld joints. The mathematical analysis and the results of verification tests have shown that this new method is reliable, and it will provide guidance in academic research and engineering application of the spherical indentation strain-gauge method. 相似文献
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Finite element modeling of burnishing of AISI 1042 steel 总被引:2,自引:0,他引:2
W. Bouzid Saï K. Saï 《The International Journal of Advanced Manufacturing Technology》2005,25(5-6):460-465
The aim of this study is to analyze the evolution of surface roughness finished by burnishing. Burnishing is done on a surface that was initially turned or turned and then ground. In a previous work, we have defined an analytical model to determine the Rt factor of burnished surfaces in relation to the feed f, the material displacement δ and the roughness Rti of the initial surface. δ has been calculated using the Hertz contact theory which supposes that the behavior of the workpiece material is elastic. Hence, in this paper, we have defined a finite element model in which the elasto-plastic behavior of the piece is taken into account to determine the material displacement δ. This model has also permitted the calculation of the residual stresses related to the macroscopic contact geometry. Good correlations have been found between experimental and finite element results when burnishing an AISI 1042 steel. 相似文献