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为研究地铁车辆制动箱焊接接头的疲劳寿命,根据实际结构建立4节点壳单元有限元模型,给出搭接焊和T型焊的焊缝建模方法.在3种振动工况下,运用主S N曲线法计算焊缝的等效结构应力和对应损伤比.结果表明:该地铁车辆制动箱焊接结构设计合理可靠;通过与实体单元模型计算结果进行对比证明壳单元模拟焊缝的合理性;在不同尺寸单元下对比2种疲劳评估方法,结果表明名义应力法预测疲劳寿命的准确性较低. 相似文献
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《Advances in Engineering Software》2003,34(9):569-575
The aircraft industry has only recently begun to explore possible application of welding as an alternative joining method for the design of future large civil airliner wing. One of the main obstacles, encountered in the past years, to welding application within the aircraft industries were due to failure in the weldments, caused by high tensile residual stresses present in the region of the weld, reducing drastically fatigue strength of welded joints. Improvement in the fatigue life of the welded joint can be obtained if compressive residual stresses are introduced at the weld region.Shot peening is a manufacturing process intended to give aircraft structures the final shape and to introduce a compressive residual state of stress inside the material in order to increase fatigue life. This paper presents the modeling and simulation of the residual stress field resulting from the shot peening process. The results achieved show that a significant decrease of welding induced tensile residual stress magnitude can be obtained. Good agreement between experimental and numerical results was achieved. 相似文献
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This paper deals with a numerical and experimental investigation on the influence of residual stresses on fatigue crack growth in AA2024-T3 friction stir welded butt joints. The computational approach is based on the sequential usage of the Finite Element Method (FEM) and the Dual Boundary Element Method (DBEM). Linear elastic FE simulations are performed to evaluate the process induced residual stresses, by means of the contour method. The computed stress field is transferred to a DBEM environment and superimposed to the stress field produced by a remote fatigue traction load applied on a friction stir welded cracked specimen; the crack propagation is then simulated according to a two-parameter growth model. Numerical results have been compared with experimental data showing good agreement and evidencing the predictive capability of the proposed method. The obtained results highlight the influence of the residual stress distribution on crack growth. 相似文献
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以T形焊接接头为研究对象,将可能发生疲劳破坏的焊趾截面和焊喉截面的节点力转换为相对于中面焊线的等效节点力和弯矩,并利用平衡等效原理转化为线力和线弯矩,基于材料力学公式求出截面的结构应力,解决应力对网格尺寸敏感的难题。从焊缝疲劳破坏的机理出发,基于Paris断裂力学公式推导以等效结构应力为变量的一条主S-N曲线,评估焊缝的疲劳寿命。分析结果发现:采用主S-N曲线法评估的寿命与试验值最接近且破坏位置准确,该主S N曲线法准确性较高。 相似文献
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正交异性钢桥的肋-桥面板焊缝处的疲劳裂纹是典型的三维裂纹问题,但是现在普遍采用平面应变二维裂纹模型对其进行断裂力学分析.基于Schwartz-Neuman交替法建立正交异性钢桥肋-桥面板焊缝裂纹的局部三维断裂力学分析模型;评估焊缝处表面裂纹的形状和深度对应力强度因子的影响;采用Paris公式估算等应力幅下焊缝的疲劳寿命.计算结果表明:用平面应变二维裂纹模型进行正交异性钢桥的肋-面板焊缝的断裂力学分析会严重低估其疲劳寿命;采用三维断裂力学模型进行肋-桥面板焊缝裂纹的疲劳寿命分析十分必要. 相似文献
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在当前汽轮机的某些极限设计工况下,基于无限寿命的线弹性考核规范已经无法满足当前的工程设计要求,需要发展弹塑性强度计算方法以及有工程意义的强度评估准则,并在此基础上引入低周疲劳寿命考核方法对零部件寿命进行分析预测.对某汽轮机末级长叶片进行弹塑性有限元分析,提出将基于局部应力 应变法的低周疲劳分析理论与商用疲劳分析软件相结合的方法对叶片进行强度设计的方法和流程.结果表明:所提出的弹塑性分析以及疲劳寿命评估方法能很好地反映长叶片的实际强度,有助于进一步制定一套完善的适合工程应用的长叶片强度评估标准,从而提高叶片的设计水平. 相似文献
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根据ASME标准的计算公式,开发基于主S-N曲线法的焊接结构疲劳寿命预测软件,其核心是采用网格不敏感结构应力及一条主S-N曲线的方法计算焊接结构的疲劳寿命.系统开发选用面向对象的VC++语言和OpenGL开发库;采用模块化程序设计的思想将系统划分为有限元定义模块、焊缝定义及结构应力计算模块、载荷谱管理及雨流计数模块、主S-N数据管理及疲劳计算模块等4个核心模块;开发专用的接口程序和三维交互界面.该软件系统已在我国轨道交通制造行业中得到良好应用.以某货车车体关键焊缝疲劳寿命计算为典型实例,用软件系统进行车体疲劳寿命评估,计算结果表明该货车焊缝满足设计要求,同时也证明该软件系统的实用性和高效性. 相似文献
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Fatigue constrained topology optimization 总被引:1,自引:0,他引:1
Erik Holmberg Bo Torstenfelt Anders Klarbring 《Structural and Multidisciplinary Optimization》2014,50(2):207-219
We present a contribution to a relatively unexplored application of topology optimization: structural topology optimization with fatigue constraints. A probability based high-cycle fatigue analysis is combined with principal stress calculations in order to find the topology with minimum mass that can withstand prescribed variable-amplitude loading conditions for a specific life time. This allows us to generate optimal conceptual designs of structural components where fatigue life is the dimensioning factor. We describe the fatigue analysis and present ideas that make it possible to separate the fatigue analysis from the topology optimization. The number of constraints is kept low as they are applied to stress clusters, which are created such that they give adequate representations of the local stresses. Optimized designs constrained by fatigue and static stresses are shown and a comparison is also made between stress constraints based on the von Mises criterion and the highest tensile principal stresses. The paper is written with focus on structural parts in the avionic industry, but the method applies to any load carrying structure, made of linear elastic isotropic material, subjected to repeated loading conditions. 相似文献
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Optimization of laser butt welding parameters based on the orthogonal array with fuzzy logic and desirability approach 总被引:1,自引:0,他引:1
This paper presents the study carried out on 3.5 kW cooled slab laser welding of 904 L super austenitic stainless steel. The
joints had butts welded with different shielding gases like argon, helium and nitrogen at a constant flow rate. Super austenitic
stainless steel (SASS) normally contains high amount of Mo, Cr, Ni, N and Mn. The mechanical properties are controlled to
obtain good welded joints. The quality of the joint is evaluated by studying the features of weld bead geometry such as bead
width (BW) and depth of penetration (DOP). In this paper, the tensile strength and bead profiles (BW and DOP) of laser welded
butt joints made of AISI 904 L SASS are investigated. Taguchi approach is used as statistical design of experiment (DOE) technique
for optimizing the selected welding parameters. Fuzzy logic and desirability approach are applied to optimize the input parameters
considering multiple output variables simultaneously. Confirmation experiment has also been conducted for both the analyses
to validate the optimized parameters. 相似文献
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Emmanuel Jakobowicz Christian Derquenne 《Computational statistics & data analysis》2007,51(8):3666-3678
Partial least squares (PLS) path modeling has found increased applications in customer satisfaction analysis thanks to its ability to handle complex models. A modified PLS path modeling algorithm together with a model building strategy are introduced and applied to customer satisfaction analysis at the French energy supplier Electricité de France. The modified PLS algorithm handles all kinds of scales (categorical or nominal variables) and is well suited when nominal or binary variables are involved. PLS path modeling and structural equation modeling are confirmatory approaches and thus need an initial conceptual model. A two-step model building strategy is presented; the first step is based on Bayesian networks structure learning to build the measurement model and the second step is based on partial correlation and hypothesis tests to build the structural model. Applications to customer satisfaction data are presented. 相似文献
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Tubular members have been used for constructing offshore structures. Large-scale fatigue tests of welded tubular K-joints under the balanced in-plane bending brace were carried out to investigate the fatigue behavior of API 2W Gr.50 steel produced by POSCO. The experimental results were verified by numerical approaches and compared with the IIW, DnV RP-C203 and API RP 2A-WSD design curves. The test results based on the hot spot stress were in agreement with the design curves. The SCF factor for tubular K-jo... 相似文献
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Dissimilar welded joints are commonly used in fossil power plants to connect martensitic steel components and austenitic stainless steel piping systems. The integrity for such welded structures is depended on residual stresses induced by manufacturing process. In this paper, the characteristics of residual stresses on the dissimilar welded pipe between T92 steel and S30432 steel were investigated using finite element method. Moreover, the effects of heat input, groove shape and layer number on the residual stress distribution were studied to find the approach to reduce the residual stress. The numerical results revealed that the hoop and axial stress in heat affected zone (HAZ) of T92 steel side of the dissimilar welded joint had sharp gradients. By decreasing the groove angle, the peak values of the hoop and axial stress on T92 steel side were reduced greatly while the peak values in welded metal and HAZ of S30432 steel side differed little. Furthermore, more layer number and less heat input decreased the peak value of the tensile residual stress on welded metal and S30432 steel side, but had little effect on the residual stress in T92 steel side. 相似文献
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为评估某铝合金地铁车辆的疲劳寿命,采用美国ASME标准中的网格不敏感的主S-N曲线法对该车焊缝进行疲劳寿命预测.用HyperMesh对车体进行有限元建模,并对焊缝处网格细化;用ANSYS计算焊缝处应力;运用自主开发的FE-Weld软件对其进行等效结构应力的计算和疲劳寿命的预测;对疲劳寿命不符合设计要求的结构进行改进和优化,改进后结构的疲劳寿命符合设计要求.网格不敏感的主S-N曲线法具有重要工程应用推广价值. 相似文献
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Damage tolerance analysis (DTA) was considered in the global design optimization of an aircraft wing structure. Residual strength and fatigue life requirements, based on the damage tolerance philosophy, were investigated as new design constraints. The global/local finite element approach allowed local fatigue requirements to be considered in the global design optimization. AFGROW fatigue crack growth analysis provided a new strength criterion for satisfying damage tolerance requirements within a global optimization environment. Initial research with the ASTROS program used this damage tolerance constraint to optimize cracked skin panels on the lower wing of a fighter/attack aircraft. For an aerodynamic and structural model of this type of aircraft, ASTROS simulated symmetric and asymmetric maneuvers during the optimization. Symmetric maneuvers, without underwing stores, produced the highest stresses and drove the optimization of the inboard lower wing skin. Asymmetric maneuvers, with underwing stores, affected the optimum thickness of the outboard hard points. Subsequent design optimizations included DTA and von Mises stress constraints simultaneously. In the configuration with no stores, the optimization was driven by the DTA constraint and, therefore, DTA requirements can have an active role to play in preliminary aircraft design. 相似文献