共查询到20条相似文献,搜索用时 421 毫秒
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基于有限元法对三辊非对称滚弯成形工艺进行了研究,对比分析了三辊非对称滚弯成形和三辊对称滚弯成形过程中,变形区应力场、板材上表面的塑形应变场及卷制力的变化规律。仿真结果表明:侧辊位移进给量相同的工况下,三辊非对称滚弯成形的卷制力大于三辊对称滚弯成形的卷制力;三辊非对称滚弯变形区的纵向应力和径向应力均大于三辊对称滚弯成形的纵向应力和径向应力;三辊非对称滚弯成形板材压弯段的成形质量高于三辊对称滚弯成形的成形质量。最后,经三辊非对称滚弯试验验证,有限元模型的成形误差为6.8%,有较高的精度。 相似文献
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R. Keivani M. Jahazi T. Pham A. R. Khodabandeh M. R. Afshar 《The International Journal of Advanced Manufacturing Technology》2014,73(1-4):409-419
A three-dimensional thermomechanical finite element (FE) analysis is carried out to model and predict the influence of welding sequence on the generation of distortions and residual stresses in large size T-joints. To simulate industrial welding conditions, the influence of nine welding sequences on the magnitude of distortion in both the plate and the stiffener was investigated. The addition of new material during welding was simulated using an element “birth and death” technique, while the moving welding arc was considered as a volumetric heat source with a double ellipsoidal distribution. The investigated material is a structural steel used for fabrication of large size structures in the hydroelectric industry. To calibrate the model and validate the simulation results, welding-induced distortion for one sequence was initially modeled and the results were compared with experimental measurements. The optimum welding sequences for the base plate and the reinforcement plate were determined. The results indicated also that the predicted distortions obtained from three-dimensional FE analysis are in reasonable agreement with experimental measurements. 相似文献
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Zhiyong Zhang He Yang Heng Li Zhijun Tao Dan Wang 《The International Journal of Advanced Manufacturing Technology》2014,72(9-12):1187-1203
The heat rotary draw bending of large-diameter thin-walled (LDTW) commercial pure titanium (CP-Ti) tube is a highly nonlinear thermo-mechanical coupled physical process. Developing a reliable finite element (FE) model for this process is an effective way to investigate the heat loading and the complex bending behaviors. In this study, considering the characteristics of multi-die constraints and local heating, a thermo-mechanical 3D-FE model was established for preheating and heat bending of LDTW CP-Ti tube in terms of both accuracy and efficiency. First, using the static implicit algorithm, a preheating model was developed to predict the temperature distribution of bending tools. In this model, the key issues such as the full-sized geometry modelling, thermal interaction definition, and automatic heating control were solved to increase the simulation accuracy and efficiency. Then, introducing the predictions of preheating model and using the dynamic explicit algorithm, a thermo-mechanical coupled 3D-FE model was established for the heat bending simulation via the geometry modelling simplification, temperature definition of bending tools, realization of non-uniform temperature distribution, etc. Considering the temperature history of bending tools and wall thickness changing of bent tube, the reliability of preheating model and heat bending model was verified by several experiments. The results showed that the maximum relative errors of both predicted temperature and wall thickness changing degree were less than 9 %. Based on the reliable models, the effects of preheating temperature on the temperature distribution of bending tools and wall thickness changing of tube were numerically evaluated. The established model provides the scientific basis for the prediction and control of bending qualities of the heat RDB process, and the modeling method is also of general significance to the other heat-aided forming process. 相似文献
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K. X. Liu Y. L. Liu H. Yang 《The International Journal of Advanced Manufacturing Technology》2013,69(1-4):627-636
The collapsing deformation of an outer flange is the key factor affecting the forming quality of a thin-walled rectangular tube during the rotary draw bending process. Therefore, the collapsing deformation is a problem that needs an urgent solution. Firstly, based on the simplified model for loads and deformation of the outer flange, the force acted by the core die and the bending moment acted by the clamp die are obtained analytically. Then, the analytical formula of collapsing deformation is deduced based on the theory of plate and shell, and finally, the analytical model is validated by comparison with simulated and experimental results. The study is of great significance to elevate the forming quality of a thin-walled rectangular tube during the rotary draw bending process. 相似文献
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Effect of clearance on wrinkling of thin-walled rectangular tube in rotary draw bending process 总被引:1,自引:1,他引:0
Gangyao Zhao Yuli Liu He Yang 《The International Journal of Advanced Manufacturing Technology》2010,50(1-4):85-92
The clearances between tube and various dies have a significant and complicated influence on the onset of wrinkling during the rotary draw bending process. To study the effect of clearance on wrinkling, a 3D finite element (FE) model of the process for thin-walled rectangular aluminum alloy tube has been built using the explicit code ABAQUS/Explicit and validated by comparing the experiment. Then, simulation and analysis of the process have been carried out based on the model. The influence laws of clearances between tube and various dies on wrinkling have been studied and the reasonable combination of clearances obtained using the combination method of 3D FE simulation and orthogonal experimental design. The results show that with the increase of tube mandrel clearance, Δc m, and tube bending die clearance, Δc b, the wrinkling wave number decreases rapidly, whereas the wrinkling wave height increases sharply. The effects of tube wiper die clearance, Δc w, and tube pressure die clearance, Δc p, on wrinkling are not significant. The reasonable combination of clearances is Δc m?=?0.15 mm, Δc b?=?0 mm, Δc w?=?0 mm, and Δc p?=?0 mm. These achievements are helpful to the design and optimization of the process. 相似文献
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Huawen Shen Yuli Liu Haiyan Qi He Yang Shuhui Zhou 《The International Journal of Advanced Manufacturing Technology》2013,68(1-4):651-662
The significant cross-sectional distortion is one of the major problems in the bending of thin-walled rectangular waveguide tube. The cross-sectional distortion, which contains the flange distortion and the web distortion, depends on the stress components distribution. In this paper, the cross-sectional distortion characteristics are investigated using a three-dimensional finite element (FE) model. Results show that: the maximum flange distortion locates at the symmetric line; meanwhile, the maximum web distortion locates at the extrados ridge of the tube. The deformation zone of the tube can be divided into three sub-zones considering the loads and deformation, viz., the clamp die affect zone, the middle zone, and the mandrel/cores affect zone. Then the underlying relations between the cross-sectional distortion and the stress components are obtained. It is found that the flange distortion has a close relation with the circumferential stress. At the same time, the web distortion is relevant to both the tangential and the circumferential stress. The above relations are verified by FE models with different cores number. Moreover, some guidelines are introduced to help reduce the cross-sectional distortion. 相似文献
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The influence of considering the variations in material properties was investigated through continuum damage mechanics according to the Lemaitre isotropic unified damage law to predict the bending force and springback in V-bending sheet metal forming processes, with emphasis on Finite element (FE) simulation considerations. The material constants of the damage model were calibrated through a uniaxial tensile test with an appropriate and convenient repeating strategy. Holloman’s isotropic and Ziegler’s linear kinematic hardening laws were employed to describe the behavior of a hardening material. To specify the ideal FE conditions for simulating springback, the effect of the various numerical considerations during FE simulation was investigated and compared with the experimental outcome. Results indicate that considering continuum damage mechanics decreased the predicted bending force and improved the accuracy of springback prediction. 相似文献
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对船体板架结构在空中近场爆炸载荷作用下的破坏进行研究,根据爆轰波理论及气体膨胀理论计算出空中近场爆炸载荷,应用应力波及塑性动力学理论计算船体板架结构的变形,得到不同工况下板架的破口大小及挠度。通过算例进行验证,计算结果合理,可应用于舰船结构在空中近场爆炸冲击波作用下毁伤的估算,为舰船的安全防护设计提供了依据。 相似文献
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In the present study, the distortion induced in rectangular plate of AISI 304 SS during autogenous GTA welding process is measured experimentally and further validated using Finite element (FE) analysis. The thermal histories are measured at fixed locations over the surface of the plate and the results are compared with FE analysis. The Gaussian surface and Volumetric heat source models are simulated and transient heat transfer analysis is performed. The heat source models have been tested with two different speeds. The effectiveness of change in thermal histories of the heat sources have been studied and reported. In FE analysis, the sequentially coupled thermomechanical analysis is performed using the thermal histories as input and the distortion of the plates are predicted and compared with experimental measurements. The large and small displacement theories are employed for the above purpose and the effectiveness of the theories are reported. The edge deformation of the plates have been measured and validated for both the theories. The residual stress and distortion at the mid span are predicted and discussed. The results predicted using large displacement theory is in good agreement with measured values. 相似文献
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Daw-Kwei Leu 《The International Journal of Advanced Manufacturing Technology》2013,64(1-4):93-103
Novel finite element analyses and a series of experiments are performed to clarify basic characteristics of high-strength steel sheet metal during fabrication by asymmetric V-die bending processes. The proposed strategy for elastic–plastic FE simulation is used to simulate asymmetric V-die bending process to test its viability for friction contact processes. Accordingly, a series of experiments is performed to verify the numerical simulation. The calculation agrees well with the experiment. The effects of process parameters such as lubrication (contact friction), material properties, and process geometries on position deviation in bending point were experimentally tested to determine the dominant parameters for minimizing position deviation in sheet metal bending processes. Moreover, springback phenomenon is also discussed to minimize bending defects and to obtain a precise asymmetric bent component. This study could be used as a process design guideline for asymmetric bending of high-strength steel sheets. 相似文献
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H. Li H. Yang J. Xu H. Liu D. Wang G. J. Li 《The International Journal of Advanced Manufacturing Technology》2013,68(9-12):1989-2004
Regarding increasing applications with mass quantities, diverse specifications, and close quality tolerance, the precision bending of large diameter thin-walled (LDTW) Al-alloy tube should be efficiently achieved. However, bending of LDTW Al-alloy tube is a highly tri-nonlinear process with possible multi-defect, needing strict coordination of various bending tools and processing parameters. Considering the coupling effects of various forming parameters on multiple defects, this study developed a knowledge-based substep methodology to solve the deterministic optimization of LDTW Al-alloy tube bending with multi-objective and multi-variable under multiple factor constraints. Considering narrow forming window under small bending radii (R b?<?2D, R b—bending radius, D—initial tube diameter), a finite element (FE)-based stepwise iterative search method is proposed to optimize key forming parameters of LDTW Al-alloy tube under small R b, and the search direction is based on bending knowledge. While for large R b bending with wide optional ranges of forming parameters, a hybrid optimization approach is used by combining virtual design of experiment, FE simulation, approximate response surface model, sequential quadratic programming algorithm, or genetic algorithm. Using orthogonal experimental method, three-dimensional (3D)-FE simulation, experiential data, and analytical formulae, knowledge on key forming parameters, coupling effects on multiple defects, effect significance, and design rules are obtained as well as initial values and design ranges. By several practical bending scenarios with D up to 100 mm, the proposed substep deterministic optimization methodology for LDTW Al-alloy tube bending is evaluated. 相似文献
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在弯板成型工艺研究中,引入UG三维绘图软件,通过用UG三维绘图软件精确绘制零件,钢管与弯板形体表面相交,去除相交部分,得到零件三维图形,并使用软件对象信息查询功能,取得弯板相贯线详细信息,根据三维坐标数值通过计算转换为二维坐标,绘制出相贯线. 相似文献
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A compact model approach of a network of spring elements for elastic loading is presented for the thermal deformation analysis
of BGA package assembly. High-sensitivity moiré interferometry is applied to evaluate and calibrated the model quantitatively.
Two ball grid array (BGA) package assemblies are employed for moiré experiments. For a package assembly with a small global
bending, the spring model can predict the boundary conditions of the critical solder ball excellently well. For a package
assembly with a large global bending, however, the relative displacements determined by spring model agree well with that
by experiment after accounting for the rigid-body rotation. The shear strain results of the FEM with the input from the calibrated
compact spring model agree reasonably well with the experimental data. The results imply that the combined approach of the
compact spring model and the local FE analysis is an effective way to predict strains and stresses and to determine solder
damage of the critical solder ball. 相似文献