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A modified membrane finite element with a proper formulation for planar anisotropic materials is introduced to correctly enhance the flexural rigidity not only within an element but among elements. The strain energy term in the formulation is decomposed into the membrane energy term for mean stretching and the bending energy term for pure bending. This procedure needs careful evaluation for the orientation of the anisotropic axes. The formulation is then combined with an effective algorithm to deal with the contact between the material and the dies. Distribution of the blank holding force is calculated in each step according to the thickness in the flange region. The calculation employs a special relation between the thickness and the blank holding force. The simulation examples demonstrate the validity and versatility of the computer code by showing the earing phenomenon in circular cup drawing and the variation of the blank holding force in rectangular cup drawing. The results shows that the thickness variation in the flange region redistributes the blank holding force during the deformation. The present algorithm can predict more precise contour lines in the flange region and a more precise shape and strain distribution. 相似文献
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3104铝合金薄板深冲制耳的有限元模拟 总被引:6,自引:0,他引:6
采用由板材织构信息进行加权的CMTP屈服函数并考虑了摩擦和压边力的变化对3104铝合金薄板的深冲制耳进行了有限元模拟;并与采用Barlat(1991)屈服函数的预测值及实测值进行了比较;分析了深冲过程中圆片的厚度变化规律;讨论了进一步提高预测精度需考虑的因素。结果表明:采用CMTP屈服函数模拟的制耳轮廓与实测值比较吻合,随摩擦和压边力的增加,制耳轮廓高度也增加;且比采用Barlat(1991)屈服函数模拟的精度要高。模拟深冲过程中圆片厚度的变化规律与实际情况一致。 相似文献
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Accurate optimization of blank design in stretch flange based on a forward–inverse prediction scheme
Fung-Huei Yeh Ming-Tsung Wu Ching-Lun Li 《International Journal of Machine Tools and Manufacture》2007,47(12-13):1854-1863
This paper presents a forward–inverse prediction scheme that combines explicit dynamic finite element method (FEM), true strain method (TSM), and adaptive-network-based fuzzy inference system (ANFIS) to determine the anisotropic optimum blank in stretch flange process. It is not easy to guess the blank shape in stretch flange process using traditional trials. The forward–inverse prediction scheme can efficiently determine the optimum blank and improve the shrink phenomenon of the flange target. In the present study, the initial shape of the nearby optimum blank could be predicted quickly by the forward scheme of TSM at first. Then, several blanks with parallel curves to this shape are created and analyzed by explicit dynamic FEM to establish the training database for the inverse scheme of ANFIS. From the hybrid-learning algorithm, ANFIS can be efficiently trained for the optimum blank shape, and the prediction knowledge rule database can be accomplished. Using the trained ANFIS, the exact optimum blank shape of stretch flange can be inversely predicted more correctly and efficiently. Moreover, the stretch flange experiments are performed using non-optimum and optimum blanks. It also shows that a good agreement is achieved from comparison between simulated and experimental results, such as punch load, punch stroke and deform shape. From this investigation, the forward–inverse scheme is proved to be able to supply a useful optimum preform in the metal forming category. 相似文献
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1 INTRODUCTIONTheeffectofstressstatesonaxisymmetricsheetformabilityhasbeenstudiedundertheconditionofsolidmetalpunchforming [14 ] ,andtheeffectofblankholderpressure (BHP) ,frictioncoefficientandpunchconfigurationonthestressstateshasbeenob tained .Becauseofthedisadvantagesofsolid punchforming ,newformingtechnologyisneededtoim provethestressstatesofthesheetinformingprocessandtomeettherequirementofforminglow plastici ty ,complexshapeparts .Viscouspressureforming(VPF)isarecentlydevelopedfle… 相似文献
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金属板材冷冲锻成形是近年来发展起来的复合成形新技术,其特点是板材冲锻时不但完成零件形状的成形,还兼有局部结构的体积成形,如凸柱成形.针对带有凸柱的散热板基座,通过对1100-H14铝合金板材冷冲锻成形有限元模拟,探讨坯料厚度、坯料形状、摩擦因数及模具结构对凸柱成形的影响规律.结果表明:坯料越厚,越有利于凸柱成形;摩擦因数越大,越有利于凸柱成形;圆形坯料形状及带有背压的模具结构有利于凸柱成形.模拟结果与实验结果吻合. 相似文献
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本文用大变形刚塑性有限元模拟正方形板料在方冲头拉延下的凸缘变形过程,并以所获得的工件形状与金属流动方向为依据,对初始板料形状进行修正。对修正后的坯料形状进行二次模拟,获得了与给定凸缘形状基本吻合的拉延件形状。文中对不同凸缘圆角对极料优化形状的影响作了计算,讨论了在保证边界轮廓位置不变的条件下网格划分的方法。 相似文献
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The objective of this paper was to investigate the characteristics of hole flanging with ironing of thick sheet metals. A
number of experiments were pertbrmed by using a conical punch. Several blanks of different thickness which were made from
commercially pure aluminum were used. A lubricant based on aluminum fluoride and metallic stearate was applied to both sides
of the blank. The effects of blank thickness on the punch load and the finished shape in the hole flanging with ironing were
investigated. The experimental results were compared with the simulated results obtained by the rigid-plastic FEM. The results
have demonstrated that the rigid-plastic FEM can be used effectively for predicting the punch load and the finished shape. 相似文献
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Lin Wang L.C. Chan T.C. Lee 《International Journal of Machine Tools and Manufacture》2007,47(12-13):1929-1940
In this paper, a process model of the controlled forming process was proposed based on Response Surface Methodology (RSM). The forming process was controlled through adjusting the blank holder force (BHF) varied with the time and other process parameters. Due to the wide application and the high efficiency of the Finite Element Method (FEM), this is the chief tool used instead of experiments to carry out the controlled forming process. Deep drawing processes of material SPCC were simulated, and the simulation results were verified by the experiments. The forming processes with several types of time variant BHF were simulated and compared to find a suitable one to achieve our desired product shape. The comparison implied that the staircase-shaped time variant BHF can direct the strain path to the desired place to acquire a targeted product.Then the process model was built up using RSM to the forming process with time variant BHF and friction coefficient. The equations explored the relationship between the principal strain of fracture risk elements and the working parameters, including BHF. Three–dimensional (3D) principal strain surfaces of the element were drawn, which visualised the relationship between the principal strain and the working parameters, especially BHF. Using the model, it is feasible to acquire a fracture-free product through regulating the BHF profile. 相似文献
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R. Padmanabhan M.C. Oliveira A.J. Baptista J.L. Alves L.F. Menezes 《Journal of Materials Processing Technology》2009,209(5):2402-2411
Deep drawing is a forming process controlled by a number of parameters. The initial blank shape is one of the most important process parameter that has a direct impact on the quality of the finished part. This paper describes a new method to determine the optimal blank shape for a formed part using the deformation behaviour predicted by finite element simulations and salient features of NURBS surfaces. The proposed optimization method involves an initial blank shape, which is iteratively trimmed according to the deep drawing simulations results, to achieve the final optimal blank shape. The deep drawing simulations were carried out using DD3IMP, an implicit in-house finite element code. Parametric NURBS surfaces are used to optimize the initial blank shape based on the deformation behaviour predicted by numerical simulation. The proposed method can determine the optimal blank shape for any part within a few iterations. 相似文献
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Tung Phan Van Katja JöchenThomas Böhlke 《Journal of Materials Processing Technology》2012,212(12):2659-2668
In this work, a ferritic stainless steel (DC04) is investigated numerically on the micro and the macro scale. Single crystal orientations extracted from 2D electron backscatter diffraction (EBSD) data are reduced by using two methodically different methods. Based on these reduced data sets, a two-scale Taylor type model is applied at the integration points of the finite elements to simulate a deep drawing process. The earing profiles of the simulated cups are compared to the experimental data. In addition, the influence of the variation of the sheet holder force on the earing profile of the drawn cup for different friction coefficients is discussed. It is found that incorporating experimental microstructural information in the two-scale simulations, realistic earing profiles are obtained. With regard to efficient computation, a coarse FE model is used, resulting in a larger average cup height than the experimental slope. Nevertheless, reducing the friction coefficient in the model, the slope of the cup height agrees very well with the experiments which is expected to be obtainable for a finer FE mesh and the experimental friction coefficient as well. 相似文献
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Thermo-mechanical coupled analysis of hot ring rolling process 总被引:1,自引:0,他引:1
A 3D rigid-plastic and coupled thermo-mechanical FE model for hot ring rolling(HRR) was developed based on DEFORM 3D software, then coupled heat transferring, material flow and temperature distribution of the ring in HRR were simulated and the effects of process parameters on them were analyzed. The results show that the deformation nonuniformity of ring blank increases with the increase of the rotational speed of driver roll and friction factor or the decrease of the feed rate of idle roll and initial temperature of ring blank. The temperature nonuniformity of ring blank decreases with the increase of the feed rate of idle roll or the decrease of initial temperature of ring blank and friction factor. There is an optimum rotational speed of driver roll under which the temperature distribution of ring blank is the most uniform. The results obtained can provide a guide for forming parameters optimization and quality control. 相似文献
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针对涡旋式压缩机花盘在温锻成形过程中出现的内壁开裂现象,对原成形工艺进行数值模拟,研究了终锻成形中的裂纹形成机理,并发现损伤值达到1.28。为了消除花盘侧壁开裂问题,提出在原工艺基础上改变毛坯形状,以提高金属流动的合理性,使锻件材料填充良好,变形均匀。通过对具有不同形状的毛坯成形过程的对比分析,给出了最优的毛坯形状:增大预锻件凹口深度,采用阶梯状凹口,针对外壁的截面形状,将原有的阶梯状改为圆弧状。采用改进的方案温锻花盘时,裂纹发生处的损伤值明显降低,仅有0.732,裂纹消失,各项指标都达到技术要求。改进后涡旋式压缩机花盘的成品率达到100%。 相似文献
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为了评估DP980高强钢材料的成形与回弹特性,通过加载-卸载实验与单向拉伸-压缩循环加载实验,获得了考虑包申格效应的吉田-上森硬化模型参数,并对DP980高强钢的U形弯曲实验进行了研究。实验结果表明,DP980高强钢U形件在凹模圆角处易开裂,在成形过程中需减小压边力并增大凹模圆角。由于材料的回弹量与施加的压边力有关,可通过增大压边力来减小U形件的回弹,但压边力过大又可能导致开裂,因此,需合理选择压边力。同时,对U形件成形后的回弹进行仿真分析,仿真中分别采用等向硬化模型与吉田-上森硬化模型,通过将实验数据与模拟的回弹结果进行对比分析发现,采用吉田-上森硬化模型的仿真结果与实验结果吻合良好,证明了吉田-上森硬化模型模拟回弹的准确度较高,可以应用于回弹仿真中。 相似文献