共查询到14条相似文献,搜索用时 15 毫秒
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采用固有应变法预测铝合金焊接变形 总被引:1,自引:1,他引:0
伴随焊接过程而产生的焊接变形和残余应力是影响焊接产品精度和性能的重要因素,至今仍然是工业生产中迫切需要解决的重要课题。目前常用的预测焊接变形的方法是三维热弹塑性有限元法,但是由于现有计算机计算能力的限制,还不能预测很多复杂结构的焊接变形。固有应变法是由日本学者提出的解决复杂结构焊接变形的方法,它忽略了整个焊接过程,直接将固有应变施加于壳单元上,经过一次弹性计算就可得到焊接变形。本文用三维热弹塑性有限元和试验相结合的方法获得了平板对接接头形式下的固有应变,运用固有应变法预测铝合金5052平板对接后的焊接变形,通过计算和试验相结合的方法验证了固有应变法预测铝合金焊接变形的可行性,结果表明,固有应变法能够较准确地预测焊接变形,且所用的时间短。 相似文献
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采用双丝CO2气体保护焊方法焊接30 mm厚Q690D钢板全尺寸液压支架顶梁.基于温度热源和热弹塑性算法对局部顶梁结构焊接变形进行计算,获得焊接固有应变,然后将固有应变施加在全尺寸壳单元顶梁模型上进行弹性计算,最终得到液压支架顶梁结构的焊接变形.结果表明,结合小结构模型的热弹塑性法和大结构固有应变法,能高效预测大型结构的焊接变形且能保证一定精度,预测的液压支架顶梁焊接变形结果与试验结果符合较好;液压支架顶梁的焊接变形主要为角变形,且两侧分布不对称. 相似文献
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Hot plane strain compression tests of 6013 aluminum alloy were conducted at temperatures ranging from 613 to 773 K and strain rates ranging from 10-3 to 10 s-1. A novel model is developed to describe the temperature rise considering deformation heating integrated with heat transfer in tests. The experimental flow stress data are corrected by the proposed novel model. Based on the corrected flow stress, the modified power function constitutive model is developed considering the coupled effects of deformation temperature and strain rate on flow stress. Meanwhile, another two widely used models, temperature-compensated power function and straincompensated hyperbolic sine constitutive model, are also established for the studied 6013 aluminum alloy. Finally, the three constitutive models are compared from the aspects of accuracy, stability and efficiency. It is found that the experimental flow stress is significantly affected by the temperature rise. Furthermore, the influence of heat transfer on temperature rise cannot be ignored. When the constitutive model is established, the coupled effects of deformation temperature and strain rate on flow stress should be considered. The modified power function constitutive model is the best one in describing the flow behavior among the three models. 相似文献
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Prediction of workpiece deformation in a fixture system using the finite element method 总被引:3,自引:0,他引:3
Shane P. Siebenaler Shreyes N. Melkote 《International Journal of Machine Tools and Manufacture》2006,46(1):51-58
Knowledge of workpiece deformations induced by loading in a fixture–workpiece system is important to ensure quality part production. Suitable methods for accurately predicting such deformations are essential to the design and operation of fixtures. In this regard, finite element modeling has been widely applied by researchers and practitioners. However, these studies generally neglect the role of compliance of the fixture body on workpiece deformation. Also lacking is knowledge of the effects of different finite element model parameters on workpiece deformation. This study uses finite element analysis (FEA) to model a fixture–workpiece system and to explore the influence of compliance of the fixture body on workpiece deformation. In addition, the effects of certain finite element model parameters on the prediction accuracy are also examined. Experimental verification of the workpiece deformations and locator reaction forces predicted by the FEA model shows agreement within 5% of the experimental data. For the fixture–workpiece system analyzed in this study, it was found that 98% of all system compliance is captured by modeling just the workpiece and fixture contact tips. The remainder of deformation occurred in the other fixture components. The accuracy and computational time tradeoffs are given for various fixture models. 相似文献
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Jonny Dixneit Florian Vollert Arne Kromm Jens Gibmeier Andreas Hannemann Torben Fischer 《Science & Technology of Welding & Joining》2013,18(3):243-255
ABSTRACTCompared to conventional welding consumables using low transformation temperature (LTT) filler materials is an innovative method to mitigate tensile residual stresses due to delayed martensite transformation of the weld. For the effective usage of LTT filler materials, a deeper understanding of the complex processes that lead to the final residual stress state during multi-pass welding is necessary. Transformation kinetics and the strain evolution of multi-pass welds during welding were investigated in situ at the beamline HEMS@PETRAIII, Germany. Compared to conventional welds, the total strain was reduced and compression strain was achieved when using LTT filler materials. For an optimal use of the LTT effect in the root of multi-pass welds, the alloying concept must be adapted taking care of dilution. 相似文献
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The effect of an atmospheric pressure plasma treated MgO layer on the discharge performance of an alternating current plasma display panel (AC PDP) was investigated by measuring the contact angle, the surface roughness, the composition, the breakdown and sustaining voltages. The plasma cleaning was performed using the He/O2/Ar gas mixture. Higher contact angle (35°) of water droplet on the MgO surface and the MgO surface roughness (90 nm, Rmax) after one day duration in the air was significantly reduced to 4° and 54 nm (Rmax) after the plasma cleaning. After the plasma treatment, the adsorbed CO2, CO, H2O impurities on the MgO surface are effectively removed. The breakdown and sustaining voltages were reduced probably due to the increase of secondary electron emission coefficient of MgO, implying that the plasma cleaning process of the MgO layer is beneficial for the improvement of the discharge performance of the AC PDPs. 相似文献
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《Intermetallics》2014
The microstructural features of the 980 °C isothermally forged Ti–22Al–25Nb (at.%) orthorhombic alloy during heat treatment were quantitatively investigated. The volume fraction of the O phase precipitates, the width and length of the lath O phase, and the diameter of equiaxed grains at different heat treatment temperatures were measured using an image analysis software. Quantitative relationships among heat treatment temperature, microstructure parameters, and microhardness were established. The relationship between microstructure parameters and microhardness was analyzed with a multiple regression analysis technique. The results indicate that the microstructure of this alloy is mainly depended on the heat treatment schedule. Only equiaxed O/α2 grains and B2 matrix existed when the samples were solution-treated above 980 °C, while equiaxed α2 grains, rim O around α2, and equiaxed/lath O could be obtained after the samples were solution treated below 980 °C. The width of lath and acicular O phases, and volume fraction of total precipitates could be controlled in the range of 0.37–0.88 μm, 0.09–0.48 μm and 10.91–60.18%, respectively. Experimental and statistical analysis showed a linear relationship between the microstructure parameters and microhardness. 相似文献
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The determination of elastic constants in anisotropic solids by line-focus acoustic microscopy (LFAM) is discussed. The velocity of leaky surface acoustic waves (SAWs) has been obtained for different directions of propagation (φ) from the V(z) curves. The elastic constants are determined from the comparison of measured and calculated velocities. The principle is based on the minimization of the summation of the square difference ∑|VΦc−VΦm|2, by using a Simplex method. This paper deals with the case of cubic-crystallite solids defined by three independent elastic constants. The influence of the initial values of cij on the final result is discussed in the case of MgO substrate and TiN deposited on MgO substrate. Experimental SAW velocity profile is measured on (100) silicon substrate as a function of φ between [100] and [010] directions. The influence of the transducer parameters and defocusing distance are also discussed. 相似文献