共查询到20条相似文献,搜索用时 15 毫秒
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以热弹塑性理论为基础,建立球栅阵列PBGA焊点在回流焊工艺中焊接应力的有限元模型,利用ANSYS的热结构耦合功能,采用生死单元法对Sn-Ag-Cu焊点回流焊的冷却过程进行数值模拟分析.焊点冷却结晶后的初始阶段,等效应力随温度的降低快速增加,当焊点的温度逐渐降低至室温时,等效应力为最大.结果表明,在回流焊接工艺中,PBGA焊点的裂纹极可能发生在焊料冷却结晶后的初始阶段,在焊点高应力集中区首先开裂,并在应力的作用下沿界面逐渐扩展.对焊料凝固初期冷却速率的控制是减少焊接裂纹产生的有效方法. 相似文献
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Yinzhou YanLingfei Ji Yong BaoYijian Jiang 《Journal of Materials Processing Technology》2012,212(6):1257-1270
A major challenge in laser percussion drilling of thick-section ceramics is to obtain a low taper and low spatter deposition hole leading to high quality post-processing. In order to achieve the fine hole drilling, it is important to understand the mechanism of laser percussion drilling. In this paper, an experimental and numerical study on laser percussion drilling was carried out. A two-dimension (2D) axisymmetric finite element (FE) model for simulation of temperature field and proceeding of hole formation during percussion drilling was developed. The FE model was validated by the corresponding experiment. Furthermore, a theoretical model for evaluation of temperature at melt front and velocity of melt ejection was presented in order to further validate the FE model and study the spatter deposition. The effects of laser peak power, pulse duty cycle and pulse repetition rate on hole diameter and spatter deposition were investigated by the developed models and experiments, in which the simulated results were in good agreement with the experiments. The study indicated that the size and temperature of the melt front significantly affected the hole diameter formation and spatter deposition during laser percussion drilling. The characteristic of melt front was mainly determined by the employed laser peak power, pulse repetition rate and pulse duty cycle. Based on the experimental and numerical study, the process parameters were optimised and a drilled-hole with low taper and low spatter deposition was obtained using a 3.5 kW CO2 laser. A microstructural and element compositional study was also performed in this work, by which the characteristics of microstructure and element composition in HAZ around laser drilled hole were revealed. 相似文献
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利用有限元分析软件MARC对"沟槽-蒙皮"结构的激光焊接过程进行三维数值模拟,涉及了激光焊接复合热源模型的确定,热力学边界条件的简化,数值模拟温度场的验证,以及残余变形和应力分布结果的分析和讨论.研究了结构上规则排列的多道焊缝的施焊顺序对焊接残余应力和变形的影响.结果表明,不同焊接顺序所产生的变形态相同,变形量有区别,而残余应力的分布则不同,以由外向中的对称顺序进行焊接时,结构的焊后残余变形最小,残余应力的分布比较均匀,峰值最小. 相似文献
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中厚船舶钢板激光弯曲成形几何效应的数值模拟 总被引:2,自引:0,他引:2
建立板材激光弯曲的三维非线性准静态弹塑性热力耦合有限元模型。使用有限元软件 MSC Marc对中厚船舶钢板的激光弯曲成形过程进行数值模拟。计算了船舶钢板激光弯曲成形过程的温度场和变形场, 并进行相应的实验验证。模拟结果与实验结果吻合较好。用建立的模型对中厚船舶钢板的激光弯曲成形过程中钢板的几何效应进行数值模拟, 讨论了一定工艺条件下钢板几何参数与弯曲角度之间的关系, 为在将来实际生产中制定和优化钢板激光弯曲成形的工艺参数提供理论依据。 相似文献
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NUMERICAL SIMULATION OF THE TEMPERATURE FIELD IN A SOLDER BALL UNDER PULSED LASER AND ITS EFFECT ON THE VIBRATION OF THE SOLDER 总被引:1,自引:0,他引:1
1.~hoInthesurfacemountingtechniqUeforelectroniccomponents,muchattentionisPaidtOfledesssolderingmethods,becausetheyprovidehighreliabilityandarefaVoboleintennsofenvironmentprotection.ItisrecognizedthatthekeyPOinttOrealizeflagnesssolderingistoremovetheoxidefilmonthesurfaceofworkpieceandavoidre--.idati@[lj.Inthispaper,thetemperatu-redistributionandthevibrationfeatUreofaSn--Phsolderunderacontinuouslyptilsedlaserisanalyzed,whichhelpstounderstandthemechAnsmofultrasonicinducedbycontinuouslyPulsedl… 相似文献
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Yinzhou Yan Lin Li Kursad Sezer David Whitehead Lingfei Ji Yong Bao Yijian Jiang 《International Journal of Machine Tools and Manufacture》2011,51(12):859-870
A major challenge in laser fusion cutting of thick-section ceramics is to overcome the thermal-stress induced cracking, which leads to catastrophic breakdown of the material integrity. In order to achieve crack-free cutting of ceramics, it is important to understand the mechanism of the transient temperature field and resulting stress distribution effect on crack formation. In this paper, both experimental and theoretical investigations are reported to understand crack formation characteristics in fibre laser cutting of thick-section Al2O3 ceramics. A three-dimensional (3D) finite element (FE) model for simulation of the transient temperature field and thermal-stress distribution together with material removal in laser cutting was developed. Crack formation characteristics were predicted by the model and validated by experiments. The effects of four process parameters i.e. laser peak power, pulse duration, pulse repetition rate and feed rate on temperature field, resulting stress distribution and potential crack formation were also investigated in this work. The study indicates that a transition from compressive to tensile stresses can be resulted in as the laser cutting parameters change, which is beneficial to resist the crack formation. Based on the experimental and numerical investigations, the process parameters were optimised and the fibre laser crack-free cutting of 6-mm-thick alumina was demonstrated for the first time. 相似文献
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Asma Belhadj Jamel Bessrour Jean-Eric Masse Mahmoud Bouhafs Laurent Barrallier 《Journal of Materials Processing Technology》2010,210(9):1131-1137
In this paper, a three-dimensional finite element model is developed to simulate thermal history magnesium-based alloys during laser beam welding. Space–time temperature distributions in weldments are predicted from the beginning of welding to the final cooling. The finite element calculations were performed using Cast3M code with which the heat equation is solved considering a non-linear transient behaviour. The applied loading is a moving heat source that depends on process parameters such as power density, laser beam dimensions and welding speed, and it is associated to moving boundary conditions. Experiments were carried out to determine temperature evolution during welding and to measure the laser weld width. By comparing the thermal model answers with the measurements, it is found that numerical simulations results are in a good agreement with the experimental data. 相似文献
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激光+GMAW复合热源焊接过程热-力耦合数值分析 总被引:3,自引:2,他引:1
从宏观的焊接热过程出发,根据激光+GMAW复合热源焊接的特点,提出了适用于复合热源焊接的“双椭球体+峰值递增圆柱体”组合式体积热源分布模式;建立了激光+GMAW复合热源焊接过程的有限元模型,数值计算了焊接温度场和焊缝横截面的形状尺寸,计算结果与试验结果吻合良好,证明了组合式体积热源模型的合理性和适用性. 采用焊接温度场的计算结果,进一步对复合热源焊接和GMAW的焊接变形和残余应力进行了数值模拟和对比分析. 结果表明,在焊缝熔深基本相同的情况下,复合热源焊接的焊接热输入、焊缝熔宽、焊接变形和高应力区域范围等均比GMAW小. 研究结果印证了激光+GMAW复合热源焊接工艺的优越性,并为焊接工艺参数的优化提供了基础理论数据. 相似文献
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激光熔覆过程热力耦合有限元温度场分析 总被引:12,自引:0,他引:12
根据激光熔覆的特点,建立了激光熔覆温度场分析模型,对送粉激光熔覆过程温度场进行了有限元分析。分析结果表明,熔覆层最高温度与激光功率、基体预热温度成正比例关系,而最大冷却速率与激光功率、基体预热温度成反比例关系。提高基体预热温度对降低熔点处材料冷却速率效果显著,而提高激光功率对降低熔点处材料冷却速率有一定作用,但效果并不明显。 相似文献
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以黄铜为基材,钴基合金为熔覆粉末,采用预置粉末方式实现激光熔覆加工,对此过程建立三维有限元模型。考虑温度变化对热物性参数的影响以及表面对流换热和辐射散热等影响因素,使用SYSWELD软件对激光熔覆过程中的温度场和应力场进行了分析。结果表明,激光熔覆过程中的温度场变化是由非稳态到稳态的过程,熔覆层横截面上不同点热循环曲线呈锯齿状衰减;最大残余应力值出现在靠近基体的熔覆层中间位置;在其他工艺参数不变的情况下,扫描速度为8mm/s,熔覆过程的稀释率为11.5%,可以获得良好的冶金结合,并进行了试验验证;利用SYSWELD软件的校核功能,获得了扫描速度为6和10mm/s熔覆过程中较为合适的功率分别为2.96和3.82kW。 相似文献
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采用有限元数值模拟方法研究了冷却过程在Al Al2 O3 异种材料结构件钎缝处导致的剪切应力分布。计算结果表明 :最大剪切应力位于钎缝圆角处和靠近钎缝圆角的Al2 O3 陶瓷 /Cu镀层金属界面处 ,同时中间层合金的热膨胀系数与Al的热膨胀系数相匹配时 ,可以最大限度减小剪切应力 相似文献