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建立了塑料球栅阵列(plastic ball grid array,PBGA)器件叠层焊点应力应变有限元分析模型,基于该模型对叠层无铅焊点在热循环载荷条件下的应力应变分布进行了分析,计算其热疲劳寿命,分析焊点材料、焊点高度和焊点最大径向尺寸对叠层焊点热疲劳寿命的影响.结果表明,与单层焊点相比,焊点叠加方式能有效提高焊点热疲劳寿命;采用有铅焊料Sn62Pb36Ag2和Sn63Pb37的叠层焊点比采用无铅焊料Sn-3.5Ag和SAC305的叠层焊点热疲劳寿命高;叠层焊点的高度由0.50 mm增加到0.80 mm时,焊点的热疲劳寿命随其高度的增加而增加;叠层焊点的最大径向尺寸由0.30 mm增加到0.45 mm时,焊点的热疲劳寿命随焊点的最大径向尺寸增加而减小. 相似文献
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为了提升车身疲劳分析的效率,对车身动态疲劳的分析方法进行研究。以某车型TB车身为例,建立车身有限元模型,通过整车多体模型的虚拟试验场(Virtual Proving Ground,VPG)仿真,得到车身上各接附点的力/力矩作为计算的载荷输入。在此基础上,分别用时域法和频域法对某车型进行动态疲劳分析。以时域法分析为基准,从计算精度和计算效率两方面对不同分析方法进行对比,结果表明:两种方法分析得到的热点区域分布基本一致,考察的单元中,78.0%的单元损伤值对比在0.5~2.0之间,在可接受范围内;计算效率上,频域法分析显著提升了82%,验证了频域法在车身疲劳计算中的可行性。 相似文献
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焊点的疲劳性能是决定车身安全性和可靠性的重要因素. 对不同强度的DP780,DP980和DP1180双相钢焊点进行了检验,在疲劳试验机上进行了拉剪疲劳试验,获得了焊点的疲劳寿命曲线,分析了焊点显微组织、硬度与疲劳性能的关系. 并对焊点的疲劳失效进行了分析. 结果表明:母材性能对其焊点的疲劳性能有较大影响. 母材强度越高即马氏体含量越多,其疲劳性能越优异,三种材料的失效模式均是沿着焊点圆周断裂,裂纹在熔核与母材交界的热影响区萌生,且先贯穿板厚,贯穿板厚的裂纹作为二次裂纹源向板宽方向扩展直至断裂. 相似文献
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《铸造技术》2018,(12)
为了获得疲劳性能较好的波纹板组件,采用印记面法建立焊点模型,通过模拟仿真计算不同直径和间距下点焊连接的波纹板组件等效应力,并采用二因素无重复试验方差分析法研究了焊点直径及间距对波纹板组件受力情况的影响。结果表明,总体上焊点水平间距及直径对波纹板组件的等效应力无显著影响。在焊点水平间距为70 mm时,波纹板组件的等效应力随焊点直径增加而变化明显,且疲劳寿命随焊点直径的增大表现出明显提高。综合考虑波纹板组件的疲劳寿命及性价比,较优的焊点结构参数为焊点直径5 mm,焊点排列距U型板边缘左右边距10 mm,上下边距4 mm,且焊点间水平间距70 mm;此时波纹板组件疲劳寿命仿真结果为3.17×10~6次,物理试验下实际疲劳寿命超过2.00×10~7次,满足工况要求。 相似文献
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表面组装焊点内部应力—应变场的数值模拟(Ⅱ):焊点失效 … 总被引:5,自引:1,他引:4
温度循环载荷可以在点界面处形成足以导致空洞损伤发生的高应力三轴度。针对温度循环载荷下软钎焊点点界面定洞损伤的失效行为特点,结合焊点内部应力-应变场分布特征及其温度历史相关性,提出了相对损伤应力这一概念,并以此作为温度循环载荷下软钎焊焊点失效的主控力学因素。分析了温度历史不同阶段对焊点失效行为的影响,结果表明高温保温阶段焊点内部最发生空洞损伤。 相似文献
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采用AlSi5铝合金焊丝,冷金属过渡方法对汽车车身用6061铝合金进行了搭接点塞焊试验,研究了送丝速度、铝板孔直径、点塞焊时间对点塞焊接头焊点直径、焊核直径和拉伸载荷的影响.结果表明,送丝速度主要影响焊点直径的大小,点塞焊时间和铝板孔直径主要影响焊核直径和拉伸载荷.接头拉伸载荷主要取决于焊核直径的大小,焊核直径越大,拉伸载荷越大,与焊点直径关系不大.接头为典型的熔焊接头,焊缝主要由α-Al固溶体和Al-Si共晶相组成,点塞焊接头断裂方式为撕裂型断裂. 相似文献
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将三种方法确定的热点应力作为控制应力,引入焊接接头的疲劳切口系数,由Taylor的临界距离理论得到该系数.通过讨论接头类型、焊缝局部尺寸、板厚以及热点应力的确定方式对疲劳切口系数的影响,揭示热点应力法进行焊接接头疲劳评定的影响因素.结果表明,腹板厚度与焊缝局部几何尺寸对疲劳切口系数的分散性影响较小,但主板厚度的效应明显,由疲劳切口系数得到的板厚效应预测与试验结果接近;以两种外推法为基础构成的热点应力法能明显减少疲劳数据的分散性及其对接头类型与载荷形式的依赖性. 相似文献
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S. Bozzi A.L. Helbert-Etter T. Baudin V. Klosek J.G. Kerbiguet B. Criqui 《Journal of Materials Processing Technology》2010,210(11):1429-1435
The influence of the tool rotational speed, the probe plunge depth and the shoulder penetration depth on weld microstructure and on the weld strength have been studied. The shear tests showed that the friction stir spot welds fail by nugget pullout. Three microstructural factors play a determinant role on the weld's strength: the size and location of the stir zone, and the unwelded interface tip slope. With increasing rotational speed, the shear strength increases because of the larger size of the stir zone. By changing the probe plunge depth the location of the stir zone can be controlled in order to maximize the bonded distance between the interface tip and the central hole left by the probe. The shoulder penetration depth must be sufficient to ensure a horizontal interface tip and therefore avoid fracture by the opening mode (mode I) during shear loading. 相似文献
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Hai-tao HU Yu-long LI Tao SUO Feng ZHAO Ying-gang MIAO Pu XUE Qiong DENG 《中国有色金属学会会刊》2014,24(5):1331-1336
Vibration tests were carried out on three types of stiffened aluminum plates with fully clamped boundaries under random base excitation. During the test, the response of the specimens was monitored using strain gauges. Based on the strain history, the accumulation of fatigue damage of the stiffened plates was estimated by means of the rainflow cycle counting technique and the Miner linear damage accumulation model in the time domain. Utilizing the change of natural frequencies, a nonlinear model was fitted for predicting the fatigue damage of plate and then the foregone failure criterion of 5% reduction in natural frequency is improved. The influence of section and spacing of the stiffeners on the vibration fatigue behavior of the aluminum plate was investigated. The results show that the fatigue life of aluminum plate increases with adding either T or L section riveted stiffeners. With the same cross-sectional area of stiffener, the T section stiffened plate shows longer fatigue life than L section stiffened plate. Meanwhile, the vibration fatigue life also shows great sensitivity to the spacing between the stiffeners. 相似文献
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The defect assessment in butt-welded joint of ASTM A36 steel plates and 7075-T7351 aluminum alloy plates containing transverse through thickness crack was analyzed using SINTAP procedure and FEA incorporating weld induced residual stresses. Weld induced longitudinal residual stress profile can be obtained through SINTAP procedure, FEA or experimental analysis. This residual stress profile can be fitted with the trapezoidal residual stress profile available in SINTAP. For three different cases, crack length and residual stress intensity factor (SIF) are calculated and its comparison with the results obtained through FEA is plotted with respect to crack length. The stress intensity factor for mechanical loading is also plotted in the same graph. Using this graphical plot, the total SIF, including residual stress and mechanical loading, can be calculated for any particular crack size. The total SIF can be compared with the fracture toughness of the material for damage tolerance analysis. Also a failure assessment diagram is drawn for welded 7075-T7351 aluminum alloy plates with different crack sizes for as-welded (only residual stress) and mechanical loading along with the existing weld induced residual stresses to show the safety level for a particular crack size and mechanical loading. 相似文献
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A CUMULATIVE FATIGUE DAMAGE RULE UNDER THE ALTERNATIVE OF CORROSION OR CYCLIC LOADING 总被引:2,自引:0,他引:2
W.X. Yao 《金属学报(英文版)》2007,20(1):65-71
Fatigue damage increases with the applied loading cycles in a cumulative manner and the material deteriorates with the corrosion time. A cumulative fatigue damage rule under the alternative of corrosion or cyclic loading was proposed. The specimens of aluminum alloy LY12-CZ soaked in corrosive liquid for different times were tested under the constant amplitude cyclic loading to obtain S-N curves. The test was carried out to verify the proposed cumulative fatigue damage rule under the different combinations among corrosion time, loading level, and the cycle numbers. It was shown that the predicted residual fatigue lives showed a good agreement with the experimental results and the proposed rule was simple and can be easily adopted. 相似文献
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对带有两个焊点的拉剪点焊试样进行了两级变幅疲劳加载,应力幅和平均应力均不相等.结果表明,两级变幅加载下存在应力次序效应.在低—高加载时存在"锻炼效应",线性累积损伤的值大于1;在高—低加载时存在"过载效应",高—低加载下的线性累积损伤值也大于1.在高—低加载方式下,高水平应力作用后,低水平应力剩余疲劳寿命大于按线性疲劳累积损伤法则所估算的剩余寿命,低应力作用下的剩余寿命甚至大于低应力单独作用下的全寿命.高—低加载下的线性累积损伤结果表明,焊点边缘更象是一个缺口. 相似文献