共查询到18条相似文献,搜索用时 312 毫秒
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在向无铅化过渡的过程中,封装材料与工艺改变所带来的最突出的问题之一就是无铅焊点的可靠性问题。由于焊点区非协调变形导致的热疲劳失效是电子封装焊点的主要失效形式。到目前为止,仍无公认的焊点寿命和可靠性的评价方法。本文采用统一型粘塑性本构模型描述SnAgCu焊点的变形行为,在对焊点可靠性分析的基础上采用基于能量的寿命模型进行焊点寿命预测;在有限元方面采用子模型的处理技术,并采用节点平均化以及体积平均化方法计算寿命模型相关参数。力图从理论方面和有限元处理技术方面改进以达到提高焊点寿命预测效率及预测精度的目的。 相似文献
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针对某涡扇发动机加力燃油分布器内有机材料聚酰亚胺薄膜过早失效的问题,基于聚酰亚胺薄膜的材料参数以及薄膜使用时的温度和波动幅值,通过在ANSYS软件中建立了聚酰亚胺薄膜有限元仿真模型,研究薄膜发生以断裂为主要形式的失效时,薄膜的Mises应力分布情况以及薄膜的薄弱区分布情况。基于概率断裂力学的疲劳寿命计算理论得到了不同可靠度下薄膜的疲劳寿命循环次数及其变化规律。结果表明:薄膜存在应力集中,且薄膜的应力集中部位与薄弱区均发生在薄膜夹持外沿;计算得到了不同可靠度下薄膜的疲劳寿命循环次数,且疲劳寿命循环次数随可靠度的提升而不断降低。 相似文献
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霍尔电流传感器的退化机理复杂,退化具有波动性,非线性等特征,对高可靠、长寿命的霍尔电流传感器准确进行寿命预测是一个难点。本研究通过对霍尔电流传感器进行加速退化试验,利用性能退化数据,预测了传感器的可靠性及寿命。首先分析了霍尔电流传感器工作原理和退化机理,确定将输出电流漂移作为其性能退化参数。然后由试验数据推导得到Wiener过程漂移参数和扩散参数的约束关系,结合阿伦尼乌斯模型推导得到漂移参数和扩散参数的加速模型。从而得到霍尔电流传感器在正常工作温度条件下的可靠度函数和可靠寿命。将结果与基于加速退化轨迹法的可靠性预测结果进行对比,验证了本方法的可行性。 相似文献
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本文针对某伺服机构控制器电路板采用故障物理方法进行失效分析,然后在不同温度应力下开展该电子产品温升试验和热仿真,之后基于Coffin-Manson模型进行产品焊点疲劳寿命仿真并求解各元器件寿命分布,最后构建竞争失效模型进行电路板寿命预计。通过温度应力试验得到了关键元器件温升值在(23~31)℃范围内,基于CRAFE热仿真得到了产品各元器件温度,应用Coffin-Manson模型得到了元器件寿命分布,运用竞争失效方法计算了产品失效概率函数,评估了产品工作10年的可靠度为0.94,在可靠度指标为0.9时其工作寿命为12.11年。本文基于温度应力试验和热仿真,通过进行故障物理分析和元器件竞争失效分析有效评估了电子产品工作寿命,对其他类似电子产品可靠性分析提供了一定参考。 相似文献
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阐述了高压油管疲劳破坏的原理及危害,建立高压油管焊接质量评价力学模型,通过有限元分析技术对其许用位移输入进行计算,并结合应变测量技术,利用电动振动台,对高压油管焊接处的疲劳特性进行了试验验证。结果表明,此高压油管焊接质量评价方法是可行的,有限元分析技术和应变测量技术的结合使用,保证了试验的安全性和结果准确性,此外,利用电动振动台进行疲劳耐久试验,操作方便简单,成本相对较低,具有通用性。 相似文献
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飞机机体结构的内力计算是其结构强度分析的重要技术手段之一。外翼壁板直接承受空气动力载荷并把它传递到机翼纵向和横向构件上。探讨有限元截面法在外翼壁板内力计算中的应用,从理论分析以及实际操作的角度,为壁板强度计算流程化设计提供一种工程化分析手段。 相似文献
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双锥形管接头角度参数对管路密封的影响分析 总被引:3,自引:0,他引:3
根据金属密封的基本条件,应用非线形有限元分析软件Msc.Marc,针对联接导管位置不同的两种双锥形管接头密封管路联接结构,计算分析双锥形管接头锥角和锥角差对管路密封性能的影响。计算结果表明,轴向预紧力随锥角或锥角差的增大而增大,密封系统承载内压能力随之下降。 相似文献
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A two-dimensional water-quality model for a winding and topographically complicated river 总被引:3,自引:0,他引:3
In this paper, a two-dimensional numerical calculation algorithm for water-quality modeling is presented. The algorithm is designed specifically for river systems with complicated geometric conditions. When velocity field data of the river are not available, the numerical calculation algorithm for the water-quality modeling can be used to project river-water quality by using a topographic map of the river course and a finite element method. The calculation results of the water-quality model can show the concentration fields of various pollutants. The water-quality model was applied to a case-study in the Hengyang City section of Xiangjiang River in Hunan Province, China. The river under consideration is winding and has an isle between two branches. In 1995, Chinese government secured a World Bank loan to conduct a Waterways Project in the study region. It was expected that construction works in the river section might affect water quality. Given that the project would change the hydrological regime of the river system and discharges, and so would affect water quality, there would be a need for model results that would predict the water-quality impacts of the Waterways Project. In particular, the study intended to apply the model to identify changes in river-water quality associated with the construction of Dayuandu navigation key project. It is hoped that the numerical calculation algorithm for the water-quality modeling presented in this paper can also be applied to other shallow rivers with similar topographical conditions. 相似文献
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随机振动试验加速因子的计算方法 总被引:3,自引:0,他引:3
在已知随机振动加速度功率谱密度的条件下通过建立失效物理模型的方法推导了在随机振动试验中计算加速因子常用的逆幂率模型;同时总结了其他计算随机载荷疲劳寿命的方法,说明了使用其他模型计算加速因子是可行的。 相似文献
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Guillermo Cabrera Miguel A. Marino 《Journal of the American Water Resources Association》1976,12(1):49-63
ABSTRACT. The response of stream-unconfined aquifer systems to localized recharge is investigated by means of a two-dimensional finite element model. A variational approach is used in conjunction with the finite element method to solve the ground water flow equation. Linear approximated triangular elements are used to calculate the hydraulic head distribution in the flow region. The Crank-Nicholson centered scheme of numerical integration is employed to approximate the time derivative in the flow equation. A computer program is developed to calculate the hydraulic head distribution in the flow region. Solutions provided by the finite element model should prove useful in the evaluation of quantitative and qualitative changes in aquifer systems due to natural or artificial recharge. In addition, they should prove useful in the study of irrigation and drainage problems. 相似文献
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Guillermo Cabrera Miguel A. Marino 《Journal of the American Water Resources Association》1976,12(2):317-335
ABSTRACT. Transient, two-dimensional solutions are developed which describe the movement and distribution of a conservative substance in a stream-aquifer system. The solutions are obtained by solving sequentially the groundwater flow and mass transport equations. A variational approach in conjunction with the finite element method is used to solve the groundwater flow equation. Galerkin's approach coupled with the finite element method is used to solve the mass transport equation. Linear approximated triangular elements and a centered scheme of numerical integration are employed to calculate the hydraulic head distribution and the concentration of solute in the flow region. The linear approximation used to define the concentration function within each element is not appropriate for cases involving steep concentration gradients. For such cases, higher order approximations are necessary to assure the continuity of gradients across interelemental boundaries. Numerical examples that illustrate the applicability of the model are presented. 相似文献