基于应力场强法的缺口构件场强值算法

工程上缺口构件疲劳寿命预测是结构设计过程中不可缺少的内容,基于这一现状通过修正后的场强法来更为有效地解决此类问题非常重要。针对传统应力场强法存在的问题,在考虑其原始假设的基础上,提出一种可以在不同结构尺寸及载荷环境下计算缺口构件场强值的方法。相比于原场强法中疲劳破坏区内各点对峰值点疲劳破坏的贡献作用,新方法认为破坏区内各点对峰值处的疲劳破坏具有“阻碍作用”,并将其做了定量分析。新方法还对模型所用参数、权函数的作用形式以及疲劳破坏区的界定准则做了适当修正,弱化了场径取值对场强求解的影响,克服了传统场强法中场径定义的难题,使场强值具有了一个客观存在的精确解。另外,综合考虑缺口形貌及其附近应力的分布特征,优化了原场强法的积分形式,大大简化了场强值的求解过程。最后还应用修正后的场强法对缺口试样疲劳数据进行了计算,分析结果表明,新模型的寿命预测误差系数可保持在0.24以内,充分满足工程需求。提出的修正模型能保持高预测精度,计算过程很简洁,有很高的推广价值。

Field Stress Intensity Calculation of Notched Component Specimens based on Field Intensity Method

Considering the situation that fatigue life prediction of notched component is an indispensable part in the process of structural design in engineering, it is necessary to solve such problems more effectively by a revised stress field intensity approach. For the existing problems of traditional stress field intensity approach and considering its original assumption, a new model is developed to calculate the field stress intensity, which can take account of the effects of different structure size and load environment. Compared with the contribution of each site in the fatigue damage zone to the peak point in the original field strength method, the new method considers that each point outside the peak in the failure zone has an "impeding effect" on the fatigue damage at the peak and quantitatively analyzes the "impeding effect". The new method also makes a proper correction to parameters of the model, the function form of the weight function and the definition of the fatigue failure zone, and also weaken the influence of the field diameter on the field strength, which consequently makes it overcome the difficult definition of field size parameter in traditional stress field intensity approach and, correspondingly, the field strength have an objective existence of exact solutions. In addition, considering the characteristics of the stress distribution near the notch and its vicinity, the integral form of the original field strength method is improved, simplifying the calculation process of the field strength greatly. Finally, experimental data of notched specimens have been calculated by the revised stress field intensity approach and analysis results show that prediction error coefficient of the new model is within 0.24, which can fully meet the practical demand in engineering. The revised model in this paper has more concise calculation process, keeping high-precision in fatigue life prediction at the same time, and also has a high promotion value.