航空学报 > 2022, Vol. 43 Issue (3): 225013-225013   doi: 10.7527/S1000-6893.2021.25013

基于双峰对数正态分布模型的DED-TA15钛合金DFR值估计方法

王天帅, 贺小帆, 王金宇, 李玉海   

  1. 北京航空航天大学 航空科学与工程学院, 北京 100083
  • 收稿日期:2020-11-25 修回日期:2021-03-18 出版日期:2022-03-15 发布日期:2021-04-08
  • 通讯作者: 贺小帆 E-mail:xfhe@buaa.edu.cn
  • 基金资助:
    国家重点研发计划(2017YFB1104003);国家自然科学基金(11772027);航空科学基金(201909051002)

Estimation method for DFR value of DED-TA15 titanium alloy based on bimodal lognormal distribution

WANG Tianshuai, HE Xiaofan, WANG Jinyu, LI Yuhai   

  1. School of Aeronautic Science and Engineering, Beihang University, Beijing 100083, China
  • Received:2020-11-25 Revised:2021-03-18 Online:2022-03-15 Published:2021-04-08
  • Supported by:
    National Key Research and Development Program of China (2017YFB1104003); National Natural Science Foundation of China (11772027); Aeronautical Science Foundation of China (201909051002)

摘要: 有效评价增材制造金属材料的疲劳强度,是增材制造技术应用于可重复使用飞行器主承力结构的关键。以DED-TA15钛合金为研究对象,基于3种应力水平下标准圆棒试件的成组疲劳试验结果,建立了描述DED-TA15钛合金疲劳寿命分布的双峰对数正态分布模型,采用EM算法,建立了双峰对数正态分布的参数估计方法;采用Bootstrap方法给出了指定置信度和可靠度要求的疲劳寿命计算方法。在军机DFR方法的基础上,给出了适用于DED-TA15钛合金的DFR值计算方法。与传统单峰对数正态分布相比,双峰对数正态分布更精确的描述了疲劳寿命分布,提高了高可靠度和高置信度要求下的疲劳寿命,DFR值也有所提高。该方法降低了因描述模型不精确导致的对设计许用应力的过度限制,有效的提高DED-TA15钛合金的使用潜力。

关键词: DFR方法, 激光沉积成形, 双峰对数正态分布, 增材制造, 疲劳可靠性

Abstract: Fatigue strength evaluation of Additive Manufacturing (AM) metal materials is a prerequisite for the application of AM materials to the main bearing structure of aircraft.Taking DED-TA15 titanium alloy as the research object, we conduct a fatigue test of standard cylindrical specimens at three stress levels and obtain the fatigue life data.A bimodal lognormal distribution model is built to describe the fatigue life distribution of DED-TA15 titanium alloy based on the test results.The EM algorithm is used to establish the parameter estimation method of the bimodal lognormal distribution, and the Bootstrap method is adopted to calculate the fatigue life with the specified confidence level and reliability requirements.Compared with the traditional lognormal distribution model, the bimodal lognormal distribution can describe the fatigue life of DED-TA15 titanium alloy more accurately.The fatigue life at the high reliability and high confidence level, as well as the Detail Fatigue Rating (DFR) value, is improved.This method reduces the excessive limitation of allowable design stress and effectively increases the load potential of DED-TA15 titanium alloy.

Key words: detail fatigue rating (DFR) method, directed energy deposition, bimodal lognormal distribution, additive manufacturing (AM), fatigue reliability

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