基于Z′参数的高强铝合金稳态蠕变速率可靠性研究

Reliability Analysis on Steady Creep Rate of High Strength Aluminum Alloy Based on Z′-parameter

建立了基于速率温度参数模型的新型高强铝合金Z′参数表达式及稳态蠕变速率-可靠度预测方法,Z′参数表征稳态蠕变速率数据偏离速率温度参数模型主曲线的程度。结合实测数据,研究了Z′参数的统计分布规律。基于Z′参数,分别得出新型高强铝合金实验应力-速率温度参数-可靠度曲线和温度-许用应力-可靠度曲线。结果显示,新型高强铝合金Z′参数满足正态分布规律。稳态蠕变速率预测上限随可靠度的增加而升高。外推至稳态蠕变速率上限10-7 h-1时,新型高强铝合金在50、80℃下的许用应力(可靠度99.7%)分别为470.0、294.5 MPa。与传统安全系数法相比,基于Z′参数的预测结果更合理。

A Z′-parameter method based on rate-temperature parameter(RTP) was proposed to be used in reliability analysis of the steady creep rate of new high strength aluminum alloy, where Z′-parameter refers to the deviation of creep property from master curve. The steady rate data of creep experiments were studied to evaluate the distribution of Z′-parameter. Stress-RTP-reliability curves and temperature-allowable stress-reliability curves were proposed for new high strength aluminum alloy based on Z′-parameter in this paper. The results demonstrate that the scatter of Z′-parameter for new high strength aluminum alloy is supported by normal distribution. As the reliability increases, the predicted upper limit of steady creep rate raises. The permissible stresses in service temperature of 50 ℃ and 80 ℃ are limited to be 470.0 MPa and 294.5 MPa, when service condition is chosen to assess 99.7% reliability prediction up to 10-7 h-1. In comparison to traditional safety factor method, Z′-parameter method has achieved reasonable creep rate prediction with reliability of new high strength aluminum alloy by considering the scatter of creep rate data.