(南京航空航天大學機電學院，南京 210016)
摘 要: 對Ti6Al4V合金在不同溫度(650、700和750℃)、初始應(yīng)力(100和150MPa)和預(yù)應(yīng)變(3.97%和15.87%)條件下進行多組應(yīng)力松弛試驗；研究Ti6Al4V合金高溫下的應(yīng)力松弛行為以及影響因素。利用應(yīng)力松弛的試驗數(shù)據(jù)推導出高溫短時蠕變應(yīng)變速率與應(yīng)力的關(guān)系，對蠕變應(yīng)變速率-應(yīng)力曲線進行擬合，得到Ti6Al4V合金的高溫短時蠕變本構(gòu)方程。將高溫短時蠕變本構(gòu)關(guān)系代入有限元軟件ABAQUS中對Ti6Al4V合金的應(yīng)力松弛行為進行模擬。結(jié)果表明：Ti6Al4V合金的應(yīng)力松弛可以分為兩個階段：第一個階段應(yīng)力松弛速率很快，剩余應(yīng)力急劇降低，該過程時間為應(yīng)力松弛的前250s；第二個階段應(yīng)力松弛較為緩慢，經(jīng)過2000s后剩余應(yīng)力趨向于某一極限值，即應(yīng)力松弛極限。溫度對Ti6Al4V合金應(yīng)力松弛的影響顯著，應(yīng)力松弛隨溫度的升高而加快，且溫度越高，應(yīng)力松弛極限越小。初始應(yīng)力和預(yù)應(yīng)變越大，應(yīng)力松弛極限越大，但是兩者對應(yīng)力松弛行為的影響不大。模擬結(jié)果與試驗測得的應(yīng)力松弛曲線具有很高的吻合度，驗證了高溫短時蠕變本構(gòu)關(guān)系的可靠性。
關(guān)鍵字: Ti6Al4V合金；應(yīng)力松弛行為；短時蠕變；本構(gòu)方程
（College of Mechanical and Electrical Engineering,
Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China）
Abstract:The stress relaxation tests of Ti6Al4V alloy were conducted at different temperatures (650, 700 and 750℃), initial stresses (100 and 150MPa), pre-strains (3.97% and 15.87%). The stress relaxation behavior of Ti6Al4V alloy and influence of different factors at high temperature were discussed. Based on the experimental data of stress relaxation, the relationship between short-term creep strain rate and stress was deduced. Then, the short-term creep constitutive equation of Ti6Al4V alloy at high temperature was obtained by fitting the creep strain rate-stress curves. The short-term creep constitutive relation at high temperature was used to simulate the stress relaxation behavior of Ti6Al4V alloy by integrating the relation into finite element software ABAQUS. The results show that the stress relaxation of Ti6Al4V alloy can be divided into two stages: At the first stage, the stress relaxation rate is very fast and the residual stress reduces sharply, which lasts 250s, While at the second stage, the stress relaxation rate is relatively slow and the residual stress tends to the limit after 2000 s. Temperature has significant influence on the stress relaxation of Ti6Al4V alloy. The rise of temperature can accelerate the stress relaxation rate, and the higher the temperature is, the smaller the stress relaxation limit is. Stress relaxation limit increases with the increase of initial stress and pre-strain which have small effect on the stress relaxation behavior. The simulated results and the experimental stress relaxation curves are with a high degree of similarity, which validates the dependability of the short-term creep constitutive relation at high temperature.
Key words: Ti6Al4V alloy; stress relaxation behavior; short-term creep; constitutive equation
