小冲杆和压入测试技术获取材料真应力-应变曲线的对比研究

A comparative study on determination of true stress-strain curves using small punch tests and indentation tests

小冲杆和压入测试技术是测量在役设备以及涂层、焊缝等局部区域力学性能的有效途径。对两种测试方法获取材料真应力-应变曲线的准确性和抗干扰能力进行了对比研究。首先提出了基于材料数据库通过小冲杆或压入的载荷-位移曲线反求材料真应力-应变数据的统一方法;然后通过虚拟材料和2.25Cr1Mo钢对数据库方法的准确性进行了验证;最后对小冲杆和压入测试技术反求真应力-应变曲线的抗干扰能力进行了比较分析。结果表明,通过小冲杆法或压入法的载荷-位移曲线均能获得准确的材料真应力-应变数据,但是当载荷-位移曲线与材料响应存在偏差时,两种测试方法的抗干扰能力不同,当载荷-位移曲线的偏差为1%时,通过小冲杆曲线和压入曲线反求的真应力-应变数据误差分别为2.5%和8.7%;当载荷-位移曲线的偏差为0.5%时,通过小冲杆法反求的真应力-应变数据误差仅为1.2%,但是压入法求得的结果误差仍高达4.8%;相同偏差下,小冲杆法比压入法具有更好的抗干扰能力,增加压入深度时,压入法的抗干扰能力有所提高。

Small punch tests and indentation tests are effective paths to measure the mechanical properties of in-service components and local regions such as welded joints.The accuracy and anti-interference ability of the true stress-strain curve of materials obtained by the two methods were comparatively researched.First,a unified method was proposed based on the materials database,which reversely obtains the material stress-strain data through the load-displacement curve of small punch or indenter.Then,the accuracy of the database methods was verified through the hypothetical material and 2.25Cr1Mo steel.Finally,the anti-interference ability of the true stress-strain curve reversely obtained through the small punch and indentation test technology was compared and analyzed.The results show that both small punch tests and indentation tests can acquire the true stress-strain data accurately through the load-displacement curve.However,the anti-interference abilities of the two test methods are different when there is a deviation between the load-displacement curve and response of the material,when the deviation of load-displacement curve is 1%,the error of the true stress-stain data reversely obtained through the small punch curve and indentation curve is 2.5%and 8.7%,respectively.When the deviation of load-displacement curve is 0.5%,the error of the true stress-strain data obtained by the small punch method is only 1.2%,whereas the error of the results obtained by indentation method still reaches high as 4.8%.The small punch method shows a better anti-interference ability than the indentation method.The anti-interference ability of the indentation method can be improved when increasing the indentation depth.