【摘要】：本文研究了計及相變的QP980鋼的動態(tài)本構(gòu)方程與動態(tài)斷裂。提出了一種應(yīng)變受控的拉伸Hopkinson試驗裝置(TSHB),取得了高應(yīng)變率拉伸下發(fā)生預(yù)設(shè)應(yīng)變的QP980鋼試件。對回收試件進行同步加速器X射線衍射(XRD)試驗,結(jié)果表明,QP980鋼在高應(yīng)變率拉伸下,殘余奧氏體的體積含量隨應(yīng)變的變化規(guī)律與準靜態(tài)拉伸下的變化規(guī)律幾乎一致。根據(jù)O-C馬氏體相變理論,結(jié)合XRD試驗分析結(jié)果,得到了高應(yīng)變率拉伸下QP980鋼的相變動力學(xué)方程。根據(jù)多相材料細觀力學(xué)理論,由各組成相的彈塑性變形行為,構(gòu)成計及相變的QP980鋼的準靜態(tài)本構(gòu)方程。假設(shè)應(yīng)變率與溫度效應(yīng)可分離,基于不同應(yīng)變率及不同溫度下的TSHB試驗,建立了計及相變的QP980鋼動態(tài)本構(gòu)方程。由所建本構(gòu)方程得出的應(yīng)力-應(yīng)變曲線與試驗曲線進行了對比,驗證了所建本構(gòu)方程的有效性。采用高速攝影技術(shù)記錄了QP980鋼板條試件在TSHB試驗中的頸縮與斷裂,基于Batra和Wei的失穩(wěn)判據(jù)以及所建立的動態(tài)本構(gòu)方程,計算了QP980鋼板條試件在TSHB試驗中的非局部頸縮應(yīng)變,并與測試結(jié)果進行了對比。通過進行不同溫度、不同應(yīng)變率下的拉伸試驗,研究了QP980鋼板條試件的斷裂應(yīng)變與應(yīng)變率以及溫度的依賴關(guān)系。通過對試件斷裂區(qū)域的掃描電鏡(SEM)觀測,揭示了QP980鋼在變形過程中的微空穴不同的演化機制。
[Abstract]:The dynamic constitutive equation and dynamic fracture of QP980 steel with phase transformation are studied in this paper. In this paper, a strain controlled tensile Hopkinson test device, (TSHB), has been developed to obtain QP980 steel specimens with preset strain under high strain rate tension. The results of synchrotron X-ray diffraction (XRD) test show that the volume content of residual austenite varies with strain in QP980 steel at high strain rate, which is almost the same as that under quasi-static tension. Based on O-C martensitic transformation theory and XRD test results, the transformation kinetics equation of QP980 steel under high strain rate tension is obtained. According to the mesomechanical theory of multiphase materials, the quasi-static constitutive equation of QP980 steel with phase transformation is constructed by the elastoplastic deformation behavior of each component phase. Assuming that the strain rate and temperature effect can be separated, the dynamic constitutive equation of QP980 steel with phase transformation is established on the basis of TSHB tests at different strain rates and different temperatures. The stress-strain curve derived from the established constitutive equation is compared with the experimental curve, and the validity of the established constitutive equation is verified. The necking and fracture of QP980 steel strip specimen in TSHB test were recorded by high-speed photography. Based on the instability criterion of Batra and Wei and the dynamic constitutive equation established, the non-local necking strain of QP980 steel strip specimen in TSHB test was calculated. The results are compared with the test results. The dependence of fracture strain on strain rate and temperature of QP980 steel strip specimens were studied by tensile tests at different temperatures and different strain rates. The different evolution mechanisms of microvoids in QP980 steel during deformation were revealed by scanning electron microscope (SEM) observation of the fracture zone of the specimens.
【學(xué)位授予單位】：寧波大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TG142.1

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