TWIP鋼屈服準則的應用與變形抗力研究
發(fā)布時間：2019-01-28 09:26
【摘要】：孿晶誘發(fā)塑性變形鋼,又稱TWIP鋼,是近些年來所發(fā)展起來的新型汽車用鋼。在力學性能上,有著很高的強塑積,能夠在保證強度的情況下,有著更高的塑性,同時,其對沖擊功的吸收能力更優(yōu)于傳統(tǒng)鋼種。從TWIP鋼塑性變形階段的本構(gòu)關(guān)系和變形抗力角度出發(fā),對鋼種的各向異性程度、TWIP效應機理、屈服準則應用以及整個變形階段的應變硬化行為進行了研究。通過單向拉伸實驗和XRD觀察,得到實驗鋼為室溫奧氏體鋼,在0°、45°和90°方向上的屈服應力差異很大,其中在90°方向和45°方向上,屈服強度相差約為165MPa,厚向各向異性指數(shù)r值均大于1,存在有明顯的各向異性。通過不同變形量的單向拉伸實驗,然后分別用金相顯微鏡和透射顯微鏡對縱向截面的微觀組織結(jié)構(gòu)進行觀察,發(fā)現(xiàn)該鋼種在形變時形成很大數(shù)量的形變孿晶,并對頸縮的出現(xiàn)起到了顯著的推遲作用,從而證明該鋼種在塑性形變中發(fā)生了較為顯著的TWIP效應。通過與軋制方向成不同角度的單向拉伸實驗,以及在自主設(shè)計制造的用于實現(xiàn)等比例雙向拉伸的簡易機械式實驗裝置上所做的等雙拉實驗,分別對Hill48和Barlat89兩種屈服函數(shù)中的未知參數(shù)進行了計算,計算方法有變形各向異性r值求解法和應力各向異性求解法。將所求結(jié)果分別對TWIP鋼的r值、屈服軌跡和等雙拉應力應變曲線進行了預測,根據(jù)預測結(jié)果的誤差分析,可以得到,由各向異性系數(shù)r值計算屈服函數(shù)中未知參數(shù)所得的Hill48屈服函數(shù)能夠更加準確的描述TWIP鋼的屈服行為。通過對室溫下單向拉伸應力—應變曲線做相應的數(shù)據(jù)處理,獲得TWIP鋼的應變硬化率—應變曲線,結(jié)果表明,TWIP鋼在塑性變形階段,其應變硬化行為分為三個階段,也即隨著應變的逐漸增加,應變硬化率呈現(xiàn)為“迅速下降—上升—再下降”的整體趨勢,而在金相顯微鏡下和透射電子顯微鏡下的觀察表明,這是試驗鋼在塑性階段的變形中,形變孿晶和位錯各自及相互之間的交互作用共同影響的結(jié)果。
[Abstract]:Twin induced plastic deformation steel, also known as TWIP steel, is a new type of automobile steel developed in recent years. In terms of mechanical properties, it has a high strong plastic product, which can ensure the strength of the steel and has a higher plasticity. At the same time, its absorptive capacity of impact work is better than that of the traditional steel. The anisotropy of TWIP steel, the mechanism of TWIP effect, the application of yield criterion and the strain hardening behavior of the whole deformation stage were studied from the point of view of constitutive relation and deformation resistance of TWIP steel during plastic deformation. Through uniaxial tensile test and XRD observation, it is found that the experimental steel is austenitic steel at room temperature. The yield stress in 0 擄, 45 擄and 90 擄directions is very different, and the difference of yield strength in 90 擄direction and 45 擄direction is about 165 MPA. The thickness anisotropy exponent r is greater than 1, and there is obvious anisotropy. The microstructure of the longitudinal section was observed by means of metallographic microscope and transmission microscope. It was found that a large number of deformation twins were formed when the steel was deformed. It is proved that the TWIP effect is significant in plastic deformation of the steel. Through the uniaxial tensile experiment with different angle to the rolling direction, and on the simple mechanical experiment device designed and manufactured by ourselves to realize the equal proportion biaxial tension, the equal double pull experiment was done. The unknown parameters in Hill48 and Barlat89 yield functions are calculated respectively. The calculation methods include deformation anisotropy r value method and stress anisotropy method. The values of r, yield trajectory and iso-double tensile stress-strain curves of TWIP steel are predicted by the calculated results. According to the error analysis of the prediction results, the results can be obtained. The Hill48 yield function calculated from the anisotropic coefficient r value of the yield function can more accurately describe the yield behavior of TWIP steel. The strain-hardening rate-strain curve of TWIP steel was obtained by processing the stress-strain curve of uniaxial tension at room temperature. The results show that the strain hardening behavior of TWIP steel is divided into three stages during plastic deformation. That is to say, with the increasing of strain, the strain hardening rate shows the whole trend of "rapid descending, rising and falling", and the observation under metallographic microscope and transmission electron microscope shows that this is the deformation of the test steel in the plastic stage. The results of the interaction between deformation twins and dislocations.
【學位授予單位】：華北理工大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TG142.1
[Abstract]:Twin induced plastic deformation steel, also known as TWIP steel, is a new type of automobile steel developed in recent years. In terms of mechanical properties, it has a high strong plastic product, which can ensure the strength of the steel and has a higher plasticity. At the same time, its absorptive capacity of impact work is better than that of the traditional steel. The anisotropy of TWIP steel, the mechanism of TWIP effect, the application of yield criterion and the strain hardening behavior of the whole deformation stage were studied from the point of view of constitutive relation and deformation resistance of TWIP steel during plastic deformation. Through uniaxial tensile test and XRD observation, it is found that the experimental steel is austenitic steel at room temperature. The yield stress in 0 擄, 45 擄and 90 擄directions is very different, and the difference of yield strength in 90 擄direction and 45 擄direction is about 165 MPA. The thickness anisotropy exponent r is greater than 1, and there is obvious anisotropy. The microstructure of the longitudinal section was observed by means of metallographic microscope and transmission microscope. It was found that a large number of deformation twins were formed when the steel was deformed. It is proved that the TWIP effect is significant in plastic deformation of the steel. Through the uniaxial tensile experiment with different angle to the rolling direction, and on the simple mechanical experiment device designed and manufactured by ourselves to realize the equal proportion biaxial tension, the equal double pull experiment was done. The unknown parameters in Hill48 and Barlat89 yield functions are calculated respectively. The calculation methods include deformation anisotropy r value method and stress anisotropy method. The values of r, yield trajectory and iso-double tensile stress-strain curves of TWIP steel are predicted by the calculated results. According to the error analysis of the prediction results, the results can be obtained. The Hill48 yield function calculated from the anisotropic coefficient r value of the yield function can more accurately describe the yield behavior of TWIP steel. The strain-hardening rate-strain curve of TWIP steel was obtained by processing the stress-strain curve of uniaxial tension at room temperature. The results show that the strain hardening behavior of TWIP steel is divided into three stages during plastic deformation. That is to say, with the increasing of strain, the strain hardening rate shows the whole trend of "rapid descending, rising and falling", and the observation under metallographic microscope and transmission electron microscope shows that this is the deformation of the test steel in the plastic stage. The results of the interaction between deformation twins and dislocations.
【學位授予單位】：華北理工大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TG142.1
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