【摘要】：鋼結(jié)構(gòu)構(gòu)件的韌性破壞是其主要破壞形式,而考慮微觀損傷的本構(gòu)模型能夠從微觀層面形象的解釋延性金屬材料的韌性破壞,科學(xué)、合理地揭示鋼材非線性性能的真實(shí)發(fā)展過程。目前應(yīng)用最為廣泛的微觀損傷模型是GTN(Gurson-Tvergaard-Needleman)模型,然而,該模型尚未推廣于建筑領(lǐng)域中。因此,本文將微觀GTN損傷模型引入建筑鋼材力學(xué)性能研究中。 基于微觀GTN損傷本構(gòu)理論,調(diào)制了有限元軟件ABAQUS中的用戶材料子程序UMAT,通過單元算例,驗(yàn)證了程序有效性和正確性,并系統(tǒng)分析了損傷參數(shù)對預(yù)測結(jié)果的影響。 取材自Q345低合金鋼和奧氏體304不銹鋼熱軋無縫鋼管,加工光滑和缺口試件,進(jìn)行了標(biāo)準(zhǔn)和缺口試件單向拉伸破壞試驗(yàn),分別識別了兩種鋼材的材料參數(shù)和損傷參數(shù),并與數(shù)值模擬結(jié)果進(jìn)行對比,發(fā)現(xiàn)GTN損傷模型能夠準(zhǔn)確預(yù)測Q345低合金鋼試件的斷裂點(diǎn),而采用Ramberg-Osgood曲線模擬鋼材應(yīng)力應(yīng)變關(guān)系構(gòu)筑GTN損傷模型,無法準(zhǔn)確模擬奧氏體304不銹鋼的力學(xué)行為。 對Q345低合金鋼和奧氏體304不銹鋼光滑和缺口試件進(jìn)行低周往復(fù)加載試驗(yàn),得到其滯回和骨架曲線,結(jié)果表明鋼材在單調(diào)與循環(huán)荷載下的力學(xué)性能有很大的區(qū)別。 此外,通過電鏡掃描試驗(yàn),觀察兩種鋼材試件在單調(diào)和循環(huán)荷載下的斷口微觀形態(tài),探討Q345低合金鋼和奧氏體304不銹鋼斷口微觀形態(tài)的區(qū)別,以及同一鋼材在不同加載方式下的破壞特征,論證其是否與GTN本構(gòu)模型的微觀表述符合,為后續(xù)研究奠定基礎(chǔ)。
[Abstract]:The ductile failure of steel structural members is the main failure form, and the constitutive model considering microscopic damage can explain the ductile damage of ductile metal materials vividly from the microscopic level. It is reasonable to reveal the true development process of the nonlinear properties of steel. The most widely used microscopic damage model is GTN (Gurson-Tvergaard-Needleman) model. However, the model has not been extended to the field of architecture. Therefore, the microscopic GTN damage model is introduced into the study of mechanical properties of building steel. Based on the microscopic GTN damage constitutive theory, the user material subroutine UMAT, in the finite element software ABAQUS is modulated. The validity and correctness of the program are verified by a numerical example, and the influence of damage parameters on the prediction results is systematically analyzed. After hot rolled seamless steel tubes made from Q345 low alloy steel and austenitic 304 stainless steel, smooth and notched specimens were processed. Uniaxial tensile failure tests of standard and notched specimens were carried out. The material parameters and damage parameters of two kinds of steels were identified, respectively. Compared with the numerical simulation results, it is found that the GTN damage model can accurately predict the fracture point of Q345 low alloy steel specimen, while the Ramberg-Osgood curve is used to simulate the stress-strain relationship of steel to construct the GTN damage model. The mechanical behavior of austenitic 304 stainless steel cannot be accurately simulated. The hysteresis and skeleton curves of Q345 low alloy steel and austenitic 304 stainless steel smooth and notched specimens under low cycle reciprocating loading are obtained. The results show that the mechanical properties of steel under monotonic and cyclic loads are quite different. In addition, the fracture morphology of two kinds of steel specimens under monotonic and cyclic loading was observed by scanning electron microscope test, and the difference between the fracture morphology of Q345 low alloy steel and austenitic 304 stainless steel was discussed. The failure characteristics of the same steel under different loading modes are proved to be consistent with the microscopic expression of the GTN constitutive model, which lays a foundation for further research.
【學(xué)位授予單位】：北京交通大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2013
【分類號】：TU511.3

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