【摘要】：鋼結(jié)構(gòu)在強烈地震作用下將會發(fā)生超低周疲勞斷裂,這類斷裂現(xiàn)象通常伴隨明顯的塑性變形,具有延性斷裂的特征。近年來對于金屬材料的延性斷裂研究已經(jīng)由傳統(tǒng)斷裂力學(xué)理論逐漸轉(zhuǎn)變?yōu)榛谖⒂^斷裂機理的局部斷裂理論,很多學(xué)者提出了適用于不同應(yīng)力狀態(tài)的局部斷裂預(yù)測模型,并驗證了預(yù)測結(jié)果的準(zhǔn)確性。但是,這些模型主要針對于高應(yīng)力三軸度的疲勞斷裂以及低應(yīng)力三軸度的拉伸斷裂,在低應(yīng)力三軸度水平下的超低周疲勞斷裂范疇還沒有進行充分的研究。因此,本文設(shè)計了對應(yīng)高、中、低三種應(yīng)力三軸度狀態(tài)的試件,并進行單向拉伸試驗和超低周疲勞試驗,在前人研究的基礎(chǔ)上,提出了適用于全范圍應(yīng)力狀態(tài)的局部斷裂預(yù)測模型。本文內(nèi)容包含以下四個方面:(1)設(shè)計了針對高應(yīng)力三軸度軸對稱應(yīng)力狀態(tài)的圓棒試件、高應(yīng)力三軸度平面應(yīng)變狀態(tài)的平板試件、以及低應(yīng)力三軸度剪切應(yīng)力狀態(tài)的剪切試件,并設(shè)計了單向拉伸以及增幅、等幅、變幅疲勞加載共四種加載制度。(2)完成了 11個單向拉伸試驗和25個超低周疲勞試驗。根據(jù)光滑圓棒試件的試驗數(shù)據(jù),分別校準(zhǔn)了用于模擬單向拉伸試驗的材性數(shù)據(jù),以及超低周疲勞試驗的混合強化模型參數(shù)。(3)依據(jù)有限元模擬數(shù)據(jù),校準(zhǔn)了 VGM模型、SWDM模型以及LOU模型的各項系數(shù),編寫了 ABAQUS有限元軟件的UVARM用戶子程序,計算得到各模型的預(yù)測結(jié)果并進行對比分析。(4)以LOU模型為理論基礎(chǔ)建立用于超低周疲勞試驗的CLOU延性斷裂預(yù)測模型,編寫UVARM子程序。利用23個不同試件類型以及不同加載制度的疲勞試件校準(zhǔn)CLOU模型、CVGM模型以及SWDM模型的系數(shù),驗證三種模型的預(yù)測結(jié)果準(zhǔn)確性,分析疲勞試驗的損傷積累過程,得到能夠應(yīng)用于全范圍應(yīng)力狀態(tài)的斷裂預(yù)測模型,并提供適用于Q460C鋼材的三種斷裂模型的材料系數(shù)。
[Abstract]:Ultra-low cycle fatigue fracture will occur in steel structure under strong earthquake. This kind of fracture is usually accompanied by obvious plastic deformation and has the characteristics of ductile fracture. In recent years, the research on ductile fracture of metallic materials has gradually changed from traditional fracture mechanics theory to local fracture theory based on micro fracture mechanism. Many scholars have proposed a local fracture prediction model suitable for different stress states. The accuracy of the prediction results is verified. However, these models are mainly aimed at the fatigue fracture of high stress triaxiality and the tensile fracture of low stress triaxiality, and the category of ultra-low cycle fatigue fracture at low stress triaxiality level has not been fully studied. Therefore, in this paper, the specimens corresponding to high, middle and low triaxial stress are designed, and the uniaxial tensile tests and ultra-low cycle fatigue tests are carried out. A local fracture prediction model suitable for full range stress state is proposed. The contents of this paper include the following four aspects: (1) the circular bar specimen with high stress triaxiality axisymmetric stress state, the plate specimen with high stress triaxiality plane strain state and the shear specimen with low stress triaxiality shear stress state are designed. Four loading systems were designed for uniaxial tension and fatigue loading with equal amplitude and variable amplitude. (2) 11 uniaxial tensile tests and 25 ultra-low cycle fatigue tests were completed. According to the test data of smooth round bar, the material property data used to simulate uniaxial tensile test and the mixed strengthening model parameters of ultra-low cycle fatigue test were calibrated respectively. (3) according to the finite element simulation data, The coefficients of VGM model and LOU model are calibrated, and the UVARM user subprogram of ABAQUS finite element software is written. The prediction results of each model are calculated and compared. (4) based on the LOU model, the CLOU ductile fracture prediction model for ultra-low cycle fatigue test is established and the UVARM subroutine is compiled. Using 23 fatigue specimens with different specimen types and different loading systems to calibrate the coefficients of the CLOU model and the SWDM model, the accuracy of the prediction results of the three models is verified, and the damage accumulation process of the fatigue test is analyzed. A fracture prediction model which can be applied to the full range stress state is obtained and the material coefficients of three fracture models suitable for Q460C steel are provided.
【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】：2017
【分類號】：TG142.1

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本文編號：2242437