本文選題：細觀損傷力學(xué)　切入點：Gurson-Tvergaard-Needleman模型　出處：《東北石油大學(xué)》2015年碩士論文　論文類型：學(xué)位論文

【摘要】：韌性金屬是壓力容器和承壓設(shè)備的常用材料,細觀損傷機理認為微觀孔洞的形核、長大和聚合是金屬承載能力下降的主要原因。深入認識韌性金屬的細觀損傷機理對壓力容器和承壓設(shè)備的安全使用和事故的預(yù)防具有重要的現(xiàn)實意義。本文基于細觀損傷力學(xué)理論,依托黑龍江省自然科學(xué)基金《金屬構(gòu)件低周疲勞細觀損傷機理及聲發(fā)射評價方法研究》,以Q245和Q345為例,研究金屬在拉伸和低周疲勞條件下的微孔洞細觀損傷變量的變化規(guī)律,主要內(nèi)容如下:第一章介紹了課題研究背景、目的及意義,論述了國內(nèi)外研究和發(fā)展現(xiàn)狀,介紹了本文的研究路線和研究內(nèi)容;第二章介紹了幾種韌性金屬微孔洞損傷模型,并對GTN模型的理論方法、模型參數(shù)、細觀損傷變量進行了詳細的論述;第三章首先應(yīng)用有限元反向標(biāo)定法,結(jié)合Q245和Q345的拉伸實驗和數(shù)值模擬,以臨界孔洞擴張比VGC為評價標(biāo)準(zhǔn),選擇最適合GTN模型的損傷參數(shù),還分析了微孔洞形核的二相粒子的體積百分?jǐn)?shù)fN、孔洞形核的平均應(yīng)變εN和標(biāo)準(zhǔn)方差SN對VGC的影響情況。其次模擬了不同材料、不同初始孔洞體積百分?jǐn)?shù)、不同橫截面直徑缺口試件在拉伸條件下的孔洞體積百分?jǐn)?shù)f、孔洞形核體積百分?jǐn)?shù)fnucleation、孔洞長大體積百分?jǐn)?shù)fgrowth的變化規(guī)律,獲得了拉伸不同階段微孔洞的損傷情況,探討了韌性金屬的細觀損傷機理;第四章對低周疲勞條件下的不同材料、不同應(yīng)變幅缺口試件進行微孔洞細觀損傷變量模擬,分析微孔洞細觀損傷參量演化規(guī)律的變化。模擬結(jié)果表明,材料特性、初始孔洞體積百分?jǐn)?shù)、橫截面直徑和應(yīng)變幅都會對微孔洞細觀損傷變量產(chǎn)生影響,故細觀損傷變量不是常數(shù)。當(dāng)材料內(nèi)部存在初始孔洞時,材料內(nèi)部的微觀損傷是由初始孔洞、孔洞形核、孔洞長大共同引起的。
[Abstract]:Ductile metals are common materials used in pressure vessels and pressure equipment. Growth and polymerization are the main reasons for the decrease of metal bearing capacity. It is of great practical significance to understand the meso-damage mechanism of ductile metals for the safe use of pressure vessels and pressure equipment and the prevention of accidents. Meso-damage mechanics theory, Based on the Natural Science Foundation of Heilongjiang Province, "study on the mechanism of microdamage and acoustic emission evaluation of metal components under low cycle fatigue", taking Q245 and Q345 as examples, the variation law of microvoid damage variables of metal under tensile and low cycle fatigue conditions is studied. The main contents are as follows: in the first chapter, the background, purpose and significance of the research are introduced, the research and development situation at home and abroad are discussed, the research route and research contents are introduced, the second chapter introduces several damage models of ductile metal microvoids. The theoretical method, model parameters and mesoscopic damage variables of GTN model are discussed in detail. Chapter three applies the reverse calibration method of finite element method, combined with the tensile experiments and numerical simulation of Q245 and Q345. According to the critical void expansion ratio (VGC) as the evaluation criterion, the damage parameters that are most suitable for the GTN model are selected. The effects of the volume percent of the two-phase particles, the average strain 蔚 N and the standard variance SN of the two-phase particles on the VGC are also analyzed. Secondly, the effects of different materials and different initial pore volume percentages on the VGC are simulated. The variation of void volume percentage f, void nucleation percentage and pore growth volume percentage fgrowth of notched specimens with different cross section diameters under tensile conditions were obtained. The damage of microvoids in different stretching stages was obtained. The meso-damage mechanism of ductile metals is discussed. In Chapter 4th, the microvoid damage variables of different materials and different strain amplitude notched specimens under low cycle fatigue condition are simulated. The results of simulation show that the material characteristics, initial pore volume percentage, cross-section diameter and strain amplitude all have effects on the meso-damage variables of microvoids, and the results of the simulation show that the variation of micropore damage parameters is affected by the variation of micropore damage parameters, such as material characteristics, initial pore volume percentage, cross-section diameter and strain amplitude. The microscopic damage of the material is caused by the initial hole, the nucleation of the pore, and the growth of the pore when there is an initial hole in the material.
【學(xué)位授予單位】：東北石油大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TG115.5;TG113

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本文編號：1611200