本文選題：疲勞裂紋擴(kuò)展 + 應(yīng)力比�。� 參考：《浙江工業(yè)大學(xué)》2016年博士論文

【摘要】：疲勞問(wèn)題一直以來(lái)都是工業(yè)上備受關(guān)注的問(wèn)題之一。金屬零部件和工程結(jié)構(gòu)疲勞斷裂不僅造成巨大的經(jīng)濟(jì)損失,甚至?xí)＜暗饺藛T的生命安全。研究材料的疲勞裂紋擴(kuò)展行為具有重大的工程實(shí)用價(jià)值和社會(huì)經(jīng)濟(jì)意義。疲勞易啟裂于零部件的表面,為了抑制表面裂紋的萌生和擴(kuò)展,通常對(duì)材料的表面進(jìn)行強(qiáng)化處理。噴丸是一種在工業(yè)生產(chǎn)中應(yīng)用極為廣泛的表面強(qiáng)化工藝,通過(guò)向金屬材料的表層注入殘余壓應(yīng)力并優(yōu)化其組織結(jié)構(gòu),顯著提高零部件的抗疲勞和抗應(yīng)力腐蝕等性能。近年來(lái),隨著有限元技術(shù)和電子計(jì)算機(jī)的飛速發(fā)展,通過(guò)數(shù)值模擬研究噴丸強(qiáng)化機(jī)制和優(yōu)化噴丸過(guò)程參數(shù),已成為當(dāng)前噴丸強(qiáng)化技術(shù)進(jìn)一步發(fā)展的要求和潮流。通過(guò)單丸噴丸模型研究模型參數(shù)(單元尺寸、摩擦系數(shù)、分析步長(zhǎng)和彈丸材料性質(zhì))對(duì)數(shù)值結(jié)果的影響。從受噴區(qū)域的動(dòng)態(tài)應(yīng)力演化和殘余應(yīng)力分布兩個(gè)方面評(píng)估對(duì)稱胞元模型預(yù)測(cè)的殘余應(yīng)力。根據(jù)對(duì)稱胞元模型的模擬方法,對(duì)預(yù)應(yīng)力噴丸強(qiáng)化過(guò)程進(jìn)行建模研究,發(fā)現(xiàn)隨著噴丸速度的增大,噴丸強(qiáng)化所致殘余壓應(yīng)力對(duì)預(yù)加拉應(yīng)力愈加敏感。根據(jù)真實(shí)的噴丸強(qiáng)化工藝和基于受噴表面凹坑分布的統(tǒng)計(jì)分析,提出隨機(jī)概率噴丸模型。利用該模型模擬二次噴丸強(qiáng)化過(guò)程,結(jié)果表明二次噴丸強(qiáng)化能夠有效強(qiáng)化靶材表層的殘余壓應(yīng)力并減小受噴表面粗糙度。基于激光沖擊波壓力的時(shí)空分布模型和能夠表征材料流動(dòng)應(yīng)力Arrhenius和non-Arrhenius特征的統(tǒng)一本構(gòu)模型,建立三維單點(diǎn)激光噴丸高導(dǎo)無(wú)氧(OFHC)銅的有限元模型。通過(guò)該模型定量研究激光功率密度和激光脈沖半高寬對(duì)噴丸強(qiáng)化效果的交互影響以及應(yīng)力波在靶材內(nèi)部的傳播特性。單點(diǎn)多次激光噴丸強(qiáng)化的殘余應(yīng)力趨于飽和,這主要與靶材的硬化歷史有關(guān)。雙面激光噴丸強(qiáng)化的殘余應(yīng)力對(duì)靶材的厚度十分敏感,這主要與雙面噴丸過(guò)程中沖擊波的相互作用有關(guān)。為了研究噴丸的組織結(jié)構(gòu)強(qiáng)化機(jī)制,采用位錯(cuò)密度演化模型定量預(yù)測(cè)噴丸強(qiáng)化過(guò)程中受噴區(qū)域細(xì)化的晶粒尺寸和增加的位錯(cuò)密度。在彈丸或激光束的沖擊載荷下,靶材表層的晶粒尺寸顯著減小,位錯(cuò)密度顯著增加,并且細(xì)化的晶粒尺寸和增加的位錯(cuò)密度隨著重復(fù)噴丸次數(shù)的增加而逐漸趨于飽和。此外,建立晶體塑性本構(gòu)模型,模擬單晶銅在沖擊載荷下的變形行為。采用非標(biāo)準(zhǔn)緊湊拉伸試樣對(duì)2024-T4鋁合金進(jìn)行常幅和變幅載荷下的疲勞裂紋擴(kuò)展試驗(yàn)。在常幅載荷下,用名義應(yīng)力強(qiáng)度因子幅表征的疲勞裂紋擴(kuò)展行為呈現(xiàn)出明顯的應(yīng)力比效應(yīng)�；谄趩⒘押土鸭y擴(kuò)展的統(tǒng)一模型能夠很好地預(yù)測(cè)不同應(yīng)力比下疲勞裂紋擴(kuò)展速率。單個(gè)拉伸過(guò)載會(huì)產(chǎn)生顯著的疲勞裂紋擴(kuò)展遲滯現(xiàn)象。當(dāng)裂紋擴(kuò)展出過(guò)載影響區(qū)后,疲勞裂紋擴(kuò)展行為將恢復(fù)到常幅載荷下的狀態(tài)。高-低變幅載荷工況引起的疲勞裂紋擴(kuò)展遲滯行為主要與兩個(gè)順序加載歷史參數(shù)有關(guān)。變幅載荷下的疲勞裂紋擴(kuò)展行為能夠采用Wheeler模型進(jìn)行合理地表征。
[Abstract]:Fatigue problem has always been one of the most important issues in industry. Fatigue fracture of metal parts and engineering structures not only causes huge economic losses, but also endangers the safety of people. Fatigue crack propagation behavior of materials is of great engineering practical value and socioeconomic significance. Fatigue crack is easy to crack in zero. In order to suppress the initiation and expansion of surface cracks, the surface of the material is usually strengthened. The shot peening is a widely used surface hardening process in industrial production. By injecting the residual compressive stress into the surface of the metal material and optimizing its microstructure, the anti fatigue and anti stress corrosion of the parts can be significantly improved. In recent years, with the rapid development of finite element technology and electronic computer, the study of shot peening mechanism and optimizing the parameters of shot peening process by numerical simulation has become the demand and trend of the further development of shot peening technology. The influence of the properties of the projectile material on the numerical results. The residual stress predicted by the symmetric cell model is evaluated from two aspects of the dynamic stress evolution and the distribution of the residual stress in the sprayed region. The residual pressure stress is more sensitive to the preloading stress. A random shot peening model is proposed based on the actual shot peening process and the statistical analysis based on the surface pits distribution on the sprayed surface. The model is used to simulate the two shot blasting process. The results show that the two shot peening intensifying can effectively strengthen the residual compressive stress on the surface of the target and reduce the stress. The surface roughness. Based on the spatio-temporal distribution model of the laser shock wave pressure and the unified constitutive model which can characterize the flow stress Arrhenius and non-Arrhenius characteristics of the material, a finite element model of the three dimensional single point laser shot peening high conductivity oxygen free (OFHC) copper is established. The model is used to study the laser power density and the laser pulse half width and width. The interaction of the effect of bolus intensification and the propagation characteristics of the stress wave inside the target. The residual stress intensification of the single point laser shot peening tends to saturate, which is mainly related to the history of the target hardening. The residual stress of the double-sided laser shot peening is very sensitive to the thickness of the target, which is mainly related to the interaction of the shock waves during the double shot peening process. In order to study the strengthening mechanism of the tissue structure of the shot peening, the grain size and the increased dislocation density of the sprayed zone are predicted by the dislocation density evolution model. The grain size of the target surface decreases remarkably under the impact load of the projectile or laser beam, and the dislocation density increases significantly, and is refined. The grain size and the increase of dislocation density gradually become saturated with the increase of repeated shot blasting times. In addition, the plastic constitutive model is established to simulate the deformation behavior of single crystal copper under the impact load. The fatigue crack propagation test of 2024-T4 aluminum alloy under constant amplitude and amplitude loading is carried out by non standard compact tensile specimens. Under load, the fatigue crack propagation behavior characterized by nominal stress intensity factor amplitude shows obvious stress ratio effect. A unified model based on fatigue crack initiation and crack propagation can well predict fatigue crack propagation rate under different stress ratios. A single tensile overload will produce significant fatigue crack growth retardation. The fatigue crack propagation behavior will be restored to the state of the constant amplitude load after the display of the overloading area. The fatigue crack growth retardation caused by the high low amplitude load condition is mainly related to the two historical parameters. The fatigue crack propagation behavior under the variable amplitude load can be reasonably characterized by the Wheeler model.

【學(xué)位授予單位】：浙江工業(yè)大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2016
【分類號(hào)】：TG668

【參考文獻(xiàn)】

相關(guān)期刊論文 前10條

1 王建杰;陳立宇;楊夏明;許楨英;王勻;;空化水射流的研究進(jìn)展[J];精密成形工程;2016年05期

2 張少波;布紫葉;;2024鋁合金隨機(jī)多彈丸噴丸后殘余應(yīng)力場(chǎng)的有限元模擬[J];機(jī)械工程材料;2016年07期

3 劉峰;魯世紅;張煒;;超聲波噴丸技術(shù)的研究進(jìn)展[J];航空制造技術(shù);2016年14期

4 王利平;王建明;趙莉莉;;基于正交試驗(yàn)法的噴丸工藝多目標(biāo)參數(shù)優(yōu)化[J];現(xiàn)代制造工程;2016年03期

5 高玉魁;蔣聰盈;;激光沖擊強(qiáng)化研究現(xiàn)狀與展望[J];航空制造技術(shù);2016年04期

6 李玉琴;王學(xué)德;楊竹芳;宋飛龍;;激光沖擊強(qiáng)化提高純銅耐磨性能的研究[J];強(qiáng)激光與粒子束;2016年02期

7 姜銀方;李娟;潘禹;蔣堯;李振;;雙面激光沖擊次序?qū)π】准䦶?qiáng)化效果影響研究[J];激光技術(shù);2016年01期

8 符永宏;劉強(qiáng)憲;葉云霞;華�？�;康正陽(yáng);符昊;;同點(diǎn)間隔多次激光微織構(gòu)工藝研究[J];中國(guó)激光;2015年12期

9 王冠;龍霓東;王波;何衛(wèi)鋒;沈曉駿;;激光沖擊加載純銅高應(yīng)變率下劇烈塑性變形行為觀察[J];材料科學(xué)與工程學(xué)報(bào);2015年04期

10 閆五柱;張嘉振;周振功;;噴丸過(guò)程中的摩擦影響研究[J];熱加工工藝;2014年18期

，

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