本文選題：TC4 + ELI鈦合金��； 參考：《浙江大學》2015年碩士論文

【摘要】：TC4鈦合金由于具有密度低、屈強比高等一系列優(yōu)點而被廣泛應用于航空航天等領(lǐng)域。在實際應用中,大量服役中的工程裝備常常承受復雜的交變載荷作用,僅僅依靠材料本身的疲勞抗力有時難以滿足工程裝備的長服役壽命和高可靠性等技術(shù)要求。噴丸處理作為有效的表面強化處理方法,已被廣泛應用于提高材料及其構(gòu)件的疲勞強度和疲勞壽命。因此,為了促進鈦合金在航空航天等領(lǐng)域中的更好應用,系統(tǒng)研究噴丸處理后鈦合金材料表面強化層的殘余應力場和力學性能分布規(guī)律,進而研究噴丸工藝參數(shù)與殘余應力分布特征的相關(guān)性,并進一步研究噴丸強化殘余應力場的定量評估方法等,將具有重要的工程實際意義。本文主要采用深度敏感壓痕測試和金相組織檢查,并結(jié)合有限元數(shù)值模擬方法,系統(tǒng)研究了TC4 ELI鈦合金光滑試樣和單邊缺口試樣噴丸強化層的殘余應力分布和力學性能變化規(guī)律。首先,采用深度敏感壓痕技術(shù),結(jié)合M.Dao等人提出的逆向算法確定出噴丸強化層材料力學性能的變化特征。結(jié)果表明：噴丸撞擊引起的材料非均勻形變硬化和延性耗散提高了噴丸強化層材料的剛度特性和變形抗力,但降低了強化層材料的塑性與韌性性質(zhì)。上述材料力學性能的變化規(guī)律與噴丸強度相關(guān)。其次,應用顯微分析術(shù)研究發(fā)現(xiàn)：噴丸強化層內(nèi)材料產(chǎn)生了明顯的滑移帶,噴丸撞擊引起材料表面位錯密度的提高導致了變形層的循環(huán)硬化,使噴丸強化層內(nèi)的顯微組織趨于等軸化且誘發(fā)了β相向α相的轉(zhuǎn)變。同時,基于深度敏感壓痕測試,采用Suresh修正模型確定出不同噴丸強度下光滑與缺口試樣的殘余應力分布特征。結(jié)果表明：噴丸引入的殘余應力場由表層的壓殘余應力區(qū)向次表層的拉殘余應力區(qū)過渡。噴丸強度的提高增大了壓殘余應力區(qū)域,但對其最大壓殘余應力的影響很小。噴丸強化殘余應力場的分布規(guī)律與噴丸強度相關(guān)�；诒疚奶岢龅臍堄鄳Χ吭u估方法得到的結(jié)果與其深度敏感壓痕測試獲得的殘余應力場兩者基本一致。最后,論文還采用有限元數(shù)值模擬方法研究了噴丸強化光滑試樣的殘余應力分布特征,并與深度敏感壓痕測試得到的殘余應力場進行了對比。結(jié)果表明：數(shù)值模擬得到的噴丸強化殘余應力場與深度敏感壓痕測試得到的結(jié)果取得了很好的一致性。
[Abstract]:TC4 titanium alloys are widely used in aeronautics and spaceflight due to their low density and high yield ratio. In practical application, a large number of engineering equipment in service often bear complex alternating loads, and it is sometimes difficult to meet the technical requirements of long service life and high reliability of engineering equipment only by relying on the fatigue resistance of the material itself. As an effective method of surface strengthening, shot peening has been widely used to improve the fatigue strength and fatigue life of materials and their components. Therefore, in order to promote the better application of titanium alloy in aerospace and other fields, the distribution of residual stress field and mechanical properties of the strengthened layer on the surface of titanium alloy after shot peening is studied systematically. Furthermore, it is of great practical significance to study the correlation between the parameters of shot peening and the distribution characteristics of residual stress, and to further study the quantitative evaluation method of the residual stress field strengthened by shot peening. In this paper, the depth sensitive indentation test and metallographic examination are used, and the finite element numerical simulation method is used. The distribution of residual stress and the change of mechanical properties of shot peening strengthened layers of TC4 ELI titanium alloy smooth and unilateral notched samples were systematically studied. Firstly, the depth sensitive indentation technique and the reverse algorithm proposed by M.Dao et al are used to determine the characteristics of mechanical properties of shot peening strengthened layer. The results show that the inhomogeneous deformation hardening and ductility dissipation caused by shot peening increase the stiffness and deformation resistance of the shot peening strengthened layer, but decrease the plasticity and toughness of the strengthened layer. The change of mechanical properties of the above mentioned materials is related to the shot-peening strength. Secondly, it is found by microanalysis that there are obvious slip bands in the peening strengthened layer, and the increase of dislocation density on the surface of the material caused by shot peening results in cyclic hardening of the deformed layer. The microstructure in the shot peening strengthened layer tends to be equiaxed and the transformation of 尾 phase to 偽 phase is induced. At the same time, based on the depth sensitive indentation test, the residual stress distribution characteristics of smooth and notched specimens under different shot peening strength were determined by Suresh modified model. The results show that the residual stress field induced by shot peening is transferred from the compressive residual stress zone to the tensile residual stress zone. The increase of shot peening strength increases the area of compressive residual stress, but has little effect on the maximum compressive residual stress. The distribution of the residual stress field of shot peening is related to the shot peening strength. The results obtained based on the quantitative evaluation method of residual stress proposed in this paper are basically consistent with the residual stress field obtained by the depth sensitive indentation test. Finally, the residual stress distribution of shot peening smooth specimen is studied by finite element method, and compared with the residual stress field obtained by depth sensitive indentation test. The results show that the results obtained by numerical simulation are in good agreement with those obtained by depth sensitive indentation test.
【學位授予單位】：浙江大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：TG668

【參考文獻】

相關(guān)期刊論文 前1條

1 蔣麗梅;周益春;黃勇力;;Elastic-plastic properties of thin film on elastic-plastic substrates characterized by nanoindentation test[J];Transactions of Nonferrous Metals Society of China;2010年12期

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本文編號：1866248