本文選題：激光噴丸 + TC6鈦合金　； 參考：《江蘇大學》2017年碩士論文

【摘要】：激光噴丸強化技術(shù)(Laser Peening,LP)是使用高功率脈沖激光照射工件表層,誘導產(chǎn)生超過材料屈服極限的沖擊波壓力,從而引起工件表層發(fā)生劇烈塑性變形、使材料晶粒細化并產(chǎn)生高密度的位錯組織。激光噴丸強化技術(shù)能顯著改善材料的應(yīng)力分布狀態(tài)和微觀組織,更好地抑制材料中裂紋源的萌生、擴展,從而提高航空關(guān)鍵部件的使用壽命。本文采用不同的激光功率密度與噴丸次數(shù)對TC6航空鈦合金進行激光噴丸,探索激光工藝參數(shù)對激光噴丸強化材料表面完整性的影響,研究激光噴丸強化TC6鈦合金的振動疲勞壽命,結(jié)合斷裂力學對振動疲勞斷口進行分析,根據(jù)振動疲勞失效過程中不同階段的斷口形貌,研究激光噴丸強化工藝對TC6鈦合金的疲勞延壽增益機制。本文的主要研究內(nèi)容有:研究激光噴丸誘導殘余壓應(yīng)力的產(chǎn)生過程及估算模型;結(jié)合振動疲勞失效及疲勞斷裂理論,分別從疲勞極限、裂紋擴展門檻值、應(yīng)力強度因子等幾個方面研究激光噴丸強化工藝對TC6鈦合金疲勞裂紋擴展速率的改善機理。使用高功率Nd:YAG固體激光器對TC6航空鈦合金試樣進行激光噴丸強化實驗,并對試樣表面方向及深度方向進行殘余應(yīng)力測定和顯微硬度測試。綜合使用激光共聚焦顯微鏡、掃描電子顯微鏡和透射電子顯微鏡等實驗手段研究激光噴丸前后試樣的微觀組織,包括α/β相形態(tài)、晶粒尺寸以及位錯形態(tài)等。利用振動疲勞實驗系統(tǒng)測定激光噴丸強化TC6航空鈦合金試樣的振動疲勞壽命,研究激光功率密度與噴丸次數(shù)對試樣振動疲勞壽命的影響規(guī)律。用掃描電子顯微鏡觀測振動疲勞試樣的斷口形貌,針對斷口中的裂紋源區(qū)、裂紋擴展區(qū)和最終斷裂區(qū),研究激光噴丸強化對TC6航空鈦合金振動疲勞斷口形貌的影響,通過疲勞條帶間距對TC6航空鈦合金的振動疲勞裂紋擴展速率進行分析。
[Abstract]:Laser peening technique (LP) is a method of irradiating the surface layer of the workpiece with high power pulse laser, which induces shock wave pressure beyond the material yield limit, thus causing severe plastic deformation of the surface layer of the workpiece. The grain size of the material is refined and high density dislocation structure is produced. Laser shot peening can improve the stress distribution and microstructure of the material, restrain the initiation and propagation of the crack source, and improve the service life of the key components of aviation. In this paper, laser shot peening of TC6 aeronautical titanium alloy was carried out with different laser power density and shot peening times, and the effect of laser processing parameters on surface integrity of laser shot peening strengthened material was explored. The vibration fatigue life of TC6 titanium alloy strengthened by laser shot peening was studied. The vibration fatigue fracture was analyzed in combination with fracture mechanics. According to the fracture morphology of different stages in the process of vibration fatigue failure, the vibration fatigue life of TC6 titanium alloy strengthened by laser shot peening was studied. The fatigue life extension gain mechanism of TC6 titanium alloy by laser shot peening was studied. The main contents of this paper are as follows: to study the process and estimation model of residual compressive stress induced by laser shot peening, to combine the theory of vibration fatigue failure and fatigue fracture, to analyze the fatigue limit and crack growth threshold, respectively. The improvement mechanism of laser shot peening on fatigue crack growth rate of TC6 titanium alloy was studied in several aspects such as stress intensity factor. High power Nd:YAG laser was used to test the laser shot peening of TC6 aeronautical titanium alloy samples. The residual stress and microhardness of the samples were measured in the direction of surface and depth. The microstructures of the samples before and after laser shot peening were studied by means of laser confocal microscope, scanning electron microscope and transmission electron microscope, including 偽 / 尾 phase morphology, grain size and dislocation morphology. The vibration fatigue life of TC6 aeronautical titanium alloy specimens strengthened by laser shot peening was measured by vibration fatigue test system. The effects of laser power density and shot peening times on the vibration fatigue life of the samples were studied. The fracture morphology of TC6 aeronautical titanium alloy was observed by scanning electron microscope (SEM). The effect of laser shot peening on the vibration fatigue fracture morphology of TC6 aeronautical titanium alloy was studied according to the crack source, crack propagation zone and final fracture zone. The vibration fatigue crack propagation rate of TC6 aeronautical titanium alloy was analyzed by fatigue strip spacing.
【學位授予單位】：江蘇大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TG668;TG146.23

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1 楊彌s，

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