碩士論文激光噴丸強(qiáng)化ti6al4v航空鈦合金疲勞裂紋擴(kuò)展性能研究畢設(shè)論文-展示頁
2024-08-11 11:13本頁面
【正文】 erospace Titanium Alloy Treated by Laser Peening16江蘇大學(xué)碩士學(xué)位論文摘 要激光噴丸強(qiáng)化技術(shù)（Laser Peening, LP）是一種新型的材料表面強(qiáng)化技術(shù)，其利用高功率短脈沖激光束與材料表面相互作用產(chǎn)生的高幅值沖擊波壓力使材料表面發(fā)生塑性變形、晶粒細(xì)化、高密度位錯(cuò)，并在材料表面產(chǎn)生比傳統(tǒng)機(jī)械噴丸更深的殘余壓應(yīng)力層來顯著提高材料的抗疲勞特性，能有效延長航空發(fā)動(dòng)機(jī)關(guān)鍵零部件的疲勞壽命，降低其疲勞裂紋擴(kuò)展速率，在航空航天等領(lǐng)域有廣泛的應(yīng)用。本文以線彈性斷裂力學(xué)及彈塑性斷裂力學(xué)理論為基礎(chǔ)，以Ti6Al4V航空鈦合金為研究對象，將試驗(yàn)研究與有限元分析驗(yàn)證相結(jié)合，對激光噴丸強(qiáng)化航空鈦合金薄板件后的殘余應(yīng)力分布及疲勞裂紋擴(kuò)展性能進(jìn)行了系統(tǒng)的研究，主要工作集中在以下幾點(diǎn)：分析了Ti6Al4V航空鈦合金薄板件激光噴丸后殘余應(yīng)力場的分布情況，研究了激光噴丸誘導(dǎo)殘余應(yīng)力場對Ti6Al4V航空鈦合金薄板件疲勞裂紋擴(kuò)展性能的影響；基于線彈性及彈塑性斷裂力學(xué)理論，探討了激光噴丸誘導(dǎo)殘余應(yīng)力場作用下裂紋尖端應(yīng)力強(qiáng)度因子ΔK的變化情況及疲勞裂紋擴(kuò)展速率和疲勞壽命分布。利用MTS809電液伺服材料測試系統(tǒng)進(jìn)行疲勞裂紋擴(kuò)展試驗(yàn)，研究激光噴丸后Ti6Al4V航空鈦合金試樣疲勞裂紋擴(kuò)展速率及疲勞壽命，結(jié)果表明激光噴丸能夠有效降低鈦合金疲勞裂紋擴(kuò)展速率，大幅提高其疲勞壽命。，建立了激光噴丸強(qiáng)化Ti6Al4V航空鈦合金疲勞裂紋擴(kuò)展性能的有限元模型，對不同激光功率密度下和不同噴丸覆蓋率下激光噴丸航空鈦合金表面及次表面殘余應(yīng)力分布及不同殘余應(yīng)力場下疲勞裂紋擴(kuò)展性能進(jìn)行探討，結(jié)果表明：激光噴丸能夠有效減小裂紋擴(kuò)展驅(qū)動(dòng)力，降低裂紋擴(kuò)展速率，延長裂紋擴(kuò)展壽命，有限元分析結(jié)果和試驗(yàn)結(jié)果一致，充分驗(yàn)證了將有限元分析技術(shù)應(yīng)用在激光噴丸強(qiáng)化疲勞裂紋擴(kuò)展領(lǐng)域的正確性。 the stress intensity factor of crack tip ΔK, fatigue crack growth rate and fatigue life were discussed based on fracture mechanics.The highpower solidstate laser was used in the experiments to carry out the LP process on CT samples of titanium alloy both under different power densities and different coverage rates. Residual stress distribution was measured using Xray diffraction equipment. MTS809 electrohydraulic servo test system was adopted to perform the fatigue crack growth experiment, at the same time, fatigue life and crack growth rate were both studied which verified that LP can decrease fatigue crack growth rate of titanium alloy apparently, enhance fatigue life and confirmed the correctness of numerical simulation.Fatigue fracture morphology was analyzed by SEM, the results showed that, there exists lots of fatigue striation in stable growth stage, and the fatigue striation spacing bees larger with crack growth, there were apparent dimples in the final rupture stage, and the characteristic of dimples vary with the LP process parameters. This pointed out the lifeprolong mechanism of LP on titanium alloys from microstructure.The ABAQUS software and were adopted to establish the model of fatigue crack growth property of Ti6Al4V titanium alloy treated by LP. Residual stress on topsurface and subsurface of samples and the fatigue crack growth property under different power d
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