应力水平对激光冲击强化圆角疲劳寿命的影响
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摘要
为了研究不同应力水平(疲劳试验过程中应力最大值)下,激光冲击强化对圆角结构疲劳寿命的影响,对半径为3mm的TC4-DT钛合金圆角试样进行了激光冲击试验,接着对试样进行拉-拉疲劳试验,在疲劳试验过程中采用的两种应力水平分别为385MPa和423MPa,应力比r=0.1,并通过扫描电子显微镜对疲劳断口进行分析。结果表明,激光冲击强化后,疲劳源从圆角表面向内部移动,且疲劳辉纹宽度减小,圆角结构疲劳寿命得到提高;当应力水平从385MPa增大至423MPa时,圆角疲劳寿命增益由246.2%减小至111.8%;激光冲击强化后,圆角结构表面形成一定深度的参与压应力,疲劳性能得到提高;但随着应力水平增大,激光冲击强化对圆角结构疲劳寿命的增益减小。该结果为针对薄弱区域强化而抑制疲劳裂纹萌生的研究具有指导意义。
In order to study effect of laser shock processing(LSP) on the fatigue life of fillet structures under different stress levels(the maximum stress during fatigue test),TC4-DT titanium alloy samples were subjected to laser shock processing,and then tensile stress test was carried out. The stress levels were 385 MPa and 423 MPa respectively,and the stress ratio r was 0.1.The fatigue fracture was analyzed by means of a scanning electron microscope(SEM). The results show that after laser shock processing,the fatigue crack initiation is moved from the fillet surface to the inside,the width of fatigue striation decreases,and the fatigue life of fillet structure is improved. With the increase of stress level,the gain of the fatigue life of the fillet treated by laser shock processing is reduced. When the stress level increases from 385 MPa to 423 MPa,the fatigue life gain of fillet structure decreases from 246. 2% to 111. 8%. After LSP,the surface of the fillet has a certain degree of compressive stress,and the fatigue life is improved. However,with the increase of the stress level,thefatigue life gain of the fillet structure is reduced. This result has guiding significance for the study on suppressing fatigue crack initiation by strengthening weak region.
In order to study effect of laser shock processing(LSP) on the fatigue life of fillet structures under different stress levels(the maximum stress during fatigue test),TC4-DT titanium alloy samples were subjected to laser shock processing,and then tensile stress test was carried out. The stress levels were 385 MPa and 423 MPa respectively,and the stress ratio r was 0.1.The fatigue fracture was analyzed by means of a scanning electron microscope(SEM). The results show that after laser shock processing,the fatigue crack initiation is moved from the fillet surface to the inside,the width of fatigue striation decreases,and the fatigue life of fillet structure is improved. With the increase of stress level,the gain of the fatigue life of the fillet treated by laser shock processing is reduced. When the stress level increases from 385 MPa to 423 MPa,the fatigue life gain of fillet structure decreases from 246. 2% to 111. 8%. After LSP,the surface of the fillet has a certain degree of compressive stress,and the fatigue life is improved. However,with the increase of the stress level,thefatigue life gain of the fillet structure is reduced. This result has guiding significance for the study on suppressing fatigue crack initiation by strengthening weak region.
引文
[1]LI Y H,HE W F,ZHOU L Ch.The strengthening mechanism of laser shock processing and its application on the aero-engine components[J].Scientia Sinica Technologica,2015,45(1):1-8(in Chinese).
[2]HU J L,LOU J,SHENG H C,et al.The effects of laser shock peening on microstructure and properties of metals and alloys:areview[J].Advanced Materials Research,2011,347/353:1596-1604.
[3]LI Zh.Investigation of residual stress and fatigue performance of titanium alloy part with hole by laser shock processing[D].Zhenjiang:Jiangsu University,2016:11-18(in Chinese).
[4]GOMEZ-ROSAS G,RUBIO-GONZALEZ C,OCANA J,et al.High level compressive residual stresses produced in aluminum alloys by laser shock processing[J].Applied Surface Science,2005,252(4):883-887.
[5]MONTROSS C S,WEI T,YE L,et al.Laser shock processing and its effects on microstructure and properties of metal alloys:a review[J].International Journal of Fatigue,2002,24(10):1021-1036.
[6]RANKIN J E,HILL M R,HACKEL L A.The effects of process variations on residual stress in laser peened 7049-T73 aluminum alloy[J].Materials Science and Engineering,2003,A349(1/2):279-291.
[7]CAO Z W,CHE Zh G,ZOU Sh K,et al.The effect of laser shock peening on fatigue property of 7050 aluminum alloy fastener hole[J].Applied Laser,2013,33(3):259-262(in Chinese).
[8]ZHANG M Y,ZHU Y,GUO W,et al.Effects of laser shock processing on fatigue properties of TC17 titanium alloy[J].Laser Technology,2017,41(2):231-234(in Chinese).
[9]RUBIO-GONZLEZ C,OCAA J L,GOMEZ-ROSAS G,et al.Effect of laser shock processing on fatigue crack growth and fracture toughness of 6061-T6 aluminum alloy[J].Materials Science&Engineering,2004,A386(1/2):291-295.
[10]PEYRE P,FABBRO R,MERRIEN P,et al.Laser shock processing of aluminum alloys.Application to high cycle fatigue behavior[J].Materials Science&Engineering,1996,A210(1/2):102-113.
[11]CLAUER A H,LAHRMAN D F.Laser shock processing as a surface enhancement process[J].Key Engineering Materials,2001,197(1775):121-144.
[12]JIANG Y F,LI J,PAN Y,et al.Investigation of effect of two-side laser shock order onsmall-hole specimen strengthening[J].Laser Technology,2016,40(1):82-85(in Chinese).
[13]WANG Zh P,GE M Zh.Impact of laser shock processing on fatigue strength of crankshaft[J].Machinery Design&Manufacture,2011(8):197-199(in Chinese).
[14]LI Q P,LI Y H,HE W F,et al.LSP to improve vibration fatigue performance of deflation valve lever[J].Journal of Beijing University of Aeronautics and Astronautics,2012,38(1):69-74(in Chinese).
[15]SPANRAD S,TONG J.Characterization of foreign object damage(FOD)and early fatigue crack growth in laser shock peened Ti-6AL-4V aerofoil specimens[J].Materials Science&Engineering,2011,A528(4):2128-2136.
[16]YANG C,HODGSON P D,LIU Q,et al.Geometrical effects on residual stresses in 7050-T7451 aluminum alloy rods subject to laser shock peening[J].Journal of Materials Processing Technology,2008,201(1):303-309.
[17]NIE X,HE W,ZANG S,et al.Effect study and application to improve high cycle fatigue resistance of TC11 titanium alloy by laser shock peening with multiple impacts[J].Surface&Coatings Technology,2014,253(9):68-75.
[18]HERSHKO E,MANDELKER N,GHEORGHIU G,et al.Assessment of fatigue striation counting accuracy using high resolution scanning electron microscope[J].Engineering Failure Analysis,2008,15(1/2):20-27.
[2]HU J L,LOU J,SHENG H C,et al.The effects of laser shock peening on microstructure and properties of metals and alloys:areview[J].Advanced Materials Research,2011,347/353:1596-1604.
[3]LI Zh.Investigation of residual stress and fatigue performance of titanium alloy part with hole by laser shock processing[D].Zhenjiang:Jiangsu University,2016:11-18(in Chinese).
[4]GOMEZ-ROSAS G,RUBIO-GONZALEZ C,OCANA J,et al.High level compressive residual stresses produced in aluminum alloys by laser shock processing[J].Applied Surface Science,2005,252(4):883-887.
[5]MONTROSS C S,WEI T,YE L,et al.Laser shock processing and its effects on microstructure and properties of metal alloys:a review[J].International Journal of Fatigue,2002,24(10):1021-1036.
[6]RANKIN J E,HILL M R,HACKEL L A.The effects of process variations on residual stress in laser peened 7049-T73 aluminum alloy[J].Materials Science and Engineering,2003,A349(1/2):279-291.
[7]CAO Z W,CHE Zh G,ZOU Sh K,et al.The effect of laser shock peening on fatigue property of 7050 aluminum alloy fastener hole[J].Applied Laser,2013,33(3):259-262(in Chinese).
[8]ZHANG M Y,ZHU Y,GUO W,et al.Effects of laser shock processing on fatigue properties of TC17 titanium alloy[J].Laser Technology,2017,41(2):231-234(in Chinese).
[9]RUBIO-GONZLEZ C,OCAA J L,GOMEZ-ROSAS G,et al.Effect of laser shock processing on fatigue crack growth and fracture toughness of 6061-T6 aluminum alloy[J].Materials Science&Engineering,2004,A386(1/2):291-295.
[10]PEYRE P,FABBRO R,MERRIEN P,et al.Laser shock processing of aluminum alloys.Application to high cycle fatigue behavior[J].Materials Science&Engineering,1996,A210(1/2):102-113.
[11]CLAUER A H,LAHRMAN D F.Laser shock processing as a surface enhancement process[J].Key Engineering Materials,2001,197(1775):121-144.
[12]JIANG Y F,LI J,PAN Y,et al.Investigation of effect of two-side laser shock order onsmall-hole specimen strengthening[J].Laser Technology,2016,40(1):82-85(in Chinese).
[13]WANG Zh P,GE M Zh.Impact of laser shock processing on fatigue strength of crankshaft[J].Machinery Design&Manufacture,2011(8):197-199(in Chinese).
[14]LI Q P,LI Y H,HE W F,et al.LSP to improve vibration fatigue performance of deflation valve lever[J].Journal of Beijing University of Aeronautics and Astronautics,2012,38(1):69-74(in Chinese).
[15]SPANRAD S,TONG J.Characterization of foreign object damage(FOD)and early fatigue crack growth in laser shock peened Ti-6AL-4V aerofoil specimens[J].Materials Science&Engineering,2011,A528(4):2128-2136.
[16]YANG C,HODGSON P D,LIU Q,et al.Geometrical effects on residual stresses in 7050-T7451 aluminum alloy rods subject to laser shock peening[J].Journal of Materials Processing Technology,2008,201(1):303-309.
[17]NIE X,HE W,ZANG S,et al.Effect study and application to improve high cycle fatigue resistance of TC11 titanium alloy by laser shock peening with multiple impacts[J].Surface&Coatings Technology,2014,253(9):68-75.
[18]HERSHKO E,MANDELKER N,GHEORGHIU G,et al.Assessment of fatigue striation counting accuracy using high resolution scanning electron microscope[J].Engineering Failure Analysis,2008,15(1/2):20-27.