氧化铝涂层垂直裂纹对热载荷下界面失效的影响
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摘要
目的探索氧化铝/铝在热载荷作用下的界面失效机理。方法基于内聚力有限元模型,预测热载荷下铝基氧化铝涂层材料界面处的残余热应力,并系统研究其失效过程。重点考虑涂层厚度、热载荷大小、预制涂层垂直裂纹密度对界面处应力场和界面损伤失效的影响,并同实验进行对比。结果试验和模拟结果都发现,加热到300℃冷却后,界面未产生平行裂纹,而加热到400℃冷却后,界面出现平行裂纹。涂层无裂纹缺陷时,界面处剪应力呈单曲线余弦分布,而有预制裂纹时,界面处的剪应力呈双曲线余弦分布。随着热载荷的增大,界面最大剪应力值由两端向界面中心处迁移。相比涂层有裂纹的情况,界面在涂层无裂纹时平均正应力最小。实际制备的氧化铝涂层不可能完美无裂纹缺陷,在考虑涂层有裂纹缺陷时,涂层裂纹密度为4 mm~(-1)时平均所受正应力较小,且界面只有拉应力作用,不容易产生脱层缺陷。结论存在特定的最佳临界预制垂直裂纹密度值,使得热载荷下界面损伤最小。有限元模拟结果也显示,相同热载荷和相同裂纹密度下,涂层越厚,对界面的防护力也越强。
To investigate the interface failure mechanism of alumina-coating/aluminum under thermal loads. The residual thermal stress at the interface under thermal loads was predicted, and the interface failure of the alumina-coating/aluminum was systematically studied by the finite element model with a cohesive zone. The effects of the coating thickness, the thermal load magnitude, and the vertical crack density of the coating on the stress field at the interface and the interface damage failure were considered and compared with experiments. Experimental and simulation results showed that, as the interface was cooled after heated to 300 ℃, no parallel cracks was observed at the interface. However, as the interface was heated to 400 ℃ and then cooled, parallel cracks were observed at the interface. The shear stresses at the interface showed a single-curve cosine distribution when there was no crack defect in the coating, while the shear stresses showed a hyperbolic cosine distribution when there was vertical cracks in the coating. With the increase of thermal load, the maximum shear stress at the interface migrated from both ends to the center. Coatings without vertical cracks had a minimum average normal stress compared to coatings with verti-cal cracks. However, the actually prepared alumina coating was unlikely to be free of defects. When the coating crack density was 4 mm~(-1), the average residual normal stress was small, and the interface had only tensile stress, which caused the interface to be less likely to delaminate. There is a specific optimum critical pre-fabricated vertical crack density value, which minimizes interface failure under thermal loading. The finite element results also indicate that, the thicker the coating is, the stronger the thermal protection of interface is under the same thermal load and the same density.
To investigate the interface failure mechanism of alumina-coating/aluminum under thermal loads. The residual thermal stress at the interface under thermal loads was predicted, and the interface failure of the alumina-coating/aluminum was systematically studied by the finite element model with a cohesive zone. The effects of the coating thickness, the thermal load magnitude, and the vertical crack density of the coating on the stress field at the interface and the interface damage failure were considered and compared with experiments. Experimental and simulation results showed that, as the interface was cooled after heated to 300 ℃, no parallel cracks was observed at the interface. However, as the interface was heated to 400 ℃ and then cooled, parallel cracks were observed at the interface. The shear stresses at the interface showed a single-curve cosine distribution when there was no crack defect in the coating, while the shear stresses showed a hyperbolic cosine distribution when there was vertical cracks in the coating. With the increase of thermal load, the maximum shear stress at the interface migrated from both ends to the center. Coatings without vertical cracks had a minimum average normal stress compared to coatings with verti-cal cracks. However, the actually prepared alumina coating was unlikely to be free of defects. When the coating crack density was 4 mm~(-1), the average residual normal stress was small, and the interface had only tensile stress, which caused the interface to be less likely to delaminate. There is a specific optimum critical pre-fabricated vertical crack density value, which minimizes interface failure under thermal loading. The finite element results also indicate that, the thicker the coating is, the stronger the thermal protection of interface is under the same thermal load and the same density.
引文
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[14]NGUYEN O,REPETTO E A,ORTIZ R A,et al.A cohesive model of fatigue crack growth[J].International journal of fracture,2001,110(4):351-369.
[15]JING J P,GAO F,JOHNSON J,et al.Simulation of dynamic fracture along solder-pad interfaces using a cohesive zone model[J].Engineering failure analysis,2009,16(5):1579-1586.
[16]GEUBELLE P H,BAYLOR J S.Impact-induced delamination of composites:a 2D simulation[J].Composites part B:Engineering,1998,29(5):589-602.
[17]XIE C G,TONG W.Cracking and decohesion of a thin Al2O3 film on a ductile Al-5%Mg substrate[J].Acta materialia,2005,53(14):477-485.
[18]LI X N,LIANG L H,XIE J J.Thickness-dependent fracture characteristics of ceramic coatings bonded on the alloy substrates[J].Surface&coatings technology,2014,258:1039-1047.
[19]左焕然.6061铝合金薄板高硬度硬质阳极氧化膜的制备[D].成都:西华大学,2009.ZUO Huan-ran.Prepare of high hardness anodize oxidation film on 6061 aluminum alloy sheet[D].Chengdu:Xihua University,2009.
[20]师昌绪,江东亮,李龙土.中国材料工程大典第八卷[M].北京:化学工业出版社,2005:30-43.SHI Chang-xu,JIANG Dong-liang,LI Long-tu.The eighth volume of china materials engineering[M].Beijing:Chemical Industry Press,2005:30-43.
[21]TSUI Y C,CLYNE T W.An analytical model for predicting residual stresses in progressively deposited coatings part 2:Cylindrical geometry[J].Thin solid films,1997,306(1):34-51.
[22]ZHU W,YANG L,GUO J W,et al.Numerical study on interaction of surface cracking and interfacial delamination in thermal barrier coatings under tension[J].Applied surface science,2014,315:292-298.
[23]华佳捷,张丽鹏,刘紫微,等.热障涂层失效机理研究进展[J].无机材料学报,2012,27(7):680-686.HUA Jia-jie,ZHANG Li-peng,LIU Zi-wei,et al.Progress of research on the failure mechanism of thermal barrier coatings[J].Journal of inorganic materials,2012,27(7):680-686.
[2]周储伟,杨卫,方岱宁.内聚力界面单元与复合材料的界面损伤分析[J].力学学报,1999,31(3):372-376.ZHOU Chu-wei,YANG Wei,FANG Dai-ning.Cohesive interface element and interfacial damage analysis of composite[J].Acta mechanica sinica,1999,31(3):372-376.
[3]PATERMARAKIS G.Aluminium anodising in low acidity sulphate baths:growth mechanism and nanostructure of porous anodic films[J].Journal of solid state electrochemistry,2006,10(4):211-222.
[4]杨雪松.基于内聚力单元热障涂层体系失效过程有限元模拟分析[D].湘潭:湘潭大学,2013.YANG Xue-song.Finite element analysis of failure process of thermal barrier coating by using cohesive element[D].Xiangtan:Xiangtan University,2013.
[5]LIUAB D,SERAFFONCD M,FLEWITTAE P E J,et al.Effect of substrate curvature on residual stresses and failure modes of an air plasma sprayed thermal barrier coating system[J].Journal of the european ceramic society,2013,33(15-16):3345-3357.
[6]PAOLA P,YANICET O.Characterization of residual compressive stresses in layered ceramics by positron annihilation spectroscopy[J].Journal of the european ceramic society,2012,32(2002):3989-3993.
[7]朱丽慧,胡涛,彭笑,等.Al含量对TiAlN涂层结合强度的影响[J].材料热处理学报,2015,36(3):154-158.ZHU Li-hui,HU Tao,PENG Xiao,et al.Effect of Al content on adhesion strength of TiAlN coatings[J].Transactions of materials and heat treatment,2015,36(3):154-158.
[8]夏宇锋,江五贵,吴志凯.热载荷下蜂窝铝基Al2O3涂层材料的残余应力和失效分析[J].材料热处理学报,2016,37(6):193-197.XIA Yu-feng,JIANG Wu-gui,WU Zhi-kai.Analysis of residual stresses and failure of aluminum honeycomb with Al2O3 coating under thermal loads[J].Transactions of materials and heat treatment,2016,37(6):193-197.
[9]JIANG W G,ZHONG R Z,QIN Q H,et al.Homogenized finite element analysis on effective elastoplastic mechanical behaviors of composite with imperfect interfaces[J].International journal of molecular sciences,2014,15:23389-23407.
[10]吴志凯,江五贵,郑隆.界面对双向纤维增强复合材料力学性能的影响[J].复合材料学报,2017,34(1):217-223.WU Zhi-kai,JIANG Wu-gui,ZHENG Long.Interfacial effect on mechanical behaviors of bidirectional-fiberreinforced composites[J].Acta materiae compositae sinica,2017,34(1):217-223.
[11]DUGDALE D.Yielding of steel sheets containing slits[J].Journal of mechanics and physics of solids,1960,8(2):100-108.
[12]BARENBLATT G.The mathematical theory of equilibrium cracks in brittle fracture[J].Advanced in applied mechanics,1962,7:55-125.
[13]HILLERBORGA A,MODEER M,PETERSSON P.Analysis of crack formation and crack growth in concrete by means of fracture mechanics and finite elements[J].Cement concret,1976,6:773-782.
[14]NGUYEN O,REPETTO E A,ORTIZ R A,et al.A cohesive model of fatigue crack growth[J].International journal of fracture,2001,110(4):351-369.
[15]JING J P,GAO F,JOHNSON J,et al.Simulation of dynamic fracture along solder-pad interfaces using a cohesive zone model[J].Engineering failure analysis,2009,16(5):1579-1586.
[16]GEUBELLE P H,BAYLOR J S.Impact-induced delamination of composites:a 2D simulation[J].Composites part B:Engineering,1998,29(5):589-602.
[17]XIE C G,TONG W.Cracking and decohesion of a thin Al2O3 film on a ductile Al-5%Mg substrate[J].Acta materialia,2005,53(14):477-485.
[18]LI X N,LIANG L H,XIE J J.Thickness-dependent fracture characteristics of ceramic coatings bonded on the alloy substrates[J].Surface&coatings technology,2014,258:1039-1047.
[19]左焕然.6061铝合金薄板高硬度硬质阳极氧化膜的制备[D].成都:西华大学,2009.ZUO Huan-ran.Prepare of high hardness anodize oxidation film on 6061 aluminum alloy sheet[D].Chengdu:Xihua University,2009.
[20]师昌绪,江东亮,李龙土.中国材料工程大典第八卷[M].北京:化学工业出版社,2005:30-43.SHI Chang-xu,JIANG Dong-liang,LI Long-tu.The eighth volume of china materials engineering[M].Beijing:Chemical Industry Press,2005:30-43.
[21]TSUI Y C,CLYNE T W.An analytical model for predicting residual stresses in progressively deposited coatings part 2:Cylindrical geometry[J].Thin solid films,1997,306(1):34-51.
[22]ZHU W,YANG L,GUO J W,et al.Numerical study on interaction of surface cracking and interfacial delamination in thermal barrier coatings under tension[J].Applied surface science,2014,315:292-298.
[23]华佳捷,张丽鹏,刘紫微,等.热障涂层失效机理研究进展[J].无机材料学报,2012,27(7):680-686.HUA Jia-jie,ZHANG Li-peng,LIU Zi-wei,et al.Progress of research on the failure mechanism of thermal barrier coatings[J].Journal of inorganic materials,2012,27(7):680-686.