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Effect of cold expansion on fatigue life of anodized Al alloy

IOP Conference Series: materials science and Engineering 2019年第2期490卷

作者： Nan Li Haitao Li Hongtao Liu Changkui Liu AECC Beijing Institute of Aeronautical Materials Beijing 100095 China Beijing Key Laboratory of Aeronautical Materials Testing and Evaluation Beijing 100095 China Aviation Key Laboratory of Science and Technology on Materials Testing and Evaluation Beijing 100095 China Key Laboratory of Aeronautical Materials Testing and Evaluation Aero Engine Corporation of China Beijing 100095 China Structure Department Shenyang Aircraft Design Research Institute Shenyang 110035 China

Anodizing treatment can improve corrosion resistance of aluminum alloy but decrease the fatigue life significantly. Introducing cold expansion before anodizing can increase the fatigue life of the specimen with open-hole structure by 2582% than the anodized one. Scanning electron microscopy (SEM) was employed for microstructure and fracture surface observation. Residual stress distribution near the sample hole edge was measured to elucidate the strengthening mechanism. The results revealed that although anodizing treatment decreases the surface integrity, the cold expansion is an effective method to improve the open-hole structure specimen remarkably.

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Experimental evaluation of Fatigue Behaviors and Tensile Properties of Selective Laser Melted K536 Alloy at Elevated Temperatures

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Procedia Structural Integrity 2017年 7卷 84-91页

作者： R.D. Xu Z.H. Jiao H.C. Yu Aviation Key Laboratory of Science and Technology on Materials Testing and Evaluation Science and Technology on Advanced High Temperature Structrual Materials Laboratory Beijing Key Laborotory of Aeronautical Materials Testing and Evaluation Beijing Institute of Aeronautical Materials Beijing 100095 China

Additive-manufacturing techniques show more and more utilization potentialities in today’s aviation industry. In order to ensure safe operation of additive-manufactured parts, it is important to have their mechanical properties well-characterized and assessed. In this study, elevated temperature fatigue behaviours and tensile properties of a selective laser melting (SLM) fabricated K536 alloy are investigated for horizontal and vertical building orientation, respectively. A series of tensile tests at 20 ºC ~700 ºC temperature range and stress-controlled fatigue tests at 400ºC and 600ºC are conducted. Effects of building orientation and temperature on tensile and fatigue behaviours are analysed. Scanning Electron Microscopy (SEM) is used to examine the fracture surfaces of fatigue specimens to qualify the failure mechanism and crack initiation sites. K536 parts manufactured via SLM are shown to exhibit anisotropic tensile properties at different testing temperatures. Anisotropy of fatigue properties is not obvious at 400ºC and 600ºC. Cracks are likely to initiate at the surface sliding or subsurface crystallographic plane of fatigue specimens in middle life regime and at subsurface or central zone crystallographic plane in longer life regime. In shorter life regime, cracks are easy to initiate at un-melted zones of fatigue specimens.

关键词： Additive manufacturing Selective Laser Melting K536 fatigue behavior tensile

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evaluation on Tensile and Fatigue Crack Growth Performances of Ti6Al4V Alloy Produced by Selective Laser Melting

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Procedia Structural Integrity 2017年 7卷 124-132页

作者： Z.H. Jiao R.D. Xu H.C. Yu X.R. Wu Aviation Key Laboratory of Science and Technology on Materials Testing and Evaluation Science and Technology on Advanced High Temperature Structrual Materials Laboratory Beijing Key Laborotory of Aeronautical Materials Testing and Evaluation Beijing Institute of Aeronautical Materials Beijing 100095 China

Additive manufacturing (AM) technologies are increasing in importance for aerospace application, where the demand for a fundamental understanding and predictability of static and dynamic material properties are high. As the most widely used and studied alloy for this technology, Selective laser melting (SLM) produced Ti6Al4V alloy is evaluated on tensile and fatigue crack growth (FCG) performances at RT and 400℃. Conventionally manufactured Ti6Al4V alloys are concerned for comparison. Different orientations are considered to investigate the anisotropy of tensile and FCG behavior. The results show that, the tensile properties at RT and 400℃ are highly dependent on the specimen orientation relative to build direction. The FCG resistance is related to specimen orientation in the near threshold region but no relationship with specimen orientation in the steady growth stage at RT. The FCG resistance is much less influenced by specimen orientation at 400℃. The tensile strength at RT and 400℃ of SLM alloy reaches even exceeds the strength level of conventionally manufactured alloys such as forging, bar and casting. The steady stage FCG resistance under stress ratio of 0.1 of SLM alloy is also comparable to conventionally manufactured alloys. The SLM alloy shows higher FCG resistance under stress ratio of 0.1 than 0.5, but the d a /d N -△ K curves of the two stress ratios are very close to each other. The steady stage FCG rate at RT is slower than 400℃ in the lower △ K region and faster in the higher △ K region.

关键词： SLM tensile properties fatigur crack growth anisotropy elevated temperature

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Analysis of Crack Growth Retardation after Single Overload Based on FEM Simulation and CORPUS Model Prediction

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IOP Conference Series: materials science and Engineering 2018年第2期322卷

作者： Lina Zhang Qianqian Gao Shaojun Ma Dihua Tong Beijing Institute of Aeronautical Materials Beijing China Beijing Key Laboratory of Aeronautical Materials Testing and Evaluation Aviation Key Laboratory of Science and Technology on Aeronautical Materials Testing and Evaluation

In this paper, the distribution of the residual stress and equivalent plastic strain along the crack surfaces of the current crack with the crack growth is presented by finite element calculation. The residual stress intensity factor K res was calculated by using the weight function method (WFM), and the effective stress range S eff during the crack growth in the retardation zone is shown based the simulative calculation. Then, the effective stress range S eff with different R ol have been predicted by CORPUS model. The results indicate that the FEM simulative calculation and the CORPUS model prediction are agreement. They all show the crack growth retardation after an overload at different overload ratio R ol, and the effects of crack growth rate by the retardation.

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Influence of Temperature on Stacking Fault Energy and Creep Mechanism of a Single Crystal Nickel-based Superalloy

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Journal of materials science & technology 2016年第8期32卷 790-798页

作者： Sugui Tian Xinjie Zhu Jing Wu Huichen Yu Delong Shu Benjiang Qian Shenyang University of Technology Shenyang 110870 China Aviation Key Laboratory of Science and Technology on Materials Testing and Evaluation Science and Technology on Advanced High TemperatureStructural Materials Laboratory Beijing Institute of Aeronautical Materials Beijing 100095 China

The influence of temperatures on the stacking fault energies and deformation mechanism of a Re- containing single crystal nickel-based superalloy during creep at elevated temperatures was investigated by means of calculating the stacking fault energy of alloy, measuring creep properties and performing contrast analysis of dislocation configuration. The results show that the alloy at 760 ℃ possesses lower stacking fault energy, and the stacking fault of alloy increases with increasing temperature. The defor- mation mechanism of alloy during creep at 760 ℃ is 7＇ phase sheared by 〈110〉 super-dislocations, which may be decomposed to form the configuration of Shockley partials plus super-lattice intrinsic stacking fault, while the deformation mechanism of alloy during creep at 1070 ℃ is the screw or edge super- dislocations shearing into the rafted 7＇ phase. But during creep at 7（50 and 980 ℃, some super- dislocations shearing into 7＇ phase may cross-slip from the {111} to {100} planes to form the K-W locks with non-plane core structure, which may restrain the dislocations slipping to enhance the creep resis- tance of alloy at high temperature. The interaction between the Re and other elements may decrease the diffusion rate of atoms to improve the microstructure stability, which is thought to be the main reason why the K-W locks are to be kept in the Re-containing superalloy during creep at 980 ℃.

关键词： Single crystal nickel-based superalloy Stacking fault energy Creep Contrast analysis Deformation mechanism

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Mechanical Properties Analysis of Patch Repaired Composite Structures with Debonding Flaw

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IOP Conference Series: materials science and Engineering 2019年第1期472卷

作者： Xia Guo Hai Chi Junzhi He Weili Liu Guanghui Hu Xia Gao Beijing Centre for Physical and Chemical Analysis Beijing 100089 China Beijing Key Laboratory of Organic Materials Testing Technology & Quality Evaluation Beijing 100089 China No. 7 Fengxian Middle Road Haidian District Beijing 100094 Beijing Academy of Science and Technology Key Laboratory of Analysis and Testing Technology Beijing 10089 China.

Increasing use of composite structures in transport industry puts forward new requirements for its maintenance and repair. However, bonding repair process will produce inevitable debonding flaws, and there will also be debonding damage during use service. In this paper, mechanisms properties of compression failure of patch repaired composite structures were explored, and effects of flaws on the properties were analysed. The results showed that buckling of patch repaired structures first occurred in compression process and then failed. Patch repaired structures broke at the damage hole. Under compression load, debonding flaw of patch repaired composite structures would be expanded, which caused the patch and the parent laminates to be detached earlier, and compression bearing capacity became weaker.

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Delamination properity of 2060 aluminium lithium alloy laminate

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IOP Conference Series: materials science and Engineering 2018年第3期322卷

作者： Xiang Guo Yi Huang Dihua Tong Shaojun Ma AECC Beijing Institute of Aeronautical Materials Beijing 100095 China Beijing Key Laboratory of Aeronautical Materials Testing and Evaluation Aviation Key Laboratory of Science and Technology on Aeronautical Materials Testing and Evaluation Beihang University Beijing 100191 China

Delamination is an significant property of aluminium lithium alloy laminate for damage tolerance design. Double Crack Lap Shear specimens of '2/1' structure are used for testing delamination properity. Experiments of 2 stress ratio conditions R=0.06, 0.5 are conducted, and 5 stress levels for each stress ratio. Delamination growth data b-N are obtained from 4 crack tips' locations. The energy release rate, Gd, of the '2/1' structure laminate are calculated. Alderliesten modelis used for describing delamination growth db/dN and energy release rate Gd. Parameters Cd and nd in Alderliesten model are determined for R=0.06 and R=0.5 by linear fitting. An analysis is made by comparing the results of different stress ratio conditons.

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Characterization of creep behavior of TiAl alloy with high Nb content at elevated temperatures

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Rare Metals 2016年第1期35卷 106-112页

作者： Cheng-Li Dong Hui-Chen Yu Ze-Hui Jiao Beijing Key Laboratory of Aeronautical Materials Testing and Evaluation Science and Technology on Advanced High Temperature Structural Materials LaboratoryBeijing Institute of Aeronautical Materials Science and Technology on Advanced High Temperature Structural Materials Laboratory Beijing Institute of Aeronautical Materials

Creep experiments of the TiAl alloy with high Nb content were conducted to consider both the temperature dependence and stress dependence of its creep *** creep curves were characterized by Theta constitutive model,and Newton-Gauss method was applied to obtain the material *** on the rupture strain,the rupture life of the TiAl alloy was able to be predicted by Theta constitutive *** results show that the creep curves of the TiAl alloy contain primary creep,secondary creep and tertiary creep stages,especially for the lower *** rupture life of the TiAl alloy decreases with the increase in either applied stress or *** constitutive model is able to describe the creep deformation of the TiAl alloy accurately,and the predicted life agrees well with the experimental result.

关键词： TiAl alloy Creep Rupture Life prediction Theta constitutive model

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Analysis of the effect of fretting wear on key structural components of TB6 titanium alloy with actual failure cases

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IOP Conference Series: materials science and Engineering 2018年第2期439卷

作者： Huanping Kong Changkui Liu AECC Beijing Institute of Aeronautical Materials Beijing BJ10 China Beijing Key Laboratory of Aeronautical Materials Testing and Evaluation Beijing BJ10 China Aviation Key Laboratory of Science and Technology on Aeronautical Materials Testing and Evaluation Beijing BJ10 China

As the main metal structure materials, titanium alloys have been widely applied in aerospace and other military industries. Titanium alloy develops on the way of high performance and functionalization. Compared with other materials, titanium alloy has high surface integrity and high fretting damage sensitivity. In this paper, the failure case of TB6 high strength titanium alloy key structural parts is taken as the breakthrough point to analyze the effect of surface fretting wear damage on its performance. The appearance inspection, macro and micro morphology observation and energy spectrum analysis were carried out, and the microstructure examination and hardness test were also adopted. The results showed that the fracture property of lug of TB6 high strength titanium alloy was fatigue fracture, and the fretting wear damage of the inner surface of lug hole was the main reason for the fatigue crack initiation. This case is a typical example of titanium alloy structure failure due to fretting wear, which provides reference for the prevention of the recurrence of such faults.

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Fatigue crack propagation behavior of Ni-based superalloys after overloading at elevated temperatures

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Progress in Natural science:materials International 2016年第2期26卷 197-203页

作者： Xinyue Huang Liang Wang Yunming Hu Guangping Guo David Salmon Ying Li Wenxia Zhao National Key Laboratory of Science and Technology on Advanced High Temperature Structural Materials Beijing Institute of Aeronautical Materials MTS Systems Corporation Eden Prairie 3. Beijing Key Laboratory of Aeronautical Materials Testing and Evaluation Beijing Institute of Aeronautical Materials

The fatigue crack propagation behavior of three superalloys subjected to a single overloading at elevated temperatures was investigated. The fatigue crack propagation rate FCPR versus stress intensity factor range data da/dN—ΔK were calculated using the two-point secant method. It was found that the crack growth rates of the investigated materials were retarded after overloading with an overload ratio R OL=1.6. The size of the plastic zone in the front of the crack tip and its relation to loading level were discussed. The overload retardation effects are attributed to crack closure. The fatigue damage in the plastic zone can also be a factor to explain the overload retardation.

关键词： High temperature fatigue Fatigue crack propagation rate Overloading Crack closure Superalloys

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