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Yan W.M.,Zhejiang University | Bi Y.B.,Zhejiang University | Fan X.T.,Xian Aircraft International Corporation | Du K.P.,Xian Aircraft International Corporation | Wang W.,Xian Aircraft International Corporation
Applied Mechanics and Materials | Year: 2013

This paper firstly establishes a finite element model of a fuselage panel, and then an assembly variation model is derived from the method of influence coefficients (MIC) and principal component analysis (PCA). With the calculation of Fisher information matrix and effective independence (EFI), 49 measurement points are extracted from a number of finite element nodes by the optimum selection method, and the mathematical relation between the position errors of measurement points and the positioning errors of frames is established, which is utilized to analyze the impact of positioning errors of each frame on fuselage panel assembly variation. Finally, the key frame that is important to ensure assembly accuracy and to improve the assembly process is determined. © (2013) Trans Tech Publications, Switzerland.


Wang Q.,Aerospace Research Institute of Materials And Processing Technology | Zhang W.,Xian Aircraft International Corporation | Qiao M.-J.,Xian Aircraft International Corporation
Cailiao Gongcheng/Journal of Materials Engineering | Year: 2013

The effect of compressive residual stress and plastic strain induced by shot peening processing on bending deformation (BD) of 7150 aluminum alloy was studied using the XRD residual stress testing and the FWHM value. The results indicate that BD rate is higher when the shot time is less than 60s, and the BD rate reaches 10.3 μm/s when shot pressure is 0.05 MPa, due to the compressive residual stress and plastic strain induced by shot peening processing. When the shot time is more than 60 s, the compressive residual stress field reaches saturated, and the BD rate reduces to 1.3 μm/s which only depends on the surface plastic defomation induced by shot peening processing. The BD rate and total amount of BD increase with the increasing of shot pressure.


Du D.,Northwestern Polytechnical University | Liu D.,Northwestern Polytechnical University | Meng B.,XiAn Aircraft International Corporation | Zhang X.,Northwestern Polytechnical University
Science China Technological Sciences | Year: 2013

The effects of grit blasting (GB), shot peening (SP) pretreatment and high velocity oxygen fuel(HVOF) sprayed WC-17Co cermet coating on the fatigue properties of the novel ultra-high strength TC21 titanium alloy were investigated with a rotating bending fatigue test machine. The basic properties and surface integrity of the coating were investigated by using X-ray diffraction (XRD), surface roughness meter, microscopic hardness tester, scanning electron microscopy (SEM) and X-ray stress test instruments. The results showed that the residual compressive stress could be introduced into the surface of TC21 alloy by GB and SP pretreatment, and that HVOF sprayed WC-17Co coating was compactly bonded with TC21 alloy substrate and it significantly improved the surface hardness of the substrate. However, there was a certain residual tensile stress in the sublayer of the coating. SP could significantly increase fatigue resistance of TC21 alloy due to the surface residual compressive stress. There was no significant effect on fatigue resistance by GB treatment due to the offset between the influence of surface residual compressive stress and the surface notch effect. The fatigue resistance of TC21 alloy was significantly reduced by HVOF WC-17Co coating prepared with GB pretreatment. This could be attributed to the relaxation of surface residual compressive stress during the HVOF heating process, pore defects and residual tensile stress distribution in the WC-17Co coating with low toughness, and the surface notch induced by GB. The fatigue resistance of TC21 alloy was slightly reduced by HVOF WC-17Co coating prepared with SP pretreatment. This was attributed to the offset between the advantage effect by SP and disadvantageous effect of WC-17Co coating and high temperature factor during the HVOF process. © 2013 Science China Press and Springer-Verlag Berlin Heidelberg.


Xiao X.D.,Northwestern Polytechnical University | Wang Y.J.,Northwestern Polytechnical University | Zhang W.,XiAn Aircraft International Corporation | Wang J.B.,Northwestern Polytechnical University | Wei S.M.,Northwestern Polytechnical University
Journal of Materials Processing Technology | Year: 2016

Stress peen forming is widely used in aerospace industry to form the thin components with complex geometry. In the stress peen forming, the prestressing condition is a critical factor that need to be precisely controlled. In this study, the effects of the prestress on the peening deformations are investigated by using static and dynamic simulations. A regularly parked four-shot model is used to study the interactions of adjacent shot treatments. To verify the finite element model with precisely controlled parameters, regularly indenting tests are adopted. The analytical results reveal that the tensile prestress enhances the shot dimple and the plastic region sizes. The contributions of the prestress to the induced bending moments and stretching forces are indicated with two scale factors. Comparison of the single-shot model and regular parked four-shot model shows the peening effects can be equivalent within certain averaging regions. The static and dynamic simulations are compared on dimple sizes and forming effects. Finally, the indenting and peening tests are carried out to verify the analytical results. © 2015 Elsevier B.V. All rights reserved.


Du D.,Northwestern Polytechnical University | Liu D.,Northwestern Polytechnical University | Sun Y.,Xian Aircraft International Corporation | Tang J.,Northwestern Polytechnical University | Zhang X.,Northwestern Polytechnical University
Advanced Materials Research | Year: 2012

In this paper, the influence of different machining methods (including rough turning, finish turning, and longitudinal polishing after finish turning) on rotating bending fatigue properties of TC21 which belonged to a new ultra high strength titanium alloy was studied. The influence of machining methods on surface integrity of TC21 titanium alloy was measured by using surface profile measurement, scanning electron microscopy, metallography microscope, micro-hardness instrument and X-ray diffraction residual stress analyzer. And fatigue fractography of specimens was further investigated. Then the mechanism of fatigue resistance which was affected by machining surface integrity was discussed. The results indicated that the fatigue life of finish turning and longitudinal polishing after finish turning was increased 3.96 times and 17.34 times compared with rough turning, respectively. The machining surface integrity had important influence on fatigue property of TC21 titanium alloy, which caused by the differences of surface roughness and texture as the dominant factors, and then the variation in surface micro-hardness, metallographic microstructure and the surface residual stress were not the main factors on three above-mentioned machining methods. By using longitudinal polishing after finish turning processing method for preparation of TC21 titanium alloy parts could ensure good surface integrity and excellent fatigue performance. © (2012) Trans Tech Publications.


Du D.,Northwestern Polytechnical University | Liu D.,Northwestern Polytechnical University | Xiang D.,Northwestern Polytechnical University | Meng B.,Xian Aircraft International Corporation | Zhang X.,Northwestern Polytechnical University
Lecture Notes in Electrical Engineering | Year: 2014

In this paper, the machining texture and shot peening (SP) on the fatigue properties of a high-strength TC18 titanium alloy for aviation were studied. The surface texture, surface morphology, hardness distribution, and residual stress characteristics of fatigue specimens were analyzed by using scanning electron microscopy (SEM), micro-hardness tester, and X-ray diffraction residual stress analyzer. The results showed that the fatigue life of the axial texture processing was 27 % lower than that of the axial polishing specimens (BM) . But circumferential texture processing was 72 % lower than that of BM. It was attributed that the fatigue cracks was initiation easily by circumferential texture processing. Then, SP technology was induced to repair the fatigue life of the circumferential texture processing specimens. Compared with the BM specimens, the fatigue life of SP specimens increased approximately 12 times. That was attributed to the depth of compressive residual stress field induced by SP. © 2014 Springer-Verlag.


Bi Y.B.,Zhejiang University | Jiang Y.H.,Zhejiang University | Li Y.C.,Zhejiang University | Wang W.,Xian Aircraft International Corporation | And 2 more authors.
Applied Mechanics and Materials | Year: 2013

The Flexible track automatic drilling equipment is widely used in aircraft assembly because of the low cost, high efficiency and high quality of holes. This paper constructs a new flexible track drilling system for large-size aircraft assembly. The system structure is introduced, and the transformation algorithm between product/device coordinate system and axes position parameters is proposed. The experimental results show that the transformation algorithm has the merits of high computational efficiency and high stability, and can meet the requirement of precision drilling. © (2013) Trans Tech Publications, Switzerland.


Liu T.,Northwestern Polytechnical University | Wang Y.,Northwestern Polytechnical University | Wu J.,Northwestern Polytechnical University | Xia X.,Northwestern Polytechnical University | And 3 more authors.
Journal of Materials Processing Technology | Year: 2015

The aluminum-lithium (Al-Li) bent extrusion products offer opportunities for significant improvements in structural performance due to its lightweight material and component. However, the high ratio of strength to Young's modulus may induce significant elastic recovery after unloading. The precise bending of the Al-Li alloys extrusion depends on the understanding of the springback features and mechanisms of the profile stretch bending process, which is a much complex physical process with multi-factors coupling interactive effects. For this purpose, the springback behaviors of the age-hardened 2196-T8511 and 2099-T83 Al-Li alloys extrusions with Z-section and T-section under displacement controlled cold stretch bending (DCSB) are investigated. Firstly, an analytical model is developed based on the radius of strain neutral layer and verified experiments are carried out. Secondly, the connector element in FEM is used to simulate DCSB. Furthermore, the roles of material, radius, process parameters and friction condition are revealed. Finally, springback control method is proposed to ensure the stabilization and precision of bending parts. The results show that: (1) The analytical model and finite element method can be used to evaluate effectively the effects of material and process parameters on springback of Al-Li alloys extrusions in DCSB. (2) 2196-T8511 and 2099-T83 Al-Li alloys extrusions show significant springback at room temperature because of its higher strength to Young's modulus. (3) Increasing pre-stretching or post-stretching strain can significantly reduce the radius springback and time-dependent springback of 2196-T8511 and 2099-T83 Al-Li alloys extrusions, but it is limited by the lower fracture strain. (4) The lubricant between extrusions with die reduces the stable radius springback ratio greatly for Al-Li alloys in the T8 temper. © 2015 Elsevier B.V. All rights reserved.


Du D.-X.,Northwestern Polytechnical University | Liu D.-X.,Northwestern Polytechnical University | Meng B.-L.,Xian Aircraft International Corporation | Zhang X.-H.,Northwestern Polytechnical University
Hangkong Cailiao Xuebao/Journal of Aeronautical Materials | Year: 2013

In order to investigate the effect of surface integrity of shot peening(SP), grit blasting(GB) and HVOF sprayed WC-17Co coating on the fatigue behavior of Ti5Al5Mo5V1Cr1Fe(TC18)alloy, the surface integrity of the surface treatment was evaluated by using X-ray diffraction (XRD), surface roughness meter, microscopic hardness tester, scanning electron microscopy (SEM) and X-ray stress test instrument. The fatigue property of TC18alloy influenced by above surface treatment was studied by using rotating bending fatigue test machine. The result indicates that the surface integrity after SP treatment is better than that after GB process. Therefore, the fatigue life of TC18titanium alloy increases dramatically by SP, but there is no significant change of fatigue life by GB treated TC18alloy. The fatigue life of HVOF WC-17Co coated TC18alloy with SP pretreatment is increased six times larger than that of the alloy substrate. This is attributed to the retained large residual compressive stress in the SP layer. The crack initiation and earlier propagation are delayed by the residual compressive stress. However, the fatigue life of HVOF WC-17Co coated TC18alloy with GB pretreatment is obviously decreased. This is due to the low toughness, large surface roughness, and pore defects of WC-17Co coating. The relaxation of residual compressive stress influenced by the HVOF high temperature process and the notch effect in GB layer are also the reasons.


Xiao X.,Northwestern Polytechnical University | Wang Y.,Northwestern Polytechnical University | Zhang W.,Xian Aircraft International Corporation | Wang J.,Northwestern Polytechnical University | Wei S.,Northwestern Polytechnical University
Procedia Engineering | Year: 2014

Stress peen forming is widely used to form the thin components with complex shapes in the aerospace industry. The prestress has an influence on the residual stress profiles, thereby influencing the peen forming forces: bending moment and stretching force for shaping the component. A static one-shot FE model was performed to investigate the residual stress profiles of single shot indenting under different prestresses and loads. A static four-shot FE model was performed to investigate the overlapping of the stress fields of adjacent shots indenting. The simulation results reveal that the tensile prestress enhances the indentation diameter and the plastic region size resulting in larger and deeper compressive residual stresses. The average peen forming forces of regular distributed four shots are four times the forming forces of one of shots when the separation distance of adjacent shots is larger than the plastic region size of one shot indenting. Experiments with different prebending arc heights and indenting gaps were carried out on aluminum alloy 2024-T351 strips with a developed Brinell hardness tester. The experimental results validated the simulation results. © 2014 The Authors. Published by Elsevier Ltd.

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