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Influence of Shim Layers on Progressive Failure of a Composite Componentin Composite-Aluminum Bolted Joint in Aerospace Structural Assembly

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Transactions of Nanjing University of Aeronautics and Astronautics 2018年第1期35卷 188-202页

作者： Cephas Yaw Attahu An Luling Li Zhaoqing Gao Guoqiang Department of Aerospace Manufacturing Engineering Jiangsu Key Laboratory of Precision and Micro-Manufacturing TechnologyNanjing University of Aeronautics and AstronauticsNanjing 210016P.R.China AVIC Xi′an Aircraft Industry(Group)Company LTD Xi′an 710089P.R.China

The influence of varying shim layers on the progressive damage/failure of a composite component in a Bolted composite-aluminum aerospace structural assembly was investigated using a non-linear three-dimensional(3 D)structural solid elements assembled model of a carbon fiber-reinforced polymer(CFRP)-aluminum single-lap joint with a titanium(Ti-6 Al-4 V)fastener and a washer generated with the commercial finite element(FE)software package,ABAQUS/Standard.A progressive failure algorithm written in Fortran code with a set of appropriate degradation rules was incorporated as a user subroutine in ABAQUS to simulate the non-linear damage behavior of the composite component in the composite-aluminum Bolted aerospace structure.The assembled 3 DFE model simulated,as well as the specimen for the experimental testing consisted of a carbon-epoxy IMS-977-2 substrate,aluminum alloy 7075-T651 substrate,liquid shim(Hysol EA 9394),solid peelable fiberglass shim,a titanium fastener,and a washer.In distinction to previous investigations,the influence of shim layers(liquid shim and solid peelable fiberglass shim)inserted in-between the faying surfaces(CFRP and aluminum alloy substrates)were investigated by both numerical simulations and experimental work.The simulated model and test specimens conformed to the standard test configurations for both civil and military standards.The numerical simulations correlated well with the experimental results and it has been found that:(1)The shimming procedure as agreed upon by the aerospace industry for the resolution of assembly gaps in Bolted joints for composite materials is the same for a composite-aluminum structure;liquid shim series(0.3,0.5 and 0.7 mm thicknesses)prolonged the service life of the composite component whereas a solid peelable fiberglass shim most definitely had a better influence on the 0.9 assembly gap compared with the liquid shim;(2)The shim layers considerably influenced the structural strength of the composite component by delaying its ultimate failure thereby increasi

关键词： composite-aluminum progressive failure modeling finite element modeling single-lap Bolted joint shimming aerospace structures

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A global-local finite element analysis of hybrid composite-to-metal Bolted connections used in aerospace engineering

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Journal of Central South University 2017年第6期24卷 1225-1232页

作者：梁珂 Qian Xuesen Laboratory of Space Technology China Academy of Space TechnologyBeijing 100094China Faculty of Aerospace Engineering Delft University of TechnologyDelft 2629HSthe Netherlands

Efficient Bolted joint design is an essential part of designing the minimum weight aerospace structures, since structural failures usually occur at connections and interface. A comprehensive numerical study of three-dimensional(3D) stress variations is prohibitively expensive for a large-scale structure where hundreds of bolts can be present. In this work, the hybrid composite-to-metal Bolted connections used in the upper stage of European Ariane 5ME rocket are analyzed using the global-local finite element(FE) approach which involves an approximate analysis of the whole structure followed by a detailed analysis of a significantly smaller region of interest. We calculate the Tsai-Wu failure index and the margin of safety using the stresses obtained from ABAQUS. We find that the composite part of a hybrid Bolted connection is prone to failure compared to the metal part. We determine the bolt preload based on the clamp-up load calculated using a maximum preload to make the composite part safe. We conclude that the unsuitable bolt preload may cause the failure of the composite part due to the high stress concentration in the vicinity of the bolt. The global-local analysis provides an efficient computational tool for enhancing 3D stress analysis in the highly loaded region.

关键词： Bolted connection global-local finite element approach failure bolt preload

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Numerical and Experimental Study on Stiffened Composite Panel Repaired by Bolted Joints under Compressive Load

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Journal of Applied Mathematics and Physics 2018年第8期6卷 1763-1771页

作者： Jifeng Xu Yuanpei Lan Xingming Zhang Kui Du Beijing Key Laboratory of Civil Aircraft Structures and Composite Materials Beijing Aeronautical Science & Technology Research Institute Beijng China

Numerical and experimental study was conducted to investigate the failure mode and strength performance of stiffened composite panel repaired by Bolted joints under compressive load, and the results were then compared with those from virgin stiffened composite panel without any damage. A finite element analysis model was established for repaired and virgin stiffened composite panels under compressive load, the 3D Hashin criteria was applied to identify the composite structure failure, and the secondary stress criteria was adopted to identify the adhesive failure between the base laminate and the stiffener. The failure modes of repaired stiffened composite panels were stiffened composite panels breaking off along the bolt joints. The experimental results were consistent with the finite element analysis results, indicating the reliability of the finite element analysis model.

关键词： Stiffened Composite Panel Bolted Joints Repair Compression Performance 3D Finite Element Model

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Nonlinear interval analysis of rotor response with joints under uncertainties

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Chinese Journal of Aeronautics 2020年第1期33卷 205-218页

作者： Yanhong MA Yongfeng WANG Cun WANG Jie HONG School of Energy and Power Engineering Beihang UniversityBeijing 100083China Collaborative Innovation Center of Advanced Aero-Engine Beijing 100083China

The dynamic influence of joints in aero-engine rotor systems is investigated in this paper.Firstly,the tangential stiffness and loss factor are obtained from an isolated lap joint setup with dynamic excitation experiments.Also,the influence of the normal contact pressure and the excitation level are examined,which revel the uncertainty in joints.Then,the updated Thin Layer Elements(TLEs)method with fitted parameters based on the experiments is established to simulate the dynamic properties of joints on the interface.The response of the rotor subjected to unbalance excitation is calculated,and the results illustrate the effectiveness of the proposed method.Meanwhile,using the Chebyshev inclusion function and a direct iteration algorithm,a nonlinear interval analysis method is established to consider the uncertainty of parameters in joints.The accuracy is proved by comparison with results obtained using the Monte-Carlo method.Combined with the updated TLEs,the nonlinear Chebyshev method is successfully applied on a finite model of a rotor.The study shows that substantial attention should be paid to the dynamical design for the joint in rotor systems,the dynamic properties of joints under complex loading and the corresponding interval analysis method need to be intensively studied.

关键词： Aero-engine Bolted joints Nonlinear interval analysis method Rotor dynamics Uncertainties Updated Thin Layer Elements(TLE)method

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Stress Analysis of Bolted Joints Part II. Contact and Slip Analysis of a Four Bolt Joint

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Modern Mechanical Engineering 2014年第1期4卷 46-55页

作者： László Molnár Károly Váradi János Holubán Andor Tamási Department of Machine and Product Design Budapest University of Technology and Economics Budapest Hungary

For up-to-date Bolted joints, first of all in vehicles, high strength bolts of 10.9 or even 12.9 are used, which are preloaded up to 90% or even 100% of the yield strength. The primary aim of this high degree utilization is the weight reduction. For the analytic dimensioning of Bolted joints, the VDI 2230 Richtlinien German standard [1] provides support. However, the analytic model can mostly consider the true structural characteristics only in a limited way. The analytic modeling is especially uncertain in case of multiple Bolted joints when the load distribution among the bolts depends reasonably upon the elastic deformation of the participating elements in the joints over the geometry of the Bolted joint. The first part of this paper deals with the problems of numerical modeling and stress analysis, respectively specifying the analytic dimensioning procedure by applying elastic or rather elastic-plastic material law. The error magnitude in Bolted joint calculation was examined in case of omitting the existing threaded connection—between the bolt and the nut—in order to simplify the model. The second part of the paper deals with the dimensioning of stands and cantilevers’ multi-bolt fixing problems, first of all, with the load distribution among the bolts keeping in view the analysis of the local slipping relations. For demonstrating the above technique, an elaborated numeric procedure is presented for a four-Bolted cantilever, having Bolted joints pre-tightened to the yield strength.

关键词： Bolted Joints Numerical Modeling Stress Analysis

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Stress Analysis of Bolted Joints Part I. Numerical Dimensioning Method

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Modern Mechanical Engineering 2014年第1期4卷 35-45页

作者： László Molnár Károly Váradi Balázs Liktor Department of Machine and Product Design Budapest University of Technology and Economics Budapest Hungary

For up-to-date Bolted joints, first of all in vehicles, high strength bolts of 10.9 or even 12.9 are used, which are pre-tightened up to 90% or even 100% of the yield strength. The primary aim of this high degree utilization is the weight reduction. For the analytic dimensioning of Bolted joints, the VDI 2230 Richtlinien German standard provides support. However, the analytic model can mostly consider the true structural characteristics only in a limited way. The analytic modeling is especially uncertain in case of multiple Bolted joints when the load distribution among the bolts depends reasonably upon the elastic deformation of the participating elements in the joints over the geometry of the Bolted joint. The first part of this paper deals with the problems of numerical modeling and stress analysis, respectively specifying the analytic dimensioning procedure by applying elastic or rather elastic-plastic material law. The error magnitude in Bolted joint calculation was examined in case of omitting the existing threaded connection—between the bolt and the nut—in order to simplify the model. The second part of the paper deals with the dimensioning of stands and cantilevers’ multi-bolt fixing problems, first of all, with the load distribution among the bolts keeping in view the analysis of the local slipping relations. For demonstrating the above technique, an elaborated numeric procedure is presented for a four-Bolted cantilever, having Bolted joints pre-tightened to the yield strength.

关键词： Bolted Joints Numerical Modeling FE Stress Analysis

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The Simple Model for Bolted Connections in Fire

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Engineering（科研） 2011年第9期3卷 865-875页

作者： Mahmoud Yahyai Mohsen Behzadpoori Amir Saedi Daryan Ahmad Baleh Moghadas Civil Engineering Department K. N. Toosi University of Technology

Recent structural collapses caused by fire have focused attention on research concerning fire safety in building design. Steel connections are an important component of any structural steel building as they provide links between the principal structural members. Considering the importance of this matter this paper describes a spring-stiffness model developed to predict the behavior of Bolted angle connections bare-steel joints at elevated temperature. The joint components are considered as springs with predefined mechanical properties i.e. stiffness and strength. The elevated temperature joint’s response can be predicted by assem-bling the stiffness of the components which are assumed to degrade with increasing temperature based on the recommendations presented in the design parameters code. Comparison of the results from the model with existing experimental data showed good agreement. The proposed model can be easily modified to describe the elevated temperature behavior of other types of joint as well as joints under large rotations.

关键词： Bolted Connection Elevated-Temperature Fire Spring-Stiffness Model Rotation-Temperature Curves Moment-Rotation Curves

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Research Review of Principles and Methods for Ultrasonic Measurement of Axial Stress in Bolts

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Chinese Journal of Mechanical Engineering 2020年第1期33卷 44-59页

作者： Qinxue Pan Ruipeng Pan Chang Shao Meile Chang Xiaoyu Xu School of Mechanical Engineering Beijing Institute of TechnologyBeijing 100081China Key Laboratory of Fundamental Science for Advanced Machining Beijing Institute of TechnologyBeijing 100081China

Bolts are important fasteners indispensable in the manufacturing field for their advantages, which include convenient assembly and disassembly, easy maintenance, refastenability to prevent looseness, and the avoidance of a phase change in the connected material composition. The precise control of the tightening force in bolts is closely related to the safety and reliability of the connected equipment or structure. Although there are many methods for estimating the tightening force applied to a bolt during assembly, poor accuracy in controlling the preload during the tightening process and a lack of monitoring to determine the residual axial force in service remain issues in evaluating the safety of Bolted assemblies. As a nondestructive testing technology, ultrasonic measurement can be applied to successfully address these issues. In order to help researchers understand the theoretical basis and technological development in this field and to equip them to conduct further in-depth research, in this review, the basic knowledge describing the state of stress and deformation of bolts, as well as conventional testing methods are summarized and analyzed. Then, through a review of recent research of the ultrasonic measurement of the axial stress in bolts, the influence of the e ective stressed length and temperature are analyzed and proposed methods of calibration and compensation are reviewed. In order to avoid coupling errors caused by traditional piezoelectric transducers, two newly proposed ultrasonic coupling technologies, the electromagnetic acoustic transducer(EMAT) and the permanent mounted transducer system(PMTS), are reviewed. Finally, the new direction of research of the detection of residual axial stress in in-service bolts that have been assembled to yield is discussed.

关键词： Bolted connections Axial stress Ultrasonic waves Influencing factors Coupling techniques

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Some Advances in the Application of Weathering and Cold-Formed Steel in Transmission Tower

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Journal of Electromagnetic Analysis and Applications 2009年第1期1卷 24-30页

作者： Fengli Yang Junke Han Jingbo Yang Zheng Li China Electric Power Research Institute Beijing China

Application of weathering and cold-formed steel in transmission lines can reduce steel consumption and environmental pollution. Some advances in the studies on the weathering and cold-formed steel in transmission tower are introduced. Firstly, corrosion-resistant tests of weathering steel samples under different simulating technical atmospheres were carried out separately for 240 hours. It shows that the corrosion degree of joint samples is higher than that of single chip samples, and the corrosion-resistant performance of weathering steel is superior to common carbon steel. The corrosion-resistance of weathering steel meets with the requirement of transmission tower. Secondly, experiments and finite element analysis for cold-formed angles and a 220kV prototype tower were completed, and the stability coeffi-cient fitting curves as well as the modification formulas of slenderness ratio for cold-formed members were determined. According to the structural characteristics of transmission towers, four sections of cold-formed angles with different sections and slenderness ratios were selected in this study. The finite element model well predicted the buckling behav-iour of the cold-formed members. Ultimate loads calculating by the fitting curve were well agreed to the experimental values, especially for the members with small slenderness ratios. Weight of the cold-formed steel tower can be reduced by more than 5 percent after considering the strength enhancement. Cost of the weathering and cold-formed steel transmission tower is nearly equivalent to that of hot-rolled steel tower with hot galvanizing.

关键词： Weathering Steel Cold-Formed Steel Bolted Joint Corrosion-Resistant Test Prototype Test Buckling Analysis Transmission Tower

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