Cumulative Damage Theory Research Articles

Method of electrical connector intermittent fault reproduction

PurposeThis paper aims to reproduce the electrical connector intermittent fault behaviours with step-up vibration stress while maintaining the integrity of the product. Design/methodology/approachA dynamic model of an electrical connector under vibration is established for contact resistance analysis. Next, the dynamic characteristics of contact resistance are analysed, and cumulative damage theory is used to calculate the damage under different stresses during the intermittent fault reproduction test. To reduce damage and improve efficiency, the step-up stress is used for the reproduction test. FindingsThe proposed method can reproduce the intermittent fault behaviour, and the step-up stress test is more efficient than the constant stress test. Research limitations/implicationsStep-up stress is used for intermittent fault reproduction, and the quantitative relationships between intermittent fault and product damage can be further studied. Practical implicationsIt is expected that the proposed methodology can help engineers to reproduce the intermittent fault behaviours to facilitate the detection and diagnosis of intermittent fault and to improve equipment safety. Originality/valueThe mechanism of electrical connector reproduction is analysed and the step-up stress test is used for intermittent fault reproduction.

Research on Pin-load Distribution for Countersunk Joint Considering Accumulated Damage of Composite Laminates

The paper presents a numerical simulation about the damage process of the multiple countersunk bolted double-lap joints based on the cumulative damage theory which is widely used to estimate the mechanical strength of fastener joints, the Hashin’s failure criterion, and the Tan’s stiffness degradation model, and investigates the influence of the composite materials cumulative damage on the pin-load distribution. The numerical model of composite joints has been established in the commercial finite element software ANSYS to research the influence of the composite cumulative damage on the pin-load distribution, to assess the feasibility of integral analysis as well as to evaluate the error and rationality of traditional methods by applying the global analysis technology. The conclusions demonstrate that the results obtained with the method of composite cumulative damage considering properties degradation are close to those of conventional methods. The pin-load distribution is characterized by “Bolts at both ends bearing greater load, the central bolts bearing smaller load” during the whole loading process. Using conventional methods to study the pin-load distribution is easy and efficient to meet the needs of engineering application.

Fatigue Performance Evaluation of Existing Concrete Girder Bridges

Main steel bars and prestressed strands in critical parts of existing concrete girder bridges are at risk of fatigue and fracture under the combined action of heavy truck loads, increased traffic volume and the effects of environmental corrosion. Based on cumulative damage theory and fracture mechanics, this paper proposes a framework for evaluating the fatigue performance of existing concrete girder bridges. The evaluation framework contains four steps: investigation of the bridge archives; detection, monitoring and simulation; fatigue performance evaluation; and implementation of the maintenance and management recommendations. A combination of acoustic emission and weigh-in-motion (WIM) technologies was adopted to acquire vehicle information and evaluate girder performance, and a Monte Carlo method and function fitting were also applied to calculate a fatigue reliability index. The results of the evaluation indicate that the case-study bridge is extremely unlikely to fail as the result of fatigue during the design service life. In addition, the parameter analysis shows that the fatigue reliability of concrete bridges is sensitive to the combined effects of negative factors. The reliability index curve and the target value of the reliability index can be used to determine the recommended fatigue inspection intervals and the limits for the initial crack size in critical steel bars.

Study on the Pin-load Distribution of Composite Joints with Protruding-head Bolts Based on Cumulative Damage

This paper presents the investigation of the pin–load distribution law of composite mechanical joints with protruding-head bolts based on the theory of composite cumulative damage. The three-dimensional finite element analysis have been carried out by using the software ANSYS for the composite plates connected with protruding-head bolts. The friction on the contact surfaces of the composite joints, and the nonlinearity of the contact state and the preload on the bolts have been considered. The effect law of cumulative damage on the pin-load distribution of multiple-bolted joints has been achieved. The results manifest that the proportion of the pin-load distribution varies with the external load and is slightly different at diverse stages of loading considering the cumulative damage of the composite materials, that pin load at both ends is greater than in the middle.

Lightweight design of gears in the wheel-side reducer based on Shanghai road driving cycle

The development of wheel-side reducer with proper durability is important for electric vehicles equipped with a wheel-side reducer system. Based on the Shanghai road driving cycle, a novel conversion method is proposed from vehicle speed to load, which provides a theoretical foundation for lightweight design and a durability analysis of the key components of the wheel-side reducer system. With the gears of the wheel-side reducer as an example, an electric drive system durability test specification is also developed on the basis of the Miner linear cumulative damage theory considering the material strengthening under low-amplitude loads. The durability test shows that the second round of the prototype design no longer has an infinite life compared with the first round of the prototype design. The method based on active load spectrum is more effective than the traditional design method.

Research on extending the fatigue life of railway steel bridges by using intelligent control

This paper investigates the potential of a vibration control-inspired method towards extending the fatigue life of railway steel bridges. Based on coupled thermal-mechanical and vehicle-track analysis, both the residual stresses from welding and these from traffic on the bridge are obtained. Subsequently, a multi-scale approach with a shell Finite Element (FE) model of the whole bridge and a solid FE model of its critical joints is put forward. The equation of motion is established for the controlled bridge, equipped with a Magnetorheological-Tuned Mass Damper (MR-TMD) system, while the combination of excitation, welding and control effects is practiced through own-developed packages and commercial software sub-model routines. The framework is showcased for the study of the Poyang Lake Railway Bridge in China. After obtaining the controlled stress states at the critical welded joint, the fatigue crack initial life is evaluated by using the critical plane method and the linear cumulative damage theory. Simulation results indicate that the multi-scale modelling approach followed, meets the accuracy needs for capturing the cracking process of the welded joint with high computational efficiency. The MR-TMD system, even when moderately reducing the critical joint stress amplitudes, can improve substantially the overall bridge fatigue resistance over the uncontrolled structure.

The Fatigue Life Prediction of Train Wheel Rims Containing Spherical Inclusions

It is a common phenomenon that fatigue crack initiation occurs frequently in the inclusions of wheel rims. Research on the fatigue life of wheel rims with spherical inclusions is of great significance on the reliability of wheels. To find the danger point and working condition of a wheel, the stress state of the wheel rim with spherical inclusions was analyzed using the finite element method. Results revealed that curve conditions are dangerous. The critical plane method, based on the cumulative fatigue damage theory, was used to predict the fatigue life of the wheel rim and whether it contained spherical inclusions or not under curve conditions. It was found that the fatigue life of the wheel rim is significantly shorter when the wheel rim contains spherical inclusions. Analysis of the results can provide a theoretical basis and technical support for train operations and maintenance.

Wind‐induced fatigue of large HAWT coupled tower–blade structures considering aeroelastic and yaw effects

SummaryAn efficient approach for predicting wind‐induced fatigue in large horizontal axis wind turbine coupled tower–blade structures subject to aeroelastic and yaw effects is presented. First, aerodynamic loads under yaw conditions are simulated based on the harmonic superposition method and modified blade element momentum theory, in which wind shear, tower shadow, tower–blade interactions, aeroelastic, and rotational effects are taken into account. Then, a nonlinear time‐history of wind‐induced responses under simulated aerodynamic loads is obtained. Finally, based on these results, wind‐induced fatigue damage and lifespan are predicted according to linear cumulative damage theory. For completeness, the influences of mean wind speed, aeroelasticity, and yaw angle on horizontal axis wind turbine fatigue life are discussed. The results indicate that the aerodynamic loads and residual fatigue life can be estimated accurately by the proposed model, which can be used to simulate the 3D wind fields of wind turbines under given wind conditions. The wind energy of the wind turbine blade is mainly concentrated at its edge and is weaker at the hub. Estimation of wind turbine fatigue life is therefore suggested to be based on the component with the shortest life, being the blade root. Furthermore, yaw conditions significantly shorten fatigue life and should not be ignored. Fatigue life is also rather sensitive to mean wind speed.

Fatigue Analysis of Mobile Maintenance Platform Based on Ansys Workbench

In order to investigate the performance of the mobile maintenance platform, Ansys Workbench was used to analyze the strength analysis of the mobile maintenance platform. The deformation, stress, and strain were obtained. The fatigue module was used to analyze the fatigue of the mobile maintenance platform and the fatigue life based on the cumulative fatigue damage theory. The simulation results show that the strength of the mobile maintenance platform is sufficient, and its lifetime is as high as 19.8 years. The mobile maintenance platform has a large space for optimization and this paper provides a basis for future structural optimization design.

RETRACTED: Fatigue property study and life assessment of composite girders with two corrugated steel webs

This paper presents the results of experimental investigations on fatigue behaviors of composite girders with corrugated steel webs (hereafter referred to as “composite girders”) subjected to bending based on the experimental work on the shear connector and corrugated steel beam. The experimental results indicated that failure started with cracks initiation and propagation at the concrete bottom plate, with the ultimate failure mode characterized as the shear failure on the bottom plate and interfacial slippage between the web and bottom plate. There was no obvious reduction in stiffness when the fatigue life approached 6 × 106 (equiamplitude load) or 2 × 106 (variable amplitude load) cycles, and the cracks grew slowly, which exhibited good fatigue resistance under the cyclic loading at quasi-static load. In addition, the cracks initiation location and fatigue life are predicted based on the fatigue damage theory, which shows good agreements with test results. The C degree of American standard AASHTO2004 is also suggested to be used in the fatigue life design of corrugated steel web in composite girders. The Palmgren-Miner cumulative linear damage theory is adopted in the partial fatigue life assessment, the fatigue life of box girder subjected to variable amplitude cyclic load is predicted when D exceeds 1. In addition, the fracture extension theory by Paris and amplitude theory of stress intensity factors are summarized to assess the fatigue life, which can be good evidence contributing to the engineering practice.

Reliability analysis of wind turbines under non‐Gaussian wind load

SummaryBased on translation models, both Gaussian and non‐Gaussian wind fields are generated using the harmony superposition method for examining the reliability of a typical wind turbine at operational and parked conditions. Using the blade aerodynamic model and multibody dynamics, wind turbine responses are calculated and then probability characteristics are analyzed in details. The short‐term extreme response distribution is estimated by the average conditional exceedance rate method at each mean wind speed bin, and the long‐term extreme response distribution is then determined by further integrating the short‐term extreme response distribution conditional on wind speed with the distribution of mean wind speed. Additionally, crack initiation life and crack propagation life are evaluated using the linear cumulative damage theory and linear crack propagation theory, respectively. The results indicate that non‐Gaussian characteristics of wind inflows have a noticeably greater influence on both extreme response and fatigue damage, and the Gaussian assumption cannot suit wind turbine in complex terrain.

Aggregate fatigue failure on macro texture polishing of asphalt pavement

The macro-texture of asphalt pavement greatly affects the traffic safety of driving. In this study, the 3D laser scanning data, which is captured from the pavements, is used for reverse modeling. FE software ANSYS is used to analyze the contact stress distribution of pavement macro-texture and tire. The results show that the macro texture will be affected by fatigue failure considering the size effect of coarse aggregate. The fatigue life distribution of pavements is analyzed using the fatigue analysis software FE-SAFE which is based on linear cumulative damage theory. The developing tendency of texture depth with respect to the number of loading times is obtained by analyzing the results of fatigue life. Compared with the results of accelerated loading test shows that the factor of fatigue failure has remarkably affected the macro texture under low loading times. This effect is gradually decreased with the increasing of cyclic loading times.

Fatigue life prediction of wire rope based on stress field intensity method

Abstract In the paper, on the basis of the stress field intensity method, the internal complex wingding structure of 6 × 31SW + FC type wire rope is analyzed and calculated. As a first step, considering the weakening speed of weight function in the stress field intensity method is too fast, a modification is presented to make it more suitable for the calculation of the fatigue life of wire rope. The load spectrum of the critical locations of wire rope is then established, based on the Costello mechanical model and the actual working conditions. Through the stress field intensity method, the time history curve of stress field is then obtained. Subsequently, the fatigue life of wire rope is calculated by using the linear cumulative damage theory of fatigue. The wire rope fatigue test rig is established, and the experimental value of the fatigue life of wire rope is compared with the theoretical calculation value. The results show that the experimental load of 90 t is the demarcation point of high and low cycle fatigue of wire rope, the theoretical values and the test results are close to each other in the fatigue cycle, which proves the effectiveness of the stress field intensity method in predicting the fatigue life of the wire rope.

Gradient approach for the evaluation of the fatigue limit of welded structures under complex loading

Welded ‘T-junctions’ are tested at different load ratio for constant and variable amplitude loading. Fatigue results are analyzed through the type of fatigue mechanisms depending on the loading type. A gradient approach (WSG: Welded Stress Gradient) is used to evaluate the fatigue limit and the comparison with experimental results shows a relative good agreement. Nonlinear cumulative damage theory is used to take into account the variable amplitude loading.

An experimental and theoretical fatigue study on macro fiber composite (MFC) under thermo-mechanical loadings

Macro fiber composite (MFC) is widely used for various applications especially in the area of sensors, actuator, structural health monitoring and vibration control due to its improved electro-mechanical coupling and flexibility. While being used for these applications, the MFCs might be subjected to cyclic mechanical load at various operating temperatures leading to the deterioration in the sensing performance. Hence, to study the life of the MFCs (d31 & d33 type) as a sensor, an experimental setup is devised and tests are performed for various thermo-mechanical loading conditions. Experiments involve huge investment in terms of cost and time. Therefore, in the present work, a theoretical model consisting of non-linear finite analysis integrated with the cumulative damage theory is derived to predict the fatigue behaviour of the MFC. The degradation in the piezoelectric coupling coefficient obtained using the present model is able to capture the non-linear trend observed from the experimental observations and the values are in good comparison. The non-linear FE model is also extended to predict the degradation of stiffnesses and strengths of the MFCs due to various thermo-mechanical loading conditions.

Spectral Method for Fatigue Damage Assessment of Structures with Uncertain Parameters

This study presents a spectral method for fatigue damage evaluation of linear structures with uncertain-but-bounded parameters subjected to the stationary multi-correlated Gaussian random excitation. The first step of the proposed method is to model uncertain parameters by introducing interval theory. Within the framework of interval analysis, the approximate expressions of the bounds of spectral moments of generic response are obtained by the improved interval analysis via the Extra Unitary Interval and Interval Rational Series Expansion. Based on the cumulative damage theory and the Tovo-Benasciutti method, the lower and upper bounds of expected fatigue damage rate are accurately evaluated by properly combining the bounds of the spectral parameters of the power density spectral function of stress of critical points. Finally, a numerical example concerning a truss under random excitation is used to illustrate the accuracy and efficiency of the proposed method by comparing with the vertex method.

Fatigue study on the sensor performance of macro fiber composite (MFC): Theoretical and experimental approach

Due to its high flexibility and enhanced electro-mechanical coupling, macro fiber composite (MFC) is widely used in the area of sensing, vibration control and structural control. While in application, MFCs are subjected to continuous cyclic mechanical load which may lead to the deterioration of piezoelectric coupling coefficient, thereby affecting its sensing performance. In order to predict the life cycle of MFC (d31&d31 type) subjected to mechanical loading, an experimental setup has been devised and the tests are carried out for various loading conditions. For lowering the effort and cost involved in the experiments, a non-linear finite element model along with cumulative damage theory is introduced. The degradation in the piezoelectric coupling coefficient obtained using the current theoretical model are in good comparison with the experimental observations. The current non-linear FE model is also extended to predict the stiffnesses and strengths of the MFC as a function of fatigue cycles.

宇航单机元器件随机振动疲劳分析

宇航单机在生命周期内要经历各种振动环境，在随机振动过程中，单机内的敏感元器件容易疲劳破坏而出现管脚断裂或焊点脱落。文章针对某型号宇航单机元器件管脚断裂情况，对其结构及元器件的几何模型进行了详细的有限元分析，获得随机振动工况下的均方根应力场，应用Miner疲劳损伤累计理论及三带宽技术，进行元器件管脚的疲劳分析，并对结构进行优化，再次分析得知结构改进后单机的疲劳安全裕度得到很大提高且通过了试验验证。结果表明了该疲劳分析方法的有效性。 The aerospace electronic equipment undergoes a variety of vibration environments throughout its life cycle. In the process of random vibration, the sensitive chips in the electronic equipment are prone to fatigue failure, and the fracture of the pins or the welding joints are broken out. In this paper, the fracture of the pin of the aerospace electronic equipment is discussed, and a de-tailed finite element analysis of the geometric model of the equipment structure and chips is car-ried out to obtain RMS stress field under random vibration conditions, and Miner’s cumulative fatigue damage theory and three bandwidth technique are used to analyze the fatigue of chips and its pins. After the structure optimization of the equipment, a detailed finite element analysis of the geometric model of the equipment structure and chips showed that the optimized structure safety margin has been greatly improved and verified by test. The results show that this method is an effective method for random vibration fatigue analysis of the aerospace electronic equipment.

Fatigue Analysis of Large-scale Wind turbine

The paper does research on top flange fatigue damage of large-scale wind turbine generator. It establishes finite element model of top flange connection system with finite element analysis software MSC. Marc/Mentat, analyzes its fatigue strain, implements load simulation of flange fatigue working condition with Bladed software, acquires flange fatigue load spectrum with rain-flow counting method, finally, it realizes fatigue analysis of top flange with fatigue analysis software MSC. Fatigue and Palmgren-Miner linear cumulative damage theory. The analysis result indicates that its result provides new thinking for flange fatigue analysis of large-scale wind turbine generator, and possesses some practical engineering value.

Study on fatigue damage characteristics of deformable mirrors under thermal-mechanical coupling effect.

In a wavefront correction process, both the mechanical effect and the irradiation of a high-power continuous-wave laser distort the deformable mirror (DM) surface, which inevitably speeds up the fatigue damage of the DM. By utilizing the stress analysis model for the fatigue damage of the DM, the fatigue damage effects are analyzed quantitatively on the consideration of thermal-mechanical coupling effects, and the fatigue life prediction model has further been proposed based on the S-N curve and Miner cumulative damage theory. On this basis, thermal-mechanical conditions have been analyzed, and the influence of laser parameters on the fatigue life of the DM has also been discussed in detail. The results indicate that the increasing of maximum temperature rise of the DM leads to the increasing of stress, and further brings about the decreasing of the fatigue life. Meanwhile, the position at the rear surface of the DM subjected to the maximum stress always presents the minimum fatigue life. Furthermore, the laser irradiation makes the DM more easily damaged when the DM is correcting a distorted wavefront, and the fatigue life decreases with the increasing of irradiation time and power density for a given peak and valley (PV) value of the corrected wavefront. Additionally, the fatigue life also decreases with the increasing of power density and the decreasing of spot radius for a certain total irradiation. On the other hand, for the given laser parameters, the influence of the mechanical effect on fatigue life is gradually apparent with increasing PV value of the corrected wavefront, and when the PV value is more than 2λ, the mechanical effect instead of the thermal effect becomes the key factor for fatigue damage of the DM.