Analysis and Comparison of Safety and Fatigue Comfort of Postal Bicycles Based on Finite Element Method and sEMG

The safety and the fatigue comfort were compared between a domestic and a Japanese postal bicycle. Firstly, the fatigue comfort of these two kinds of bicycles was evaluated by surface electromyographic signal (sEMG) experiment, in which human lower limb muscle groups were research objects, and the average EMG (AEMG) index and median frequency (MF) were chosen as the evaluation indexes. Secondly, the safety of these two kinds of bicycle frames was analyzed and compared by using the finite element analysis. The results show that the riding fatigue comfort of the Japanese postal bicycle is better, and the Japanese postal bicycle frame is more safe and reasonable although both the postal bicycles meet the requirement for strength. Finally, based on the above analysis, the frame structure and related parameters of the domestic postal bicycle were improved with reference to the Japanese postal bicycle and biomechanics theory.

Optimum Autofrettage Pressure of Hydrogen Valve Using Finite Element and Fatigue Analysis

The presented article shows an estimation method of optimum autofrettage pressure taking into consideration subsequent cyclic loading. An autofrettage process is used in pressure vessel applications for strength improvement. The process relies on applying massive pressure that causes internal portions of the part to yield plastically, resulting in internal compressive residual stresses when pressure is released. Later applied working pressure (much lower than autofrettage pressure) creates stress reduced by the residual compressive stress improving the structural performance of the pressure vessels. The optimum autofrettage pressure is a load that maximizes the fatigue life of the structure at the working load. The estimation method of that pressure of a hydrogen valve is the subject of the presented work. Finite element and fatigue analyses were employed to investigate the presented problem. An automated model was developed to analyze the design for various autofrettage pressures. As the results of the procedure, the optimum autofrettage pressure is determined. The research has shown that the developed method can profitably investigate the complex parts giving the autofrettage load that maximizes the fatigue life. The findings suggest that the technique can be applied to a large group of products subjected to the autofrettage process.

Full－range nonlinear analysis of fatigue behaviors of reinforced concrete structures by finite element method

The offshore reinforced concrete structures are always subject to cyclic load, such as wave load.In this paper a new finite element analysis model is developed to analyze the stress and strain state of reinforced concrete structures including offshore concrete structures, subject to any number of the cyclic load. On the basis of the anal ysis of the experimental data,this model simplifies the number of cycles-total cyclic strain curve of concrete as three straight line segments,and it is assumed that the stress-strain curves of different cycles in each segment are the same, thus the elastoplastic analysis is only needed for the first cycle of each segment, and the stress or strain corresponding to any number of cycles can be obtained by superposition of stress or strain obtained by the above e lastoplastic analysis based on the cyclic numbers in each segment.This model spends less computer time,and can obtain the stress and strain states of the structures after any number of cycles.The endochronic-damage and ideal offshore concrete platform subject to cyclic loading are experimented and analyzed by the finite element method based on the model proposed in this paper. The results between the experiment and the finite element analysis are in good agreement,which demonstrates the validity and accuracy of the proposed model.

FINITE ELEMENT ANALYSIS TO THE FATIGUE STRENGTH OF SYNCHRONOUS BELT TEETH

By means of finite element analysis methods calculated the stress, strainand displacement of the belt teeth and analysisied the factors such as load distribution,specific property coefficient of material and temperature variation, which influence the fatigue strength of the belt teeth..

Finite element simulation and optimal analysis of surfacing on steel orthotropic bridge deck

To analyze the stress state of steel orthotropic deck pavement and provide reference for the design of the overlay, the inner stress state and strain distribution of surfacing under the load of the deformation of the whole bridge structure and tyre load are analyzed by the finite element method of submodeling. Influence of surfacing modulus on the strain state of the overlay is analyzed for the purpose of the optimal design of the overlay structure. Analysis results show that the deformation of the whole bridge structure has no evident influence on the stress state of the overlay. The key factor of the overlay design is the transverse tensile strain in the overlay above the upper edge of web plate of rib. The stress state of the overlay is influenced evidently by the modulus of rigidity transform overlay. And the stress state of the overlay can be optimized and lowered by increasing the modulus and thickness of rigidity transform overlay, The fatigue test has been done to evaluate the fatigue performance and modulus of different deck pavement materials such as epoxy asphalt, SBS modified asphalt, rosphalt asphalt which can provide reference for deck pavement structure design.

Fatigue Analysis and Life Prediction of Dumpers with Cumulative Fatigue Damage Approach

A fatigue damage model is developed for evaluating accumulative fatigue damage of dumpers. The loading spectrums acted on dumpers are created according to measured strain data in field. The finite element analysis is carried out for assessing stress distribution and strength characteristics of dumpers. Fatigue damage indexes and service life are calculated by a modified Palmgren-Miner rule. The investigation shows that fatigue notch factor has a significant influence on the calculation of fatigue damage of dumpers.

Analysis of Temperature Rise Characteristics and Fatigue Damage Degree of ACSR Broken Strand

In this paper,the research on ACSR temperature of broken strand and fatigue damage after broken strand is carried out.Conduct modeling and Analysis on the conductor through AnsoftMaxwell software.The distribution of magnetic force lines in the cross section of the conductor after strand breaking and the temperature change law of the conductor with the number of broken strands are analyzed.A model based on electromagnetic theory is established to analyze the distribution of magnetic lines of force in the cross section of the conductor after strand breaking and the temperature variation law of the conductor with the number of broken strands.The finite element analysis results show that with the increase in the number of broken strands,the cross-sectional area of the conductor decreases,the magnetic line of force of the inner conductor at the broken strand becomes denser and denser,and the electromagnetic loss of the conductor becomes larger and larger.Therefore,the temperature of the conductor at the broken strand becomes higher and higher.Then,the current carrying experiment of conductor is carried out for LGJ-240/30 conductor.It is found that the temperature rise at the junction of inner and outer layers at the broken strand is particularly obvious,and the temperature of inner aluminumconductor at the broken strand also increases with the increase of broken strand.According to the analysis of experimental data,with the increase of broken strands,the antivibration ability and service life of the conductor decrease.At the same time,under certain conditions of broken strand,the fatigue life of conductor increases with the increase of temperature.

Prediction of edge cracks and plastic-damage analysis of Mg alloy sheet in rolling

A thermal-mechanical-damage coupled finite elements model was established to investigate temperature changes, edge cracks and rolling force during roiling of magnesium alloy sheet. A cuneal sheet was also adopted to study the influence of reduction on temperature, damage and rolling force. The results show that with increasing the reduction, the rolling force increases, and the temperature of the Mg sheet decreases. Edge cracks occur when the reduction is above 51.6%, with the damage value of above 0.49. The plastic-damage in Mg sheet rolling is a result of hole development, shearing deformation and accumulative plastic strain.

Numerical study of fatigue damage of asphalt concrete using cohesive zone model

In order to investigate the fatigue behavior of asphalt concrete, a new numerical approach based on a bi-linear cohesive zone model （CZM） is developed. Integrated with the CZM, a fatigue damage evolution model is established to indicate the gradual degradation of cohesive properties of asphalt concrete under cyclic loading. Then the model is implemented in the finite element software ABAQUS through a user-defined subroutine. Based on the proposed model, an indirect tensile fatigue test is finally simulated. The fatigue lives obtained through numerical analysis show good agreement with laboratory results. Fatigue damage accumulates in a nonlinear manner during the cyclic loading process and damage initiation phase is the major part of fatigue failure. As the stress ratio increases, the time of the steady damage growth stage decreases significantly. It is found that the proposed fatigue damage evolution model can serve as an accurate and efficient tool for the prediction of fatigue damage of asphalt concrete.

Revised damage evolution equation for high cycle fatigue life prediction of aluminum alloy LC4 under uniaxial loading

The fatigue life prediction for components is a difficult task since many factors can affect the final fatigue life. Based on the damage evolution equation of Lemaitre and Desmorat, a revised two-scale damage evolution equation for high cycle fatigue is presented according to the experimental data, in which factors such as the stress amplitude and mean stress are taken into account. Then, a method is proposed to obtain the material parameters of the revised equation from the present fatigue experimental data. Finally, with the utilization of the ANSYS parametric design language （APDL） on the ANSYS platform, the coupling effect between the fatigue damage of materials and the stress distribution in structures is taken into account, and the fatigue life of specimens is predicted. The outcome shows that the numerical prediction is in accord with the experimental results, indicating that the revised two-scale damage evolution model can be well applied for the high cycle fatigue life prediction under uniaxial loading.

Multi-Scale Analysis of Fretting Fatigue in Heterogeneous Materials Using Computational Homogenization

This paper deals with modeling of the phenomenon of fretting fatigue in heterogeneous materials using the multi-scale computational homogenization technique and finite element analysis(FEA).The heterogeneous material for the specimens consists of a single hole model(25% void/cell,16% void/cell and 10% void/cell)and a four-hole model(25%void/cell).Using a representative volume element(RVE),we try to produce the equivalent homogenized properties and work on a homogeneous specimen for the study of fretting fatigue.Next,the fretting fatigue contact problem is performed for 3 new cases of models that consist of a homogeneous and a heterogeneous part(single hole cell)in the contact area.The aim is to analyze the normal and shear stresses of these models and compare them with the results of the corresponding heterogeneous models based on the Direct Numerical Simulation(DNS)method.Finally,by comparing the computational time and%deviations,we draw conclusions about the reliability and effectiveness of the proposed method.

Fatigue Analysis of Steel Catenary Risers Based on a Plasticity Model

The most critical issue in the steel catenary riser design is to evaluate the fatigue damage in the touchdown zone accurately. Appropriate modeling of the riser-soil resistance in the touchdown zone can lead to significant cost reduction by optimizing design. This paper presents a plasticity model that can be applied to numerically simulate riser-soil interaction and evaluate dynamic responses and the fatigue damage of a steel catenary riser in the touchdown zone. Utilizing the model, numerous riser-soil elements are attached to the steel catenary riser finite elements, in which each simulates local foundation restraint along the riser touchdown zone. The riser-soil interaction plasticity model accounts for the behavior within an allowable combined loading surface. The model will be represented in this paper, allowing simple numerical implementation. More importantly, it can be incorporated within the structural analysis of a steel catenary riser with the finite element method. The applicability of the model is interpreted theoretically and the results are shown through application to an offshore 8.625 steel catenary riser example. The fatigue analysis results of the liner elastic riser-soil model are also shown. According to the comparison results of the two models, the fatigue life analysis results of the plasticity framework are reasonable and the horizontal effects of the riser-soil interaction can be included.

A Multiscale Method for Damage Analysis of Quasi-Brittle Heterogeneous Materials

A novel multiscale algorithm based on the higher-order continuum at both micro-and macrostructural level is proposed for the consideration of the quasi-brittle damage response of heterogeneous materials.Herein,the microlevel damage is modelled by the degradation of the homogenized stress and tangent stiffness tensors,which are then upscaled to govern the localization at the macrolevel.The C^1 continuity finite element employing a modified case of Mindlin’s form II strain energy density is derived for the softening analysis.To the authors’knowledge,the finite element discretization based on the strain gradient theory is applied for the modeling of damage evolution at the microstructural level for heterogeneous materials for the first time.The advantage of the novel C1 finite element formulation in comparison with the standard finite element discretization in terms of the regularization efficiency as well as the objectivity has been shown.An isotropic damage law is used for the reduction of the constitutive and nonlocal material behaviour,which is necessary for the physically correct description of the localization formation in quasi-brittle materials.The capabilities of the derived finite element to capture the fully developed localization zones are tested on a random representative volume element(RVE)for several different loading cases.By employing the conventional second-order computational homogenization,the microstructural material constitutive response is averaged over the whole RVE area.In order to model the loss of structural integrity when sharp localization is formed across RVE,the specific conditions which detect a completely formed localization zone are developed.A new failure criterion at the microstructural level has been proposed.The derived finite element formulation,as well as the multiscale damage algorithm,are implemented into the finite element program ABAQUS.The capabilities of the presented multiscale scheme to capture the effects of the deformation localization are demonstrated by few benchmark numerical examples.

The Performance of Small Diameter Aluminum Light Support Structures Containing Handholes under Cyclic Fatigue

Aluminum light poles play a pivotal role in modern infrastructure, ensuring proper illumination along highways and in populated areas during nighttime. These poles typically feature handholes near their bases, providing access to electrical wiring for installation and maintenance. While essential for functionality, these handholes introduce a vulnerability to the overall structure, making them a potential failure point. Although prior research and analyses on aluminum light poles have been conducted, the behavior of smaller diameter poles containing handholes remains unexplored. Recognizing this need, a research team at the University of Akron undertook a comprehensive experimental program involving aluminum light poles with handholes containing welded inserts in order to gain a better understanding of their fatigue life, mechanical behavior, and failure mechanisms. The research involved testing seven large-scale aluminum light poles each 8-inch diameter, with two separate handholes. These handholes included a reinforcement that was welded to the poles. Finite Element Analysis (FEA), statistical analysis, and comparison analysis with their large counterparts (10-inch diameter) were used to augment the experimental results. The results revealed two distinct failure modes: progressive crack propagation leading to ultimate failure, and rupture of the pole near the weld initiation/termination site around the handhole. The comparison analysis indicated that the 8-inch diameter specimens exhibited an average fatigue life exceeding that of their 10-inch counterparts by an average of 30.7%. The experimental results were plotted alongside the fatigue detail classifications outlined in the Aluminum Design Manual (ADM), enhancing understanding of the fatigue detail category of the respective poles/handholes.

FATIGUE DAMAGE AND LIFETIME PREDICTION OF AERONAUTIC WELDED STRUCTURES UNDER HIGH TEMPERATURE

The fatigue damage evolution equations and the relation of fatigue damage parameter with maximum cyclic stress of superalloy GH150 and its welded structures are established. The fatigue damage evolution equations in a multiaxial stress state are also given. By use of cyclic thermal elastoplastic damage constitutive relations, the fatigue damage and lifetime predictions are carried out for the welded combustion chamber of aeroengine.

Fatigue Strength and Modal Analysis of Bogie Frame for DMUs Exported to Tunisia

The equivalent stress at key positions of Bogie Frame for DMUs Exported to Tunisia is obtained by using simulation analysis. The evaluation of static strength and fatigue strength is checked referring to UIC specification and Goodman sketch for welding materials. In addition, the modal analysis of the frame is made, and the vibrational modal of frame in given frequency domain is predetermined to evaluate the dynamical behavior of the frame in order to meet the dynamical design requirements. The results show that the key points of the calculated frame of the equivalent stress are less than allowable stress, and thus it could provide a theoretical foundation for the optimized design of frame structure and safety of industrial production.

Finite Element Model of a Filament-Wound Composite Tube Subjected to Uniaxial Tension

The aim of this paper is to demonstrate the mechanical behaviour of a filament-wound composite tube subjected to uniaxial tension by finite element analysis. Uniaxial tensile test experiments have been carried out on standard specimen and hose piece in order to verify finite element models and material properties and also to assess failure mode of composite plies. Composite reinforcement plies are modeled as linear orthotropic, while elastomer liners are described by hyperelastic material model. Results of finite element models and experiments show good agreement in the initial phase of uniaxial tension, which justifies utilized material models in the operating range. Results of finite element models show that transverse tension and shear load are dominant under tension. It is determined that principal failure mode of reinforcement plies is intra-ply yarn-matrix debonding caused by intensive shear of rubber matrix.

Computation of the Fatigue Life of Road Wheel with Double-Layer Rubber Flange

In order to increase the fatigue life (FL) of road wheels (RW), a kind of double layer rubber flange (DLRF) is put forward. It consists of two layers of rubber, where metal wires are laid in the inner layer and the outer layer has no inlaid metal wires. Stress, strain and temperature field of DLRF were calculated with ANSYS finite element analysis (FEA) software, FL of DLRF RW was also computed with fracture mechanics fatigue theory. The results of computation indicate that the heat generated in RW's rubber flange (RF) can be reduced by the use of DLRF, and the FL of RW can be increased without affecting the mechanical intensity of RW.

FATIGUE LIFE PREDICTION OF CRANKSHAFT MADE OF MATERIAL 48MnV BASED ON FATIGUE TESTS,DYNAMIC SIMULATION AND FEA

S-N curve and fatigue parameters of 48MnV are obtained using small sample tests and staircase or up and down method, which paves the way for predicting fatigue life of crankshaft made of 48MnV. The fatigue life of the crankshaft of a six-cylinder engine is calculated using different damage models such as S-N method, normal strain approach, Smoth-Watson-Topper （SWT）Bannantine approach, shear strain approach, and Fatemi-Socie method based on dynamic simulation and finite element analysis （FEA） of crankshaft. The results indicate that the traditional calculation is conservative and the residual fatigue life of crankshaft is sufficient to maintain next life cycle if the crankshaft is remanufactured after its end of life.

Enhanced Multi-Layer Fatigue-Analysis Approach for Unbonded Flexible Risers

This paper proposes an enhanced approach for evaluating the fatigue life of each metallic layer of unbonded flexible risers. Owing to the complex structure of unbonded flexible risers and the nonlinearity of the system, particularly in the critical touchdown zone, the traditional method is insufficient for accurately evaluating the fatigue life of these risers. The main challenge lies in the transposition from global to local analyses, which is a key stage for the fatigue analysis of flexible pipes owing to their complex structure. The new enhanced approach derives a multi-layer stress-decomposition method to meet this challenge. In this study, a numerical model validated experimentally is used to demonstrate the accuracy of the stress-decomposition method. And a numerical case is studied to validate the proposed approach. The results demonstrate that the multi-layer stress-decomposition method is accurate, and the fatigue lives of the metallic layers predicted by the enhanced multi-layer analysis approach are rational. The proposed fatigue-analysis approach provides a practical and reasonable method for predicting fatigue life in the design of unbonded flexible risers.