Finite Element Fatigue Research Articles

Fatigue life prediction of rubber suspension bushings based on virtual road load spectrum pulses

Rubber suspension bushings have mainly been studied under single- or multi-axis load cycling, while research on rubber suspension bushings under random load cycling is not deep enough. This study conducted uniaxial tensile and fatigue tests on N60 rubber dumbbell-shaped plate samples to obtain stress–strain curves and S–N curves. Using the uniaxial tensile test data, a Mooney–Rivlin hyperelastic constitutive model was fitted using Abaqus software, and a finite element model of the rubber suspension bushing was established. A 3D virtual road surface was constructed using Adams software, and characteristic features of typical road surfaces were extracted for statistical analysis, resulting in the generation of a load spectrum showing variations in force over time. Based on the Miner linear damage accumulation theory, finite element fatigue life prediction of the rubber suspension bushing was conducted using pulses from the 232 s region of the load spectrum. The predicted fatigue life was compared to the results from benchtop fatigue testing, resulting in a relative error of less than 6.443 %. The findings suggest that the method is effective in predicting the fatigue life of rubber suspension bushings under random loads.

Experimentally calibrated finite element fatigue reliability assessment of an offshore platform in the Persian Gulf

Experimentally calibrated finite element fatigue reliability assessment of an offshore platform in the Persian Gulf

Technology Focus: Bits and Bottomhole Assemblies (December 2023)

As bottomhole-assembly and drill-bit design and operation have embraced new technologies such as artificial intelligence, new materials and manufacturing techniques, and improved design software, the industry continues to research methods of optimizing delivery and understanding of already globally used technologies. It is this approach that has long allowed service companies, operators, and drilling contractors alike to improve drilling performance, as highlighted in the papers summarized here. In the first of these papers, paper SPE 210723, finite element fatigue simulation has been used to minimize the risk of twistoffs in jars, something that many of us in the drilling community have experienced. This paper can help us reduce those unplanned events and lost time. Many rigs worldwide have moved to using autodriller-type control systems, and, in many cases, these systems have shown improved performance. In the second paper, paper SPE 214997, the optimization of these systems is discussed in the review and modification of driller procedures to minimize damage to bottomhole assemblies and the drill bit during drilling. Finally, while many papers have discussed high-frequency torsional oscillations and their effect on the bottomhole assembly and drill bit from an operational or a theoretical view point, the final paper, paper SPE 212566, discusses full-scale laboratory experiments to qualify the drill bit’s influence on this effect. All three of these papers highlight increased understanding in the operation and evolution of existing technologies to improve drilling delivery. In the evolving world of drilling where the final objectives and uses of wells are changing—whether for repurposing; carbon capture, use, and storage; or geothermal uses—these approaches to optimizing existing technologies in conjunction with the introduction of new technologies can help oilfield drilling teams pivot into this adjacent energy environment to deliver successful wells. Recommended additional reading at OnePetro: www.onepetro.org. SPE 212438 Building a System To Solve the Challenges of Drilling Hot Hard Rock for Geothermal and Oil and Gas by Anthony Pink, NOV, et al. SPE 212559 Machine Learning-Based Drilling System Recommender: Toward Optimal BHA and Fluid-Technology Selection by Gregory Skoff, SLB, et al. SPE 212109 World’s First Application of Steel Body Bit in High-Chloride Formation With Water-Based Mud by Bekbolat Uandykov, Zhigermunaiservice, et al.

Fracture Toughness and Fatigue Crack Growth Analyses on a Biomedical Ti-27Nb Alloy under Constant Amplitude Loading Using Extended Finite Element Modelling.

The human body normally uses alternative materials such as implants to replace injured or damaged bone. Fatigue fracture is a common and serious type of damage in implant materials. Therefore, a deep understanding and estimation or prediction of such loading modes, which are influenced by many factors, is of great importance and attractiveness. In this study, the fracture toughness of Ti-27Nb, a well-known implant titanium alloy biomaterial, was simulated using an advanced finite element subroutine. Furthermore, a robust direct cyclic finite element fatigue model based on a fatigue failure criterion derived from Paris' law is used in conjunction with an advanced finite element model to estimate the initiation of fatigue crack growth in such materials under ambient conditions. The R-curve was fully predicted, yielding a minimum percent error of less than 2% for fracture toughness and less than 5% for fracture separation energy. This provides a valuable technique and data for fracture and fatigue performance of such bio-implant materials. Fatigue crack growth was predicted with a minimum percent difference of less than nine for compact tensile test standard specimens. The shape and mode of material behaviour have a significant effect on the Paris law constant. The fracture modes showed that the crack path is in two directions. The finite element direct cycle fatigue method was recommended to determine the fatigue crack growth of biomaterials.

Investigation of CFRP-Countersunk Bolted Assembly Fatigue Damage under Three-Point Bending via Experimental and Numerical Analysis

In this research, the fatigue damage behavior under three-point bending of a composite joint incorporating a single countersunk fastener is investigated. Firstly, a self-developed fatigue test system was set up to test the fatigue characteristics of CFRP-countersunk bolted assembly under the displacement amplitude cycles of 103 to 106 to study the formation and expansion rule of damage and cracks. It found two typical damage processes, both of which involve some formal interface damage between fiber and matrix. Based on the experiment, a finite element fatigue damage analysis on this assembly was carried out according to the Hashin failure criterion. The simulation result shows an identical fatigue damage location and fatigue life with the experimental phenomenon. Moreover, it predicted the final fatigue life of the specimen under 10 hz cyclic loading with 1 mm displacement and 10 Nm bolt preloading. This research provides guidance for the engineering fatigue issues of single-bolted joint composite connection structures and provides a reference for the corresponding technical specifications formulation.

A fatigue reliability assessment approach for wind turbine blades based on continuous time Bayesian network and FEA

AbstractWind turbine blades made by composite materials (CWTBs), encounter fatigue failures, such as cracks, fractures, delamination, etc. Finite Element Analysis (FEA) is applied for fatigue performance simulations of CWTBs as the full‐scale testing is costly. To consider correlated failures and uncertainties in load and material parameters, this paper proposes a fatigue reliability assessment method based on continuous time Bayesian network and FEA. Specifically, the dangerous regions of each component of CWTBs are determined by finite element fatigue simulation. The failure probability distributions of components are then computed by quantifying the uncertainties of several factors including the load and material parameters. A continuous time Bayesian network model is constructed for the fatigue reliability of CWTBs. The performance of the proposed method is verified by a comprehensive analysis with the results of discrete time Bayesian networks.

Fatigue performances of helicopter gears

Abstract Gears are widely used machine elements to transmit power and motion in the industry. During the power transmission, the gears are subjected to cyclic loads. Thus the fatigue resistance of the gears should be deeply investigated. In particular, this issue is gaining much more importance in the space and aviation fields. In this study, the fatigue life of gears made of 9310-VIM-VAR steel used in the aviation field was determined experimentally, and the crack propagation paths obtained were numerically verified. To this end, the SAE J1619 standard single-tooth bending fatigue test apparatus was redesigned and manufactured in order to adapt it to the helicopter gears. Totally 28 single-tooth bending fatigue tests were carried out for various loading conditions. Accordingly, the S–N curves for the helicopter gears were created. The experimental results were verified by the finite element fatigue crack propagation analysis in terms of the initial crack location, crack initialization angle, and crack propagation paths. Conducted experiments and numerical studies are found as compatible with each other.

Clamping Fatigue Properties of Shrink-Fit Holder.

In order to explore the clamping fatigue properties of shrink-fit holders, ANSYS software was used in this study to analyze the thermal and contact stresses during the clamping process of the shrink-fit holder, and the fatigue analysis was performed by selecting the dangerous areas based on the two stresses. A numerical control shrink-fit holder clamping fatigue test device was manufactured, and the automatic clamping of the shrink-fit holder was executed in this study. After 500 clamping repetitions, a milling test was carried out on the shrink-fit bracket. By collecting the vibration signal of the workpiece during processing and measuring the change in the surface roughness of the workpiece, and then analyzing the change in the machining performance of the shrink-fit holder under different clamping times, we were able to compare and verify the accuracy of the finite element fatigue analysis.

Finite Element Simulation and Fatigue Damage Analysis of High-Speed Train Gearbox Shell Based on Structure and Material Cross-Scale Correlation

Finite Element Simulation and Fatigue Damage Analysis of High-Speed Train Gearbox Shell Based on Structure and Material Cross-Scale Correlation

Multiple Reflective Cracks in Semirigid Base Asphalt Pavement under Traffic Load Using XFEM

This paper built a three‐dimensional layered structure model of semirigid base asphalt pavement with single and double transverse reflective cracks based on the Extended Finite Element Method and fatigue fracture theory. The effects of the number of cracks, crack spacing, and crack length on the stress intensity factors (KI, KII, and Keff) under moving vehicle loads were studied. The fracture life of the asphalt pavement structure was calculated based on the Pairs formula. The results demonstrate that reflective cracks in semirigid asphalt pavement are composite cracks of type I and type II under moving vehicle loads, and shear fracture is the main reason for the failure of the base. The damage to the pavement base will be accelerated with the increase in the number of cracks and the length of the cracks. As the distance between the two reflection fractures is closer, the interaction between the cracks has a superimposed enhancement effect on the crack propagation. Compared with the single nonpenetrating crack model, the fatigue life of the nonpenetrating reflective crack in the double crack pavement structure with a crack spacing of 30 cm is reduced by 46.87%. The research on the propagation mechanism of reflective cracks in this paper provides the essential theoretical and numerical basis for the design, construction, working condition evaluation, and maintenance of pavement structures.

Contact fatigue life prediction of rolling bearing considering machined surface integrity

PurposeRolling bearings often cause engineering accidents due to early fatigue failure. The study of early fatigue failure mechanism and fatigue life prediction does not consider the integrity of the bearing surface. The purpose of this paper is to find new rolling contact fatigue (RCF) life model of rolling bearing.Design/methodology/approachAn elastic-plastic finite element (FE) fatigue damage accumulation model based on continuous damage mechanics is established. Surface roughness, surface residual stress and surface hardness of bearing rollers are considered. The fatigue damage and cumulative plastic strain during RCF process are obtained. Mechanism of early fatigue failure of the bearing is studied. RCF life of the bearing under different surface roughness, hardness and residual stress is predicted.FindingsTo obtain a more accurate calculation result of bearing fatigue life, the bearing surface integrity parameters should be considered and the elastic-plastic FE fatigue damage accumulation model should be used. There exist the optimal surface parameters corresponding to the maximum RCF life.Originality/valueThe elastic-plastic FE fatigue damage accumulation model can be used to obtain the optimized surface integrity parameters in the design stage of bearing and is helpful for promote the development of RCF theory of rolling bearing.

Ductile iron optimization approach for mechanically and thermally loaded components

The mechanical and thermal properties of ferritic–pearlitic ductile irons vary widely according to their silicon and pearlite contents. Thus, different combinations of silicon and pearlite affect components’ lifetime under mechanical and thermal stress. An excellent example of the usage of such irons is combustion engine cylinder heads. They experience transient thermal loading (heating and cooling) during starting and stopping in addition to mechanical loading (combustion) during engine operation. An optimization approach and calculation models for the estimation of the optimal ductile iron composition are presented in this study. The approach allows selection of the most suitable base composition for subsequent analyses, such as casting simulation and final accurate finite element modelling and fatigue calculations.

Finite Element Fatigue Analysis of Mouldboard Plough Cross Bar Based on the Draft Force of MF 399 Tractor

Cross bar of mouldboard plough of Massey Ferguson 399 Tractor was investigated by finite element method in point of failure analysis. A 3-d model of the cross bar was provided in ANSYS Software, and the constraints, boundary conditions, and loads were applied on the model. The fatigue analysis was done on the model after static analysis. The exerted loads were calculated based on the maximum draft force of the tractor. Based on Soderberg criteria, the safety factor in fatigue analysis was calculated and that of the left hole of the cross bar was minimum as 1.82 that shows higher failure probability of that. The result of fatigue analysis in the present research is in agreement with that practically is happened for mouldboard plough cross bar.

Investigation of Shock Signals from SAE J577 Mechanical Shock Machine

In this study, acceleration signals measured from the SAE J577 mechanical shock machine are investigated in detail. The aim of this investigation is to derive representative standard acceleration signals to be used as acceleration loads for finite element fatigue analysis of Automotive Lighting parts. These signals can also be used as load inputs for vibration shakers which have the capability of driving time domain signals. First of all, acceleration signals have been measured from the free machine table and by the help of the signal analysis software, automatic averaging operation has been performed from the long train of shock signals to have a single average acceleration shock signal. Furthermore; because the machine is force controlled, it is understood that the total weight and the overall dimensions of the device under test (DUT) and the fixture have significant effect on the severity of the test. Thus, measurements are repeated from the different sized fixtures and the results are compared in order to understand the effects of the fixture size and the weight on test severity.

Mixed mode fatigue crack growth studies in AISI 316 stainless steel

Damage tolerance assessment requires the accurate prediction of fatigue crack growth lives. Numerical simulation techniques using mixed mode Paris' law and various equivalent stress intensity factor models (ΔKeq) are widely employed for fatigue life prediction. In the present work, mixed mode (I/II) fatigue crack growth experiments are performed using the compact tension shear specimens made of AISI 316 austenitic stainless steel for various loading angles. Finite element fatigue crack growth simulations are carried out, and the effect of ΔKeq model in fatigue life prediction is studied. To achieve this, a three parameter double exponential type best fit is proposed for fitting the experimental mixed mode crack length vs fatigue life. The performance and capability of various selected models are assessed by comparing the predicted life with the experimental results. Fractographic studies at different stages of crack propagation for different loading angles are also presented to aid the above assessments. Based on the overall consistent performance, Irwin's and Tanaka models are predicting life close to the experimental data and Richard's and Yan's models provide conservative solutions.

A microstructure based approach to model effects of surface roughness on tensile fatigue

This paper presents a novel approach to model the effects of surface roughness on fatigue of tensile specimens. Voronoi tessellation was employed to simulate material microstructure and generate rough surfaces. Continuum damage mechanics was utilized to model progressive material degradation due to fatigue loading. In order to evaluate and corroborate the results from the finite element fatigue damage model, an experimental investigation was conducted on 4130 steel specimens under fully reversed loading. SEM Imaging was performed to obtain grain morphology parameters to model microstructure accurately using Voronoi grains. Ra measured from optical surface profilometry was utilized to model roughness. Three levels of roughness were chosen for this study. Damage parameters for fatigue modeling were obtained from the experimental SN results of the smooth specimens having Ra = 0.1 μm. The same parameters were used to model fatigue of numerically generated rough domains and predict a reduction in fatigue lives with increase in Ra. The randomness originating from microstructure and surface profile predicts a scatter in fatigue lives. The fatigue failure mechanism predicted by the model is in close agreement with experimental observations. The reduction in endurance limit with increasing roughness level as predicted by the model provides better accuracy than the widely used empirical relationship for surface finish factor ka.

Reinforcement Analysis of Rigid Hangers for Existing Old Arch Bridges: A Case Study of Ling Bridge

Ling Bridge, built in 1936, is an old half-through riveted steel arch bridge with rigid hangers and a floating deck system. The effects of various factors, such as temperature, vehicle load, and crowd load, have caused large additional stresses on the rigid hangers. According to the inspection in 2011, the bridge was in a dangerous state. Therefore, improving the structural strength of the bridge and prolonging the service life for another 40 years while protecting the cultural relic were major problems. This study analyzes rigid hangers on the premise that the reinforcement schemes of other bridge components have been determined. First, the damage situation, material properties and mechanical behaviors of old hangers are evaluated. Second, an appropriate reinforcement method is proposed. Third, mechanical and fatigue analyses are conducted on the new structures to prove the rationality of the reinforcement method. For the undemolished old structures, a fracture assessment of existing damage is performed to obtain the evolution laws and ensure safety. Finite element calculations and fatigue fracture analyses show that the proposed reinforcement method for the hanger system can reduce all hangers’ stresses effectively to prolong service life and protect the cultural relic.

Experimental and finite element fatigue assessment of the spring clip of the SKL-1 railway fastening system

The fastening system that links the rail and the sleeper in railway lines is an element of high responsibility, since its failure may lead to the derailment of the train. This paper combines an experimental approach and a Finite Element model to assess the structural integrity of the spring clip of the SKL-1 fastening system, used assiduously in high-speed lines. Our results prove that fatigue is not the failure mechanism that explains the fractures of clips as pointed out by other authors, provided the following requirements: the material has received the appropriate thermomechanical treatments; the assembly of the clip has been carried out with precision; and the system has not suffered anomalous in-service overloads.

Shell Analysis and Optimisation of a Pure Electric Vehicle Power Train Based on Multiple Software

Motor end cover mounting fracture is a problem recently encountered by novel pure electric vehicles. Regarding the study of the traditional vehicle engine mount bracket and on the basis of the methods of design and optimisation available, we have analysed and optimised the pure electric vehicle end cover mount system. Multi-body dynamic software and finite element software have been combined. First, we highlight the motor end cover mount bracket fracture engineering problems, analyse the factors that may produce fracture, and propose solutions. By using CATIA software to establish a 3D model of the power train mount system, we imported it into ADAMS multi-body dynamic software, conducted 26 condition analysis, obtained five ultimate load conditions, and laid the foundations for subsequent analysis. Next, a mount and shell system was established by the ANSYS finite element method, and modal, strength, and fatigue analyses were performed on the end cover mount. We found that the reason for fracture lies in the intensity of the end cover mount joint, which leads to the safety factor too small and the fatigue life not being up to standard. The main goal was to increase the strength of the cover mount junction, stiffness, safety coefficient, and fatigue life. With this aim, a topology optimisation was conducted to improve the motor end cover. A 3D prototype was designed accordingly. Finally, stiffness, strength, modal, and fatigue were simulated. Our simulation results were as follows. The motor end cover suspension stiffness increases by 20%, the modal frequency increases by 2.3%, the quality increases by 3%, the biggest deformation decreases by 52%, the maximum stress decreases by 28%, the minimum safety factor increases by 40%, and life expectancy increases 50-fold. The results from sample and vehicle tests highlight that the component fracture problem has been successfully solved and the fatigue life dramatically improved.

Study on SN-based and FCP-based Fatigue Assessment Techniques for T-Shaped Tubular Welded Joint

Full-scale fatigue tests of the land structure's T-shaped tubular welded joints are conducted. Three-dimensional finite element (FE) fatigue crack propagation (FCP) analyses based on VCCM with tetrahedral elements are performed in order to obtain the reference SIF solutions. The preciseness of the FE FCP analyses is demonstrated by comparing calculated and measured crack propagation behaviors. Hot spot stress (HSS)-based fatigue assessments are carried out by using various fatigue design codes for tubular joints, and the safety margin of each HSS determination techniques are compared. The crack propagation lives are also predicted by carrying out FCP analyses based on Mk factor method. HSS determination techniques examined in the fatigue assessment are adopted to determine the stress concentration factor (SCF) and the degree of bending (DOB) in Mk factor calculations. It is found that the Mk factor-based FCP results show good agreement with the FE FCP results and the measurements when the HSS determination technique with the smallest safety margin is chosen. Based on these results, the method for selecting SCF and DOB calculation procedure for Mk factor-based FCP analysis is proposed. It is also shown that the difference between the fatigue test results and the HSS SN-based fatigue assessment results becomes smaller when the SIF estimated by Mk factor method agrees with the SIF calculated by the FE fracture analysis.