Load Fatigue Life Research Articles

Study on fatigue performance and topology optimization of cast steel bifurcation joint under alternating load

Abstract The numerical simulation analysis of a typical cast steel bifurcation joint under the alternating load was performed to comprehend its mechanical properties. The MSC Fatigue is used to explore and analyze the fatigue behavior of joints, and the control variable approach is used to examine the impact of various geometric parameters on fatigue life. Then, the load spectrum and fatigue life were invertedly calculated and transformed into maximum stress constraints by converting fatigue limitations into stress constraints. Finally, the optimal shape of cast steel bifurcation joint under fatigue limitations was studied using topology optimization methods, intending to solve the lightweight problem while still fulfilling fatigue design requirements. The research results show that the intersection of the main and branch pipes is the fatigue weakest part of the whole joint, and the geometric parameters significantly affect the joint's fatigue performance. The topology optimization shapes of cast steel bifurcated joints are different under vertical and horizontal loads, indicating that different load conditions significantly impact topology optimization shapes. The topology optimization method can reduce the self-weight while maintaining fatigue performance.

A generative adversarial network for enhancing over-expansion flow field perception of nozzles with large expansion ratio

Over-expansion flow and separation phenomena exist inside the nozzle during the startup and shutdown of the rocket engine, and the transition between the separation modes is prone to cause significant side loads and jeopardize the safety of the engine. Accurate, comprehensive and prompt nozzle flow field state perception is of great significance to the stable operation of the engine. Here, a generative adversarial network is proposed to reconstruct the internal Mach number and temperature fields for different nozzle pressure ratios and flow separation modes based on the discrete pressure at the nozzle wall. The proposed generative adversarial network employs Wasserstein distance and gradient penalty to improve the problems of gradient vanishing and pattern collapse during discriminator network training. The large expansion ratio nozzle selected was the VOLVO S1 nozzle and numerical simulations were carried out under different nozzle pressure ratio conditions to obtain data for the training of data-driven model. The results indicate that generative adversarial networks can accurately reconstruct restricted shock separation and free shock separation modes under different nozzle pressure ratios based on discrete pressure and temperature measurement points on the nozzle wall, with a relative error of less than 1.2%, and accurately identify important flow field characteristics such as Mach disk, supersonic jet flow, and multiple recirculation regions. The advantages of the generative model in recognizing the strong normal shock Mach disk are compared with those of the supervised learning model. This study lays the foundation for the subsequent study of nozzle side load and structural fatigue life based on three-dimensional flow field.

A modified Manson-Halford model based on improved WOA for fatigue life prediction under multi-level loading

The Manson-Halford (M-H) nonlinear cumulative damage model is widely applied for fatigue life analysis problems under multi-level loading. In this model, the influence of loading sequence on the fatigue life can be better considerer, but the loading interaction effect is ignored. An improved whale optimization algorithm (IWOA) by integrating multiple strategies is proposed. The ability of global search and local exploitation is balanced and improved through nonlinear convergence factor, adaptive weighting factors and the Cauchy reverse learning strategies. In order to fully account for loading interaction effect, loading weighting factors are introduced to modify the M-H model, and the parameters are optimized through the global search properties of IWOA. The model is evaluated on multi-level loading fatigue experimental data from five metal materials and two aluminum alloy welded joints. The results suggest that the proposed IWOA has better optimization accuracy compared to the standard whale optimization algorithm (WOA). The proposed modified M-H model has better prediction performance compared to the four traditional cumulative damage models, which can be effectively applied to multi-level loading fatigue life analysis problems under actual working conditions. The proposed model is useful for the study of fatigue life evaluation methods.

Fatigue characteristics of deep excavation-disturbed Jinping marble

Deep rocks encountered in underground engineering are frequently in complex in situ environments and experience both excavation disturbance during construction and cyclic loading throughout the long-term operation. Understanding the fatigue behavior of excavation-disturbed rocks in complex stress environments is critical for assessing the long-term stability of deep rock structures. Hence, an experimental method has been developed to capture the fatigue damage process of rocks while considering the in situ environment and excavation disturbance. Using this method, a series of triaxial fatigue damage experiments were conducted on Jinping deep marble samples from various in situ environments of 100 m, 1000 m, 1800 m, and 2400 m to better understand the variation in fatigue characteristics at different depths. With increasing depth, the samples experienced more cycles and greater fatigue deformation before failure. Further insights were gained into the fatigue damage behavior in terms of stiffness degradation, energy dissipation and irreversible strain accumulation. A decrease in the elastic modulus and an increase in the dissipated energy and irreversible strain exhibit an evolution pattern of initial→stabilization→acceleration, reflecting the nonlinear fatigue process that occurs inside marble. With increasing depth, marble samples have longer fatigue lives but exhibit more significant stiffness loss, energy dissipation and irrecoverable deformation accumulation; thus, evaluating the instability of deep rock structures solely using fatigue life alone is inadequate. Moreover, the previously reported inverted S-shaped evolution of fatigue damage was observed, and it was found that an increase in depth leads to an earlier onset of the accelerated fatigue damage stage with greater dominance of fatigue failure. Based on the nonlinear strain, loading cycle variable and fatigue life, a highly accurate nonlinear fatigue model was developed to describe the complete inverted S-shaped evolution pattern of fatigue damage, which demonstrated excellent practical implications for the theoretical characterization of anisotropic fatigue damage in disturbed Jinping marble.

The influence of different load distribution considering geometric error on the fatigue life of ball screw

The ball screw pair is a precision drive component that converts rotary motion into linear motion. In practical applications, because the feed system usually has rotational torque and geometric errors, it may increase the contact load of the ball screw pair and reduce the fatigue life. In order to study the influence of different loads and geometric errors on the maximum contact load and fatigue life of ball screw pairs, the following research work was carried out. Firstly, based on the composite load and rotational torque, the ball load distribution model is established, and the accuracy of the model is verified by finite element modeling analysis. Then, the influence of different composite loads, rotation times and geometric errors (including ball size error, lead error and raceway tooth profile error) on the ball load distribution is analyzed. Finally, the influence of compound load, rotating torque and geometric error on the fatigue life of ball screw pairs is studied. The results show that the rotational torque and lead error have a great influence on the load distribution and fatigue life of the ball, and the influence of lead error on load distribution is greater than that of dimension error and tooth profile error. The fatigue life of the ball screw pair with non-uniform load distribution is shorter than that of the ball screw pair with uniform load distribution.

FEM and field tests to study the dynamic response of composite pavement surrounding embedded tram tracks to moving loading: implications to fatigue cracking

Under long-term tram loads, cracking occurs on the composite pavement surrounding an embedded tram track. However, in the current pavement design of the shared right-of-way section of a tram track, the trackside pavement fatigue characteristics are not considered. The investigation of the real dynamic strain response of the trackside composite pavement under tram loads is crucial for pavement system design. In this paper, a three-dimensional finite element model of tram-track- composite pavement was established. The rationality of this model was verified by a field pavement dynamic test. The influence of the track irregularity and tram speed on the dynamic characteristics of the pavement surrounding the track was explored. The trackside pavement strain distribution along the longitudinal and vertical directions of the track had been studied. The high-frequency strain components caused by the random shortwave track irregularity excitation were found in the strain frequency domain curves in different directions, and the track irregularity amplifies the influence of the tram speed on the surrounding pavement dynamic response. The loading frequency is an important input for determining the dynamic model and fatigue characteristics of asphalt materials. At the same time, the lab test loading frequency and fatigue life corresponding to the mixture were calculated by the mechanistic coupled model and empirical damage evolution equation. It provides an analytical base for the design of pavement surrounding embedded tram tracks.

A Deep Learning-Based CAE Approach for Simulating 3D Vehicle Wheels Under Real-World Conditions

The implementation of deep learning (DL) in computer-aided engineering (CAE) can significantly improve the accuracy and efficiency of simulating 3D vehicle wheels under real-world conditions. While traditional CAE methods can be time-consuming and computationally expensive, DL can reduce simulation time and development cycles across all industries. This work explores the role of DL and AI in virtual manufacturing and CAE and investigates how they can be used to improve the accuracy and efficiency of simulations for 3D vehicle wheels. Deep learning models can learn the complex relationships between different wheel design parameters, such as tire load distribution, stress distribution, and fatigue life. Once trained, these models can be embedded into CAE software, allowing for faster and more accurate simulations of wheel performance. This interdisciplinary study uses various deep learning techniques, including convolutional neural networks (CNNs), generative adversarial networks (GANs), and recurrent neural networks (RNNs), to create a more efficient and accurate relationship between CAD modeling and CAE simulation. The research aims to leverage the potential of deep learning models to automate 3D CAD design, accurately predict CAE results, and provide in-depth explanations and verifications. The benefits of this research are expected to extend to the automotive industry's pursuit of more robust and resilient wheel designs. By streamlining the product development process from conceptual design to engineering performance evaluation, this study has the potential to revolutionize the automotive industry's product development cycle.

Load response and fatigue life of cement-stabilized macadam base structure considering dynamic and static load differences and tension-compression modulus differences

The conventional semi-rigid base asphalt pavement (SRBAP) construction is designed with the classical theory of linear elastic mechanics. There is a significant discrepancy between the calculation results of the pavement structure load response and the measured results, which leads to inaccurate structural resistance and load response calculations. For this reason, this work depended on the actual structure of the SRBAP, took the linear elasticity theory as a contrast, and considered the difference between dynamic and static loads or the difference between the compressive and tensile modulus of pavement materials. Thus, the pavement structure response to load under three conditions is calculated, and five mechanical indexes are selected for comparative analysis. Furthermore, based on the calculated mechanical response, the structural fatigue life of the cement-stabilized macadam (CSMB) was then calculated, replacing the design index in the fatigue cracking model with the underside tensile stress or equivalent stress. The results demonstrated 20–30% variations between the calculated mechanical responses to dynamic and static stresses. Additionally, there is a substantial discrepancy between the strain computed using the bimodulus theory and the traditional linear elasticity theory, with a maximum divergence of 40%. In the meantime, the fatigue life of the CSMB produced using various design indices is noticeably different, and the fatigue life achieved using equivalent stress as the design index is significantly higher than that obtained using underside course tensile stress. Following is a relationship between the CSMB's fatigue life calculated by underside course tensile stress: viscoelastic theory (dynamic load) > bimodulus theory (tension–compression modulus difference) > classical linear elastic theory; The relationship of fatigue life represented by equivalent stress is as follows: viscoelastic theory > classical linear elastic theory > bimodulus theory.

A numerical study of fatigue life in high-speed angular contact ball bearings with thermal and centrifugal expansion

PurposeFix-position preloading, centrifugal force and higher temperatures cause the bearing units in angular contact ball bearings to expand, changing the contact load and affecting bearing life. This study aims to examine the effect of thermal and centrifugal expansion on the fatigue life of fix-position preloaded angular contact ball bearings in high-speed operating conditions.Design/methodology/approachThe contact loads on the inner and outer bearing rings were resolved according to the thermal and centrifugal expansion factors in the quasi-static position preloading model. The pressure and frictional stress distribution were used to calculate the subsurface stress in the contact area, while the Zaretsky model was used to determine the relative fatigue life of the inner and outer bearing rings.FindingsUnder fix-position bearing preloading, thermal and centrifugal expansion significantly affected the contact load and relative fatigue life. At the same axial preload, the inner ring contact load was higher than the outer ring contact load, with a maximum difference of 132.3%. The decrease in the inner ring relative life exceeded the outer ring contact load, with a maximum difference of 7.5%, compared to the absence of thermal and centrifugal expansion.Originality/valueThis study revealed the influence of thermal and centrifugal expansion on the fatigue life of angular contact ball bearings in high-speed service conditions.Peer reviewThe peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-03-2023-0065/

Fatigue Crack Growth Behavior of Different Zones in an Overmatched Welded Joint Made with D32 Marine Structural Steel

Applying fracture mechanics theory to heterogeneous welded joints might lead to an uncertain assessment of fatigue crack propagation behavior and, consequently, an inaccurate estimation of the cyclic loading capacity and fatigue life of welded structures. Combining experimental testing and analytical equations of the marine overmatched welded joints of D32 marine structural steel provided a view of the influence of strength heterogeneity on fatigue crack growth (FCG) behavior under constant cyclic loading. FCG testing was conducted using compact tension specimens under different stress ratios. The effect of residual stress on the FCG behaviors of the heat-affected zones (HAZs) and fusion zones (FZs) of the compact tension (CT) specimens was examined in the overmatched welded joints. Subsequently, the welding residual stresses were removed by post-welding heat treatment (PWHT) to focus the FCGR assessment on the microstructural effect. The results indicated that the FCG rates (FCGRs) of the FZ and HAZ materials obviously varied in as-welded and stress-relieved states. The existence of residual stress in the overmatched welded joints led to a decrease in FCG rates and prolonged the fatigue crack propagation life for the FZs and HAZs. Moreover, the FCGR increased in the base metal (BM), HAZ, and FZ with the increase in the stress ratio. The FCG curves of these materials were fitted to correct the stress ratios using the NASGRO equation. Finally, an analytical analysis of the FCGR based on the NASGRO equation revealed the relationship between different stress ratios for different materials.

Investigation of the Effect of Loading on Fatigue Life by Comparing Strain Gauge Measurements and Finite Element Analysis Under Gradually Increasing Load in An Axle Housing

In this study, the stress values obtained from commercial finite element analysis software ANSYS® and stress values measured by strain gauges applied on an axle housing in test environment were compared. The axle housing is a test sample from heavy duty commercial vehicles. Besides from stress values comparison, fatigue behavior of the housing was observed under gradually increased loading conditions via hydraulic loaded test benches. Load conditions, configuration change steps, test parameters and fatigue life results will be explained in detail. It was observed that the results of FEA and strain gauge are coherent to each other and as the load was increased, the fatigue life decreased. The stress values in specified points of housing increase linearly with the load increment. However, as predicted, the relationship between load change and fatigue life is not linear. For instance, fifty percent increase in load reduces life by about seventy-five percent. The aim of the study is firstly correlate the FEA results by comparing with the test measurements and then try to observe the effect of load increase on the fatigue life which will be a beneficial source for estimation of the life of the axle housing under diverse loadings in the further studies.

DIC-based constant amplitude and two-block loading fatigue life prediction of open hole GLARE laminate

The constant amplitude fatigue life is predicted using the normalized fatigue stress with the goodness of fit above 0.98. The crack initiation life was estimated based on the stress concentration factor and the surface axial strain measured by DIC. The high-low amplitude sequence two-block loading fatigue life was predicted using an iterative calculation method based on the corrected crack tip effective stress intensity factor range, almost all results are in a 1.3-scatter band. The previous nonlinear fatigue damage cumulative model was further modified for two-block loading, the life prediction results are within a 1.2-scatter band.

Coupled loads analysis of a novel shared-mooring floating wind farm

Shared mooring lines are a method to reduce the stationkeeping cost of floating offshore wind farms; however, their impacts on floating array dynamics are not yet well understood. This article presents advancements to floating wind farm simulation capabilities that allow the dynamic modeling of shared-mooring floating wind arrays—specifically, platform coupling through shared lines and proper phasing of wave loads across the array. These capabilities are demonstrated on a 10-turbine shared-mooring array featuring two staggered rows of wind turbines. A baseline array design with individually moored turbines is used as a basis for comparison. Coupled analysis using FAST.Farm shows that the shared-mooring design has smaller fluctuations in surge when compared to the baseline design. The mean and maximum platform offsets are highest in normal operating conditions, but the maximum mooring line tensions are highest in 50-year storm conditions. Power spectral density analysis of platform surge and sway motions shows that the shared mooring configuration does not introduce any significant inter-platform resonances. The tower-base bending moment statistics and the line tension damage equivalent loads indicate no consequential differences in turbine loading or mooring fatigue life. Anchor load analysis shows that the total required anchor capacity for the shared-mooring array is decreased by approximately 25% when shared anchors are used. Dynamic simulations of the shared mooring system under line failures show that remaining line tensions stay within bounds and that offsets are significantly smaller when compared to the baseline design. Overall, the results show that shared moorings do not introduce any dynamic response concerns in this floating wind array design.

Design of Downhole Robot Actuator System and Mechanical Behavior Analyses of the PRSM by Considering Elastic Errors and Radial Loads

This paper designs a new class of actuators for the downhole traction robot system to achieve high-accuracy transmission, which is realized by the planetary roller screw mechanism (PRSM). As the downhole environment is a non-structure one, which increases the difficulty of the load analyses and distributions of the downhole robot system to complete a predesigned mission. Traditional achievements about the mechanical behavior analyses of PRSM ignore the effects of radial loads and torque elastic deformation errors, which are inevitable for the downhole robot actuator, and the results of which would affect the load distribution and fatigue life of the PRSM-aided actuator. To assist the complex task, in this study the mechanical behavior analyses of PRSM for the downhole robot system are investigated by considering axial loads, torque elastic deformation errors, and radial loads. Moreover, the calculation models for contact load distribution and fatigue life are established by utilizing the equivalent contact load and Hertz contact theory. Two cases for the robot actuator in the downhole environment are addressed, the results of which indicate that the contact load change and decrease with the thread growth direction of the PRSM, the first several threads bore most of the loads, and the last several threads only took a few loads. Additionally, the fatigue life reduces sharply under the condition that the axial loads, radial loads, and rotation speeds increase. Compared with the other two effectors, the fatigue life is more sensitive to the radial loads. The results show the sustainability of the presented screw–roller–nut and provide a potential reference for the downhole robot actuator motion analyses.

Mechanical properties and failure behavior of flow-drilling screw-bonding joining of dissimilar aluminum alloys under dynamic tensile and fatigue loading

Flow-drilling screw (FDS) is a new type of single-sided joining process that is increasingly used to join dissimilar aluminum alloys in automobile lightweight. Fatigue failure and high-speed collision may occur in automotive joints under actual service conditions. This study proposed a joining process combining FDS and adhesive bonding to join dissimilar aluminum alloy sheets commonly used in body manufacturing. The adhesive bonding improved the joint strength and increased the failure distance of FDS joint. A thorough study of the FDS-bonding joining process on the mechanical properties and failure behavior was conducted. Specifically, a finite element analysis (FEA) model was built to predict the plastic deformation and stress distribution of the joints. Microstructure and hardness tests of the joints were performed to study the effect of plastic deformation during the joining process. The comparison of the mechanical properties and failure behavior of joints in dynamic tensile and quasi-static tensile tests showed differences and strain rate sensitivity. In addition, the maximum load–fatigue life (F-N) curves of dissimilar aluminum alloy joining were obtained by fatigue tests to predict the fatigue strength and failure life of the joints. Furthermore, the relationship between failure mechanisms and mechanical properties was established. This work provides a new industrial solution and failure performance reference for the requirement of composite structure and often one-sided access connection position in automobile industry.

Fatigue Performance of Rib Beam Bridge Slabs Reinforced with Polyurethane Concrete Based on the Damage Theory

In this paper, the rib beam bridge slabs were taken as the research object. Static load and fatigue tests were carried out on the benchmark bridge slabs to determine the ultimate load capacity and fatigue life of the bridge slabs. Then, the bridge slab was pre-damaged and reinforced with polyurethane concrete. A fatigue test was carried out on the reinforced bridge slab to study the fatigue performance. Based on the damage theory, the fatigue damage reinforcement finite element models of the bridge slabs under different damage degrees were established. The fatigue performance of the reinforced bridge slabs was systematically studied. The results show that the fatigue damage of the reinforced bridge slab developed in stages. Compared to the unreinforced bridge slab, the fatigue damage of the reinforced bridge slab was significantly reduced at each stage. According to the least square method and numerical analysis results, a residual-bearing-capacity model including damage degree and fatigue cycles of the reinforced bridge slabs is proposed, which can be used as a reference in bridge slab reinforcement design.

Determination method for metal bridge superstructure replacement priority using strength, economic and operational criteria

The article describes the problem arising from the setting trains with increased axleloads into operation on bridges with superstructures, engineered according to the old design standards. On the railways used riveted metal bridge superstructures, which require replacement due to significant corrosion, mechanical and fatigue damage, due to insufficient carrying load and residual fatigue life to pass the prospective load. Superstructures, designed in the 30s-40s, are more than 80-90 years used in conditions of a relatively difficult operation. During long-term operation, processes occur in elements and joints that lead to the formation and development of various hazard degrees damages, and failures. It is necessary to resolve the further exploitation issue of old bridge superstructures and their replacement. The author has applied the analyzing method of the criteria system, with the account of economic and technical capabilities for replacement priority determination of bridge superstructures. A set of criteria were proposed for solving this problem in digital form. Compiled matrices of pair-wise comparison, the comparison was performed using a relative importance scale with the test significance determination. By the linear algebra methods the eigenvector of matrix components values — local priorities — are calculated for each pair-wise comparisons matrix. As a result of calculations by the proposed criteria, were obtained global priorities for replacing options for riveted metal superstructures made by old design standards. The mathematical apparatus of the criteria hierarchy method is easy to use and allows you to get a solution in digital form, you can use other criteria.

Topology Optimization of Aircraft Components for Increased Sustainability

The aim of this work is to explore a topology optimization approach for the design of load-bearing aircraft components. The main objective of the approach is to develop a design methodology that reduces the maximum stress in a component for a given applied load and weight constraint. Consequently, the load carrying capacity and fatigue life of the component are maximized, resulting in less downtime and increased sustainability of the aircraft. A representative component geometry has been selected that is a potential candidate for additive manufacturing in order to enable the enhanced design freedom required of topology optimization approaches. Both linear and nonlinear-static finite element analyses are performed to validate the improved performance of the topologically optimized component, as well as contact analyses to demonstrate that the resulting design cannot be further improved without redesigning the complete assembly. The optimization problem is formulated and solved using a bidirectional evolutionary structural optimization method. The method demonstrates large reductions in maximum stress, leading to significant increases in fatigue life, potentially compensating for the degradation in fatigue properties inherent in additively manufactured metallic structures. The added design flexibility of additive manufacturing combined with topology optimization offer the potential for an anywhere, anytime manufacturing capability that would greatly benefit aircraft sustainability.

An improved manson-halford model for multi-level nonlinear fatigue life prediction

The Manson-Halford (M−H) nonlinear fatigue damage model is widely used for fatigue damage analysis. It, however, does not consider the load interaction effect. This paper presents an improved M−H model with a load interaction factor defined as the ratio of the first and second stress levels. The characteristic exponent of the M−H model is modified by multiplying the load interaction factor and fatigue life ratio. The characteristic exponent can consider the load interaction effect and the load sequence effect under multi-level loading. Experimental data from five materials under two-level and multi-level stress loadings verify the accuracy of the proposed model.

Analytical Determination of the Optimal Clearance for the Fatigue Life of Ball Bearing Under Different Load Conditions

Abstract In this paper, a comprehensive analytical model for the fatigue life prediction of ball bearing in various operating conditions is presented. Not only the internal clearance variations induced by the centrifugal expansion and assembly interference but also ball inertia forces and ball–raceway separations are fully considered in theoretical modeling to achieve accurate life prediction of the ball bearing. The model has been validated by comparison with the static results in previous literature. Based on this, the results of the load distribution and fatigue life versus the internal clearance of ball bearing under various operating conditions are studied. The results show that there is always an optimal clearance to maximize bearing fatigue life for the radial load or the combined load conditions, and the size of the optimal clearance for bearing life is determined by both the load conditions and rotating speeds to ensure the uniformity of the internal load distribution of the ball bearing. Therefore, the above-mentioned theoretical and conclusions can be used in structural design optimization and assembly parameters selection of ball bearing to maximize the life characteristic.