Risk Of Fatigue Failure Research Articles

Fatigue reliability analysis of bogie frames considering parameter uncertainty

With the increasing service life of bogie frames, the risk of fatigue failure becomes significant, making fatigue reliability analysis crucial for ensuring operational safety. However, accurately analyzing fatigue reliability presents a significant challenge with uncertain factors such as load fluctuations, unstable material shaping, and dimensional manufacturing deviations. To address this, this paper establishes a comprehensive active learning reliability framework based on surrogate models, enabling high-fidelity modeling and precise fatigue reliability analysis of welded frames under parameter uncertainty. The material utilization method was developed using APDL for secondary development to efficiently evaluate frame fatigue failure indicators. The effectiveness of this method was validated by combining the improved Goodman-Smith fatigue limit diagram and test bench fatigue tests, which helped identify the locations on the frame most prone to fatigue fractures. An Atom Search Optimization-BP Neural Network surrogate model was established with the objective of maximum material utilization, and the fatigue reliability of the bogie frame was obtained by combining the active learning function and the Monte Carlo method. The results show that the uncertainty design parameters greatly impact the fatigue reliability of critical welded structures. The proposed method improves the accuracy and efficiency of the fatigue reliability analysis of the bogie frame.

Age- and sex-specific biomechanics and extracellular matrix remodeling of the ascending aorta in a mouse model of severe Marfan syndrome.

Thoracic aortic aneurysm (TAA) is associated with Marfan syndrome (MFS), a connective tissue disorder caused by mutations in fibrillin-1. Sexual dimorphism has been recorded for TAA outcomes in MFS, but detailed studies on the differences in TAA progression in males and females and their relationships to outcomes have not been performed. The aims of this study were to determine sex differences in the diameter dilatation, mechanical properties, and extracellular matrix (ECM) remodeling over time in a severe mouse model (Fbn1mgR/mgR = MU) of MFS-associated TAA that has a shortened life span. Male and female MU and wildtype (WT) mice were used at 1-4 mo of age. Blood pressure and in vivo diameters of the ascending thoracic aorta were recorded using a tail-cuff system and ultrasound imaging, respectively. Ex vivo mechanics and ECM remodeling of the aorta were characterized using a biaxial test system and multiphoton imaging, respectively. We showed that mechanical properties, such as structural and material stiffness, and ECM remodeling, such as elastic and collagen fiber content, correlated with diameter dilatation during TAA progression. Male MU mice had accelerated rates of diameter dilatation, stiffening, and ECM remodeling compared with female MU mice which may have contributed to their decreased life span. The correlation of mechanical properties and ECM remodeling with diameter dilatation suggests that they may be useful biomarkers for TAA progression. The differences in diameter dilatation and life spans in male and female MU mice indicate that sex is an important consideration for managing thoracic aortic aneurysm in MFS. NEW & NOTEWORTHY Using a mouse model (Fbn1mgR/mgR = MU) of severe thoracic aortic aneurysm in Marfan syndrome (MFS), we found that male MU aorta had an accelerated time line and increased amounts of dilatation, stiffening, and extracellular matrix (ECM) remodeling compared with female MU aorta that may have contributed to an increased risk of fatigue failure with cyclic loading over time and a reduced life span. We suggest that aortic stiffness may provide useful information for clinical management of aneurysms in MFS.

Kinematic analysis of engagement and bending capabilities of a point-of-care, incremental skeletal fixation plate bending system

The current standard of care for skeletal reconstruction surgery is to join skeletal disunions with fixation plates and these plates are most commonly fit to bones through manual bending. The bending procedure is often performed in the surgical operating theatre with specialized pliers or, if available, lengthy pre-operative bending to fit a 3D printed skeletal model prepared on computer as part of a virtual surgical plan. Manual bending of fixation plates by eye or to a model can take considerable time. Repetitive bending at a single location can result in work hardening that increases the subsequent risk of fatigue failure. However, incremental forming systems may provide a solution to automatically bend fixation plates accurately, rapidly, and as little at any one location as possible. This paper is an investigation of the kinematics and manipulability of two versions of an incremental fixture plate bending system for Point of Care Manufacturing (POCM) of craniomaxillofacial (CMF) skeletal fixation hardware. The Automatic Plate Bender (APB) v1 is a minimal POCM system that is designed for simple straight plates with a constant incremental pitch. The APB v2 is a more complex POCM that is designed to accommodate a larger variety of standard plates. Kinematic and manipulability analysis demonstrate the engagement and bend classes that each system can accomplish, and identifies a critical singularity in the APB v2 mechanism. The paper concludes with two case studies in which a path planning algorithm uses a manipulability analysis to avoid singularities during incremental bending.

Comparative analysis of offshore wind turbine blade maintenance: RL-based and classical strategies for sustainable approach

This study compares traditional methods like Corrective Maintenance (CM), Scheduled Maintenance (SM), and Condition-based Maintenance (CbM) with Reinforcement Learning (RL)-based offshore wind turbine (OWT) blade maintenance strategies. In order to address the dual challenge of minimizing carbon output while managing maintenance costs and operational efficiency, the study presents a mathematical model intended to estimate carbon emissions associated with OWT maintenance activities. The ability of the RL-based strategy to reduce the risk of fatigue failure in OWT blades and account for wind speed variability in maintenance schedule optimization is assessed. In order to provide a sustainable maintenance solution this strategy balances the trade-offs between economic profit and environmental effect. The findings demonstrate how RL can provide a balanced approach to maintenance that enhances both operational performance and environmental sustainability.

A physics-informed neural network approach for predicting fatigue life of SLM 316L stainless steel based on defect features

Defects in additively manufactured materials severely limit the performance of parts in practical applications, often exposing them to the risk of fatigue failure. In order to improve the reliability and performance of additively manufactured parts, it becomes crucial to accurately predict the fatigue life of the material. Although traditional semi-empirical formulas can assess the effect of defects on the fatigue performance of parts, they still lack detailed research and consideration of defect morphology features. Therefore, this study proposes a method based on Physics-Informed Neural Networks (PINN). This method improves the predictive capability of the model and enhances its interpretability by extracting the sensitive features of critical defects and embedding known physical knowledge or fracture mechanics methods as loss functions into the training process of the neural network. Additionally, the method effectively captures the complex relationship between defect features and fatigue life, providing a deeper understanding of the model prediction results. The results show that the PINN model considering feature-related knowledge has higher prediction accuracy and reliability, and all predicted fatigue life are narrowed within 2-factor bands, enabling more accurate prediction of fatigue life for SLM 316L stainless steel under different processing conditions.

Composite effects of residual stress and hardness gradient on contact fatigue performance of rough tooth surfaces and optimization design of detailed characteristic parameters

Residual stress and hardness gradient significantly affect the contact fatigue failure process of rough tooth surfaces, and the meticulous design of their characteristic parameters can help improve the fatigue resistance of gears. In this paper, an efficient computational method for rough tooth surface contact is established based on the reconstruction modeling of asperities and mixed lubrication analysis. By comprehensively considering the effects of residual stress and hardness gradient, the Dangvan multiaxial fatigue criterion is adopted to predict and analyze the contact fatigue life of the gear surface. The correlation between the surface residual stress, maximum residual stress depth, surface hardness, and effective hardening layer depth, among other characteristic parameters, and the contact fatigue performance of tooth surfaces is established. The results show that: (1) Increasing the magnitude of surface residual compressive stress and surface hardness can significantly reduce the risk of fatigue failure in the near-surface layer of the gear. To achieve the same fatigue performance, there is a linear negative correlation between the design values of the two parameters. (2) Affected by the double stress peaks in the rough tooth surface stress field, the maximum residual stress depth significantly affects the depth at which the highest failure risk occurs. With changes in roughness, the optimal design value of the maximum residual compressive stress depth changes from about 0.5 times the Hertzian contact half-width depth in the subsurface layer (Sa < 0.2 μm) to about 15 μm in the near-surface layer (Sa > 0.4 μm). (3) Considering both process cost and gear surface fatigue resistance, the design threshold for the effective hardening layer depth should be greater than the Hertzian contact half-width. This paper establishes a composite correlation between the meticulous characteristic parameters of residual stress, hardness gradient, and the contact fatigue performance of tooth surfaces, providing theoretical support for optimal design of tooth surface anti-fatigue performance.

Fatigue-sensitive feature extraction, failure prediction and reliability-based design optimization of the hyperloop tube

Hyperloop research focuses on investigating the design and limitations of its complex subsystems. However, the existing literature overlooks the fatigue failure characteristics of the Hyperloop tube, leaving future engineers without informed estimates of its reliability. To address this gap, this study examined the occurrence and prediction of fatigue failure in the Hyperloop system. The findings revealed that both the underground and above-ground configurations showed resistance to fatigue failure, with the underground system showing greater resilience. Additionally, sensitivity analysis highlighted support spacing, tube ultimate tensile strength, and tube radius as the most influential design variables affecting fatigue sensitivity. Moreover, a reliability-based design cost optimization was performed, taking into account demand uncertainty and utilizing insights from previous analyses to determine ideal design parameters. This research sheds light on critical design aspects of the Hyperloop tube that require intensified attention to effectively mitigate the risk of fatigue failure.

Development of a modified BEMT model for the analysis of helical bladed vertical axis tidal turbines

Development of a modified BEMT model for the analysis of helical bladed vertical axis tidal turbines &#x0D; Mohammad Fereidoonnezhad1, Seán Leen1, Stephen Nash1, Tomas Flanagan2, Patrick McGarry1&#x0D; 1 School of Engineering, University of Galway, Galway, Ireland&#x0D; 2 ÉireComposites Teo., Údarás Industrial Estate An Choill Rua, Inverin, Galway, Ireland&#x0D; E-mail: patrick.mcgarry@universityofgalway.ie &#x0D; &#x0D; Keywords: Blade element momentum theory, Helical vertical axis tidal turbine, FEA Analysis&#x0D; Classical blade element momentum theory (BEMT) formulations are not capable of accurately simulating complex blade geometries, such as spiral or helical blade geometries. In this paper, we develop a modified BEMT model to calculate hydrodynamic forces acting on the helical vertical axis tidal turbines. Our framework accounts for curved blade geometries where the leading edge is not orthogonal to the freestream velocity, and chord vectors are not in the azimuthal-radial plane. We validate the model using experimental data for a prototype VAWT. We then perform a parametric analysis of helical bladed VATT designs. Both the helix angle of the blade and the relative orientation of the chord strongly influence the power output of a turbine. Our modified BEMT model also predicts that an increase in blade helix angle results in reduced power fluctuations. Additionally, computed fluctuations in tangential and normal forces acting on blades are shown to reduce significantly with increasing blade helix angle, suggesting a reduction in risk of fatigue failure. We also uncover a complex distribution of normal and tangential forces along the length of a helical blade. Fluctuating hydrodynamic forces computed by our modified BEMT model are input into a finite element (FE) framework to compute the stress state in a fibre reinforced composite blade material for a range of blade azimuthal positions. Analyses reveal that blade deflections are three orders of magnitude lower than the turbine radius, suggesting that sufficient structural stiffness is achieved by the blade design. Results also uncover stress concentrations in the region of strut-blade connection, revealing a higher risk of fracture and fatigue failure at this location.

The Effect of Carburization and Repeated Heat Treatment with Different Solutions on the Fatigue Resistance of Medium Carbon Steel

Many mechanical parts are exposed to failure as a result of mechanical stresses for design or metallurgical reasons, and the phenomenon of fatigue represents the largest area and reaches (90%) of the faults of engineering parts that are subject to periodic stresses. The risk of fatigue failure occurs without warning, so the phenomenon of fatigue resistance has taken up a large part of the research and studies concerned with the dissolution of metals. This article aims to study the effect of fatigue resistance of ASTM 1050 steel. Carbonation, repeated quenching at different temperatures (780 &amp; 770℃) using seven different solutions, and tempering at repeated tempering after each quenching at temperatures (230 &amp; 250℃). The stress resistance of all the studied samples decreases after the second cooling in distilled water, with the exception of the samples that were initially quenched with the same solution and then quenched again. This is one of the most significant findings. Another finding is that following a second chilling in distilled water-based solution, the resistance to fatigue stress rises, increasing by up to (8.5%) in comparison to samples that were first quenched in the same solution then diluted.

Freespan Analysis for Subsea Pipeline Integrity Management Strategy

. Over a rough seabed or on seabed subject to scour, freespans can occur when contact between a subsea pipeline and the seabed is lost over an acceptable distance. When this exceeds the allowable freespan length, design stresses can be exceeded, and a vortex induced vibration (VIV) response can be initiated, resulting in the risk of fatigue failure. If this is not predicted and controlled properly, it will affect pipeline integrity, leading to expensive rectification and intervention work. Freespan analysis consisted primarily of a screening check in which the as-found freespans from Remotely Operated Vehicle (ROV) or multibeam Side Scan Sonar (SSS) inspection survey were compared against the design allowable lengths and determine the expected fatigue life of a freespan that may be experiencing Vortex Induced Vibration (VIV). Freespans are considered acceptable if the calculated fatigue life exceeds the design life criteria. This paper describes the freespan analysis that has been developed to perform detailed freespan engineering assessments, incorporating the latest survey and as-laid conditions. This analysis follows a methodology in standard code DNVGL RP F105 that has been accepted and used by operators to produce more accurate and less conservative freespan analysis results, leading to a subsea pipeline integrity management strategy with fewer unnecessary interventions and greater cost benefits.

Simulation Analysis and Experimental Study of the Strength of Aluminum Alloy Suspension Structure

High-speed trains have a large amount of ancillary equipment, which is suspended from the underside of the train by means of a suspension structure. Due to the large mass of the ancillary equipment, the suspension structure is subjected to various loads during train operation and there is a risk of fatigue failure. In this paper, the stress distribution at the suspension point and the lo-cation of the maximum stress point under load are investigated in detail based on actual test loads at the suspension point and finite element simulation analysis. In order to further investigate the fracture failure of the suspension points, experimental studies were carried out. Firstly, static strength tests were carried out to obtain the load-displacement curves of the structural members and to determine the fracture strength of the structure based on the displacement sensors, and secondly, fatigue tests at different stress levels were carried out to obtain the load-life curves of the structural members and to investigate the probabilistic load-life curves at different reliability levels. The test results show that the structural component has a high fracture strength of 65kN, while the conditional fatigue strength is relatively low, corresponding to a load level of 12.5kN at a median life of 106 cycles. The above research work provides the necessary basis for the design, optimization and reliability assessment of the suspension structures of high-speed trains.

Material damage integration approach for efficient modelling of high cycle fatigue

The recognition of the risk of fatigue failure and its study, particularly fatigue crack growth (FCG) behaviour of engineering materials, is not neoteric, and the majority of approaches for investigating the problem are empirical and dated. With recent computational advances, the cohesive zone modelling (CZM) approach for FCG analysis has become popular especially amongst researchers owing to its flexibility of use particularly within the finite element framework. However, the use of the CZM for explicit cycle-by-cycle high cycle FCG analysis of real structural components is still largely computationally prohibitive. Thus, this study presents a novel material integration (MI) approach to accelerate fatigue crack propagation within the cyclic cohesive zone modelling (CCZM) framework. Using a bilinear cohesive law, the proposed technique is compared with the Linear Extrapolation (LE) technique and assessed for three models of different bulk-interface element discretisation and deformations. The results show that the MI technique offers a more consistent approximation to the accelerated fatigue damage computation and, more importantly, better convergence characteristics for the different models under tension, mixed mode and bending deformations. These outcomes underline the computational benefits of the proposed MI technique in assessing the FCG behaviour of real structural components within the CCZM framework.

Experimental Study on Fatigue Performance of Welded Hollow Spherical Joints Reinforced by CFRP

The risk of fatigue failure of welded hollow spherical joints (WHSJs) under alternating loads increases due to the inherent defects, the disrepair, and the demand for tonnage upgrades, of suspension cranes. The finite element analysis results revealed that the ranking of the stress concentration factor at the WHSJ was as follows: weld toe in steel tube of tube–ball connection weld &gt; weld toe in steel tube of tube–endplate connection weld &gt; weld toe in sphere of tube–ball connection weld &gt; weld toe in plate of tube–endplate connection weld. Moreover, the peak stress at the weld of the tube–sphere connection was reduced by 32.93% after CFRP bonding reinforcement, which was beneficial for improving the fatigue performance. In this study, 16 full-scale specimens of Q235B WHSJs were tested by an MTS fatigue testing machine to study the strengthening effect of CFRP on the fatigue performance. It was found that the fatigue fracture of WHSJs was transferred from the tube–sphere connection weld to the tube–endplate connection after CFRP reinforcement. According to the fitted S-N curves, the fatigue strength could be increased by 13.26%–18.19% when the cycle number increased from 10,000 to 5,000,000.

Effect of internal defect on the low-cycle bending fatigue behavior of a single-strand wire rope

• The low-cycle bending fatigue behavior of a defective wire rope is analyzed. • The minimum fatigue life of the wire rope occurs near the defective area. • The internal defect increases the risk of stress yielding of the wire rope. • The internal defect reduces the minimum fatigue life of the wire rope. • An increment in radial position of defect causes a worse performance of the rope. In order to explore the evolution rules and failure mechanism of bending fatigue behavior of a defective single-strand wire rope under cyclic bending load, the influence of average stress and elasto-plasticity on the bending fatigue behavior is considered in this paper. Based on the characteristics of constant amplitude cyclic load, a finite element analysis model of the low-cycle bending fatigue behavior of the single-strand wire rope with an internal defect is established. Then the fatigue lives of the defective rope and non-defective rope are compared, and the influence of the defect’s radial position on the bending fatigue behavior of the rope is discussed. The results show that under the cyclic bending load, the minimum fatigue life of the defective rope in the cross section occurs in the defective area, while that of the non-defective rope lies in the interwire contact area. The defect changes the fatigue life distribution of the single-strand wire rope, and improves the fatigue life locally but reduces the rope’s bearing capacity. Additionally, a larger distance between the defect and neutral layer causes an earlier stress yielding in defective area and makes a greater risk of fatigue failure.

Numerical investigation on the effect of diameter ratio on wake induced vibrations of tandem cylinders

Numerical simulations of WIV (wake induced vibration) for tandem cylinders with different diameter ratio in the impingement regime are performed for a low Reynolds number of Re = 150 and low mass ratio of m* = 2.0. Five different diameter ratios of d/D = 1/2, 3/4, 1, 4/3, and 3/2 are examined, in order to identify the effects of diameter ratio on 2-DOF (two-degree-of-freedom) vibration responses of the cylinder in the range of 2≤Ur ≤ 14. The results show that the diameter ratio and vortex mode play important roles in the vibration amplitudes and frequencies of the downstream cylinder. The WIV can be further classified into WIEV (wake interference and enhancement vibration) and WCV (wake controlled vibration) according to two distinct mechanisms of the amplification of cross-flow vibration amplitude. As d/D ≤ 1, the vibration frequencies of the downstream cylinder are significantly pulled down and interfered by the small vortices shedding from the small upstream cylinder. Meanwhile, a wider range of lock-in and enhanced vibration amplitudes are the features for WIEV. The inline direction of the downstream cylinder have large response amplitudes in a wide range of Ur (reduced velocity) and reach to the maximum value at d/D = 1. As d/D > 1, the hydrodynamic characteristics of the downstream cylinder are mainly controlled by the larger vortices shedding from the upstream cylinder. The downstream cylinder vibrates as the vortex shedding frequency of the larger upstream cylinder and the lock-in phenomenon is absent. WCV significantly increases the risk of fatigue failure of the cylindrical structure.

Investigation of Transient Characteristics of a Vertical Axial-Flow Pump with Non-Uniform Suction Flow

The aim of this paper is to study the influence of non-uniform suction flow on the transient characteristics of a vertical axial-flow pump device. The unsteady calculation is employed to forecast the unstable flow structure with three inlet deflection angles α, and the calculation accuracy under uniform inlet flow is verified by the external characteristic test. The results depict that a promotion in the α will increase the head and shaft power and thus improve the stress and fatigue failure risk of the impeller. At the impeller inlet, the pressure pulsation intensity (PPI) with α = 40° is lower than that with α = 0° caused by a decline in the axial velocity. The dominant frequency of the unsteady pressure signal is the blade-passing frequency (BPF), and the dominant frequency amplitude rises with the increase in α due to the improvement of the pre-rotation impact intensity. At the guide vanes inlet, the dominant frequency of the unsteady pressure signal at the guide vane inlet is also the blade-passing frequency. An improvement in α magnifies the angle between the trailing edge jet of the impeller and the leading edge of the guide vanes under 0.8Qdes and 1.0Qdes, while it diminishes the angle under 1.2Qdes. Thus, the PPI and dominant frequency amplitude with α = 40° are higher than that with α = 0° under 0.8Qdes and 1.0Qdes, but these are lower than that with α = 0° under 1.2Qdes.

Mechanical behavior of hybrid glenoid components compared to all-PE components: a finite element analysis

PurposeThe purpose of this finite element study was to compare bone and cement stresses and implant micromotions among all-polyethylene (PE) and hybrid glenoid components. The hypothesis was that, compared to all-PE components, hybrid components yield lower bone and cement stresses with smaller micromotions.MethodsImplant micromotions and cement and bone stresses were compared among 4 all PE (U-PG, U-KG, A-KG, I-KG) and 2 hybrid (E-hCG, I-hPG) virtually implanted glenoid components. Glenohumeral joint reaction forces were applied at five loading regions (central, anterior, posterior, superior and inferior). Implant failure was assumed if glenoid micromotion exceeded 75 µm or cement stresses exceeded 4 MPa. The critical cement volume (CCV) was based on the percentage of cement volume that exceeded 4 MPa. Results were pooled and summarized in boxplots, and differences evaluated using pairwise Wilcoxon Rank Sum tests.ResultsDifferences in cement stress were found only between the I-hPG hybrid component (2.9 ± 1.0 MPa) and all-PE keeled-components (U-KG: 3.8 ± 0.9 MPa, p = 0.017; A-KG: 3.6 ± 0.5 MPa, p = 0.014; I-KG: 3.6 ± 0.6 MPa, p = 0.040). There were no differences in cortical and trabecular bone stresses among glenoid components. The E-hCG hybrid component exceeded micromotions of 75 µm in 2 patients. There were no differences in %CCV among glenoid components.ConclusionsFinite element analyses reveal that compared to all-PE glenoid components, hybrid components yield similar average stresses within bone and cement. Finally, risk of fatigue failure of the cement mantle is equal for hybrid and all-PE components, as no difference in %CCV was observed.Level of evidenceIV, in-silico.

Research of the major clinical findings of the use of reciprocant files: a systematic review

Introduction: In the context of root canal treatments, nickel-titanium endodontic rotary instruments fracture due to torsional overload or cyclic fatigue. Channels with bends located closer to the channel orifice and channels with double bends (S-shaped channels) have been shown to increase the risk of fatigue failure of rotating instruments. Thus, Yared was the first to report the use and effectiveness of reciprocating motions for rotary files, as he demonstrated that a single reciprocating file was sufficient to replace several files used in continuous rotation. Objective: A concise systematic review was carried out on the main results of clinical studies on the use of reciprocating files, to externalize the scientific evidence of these files to files used in continuous rotations. Methods: The present study followed the model of systematic literature review (PRISMA). The research was carried out from January 2022 to March 2022 and was developed based on Google Scholar, Scopus, PubMed, Scielo, and the Cochrane Library. The quality of scientific evidence of the studies was based on the GRADE instrument. The risk of bias was analyzed according to the Cochrane instrument. Results and Conclusion: A total of 85 articles were found. After the process of analyzing the quality of scientific evidence, 32 articles were selected. After analyzing the risk of bias, 8 recent clinical studies, from 2019 to 2022, were selected to compose this systematic review. Based on the clinical studies presented in the present study, it was evidenced that there is a significant statistical difference in the number of cycles in and out movement and wear time to failure between reciprocating and continuous rotary files. Furthermore, an endodontic treatment combining a single reciprocating file with a single cone showed similar clinical efficacy to treatment with hand file instrumentation and lateral compaction obturation. However, randomized clinical studies have shown that reciprocating instruments have less resistance to cyclic fatigue when operated in canals with curvatures in the coronal and middle thirds when compared with curvatures in the apical thirds.

Optimal life-cycle mitigation of fatigue failure risk for structural systems

Fatigue failure risk can be mitigated both by increasing the design fatigue capacity of the structural components and by conducting more frequent inspection and maintenance actions. The optimal combination of these two types of safety measure is structure dependent. It depends, among others, on the relative cost of the safety measures, the consequences of failure, the level of redundancy, the number of deteriorating components and the statistical dependence among components. In this article, a generic system representation is used to parametrise deteriorating structures according to these system characteristics. Based on this system representation, we investigate patterns of optimal life-cycle fatigue mitigation and provide recommendations for fatigue design. Results show that it can be cost-efficient to achieve system-level safety requirements with high component reliabilities at design and less frequent inspections. Furthermore, we show that the minimum requirements for fatigue design that are typically prescribed in design standards to avoid the need for inspections are not enough unless sufficient redundancy is ensured.

Fatigue failure risk evaluation of bimetallic rolls in four‐high hot rolling mills

AbstractIn hot rolling mills, bimetallic rolls are used because of the excellent hardness and wear resistance by applying high‐speed steel (HSS) and ductile casting iron (DCI). Because most of the previous studies focused on surface spalling, almost no study is available for internal fatigue failure based on the stress during the rolling. In this study, therefore, a three‐dimensional finite element method is applied to investigate the rolling stress of the work roll in the four‐high rolling mill. A suitable chamfer geometry in the backup roll is discussed as well as the standard wear profile by considering those effects on the fatigue. Then, to evaluate the fatigue risk under compressive mean stress, the fatigue limit lines in the stress amplitude versus mean stress diagram are newly discussed. With the aid of previous experience in industries, the fatigue fracture risk is discussed by focusing on three critical points inside the work roll.