Thermo-mechanical Finite Element Analysis Research Articles

Numerical and Experimental Investigation on the Surface Defect Generation during the Hot Extrusion of Al6063 Alloy.

The surface quality control of extruded products is a critical concern in the home appliance manufacturing industry owing to the increasing need for products with a high surface quality, in addition to the essential mechanical properties of the final product. The underlying issue with achieving high-quality extrusion products is that surface defects, especially those resulting in surface gloss differences, called white line defects, are only observed after surface treatment. In this study, we aim to investigate the cause of white line defect generation on the surface of an extruded product. Accordingly, an experimental extrusion program is established using an L-shaped die that has a noticeable change in its bearing length along the inner corner of its cross-sectional profile. Laboratory-scale experiments were performed for the L-shaped extrusion of homogenized Al 6063 alloy at various ram speeds, in order to induce surface defects, considering the production yield rate required for mass production. Subsequently, the microstructural changes near the surface failure region were investigated using an arbitrary Lagrangian–Eulerian (ALE) technique-based thermomechanical finite element (FE) analysis. To scale-up the defect observation method from laboratory-scale to production-scale manufacturing and confirm the reproducibility of the surface defect, scaled-up L-shaped extrusions were performed in an actual industrial production line. Finally, the potential cause of white line defect generation is discussed by comparing the numerical and metallurgical analyses, including the scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD) observations.

Thermo-mechanical modeling of stacked die flash memory package EMI shielding layer crack under thermal cycling test

EMI (Electromagnetic Interference) shielding is widely used in electronic modules to reduce the coupling of radio waves, electromagnetic fields, and electrostatic fields to enhance electric performance (Liu et al., 2016). Some flash memory products are also equipped with EMI shielding for the desired electric requirements. In this paper, TCT (Thermal Cycling Test) reliability of metallic thin film EMI (Electromagnetic Interference) shielding layer, which is deposited on stacked die flash memory package top and sidewalls is studied. A crack in the EMI layer is observed under TCT (Thermal Cycling Test) experiment. Three-dimensional thermo-mechanical FEA (Finite Element Analysis) modeling is used to determine the root cause of EMI shielding layer crack, that is, the two stacks of stacked NAND dies causes stress concentration and plastic strain accumulation at the EMI centerline region where the local metallic EMI structure gets fatigued and finally cracks. In addition, simulation results explain the difference in EMI layer fatigue behaviors between two stacks and one stack NAND package, which is verified by experimental warpage test data and crack occurrence. Lastly, methods to improve EMI layer fatigue life under TCT for two NAND stacks package are suggested.

Experimental verification of computational and sensitivity analysis on substrate deformation and plastic strain induced by hollow thin-walled WAAM structure

PurposeThis paper aims to numerical and experimental analysis on substrate deformation and plastic strain induced by wire arc additive manufacturing.Design/methodology/approachThe component has the form of a hollow, rectangular thin wall consisting of 25 deposition layers of SS316L on an SS304 substrate plate. Thermo-mechanical finite element analysis was applied with Goldak’s double-ellipsoidal heat-source model and a non-linear isotropic hardening rule based on von Mises’ yield criterion. The layer deposition was modelled using simplified geometry to minimize overall pre-processing work and computational time.FindingsA new material modelling of SS316L was obtained from the chemical composition of the evolved component characterized by scanning electron microscope/energy dispersive X-ray and further generated by an advanced material-modelling software JMatPro. In defining heat-transfer coefficients, transient thermometric analysis was first performed in the bead and on the substrate, which was followed by an adjustment of the heat-transfer coefficients to reflect the actual temperature distribution. Based on the adjusted model and boundary conditions, sensitivity analysis was conducted prior to the ultimate simulation of substrate deformation and equivalent plastic strain. Furthermore, this simulation was verified by conducting a series of automated wire + arc additive manufacturing tests using robotic gas Metal arc welding with distortion measured by coordinate-measurement machine and equivalent plastic strain measured by optical three-dimensional-metrology measurements (Gesellschaft für Optische Messtechnik).Originality/valueIt can be concluded that a proper numerical computation using the adjusted model and property-evolved material exhibits a similar trend with acceptable agreement compared to the experiment by yielding an error percentage up to 30% for deformation and up to 21% for equivalent plastic strain at each individual measurement point.

Finite element simulation of residual stresses in welded steel butt joints and their experimental verification and mitigation

The localized, intense, and moving heat source existing in welded fabrication results in residual stresses and distortion. Residual stresses remain inside the material even after the external forces or thermal gradients are removed after welding. Residual stresses decrease fatigue life of the welded joint leading to premature failures and associated distortion cause problems in fitment during assembly. Estimation of residual stresses before actual fabrication is essential for elimination or mitigation after fabrication. In this work, finite element thermomechanical analyses are carried out to estimate the levels of residual stresses of thin welded similar butt joints of 1018 steel and SS 304 steel. The numerically obtained results of the joints are compared with experimental results of identical joint geometry, welding conditions, and material properties existing in the literature. The comparison of numerically obtained thermal histories with those from experiments yielded good agreements. Longitudinal residual stresses are found to be dominant and comparison of these longitudinal stresses with experimental data also found to be in good agreements. Further, the levels of residual stresses are computed with three different preheat temperatures (600°C, 700°C and 800°C) to study the effect of preheating temperature in the mitigation of residual stresses. It has been found that the peak value of longitudinal stress decreased considerably with preheat temperature. Increasing preheat temperature has a marginal reduction in the peak value of longitudinal stress.

An Experimental and Numerical Study of Quenching-Induced Residual Stresses Under the Effect of Dynamic Strain Aging in an IN718 Superalloy Disc

Abstract The effects of dynamic strain aging (DSA) on residual stresses generated in Ni-base superalloys during heat treatments are not well understood. In this study, the residual stress field induced by water quenching an IN718 disc while undergoing DSA is studied using coupled thermo-mechanical finite element (FE) analyses in conjunction with neutron diffraction (ND) measurements. A visco-plastic constitutive model that incorporates the effect of DSA is proposed to describe the experimentally observed negative strain rate sensitivity and abnormal temperature dependence phenomena in the stress–strain response of solid solution treated IN718. The predicted quenching residual stresses in the disc agree well with the ND measurements. Due to the DSA, a propagating high plastic strain rate region can be identified in the disc during the early stages of the quenching process. Due to the negative strain rate sensitivity and abnormal temperature dependence effects caused by DSA, the predicted residual stresses are approximately 10% greater than when those two effects are not accounted for. The effects of different convection heat transfer conditions in the FE model are examined and discussed. It is found that the convection heat transfer coefficients have a great influence both on the disc residual stresses and DSA-related plastic strain rate field predictions.

Fire performance of eccentrically-loaded square and rectangular tubed-reinforced-concrete columns

Tubed-reinforced-concrete (TRC) columns are gaining increasing popularity in engineering constructions, however, research on their fire performance is still limited and mainly focused on concentrically-loaded columns. In this study, extensive numerical analysis was carried out to investigate the performance of square and rectangular TRC columns under eccentric loading and exposed to ISO 834 standard fire. A sequentially-coupled thermo-mechanical finite element analysis (FEA) model was developed in ABAQUS and validated well against fire testing results. The high-temperature overall deformations, internal bending moments and cross-sectional load redistributions of square TRC columns with different load eccentricities were analysed. Parametric studies were conducted to investigate the influences of load eccentricity ratio, sectional aspect ratio, bending direction, fire protection thickness, sectional dimension, load ratio and slenderness ratio on the fire resistance of square and rectangular TRC columns. Load eccentricity was found to have a greater effect on the fire resistances of columns of lower slenderness than those of columns of higher slenderness. Rectangular TRC columns of sectional aspect ratios no larger than 2 could generally achieve identical buckling resistance as that of the equivalent square sections. The influences of sectional aspect ratio and bending direction on the column fire resistance were insignificant. A design method was then proposed for both the ambient-temperature and high-temperature designs of eccentrically-loaded square and rectangular TRC columns. The fire design method could cover both protected and unprotected TRC columns. The design method has been thoroughly validated against detailed FEA modelling and yields excellent agreements with the modelling results.

Thermomechanical finite element simulation and correlation analysis for orthogonal cutting of normalized AISI 9310 steels

A coupled thermomechanical finite element analysis is performed in order to simulate orthogonal cutting of normalized AISI 9310. Damage parameters are optimized to define the behavior of the material subjected to orthogonal cutting. AISI 1045, AISI 4140, and A2024-T351 are selected as precursors to validating the present finite element approach for orthogonal cutting of normalized AISI 9310. The numerical results obtained in this study include the average cutting force, residual stresses and strains, chip morphology, and tool temperature. These results are validated for each material with experimental results found in literature. The current study optimizes the Johnson–Cook damage parameters for steel materials in order to capture physical chip morphology. A correlation analysis is then performed using the validated finite element model for the AISI 9310 material to better understand the effect of specific input parameters such as the damage parameters, coefficient of friction, fracture energy, heat generation fractions and tool velocity on output results such as stresses and strains in the workpiece, chip thickness ratio and tool temperature. This analysis provides input-output relations for a physically reasonable range of input parameters and supports that the damage parameters, coefficient of friction, and fracture energy have a very strong influence on the residual stresses and strains, and the chip morphology. The coefficient of friction has a strong influence of tool temperature. Correlation analysis results can help manufacturers in understanding the nature of residual stresses and distortion, and in choosing optimized process parameters suitable for and applicable to the specific workpiece material. Tool wear that is observed in actual cutting of normalized AISI 9310 is also discussed. This study will benefit the manufacturing industry with the understanding of how specific cutting processing parameters will impact the distortions and residual stresses in the machined AISI 9310 parts.

Rapid tooling for injection molding inserts

Injection molding is a widespread manufacturing technology for mass production of polymeric parts. Conventionally, fused polymers are injected at high pressure in a metallic mold. This tool is typically characterized by high manufacturing costs and times, making the injection molding process not affordable for small batches or prototypal applications. Additive Manufacturing represents a practical solution to cut down tooling costs and times of molds and inserts. In this work, FDM (Fused Deposition Technology) has been considered as candidate technology to produce polymeric inserts for injection molding. Considering the commercially available filaments for FDM, a PEI (Polyetherimide) grade has been selected as tooling material for the injection of a part made of Polypropylene. The PEI grade represents a good compromise between manufacturing costs and thermo-mechanical properties required for the application. The PEI grade has been characterized with DSC (Differential Scanning Calorimetry), DMA (Dynamical Mechanical Analysis) and compression tests. The data gathered were used to set up 2D simplified thermo-mechanical finite element analyses, simulating the response of the PEI inserts subjected to repeated injection molding cycles. The simulations confirmed that the PEI grade is a good candidate tooling material but the progressive tool heating could lead to prolonged cooling time of the Polypropylene part. Finally, some PEI inserts were 3D printed with FDM and tested in a real injection molding machine injecting POM. In total, 20 POM parts have been injected correctly without relevant damaging of the PEI inserts.

Integration of artificial neural network with finite element analysis for residual stress prediction of direct metal deposition process

Direct Metal Deposition (DMD) process is considered to be an efficient and reliable manufacturing method for the production of complex parts in many design applications. The thermo-mechanical nature of the DMD process induces a significant amount of residual stresses and distortions on fabricated parts. Evaluation of residual stress distributions requires considerable amount of modeling and experimental works. Therefore, there is a need for an accurate, and feasible assessment method(s) for engineers to estimate residual stresses based on chosen process parameters and geometrical features of DMD built parts. A novel artificial neural network-based modelling approach integrated with finite element analysis is proposed to address shortcomings of conventional thermo-mechanical finite element-based models and improve the computational efficiency of predicting residual stresses of AISI 304 L parts built on the basis of the DMD process. Predicted results showed that the novel approach is capable of accurate and efficient prediction of residual stress distributions of three different geometric structures e.g. a plane wall shape, L-shape wall, and rectangular box structures. Furthermore, the computational time of predicting the residual stresses for the wall, L-shape wall, and rectangular box structures is significantly improved with respect to the classical finite element thermo-mechanical analysis.

Experimental investigation and numerical simulation on welding residual stress of innovative double-side welded rib-to-deck joints of orthotropic steel decks

An innovative double-side welded rib-to-deck (RTD) joint has been developed recently to enhance fatigue performance of orthotropic steel decks (OSDs) in steel bridges. The welding residual stresses (WRS) will lead to reduction in fatigue resistance of RTD joints in steel bridges. It is essential to study WRS and its distribution to estimate the fatigue resistance of innovative double-side welded RTD joints accurately. To investigate WRS caused by the double-side welding process, the experimental tests on four specimens of double-side welded RTD joints were carried out by means of longitudinal critical refraction (LCR) wave method. A sequentially coupled three-dimensional thermo-mechanical finite element (FE) analysis model was established to simulate the double-side welding process, and it was validated by the WRS results of experimental investigation. Then, the effects of welding parameters and geometric configuration of RTD joints on WRS and its distribution are analyzed by the validated numerical simulation. The results show a reasonable agreement between WRS simulation and the experimental data. WRS at the surface of weld seam and plate components is strongly affected by the welding speed, but comparatively weakly depends on the weld penetration rate, the assembly gap and the deck thickness.

Thermo-mechanical behavior of a full-scale energy pile equipped with a spiral pipe configuration

This study investigates the thermo-mechanical behavior of energy piles equipped with a spiral pipe configuration. The analysis is based on the results of a full-scale energy pile as well as three-dimensional thermo-mechanical finite element analyses. The thermo-mechanical behavior of two energy piles with five U-shaped pipes connected in series and parallel, characterized by the same total length of the piping network, is also analyzed numerically for comparison purposes. The results of this work highlight that energy piles equipped with a spiral pipe configuration are characterized by the lowest trends of average temperature variation and thermally induced vertical stress within their volume, as compared to energy piles equipped with five U-shaped pipe configurations connected in series or parallel. Considerable variations in temperature and thermally induced vertical stress arise in the vicinity of the piping network embedded in all of the considered energy piles. Nevertheless, energy piles equipped with a spiral pipe configuration appear the best solution for practical applications in comparison with U-shaped pipe configurations of the same total length, because they maximize the heat exchange that is achieved with the ground and minimize the associated thermally induced variations of their mechanical response.

Local-Induction-Heating Bending Process of B1500HS Thin-Walled Rectangular Steel Tubes: A Simulation and Experimental Investigation

To lighten and stiffen the structural components used in automobile bodies, the variable curvature local-induction-heating bending forming (VC-LIHBF) technology was developed. However, few studies have been conducted on the optimization of the structural and geometric parameters of the inductor and the parameters of the LIHBF process. This paper focuses on the improvement of the cross-sectional distortion and the forming limit of the thin-walled rectangular steel tubes (TWRSTs) without the mandrel support. In this work, a coupled thermo-mechanical finite element analysis (FEA) method is developed to investigate the structural and geometric parameters of the inductor and the deformation behavior during VC-LIHBF. The temperature distribution is calculated by the electromagnetic and heat transfer analysis, and the stress distribution is obtained by the deformation analysis. Experiments were carried out to validate the reliability of the proposed finite element model (FEM). The results indicate that the forming quality of the TWRST is significantly affected by the structural and geometric parameters of the inductor, the feed rate of the tube, the push speed of the bending roller and the distance between the inductor and the bending roller. The appropriate inductor and process parameters for a B1500HS TWRST were determined. The findings of this study may provide important guidance for practical manufacturing via the LIHBF process.

Fire safety engineering principles applied to a multi-storey steel building

In this paper, fire safety engineering principles were applied to a steel-framed office building. The case study consisted of a 15-storey steel moment-resisting frame designed in Japan. Once the performance criteria had been defined, two severe fire scenarios for the unprotected structure, implying a different degree of building collapse, were identified and modelled in zone models, OZone and consolidated fire and smoke transport (CFast), as well as in the computational fluid dynamics software Fire Dynamics Simulator (FDS). Based on the results of the fire development simulation, several finite-element thermo-mechanical analyses were performed with SAFIR. OZone and CFast models, which are much less computationally demanding, provided comparable failure mode and time with respect to FDS. Since the steel frame was seismically designed as a moment-resisting frame in the two main horizontal building directions, the columns were particularly stocky. Moreover, they were only partially heated because they were located on the compartment edges. For these reasons, columns did not exhibit failure, in contrast to the assumptions taken in the risk-ranking process in relation to the evaluation of the consequences, suggesting a revision of such estimations and a possible iterative procedure for the definition of critical fire scenarios for the structure.

Tribo-Brake Characteristics between Brake Disc and Brake Shoe during Emergency Braking of Deep Coal Mine Hoist with the High Speed and Heavy Load

The friction wear and thermal fatigue cracking of the brake shoe and friction-induced self-excited vibration (frictional flutter) of the disc brake can easily occur during emergency braking of a deep coal mine hoist with at high speed and with a heavy load. Therefore, tribo-brake characteristics between the brake disc and brake shoe during emergency braking of a deep coal mine hoist are investigated in the present study. Scaled parameters of the disc brake of a deep coal mine hoist are determined by employing the similarity principle. Friction tests between friction disc and brake shoe are carried out to obtain the coefficient of friction in the case of high speed and large specific pressure between the friction disc and brake shoe. Coupled thermo-mechanical finite element analyses of the brake disc and brake shoe are established to investigate temperature and stress fields of the brake disc and brake shoe during emergency braking, which is validated by the engineering failure case. Effects of braking parameters on flutter characteristics between the brake disc and brake shoe are explored by employing a double-degrees-of-freedom vibration mechanism model. The results show that the maximum temperature, equivalent Von Mises stress and contact pressure are all located at the average friction radii of contact surfaces of the brake disc and brake shoe during emergency braking. The cage crashing accident in the case of high speed and heavy load in a typical coal mine shows crack marks and discontinuous burn marks at central locations of brake shoe and brake disc surfaces, respectively, which indicates frictional flutter characteristics between brake disc and brake shoe. During emergency braking, flutter time duration decreases with increasing initial braking speed and damping parameter; the flutter amplitude and frequency of the disc brake increases with increasing normal braking load and stiffness, respectively.

Simulation methodology for the assessment of the structural safety of concrete tunnel linings based on CFD fire – FE thermo-mechanical analysis: a case study

This work aims to provide a comprehensive procedure for the assessment of structural safety of tunnel linings exposed to fire. To this purpose, numerical simulations that model the three fundamental features influencing tunnel fire safety design, namely fire dynamics, thermal behavior and structural response, are performed. Fire development within tunnel is simulated by applying advanced Computational Fluid Dynamics (CFD) techniques under a Fire Safety Engineering (FSE) approach. CFD fire simulation is carried out first, and then the results are transferred into a thermo-mechanical Finite Element (FE) model. A “sequentially coupled thermo-mechanical analysis” is then performed by linking a heat-transfer analysis that provides the temperature distribution within the lining with a refined non-linear mechanical simulation. A proper non-linear constitutive model for concrete subjected to high temperature, able to account the main features governing concrete behavior (i.e. cracking and crushing), is applied to the purpose. Comparisons in terms of structural results obtained by applying this coupled procedure and those obtained through a thermo-mechanical analysis adopting a standard time-dependent fire curve are provided. The importance of considering a refined simulation of the fire scenario is proved: from a structural point of view, significant differences concerning stress distribution and cracking development in the lining are indeed observed. Therefore, the use of a realistic model to describe fire development appears crucial to understand the behavior of unreinforced concrete linings subjected to fire and to control their possible weaknesses, such as the appearance of cracks.

ISO 834 standard fire test and mechanism analysis of square tubed-reinforced-concrete columns

The tubed-reinforced-concrete (TRC) column is an innovative steel-concrete composite column and its steel tube is terminated at beam-to-column connections to mainly work as hoop reinforcements without sustaining axial load directly. Fire performance of TRC columns differs from that of concrete-filled steel tubular (CFST) columns since the axial deformation behaviour of the TRC columns would mainly depend on the inner reinforced concrete and local buckling of steel tube is minimised. However, no research has been reported on the behaviour of square TRC columns under fire exposure. Five slender square TRC columns subjected to standard fire and axial loading were tested in this study and the effects of load ratio and load eccentricity were investigated. Failure mode of the test specimens was dominated by global flexural buckling, whereas tube local buckling was also observed. The experimental results show that load ratio has a significant influence on the fire resistance of test specimens while the influence of load eccentricity is marginal. A sequentially-coupled thermo-mechanical finite element analysis (FEA) model was developed using ABAQUS. This FEA model was validated well against the test results when using the measured column end rotations as realistic boundary conditions. Different from the case of a CFST column, the axial load applied to a TRC column in fire is mainly sustained by the concrete and reinforcing bars and the high-temperature capacity contribution of steel tube is neglectable. With the increase of exposure time, the applied load gradually transfers from concrete to reinforcements until the yielding of re-bars.

Pre-drilling Effect on Thermal Friction Drilling of Cast Aluminum Alloy Using Thermo-mechanical Finite Element Analysis

Thermal friction drilling is a non-conventional hole making process, which uses a rotating tool to penetrate the workpiece and create a bushing. Friction drilling of brittle cast alloys is likely to result in severe petal forming and radial fracturing. This research investigates the effect of pre-drilling diameter and depth on the produced bushing cracks and petal formations while drilling cast aluminum alloy (A380). A three-dimensional finite element model of high-temperature deformation and large plastic strain is performed by using ABAQUS software. Modeling by using dynamic, temperature-displacement, explicit, as well as the adaptive meshing, element deletion, interior contact, and mass scaling techniques, is necessary to enable the convergence of the solution. The finite element analysis results predict that the pre-drilling has a significant effect on the produced bushing shape. The effect of initial deformation decreases with pre-drilling, leading to fewer cracks and petal formations. Hence, the obtained bushing length increases, so providing a more load-bearing surface that leads to a stiffer joint. Additionally, the effect of pre-drilling on the produced temperature is studied, and the results reveal that by increasing the pre-drilling diameter or depth the temperature decreases. Therefore, less workpiece material melting occurs, which leads to less adhering on the tool surface, so fewer cracks and petal formations.

Experimental and numerical investigation of the thermo-mechanical behaviour of an energy sheet pile wall

One-of-a-kind experimental and numerical investigation is provided in this paper about energy sheet pile walls: earth retaining structures that embed heat exchanger probes within piles for the exploitation of shallow geothermal energy. The study resorts to the results of full-scale in situ tests and coupled three-dimensional thermo-mechanical finite element analyses of an energy sheet pile wall constructed in an underground station. In this context, an investigation about the influence of thermal boundary and initial conditions on thermo-mechanical behaviour of the energy sheet pile wall is performed. The addressed thermal boundary conditions are associated with the thermal load imposed on the considered foundation by the field environment and the geothermal operation of some energy piles constituting the wall. The addressed thermal initial conditions are associated with the undisturbed ground temperature field of the considered site. Based on a comparison between the experimental and numerical results, and the development of numerical sensitivity analyses, criticalities associated with the analysis and modelling of the thermo-mechanical behaviour of energy sheet pile walls are denoted. The results highlight that: a marked non-uniformity of the temperature field can characterise real applications of energy sheet pile walls, representing a significant challenge to capture numerically at all spatial locations; a comparable influence denotes thermal loads that derive from the field environment and the geothermal operation of energy sheet pile walls, deserving attention when modelling the behaviour of such geostructures; and a critical role of the initial thermal conditions is connected to the satisfactory understanding and prediction of the thermo-mechanical behaviour of energy sheet pile walls, requiring careful consideration for analysis and design purposes.

Effect of temperature on CFST arch bridge ribs in harsh weather environments

In a concrete-filled steel tube (CFST), dry shrinkage and creep produce a circumferential gap between the inner concrete core column and outer steel tube that is increased by harsh weather in cold regions. Thermomechanical coupling finite element analysis was performed to determine the temperature fields, stresses, and strains of CFST arch bridge ribs with circumferential gaps. A traction–separation law was developed for cohesive elements of the steel–concrete interface, which was applied to a parametric analysis on the CFST temperature field and stresses according to diameter. The results can help guide maintenance strategies for CFST arch bridges.

Three-dimensional coupled thermo-mechanical analysis for fatigue failure of a heavy vehicle brake disk: Simulation of braking and cooling phases

In this paper, transient coupled thermo-mechanical finite element analysis of a three-dimensional model of braking pairs (brake disk and brake pads) is accomplished in order to estimate temperatures and stresses in brake disk during a braking cycle, including braking and cooling phases, and calculate fatigue life. A nonuniform distribution of temperatures is revealed on the surface of the brake disk, gradually generating surface hot spots and hot bands with temperatures up to 800 °C that lead to an uneven distribution of thermal stresses on the frictional surfaces. According to the simulations, variations in the circumferential stress, which is mainly responsible for the cracking of the brake disk, can reach up to 400 MPa in the hot spot areas, depending on the braking configurations. The numerical results are also used to estimate the fatigue life of brake disk using the Smith–Watson–Topper model. The numerical model demonstrates a high accuracy of fatigue life estimation when evaluated by prior experimental studies, signifying the effects of hot spots in reducing the service life of brake disk. Results of the fatigue life estimation show superiority to the analytical method both in the accuracy of calculation and detection of the failure location.