Cumulative Damage Research Articles

Helmets with lattice liners can mitigate traumatic brain injury from impacts

This study explores the effectiveness of architected lattice structures, specifically made of PA12 material, as potential helmet liners to mitigate traumatic brain injuries (TBI), with a focus on rotational acceleration. Evaluating three lattice unit cell topologies (simple cubic, dode-medium, and rhombic dodecahedron), the research builds upon prior investigations indicating that PA12 lattice liners may outperform conventional EPS liners. Employing a high-fidelity finite element male head model and utilizing direct and oblique impact scenarios, mechanical quantities, such as maximum principal strain (MPS) and shear strain, cumulative strain damage measure and intracranial pressure were measured at the tissue level in different brain regions, Results indicate that lattice liners, especially with dode-medium topology, exhibit promising reductions in brain tissue strains. On average, during oblique impacts, less than 1 % of the brain volume experienced an MPS level of 0.4 when the lattice liners were adopted, whereas that percentage was above 70 % with the expandable polystyrene (EPS) foam liners. Pressure-based assessments suggest that lattice liners may outperform EPS liners in oblique impacts, showcasing the limitations of EPS for effective TBI mitigation. Despite certain model limitations, this study emphasizes the need for advancements in helmet technology, particularly in the development of commercial lattice liners using additive manufacturing, to address the limitations of existing EPS liners in preventing rotational consequences of impacts and reducing TBI.

Cumulative damage characteristics of rock samples under cyclic low energy inclined plane impact

The ore pass wall in underground mines is often damaged by the impact and wear caused by unloaded ores. Studying the mechanisms of rock damage and failure under different impact angles can provide technical insights for the design and maintenance of the ore passes. This study employed an inclined impact experimental device along with a drop hammer loading test machine to perform cyclic low-energy impact tests on sandstone samples at five different inclined plane angles. The porosity of the rock samples was measured using a nuclear magnetic resonance (NMR) detection system, which provided data on porosity, T2 spectrum distribution, and NMR images of the samples after different numbers of impacts at different slope angles. The results indicate that: (1) Under cyclic inclined plane impact loading, an increase in the inclination angle, leads to reduced damage to the rock sample. The rock sample impacted at a 45° inclined plane exhibited the most severe damage. Rock samples with large inclination angles are more prone to experience rupture fractures at the tip of the inclined plane, primarily due to shear-tensile failure. The porosity changes dramatically at initially slope angles, resulting in greater damage. (2) As the number of impacts increases, the porosity of the samples first decreases, then increases, and subsequently decreases again. This progression corresponds to the closure of large pores following the first impact, followed by the expansion of micropores into macropores after 5 impacts, ultimately leading to gradual degradation of the samples until failure. (3) As the number of impacts increases, new cracks form within the rock sample and small cracks expand. Despite an increase in the number of micropores, the macropores still exert a significant influence on the rock samples, with the macropore spectrum area accounting for over 95%.

Study on Mechanical Properties and Fatigue of Cold-rolled Steel Plate for Distribution Transformer

The oil tank steel plate of the distribution transformer is covered with welds, and the fatigue failure of the oil tank often occurs in the internal defects of fillet welds. Given the above problems, this paper puts forward the bearing capacity calculation formula of cold-rolled steel plate and carries on the force analysis of steel plate and the fatigue analysis of weld through finite elements. Based on the theory of plastic limit design, the ultimate flexural bearing capacity of the control section of steel plate members is proposed. The calculation formula of equivalent structural stress is given based on the calculation method of structural stress and linear elastic fracture mechanics, and the calculation method of fatigue life and fatigue cumulative damage is given. Then, the elastic-plastic equation is solved according to three criteria: Mises yield criterion, plastic flow criterion, and strengthening criterion. Based on the above numerical simulation analysis, the mechanical model of steel plate weld is constructed, the mesh is divided, the boundary conditions are restricted and the same load is applied. ABAQUS analysis results show that the stress distribution curve of the connector has a maximum value at X = 80 mm and X = 210 mm, that is, the top surface of the connector steel plate has an obvious stress concentration at 80 mm and 210 mm. When the length of the weld is not more than 60 times the size of the welding foot, the full section of the core plate will yield, and the maximum stress value of the weld element will not exceed the tensile strength value of the welding material. The error of the results calculated by the formula in this paper is mostly within 10%, and the rest is basically within 20%. Therefore, the bearing capacity formula of the steel plate in this paper has ideal calculation accuracy and can provide effective guidance for the design of distribution transformer oil tanks.

Celastrol attenuates the invasion and migration and augments the anticancer effects of olaparib in prostate cancer

BackgroundProstate cancer (PCa) is a leading malignancy among men globally, with rising incidence rates emphasizing the critical need for better detection and therapeutic approaches. The roles of HSP90AB1 and PARP1 in prostate cancer cells suggest potential targets for enhancing treatment efficacy.MethodsThis study investigated the overexpression of HSP90AB1 and PARP1 in prostate cancer cells and the impact of HSP90AB1 knockdown on the sensitivity of these cells to the PARP inhibitor olaparib. We also explored the combined effect of olaparib and celastrol, an HSP90 inhibitor, on the clonogenic survival, migration, proliferation, and overall viability of prostate cancer cells, alongside the modulation of the PI3K/AKT pathway. An in vivo PC3 xenograft mouse model was used to assess the antitumor effects of the combined treatment.ResultsOur findings revealed significant overexpression of HSP90AB1 and PARP1 in prostate cancer cells. Knockdown of HSP90AB1 increased cell sensitivity to olaparib. The combination of olaparib and celastrol significantly reduced prostate cancer cell survival, migration, proliferation, and enhanced cumulative DNA damage. Celastrol also downregulated the PI3K/AKT pathway, increasing cell susceptibility to olaparib. In vivo experiments demonstrated that celastrol and olaparib together exerted strong antitumor effects.ConclusionsThe study indicates that targeting both HSP90AB1 and PARP1 presents a promising therapeutic strategy for prostate cancer. The synergistic combination of celastrol and olaparib enhances the efficacy of treatment against prostate cancer, offering a potent approach to combat this disease.

Study on the Degradation Model of Service Performance in Railway Steel–Concrete Composite Beams Considering the Cumulative Fatigue of Steel Beams and Studs Based on Vehicle–Bridge Coupling Theory

The steel–concrete composite beam, as a structural form that combines the advantages of steel and concrete, has been applied in railway engineering. However, with the increase in railway operation time, the degradation pattern of the service performance of steel–concrete composite bridges remains unclear. This paper proposes a method for calculating the long-term service performance of railway steel–concrete composite beams, considering the cumulative fatigue damage of steel beams and studs, based on the vehicle–bridge coupling theory and Miner’s linear cumulative damage criterion. The proposed method is validated using measured data from an in-service steel–concrete composite railway bridge with spans of 40 + 50 + 40 m. The calculated mid-span vertical displacement and the first two natural frequencies of the composite beam deviated from the measured results by only 2.1%, 7.7%, and 9.5%, respectively. The research results can provide a basis for extending the service life of composite beams and preventing the occurrence of safety accidents.

The Impact of Age and Gender on Periodontal Conditions in Iraqi People: A Retrospective Study

Background: Periodontal disease is initially associated with a bacterial infection, such as dental plaque. With aging, the prevalence of periodontal diseases increases, and periodontal destruction in older individuals is due to cumulative damage rather than cumulative rates of devastation. Objective: To assess the effect of gender and age on periodontal health in selected Iraqi populations. Methods: The cross-sectional retrospective study analyzed the periodontal records of patients from October 2021 to June 2023. The study was conducted at the Dentistry Department, Al-Rafidain University College, Baghdad, Iraq. The sample was taken from patients who visited the periodontal department. A total of 508 subjects, with an age range of 10-69 years (35.23±10.25), participated in this study, including 287 males and 221 females. The sample was classified based on age and sex into 5 groups. The clinical evaluation includes plaque index (PLI), gingival index (GI), probing pocket depth (PPD), and clinical attachment loss (CAL). Results: The overall percentage of chronic gingivitis was 53.94%, while the percentage of chronic periodontitis was 46.06%. The 60–69-year-old group reported the highest rate of patients with chronic periodontitis. Additionally, the 10–19-year group showed the highest percentage of patients with chronic gingivitis. Conclusions: The prevalence of chronic periodontitis increases with age, and it is higher among females than males. Clinical periodontal parameters such as plaque index, probing pocket depth, and clinical attachment level are higher in older age groups than in younger age groups.

Experimental investigation on shear fatigue behavior of perfobond strip connectors made of high strength steel and ultra-high performance concrete

This paper explores the fatigue performance of perfobond strip connectors (PBL) made from high-strength steel (HSS) and ultra-high performance concrete (UHPC) by fabricating and testing eight push-out specimens. The failure modes, load-slip curves, stiffness degradation, and residual strength of the PBLs are presented and discussed. The experimental results show that fatigue loads caused connector’s crack formation and stiffness degradation, leading to concrete dowel shear fracture and transeverse rebar bending-shear rupture damage. Compared to the static performance, the fatigue residual strength of the PBL subjected to 0.5 × 106, 1.25 × 106, and 2.0 × 106 loading cycles decreases by 1.2 %, 3.6 %, and 14.5 %, respectively, with corresponding reductions in ductility of 14.7 %, 19.4 %, and 4.7 %. Under the same loading cycles, the fatigue residual strength and ductility of the PBL with a maximum repeated load of 0.65Pu are 13.0 % and 3.9 %, respectively, smaller than those of 0.55Pu. A semi-empirical model based on the elastic foundation beam theory and linear cumulative damage model is developed to predict the residual strength of the PBLs using HSS and UHPC. The accuracy and applicability of the model are calibrated using the experimental results. The findings of this study can serve as an experimental foundation and theoretical reference for the fatigue design of PBLs made with high-strength materials.

Extracorporeal membrane oxygenation ameliorate hepatic injury in brain death rat donors with hemodynamic instability.

Donation after brain death (DBD) serves as the primary source for liver transplantation. However, livers obtained through DBD often incur damage due to unstable hemodynamics, potentially impacting transplantation outcomes. Extracorporeal Membrane Oxygenation (ECMO) emerges as an optimal technique for donor liver retrieval and has found application in clinical settings. Despite its clinical implementation, the precise mechanisms through which ECMO enhances liver functions remain elusive. This study aims to investigate the mechanisms underlying how ECMO ameliorates liver function in brain-dead donors. We randomly assigned 18 male Sprague-Dawley (SD) rats (350 ± 50 g) into three groups: Con (n = 6), DBD-assisted drug (n = 6), and DBD-assisted ECMO (n = 6). After 3 h of ECMO, the rats were sacrificed. We assessed and compared changes in heart rate, blood pressure, cumulative liver damage (evaluated through HE and TUNEL staining), serum levels of AST and ALT, alterations in serum oxidative stress factors (MDA, H2O2, SOD, and 8-OHdG), and serum concentrations of related inflammatory factors (interleukin [IL]-1β, IL-6, IL-8, and TNF-α) among rats in the Con, DBD-assisted drug, and DBD-assisted ECMO groups. Subsequently, we established a rat orthotopic liver transplantation (OLT) model and transplanted livers obtained through the aforementioned methods. The post-transplantation status of the livers was observed. After 3 h of brain death, liver injury worsened, accompanied by a significant increase in serum transaminases, inflammatory responses, oxidative stress, and TUNEL staining. Strikingly, ECMO not only stabilized hemodynamics after DBD but also mitigated liver damage, leading to an alleviated status post liver transplantation. ECMO stabilizes hemodynamics, attenuates inflammatory responses and oxidative stress, thereby enhancing the quality of liver grafts for transplantation.

Evolution and Characterization of Uniaxial Compression Damage of Coal Measure Rock

In order to study the evolution law of uniaxial compression damage and its characterization method, three kinds of rocks with different lithology that commonly exist in coal measure rock were taken as the research objects to explore the relationship between their mineral composition, microstructure and mechanical properties, and the feasibility of acoustic emission (AE) characteristic parameters and AE spatial location to characterize the evolution process of uniaxial compression damage of rocks was compared and analyzed. A damage constitutive model based on AE cumulative ringing count was established and verified by numerical simulation. The results show that the differences in the micromorphology and mineral composition of coal measures with different lithology directly affect their physical and mechanical properties and load damage characteristics. AE characteristic ringing count can effectively represent the damage evolution process of rock during loading. Based on rock porosity characteristics and AE cumulative ringing count during loading, a constitutive model considering initial damage and cumulative damage was established. The theoretical analysis results of the damage constitutive model are in good agreement with the results of laboratory experiments and numerical simulation, which can be used to analyze the damage process of coal measure rock under load.

Hysteresis Model of RC Column Considering Cumulative Damage Effect under Variable Axial Load

Hysteresis Model of RC Column Considering Cumulative Damage Effect under Variable Axial Load

Evaluation of Cumulative Damage and Safety of Large-Diameter Pipelines under Ultra-Small Clear Distance Multiple Blasting Using Non-Electric and Electronic Detonators

The safety assessment and control of large-diameter pipelines under tunnel blasting at ultrasmall clear distances is a significant problem faced in construction. However, there has been no reference case for the quantitative comparison of the disturbance degree of surrounding rock by using two blasting schemes of non-electric detonator design and electronic detonator design under a similar total blasting charge consumption. In this study, the blasting test was carried out based on the engineering background of drilling and blasting methods to excavate the tunnel under the water pipeline at a close distance. The peak particle velocity (PPV), stress, and deformation responses of the pipeline under the two construction methods of non-electric and electronic detonators were comparatively analyzed. The PPV can be remarkably reduced by 64.2% using the hole-by-hole initiation of the electronic detonators. For the large-diameter pipeline, the PPV on the blasting side was much larger than that on the opposite side because the blasting seismic wave propagated a longer distance and attenuated more rapidly, owing to its greater cavity vibration reduction effect. The PPV of the electronic detonators decayed more slowly than that of the non-electric detonators. The cumulative damage caused by consecutive hole-by-hole blasting using electronic detonators was less than that caused by simultaneous multi-hole initiation using non-electric detonators, with a reduction of about 50.5%. When the nearest peripheral holes away from the pipeline are detonated, the cumulative damage variable D and damage range increase rapidly. The PPV, dynamic tensile strength, and cumulative damage variables were used to evaluate the safety of the pipelines.

Theoretical and experimental study on the damage behavior of bolted joints under cyclic loads

This paper presents a quasi-static and dynamic experimental study on the damage behavior of bolted joints. It proposes a 7-parameter theoretical model to accurately describe the damage properties of bolted joints during both micro- and macro-slip stages under cyclic loads. Results from quasi-static experiments indicate that under the preload of 12.4 kN, a ratcheting effect is observed during the micro-slip stage, reflecting the cumulative plastic damage process at the bolted interface. The macro-slip force exhibits a linear decrease with increased loading cycles. In the initiation of macro-slip, energy dissipation exhibits unstable characteristics, manifested as an "S"-shaped curve in the energy dissipation-applied force relationship. The proposed model can well describe bolted joints' observed energy dissipation characteristics.

Damage evolution and acoustic emission characteristics of sandstone under different true triaxial cyclic loading and unloading modes

In the process of deep coal mining, the cyclic mining disturbance behavior produces significant cyclic loading and unloading effects, to ensure safe production in the mining area, it is necessary to study the damage characteristics and acoustic emission characteristics of the rock body under different cyclic loading and unloading effects. This study developed a TAWZ-5000/3000 rock true triaxial (disturbance) test system and used it to carry out true triaxial cyclic loading and unloading tests in different modes, with acoustic emission (AE) monitoring of the deformation and damage processes. The test results proved that a large number of cycles weakens the rock’s ability to control deformation, and this weakening ability is also related to the types of cyclic loading and unloading modes. The hysteresis loop characteristics and mechanical parameters show obvious path dependence. Based on the damage equivalence method, it is found that the absolute damage parameter increases with the increase of the number of cycles in the same mode, and the accumulation rate of the cumulative damage parameter is faster; the cumulative damage parameter in the equal amplitude cyclic loading and unloading (EAC) mode is always higher than that in the other two modes. The normalized AE ring count rate in the rock samples under cyclic loading and unloading has a significant relationship with the damage percentage, and the crack extension scale function (b-value) shows the “steady increase – strong fluctuation − significant decline” trend. By analyzing the AE characteristic parameters, namely rise time/amplitude (RA) and ringing count/duration (AF), it is found that the sandstones in EAC, graded cyclic loading and unloading (GC), and stepped cyclic loading and unloading (SC) modes are mainly damaged by tension-shear and shear, respectively. By analyzing the values of the acoustic emission parameters RA-AF, it is found that the sandstone is mainly damaged by tensile shear, tensile tension, and shear under EAC, GC, and SC modes, respectively, corresponding to the rock samples’ damage patterns. The study results have important guiding significance for preventing and controlling disasters in deep mines.

Lifespan Evaluation for a Standard RV Reducer based on Fatigue Strength Theory

Rotate vector (RV) reducers are the two-stage deceleration device comprising involute and cycloid-pin gear transmission mechanisms. As the typical deceleration elements, they are widely applied in industrial robots, digitally controlled machine tools and automation fields due to their compact structure and high precision. However, a reducer may lose precision after a long-term operation. Moreover, pitting and metal peeling of internal components may also occur, leading to a fatigue failure. Therefore, it is necessary to conduct investigations on lifespan evaluation for RV reducers. In this study, the CRV-80E reducer is taken as the research object. Firstly, according to its transmission characteristics, the lifespan evaluation model for a standard RV reducer is established based on fatigue strength theory and Palmgren-Miner linear cumulative damage law, with the internal crankshaft bearing is considered as the key component. Then, the simulations are carried out on crankshaft bearing by the ANSYS Workbench and SKF SimPro. The contact stress, deformation on bearing rollers, and the rated lifespan of the reducer are simulated. Finally, the accelerated life test is conducted on an RV reducer by increasing the external load with the positioning precision as an output and criterion. After the test, the reducer is disassembled, and metal peeling failure is observed on the crankshaft bearing while other parts are relatively intact. The test results validate the feasibility and accuracy of the service life evaluation model and simulation analysis. This study provides a new research approach for researchers and manufacturers and a design reference for engineers to improve the lifespan of RV reducers by optimizing crankshaft bearings, which have a certain academic value.

The effect of ionizing radiation on hydrated fungal cells: Implications for planetary protection and mars habitability

Liquid water is one of the essential conditions for life as we know it. Its presence has been currently reported beyond Earth. Geological and mineralogical evidence indicates that water once flowed on Mars. The recent discovery of present ice-water on the planet's surface is one of the driving factors for life-detection missions. The highly radiative Martian surface, combined with aqueous thin layers, is prohibitive for the presence of hypothetical forms of terrestrial-like life on the planet. In this context, we examined the survival of hydrated colonies of the Antarctic black fungus Cryomyces antarcticus, which thrives in the extreme environment of McMurdo Dry Valleys in Antarctica, after the exposure to increasing doses of space relevant γ-rays. Results suggest that water significantly reduces the number of survivors at the lowest doses, while at the higher dose (117 kGy) the cumulative damage caused by radiation could no longer be counteracted by dehydration.

Damage-driven framework for reliability assessment of steam turbine rotors operating under flexible conditions

The high-temperature rotating structures (HTRS), e.g., steam turbine rotors, often operate in extremely harsh environments with a flexible load condition during peak shaving of power system. In this work, a damage-driven framework for reliability assessment is developed in terms of the cumulative damage-damage threshold interference (CD-DT) principle, in which the cumulative damage and damage threshold are regarded as two random parameters to address uncertainties. The CD-DT principle is founded on the engineering damage theory and incorporates physics-of-failure into the probabilistic modeling of high-temperature structural reliability. Probabilistic damage analysis, correlation analysis of weak sites, system-level reliability analysis, and sensitivity analysis have been encompassed in this framework. Three numerical examples are used to verify the effectiveness and applicability of the proposed framework. Application to steam turbine rotor involving multiple weak sites with multi-damage modes illustrate the implementation procedures of the framework. Results show that the reliability-based design life of rotor decreases with the increases of start-stop frequency, the implementation of a two-shift operation would pose a threat to meeting the safety requirement of a 30-year design life. Furthermore, sensitivity analysis highlights the critical influences of initial rotor temperature and speed rising rate on rotor reliability, providing insights for operational maintenance and reliability optimization.

Crack arrest characteristics and dynamic fracture parameters of moving cracks encountering double holes under impact loads

Brittle materials such as rock or concrete contain a large number of micro-cracks, voids, and other defects. Under external impacting loads, the interaction between fissures and holes affects the bearing capacity and stability of Engineering structures. To study the interaction mechanism between moving cracks and circular holes, A large-size semi-circular notched with a fissure and double circular hole (SNFDH) specimen was suggested in this research, and the dynamic fracture tests were carried out on the SNFDH specimens with different double circular hole spacing (35mm, 40 mm, 45 mm, 50 mm, 55 mm, 60 mm, and 70 mm) using a drop hammer impact test device. Crack propagation gauges were employed to track the time and velocity at which the crack propagated along its trajectory. Dynamic Drucker-Prager yield criterion and the cumulative damage failure criterion were used in the numerical simulation of SNFDH concrete materials. The program AUTODYN was employed to simulate the crack growth characteristics when a crack encounters the double hole. The program ABAQUS was applied to calculate the dynamic fracture parameter of cracks. The test results manifest that the crack propagating trajectory has three different characteristics according to the double hole spacing; the double circular hole has an arresting function for a moving crack; the size of the double hole spacing has a significant effect on the crack propagating velocity, crack propagating length, dynamic stress intensity factor and dynamic energy release rate; the configuration of the SNFDH specimen can be used to investigate the crack arrest mechanism when moving crack encountering double holes.

Mechanism of rockburst induced by the microseismic event in the floor strata of high tectonic stress zones: A case study

With the increase of mining scope, rockburst occurs frequently, but its generation mechanism has not been understood comprehensively. Based on a rockburst in the coal pillar area of high tectonic stress zones (HTSZs), this study analyzed the distribution characteristics of large-energy microseismic (MS) events by using data statistics. The mechanical cause of the MS event that induced the rockburst was revealed by means of seismic moment tensor inversion. On this basis, by using numerical simulation, this study explored the distribution characteristics of static load in rockburst area and the effect of dynamic load in the floor, and then proposed the rockburst mechanism. The results show that under the squeezing action, the floor strata in HTSZs implode and transmit energy outward in the form of stress waves. This causes the cumulative damage and stress of the coal body in the fast track of coal pillar area increase in a short time. Since the coal in this area has already been in the critical stress state, small stress changes may lead to coal failure and rockburst. In this case of rockburst, the high static load of coal is the main force source, and the dynamic load plays a role in increasing coal body damage and inducing rockburst. Combined with seismic moment tensor inversion and numerical simulation, this paper proposes a rockburst research scheme, which makes the simulation of dynamic load more reasonable. The results provide the theoretical basis for rockburst control under similar conditions.

A novel approach for analyzing linear amplitude sweep (LAS) test data of asphalt binders

Fatigue cracking is one of the crucial distresses considered for the design of flexible pavements. The initiation of fatigue cracking occurs in the binder phase of an asphalt mixture. The linear amplitude sweep (LAS) test was developed to analyze the fatigue damage in the asphalt binder. AASHTO T391 provides a method to analyze the LAS test data by fitting a power equation between the fatigue parameter (G*sinδ) and damage intensity. This method has some inherent weaknesses of overfitting or underfitting of the data at different damage levels. This study proposes a new method where a total curve is divided into two parts that fit the data in two different equations and then sum them up. The first part comprises of the data up to cumulative damage corresponding to the maximum effective stress, and the second part consists of accumulated damage in the material till it reaches the maximum strain (30 %). This method is called the bifurcation method in this paper. LAS test data of 27 long-term aged bitumen samples having different physical properties is used to determine the number of fatigue life cycles (Nf) by these two methods, and results are compared in terms of mean absolute percentage error (MAPE), root mean square error (RMSE), and residual sum of squares (RSS). It is shown that there is a significant reduction in the errors when the data fitting was done using the proposed bifurcation method. Further, the ranking was allotted to the samples based on the number of fatigue life cycles (Nf) at three different strain levels (2.5 %, 5 %, and 10 %) at intermediate-temperature conditions estimated using two methods. The shift indicator parameter was used to analyze the variability in the ranking of the samples due to changes in the strain levels. The study concludes that the proposed bifurcation method fits the predicted values more accurately than the prescribed power law.

Fatigue research of metro car body based on operational loads

PurposeThe principle of infinite life design currently directs fatigue resistance strategies for metro car bodies. However, this principle might not fully account for the dynamic influence of operational loads and the inevitable presence of defects. This study aims to integrate methods of service life estimation and residual life assessment, which are based on operational loads, into the existing infinite life verification framework to further ensure the operational safety of subway trains.Design/methodology/approachOperational loads and fatigue loading spectra were determined through the field test. The material test was conducted to investigate characteristics of the fracture toughness and the crack growth rate. The fatigue strength of the metro car body was first verified using the finite element method and Moore–Kommers–Japer diagrams. The service life was then estimated by applying the Miner rule and high-cycle fatigue curves in a modified form of the Basquin equation. Finally, the residual life was assessed utilizing a fracture assessment diagram and a fitted curve of crack growth rate adhered to the Paris formula.FindingsNeither the maximum utilization factor nor the cumulative damage exceeds the threshold value of 1.0, the metro car body could meet the design life requirement of 30 years or 6.6 million km. However, three out of five fatigue key points were significantly influenced by the operational loads, which indicates that a single fatigue strength verification cannot achieve the infinite life design objective of the metro car body. For a projected design life of 30 years, the tolerance depth is 12.2 mm, which can underscore a relatively robust damage tolerance capability.Originality/valueThe influence of operational loads on fatigue life was presented by the discrepancy analysis between fatigue strength verification results and service life estimation results. The fracture properties of butt-welded joints were tested and used for the damage tolerance assessment. The damage tolerance life can be effectively related by a newly developed equation in this study. It can be a valuable tool to provide the theoretical guidance and technical support for the structural improvements and maintenance decisions of the metro car body.