Damage Accumulation Process Research Articles

Mechanical behavior and failure mechanism of 2D-SiCf/SiC composite under dynamic tensile loading through experimental and numerical investigation

The mechanical behavior of 2D-SiCf/SiC composite is investigated under both quasi-static (strain rate of 10-5 and 10-4s-1) and dynamic loading conditions (strain rate of 102s-1) through a combined experimental and numerical approach. The damage evolution process is monitored using digital image correlation, while failure mechanisms are analyzed through in-situ and post-test observations. Strain rate has a significant effect on tensile behavior of 2D-SiCf/SiC composite, including stress-strain behavior, damage accumulation process, fracture mode and fiber pull-out length. By integrating theoretical models with a detailed meso-scale finite element model, changes in constituent properties due to strain rate are quantified, and the evolution patterns of different damage modes under varying strain rates are explored. The study revealed that the strain rate effect is primarily driven by the enhancement of interfacial shear stress, matrix strength, and in-situ fiber strength as the strain rate increases.

Study on the extension mechanism of fissures in expansive soil based on fracture mechanics test method

Expansive soil, characterized by widespread fissures, is a special type of soil prone to localized fissure propagation, leading to failure and instability, often resulting in landslides. Numerous studies have applied fracture mechanics theory to analyze soil failure along fissures, but no standardized testing method has been established. This paper reviews existing soil fracture toughness testing methods, designs an integrated system combining digital image correlation(DIC) technique and electrical resistance testing, and employs the Cracked Chevron-Notched Brazilian Disc (CCNBD) method to assess the fracture toughness of expansive soil. The deformation and internal damage accumulation processes of the specimens were monitored. The KΙc and KΙΙc of expansive soil were tested at moisture contents of 15 %, 20 %, and 25 % using specimens with three different crack length ratios (a/R). The role of water was explored by injecting water into the fissures. The results showed that KΙc of expansive soil ranged from 10 to 36 kPa·m0.5, with a linear negative correlation to moisture content and a proportional relationship to tensile strength, having a proportionality coefficient of 0.331. The KΙΙc ranged from 20 to 70 kPa·m0.5,and it is greater than KΙc under the same conditions. Based on the load, internal damage, strain, and fissure area during the tests, the failure process of expansive soil along fissures was divided into four stages: initial deformation stage(I), quasi-elastic deformation stage(II), fissure extension stage(III), and failure stage(IV). Water injection into the fissures reduced the soil's fracture toughness, with a more significant reduction as a/R increased and the failure showed progressive behavior. The CCNBD method, combined with DIC technique and electrical resistance testing, effectively measures the fracture toughness of soil, aiding in understanding the failure mechanism along fissures and providing a basis for preventing and controlling landslides and other hazards in expansive soils.

Numerical study of the influence of the parameters of statistical distribution of the structural elements’ ultimate strength on deformable bodies’ fracture processes

This work is dedicated to the numerical study of the influence of the parameters of statistical distribution of the structural elements’ ultimate strength on fracture processes of deformable bodies with stress concentrators. The loading diagrams, the macro level behavior and the damaging process kinetics have been studied using various probability distribution laws and their standard deviations. The main types of the damage accumulation process have been identified. The approach basing on the analysis of the solutions of the boundary value problems within the elasticity theory has been proposed in order to predict the fracture process kinetics, the corresponding parameters have been introduced. Advantages, limitations and potential practical use of the proposed methodology have been discussed. It has been concluded that the statistical distribution of the structural elements’ strength properties should be taken into account in the numerical modeling of the fracture processes to ensure the reliability and safety of critical structures.

Seismic Response and Collapse Analysis of a Transmission Tower Structure: Assessing the Impact of the Damage Accumulation Effect

This paper delves into the impact of the damage accumulation effect, which leads to the degradation of material strength and stiffness, on the seismic resistance of transmission towers. Building upon the elastic–plastic finite element theory, a mixed hardening constitutive model is derived for circular steel tubes, standard elements in transmission towers, incorporating the damage accumulation effect. A user material subroutine, UMAT, is created within the LS–DYNA framework. The program’s validity and reliability are established through axial constant–amplitude loading tests on single steel tubes. The subroutine is employed to conduct the incremental dynamic analysis (IDA) of an individual transmission tower and to contrast it with the structure utilizing the Plastic Kinematic material model, assessing the discrepancies in tower top displacements and segment damage indices (SDIs) at both macroscopic and microscopic scales. The results shows that the Plastic Kinematic model inflates the seismic performance of the transmission tower. When considering the damage accumulation effect in structural failure, the damage index of the members increases, leading to a reduction in both the structural strength and stiffness. The dynamic response in the plastic phase becomes more pronounced, and the onset of structural failure is accelerated. Consequently, structural analysis under seismic conditions should account for the damage accumulation process. Through the delineation of member and segment damage, the extent of damage to transmission tower segments can be quantitatively assessed. Subsequently, the ultimate load–bearing capacity and the most vulnerable location of the transmission tower can be ascertained. Finally, this paper provides a detailed analysis of the transmission tower collapse process under seismic action and summarizes the mechanism of collapse for the structure.

Analysis of corrugation development on a Tianjin metro straight line focusing on wheel-rail contact mechanics

The development features of corrugation on the straight track metro line are studied to find the root cause of corrugation. Firstly, the measured corrugation characteristics on the line are investigated and a three-dimensional wheel-rail (WR) rolling contact finite element (FE) model is constructed. Then, the WR stick-slip (SS) characteristics, WR contact and rail wear are analyzed to understand the evolution process of corrugation from the micro transient point of view. Finally, combined with a system stability analysis, the development trend of corrugation is characterized from the macro perspective. The results show that the WR contact has a significant SS variation under the corrugation condition, which promotes the initial corrugation to develop further. For the fixed node in the contact area on the rail surface, the maximum stress and strain of the section where it is located will gradually transfer from the subsurface to the surface with the wheel running, so the damage prone position will also form first on the subsurface and gradually transfer to the surface. This shows from the micro viewpoint that the formation of wave crest/trough in the corrugation section is a bottom-up process of damage accumulation. The corresponding frequency of 648 Hz of the unstable vibration mode in the WR system is close to the passing frequency of 656 Hz of measured corrugation, demonstrating that the initial corrugation will tend to intensify with the wheel running.

Research on Macroscopic Mechanical Behavior of Recycled Aggregate Concrete Based on Mesoscale.

Recycled concrete is a heterogeneous composite material, and the composition and volume fraction of each phase affect its macroscopic properties. In this paper, ANSYS APDL was used to construct a two-dimensional numerical model of recycled aggregate concrete with different replacement rates of recycled aggregate (0%, 25%, 50%, 75% and 100%), and a uniaxial compression test was carried out to explore the relationship between recycled aggregate content and its macroscopic mechanical behavior. On this basis, the numerical simulation of different strain rates (0.1 s-1, 0.05 s-1, 0.01 s-1, 0.005 s-1 and 0.001 s-1) was carried out. It was found that with the increase in the recycled aggregate replacement rate, the peak stress decreases first and then increases, and the peak strain increases continuously. When the replacement rate of recycled aggregate exceeds 50%, the overall damage area of the material increases rapidly. The strain rate will change the path of the micro-crack initiation and expansion of recycled concrete, as well as the process of damage accumulation and evolution. As a result, the unit area and shape of recycled concrete are different at different strain rates, and the damage degree of each phase material is also different.

Study of the Surface-Layer Softening Effects in xLi2ZrO3–(1−x)Li4SiO4 Ceramics under Irradiation with He2+ Ions

The study investigates alterations in the mechanical and thermophysical properties of ceramics composed of xLi2ZrO3–(1−x)Li4SiO4 as radiation damage accumulates, mainly linked to helium agglomeration in the surface layer. This research is motivated by the potential to develop lithium-containing ceramics characterized by exceptional strength properties and a resistance to the accumulation of radiation damage and ensuing deformation distortions in the near-surface layer. The study of the radiation damage accumulation processes in the near-surface layer was conducted through intense irradiation of ceramics using He2+ ions at a temperature of 700 °C, simulating conditions closely resembling operation conditions. Following this, a correlation between the accumulation of structural modifications (value of atomic displacements) and variations in strength and thermophysical characteristics was established. During the research, it was observed that two-component ceramics exhibit significantly greater resistance to external influences and damage accumulation related to radiation exposure compared to their single-component counterparts. Furthermore, the composition that provides the highest resistance to softening in two-component ceramics is an equal ratio of the components of 0.5Li2ZrO3–0.5Li4SiO4 ceramics.

Enterohemorrhagic Escherichia coli effector EspF triggers oxidative DNA lesions in intestinal epithelial cells.

Attaching/effacing (A/E) pathogens induce DNA damage and colorectal cancer by injecting effector proteins into host cells via the type III secretion system (T3SS). EspF is one of the T3SS-dependent effector proteins exclusive to A/E pathogens, which include enterohemorrhagic Escherichia coli. The role of EspF in the induction of double-strand breaks (DSBs) and the phosphorylation of the repair protein SMC1 has been demonstrated previously. However, the process of damage accumulation and DSB formation has remained enigmatic, and the damage response is not well understood. Here, we first showed a compensatory increase in the mismatch repair proteins MutS homolog 2 (MSH2) and MSH6, as well as poly(ADP-ribose) polymerase 1, followed by a dramatic decrease, threatening cell survival in the presence of EspF. Flow cytometry revealed that EspF arrested the cell cycle at the G2/M phase to facilitate DNA repair. Subsequently, 8-oxoguanine (8-oxoG) lesions, a marker of oxidative damage, were assayed by ELISA and immunofluorescence, which revealed the accumulation of 8-oxoG from the cytosol to the nucleus. Furthermore, the status of single-stranded DNA (ssDNA) and DSBs was confirmed. We observed that EspF accelerated the course of DNA lesions, including 8-oxoG and unrepaired ssDNA, which were converted into DSBs; this was accompanied by the phosphorylation of replication protein A 32 in repair-defective cells. Collectively, these findings reveal that EspF triggers various types of oxidative DNA lesions with impairment of the DNA damage response and may result in genomic instability and cell death, offering novel insight into the tumorigenic potential of EspF.IMPORTANCEOxidative DNA lesions play causative roles in colitis-associated colon cancer. Accumulating evidence shows strong links between attaching/effacing (A/E) pathogens and colorectal cancer (CRC). EspF is one of many effector proteins exclusive to A/E pathogens with defined roles in the induction of oxidative stress, double-strand breaks (DSBs), and repair dysregulation. Here, we found that EspF promotes reactive oxygen species generation and 8-oxoguanine (8-oxoG) lesions when the repair system is activated, contributing to sustained cell survival. However, infected cells exposed to EspF presented 8-oxoG, which results in DSBs and ssDNA accumulation when the cell cycle is arrested at the G2/M phase and the repair system is defective or saturated by DNA lesions. In addition, we found that EspF could intensify the accumulation of nuclear DNA lesions through oxidative and replication stress. Overall, our work highlights the involvement of EspF in DNA lesions and DNA damage response, providing a novel avenue by which A/E pathogens may contribute to CRC.

A review of the interfacial transition zones in concrete: Identification, physical characteristics, and mechanical properties

Interfacial Transition Zones (ITZ) with high porosity are easier pathways for damage initiation and propagation. However, their mechanical performance has hardly been examined owing to the length scale of the microregions, as well as the heterogeneous and opaque constituent properties, which have been increasingly studied in recent years. This study presents a comprehensive review of the ITZ, determining strategies at the meso-micro level, quantitative characterization, and physical features. It focuses on the effects of various casting and material composition factors on the microstructural and mechanical properties of the ITZ, including porosity, thickness, volume, and elastic modulus. The correlations between the microstructures and the essential mechanical properties are discussed in detail. The weak bonding properties of the ITZ can be tailored by the material composition, which changes its internal microstructure, enhances the adhesion of the paste to aggregates, and fills micropores in cement. Several approaches can be employed to achieve this, such as adding minerals, increasing the curing age, and adjusting the water-cement ratio and sand fineness. The content of the weak ITZ can be reduced by optimizing the size distribution and volume fraction of the aggregates. Furthermore, modelling the gradient distribution of the ITZ thickness and elastic modulus is crucial in numerical simulations to enable an accurate investigation of the damage accumulation process in concrete. This study also identifies the challenges in the mechanical behavior of ITZ and serves as an engineering design guide for more advanced fracture-resistant concrete structures.

Mechanical behavior of fiber-glass plastic with hole pattern using digital image correlation and acoustic emission methods

In this paper, tensile tests of specimens with a pattern of holes made of fiber-glass plastic based on combined epoxy and phenol-formaldehyde resins are carried out in order to study the processes of damage accumulation and tension fracture. The Vic-3D video system is used to evaluate damage development and inhomogeneity of strain localization during loading. Continuous recording of acoustic emission signals is carried out during the tests, resulting in obtaining data on fracture mechanisms in the material. Ranges of peak frequencies are identified. Surface analysis of specimens was carried out using a microscope. A significant reduction in strength occurs due to the presence of a circular hole in the material, although additional holes do not exacerbate this effect. Fracture patterns of specimens with a hole pattern have been analyzed, and different "paths" of fracture have been observed. The comparison of strain fields obtained on the basis of application of three-dimensional digital optical system with the configuration of strain fields constructed as a result of numerical modeling by the finite element method has been carried out. It is found that the strain fields for different open hole patterns are quantitatively and qualitatively similar and identical.

Multi-Stage Hybrid Loading Fatigue Life Prediction Study

Abstract Fatigue is a damage accumulation process in which material properties are continuously deteriorated and degraded under cyclic loading. Damage accumulation analysis plays a key role in preventing the occurrence of fatigue failure, and the damage evolution mechanism is an important parameter of interest for fatigue behavior. The fatigue cumulative damage life prediction model is established by focusing on the damage evolution mechanism, and an improved Manson–Harford cumulative damage nonlinear model is developed to calculate fatigue damage life by considering the effect of load ratio of multi-stage loading on fatigue life. A fatigue life prediction method considering high-low cycles and multi-stage mixed loads is proposed. The fatigue life prediction accuracy of the model is verified by fatigue tests on structural samples. The accuracy of the fatigue life prediction error is the highest among similar models under the same test, the model proposed in this paper.

Damage mechanism and assessment of precast double-column bridge piers under blast impact

This paper aims to investigate the damage mechanism of precast double-column bridge piers under blast impact and propose a new damage evaluation method. The three-dimensional solid separation model of a pier column under explosion actions is established using ANSYS/LS-DYNA, and the accuracy of the numerical simulation method is verified by the existing experimental results. Subsequently, numerical experiments of the double-column bridge piers under explosions are carried out. The damage accumulation process and local failure mechanism are investigated with the analyses of the propagation of stress waves in concrete. In addition, the criteria containing residual bearing capacity and local damage are introduced in the damage assessment, aiming to evaluate the explosion damage degree of bridge piers comprehensively. The P-I (pressure-impulse) curves of precast double-column piers are established, based on the overpressure-impulse damage assessment method by Henrych’s empirical formula. The general evaluation process and method of double-column bridge piers under blast impacts are proposed and verified. The research results provide important insights and references for the anti-blast design of precast double-column piers and their bridge systems.

Influence of the process of damage accumulation on the asymptotic behavior of stress fields under creep conditions of a sample with a central crack

Influence of the process of damage accumulation on the asymptotic behavior of stress fields under creep conditions of a sample with a central crack

Effects of crystallographic orientation and lamellar configuration on fatigue crack propagation in single-colony structures of Ti–6Al–4V alloy: Alternating shear crack growth vs. damage accumulation crack propagation

In this study, the fatigue crack propagation mechanisms in lamellar colonies of Ti–6Al–4V alloy were examined using miniature compact-tension specimens with a single-colony structure at the crack tip. Fatigue tests were performed on colonies with different α-phase crystallographic orientations and lamellar configurations with respect to the notch plane and direction, followed by post-fatigue metallographic analysis. Crack propagation occurs by three main mechanisms: 1) alternating shear due to in-plane prismatic slip, 2) damage accumulation via dislocation–dislocation interaction due to out-of-plane slip, and 3) interlamellar decohesion due to damage accumulation via lamellar interphase boundary–dislocation interaction. The slope of da/dN vs. ΔK is higher for alternating shear crack growth than for damage accumulation crack propagation via dislocation–dislocation interaction. This is due to an incubation period before substantive crack extension in the latter case, which is dominated by degree of strain accommodation associated with the activated slip systems. When the lamellar interphase boundaries are nearly perpendicular to the loading axis, the crack growth rates drastically increase by interlamellar decohesion. This is attributed to the reduced incubation period due to slip incompatibility at the interphase boundary where numerous crack nuclei were formed during damage accumulation process.

A new fatigue cumulative damage model based on material parameters and stress interaction

In order to evaluate the fatigue damage accumulation process of materials under different stress levels and to predict the fatigue lives, a new fatigue accumulation damage model based on material parameters and stress interaction is proposed. The parameters of the material required for the action coefficient introduced by the proposed model are the slope of the S-N characteristic curve and the ultimate stress. In addition, the fatigue cumulative damage of the previous level and the ratio of adjacent stresses are also taken into consideration. Besides, we have conducted extensive experiments by utilizing the two-level stress experimental data of steel 300CVM, 16Mn steel, LY12CZ, and AL-2024-T42, the three-level stress experimental data of LY12CZ material, the four-level and five-level stress experimental data of Aluminum alloy material, respectively. Especially, we calculate and compare the fatigue prediction results of our proposed model with those of the 6 existing models, i.e., Manson-Halford model, YG model, Yue model, Haghgouei model, Subramanyan model and Hashin model. These materials used for verification, in addition to the fatigue test data of high cycle lives, also include the combination of high cycle and low cycle multi-level stress test data. Finally, we compare the cumulative fatigue life of each model via two-level to five-level stress tests, and calculate the difference between the fatigue damage prediction results and the test results to evaluate the advantage of the proposed model. The predicted results show that the model proposed in this paper is in great agreement with the real testing results. Besides, the prediction effect of the proposed model is significantly superior to that of the existing 6 models, especially when both the fatigue low-cycle and high-cycle mixed stresses are used, which validates the high robustness of the proposed model under various complex stress conditions.

Structural and functional regularities of the damage accumulation and failure in metals under dynamic loading and wear

The effect of damage caused by friction and wear on the accumulation of fatigue damage in the near-surface layers of the material used in technical systems operating under dynamic loading is studied. A comparative study of the samples of carbonized Cr – Mn – Si steel under ultrasonic loading in the range up to 109 cycles and the samples of steel 45 loaded at a permanent frequency of 100 Hz to simulate conditions of tribological tests for frictional fatigue revealed the same types of damage occurring in the characteristic frequency ranges of loading. To assess the effect of friction fatigue on damage accumulation and the probability of operational failures the authors have supposed that the processes of structural damage accumulation in cyclic and frictional fatigue are similar. The analysis of experimental data on the behavior of the friction coefficients and the magnitudes of broadening X-ray lines which characterize changes in the dislocation structure of the metallic structural materials (steels and titanium alloys) upon friction and the friction fatigue curves confirmed that the process of friction fatigue failure occurs via the mechanisms of low and high cycle fatigue that proves the validity of the proposed approach. The calculation results for the probability of the compressor failure are presented as an example. The calculations are based on the friction fatigue curves in a wide range of loading cycles obtained upon testing the crankshaft neck. The use of friction fatigue curves thus obtained provided assessment of the effects of combined action of the dynamic loading and friction, resulting in increased gaps and the dynamic loads (due to the wear of contacting parts) on the fatigue damage accumulation, durability and the reliability of the mechanical systems during operation.

A study of effects of different impact loads on the dynamic and elastoplastic behavior in reservoir rocks at the beginning of hydraulic fracturing

Successful hydraulic fracturing is very important in the development of hydrocarbon-bearing formations. The loading introduced by hydraulic fracturing causes deformation and failure, which are related to the damage accumulation and hydraulic fracture initiation process. This study employs a numerical model that considers the dynamic and elastoplastic behaviors in rocks under the influence of impact loads. The acceleration and wave propagation behaviors are quantified using the model. A time integration algorithm is used to ensure numerical accuracy and stability. The effects of loading rate, loading location, and heterogeneity are quantified. Results show that the elastoplastic and dynamic can effectively capture the wavy mechanical responses in the domain. Strain rate, acceleration, and plasticity can all exhibit oscillatory distribution patterns. Increasing the loading rate can magnify acceleration, strain rate, and the maximum plastic strain, while it reduces the range experiencing these induced changes. Changing the loading types and introducing the heterogeneity consideration both largely alter the mechanical response in the domain, and the waveforms of the mechanical parameters are significantly changed. Failure can occur earlier in layers with more elastic mechanical properties. Exerting 50 MPa loading in 0.01 ms can effectively introduce deformation and failures in the reservoir rock. Doubling the loading rate can effectively improve the ability of creating rock failures, which facilitates the following fracture initiation and propagation processes. This study can be a reference for the understanding of near-well and instantaneous rock mechanical behaviors at the beginning of fracturing.

Comparative analysis of fracture characteristics between rock and rock-like materials

In order to investigate the characteristics of rock and rock-like materials during the fracture process, notched semi-circular bending (SCB) experiments of 3 rocks and 2 rock-like materials were conducted in this paper. The process of the crack mouth opening was measured with a clip gauge. Acoustic emission was used to analyze the damage and failure mode of the specimens. Meanwhile, the fracture process zone (FPZ) was analyzed with the digital image correlation (DIC). Finally, the differences in the fracture process between rocks and rock-like materials were observed with a polarized microscope, and the formation mechanism of FPZ was discussed. The results indicate that the sequence from brittleness to plasticity is gypsum, marble, granite, concrete and fine sandstone. The crack opening velocity of gypsum, marble, and granite reaches 0.02–0.025 mm/s, far exceeding that of sandstone and concrete at 0.003 mm/s and 0.005 mm/s. The stronger the brittleness of geomaterials, the less significant their acoustic emission effect. Only a few acoustic emissions occur during the fracture process of gypsum with 8 hits. Its fracture occurs instantaneously rather than through a process of damage to fracture and the failure mode is tensile failure. Sandstone has the strongest plasticity, with a large count of acoustic emissions before and after fracture, with a hit number of 5062, which is 630 times of pure gypsum. The fracture is a process of damage accumulation with 94% of sandstone, 89% of concrete, 80% of granite, and 60% of marble showing a tensile and shear failure mode except gypsum. In addition, the stronger the brittleness of geomaterials, the smaller their FPZ size. The FPZ of gypsum is only about 3 mm, which can be considered as lacking, while other materials are about 6–11 mm. The formation of FPZ depends on whether an interlocking structure can be formed inside the material, which is related to the base material and crystalline or aggregate particle size.

Calculation of Life Characteristics for Structural Alloys under the Mutual Influence of Fatigue and Long-Term Strength

The processes of degradation of the initial strength properties of polycrystalline structural alloys are considered under mechanisms that combine low-cycle fatigue and long-term strength of the material. From the point of view of mechanics of damaged medium (MDM) and fracture mechanics (FM), a mathematical model that describes the processes of cyclic viscoplastic deformation and damage accumulation in structural alloys under multiaxial disproportionate modes of combined thermomechanical loading has been developed. The model consists of three interrelated components: relations that determine the cyclic viscoplastic behavior of the material by taking into account the dependence on the fracture process; evolutionary equations describing the kinetics of damage accumulation; criterion of the strength of the damaged material. The viscoplasticity model is based on the idea of the existence of plasticity and creep surfaces in stress space and the principle of gradient vectors of plastic and creep strain rates to the corresponding surface at the loading point. This form of the equations of state reflects the main effects of cyclic viscoplastic deformation of the material for arbitrary complex loading trajectories. The form of kinetic equations for damage accumulation is based on the introduction of a scalar damage parameter and on energy principles. It also takes into account the main effects of the formation, growth and merging of microdefects under arbitrary complex modes of combined thermomechanical loading. A joint form of the evolutionary equation for damage accumulation in the areas of low-cycle fatigue and long-term strength of the material is proposed. As a criterion for the strength of a damaged material, the condition for reaching a critical value is used. The material parameters and scalar functions included in the constitutive relations of the MDM mathematical model are obtained. The results of numerical simulation of the processes of deformation and damage accumulation in structural alloys under the mutual influence of low-cycle fatigue and long-term strength of the material are presented. The results of comparison of calculated and experimental data show that the proposed MDM model qualitatively and with the accuracy necessary for practical calculations quantitatively describes the durability of materials under the mutual influence of low-cycle fatigue and long-term strength of the material.

Micro-Mechanical Characterisation of Hydrogen Embrittlement and Fatigue Crack Growth Behaviours in Metastable Austenitic Stainless Steels with Microstructure Refinement

This article reviews the microstructural evolution in ultrafine-grained and nanotwinned austenitic stainless steels that have been subjected to hydrogen embrittlement (HE) and fatigue cracking. It provides guidelines for the development of high-strength austenitic steels without sacrificing HE and fatigue performance. The author focuses on the hydrogen-induced ductility loss and short fatigue crack growth associated with deformation-induced martensitic transformation, using micro-tension and micro-fatigue testing technologies. In type 304 metastable austenitic stainless steel, the microstructure produced by high-pressure torsion depends strongly on the processing temperature. Nanocrystalline austenite with enhanced strength and moderate ductility can be obtained at a processing temperature of ~423–573 K, whereas dual-phase microstructures comprising austenite and martensite are formed by processing at room temperature. Introducing ultrafine grains and nanotwin bundles mitigates the hydrogen-induced ductility loss in metastable austenitic steel by controlling the dynamic martensitic transformation. The microstructure refinement also contributes to enhanced resistance to short fatigue crack growth by changing the route of the damage accumulation process via phase transformation and detwinning.