High Strain Rate Research Articles

Effect of microstructure on dynamic response of ferrite matrixed steel at high strain rates

Dynamic response of steels at high strain rates are of great practical significance for understanding mechanical structures under extreme load conditions. To explore the relationship between structure and stress during dynamic deformation at high strain rates, steel specimens were prepared with varied microstructures of ferrite, ferrite and pearlite, and ferrite and spherical carbide. It is revealed that different microstructured steels exhibit drastically different characteristic of waves excited by the instantaneous impact of a servo-hydraulic tensile testing. It is also observed that a beat frequency response exists under dynamic deformation at certain high strain rates. It is therefore proposed that dynamic plastic deformation starts with stress fluctuation with a dislocation damped vibration model, and two successively excited waves are superimposed to form the beat frequency response.

Effect of the flow behavior and dynamic recrystallization of EH420 marine steel on the morphology evolution of martensite substructures

The hot deformation behavior of EH420 marine steel was investigated by isothermal compression tests in the temperature range of 850~1050°C and the strain rate range of 0.01~10s−1. A high-temperature constitutive model and a hot processing map were developed. The results indicated that the microstructure of EH420 marine steel after hot deformation was mainly bainite and lath martensite. The martensite blocks gradually coarsened with the increase in temperature within the range of 950~1050°C/0.01s-1, and the average width increased from about 0.7 μm to 2.3 μm. At high strain rates, martensite blocks became coarse and disordered due to flow instability. The flow stress curve showed a single peak when the strain rate was low. There were more dynamic recrystallization (DRX) structures, resulting in fine and ordered martensite blocks. Under the deformation conditions of 0.1~10s-1/1000°C, the proportion of high-angle grain boundaries (HAGBs) decreased from 53.5% to 40.7% as the strain rate increased. Meanwhile, the hot deformation mechanism shifted from discontinuous dynamic recrystallization (DDRX) to the combined effect of DDRX and dynamic recovery (DRV) and finally transformed into DRV. The flow stress derived from the constitutive model was consistent with the experimental results. The activation energy of EH420 marine steel was 3.16×105J/mol. The optimal hot processing parameters were 950~1050°C and 0.01~0.1s-1.

Dynamic splitting tensile properties of high-strength ultrahigh-toughness cementitious composites (HS-UHTCCs)

In this study, the splitting tests were conducted to examine the effect of strain rate on the splitting tensile performance of high-strength ultrahigh-toughness cementitious composites (HS-UHTCCs). Hydraulic machine and split Hopkinson pressure bar (SHPB) were used to investigate the tensile properties of HS-UHTCCs. The strain rates ranged from 10-6 to 10-3 s−1 for hydraulic machine experiments and from 5 to 15 s−1 for SHPB tests, respectively. The splitting tensile strength, tensile stress-strain curves, dynamic increase factor (DIF) and energy absorption ability of HS-UHTCCs were analyzed. The new DIF models proposed for HS-UHTCCs fit well with the experimental data. In addition, the failure modes of specimens and fibers were investigated. The splitting tensile strain was obtained from digital image correlation (DIC) tests. The results indicate that the strain rate has a significant effect on the splitting tensile strength and energy absorption ability of HS-UHTCCs. On the contrary, the average splitting tensile strain showed a decreasing trend with the increase of strain rate. Besides, the DIF model of HS-UHTCCs was proposed with experimental data. The failure modes of specimens changed at high strain rates, transitioning from remaining intact to completely splitting into half. Two failure patterns of polyethylene (PE) fibers included pull-out failure and rupture were observed, while steel fibers experienced pull-out failure.

Modification of the Johnson-Cook relationship for AZ31 magnesium alloy at high strain rates

Modification of the Johnson-Cook relationship for AZ31 magnesium alloy at high strain rates

A modified Johnson-Cook constitutive model of Inconel 690 weld overlay taking into account the strain rate softening effect

Precise material constitutive models are essential for finite element (FE) cutting simulation and analytical calculations of cutting mechanics. In this work, a split Hopkinson pressure bar (SHPB) equipment was employed to investigate the dynamic mechanical behavior of Inconel 690 weld overlay with a wide range of temperatures (20℃, 200℃, 400℃, 600℃, and 800℃) and strain rates (5000s-1, 7500s-1, 10,000s-1, and 12,500s-1). Based on the material flow characteristics at different loading conditions, a modified Johnson-Cook (JC) constitutive model was established, which takes into account the strain rate softening effect at high strain rates and the softening behavior induced by the competition between work hardening and dynamic recovery at large strains. Compared with the original JC constitutive model, the modified constitutive model can provide a closer correspondence between the predicted flow stresses and experimental data. The modified material constitutive model was introduced into FE simulation for orthogonal cutting of Inconel 690 weld overlay. The results indicate that the average prediction errors for the main cutting force and thrust force are 6.38% and 11.38%, respectively, validating the applicability and reliability of the modified JC constitutive model for cutting simulation applications. This study can provide a mechanical foundation for FE analysis in high-speed cutting of Inconel 690 weld overlay, which is conducive to optimizing cutting parameters, reducing machining costs, and enhancing production efficiency in practical industrial manufacturing.

Effect of Annealing Time on Grain Structure Evolution and Superplastic Response of Al-Mg 5xxx Alloys

The impact of annealing on the recrystallized grain structure and superplastic behavior of two Al-Mg 5xxx alloys used for high-speed blow forming (HSBF) was studied. The results revealed that both alloys demonstrated rapid static recrystallization after only a few minutes of annealing at 520 °C, forming fine and equiaxed grain structures. After four min of annealing, Alloy 2 (Al-4.0Mg-1.18Mn) exhibited a higher fraction of small grains (<10 µm) compared to Alloy 1 (Al-4.5Mg-0.74Mn). Moreover, Alloy 2 displayed enhanced resistance to grain coarsening with increasing annealing times, which was attributed to its higher amount of Al6(Mn,Fe) intermetallic particles and a higher number density of Mn dispersoids. Optimizing the annealing time can effectively develop a fine and stable grain structure in Al-Mg 5xxx alloys. During tensile deformation, Alloy 2 consistently showed higher ductility compared to Alloy 1 at low strain rates (170% vs. 138% at 0.001 s−1 and 163% vs. 134% at 0.01 s−1), whereas at a high strain rate of 1 s−1, both alloys displayed comparable tensile elongation. The high superplastic response of Alloy 2 at low strain rates renders it a superior superplastic alloy for HSBF applications.

Hot Deformation Behavior and Microstructure Evolution of the Maraging Stainless Steel

Hot deformation behavior of the maraging stainless steel is studied in temperature range from 900 to 1150 °C and strain rate from 0.1 to 10 s−1. When the deformation temperature is 900−950 °C, the abnormal stress increase is observed at the end of the flow curves. Transmission electron micrographs reveal that the Laves phase at the interface between prior austenitic (γ) and high‐temperature ferrite (δ) impedes hot deformation. The microstructure analysis shows that the dynamic recrystallization (DRX) mechanism of γ and δ is discontinuous DRX and continuous DRX, respectively. When the specimens are deformed at 950 °C, the extent of DRX at a strain rate of 5 s−1 is higher than at 0.1 s−1. This anomaly is due to adiabatic heating causing the actual deformation temperature at high strain rate () to be higher than at low , indicating that DRX is more influenced by temperature compared to . The influences of adiabatic heating and friction are corrected. Strain‐dependent constitutive equation is developed based on the revised flow curves, yielding an average absolute relative error of 4.69% and a correlation coefficient of 0.99; the prediction accuracy exceeds 90% when the relative error is within 10%.

Enhancing performance through friction welding of dissimilar aluminium 2014 and 7075 hybrid metal-matrix composite: insights into material characterization, crystallographic texture, and mechanical properties

Abstract Welding high-strength, age-hardenable aluminium alloys from the 2XXX and 7XXX series poses challenges when using fusion-based welding processes. Common issues such as hydrogen porosity, hot cracking, stress corrosion cracking, and solidification cracking can lead to a reduction in mechanical properties due to the loss of strengthening precipitates and alloying elements. Consequently, friction stir welding (FSW) has emerged as a promising solid-state welding technique for joining dissimilar aluminium alloys and composites, particularly in aerospace applications where a combination of strength, corrosion resistance, and other desirable properties is required. This study investigates the FSW of dissimilar aluminium alloys, specifically AA2014 and a hybrid metal-matrix composite of AA7075 reinforced with silicon carbide and graphite particles. The microstructural and mechanical properties of the welded joints were characterized, revealing an average grain size of 2.39 μm ± 1.2 in the stir zone (SZ). A high angle grain boundary volume fraction of 47.25% was observed in the SZ, compared to 2.01% in the AA7075 composite and 15.03% in the AA2014 base metal. The presence of shear textures and the distribution of cube, S, and H textures indicate a homogeneous mixing of the base materials and a high shear strain rate during welding. The hardness of the SZ increased by 13%, and the ultimate tensile strength, yield strength, and elongation of the joint were measured at 251 MPa, 183 MPa, and 6.44%, respectively. The flexural strength of the joints improved significantly, with the CW13 sample showing a 67% increase compared to CW1. The dissimilar joint CW13, welded at 12.5 mm min−1, achieved a maximum joint efficiency of 95%.

Effect of irradiation on the high strain rate indentation response of iron

Effect of irradiation on the high strain rate indentation response of iron

Impact of surface roughness on the formation of necking instabilities in additive manufactured porous metal plates subjected to dynamic plane strain stretching

This paper investigates the influence of surface roughness on multiple necking formation in additive manufactured porous ductile plates subjected to dynamic plane strain stretching. For this purpose, we have developed a computational model in ABAQUS/Explicit which includes surface texture and discrete voids measured from 3D-printed metallic specimens using optical profilometry and X-ray tomography analysis, respectively. The mechanical behavior of the material is described using an elastic–plastic constitutive model, with yielding defined by the isotropic von Mises criterion, an associated flow rule, and a power-law function for the yield stress evolution which depends on plastic strain, plastic strain rate, and temperature. The finite element calculations have been conducted across a broad range of strain rates, from 5000s−1 to 50000s−1, to explore the interactions among inertia, surface roughness, and porosity in determining the necking pattern that emerges in the plates at large strains. The finite element results show that surface roughness induces perturbations in the deformation field of the specimen, which lead to early necking localization, while the location and number of necks formed are primarily controlled by the porous microstructure and the loading rate. The results for the neck spacing have shown quantitative agreement with the analytical stability analysis predictions and the unit-cell finite element calculations reported by Rodríguez-Martínez et al. [1]. Moreover, integrating discrete voids into simulations that already account for surface roughness results in a minor reduction in necking strain: surface roughness and porosity demonstrate similar quantitative impacts on necking ductility, which is primarily influenced by inertia effects at the highest strain rates studied. To the best of the authors’ knowledge, this paper presents the first calculations that explore dynamic plastic localization in additive manufactured metals, incorporating actual surface roughness and explicit void representation derived from experimental measurements. This work marks progress in the analysis of 3D-printed structures under impact loading, aiming to understand and predict the mechanics influencing their energy absorption capacity at high strain rates.

Effect of high strain rates on the mechanical behavior and structure formation of the titanium alloy Ti–6Al–4V

Effect of high strain rates on the mechanical behavior and structure formation of the titanium alloy Ti–6Al–4V

Measurement of dynamic deformation during shock loading using a fiber-optic loop-sensor

Abstract Characterizing materials under shock loading has been of interest in fields such as protective material development, biomechanics to study the injury mechanics and high-speed aerodynamic structures. However, shock loading of material is a very short duration phenomenon and it is extremely challenging to develop sensors for dynamic measurements under such loading conditions. Optical fiber sensors that present the possibilities to allow high resolution measurement of force or displacement in such high strain rate loading conditions. This work studies the possibility of developing a single mode optical fiber sensor based on the principle of power losses from the curved section for dynamic measurements under shock loading conditions. The strain measurement results obtained from the optical sensors are validated with the controlled digital image correlation measurements are found to be in close correlation. The sensor was able to provide time sensitivity of better than 1 ms. The results show that the fiber sensor has the characteristics of high sensitivity and high precision, which can be used to measure fine vibration in real-time.

Thermodynamically consistent phase-field model for pressure-induced multiphase phase transformation of metals under intensive dynamic loading

Understanding the pressured-induced multiphase phase transformation (MPT) of metals at high strain rate is of great technical and scientific interest. Despite of several decades of studies, the pressured-induced MPT of metals at high strain rate is far from well understood because the deformation at high strain rate is so complex that present in situ diagnostic techniques or atomistic simulations cannot provide the details of the MPT at high strain rate. In the current work, a multiphase phase-field (MPF) model for the dynamic phase transformation (PT) of metals is developed, in which the volume fraction of each phase is chosen as the order parameter. The driving force of the MPT consists of the Gibbs free energy, the gradient energy and the penalizing energy. In particular, a smooth and normalized interpolation function is introduced to establish the Gibbs free energy at the multiphase junction. With the aid of this interpolation function, the explicit forms of the kinetics equation and constitutive relations of the MPT at the multiphase junction are also derived. It is demonstrated that the model satisfies all seven criteria of a consistent MPF model. Compared to previous models, the thermodynamic stability of this model is improved significantly. When applied to address the MPT of bismuth subjected to ramp-wave loading (RWL), the model can quantify the connection between the microstructural evolution of multiple phases and the experimentally measured multiwave structures.Moreover, new insights concerning the MPT-related thermodynamic paths of bismuth at elevated temperatures and the metastable phase during dynamic MPT are gained.

Heterogeneous dynamic restoration of Ti-15Mo alloy during hot compression

Near-β titanium alloys have shown low Young’s modulus and good strength, making them excellent implant candidates. However, their processing using thermomechanical routes in single phase β region results in heterogeneous microstructures due to high content alloying elements and consequent slow diffusion-controlled processes such as dynamic recovery. This study investigates the deformation behaviour of a Ti-15Mo alloy through hot compression experiments using a Gleeble ® 3800 device in the single β domain at strain rates from 0.01 s-1 to 10 s-1, reaching final strains of 0.50 and 0.85 followed by immediate water quench. The findings show that the material presents a low strain rate sensitivity. The flow curves show significant strain hardening before reaching a steady-state regime, particularly at high strain rates. The strain hardening exponent calculations support the effect of molybdenum on retarding softening mechanisms such as dynamic recovery. Electron backscatter diffraction (EBSD) measurements of deformed samples revealed that dynamic recovery is the primary restoration mechanism, with continuous and geometric dynamic recrystallisation evidence. Due to the slow restoration process, we observe the subgrain formation for different deformation parameters. Therefore, we introduced an EBSD-based method to quantify dynamic recovery and subgrain size. We concluded that for a given deformation, the areas of dynamically recovered and recrystallised regions decrease with increasing strain rate and decreasing temperature, exhibiting negligible variation at higher strain rates.

Adiabatic Shear Localization in Metallic Materials: Review.

In advanced engineering applications, there has been an increasing demand for the service performance of materials under high-strain-rate conditions where a key phenomenon of adiabatic shear instability is inevitably involved. The presence of adiabatic shear instability is typically associated with large shear strains, high strain rates, and elevated temperatures. Significant plastic deformation that concentrates within a adiabatic shear band (ASB) often results in catastrophic failure, and it is necessary to avoid the occurrence of such a phenomenon in most areas. However, in certain areas, such as high-speed machining and self-sharpening projectile penetration, this phenomenon can be exploited. The thermal softening effect and microstructural softening effect are widely recognized as the foundational theories for the formation of ASB. Thus, elucidating various complex deformation mechanisms under thermomechanical coupling along with changes in temperatures in the shear instability process has become a focal point of research. This review highlights these two important aspects and examines the development of relevant theories and experimental results, identifying key challenges faced in this field of study. Furthermore, advancements in modern experimental characterization and computational technologies, which lead to a deeper understanding of the adiabatic shear instability phenomenon, have also been summarized.

The influence of V microalloying on the hot deformation behavior and microstructure evolution of high-manganese steel for LNG storage tanks.

Herein, the high-temperature hot deformation and dynamic recrystallization (DRX) behavior of high-manganese steel were investigated through the measurement of true stress-strain curves, the establishment of constitutive equations, the construction of recrystallization and hot processing maps, and the characterization of microstructure evolution. Furthermore, the influence of V on the DRX behavior of high-manganese steel during the hot deformation process, particularly for LNG storage tanks, was systematically evaluated. The results indicate that both the critical stress (σc) and peak stress (σp) of the tested steels increase as the deformation temperature decreases and the strain rate increases. Additionally, a higher V content leads to an increase in σc and σp, thereby suppressing the occurrence of DRX. Compared to 0.1V steel, 0.2V steel precipitates a greater quantity of carbides at the grain boundaries (GBs), which effectively stabilizes the GBs and inhibits the growth of DRX grains. In contrast, 0.1V steel achieves DRX over a wider range of Z parameters (at lower temperatures and higher strain rates). The activation energies for hot deformation (Q) of the two tested steels are 479.100 kJ/mol and 438.274 kJ/mol, respectively. The hot processing maps indicate that an increase in V content reduces the hot workability of high-manganese steel. The optimal temperature and strain rate for hot processing of 0.1V steel are 1035–1095°C and 0.01–0.0451 s⁻1, respectively. For 0.2V steel, the optimal hot processing parameters are a temperature of 1065–1100°C and a strain rate of 0.01–0.07 s⁻1.

Microstructure-sensitive crystal plasticity and phase-field modeling of deformation and fracture in polycrystalline ice

The formation of crevasses in Greenland and Antarctica is primarily driven by the brittle failure of ice at low strain rates. Understanding this phenomenon requires exploring the effect of microstructural heterogeneity and anisotropic elastoplastic deformation on the fracture behavior of ice. Here, we have developed a microstructure-sensitive coupled crystal plasticity and phase-field model. This model allows us to study the plastic deformation, damage initiation and propagation under various strain rates in hexagonal open-packed polycrystalline ice, the prevailing phase on Earth. By employing a Bayesian optimization method, we derived the material parameters for the micromechanical model based on experimental results. The modeling results reveal that the activation of basal dislocations results in a brittle to ductile transition in ice at a low strain rate of 10-7s-1 under tension. At higher strain rates, the intrinsic plastic anisotropy of ice leads to heterogeneous deformation among grains and stress concentration near grain boundaries, triggering crack initiation and exacerbating the brittleness of ice. Under compression, cracks usually do not propagate throughout the specimen due to a significant decrease in stress around the crack tip upon propagation. Moreover, we found that the formation of the shear-induced basal texture at the bottom of ice layers and along glacier valley sides intensifies the brittleness of ice. This study provides insights into the micromechanical deformation and fracture mechanisms of ice, elucidating the intricate process of crevasse development in polar ice sheets.

Anisotropic stress corrosion cracking susceptibility of Mg-8Gd-3Y-0.5Zr alloy

This study investigates the stress corrosion cracking (SCC) behavior of a Mg-8Gd-3Y-0.5Zr alloy in a 3.5 wt.% NaCl solution using slow strain rate tensile (SSRT) testing. The results reveal that SCC susceptibility increases as the strain rate decreases, with hydrogen embrittlement (HE) becoming more dominant at lower strain rates, leading to brittle fracture. Anodic dissolution (AD) plays a more significant role at higher strain rates, resulting in mixed fracture modes. Additionally, the mechanical properties and SCC resistance are strongly influenced by the sample orientation. TD-oriented samples show higher SCC susceptibility than RD-oriented ones due to the alignment of Gd- and Y-rich precipitates and grain boundaries, which act as initiation sites for SCC. These precipitates form micro-galvanic couples with the Mg matrix, accelerating localized corrosion and HE. The findings provide insights into the SCC mechanisms of VW83 alloy and highlight the importance of optimizing microstructure and processing conditions to improve its corrosion resistance.

Investigation on the thermal deformation mechanisms and constitutive model of Ti-55511 titanium alloy

This study presents a comprehensive analysis of the hot deformation behavior of the Ti-55511 alloy over a temperature range of 700 °C–950 °C and strain rates from 0.001 s⁻1 to 1 s⁻1, utilizing isothermal compression testing alongside electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM). The investigation focuses on the influence of various hot deformation parameters on the microstructural evolution of distinct phase regions within the alloy. At higher strain rates (0.1 s⁻1 to 1 s⁻1), the primary softening mechanisms for β grains in the α+β two-phase region are identified as continuous dynamic recrystallization (CDRX) and dynamic recovery (DRV), while in the β single-phase region, discontinuous dynamic recrystallization (DDRX) and DRV predominate. Conversely, at lower strain rates (0.001 s⁻1 to 0.01 s⁻1), the softening of β grains in the two-phase region is primarily governed by DRV, whereas in the single-phase region, DDRX and CDRX are the dominant mechanisms. Additionally, based on stress-strain data corrected for friction and temperature effects, an elastoplastic constitutive model is developed, incorporating strain rate and temperature to predict peak stress in the two-phase regions of the Ti-55511 alloy. This examination of the thermal deformation behavior and microstructural evolution of the Ti-55511 alloy provides significant theoretical and practical insights for optimizing the manufacturing processes of aviation die forging, tailoring microstructures, and enhancing hot working techniques.

Dynamic response and damage mechanisms of 2D plain weave hybrid composites under the out-of-plane punch shear loading

A modified theoretical method for the punch shear test is derived by considering the influence of stress wave reflections caused by cross section discontinuities in the incident and transmitted bars. The dynamic punch shear behavior of 2D plain weave carbon/aramid hybrid composites was researched. The failure strength and strain are sensitive to strain rate. The stress-strain curves were obtained by the modified method. Significant shear deformation was observed under a single loading. An effective punch shear mesoscopic simulation model that accounts for the strain rate effect of the component materials was developed using the multi-scale analysis method. The model reveals the damage characteristics in the component materials. Damage modes are affected by hybridization and strain rates. The high elongation at the fracture of aramid fibers at high strain rates plays a crucial role in absorbing impact energy.