High Strain Rate Effects Research Articles

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

Dynamic deformation behavior and mechanical properties of porous titanium: Coupling effect of high temperature and high strain rate

Porous titanium exhibits excellent mechanical properties and clarifying its dynamic deformation behavior with the rate-temperature effect can offer the significant insights for the structural design of materials. This article delves into the coupling effect of rate and temperature, as well as the local deformation mechanisms of porous titanium subjected to high-temperature and high-strain-rate conditions (−823 K and −8000/s, respectively). A dynamic balance formula for rate-temperature competition has been introduced for application in high-temperature and high-strain-rate conditions. The local relative deformation observed at the end face exceeds 300% than other regions, while the degree of end surface densification reaches 61.5%.

Effects of high temperature and strain rate on the impact-induced inter-laminar shear behavior of plain woven CF/PEEK thermoplastic composites

This paper aims to investigate the interlaminar shear properties and failure mechanisms of plain woven carbon fabric/polyetheretherketone (CF/PEEK) thermoplastic composites under high strain rate impact loads at different temperatures (25°C, 120°C, 295°C). A reliable hot air flow heating method with SHPB is creatively employed for short beam shear experiments. A multi-scale model was developed to predict the impact behavior of plain CF/PEEK composites. Both results show that the thermoplastic composites have strong strain rate and temperature dependence, and which are more sensitive to temperature effect. As the temperature increases, the thermoplastic composites are mainly affected by the softening effect of the matrix due to the glass transition temperature. The shear modulus and peak stress appear to decline at high temperatures, while the failure strain tends to increase. The damage mode changes from interlayer delamination cracking at the glassy state to shear fracture and fiber pullout at a highly elastic state. As the strain rate increases, the failure strain decreases, while the shear modulus and peak stress show the opposite trend. Fiber bundle breakage, debonding, matrix cracking, and significant interlayer delamination occur at high strain rates.

Surface characteristics evolution under the controllable impact cycles of an interrupted discrete waterjet

The interrupted discrete waterjet (DWJ) offers advantages in surface treatment due to its exceptional load characteristics and high controllability. However, the surface characteristics of materials under controllable DWJ parameters have not been fully elucidated. This study delves into the surface morphology, roughness parameters, microhardness, residual stress, and distribution of crystal characteristics in both the depth and radial directions under 2400–36,000 impact cycles of DWJ through peening experiments and material characterization. The findings indicate that the surface morphology is influenced by high-frequency roughness components with limited impact cycles, while low-frequency waviness components gradually take precedence with more impact cycles. As impact cycles increase, certain roughness parameters such as Sq, S5p, S5v, and S10z initially rise until 21,600 cycles, after which they fluctuate within a specific range. Furthermore, DWJ peening leads to an increase in maximum hardness with impact cycles, with the depth of peak value transitioning from the surface layer to the subsurface. The residual compressive stress initially increases and then decreases with impact cycles. Under the experimental conditions, the maximum hardness reaches 268.1HV0.3, a 49.95 % increase from the original state, and the peak residual compressive stress reaches 297.7 MPa with a 310.2 % increase. As impact cycles continue to rise, a balance between material removal and surface hardening is achieved, resulting in the stabilization of maximum hardness and compressive stress as erosion strength grows. Following DWJ peening, there is an increase in the percentage of low-angle grain boundaries, along with enhanced grain refinement, increased geometrically necessary dislocation (GND) density, and the emergence of new phases. As the impact cycles increase, the effects of DWJ peening on crystal grains become more pronounced. Additionally, it has been observed that the lateral jetting influence extends further horizontally than in the depth direction of the incoming jet. It is considered that cyclic hardening and high strain rate effects (1.2 × 104) play significant roles in material hardening and failure.

Effect of high strain rate on adiabatic shear susceptibility and microstructures in Al0.4CoCrFeNi high-entropy alloy

The effect of high strain rate on adiabatic shear susceptibility and microstructures in Al0.4CoCrFeNi high-entropy alloy (HEA) was examined using a split Hopkinson pressure bar (SHPB) and hat-shaped specimens. The results exhibit a clear strain-hardening effect at high strain rates within the experimental range in six specimen groups. The adiabatic shear band (ASB) with an approximately 1 μm wide was formed at 1.05 × 105 s−1 due to thermoplastic instability resulting from adiabatic temperature rise. The central region of the ASB consists of ultrafine and equiaxed recrystallized grains with a typical size of 100 nm. Comparison of metallographic observation and calculation shear voltage-time, the dynamic shear stress-time curves and the dissipation energy, it was found that the adiabatic shear susceptibility of Al0.4CoCrFeNi HEA increases with increased strain rate. The thermodynamic and kinetic calculations indicate that dynamic recrystallization can occur in the shear band based on the rotational dynamic recrystallization (RDR) mechanism.

Cryogenic mechanical behavior and FCC → HCP phase transformation mechanism in a Si-added CrCoNi medium-entropy alloy under quasi-static and dynamic tension

The CrCoNiSi0.3 MEA exhibits excellent cryogenic mechanical properties upon both quasi-static and dynamic tension. Under quasi-static tension at cryogenic temperature, the engineering yield and ultimate tensile strengths (UTS) reach 980 MPa and 1800 MPa, respectively, with notable ductility (62 %). The product of UTS and total elongation (TE) is 111.6 GPa %, surpassing most cryogenic high strength-ductility alloys. The significant mechanical strength enhancement is attributed to the denser deformation twins (DTs), multiple twinning, and extensive face-centered-cubic to hexagonal-close-packed (HCP) phase transitions, resulting in a high work hardening capacity. Upon dynamic tension at cryogenic temperature, the strength and strain hardening are further improved, which originates from the thickening DTs and HCP sequence and localized plastic deformation. The effects of temperature and strain rate on phase transition are studied. It is proposed that there is a competing relationship between high strain rate and increased stacking fault energy (SFE) due to temperature rise. The coupling effect of cryogenic temperature and high strain rate inhibits phase transition due to the deformation inhomogeneity in CrCoNiSi0.3 MEA. The findings make a valuable contribution to understand the influence of temperature and strain rate on the mechanism of FCC-to-HCP phase transition.

High strain rate effect and dynamic compressive behaviour of auxetic cementitious composites

Masonry walls are known for their limited impact resistance, even when retrofitted with CFRP (carbon fibre-reinforced polymer) and nanomaterials. This paper presents the findings of an experimental study using split Hopkinson pressure bar (SHPB) tests aimed at exploring the potential application of auxetics textile reinforced mortar (TRM) composites in impact protection. This study will provide the initial understanding of the composite as a structural reinforcement solution for masonry walls. Key findings reveal that the peak strength increases with rising strain rates, highlighting significant strain rate sensitivity in TRMs with auxetic (AX) and carbon fabric (CF) reinforcements. AX samples exhibit better energy absorption as compared to the reference plain mortar (PM) samples, particularly at higher strain rates, surpassing CF samples beyond 150 s−1. Moreover, the insertion of auxetic and carbon fabrics eliminates crack development and mitigates the severity of sample failure. The negative Poison ratio effect of auxetic fabrics significantly enhances the lateral confinement, ultimately improving the dynamic performance of AX samples compared to CF samples. These findings underscore the potential of auxetic materials in enhancing dynamic performance, particularly under high strain rates, with clear implications for engineering applications, including in masonry buildings.

Modeling and simulation of dynamic compression of Bulk Metallic Glasses at room and elevated temperatures using split Hopkinson pressure bar setup

This paper presents a modeling and simulation study of dynamic compression behavior of Bulk Metallic Glasses (BMGs) at room and elevated temperatures using the split Hopkinson pressure bar (SHPB) setup. The primary objective of this study is to develop and validate a constitutive model and simulation methodology capable of predicting the high strain rate response of BMGs at different temperatures. We propose a constitutive model for BMGs that accounts for the effects of high strain rates and elevated temperatures. We numerically implemented this model in ABAQUS/Explicit Finite Element Analysis software by writing a Vectorized User Material (VUMAT) subroutine. The methodology for modeling and simulation of dynamic compression of BMG specimens using the SHPB setup is developed. The present simulations are able to correctly predict the rate-independent response of Zr41.2Ti13.8Cu12.5Ni10Be22.5 (Vitreloy-1) BMG under dynamic compression at room and elevated temperatures. Furthermore, the present simulations are also able to correctly predict the negative strain rate sensitivity (SRS) of Zr52.5Cu17.9Ni14.6Al10Ti5 (Vitreloy-105) BMG at room temperature. Finally, the present simulations correctly predict that the failure stress of Zr64.13Cu15.75Ni10.12Al10 BMG decreases with increasing temperature and exhibits a minimal positive SRS. The present study is the first successful attempt to model the mechanical response of various BMGs under dynamic compression and at room and elevated temperatures. In particular, the experimentally observed negative SRS in some BMGs has been successfully simulated. The present work has important implications for the design of next generation spacecraft shields that are based on BMGs for mitigating the effects of hypervelocity impacts from debris in space.

Analytical modeling and analysis of the low-velocity penetration and non-penetration behaviors of fiber-reinforced composite cylindrical shells based on critical impact velocity criterion

An analytical model is developed to predict the impact characteristic parameters of composite cylindrical shells when low-velocity penetration and non-penetration damage are considered. The critical impact velocity criterion for judging the penetrating failure of such structures is also proposed. The impact contact force, displacement, and load-displacement curve of the structure subjected to oblique non-penetrating impact loading are solved using the improved Hertz contact theory, cumulative damage theory, stiffness degradation method, etc. Based on the formula derivation of critical impact velocity, the key impact parameters are solved, such as the residual velocity of the projectile and damage area of the structure with penetrating impact, which takes into account three energy absorption mechanisms, such as delamination, laminating crushing and linear momentum transfer. A series of non-penetrating and penetrating impact tests are conducted using a low-velocity drop hammer rig and a light gas gun. The prediction results of the proposed model are compared to both experimental and literature results. One can find out that the largest prediction errors of the peaks of impact contact force and displacement deformation are 12.3 and 9.2 %, respectively, and the counterparts of residual velocity and damage area are 12.0 and 6.2 %, respectively. Hence, the present model is trustworthy for predicting these impact parameters. Moreover, it is advised to adopt an appropriate stacking sequence, a high ratio of structural thickness to radius, a large oblique impact angle of the projectile, and a small mass ratio of the projectile to such a structure to enhance its impact resistance or reduce impact response. In addition, it is worth noting that the current model probably has a big prediction error of the high-velocity impact behaviors involving the material heating and soft effects caused by penetration damage since high strain rate and temperature effects are not considered.

Investigation of high strain rate effects on strain-hardening cementitious composites using Voronoi-cell lattice models

Strain-hardening cementitious composites (SHCC) have been reported in several studies to exhibit in several studies to exhibit high toughness even under extreme dynamic loads. To understand such dynamic behavior of SHCC, this study extends a previously developed rate-dependent lattice model by introducing a non-local formulation of the fiber-matrix interface behavior. The Voronoi-cell lattice model, representing the cementitious matrix, employs an explicit time integration scheme and a visco-plastic unit to account for the inertia effect and Stefan effect. Additionally, randomly-distributed short fibers were modeled using an analytical model of shear stress transfer at the fiber-matrix interface. The proposed numerical model successfully simulated the direct tensile behavior and multiple cracking patterns of SHCC, revealing distinct rate-dependent failure characteristics. Through a simple parameter fitting process, the model accurately predicted the dynamic increase factor (DIF) of strength and strain capacity of high-speed tensile experiments. Furthermore, the numerically evaluated rate dependency of the fiber-matrix interface exhibited identical trends to previous experimental studies. Finally, the influences of fluctuations in the applied strain rate during actual high-speed loading tests and the random dispersion of fibers were assessed.

The collapse evaluation method of steel moment-resisting frames based on dynamic increase factor

Considered the application of structural vibration characteristic parameters in the field of structural health monitoring and damage identification, the relationship between the structural dynamic increase factors (DIFs) and the collapse resistance of structure under the column removal scenario, is studied. Referring to previous researches, the load–displacement curve of structures under static collapse condition is simplified to be a multi-parameter broken line, which is used as the analysis and calculation model for the structural DIFs under the column removal scenario. Based on the model, the displacement-based DIF (DIFu) and the load-based DIF (DIFp) are derived with the help of energy balance method, and the development laws of DIFs are nalysed under different strength of catenary effect and ductility of structures. It is found that the value of DIFs in the catenary stage of structures is positively correlated with the ductility and strength of catenary effect of structures. A new structural collapse evaluation method is proposed based on the evaluation laws of DIFs. By dint of previous experiments the finite element model is established and the collapse evaluation method is verified. Finally, the different strain rates of steel are introduced in the FEM. It is found that the effect of medium and high strain rate of steel on the limit displacement of structures against column removal could be neglected, which further improves the evaluation method.

Effective prediction finite element model of pull-out capacity for cast-in-place anchor in high strain rate effects

Cast-in-place anchors are being increasingly used in many applications including building construction, bridge, and power plants. The anchorage to concrete systems are subjected to tensile, shear and combined loads from a variety of loading circumstances including static, dynamic, and shock loading. Despite extensive studies on these systems, reliable numerical models for predicting the behavior of these anchors are still limited. Therefore, this paper investigated the tensile behavior of cast-in-place anchorage to concrete systems, to propose an effective model for reproducing anchorage behavior using finite element (FE) methods. Experiments and code-based models for the anchorage system in tension were used to evaluate the numerical models for cast-in-place anchors in concrete, and the most suitable model, with advantages in accuracy and saving analysis time, was chosen. Finally, the FE model was used to study the tensile capacity and related dynamic increase factor for various strain rates, anchor diameters, and embedment depths.

High strain rate effects in masonry structures under waterborne debris impacts

Masonry buildings are vulnerable to extreme hydrodynamic events such as floods or tsunamis. Post-disaster surveys have shown that waterborne debris impacts can significantly damage masonry walls during these events. To simulate these actions, the current design or research practice is to compute the force–time diagram of the impact and then use it for dynamic analyses. Standing on the current knowledge, debris impacts are highly impulsive, but it is not clear if such loads are fast enough to activate the high strain rate effects in masonry, i.e. the strain rate dependency of material properties. The present study aims to answer this question, for the first time, following nonlinear Finite Element (FE) simulations. Simulations are conducted on a masonry wall, following a micro-modelling strategy, subjected to water flow and waterborne debris impact under different scenarios. It is found that the strain rates exceed the critical threshold after which strain rate effects are considerable. Such a finding, initially obtained using the minimum design demand for log-type debris imposed by ASCE/SEI 7-22, is further extended to a range of impact force–time diagrams different in impact duration and peak force (corresponding to different debris properties or flow velocity). It is also shown that the impact location (i.e. midspan or close to the boundary) affects the strain rate magnitude because of the changes in the impact stiffness and the activated failure mechanisms. Furthermore, it is found that the dynamic tensile post-elastic behaviour of the materials is the most influencing parameter in the structural response. These results open a new area in the field of assessment and design of masonry structures to waterborne debris and guide the development of future experiments, numerical simulations or design relations.

Numerical investigation on dynamic behavior and damage mechanisms of fiber metal laminates subjected to combined explosion and fragments loading

Fiber metal laminates (FMLs) are widely applied as protective structures in various high-tech industries owing to their excellent impact resistance. This paper presents an explicit finite element (FE) simulation to investigate the dynamic damage behavior of carbon fiber-reinforced aluminum laminates (CRALLs) under combined explosion and fragment loading. Johnson-Cook model is utilized to capture the damage response of aluminum material; 3D Hashin failure criteria are applied to predict the damage evolution of fiber composite material considering the high strain rate effect; cohesive elements are incorporated to simulate the inter-laminar delamination phenomena. The effectiveness of the proposed numerical model is verified through a comparison with available experimental data in ballistic impact conditions. In addition, a thorough analysis of the dynamic behavior and damage mechanism of FMLs is conducted, and the impact performance is extensively discussed in terms of the influences of explosion distance and explosion mass. This work serves as a valuable reference for future numerical studies on the explosive impact resistance of other FMLs structures.

Αn efficient numerical model for the simulation of debonding of adhesively bonded titanium/CFRP samples induced by repeated symmetric laser shocks

ABSTRACT Novel engine fan blades are made of 3D woven composite materials and incorporate a protective metallic layer at the leading edge. The end-of-life of such structures involves complicated disassembly and recycling processes. In this paper, laser-shock is being investigated as an environmentally friendly disassembly method. In this context, symmetric laser-shock experiments that have been conducted in a previous work using a time delay between the shots have been proven successful for debonding initiation and propagation as they manage to effectively focus the tensile stress field developed by the shock waves at the bondline. In this paper, a numerical model simulating the symmetric laser-shock disassembly of titanium/CFRP specimens has been developed using the LS-Dyna explicit FE code. The aim is to give a deeper insight into the physical mechanisms and to optimize the experimental process. To simulate the behavior of the titanium part, the Johnson-Cook material model in combination with Grüneisen equation of state has been employed, while for the composite part a progressive damage material model incorporating high-strain rate effects has been used. The bondline between the two parts has been modeled using cohesive zone elements. To obtain tensile and shear elastic and strength properties at high strain rates for the composite damage model, tension and punch shear Split-Hopkinson Bar tests have been conducted. The numerical results correlate well with back-face velocity profiles obtained from single sided laser shock experiments and with debonding patterns in the adhesive, observed in electron microscopy images, induced by symmetrical laser shock experiments. After the validation, the numerical model has been used successfully to simulate a larger disassembly process composed of 16 consecutive shots.

A modified K&C model for concrete subjected to coupled effect of high temperature and high strain rate

The K&C model is a commonly used constitutive model for concrete that simulates its dynamic response to blasts and impacts. However, this model is calibrated using data obtained at room temperature and is therefore not suitable for high-temperature conditions. To address this limitation, we propose a new constitutive model, named the KC-HT model, which is based on extensive modifications to the commercially available K&C model. The new model incorporates a failure surface that takes into account the temperature effect, which was established through triaxial compressive tests performed at high temperatures. The plastic hardening and softening behaviors of heated concrete are also considered by a new damage determination algorithm. The KC-HT model was integrated into the ABAQUS software using the VUMAT interface for simulation purposes, and its accuracy was confirmed through both single-element simulation and numerical SHPB tests. Finally, the KC-HT model was further validated by predicting the dynamic behavior of fire-damaged RC beams. The results reveal that the KC-HT model can replicate the dynamic behavior and crack morphology of concrete with different fire durations, while the K&C model is unable to take into account the temperature effect or the combined effect of high temperature and high strain rate.

Effect of strain rate and high temperature on quasi-static and dynamic compressive behavior of forged GH5188 superalloy

GH5188 Co-based superalloy is commonly employed in aero-engine eddy current and high-temperature components. Nonetheless, current research on its response behavior and mechanisms under dynamic and temperature loading remains scarce. Therefore, this study aims to investigate the dynamic compression and related deformation mechanism of GH5188 superalloy under the coupling effect of high temperature and strain rate. Quasi-static and dynamic compression tests were conducted on the forged GH5188 superalloy at both room temperature and 1000 °C. The results indicate that the material displays impressive yield strength and plasticity, while also showing a pronounced temperature sensitivity and strain rate hardening effect. Additionally, the dynamic stress-strain constitutive relationship of GH5188 is described by the modified J-C model. Regarding the dynamic deformation mechanism, GH5188 exhibited microbands, stacking faults, and nanotwins during high-strain rate compression. At 1000 °C, GH5188 underwent discontinuous dynamic recrystallization (DDRX) and continuous dynamic recrystallization (CDRX) at strain rates of 6000 s−1 and 10000 s−1, respectively. The synergistic effect of microbands and twinning enhanced the dynamic deformation ability and strengthening effect of the material. The transformation of microshear bands generated nanotwins. The twin boundaries are high-energy zones that can provide suitable recrystallization nucleation sites, induce dynamic recrystallization process, and thus obtain a fine and uniform equiaxed grain structure.

Modelling the behaviour of heavy and mass timber members subjected to blast loads

This paper presents a numerical study investigating the behaviour of glued laminated timber (glulam) beams and cross-laminated timber (CLT) panels subjected to shock-tube simulated blast loads. A 3D constitutive material model for wood, which accounts for the anisotropic nature of the material as well as high strain rate effects, was implemented into a finite element (FE) model via user subroutine. Utilizing the continuum damage approach for wood, a total of eight failure criteria were used to describe both ductile and brittle failure modes. A total of 23 full-scale experimental test results were used in the validation of the modelling approach. In general, the FE model was found to be capable of capturing the overall failure mode, damage propagation, as well as predicting the resistance curves with good accuracy.

Analytical and experimental investigations of rake face temperature considering temperature-dependent thermal properties

In metal cutting, rake face temperature is a critical factor affecting the quality of processed parts and tool wear. However, this temperature is difficult to estimate because of the high strain rate and barrier effect of chips. This paper presents an integrated analytical and experimental approach to predict rake face temperature, which proposes an improved analytical model considering temperature-dependent thermal properties. The considered temperature properties mainly include thermal conductivity (TC) and thermal diffusivity (TD) of the workpiece and cutting tool, which has rarely been considered in previous studies. With the measured cutting force and tool–chip contact length, the improved analytical model can predict the tool temperature based on an adaptive method to match the thermal properties and temperature at an arbitrary point. Moreover, a relatively new in situ measurement method for directly capturing the radiation of the rake face temperature using a two-colour pyrometer and slotted workpiece is presented. This new technique can eliminate the barrier effect of the chip without interrupting the cutting process. This experimental method is proved to be able to stably measure the rake face temperature with a deviation less than 3%, furthermore, the captured temperatures are much higher when compared with conventional methods under the comparable cutting conditions. The comparison of rake face temperature between the predicted and the measured results shows an average prediction error of 8.6% of the proposed method, proving its superiority over conventional models using constant thermal properties.

Dynamic compressive behaviour of basic magnesium sulfate cement–coral aggregate concrete (BMSC–CAC) after exposure to elevated temperatures: Experimental and analytical studies

This study investigates the effects of high temperature and strain rate on the dynamic compression behaviour of basic magnesium sulfate cement–coral aggregate concrete (BMSC–CAC). Specimens are exposed to temperatures ranging from 100 °C to 900 °C and then systematically tested using a split Hopkinson pressure bar (SHPB) apparatus. A three-dimensional mesoscale modelling approach is adopted in this study to account for the random shape and position of the aggregate. Results indicate that the dynamic impact damage is due to the coupled effect of high exposure temperature and high strain rate. At lower exposure temperatures, the dynamic compressive strength is similar to that at ambient temperature. However, at exposure temperatures of 500 °C and 700 ℃, the compressive strength is reduces to 50% and 30% of that at ambient temperature, respectively. Additionally, an increase in the exposure temperature increases the strain rate and continuously decreases the elastic modulus of concrete. A dynamic constitutive model is proposed considering the temperature and strain rate as influencing factor. This mesoscale modelling method is highly reliable and provides the best calculation parameters for simulating and predicting the dynamic compressive effect of BMSC–CAC after exposure to high temperatures.