Rise Of Strain Rate Research Articles

The thermal deformation behavior and processing map of TC9 titanium alloy

This investigation delves into the thermal deformation behavior of TC9 titanium alloy. Compression tests at isothermal conditions were performed on a Gleeble thermal simulator under conditions spanning 700–1200 °C and strain rates of 0.001–1 s−1. The true stress-true strain curves indicated that stress increases with rising strain rate and decreasing temperatures. The softening mechanisms in the biphasic and monophasic regions were discussed. By correcting errors caused by friction, the strain-compensated Arrhenius-type constitutive equation, which accurately describes the flow behavior of TC9 titanium alloy, has been established. A processing map at a strain of 0.7 was constructed based on the power dissipation factor, revealing an unstable region at 700–800 °C/0.01–1 s−1 and 800–900 °C/0.1–1 s−1, where microcrack defects were observed, suggesting that processing should be avoided in this region. Efficiency values as high as 60–70 % indicate superplasticity deformation, with corresponding m values within this efficiency range of approximately 0.4–0.5, reaching the strain rate sensitivity index range of superplasticity titanium alloys. Tensile tests conducted at 900 °C and a deformation rate of 0.001 s−1 showed elongation exceeding 100 %. The sample compressed at 900 °C and 0.001 s−1 exhibits small grain size, uniform orientation, the lowest dislocation density, and a uniform two-phase mixture. These microstructural features indicate the material's good machinability.

Research on mechanical properties of HTPB propellants

Abstract Slat propellants with different sizes and shapes are designed to investigate the strength criteria of HTPB propellants. According to the calculation and simulation results, with the increase of multiple, the designed size slat specimens can achieve equivalent biaxial tensile stress ratios of 1:2, 1:2.5, 1:3, 1:3.5, and 1:4 under uniaxial tensile conditions. The biaxial mechanical properties of the slab with a stress ratio of 1:2 were tested at low temperatures (25°C, −30°C, −50°C, and 0.4 s−1, 4.0 s−1, 14.29 s−1, 42.86 s−1). It was found that as the temperature and the strain rate rise, an increase is observed in the maximum tensile strength and the initial modulus, a decrease is observed in the maximum elongation of the propellant, and the strength envelope is constructed according to the typical mechanical parameters: the strength envelope of HTPB propellant increases as the temperature decreases. The research findings are expected to provide statistical support for the analysis of the structural integrity of HTPB propellants under low-temperature ignition.

Mechanical Behaviour of Photopolymer Cell-Size Graded Triply Periodic Minimal Surface Structures at Different Deformation Rates.

This study investigates how varying cell size affects the mechanical behaviour of photopolymer Triply Periodic Minimal Surfaces (TPMS) under different deformation rates. Diamond, Gyroid, and Primitive TPMS structures with spatially graded cell sizes were tested. Quasi-static experiments measured boundary forces, representing material behaviour, inertia, and deformation mechanisms. Separate studies explored the base material's behaviour and its response to strain rate, revealing a strength increase with rising strain rate. Ten compression tests identified a critical strain rate of 0.7 s-1 for "Grey Pro" material, indicating a shift in failure susceptibility. X-ray tomography, camera recording, and image correlation techniques observed cell connectivity and non-uniform deformation in TPMS structures. Regions exceeding the critical rate fractured earlier. In Primitive structures, stiffness differences caused collapse after densification of smaller cells at lower rates. The study found increasing collapse initiation stress, plateau stress, densification strain, and specific energy absorption with higher deformation rates below the critical rate for all TPMS structures. However, cell-size graded Primitive structures showed a significant reduction in plateau and specific energy absorption at a 500 mm/min rate.

Behavior of geometrically-similar Basalt FRP bars-reinforced concrete beams under dynamic torsional loads

A numerical model utilizing 3D mesoscale simulation methods was developed to investigate the influence of strain rate on the torsional performance of geometrically similar Basalt Fiber Reinforced Polymer bars-reinforced concrete (BFRP-RC) beams, as well as the corresponding size effects. The model incorporates concrete heterogeneity, material strain rate effects, and the dynamic bond-slip relationship between BFRP bars and concrete. The torsional performance of BFRP-RC beams with different structural sizes and stirrup ratios was analyzed under different strain rates. The study yielded the following findings: (1) The damage degree of BFRP-RC beams increases with the rising strain rate. (2) Increasing strain rate and stirrup ratio enhances the beams’ torsional strength and ductility while attenuating the size effect, albeit not eliminating it. (3) The impact of increasing strain rate on beam strength, ductility, and size effect outweighs that of increasing stirrup ratio. Finally, based on the Bažant size effect law (SEL) combined with the simulation results, a new size effect law was proposed that can quantitatively consider the effect of strain rate and stirrup ratio on the torsional strength of BFRP-RC beams.

Plastic deformation mechanisms and constitutive modeling of WE43 magnesium alloy at various strain rates and temperatures

In this study, we investigated the mechanical behavior and deformation mechanisms of as-cast and as-rolled WE43 at various strain rates and temperatures. Compression tests were carried out at ambient temperature under 900/s, 1400/s, and 2000/s, and at temperatures of 100 °C, 200 °C, 250 °C, and 300 °C under 1400/s, respectively. The results showed that, with the rise of strain rate, the deformation mechanism of as-cast and as-rolled WE43 both changed from twinning dominant combined with slipping to slipping dominant. As the temperature increased, the deformation mechanism of WE43 changed from twinning to slipping, controlled by non-basal slips at various strain rates and temperatures. As for as-rolled WE43, it was observed that intense dynamic recrystallization and adiabatic shear bands (ASBs) occurred under high strain rate and high temperature conditions. Moreover, this study employed the Johnson-Cook (JC) model to formulate the plastic deformation model of the WE43 alloy under conditions of elevated temperatures and high strain rates. And a dynamic mechanical analyzer (DMA) was successfully employed to refine the accuracy of elastic modulus.

Effects of fiber characteristics and specimen sizes on static and dynamic split-tensile failures of BFLAC: 3D mesoscopic simulations

In this study, a three-dimensional mesoscopic numerical model considering concrete heterogeneity and explicit modelling of basalt fibers was established to simulate the static and dynamic split-tensile failures of basalt fiber-reinforced lightweight aggregate concrete (BFLAC), with a special focus on the influences of structure sizes (D = 100, 200, 300 and 400 mm), basalt fiber contents (Vf = 0.1 %, 0.2 % and 0.3 %), fiber lengths (Lf = 6, 12, 18, 24 mm) and loading strain rates (ε̇ = 10-5/s ∼ 100/s) on split-tensile failure patterns, deformation characteristic and failure strengths. Simulation results indicate that as the fiber length increases, split-tensile strength of BFLAC enhances first and then remains unchanged. As the fiber content increases, both static and dynamic split-tensile strengths enhance, showing a fiber reinforcement effect which increases with the rising strain rate rise and reaches a threshold when the strain rate exceeds 1/s. Under static and low strain rates, the size effect on split-tensile strength of BFLAC is reduced by the addition of basalt fiber content; while there is a reverse size effect under high strain rates and it is strengthened with the increasing fiber content. Besides, the strain rate effect of BFLAC is stronger with the increasing basalt fiber content. A unified TDIF formula of BFLAC considering the influence of basalt fiber content was proposed, which can provide a valuable reference for the dynamic performance simulations and calculations.

Investigations of Dynamic Mechanical Performance of Rubber Concrete under Freeze-Thaw Cycle Damage

In order to study the effect of the freeze-thaw cycle on the integrity and dynamic mechanical performance of rubber concrete, the wave speed of rubber concrete specimens with 10% rubber volume was measured by a nonmetallic ultrasonic detector. The impact tests were also performed on rubber concrete specimens with different numbers of freeze-thaw cycles (0, 25, 50, 75, 100, and 125) at different impact air pressures (0.3, 0.4, 0.5, and 0.6 MPa) using a 74 mm diameter split Hopkinson pressure bar (SHPB) device, peak stress, ultimate strain dynamic intensity enhancement factor (DIF), and energy absorption effect. The results show that with the increase of freeze-thaw cycles, the wave speed decreases, and the freeze-thaw action will damage the rubber concrete and reduce the longitudinal wave velocity. Under the same freeze-thaw cycles, with the rise of strain rate, the peak stress, limit strain, DIF, and absorbed energy increase, and there is an obvious strain rate effect; under the pressure of 0.6 MPa, the peak stress of 25, 50, 75, 100, and 125 freeze-thaw cycles decreases by 25.1%, 37.1%, 46%, 52.5%, and 54.8%. With the increase of the freeze-thaw cycles, the peak stress of the specimen decreases, and the decrease gradually decreases. After the number of cycles exceeds 100, the stress decrease of the specimen is no longer obvious, the limit strain increases, and the absorbed energy decreases. The freeze-thaw environment significantly reduces the strength and integrity of rubber concrete specimens.

Mechanical properties and microstructure evolution during dynamic compression and cutting of nickel-based superalloys

Superalloy GH4169 has been widely used on account of its excellent property. However, the microstructure characteristics of the machined surface will be changed significantly because of mechanical-thermal coupling effect after the cutting process, which affects the fatigue performance of key components. To clearly understand the microstructure development of surface layer during machining process, the mechanical behavior and microstructure evolution of GH4169 under high strain rate and high temperature conditions are studied in detail by dynamic compression tests. The peak stress can be improved by rising strain rate and decreasing temperature. Cutting experiments show that the depth of low angle grain boundaries distribution and plastic deformation in the machined surface layer are improved by rising cutting parameters. The degree of twin boundaries deviation from the ideal misorientation increases by improving cutting parameters. In addition, the geometrically necessary dislocation density increases first and then decreases by increasing distance from the machined surface. Furthermore, the cutting simulation model based on dynamic compression tests are established.

Effects of structure and strain rate on deformation mechanism of twin lamellar Al0.3CoCrFeNi alloys

Lamellar twined materials display simultaneous ultrahigh strength and high ductility, which is attributed to the interaction between twin boundaries and dislocation. However, deformation at the atomic level is rarely seen in experiments. To study the deformation properties and mechanical behavior of the lamellar twined Al0.3CoCrFeNi high-entropy alloys (HEA) sample, we applied the uniaxial tension by employing molecular dynamics (MD) simulations. The impact of various twin inclination angles, twin boundary spacing (TBS), and strain rates are investigated. The mechanical softening as the increasing TBS from 4a to 12a was observed, which corresponds to Hall – Petch relationship. The yield strength of the medium inclination angle (450, 600) records the minimum value with all various TBS due to the elastic energy being easier released. The strain-hardening phenomenon appears at these angles. The sample with an inclination angle perpendicular to the tension loading axis (900) displays the highest stress value. The shrinking migration twin has been observed in 00, 150, and 300 twin inclination angles. The migration and disappearance of initial TBs lead to grains being reoriented into the same orientation at 450 and 600. With twin orientations of 750 and 900, the TB is no longer as crisp and straight as the initial TB under the tension process. An extensive dislocation process occurs at higher strain values, and their interaction with TB leads to establishing the shear band. After that, twin boundaries within the shear band are almost destroyed. Besides, the results also indicate that the flow stress, ultimate strength, and Young's modulus rise with the rising strain rate and decreasing temperature.

Microstructural evolution and dynamic compressive properties of engineered cementitious composites at elevated temperatures

This paper presents a comprehensive study on the microstructural evolution and quasi-static and dynamic compressive properties of engineered cementitious composites (ECC) at elevated temperatures (20, 105, 250, 400, 600 and 800 °C). Split Hopkinson pressure bar (SHPB) was adopted to investigate the compressive behaviour of ECC at various strain rates after exposure to elevated temperatures, while the corresponding microstructural evolution was characterised using scanning electron microscopy (SEM), digital electron microscope and mercury intrusion porosimetry (MIP) along with fractal analysis. Results indicate that ECC exhibited strain rate effect and high temperature sensitivity simultaneously. The residual dynamic compressive strength of ECC increased by 33.0–50.4% with the rising strain rate from 79.8 to 127.1 s−1. It reached the maximum value at 105 °C but reduced to 14.3−25.8% at 800 °C compared to that at 20 °C. The change in dynamic increase factor of ECC for various temperatures and strain rates can be well predicted using the developed equation. The thermal decomposition of PVA fibres was the main detrimental affecting the dynamic performance of ECC at sub-high temperatures (below 400 °C), whereas the negative effects caused by the formation of pores and microcracks in the matrix dominated at higher temperatures (400−800 °C). Microscopic damage induced by elevated temperatures aggravated the deterioration degree under dynamic compressive load, whilst the larger the difference in the macro/micro pore structural fractal dimension of 2.50/2.67, the greater the temperature softening effect on impact resistance of ECC.

Effect of strain rates on the mechanical response of whole muscle bundle.

Muscle injuries frequently happen during sports activities and exercise, which could have serious consequences if not diagnosed and treated promptly. This research aims to investigate the quasi-static and dynamic responses of over 30 fresh frog semitendinosus muscles utilizing Split Hopkinson Pressure Bars (SHPB) and a material testing system under strain rates between 0.001 ~ 200s-1. To accommodate the special shape of muscle-tendon-bone samples, PLA clampers were produced by the 3D printer to properly hold and prevent slipping during the testing process. The mechanical characteristics of the whole muscle bundle, including Young's modulus and stress-strain curve, are illustrated at various strain rates. The findings showed that the muscle properties were sensitive to strain rate when under passive deformation. Both maximum stress and Young's modulus increased with the rise of strain rate, and modulus at 200s-1 can be as high as 10 times compared with quasi-static conditions.

Effect of strain rate on fractography texture descriptor of AA6063/(Si3N4)x/(Cu(NO3)2)y (x=12%, y = 2–6%)composite after multiple ECAP passes: second order statistical texture analysis conjunction with regression analysis

The tensile strength of the ECAP processed composite of AA6063/(Si3N4)x/(Cu(NO3)2)y (x=12%, y=2-6%) at various strain rates from 0.0001 to 1s-1 with an increment of 10 was examined in relation to the seven-fracture image texture descriptor through void features such as void size and distribution. In order to measure the matrices of voids on the fracture surface created through the coalescence of void results to enhance the material hardening as strain rate increases, the second order statistical texture analysis has been used. With respect to the rising strain rate, it was observed that the composite fracture image feature parameter correlation, homogeneity improved by 6 %, and 20.74% for AA6063/12%Si3N4/6%Cu(NO3)2 after I passes as compared to AA6063/12% Si3N4 after III pass. The contrast was reduced by around 58.643% when reinforcement went from a single reinforcement of 12% Si3N4 with I Pass to a composite of two reinforcements (Si3N4, Cu(NO3)2) that had 6% Cu(NO3)2 with I Pass. After three passes on AA6063/12%Si3N4/2%Cu(NO3)2, the maximum entropy was seen due to the material's increased plastic deformation, which led to an uneven particle distribution. As strain rate and copper nitrate percentage grew from 0 to 6 percent, the tensile strength of the composite improved by 34.69%. To assess the importance of fracture image features in relation to tensile strength with respect to strain rate, a regression model was developed. In order to get information about the fracture studies from fractography, the contrast with varying strain rate was nevertheless the aspect, which had the greatest influence.

Dynamic response and adiabatic shear behavior of β-type Ti–Mo alloys with different deformation modes

This study examined the dynamic compressive properties and adiabatic shear behavior of β-type Ti–10Mo, Ti–15Mo, and Ti–22.5Mo alloys whose deformation modes are stress-induced α''-martensitic transformation combined with {332}<113> twinning, {332}<113> twinning, and dislocation slip under quasi-static loading, respectively. Based on the characterization of deformation microstructures, the deformation modes did not undergo significant change regardless of quasi-static and dynamic conditions. Their yield strength increased remarkably when the strain rate rose from 10−3 s−1 to 103 s−1, thus exhibiting the strain rate strengthening effect. The impact absorbed energy showed an increasing trend with a rise in strain rate, and the highest value (319.2 J/cm3) was observed in the Ti–15Mo alloy at a strain rate of 3956 s−1. The {332}<113> twinning deformation led to a high capacity for strain hardening, which delayed the formation of adiabatic shear bands, comprising the ultra-fine β-matrix and nano-scale ω-phase. Moreover, the deformed twins provided a tortuous and bifurcated path to enhance the propagation resistance of adiabatic shear bands, thereby further consuming the impact energy.

The influence of SAP particle size and extra water on the dynamic mechanical behavior of SAP-modified cement-based composites

Superabsorbent polymers (SAP)-modified cement-based composites (abbreviated as composites) have excellent frost resistance, internal curing efficiency, self-sealing and self-healing capacity. However, the effects of SAP particle size and extra water on the dynamic mechanical behavior of composites are still unclear. In this study, the total porosity and macropore (>100 μm) porosity of composites were studied with a mercury intrusion porosimetry test and an image analysis. The influence of SAP particle size and extra water on the quasi-static and dynamic mechanical properties of composites was analyzed. The fracture behavior of composites was investigated based on the fractal dimension and crack morphology. The results reveal that adding extra water can respectively raise the total porosity and macropore porosity by 33 %–39 % and 36 %–50 %, thereby declining the compressive strength and elastic modulus of composites under quasi-static and dynamic compression. The rise of strain rate from 63 s−1 to 102 s−1 elevates the dynamic compressive strength, elastic modulus, and fracture degree of composites by 39 %–44 %, 4.9 %–6.0 %, and 5.2 %–7.4 %, respectively. Raising particle size of SAP and adding extra water can raise the dynamic increase factor of compressive strength and elastic modulus. Which originates from the change of crack path, the increase of fracture degree, and the delayed response of strain induced by the rise of total and macropore porosity.

Experimental Study of Dynamic Mechanical Properties of Water-Saturated Coal Samples under Three-Dimensional Coupled Static–Dynamic Loadings

It is very important to study the influence of water content on the mechanical properties of coal rock to prevent rock burst and roadway instability under dynamic disturbance. In this study, the split Hopkinson pressure bar (SHPB) test system was applied to conduct three-dimensional dynamic and static impact tests on natural and water-saturated coal samples at different strain rates to determine the dynamic mechanical properties of a series of water-bearing coal samples. Based on the new data, we discuss the strength, deformation, crushing energy dissipation, and fractal characteristics of natural and saturated coal rocks. We specifically focus on the different effects of hydraulic pressure on crack propagation under static and dynamic loads. Our results document a well-defined linear relationship between the peak stress and the strain rate of coal in the natural state and the water-saturated state. Once the impact rate reaches a certain value, a double peak phenomenon is observed, and the curve shows a certain leap. The critical impact velocity of the curve leap is ca. 9.485~10.025 m/s. At the same strain rate, the average peak stress in the water-saturated state is ca. 2.684% higher than that in the natural state. The secant modulus of the two states generally increases with the rise in strain rate, but the scatter of the results is large. The average secant modulus of the water-saturated coal sample increases by 2.309% compared with the natural state. The energy consumption density and absorbed energy of saturated and natural coal samples rise with the increase in strain rate, and both show a well-defined power–function relationship. However, under the same condition, the absorbed energy and absorbed energy density of water-saturated coal samples are higher than that of natural coal samples. The fractal dimension of water-saturated coal rises with the increase in strain rate and energy consumption density, showing a strong linear and quadratic relationship, respectively. Under dynamic loading, the cohesive force, jointly generated by free water and the Stefan effect, hinder the expansion of coal and rock fractures, thus improving the compressive strength of coal and rock. The study provides a reliable theoretical basis for preventing rock burst and providing roadway support.

Hysteresis loss of ultra-large off-the-road tire rubber compounds based on operating conditions at mine sites

The objective of this study is to investigate the hysteresis loss of ultra-large off-the-road (OTR) tire rubber compounds based on typical operating conditions at mine sites. Cyclic tensile tests were conducted on tread and sidewall compounds at six strain levels ranging from 10% to 100%, eight strain rates from 10% to 500% s−1 and 14 rubber temperatures from −30°C to 100°C. The test results showed that a large strain level (e.g. 100%) increased the hysteresis loss of tire rubber compounds considerably. Hysteresis loss of tire rubber compounds increased with a rise of strain rates, and the increasing rates became greater at large strain levels (e.g. 100%). Moreover, a rise of rubber temperatures caused a decrease in hysteresis loss; however, the decrease became less significant when the rubber temperatures were above 10°C. Compared with tread compounds, sidewall compounds showed greater hysteresis loss values and more rapid increases in hysteresis loss with the rising strain rate.

Hot Deformation Behavior and Constitutive Analysis of As-Extruded Mg–6Zn–5Ca–3Ce Alloy Fabricated by Rapid Solidification

The plasticity of Mg–6Zn–5Ca–3Ce alloy fabricated by rapid solidification (RS) at room temperature is poor due to its hexagonal-close-packed (HCP) structure. Therefore, hot deformation of RS Mg–6Zn–5Ca–3Ce alloy at elevated temperature would be a major benefit for manufacturing products with complex shapes. In the present study, hot deformation behavior of as-extruded Mg–6Zn–5Ca–3Ce alloy fabricated by RS was investigated by an isothermal compression test at a temperature (T) of 573–673 K and strain rate (ε˙) of 0.0001–0.01 s−1. Results indicated that the flow stress increases along with the declining temperature and the rising strain rate. The flow stress behavior was then depicted by the hyperbolic sine constitutive equation where the value of activation energy (Q) was calculated to be 186.3 kJ/mol. This issue is mainly attributed to the existence of fine grain and numerous second phases, such as Mg2Ca and Mg–Zn–Ce phase (T’ phase), acting as barriers to restrict dislocation motion effectively. Furthermore, strain compensation was introduced to incorporate the effect of plastic strain on material constants (α,Q,n,lnA) and the predicted flow stresses under various conditions were roughly consistent with the experimental results. Moreover, the processing maps based on the Murty criterion were constructed and visualized to find out the optimal deformation conditions during hot working. The preferential hot deformation windows were identified as follows: T = 590–640 K, ε˙ = 0.0001–0.0003 s−1 and T = 650–670 K, ε˙ = 0.0003–0.004 s−1 for the studied material.

Dynamic Recrystallization Behavior in a Hot Compressed Symmetrical Bulb Flat Steel

The process of dynamic recrystallization of bulb flat steel was simulated by the hot compression tests at a deformation temperature ranging of 950 to 1200 °C and strain rate ranging of 0.02 to 5 s−1, which is also the rolling speed and temperature range of the large-sized bulb flat steel. The results show that the PAGs increases gradually with the increase in deformation temperature. The PAGs are 16.7 μm in the temperature of 950 °C and up to 27.1 μm in the temperature of 1100 °C. The average austenite grain size was sharply decreased from 31.2 to 24.4 μm with the rise of strain rate from 0.2 to 2 s−1; the degree of decrease gets slow and becomes 21.9 μm at the strain rate of 5 s−1. Moreover, the constitutive equation of activation energy and grain sizes of dynamic recrystallization in the deformation process were established, and the dynamic recrystallization was elaborated in the deformation temperature of 950 to 1200 °C and strain rate ranging of 0.02 to 5 s−1. The dynamic recrystallization in the rolling process can be well reflected by the established models.

Locating the optimal microstructural state against dynamic perforation by evaluating the strain-rate dependences of strength and hardness

Intense research efforts have been made to understand the variation of strength with strain rate, while the mechanisms governing the strain-rate dependence of hardness have been rarely studied. In this work, we conducted a comprehensive investigation on strength, hardness and failure mechanism of AISI 4340 steels with 4 different microstructural states in a wide range of loading rate. We found strain-rate hardening behavior in all 4 steels, while the degree of hardening, characterized by the normalized dynamic strength (NDS) or the normalized dynamic hardness (NDH), depends on not only materials but also loading modes. With the increase of material strength, the NDS significantly increases but the NDH decreases slightly. The inconsistency between the variations of NDS and NDH is because the hardness is governed by not only yield strength but strain-hardening ability. Although the yield strength increases as rising strain rate, the strain-hardening ability reduces obviously, particularly for high-strength materials due to shear softening under dynamic loading conditions, which also causes a transition from homogeneous deformation to shear fracture. The variations of NDS and NDH could reflect the trends for resisting not only the ductile perforation (strength limited) but also the shear plugging failure (toughness limited), allowing to propose a criterion for locating the optimal strength-toughness combination against dynamic perforation, which was further verified by the ballistic penetration testing results. Moreover, similar behaviors of NDS and NDH of various other alloys were also found, which may suggest the extensive applicability of the current approach.

Compressive Properties and Energy Absorption Characteristics of Extruded Mg-Al-Ca-Mn Alloy at Various High Strain Rates.

This paper is focused on the mechanical properties and the energy absorption characteristics of the extruded Mg-Al-Ca-Mn alloy in different compression directions under high strain rate compression. Compressive characterization of the alloy was conducted from the high strain rate (HSR) test by using a Split Hopkinson Pressure Bar (SHPB). Results show that the investigated alloy exhibits a strong strain rate sensitivity. With the rise of strain rate, the compressive strength is increased significantly, and the deformation ability also improves. When compressed along the extrusion direction, as the strain rate increases, the total absorbed energy E, the crush force efficiency (CFE), and the specific energy absorption SEA of Mg-Al-Ca-Mn alloy are all greatly improved as compared with those obtained along other compression directions.