Strain Rate Change Research Articles

Assessing the Adequacy of Earthquake Catalog Sampling for Long-Term Seismicity in Low-to-Moderate Seismic Regions: A Geodetic Perspective

Abstract Seismic hazard assessment in low-to-moderate seismicity regions can benefit from the knowledge of surface deformation rates to better constrain earthquake recurrence models. This, however, amounts to assuming that the known seismicity rate, generally observed over historical times (i.e., up to a few centuries in Europe), provides a representative sample of the underlying long-term activity. We here investigate how this limited sampling can affect the estimated seismic hazard and whether it can explain the disagreement between the seismic moment loading rate as seen by nowadays Global Navigation Satellite Systems (GNSS) measurements and the seismic moment release rate by past earthquakes, as is sometimes observed in regions with limited activity. We approach this issue by running simulations of earthquake time series over very long timescales that account for temporal clustering and the known magnitude–frequency distribution in such regions, and that those are constrained to a seismic moment rate balance between geodetic and seismicity estimates at very long timescales. We show that, in the example of southeastern Switzerland, taken here as a case study, this sampling issue can indeed explain this disagreement, although it is likely that other phenomena, including aseismic deformation and changes in strain rate due to erosional and/or glacial rebound, may also play a significant role in this mismatch.

Origins and optimization mechanisms of periodic microstructures in Al-Cu alloys fabricated by wire arc additive manufacturing combined with Interlayer Friction Stir Processing

Inter-layer Friction Stir Processing on Arc Additive Manufactured Components offers significant potential for performance enhancement, yet the homogenization of microstructures has become a challenge for industrial application. To address this, 2319 Al-Cu alloy components were fabricated through the Wire Arc Additive Manufacturing + Interlayer Friction Stir Processing (WAAM-IFSP)1 technique, and a systematic study was conducted on the effects of deformation degree, deformation temperature, and strain rate changes on the microstructural evolution, revealing three distinct periodic microstructures. An increase in deformation degree resulted in a uniform periodic microstructure, attributed to the more uniform internal deformation caused by the increased deformation degree. At a deformation degree of 24.1 %, higher strength and ductility were achieved, along with a notable bimodal grain structure (BGS). Further research indicated that this structure would distribute more widely within the matrix with increasing strain rate, aiding in further performance breakthroughs, ultimately reaching an ultimate tensile strength (UTS) of 404 MPa and an elongation (EL) of 32 %. However, imperfections in the process led to inhomogeneity in the structure. Focusing on the dynamic recrystallization (DRX) mechanisms during stirring can improve this phenomenon. The research revealed that the fine grains in the BGS were controlled by a synergy of dominant discontinuous dynamic recrystallization (DDRX) and auxiliary continuous dynamic recrystallization (CDRX) nucleation mechanisms. The findings are expected to provide a theoretical basis for the optimization of WAAM-IFSP processes and microstructural and performance regulation, which is crucial for enhancing the industrial application prospects of aluminum alloys.

Lateral impact performance of pitting corroded CFST columns for offshore applications

This study investigates the lateral impact performance of circular concrete-filled steel tube (CFST) columns with pitting corrosion. A comprehensive set of 15 CFST specimens was meticulously constructed, including 3 non-corroded specimens used as controls and 12 specimens subjected to varying pitting corrosion conditions. These conditions included different depths, numbers of corrosion pits, and pitting corrosion distributions. Additionally, an extensive Finite Element Analysis (FEA) was conducted to gain detailed insights into the instantaneous dynamic responses of CFST columns with pitting corrosion under lateral impact. The FEA included failure mechanism investigation, stress and strain analyses, bending moment responses, strain rate changes, and energy transformations. The experimental and FEA results reveal that pitting corrosion significantly affects the dynamic behavior of CFST columns, demonstrating reductions in impact force and flexural capacity due to pitting corrosion, and highlighting the influence of corrosion depth, number of pits, and distribution on column behavior. Finally, a simplified model incorporating the effects of pitting corrosion was proposed to estimate the dynamic flexural strength of pitting corroded CFST columns. The results provide valuable insights for designing and assessing the structural integrity of CFST members in marine environments.

Stress-controlled medium-amplitude oscillatory shear (MAOStress) of PVA–Borax

We report the first-ever complete measurement of MAOStress material functions, which reveal that stress can be more fundamental than strain or strain rate for understanding linearity limits as a function of Deborah number. The material used is a canonical viscoelastic liquid with a single dominant relaxation time: polyvinyl alcohol (PVA) polymer solution cross-linked with tetrahydroborate (Borax) solution. We outline experimental limit lines and their dependence on geometry and test conditions. These MAOStress measurements enable us to observe the frequency dependence of the weakly nonlinear deviation as a function of stress amplitude. The observed features of MAOStress material functions are distinctly simpler than MAOStrain, where the frequency dependence is much more dramatic. The strain-stiffening transient network model was used to derive a model-informed normalization of the nonlinear material functions that accounts for their scaling with linear material properties. Moreover, we compare the frequency dependence of the critical stress, strain, and strain-rate for the linearity limit, which are rigorously computed from the MAOStress and MAOStrain material functions. While critical strain and strain-rate change by orders of magnitude throughout the Deborah number range, critical stress changes by a factor of about 2, showing that stress is a more fundamental measure of nonlinearity strength. This work extends the experimental accessibility of the weakly nonlinear regime to stress-controlled instruments and deformations, which reveal material physics beyond linear viscoelasticity but at conditions that are accessible to theory and detailed simulation.

A failure model for bulk metallic glass based on strain rate-correlated softening mechanism

Due to the amorphous nature of the bulk metallic glasses (BMGs), catastrophic fractures occur once the nucleation and propagation of shear bands occur, which is quite different from crystal materials. So far, the underlying mechanism of BMG failure behavior and its strain rate effect are still controversial. In this work, the quasi-static and dynamic compression experiments of Vit-1 BMG were carried out in a wide range of strain rates from 0.001 s−1 to 5000 s−1. The results show that the variation tendency of failure stress with strain rate can be divided into three stages. The quasi-static failure stress is insensitive to the change of strain rate with only almost constant free volume softening effect inside the material during the failure process. When entering dynamic loading stage, the failure stress decreases significantly, which is caused by a combination of increasing thermal softening and free volume softening effects. When the strain rate increases to the third stage, that is, over 2000 s−1, the failure stress and the softening effects basically remain unchanged. The transformation of failure mechanism is well confirmed by the micromorphology of fracture surfaces. Based on the experimental results, a concise empirical failure model is established, in which the failure stress is decomposed into softening and non-softening parts. The verification experiments show that the model can effectively predict the compression failure stress of BMG under different strain rates.

Prediction of the flow behaviour of AISI 321 austenitic stainless steel during dynamic recovery using sine hyperbolic constitutive equation and artificial neural network

ABSTRACT In the present investigation, AISI 321 austenitic stainless steel was subjected to hot compression deformation at temperatures of 800, 850, and 900°C and strain rates in the range of 0.001-1 s-1. Results showed that in all the predefined conditions, the microstructure of the samples consisted of elongated austenite grains which indicates the occurrence of dynamic recovery. Furthermore, the hot flow curves obtained at this temperature range showed a trend similar to the dynamic recovery flow type behavior. In these curves, the flow stress increased with increasing applied strain and then tended to a constant value. The saturation stress at 800˚C increases from about 200 to 280 MPa with increasing strain rate from 0.001 to 1 s-1. For the same strain rate changes, the saturation stress increases from 150 to 240 MPa, and 90 to 200 MPa, at deformation temperature of 850 and 900˚C, respectively. The flow curves obtained from the hot compression tests were modelled using the sine hyperbolic constitutive equation and alternatively an artificial neural network. The results showed that the artificial neural network better predicts the flow behavior of AISI 321 austenitic stainless steel during dynamic recovery compared to the sine hyperbolic constitutive equation.

Mechanical properties of AlCoCrCuFeNi high-entropy alloys using molecular dynamics and machine learning

High-entropy alloys (HEAs) stand out from multi-component alloys due to their attractive microstructures and mechanical properties. In this investigation, molecular dynamics (MD) simulation and machine learning (ML) were used to ascertain the deformation mechanism of AlCoCrCuFeNi HEAs under the influence of temperature, strain rate, and grain sizes. First, the MD simulation shows that the yield stress decreases significantly as the strain and temperature increase. In other cases, changes in strain rate and grain size have less effect on mechanical properties than changes in strain and temperature. The alloys exhibited superplastic behavior under all test conditions. The deformity mechanism discloses that strain and temperature are the main sources of beginning strain, and the shear bands move along the uniaxial tensile axis inside the workpiece. Furthermore, the fast phase shift of inclusion under mild strain indicates the relative instability of the inclusion phase of hexagonal close-packed (HCP). Ultimately, the dislocation evolution mechanism shows that the dislocations are transported to free surfaces under increased strain when they nucleate around the grain boundary. Surprisingly, the ML prediction results also confirm the same characteristics as those confirmed from the MD simulation. Hence, the combination of MD and ML reinforces the confidence in the findings of mechanical characteristics of HEA. Consequently, this combination fills the gaps between MD and ML, which can significantly save time, human power, and cost to conduct real experiments for testing HEA deformation in practice.

Evaluation of changes in cardiac longitudinal strain rate in patients with systemic sclerosis undergoing iloprost treatment: an observational study.

Systemic Sclerosis (SSc) is characterized by widespread microangiopathy and fibrosis of skin and visceral organs. Left ventricle involvement is usually subclinical, characterized by systolic and/or diastolic dysfunction. The global longitudinal strain (GLS), a validated and reliable technique for the measurement of ventricular longitudinal deformation by means of echocardiography, may detect subclinical systolic dysfunction of SSc myocardium. The improvement of myocardial perfusion by means of intravenous Iloprost administration could ameliorate the contractility of SSc heart. Therefore, we aimed to evaluate GLS in a series of SSc patients prior and after Iloprost infusion. Fifteen consecutive SSc patients (age: 54 ± 11 years; 12 females) treated with Iloprost because of the presence/history of digital ulcers underwent echocardiography, including GLS technique. This evaluation was conducted immediately before Iloprost administration and at the end of the 6-h infusion session. Significant improvement in the mean GLS was observed after Iloprost administration (from -13.5 ± 2.5 to -15 ± 3.3; p= 0.011). The echocardiographic data obtained from the four-chamber view showed the best quality for GLS analysis and showed a highly significant improvement of the strain after Iloprost administration (from -13.4 ± 2.2 to -15.6 ± 3; p= 0.001). The degree of GLS improvement did not correlate with any SSc parameters. Iloprost administration improved GLS, suggesting that the increase of myocardial perfusion allowed, at least in part, a correction of left ventricular systolic dysfunction. Further studies are needed to confirm these findings, further exploring the mid/long-term effects of Iloprost on myocardial contraction.

Two-Level Constitutive Model of Metal with a Comprehensive Account of Temperature and Strain Rate Changes

Two-Level Constitutive Model of Metal with a Comprehensive Account of Temperature and Strain Rate Changes

Previously hidden landslide processes revealed using distributed acoustic sensing with nanostrain-rate sensitivity

Landslides sometimes creep for decades before undergoing runaway acceleration and catastrophic failure. Observing and monitoring the evolution of strain in time and space is crucial to understand landslide processes, including the transition from slow to fast movement. However, the limited spatial or temporal resolution of existing landslide monitoring instrumentation limits the study of these processes. We employ distributed acoustic sensing strain data below 1 Hertz frequency during a three-day rainfall at the Hollin Hill landslide and quantify strain-rate changes at meter and sub-minute scales. We observe near-surface strain onset at the head scarp, strain acceleration at a developing rupture zone, retrogression towards the scarp, and flow-lobe activity. These processes with displacements of less than 0.5 mm are undetected using other methods. However, the millimeter processes over three days agree with previously observed seasonal landslide patterns. Here, we show landslide processes occurring with nanostrain-rate sensitivity at spatiotemporal resolution previously not possible.

Effect of Strain Rate on Mechanical Deformation Behavior in CuZr Metallic Glass.

Tensile tests were performed on Cu64Zr36 metallic glass at strain rates of 107/s, 108/s, and 109/s via classical molecular dynamics simulations to explore the underlying mechanism by which strain rate affects deformation behavior. It was found that strain rate has a great impact on the deformation behavior of metallic glass. The higher the strain rate is, the larger the yield strength. We also found that the strain rate changes the atomic structure evolution during deformation, but that the difference in the atomic structure evolution induced by different strain rates is not significant. However, the mechanical response under deformation conditions is found to be significantly different with the change in strain rate. The average von Mises strain of a system in the case of 107/s is much larger than that of 109/s. In contrast, more atoms tend to participate in deformation with increasing strain rate, indicating that the strain localization degree is more significant in cases of lower strain rates. Therefore, increasing the strain rate reduces the degree of deformation heterogeneity, leading to an increase in yield strength. Further analysis shows that the structural features of atomic clusters faded out during deformation as the strain rate increased, benefiting more homogeneous deformation behavior. Our findings provide more useful insights into the deformation mechanisms of metallic glass.

Temperature-gradient and isothermal creep tests on 2024 aluminum alloy: A novel approach to creep failure evaluation aided by image processing

In high-temperature working conditions, the temperature difference between parts is common, and it is necessary to perform a temperature gradient test to predict creep behavior of alloy in real working conditions. In this study, a novel temperature gradient creep (TGC) test aided by an image processing method (IPM) was designed and performed on 2024-T3 aluminum alloy. The tests were performed under the conditions of isothermal tensile creep (ITC) and TGC in the temperature range of 285–315 °C under two stresses of 90 MPa and 125 MPa. Several experimental investigations were conducted to evaluate the creep failure of the specimens. The results showed that the temperature gradient during the TGC test leads to changes in strain, strain rate, stress exponent, microstructure and damage amount in the samples. The creep strain and strain rate of the TGC are greater than those of the ITC at 300 °C and 285 °C, and the rupture life is shorter. Finally, the Larson–Miller parameter is calculated, and the mathematical relationships between the strain rates of the TGCs and ITCs in 90 MPa and 125 MPa, which can be used to predict the creep strain rate under isothermal conditions, are proposed.

Dynamic responses of shear thickening fluid-filled lattice structures

Lattice structures that possess exceptional energy absorption capabilities show promise across various fields. However, their tendency to exhibit relatively low stiffness due to rotation or bending during impacts poses a challenge. Shear thickening fluid with the unique property of shear thickening effect can be an ideal filler to overcome the limitation of lattice structure. In this paper, composites that combined STF with new lattice structures were fabricated to investigate their dynamic response using experimental and numerical means and found that incorporating STF into these lattice structures not only preserved the inherent mechanical characteristics of the lattice structures but also led to substantial improvements on mechanical performance. The lattice structures displayed a noteworthy boost in stiffness, increasing significantly from 11.02 to 85.56 times. Additionally, there was an improvement in energy absorption, ranging from 2.78 to 5.51 times. These findings indicate that STF holds more promise in enhancing a structure's stiffness compared to its energy absorption capacity. Moreover, strain rate, weight fraction of STF, and cell size of the lattice structure were considered to further investigate their impact on the dynamic behaviour of STF-filled lattice structures. Our findings indicate that the increase in stiffness and energy absorption of the lattice structure following STF filling is correlated with an increase in strain rate and weight fraction but decreases when the cell size of the lattice structure is increased. The critical strain rate of STF-filled lattice structure was predicted, around 104 s−1, which indicates the onset of the shear-thickening effect in STF. Furthermore, it was observed that composites with higher weight fractions of STF were more responsive to changes in strain rate. Additionally, structures with initially lower mechanical properties experienced the most significant improvements after being filled with STF. These optimal outcomes provide valuable insights for the design of STF-filled lattice structures in practical applications.

Creep‐fatigue deformation characteristics and life prediction model of Inconel 718 superalloy under hybrid stress–strain‐controlled mode

AbstractIn this paper, the creep‐fatigue responses of the nickel‐based superalloy Inconel 718 have been investigated by conducting hybrid stress–strain‐controlled creep‐fatigue interaction (HCFI) loading experiments at 650°C with different dwell stresses and dwell periods. Deformation responses demonstrate that stress dwell leads to complex cyclic responses, such as an increase in softening rate and changes in inelastic strain rate. Then, a novel creep equivalent stress determination method is proposed based on stress relaxed characteristics. After modifying the continuum damage mechanics (CDM) model with this method, accurate prediction results of the creep‐fatigue cyclic life under strain‐controlled creep‐fatigue loading and HCFI loading can be obtained. Finally, the damage evolutions of Inconel 718 under HCFI loading are analyzed by CDM model. The results of damage evolution indicate that the trend of damage accumulation under different test conditions is consistent with the trend of inelastic strain in the material.

Study on Multi-Scale Tensile Strength and Tensile Strain of Calcium Silicate Hydrate Layered Nanocomposites Under External Physical Field

Calcium silicate hydrate (C-S-H) is the mainly strength source of cement-based materials, but there is little basic research. In this paper, molecular dynamics method is applied to analyze the multi-scale tensile strength and tensile strain of C-S-H layered materials under the condition of external physical fields (temperature and strain rate). The results show that the tensile strength and strain of C-S-H model decrease with temperature raises. The temperature (from 1 K to 600 K) has obvious influence on the tensile strain and strength of C-S-H layered materials. In addition, at (0.00025 ps-1-0.001 ps-1), the tensile strain and strength of C-S-H layered materials are less sensitive to strain rate. The whole model is closer to a 3-dimensional deformation. However, at (0.001 ps-1-0.005 ps-1), the dynamic load effect begins to increase, and the work done by the load per unit time increased. The tensile strain and strength of C-S-H layered materials indicates intensified by the change of strain rate. The energies are randomly distributed in the system, not concentrated in a certain area.

Numerical Investigation of Partially Premixed Flames Under Transcritical Conditions

Understanding the characteristics of partially premixed flames (PPFs) under transcritical conditions is of critical importance for the development of fuel-rich staged rocket engines. While substantial progress has been achieved for transcritical non-premixed flames (NPFs), comparatively little effort has been made to investigate transcritical PPFs. To this end, a series of transcritical counterflow gaseous hydrogen/liquid oxygen (GH2/LOX) PPFs is simulated to investigate the thermodynamic structure of PPF and to examine the effects of molecular diffusion modeling, strain rate, and the equivalence ratio at the fuel-rich side on PPFs in physical space and mixture fraction space, as well as reduced temperature/reduced pressure space. The comparisons between the NPF and PPF demonstrate that the PPF exhibits a bimodal structure in physical space: a premixed reaction zone at the fuel inlet side and a non-premixed reaction zone at the oxidizer side. In mixture fraction space, the C-shaped structure of PPF is observed owing to the differential diffusion of species. It is found that the choice of molecular diffusion model has a significant impact on PPF structure. The presence of a loop at subcritical pressures in a reduced temperature/reduced pressure space is caused by the differential diffusion of species and the formation of [Formula: see text] in the non-premixed reaction zone. Furthermore, the results indicate that the premixed reaction zones in the PPFs are very sensitive to the change in strain rate and/or equivalence ratio of the premixed mixture at the fuel inlet side. For a given equivalence ratio, increasing strain rate can suppress the differential diffusion effect and the C-shaped structure, while it has a negligible impact on the non-premixed reaction and hence on loop formation.

Elucidating changes in thermal creep strain rate of Cr-coated Zr-Nb alloy Accident Tolerant Fuel (ATF) cladding via experiment and mechanical analysis

Remarkable decrease in creep strain rate (86% decrease) was observed for Zr-1.1Nb alloy cladding coated with a thin Cr layer (16.8μm) compared to uncoated cladding in the present experiment at 380°C. The structural analysis with the in-house code and FEM analysis showed good agreement with the experimental results, demonstrating that the creep strain rate reduction was primarily occurred by mechanical cause. Cr coating layer induces extra compressive stress on the underlying cladding due to the strain compatibility, reducing the tensile stress level on the underlying cladding and thereby resulting in a decreased creep strain rate. This suggests the coating layer has non-negligible impact on the overall mechanical behavior of the underlying cladding despite of its significantly thin thickness. In addition, the XRD analysis found that the Cr coating layer has high compressive residual stress that also impedes the creep deformation of the underlying cladding. However, if the residual stress within the coating layer is limited or absent, the creep deformation will not be dramatically reduced. Inclusion of appreciable creep or plastic deformation of Cr coating led to the use of unrealistically high elastic modulus to match the experimental results. This result implies that creep or plastic deformation in the Cr coating layer is likely to be absent or negligible in the tested conditions. The magnitude of irradiation creep is markedly greater than that of thermal creep, and is less sensitive to the changes in stress which is induced by coating. Therefore, the extent of changes in creep strain rate in the reactor environment is anticipated to be less than that of an out-of-pile thermal creep experiments. It can be estimated that the creep strain rate will be decreased by 10–20% with Cr-coated cladding (Cr-thickness of 10μm - 20μm) at BOL.

Effects of balloon pulmonary valvuloplasty on longitudinal changes in right ventricular strain and strain rate in pediatric pulmonary stenosis.

Balloon Pulmonary Valvuloplasty (BPV) is a procedure for Pulmonary Stenosis (PS) treatment. In this study, right ventricle (RV) performance was determined through 2D-Speckle Tracking Echocardiography (2D-STE). The study involved 25 diagnosed children with PS undergoing BPV and 25 normal children. They were examined using 2D-STE and Linear Mixed Model (LMM) approach was used to determine changes in Pulmonary Valve Peak Gradient (PVPG), Tricuspid Annular Plane Systolic Excursion (TAPSE), strain and Strain Rate (SR) for RV, and Ejection Fraction for Left Ventricle (LVEF). Notable differences were found between two groups in TAPSE (P=0.001), global strain (P=0.001), apical septal strain (P=0.024), middle septal strain (P=0.001), basal septal strain (P=0.001), apical lateral SR (P=0.001), middle lateral SR (P=0.007), basal lateral SR (P=0.001), and apical septal SR (P=0.001). Post-BPV, there was an increase in LVEF (P=0.001) and TAPSE (P=0.001) but PVPG decreased (P=0.001). Following BPV, an increase was observed in apical lateral strain (P=0.004), middle septal strain (P=0.001), apical septal strain (P=0.003), middle septal strain (P=0.001), basal septal strain (P=0.048), apical septal SR (P=0.025), and middle septal SR (P=0.023). Gender was remarkably correlated with mean changes in basal lateral strain (P=0.019), middle septal strain (P=0.037), and middle septal SR (P=0.020). Age of PS children was related to mean change in basal septal strain (P=0.031) and basal septal SR (P=0.018). Strain and SR in RV improved post-BPV in children with PS. The gender and age of the children revealed remarkable effects on RV strain and SR changes after BPV.

Application value of ultrasound elastography for screening of early pregnancy cervical insufficiency: a retrospective case-control study.

This study aimed to investigate changes in the cervical strain rate (SR), cervical length (CL), and uterine artery blood flow parameters during early pregnancy in women with cervical insufficiency and evaluate the clinical efficacy of these markers for screening of cervical insufficiency in early pregnancy. This retrospective study in 60 pregnant women with cervical insufficiency and 100 normal pregnant women was conducted between September 2021 and January 2023 and measured ultrasound parameters of the cervix during early pregnancy. The cervical SR, CL, and uterine artery resistance index (RI) were measured in both groups at 11-14 weeks of gestation. Strain elastography represented by the SR was used to assess the hardness of the internal and external cervical openings. During early pregnancy, the SR at the internal and external cervical openings were significantly higher in the cervical insufficiency group than those in the normal pregnancy group (SR I: 0.19 ± 0.018% vs. 0.16 ± 0.014%; SR E: 0.26 ± 0.028% vs. 0.24 ± 0.025%; p < .001). The CL was significantly shorter in the cervical insufficiency group than that measured in the normal pregnancy group (34.3 ± 2.9 mm vs. 35.2 ± 1.99 mm; p = .036), while cervical blood perfusion was also poorer in the cervical insufficiency group than that in the normal pregnancy group (uterine artery RI: 0.76 ± 0.07 vs. 0.74 ± 0.05; p = .048). Receiver operating characteristic (ROC) curve analysis showed that the optimal critical values for diagnosing cervical insufficiency were 0.17% for SR I, 0.25% for SR E, 33.8 mm for CL, and 0.78 for uterine artery RI. Of these parameters, the ROC curve for SR I had the largest area under the curve [AUC = 0.89 (p < .001)], with the highest sensitivity (78%) and specificity (82%). Multivariate logistic regression analysis demonstrated that the SR at the internal cervical opening (OR 17.47, 95% confidence interval (CI) 5.08-60.08; p < .001) and CL (OR 5.05, 95% CI 1.66-15.32; p = .004) still showed significant differences between the two groups. Cervical elastography is an effective tool for screening early pregnancy cervical insufficiency. The SR at the internal cervical opening is a valuable indicator for screening cervical insufficiency and has superior clinical efficacy for screening for this condition compared to that of CL and the uterine artery blood flow index.

Exploring the influence of strain rate on BTRM tensile behaviour

Extensive research has been conducted on textile-reinforced mortars (TRM); however, a significant gap exists in understanding how strain rate influences mechanical performance. TRM composites reinforced with basalt textiles (BTRM) have become increasingly popular due to the remarkable sustainable profile of basalt fibres. However, there is limited knowledge regarding the tensile response of this composite under intermediate strain rates. The present study examined a BTRM composite consisting of a bi-directional basalt fibre textile and a commercially available mortar strengthened with short glass fibres. Coupon specimens with aluminium tabs were tested with a high-speed servohydraulic equipment at strain rates ranging from 0.5/s to 10/s. Strain and failure propagation were captured with a high-speed camera and analysed using the digital image correlation (DIC) technique. Tests were also performed under quasi-static conditions for comparison. The mechanical characteristics of the BTRM composite were assessed based on its tensile strength, ultimate strain, toughness, stress-strain behaviour, and failure mode. The findings demonstrated that the BTRM composite exhibited sensitivity to changes in strain rate. Increasing strain rates enhanced tensile strength, ultimate strain, and toughness. Furthermore, the specimens examined under dynamic conditions displayed distinct stress-strain characteristics compared to similar specimens subjected to quasi-static loadings.