Heterogeneous Stress Field Research Articles

Impact of initial stress field heterogeneity in dynamic soil–structure interaction

This article covers the impact of soil initial stress field heterogeneity (ISFH) in wave-passage analysis and in prescribed structural acceleration in the context of dynamic soil–structure interaction (DSSI) analysis. ISFH is directly related to the natural behavior of soil where a significant increase in net effective confinement, as is the case in the foundation soil under a building, tends to increase the soil’s modulus and strain. This creates a heterogeneous stress field in the vicinity of the foundation elements, which results in a modification of the dynamic behavior of the soil–structure system. A simple method for considering the impact of ISFH on the value of the soil’s modulus and strain was developed using the direct DSSI approach. The method was used to analyze numerical artifacts and its impact on the surface acceleration values of a nonlinear two-dimensional (2D) numerical soil deposit under transient loading. This analysis was followed by a sample application for a three-story, three-bay concrete moment-resisting frame structure erected on a deep soil deposit. Floor acceleration and relative displacement were used for comparison. The soil deposit was modeled using the typical geotechnical properties of fine-grained, post-glacial soil samples obtained in Eastern Canada from in situ geotechnical borehole drilling, geophysical surveys, and laboratory testing. Ground motion was based on eastern calibrated seismic signals. The results of the soil deposit analysis show that ISFH had a significant impact on surface acceleration values. The effect was found to be period-dependent and to have a direct impact on prescribed acceleration values at the base of structure. Thus, failure to take the effects of ISFH into consideration can lead to errors in calculating prescribed structural accelerations (i.e. over- or underestimation).

Multi-scale fracture probability analysis of tungsten monoblocks under fusion conditions

Plasma facing components inside future nuclear fusion reactors are subjected to a high heat load and intense irradiation conditions. Using advanced computational material models, several problems can be solved that reflect tungsten monoblocks under fusion relevant loading scenarios. This allows for the identification of the conditions under which material failure is probable. The material model and parameters are identified such that the mechanical behaviour is in accordance with the homogenized behaviour of a previously developed crystal plasticity model on the microscopic scale. The heterogeneous stress field that follows is analysed in order to assess the probability of material failure, which is typically reflected by unstable crack propagation. Since fracture is an inherently multi-scale problem, critical regions are analysed in detail by means of a representative volume element. The resulting analysis reveals that in case the stress relaxation in the monoblock under the applied static heat load is complete, the probability of unstable crack propagation can reach values close to 35%. Finally, the impact of prolonged neutron irradiation is simulated by means of a cluster dynamics model. Although irradiation drastically increases the brittleness of tungsten, its impact on the overall monoblock performance remains limited. • The performance of tungsten monoblocks under fusion conditions is investigated. • Failure is predicted by application of the weakest-link theory on two length scales. • Stress relaxation increases the risk of failure upon shut down of the heat source. • The impact of neutron irradiation on the failure probability is shown to be limited.

Learning from superelasticity data to search for Ti-Ni alloys with large elastocaloric effect

In the present study, the reversible adiabatic temperature change (ΔTad) of shape memory alloys was shown to be proportional to the mechanical work released by the reverse martensitic transformation during unloading (ΔWu). As there exists a considerable amount of data (ΔWu) on superelastic stress-strain measurements in shape memory alloys, the proposed relationship allows us to predict ΔTad without caloric measurements. The estimated ΔTad from the ΔWu of different Ti-Ni alloys shows good linear relationship with the directly measured values. Moreover, following such a design criterion and by tuning of composition and thermo-mechanical treatment, a group of Ti-Ni binary shape memory alloys with directly measured ΔTad larger than 35 K under tension were achieved. The large ΔTad and ΔWu can be ascribed to the grain refinement and the heterogeneous internal stress fields after the thermo-mechanical treatment, which have enhanced the critical stress of superelasticity and recoverability of martensitic transformation during unloading.

Buckling analysis of symmetrically laminated composite plates including the effect of variable pre-stress field using the Ritz method

A buckling solution capable of accounting for prebuckling stress field heterogeneities is proposed. Oftentimes the same structural elements that restrict the out-of-plane displacement of the edges of a plate may also constrain their in-plane movements and cause heterogeneous prebuckling stress fields. The effect of these constraints and the consequent prebuckling stress field heterogeneity is vastly overlooked in the context of approximate analytical buckling solutions. The novelty of this work lies in basing the eigenvalue buckling analysis on a calculated prebuckling in-plane stress field. The in-plane stress field is determined by conducting a displacement-based linear elasticity analysis. In both elasticity and eigenvalue buckling analyses, the deformations of the anisotropic laminate were approximated using a first-order shear deformation theory. The equilibrium and instability equations were derived using the principle of stationary total potential energy and by employing the Ritz method. The derived formulation along with arbitrarily selected sets of boundary conditions was incorporated into a Matlab program and used for demonstrating the effect of in-plane constraints on prebuckling and buckling behavior of plates. Through a parametric study, the effect of the geometric configuration of plates on their buckling strength for selected symmetrical laminates was investigated.

Learning from Superelasticity Data to Search for Ti-Ni Alloys with Large Elastocaloric Effect

In the present study, the reversible adiabatic temperature change (ΔTad) of shape memory alloys was shown to be proportional to the mechanical work released by the reverse martensitic transformation during unloading (ΔWu). As there exists a considerable amount of data (ΔWu) on superelastic stress-strain measurements in shape memory alloys, the proposed relationship allows us to predict ΔTad without caloric measurements. The estimated ΔTad from the ΔWu of different Ti-Ni alloys shows good linear relationship with the directly measured values. Moreover, following such a design criterion and by tuning of composition and thermo-mechanical treatment, a group of Ti-Ni binary shape memory alloys with a directly measured ΔTad larger than 35 K under tension were achieved. The large ΔTad and ΔWu can be ascribed to the grain refinement and the heterogeneous internal stress fields after the thermo-mechanical treatment, which have enhanced the critical stress of superelasticity and recoverability of martensitic transformation during unloading.

Development of local plasticity around voids during tensile deformation

Voids can limit the life of engineering components. This motivates us to understand local plasticity around voids in a nickel base superalloy combining experiments and simulations. Single crystal samples were deformed in tension with in-situ high angular resolution electron back scatter diffraction to probe the heterogeneous local stress field under load; the reference stress is informed by crystal plasticity finite element simulations. This information is used to understand the activation of plastic deformation around the void. Our investigation indicates that while the resolved shear stress would indicate slip activity on multiple slip systems, slip is reduced to specific systems due to image forces and forest hardening. This study rationalizes the observed development of plastic deformation around the void, aiding in our understanding of component failure and engineering design.

Efficacy of shear strain gradients as an osteogenic stimulus

The question of which mechanical variables are responsible for inducing osteogenic activity is unresolved despite extensive experimental and theoretical investigation. Candidate variables include strain magnitude, loading frequency, the interaction of magnitude and frequency (strain rate), and strain gradients. An additional challenge is discerning the coordination of periosteal and endosteal expansion during growth, and whether this coordination (or lack thereof) is fully dependent or partially independent of the local mechanical environment.In this study, under the assumption that calculated stresses correspond to relative strain magnitudes, we specify alternative growth algorithms of bone cross-sectional size and geometry to explore skeletal growth under alternative scenarios of osteogenic activity that are tracking 1) an attractor stress, 2) local stress magnitude or 3) steepness of stress gradients. These developmental simulations are initiated from two initial geometries (symmetrical and asymmetrical ellipses) under a time-varying torsional load whose magnitude is proportional to body size growth in a model primate. In addition, we model endosteal expansion under three conditions hypothesized in the literature, in which endosteal expansion is 1) independent of the mechanical milieu, 2) completely dependent on the mechanical milieu, and 3) a “hybrid” model in which intrinsic biological (independent) growth is operative early but gives way to mechanically-sensitive (dependent) growth at later ages. Three variables were recorded over each growth simulation: the safety factor (ratio of yield stress to actual stress), an efficiency ratio (invested bone area per unit of stress), and proximity to an isostress condition (an optimal design criterion in which stress is invariant throughout the structure).The attractor stress algorithm produces the most “adapted” bones in terms of mechanical competence and economy of material. Localized osteogenic activity that is guided in direct proportion to stress magnitude produces competent bones but with variable adult geometries depending on conditions of endosteal expansion. Stress gradients also produce functional but relatively inefficient bones, with widely variable safety factors during growth and heterogeneous stress fields. If, in fact, the osteocyte network monitors strain gradients to generate osteogenic signals, the resulting morphology is competent but falls well short of an optimal mechanical solution.

New tectonic configuration in NW Iran: Intracontinental dextral shear between NW Iran and SE Anatolia

The Main Recent Fault (MRF) is a major active strike-slip fault system at the NE border of the Arabian platform and Central Iran. Both geometry and kinematics of the fault system is rather well known along its central part and at its SE termination, while its possible continuation to the northwest is ambiguous. Moreover, less regard has been paid to possible relationships between this major intracontinental fault system and other strike-slip faults in NW Iran – SE Anatolia. This paper investigates both the structural pattern and kinematics of deformation in the region to the north of latitude 37°N, between the North Tabriz Fault and the MRF. We followed this goal through detailed fault mapping, structural field measurements, and fault-slip analyses, complemented by the reconstruction of cumulative geomorphic offsets along the main fault segments. The collected data sets have led us to propose a new tectonic model for the northwest corner of the Arabia – Central Iran collision zone. Our results reveal that the intracontinental dextral shear between Arabia-Central Iran, which is mainly localized along the MRF, continues to the north of latitude 37°N along a branch of the Neotethyan suture penetrating into SE Anatolia. The dextral fault system abruptly dies out at latitude 37.5° N joining two NNW-striking normal fault zones, which accommodate the dextral translation of Central Iran relative to Arabia through ESE-trending extension. The region in NW Iran and SE Anatolia is affected by a heterogeneous active stress field due to different tectonic processes such as tectonic escape, block translation, and localized extension. The dynamics of these processes is either directly governed by the Arabia – Eurasia oblique convergence or indirectly controlled by frontal collision and pure shear deformation in central Anatolia.

The Influence of Development Target Depletion on Stress Evolution and Infill Drilling of Upside Target in the Permian Basin

SummaryThe extensive depletion of the development target triggers the demand for infill drilling in the upside target of multilayer unconventional reservoirs. However, such an infill scheme in the field practice still heavily relies on empirical knowledge or pressure responses, and the geomechanics consequences have not been fully understood. Backed by the data set from the Permian Basin, in this work we present a novel integrated reservoir-geomechanics-fracture model to simulate the spatiotemporal stress evolution and locate the optimal development strategy in the upside target of the Bone Spring Formation. An embedded discrete fracture model (EDFM) is deployed in our fluid-flow simulation to characterize complex fractures, and the stress-dependent matrix permeability and fracture conductivity are included through the compaction/dilation option. After calibrating reservoir and fracture properties by history matching of an actual well in the development target (i.e., third Bone Spring), we run the finite element method (FEM)-based geomechanics simulation to model the 3D stress state evolution. Then a displacement discontinuity method (DDM) hydraulic fracture model is applied to simulate the multicluster fracture propagation under an updated heterogeneous stress field in the upside target (i.e., second Bone Spring). Numerical results indicate that stress field redistribution associated with parent-well production indeed vertically propagates to the upside target. The extent of stress reorientation at the infill location mainly depends on the parent-child horizontal offset, whereas the stress depletion is under the combined impact of horizontal offset, vertical offset, and infill time. A smaller parent-child horizontal offset aggravates the overlap of the stimulated reservoir volume (SRV), resulting in more substantial interwell interference and less desirable oil and gas production. The same trend is observed by varying the parent-child vertical offset. Moreover, the efficacy of an infill operation at an earlier time is less affected by parent-well depletion because of the less-disturbed stress state. The candidate infill-well locations at various infill timings are suggested based on the parent-well and child-well production cosimulation. Being able to incorporate both pressure and stress responses, the reservoir-geomechanics-fracture model delivers a more comprehensive understanding and a more integral solution of infill-well design in multilayer unconventional reservoirs. The conclusions provide practical guidelines for the subsequent development in the Permian Basin.

The effect of hydrogen content and yield strength on the distribution of hydrogen in steel: a diffusion coupled micromechanical FEM study

In this study, we investigate the effect of the heterogeneous micromechanical stress fields resulting from the grain-scale anisotropy on the redistribution of hydrogen using a diffusion coupled crystal plasticity model. A representative volume element with periodic boundary conditions was used to model a synthetic microstructure. The effect of tensile loading, initial hydrogen content and yield strength on the redistribution of lattice (CL) and dislocation trapped (Cx) hydrogen was studied. It was found that the heterogeneous micromechanical stress fields resulted in the accumulation of both populations primarily at the grain boundaries. This shows that in addition to the well-known grain boundary trapping, the interplay of the heterogeneous micromechanical hydrostatic stresses and plastic strains contribute to the accumulation of hydrogen at the grain boundaries. Higher yield strength reduced the amount of Cx due to the resulting lower plastic deformation levels. On the other side, the resulting higher hydrostatic stresses increased the depletion of CL from the compressive regions and its diffusion toward the tensile ones. These regions with increased CL are expected to be potential damage initiation zones. This aligns with the observations that high-strength steels are more susceptible to hydrogen embrittlement than those with lower-strength.

Seismotectonic implications of the South Chile ridge subduction beneath the Patagonian Andes

AbstractThe South Chile ridge (SCR) intersects the Patagonian trench around 46°09′S, forming the triple junction among the Antarctic, Nazca, and South America plates. Subduction of the SCR since ~18 Ma produced the opening of a slab window beneath Patagonia and a noticeable magmatic gap in the cordillera, profuse volcanism and topographic uplift in the retroarc. To study seismicity distribution and present‐day stress resulting from this particular framework, we analyse databases of seismic events and earthquake focal mechanisms. Our study finds that clusters of intraplate crustal seismic events are disrupted by a ~450–470 km seismicity gap above the slab window. Calculated stress tensors depict a strike‐slip tectonic regime north of the triple junction, and ~W‐E compression to the south of the seismic gap. We propose that the seismotectonic behaviour of the upper plate is disturbed at the first order by the trench‐ridge intersection, leading to a heterogeneous stress field.

Metre-scale stress heterogeneities and stress redistribution drive complex fracture slip and fracture growth during a hydraulic stimulation experiment

SUMMARYWe investigated the induced seismicity, source mechanisms and mechanical responses of a decametre-scale hydraulic stimulation of a pre-existing shear zone in crystalline rock, at the Grimsel Test Site, Switzerland. The analysis reveals the metre-scale complexity of hydraulic stimulation, which remains hidden at the reservoir-scale. High earthquake location accuracy allowed the separation of four distinct clusters, of which three were attributed to the stimulation of fractures in the damage zone of the shear zone. The source mechanism of the larger-magnitude seismicity varied by cluster, and suggests a heterogeneous stress field already prevailing before stimulation, which is further modified during stimulation. In the course of the experiment, stress redistribution led to the aseismic initiation of a tensile-dominated fracture, which induced seismicity in the fourth of the identified seismic clusters. The streaky pattern of seismicity separated by zones without seismicity suggests fluid flow in conduits along existing fracture planes. The observed submetre scale complexity questions the forecasting ability of induced seismic hazard at the reservoir scale from small-scale experiments.

Численное моделирование неоднородного напряженно-деформированного состояния и прогноз изменения проницаемости прискважинной зоны при создании щелевой перфорации в терригенном коллекторе

The results of numerical simulation of the distribution of a heterogeneous stress field near the well for a sandstone reservoir formation when creating slotted perforation are presented. Variations in permeability are predicted depending on changes in the magnitude of effective stresses. Areas of restoration of permeability after the creating of slotted channels are revealed. It is shown that slotted perforation is an effective method for stimulating hydrocarbon inflow.

Fatigue performance evaluation of plate and shell heat exchangers

Fatigue life of plate and shell heat exchangers has been determined by experiments. Tests occurred with the aid of a pneumatic-hydraulic setup in which plate pack samples were internally pressurized by water. The samples were exposed to cyclic pressure loads varying from ambient to service pressure in the range 1.0–1.4 MPa, typical operating pressure range of crude oil production sites. Stress determination was possible due to strain gauge measurements. A heterogeneous stress field occurs along the corrugated plate due to its complex geometry. The external welded region is the preferential failure location. An average stress-life curve has been provided with 50% failure probability in accordance to ISO-12107. Fatigue strength reduction factors at the critical welded locations were determined via elastic stress analysis as proposed by ASME procedure. PSHE useful life increases with decreasing spacing between plates.

Simulation of fracture propagation and optimization of ball-sealer in-stage diversion under the effect of heterogeneous stress field

Ball-sealer in-stage diversion in horizontal wells is a key technique to realize the uniform stimulation of fractured sections in tight oil and gas reservoirs. So far, however, there are fewer research results on the propagation morphologies of multi-cluster fractures after the implementation of different ball-sealer in-stage diversion processes during the fracturing treatment, which results in less theoretical support for the preparation of field ball-sealer in-stage diversion process and measures and impacts its application effects in the fracturing field. To deal with this situation, this paper established a fully coupled “wellbore–perforation–fracture propagation” model of horizontal wells on the basis of the boundary element method. Then, a method for calculating the allocation of ball sealers was proposed. Finally, the number of ball sealers, diversion time and number of diversions during the intra-stage temporary plugging and diversion under the condition of initial heterogeneous stress field and their effects on the propagation of multi-cluster fractures were simulated. And the following research results were obtained. First, the flow restriction of perforation friction can counterbalance the intake difference caused by the induced stress interference so that the friction difference applied on the fluid flow in each fracture cluster is reduced. Second, when the effect of the heterogeneous distribution of the initial stress field is taken into consideration, the liquid intake of each fracture cluster changes greatly and even ineffective perforation clusters without liquid incoming appear in the high-stress region. And after the ball is injected, new fractures are initiated from the ineffective perforation clusters. Third, when the initial minimum horizontal principal stress difference (Δσh) is higher than 3 MPa, it is beneficial to reduce the non-uniform propagation of each fracture cluster by increasing the number of ball sealers appropriately in the middle stage of the construction (over half of the total perforations of each stage) or carrying out temporary plugging in the early–middle stage (including ball injection in batches in the early–middle stage). Fourth, when Δσh is lower than 2 MPa, it is necessary to reduce the number of ball sealers or inject balls in the middle–late stage, or the non-uniform propagation of each fracture cluster will be aggravated.

Spatiotemporal Change in the Stress State Around the Hypocentral Area of the 2016 Kumamoto Earthquake Sequence

AbstractFor understanding the physical condition of earthquake generation, we estimated the deviatoric stress fields and fault planes of the large earthquakes in the hypocentral area of the 2016 Kumamoto earthquake sequence, central Kyushu, Japan. We analyzed precise hypocenters and their focal mechanism tensors from 1993 to 2017 and found the complex fault planes of the largest foreshock and the mainshock during the sequence. The faults of large earthquakes could not be detected from the preceding high seismic activity in the area to the mainshock. The analyses of the deviatoric stress tensors obtained from pre‐ and post‐sequence seismic moment tensor data revealed the temporal change in the deviatoric stress field at the vicinity of the hypocenters of the largest foreshock and the mainshock. Because of this temporal change, we found that the stress level of the deviatoric stress field in this region is the same level as the co‐seismic stress change caused by the two large earthquakes. We attempted to estimate the differential stress at the region using a new method, which can be applied to the heterogeneous stress fields. The average value of the estimated differential stresses in the region was 15.4 ± 10 MPa. The rotation of the principal stress axes and the low differential stress are important information to understand the physical processes of the earthquake generation and the state of the crustal stress.

Enhanced non-linearity during unloading by LPSO phase in as-cast Mg-Zn-Y alloys and slip-dominated non-linear unloading mechanism

The non-linear unloading behavior and the underlying deformation mechanism of as-cast Mg-Zn-Y alloys with the long period stacking ordered (LPSO) phase were investigated. To evaluate the stress-strain behavior, compression-unloading tests under stress control were performed for as-cast alloys with six different volume fractions of the LPSO phase, which were produced using the high-frequency induction melt casting technique in an Ar atmosphere. The experimental results showed that the non-linearity during unloading was more significant for alloys with a higher volume fraction of the LPSO phase. The LPSO single-phase alloy, in which deformation twinning was hardly activated, exhibited the most significant non-linear unloading behavior, which originated from the small linear elastic region and the steep decrease in the instantaneous hardening modulus during unloading. Crystal plasticity finite-element analysis for the compression-unloading of the LPSO single-phase alloy indicated that the activity of the basal slip system during unloading led to non-linear unloading behavior. The heterogeneous stress distribution that developed during compressive deformation led to the activity of the basal slip system during unloading owing to the local stress tensor, whose normal stress component in the axial direction had opposite sign to that of the macroscopically imposed stress. Comparisons between numerical results with different implemented deformation modes, i.e., the basal slip system and the second-order pyramidal <c+a> slip system, indicated that strong plastic anisotropy contributes to the development of a pronounced heterogeneous stress field and an insignificant increase in the critical resolved shear stress before unloading, which leads to a higher non-linearity during unloading.

Local stress perturbations associated with the 2008 Wenchuan M 8.0 earthquake near the Longmenshan fault zone in the eastern margin of the Tibetan Plateau

The 2008 Wenchuan M 8.0 earthquake induced local stress perturbations near the Longmenshan (LMS) fault zone. Using in situ measurements and stress tensor inversions from focal mechanisms, we investigated the post-earthquake perturbed stress field at shallow depths (≤1.2 km), in the upper crust above a basal attachment (~5–18 km) as well as in the middle crust beneath a basal attachment (~19–32 km). At shallow depths in the Beichuan-Jiangyou section, the maximum principal stress (σ1) orientations changed from a pre-earthquake orientation of NWW to a post-earthquake orientation of NEE. However, near the Baoxing-An'xian and Qingchuan-Mianxian sections, the pre-earthquake σ1 orientation of NW-NWW was largely unaltered. Before the mainshock, in the upper crust above the basal detachment, the entire LMS fault zone exhibited a consistent σ1 orientation of NW-NWW. However, after the earthquake, some sections, such as the Beichuan-Nanba section, achieved σ1 orientations of NEE that were distinctly different from the pre-seismic stress field. In the middle crust beneath the basal detachment, the stress field was mostly unchanged. The crust beneath the basal detachment, along the eastern margin of the Tibetan Plateau, is dominated by NWW-oriented maximum principle stress and strain directions and a thrust faulting stress regime along the entire LMS fault zone; these observations are representative of the southeastward motion of the Bayan Har block and its ongoing collision with the South China block along the LMS thrust belt. The spatially heterogeneous stress field that occurred in the upper crust (≤18 km) after the mainshock was most likely caused by the co-seismic static stress changes associated with the Wenchuan earthquake. Prior to the onset of seismic activity, the deviatoric stress magnitudes were estimated at less than 22 MPa and 4 MPa at depths of 10 km and 20 km, respectively, suggesting that the mainshock fault zone has a relatively low fault strength to overcome, in order to initiate significant co-seismic rupture and aftershocks, especially in the crust beneath the basal detachment. These smaller deviatoric magnitudes are indicative of the weaker fault materials that resides in the LMS region.

Numerical approach to simulate the mechanical behavior of biodegradable structures considering degradation time and heterogeneous stress field

AbstractBiodegradable polymers are widely used to manufacture biodegradable devices, such as those used in regenerative medicine. In many cases, nonuniform degradation can arise from nonuniform stress fields. The developed numerical methodology can simulate the mechanical behavior of three‐dimensional structures subjected to loads during degradation after a given degradation time, thus providing a valuable tool for pre validation of biodegradable devices. Degradation rate was assumed as linear function of the local von Mises stress. Material model parameters change as degradation proceeds and hydrolytic damage increases. Hence, shear modulus of the neo‐Hookean constitutive model was assumed as linear function of hydrolytic damage. The methodology was developed in a finite elements' framework using ABAQUS/Standard. The local hydrolytic damage and the consequent shear modulus evolutions were calculated by means of a user material subroutine. The stress field affects locally the kinetics of degradation and the evolution of hydrolytic damage. Thus, local hydrolytic damage and the material parameter are updated at each time step to recalculate stress and strain fields at the inputted degradation time. The aim of this work was to allow the simulation of biodegradable devices subjected to both mechanical and chemical environments.

An experimental investigation of the nucleation and the propagation of NiTi martensitic transformation front under impact loading

The paper presents an experimental investigation of the NiTi superelastic shape memory alloy (SMA) under high-speed impact loading. A Split Hopkinson tensile bar (SHTB) and special short strikers are used to reach impact speeds exceeding 50 m/s. A very high-speed camera allows for the capture of full resolution images (924 × 768 pixels) at a sampling rate of 2 million frames/s. Digital image correlation (DIC) analysis provides good measurements of the strain field as well as the particle velocity field of the whole specimen.Experimental results shows that the increase of the critical transformation stress is much higher at strain rates around 103/s instead of a moderate increase at lower strain rates under 102/s. The heterogeneous stress field due to elastic wave propagation at high impact velocity leads to a heterogeneous transformation zone inside the specimen. The loading and the distal ends are the privileged sites of the martensitic transformation nucleation because of stress wave reflections. Transformation fronts will afterwards occur and propagate, driven by the stress increase at the loading end or that due to the loss of particle velocity (kinetic energy) at the distal end respectively. The jump condition across the front is respected. Finally, the cumulated martensitic phase length is traced when multiple fronts occur. It is found that the growing speed of this cumulated martensitic phase length remains proportional to the loading speed and that it can exceed the shear wave speed in the martensitic phase of the material.