Total Strain Research Articles

Finite Element Analysis of Delamination Initiation in Wind Turbine Blade Spar Caps: Role of Compression, Strain Energy, and Principal Stresses

In wind turbine blades, utilizing the finite element method (FEM) to identify potential failure modes before production provides considerable value and cost savings in contrast to conventional structural tests. This paper focuses on examining the factors leading to delamination in spar caps and exploring the initiation of this delamination using the finite element method. Compression, total strain energy density, and principal stresses are significant among the variables examined to determine the effects on model deformation and crack formation. Examining these variables may contribute to understanding the mechanisms involved in initiating and progressing delamination. This study examined the effects of compression, total strain energy density, and principal stresses on model deformation and crack formation. This study focuses on the effects of principal stresses on displacement, the effects of compression on delamination and crack formation, and the effects of total strain energy density on fracture tendency and failure modes due to delamination.

Using In-Building Observations of Small-to-Large Earthquakes to Predict the Seismic Response of Structures

ABSTRACT The main goal of this study is to evaluate the potential value of data from weak-to-moderate earthquakes for structural response analysis. Data recorded over 18 yr by the seismic network installed in the 12-stories Grenoble City Hall Building (France) is considered. The building response is analyzed in terms of intensity measures and engineering demand parameters, and then compared with strong earthquake data recorded in Japanese buildings. The uncertainties of structural response prediction are estimated and defined in terms of “within-building” and “between-building” components in the same way as the components of the ground-motion model. Data complementarity in the response model is observed between the weak-to-moderate (France) and the moderate-to-strong (Japan) earthquake datasets, disclosing nonlinear processes (associated with resonance period elongation) that are activated in buildings during low-to-strong motion. For example, fundamental frequency shifts are triggered at low values of both total structural drift amplitudes and equivalent strain rates (i.e., time derivative of structural drift). In addition, strain rate thresholds from 10−11 s−1 to 10−5 s−1 representing different structural conditions from undamaged to severely damaged buildings are observed to activate nonlinearities. This confirms the link between loading rates and structural conditions. Our results highlight the interest in instrumentation in buildings located in regions of weak-to-moderate seismicity, for (1) the development and calibration of realistic models for predicting the seismic response of structures, (2) for improving our understanding of the components of uncertainties in the risk assessment of existing buildings, and (3) to investigate physical processes activated in structures during seismic loading that influence their response.

Design of FDM fabricated poly-lactic acid parts with forced-air cooling speed as the new control parameter to tune its shape memory effect

Poly lactic acid (PLA) as one of the shape memory polymers has extensively been used as the material in the 3D printing by fused deposition modeling process. In this study, we introduced the forced-air cooling speed as new control parameter in the fabrication process. A commercial material extrusion printer was retrofitted with a control module of forced-air cooling system. The shape memory effects of the PLA printed in different cooling speeds from 0–5 m s−1 were first measured by submerging the printed coupon specimens into water bath at recovery temperature. It is found that the changes in dimensions were mainly anisotropic and dependent of the raster angle in printing, in addition to the controlled cooling speed. The shape memory strains were roughly in linear trend with the magnitude of cooling air speed. In other words, the shape memory effect of the PLA can be easily controlled by the cooling air speed in fabrication. X-ray diffraction measurement on the specimens before and after recovery treatment confirmed the shape memory effect was related to the partial crystallization of molecular structure. Moreover, the different cooling air speeds also induced different thermal stresses in the printed specimens which manifest its important role in the total shape memory strain. Finally, the proposed theoretical beam formulation for the recovery bending deflection was shown to have good prediction accuracy comparing with experimental measurements.

An informatics method for inferring the hardening exponent of plasticity in polycrystalline metals from surface strain measurements

The investigation of strain hardening in metals is complex, with the outcome depending on experimental conditions, that may involve microstructural history, temperature and loading rate. Hardening is commonly measured, after mechanical processing, through controlled mechanical testing, in ways that either distinguish elastic (stress) from total deformation measurements, or by identifying plastic slip contributions. In this paper, we conjecture that hardening effects can be unraveled through statistical analysis of total strain fluctuations during the evolution sequence of profiles, measured in-situ, through digital image correlation. In particular, we hypothesize that the work hardening exponent is related, through a power-law relationship, to a particular exponent arising from principal component analysis. We demonstrate a scaling analysis for synthetic data produced by widely applicable crystal plasticity models for polycrystalline solids.Graphical

Numerical modeling and analysis of cardiac stent using blood hammer principle.

Atherosclerosis is a condition which disrupts blood flow due to plaque build-up inside the arteries. Under conditions where consecutive plaques are prevailing blood hammer principle is exhibited. The pressure and shear stress produced at an infinitesimal area act as the governing equation for stent modeling. The leading order pressure lays the foundation for the design of cardiac stents with definite dimensions. The designed stent was encapsulated inside a crimper validated through ANSYS-static and transient structural simulation to derive the total deformation, equivalent strain, and stress exerted on the stent. Five different biomaterials stainless steel 316, cobalt, chromium, platinum, and Poly lactic acid were selected for the material assessment. Static and Transient structural analysis for a period of 1 and 10 secs was implemented for a stent with and without a crimper. The material performance in terms of total deformation, equivalent stress, and strain are analyzed. The paper envisions the dynamics of blood hammer in atherosclerosis that provides the changes in the pressure and clotting process. It shows the promising results of the stent behavior in varied forces which gives valuable insights for future improvement in stent design and material selection.

In-situ observation of variant pair formation in bainite of low carbon steel by digital holographic microscopy

Digital holographic microscopy (DHM) was employed to investigate the formation process and shape evolution of the most frequently observed bainite variant pairs in low-carbon alloy steel. Through in-situ observation coupled with theoretical predictions, the continuous changes in surface relief corresponding to bainite and adjacent austenite were measured. Additionally, the crystal orientations of the observed variant pairs were determined using electron backscattered diffraction (EBSD). The results indicated that at the onset of the transformation, the bainite variant shape agreed with theoretical predictions, while the adjacent austenite experienced plastic deformation. However, as the transformation proceeded towards completion, the shape of some bainite variants deviated from the theoretical predictions, while their adjacent austenite remained undeformed. This shift of deformation strain between austenite and bainite suggests a change in strain accommodation mechanism. Furthermore, the observed ‘tent-shaped’ surface relief was attributed to back-to-back mutually accommodating variant pairs, resulting in reduction of the total shape strain, compared to the theoretical prediction.

Synchrotron-based x-ray diffraction analysis of energetic ion-induced strain in GaAs and 4H-SiC

Strain engineering using ion beams is a current topic of research interest in semiconductor materials. Synchrotron-based high-resolution x-ray diffraction has been utilized for strain-depth analysis in GaAs irradiated with 300 keV Ar and 4H-SiC and GaAs irradiated with 100 MeV Ag ions. The direct displacement-related defect formation, anticipated from the elastic energy loss of Ar ions, can well explain the irradiation-induced strain depth profiles. The maximum strain in GaAs is evaluated to be 0.88% after Ar irradiation. The unique energy loss depth profile of 100 MeV Ag (swift heavy ions; SHIs) and resistance of pristine 4H-SiC and GaAs to form amorphous/highly disordered ion tracks by ionization energy loss of monatomic ions allow us to examine strain buildup due to the concentrated displacement damage by the elastic energy loss near the end of ion range (∼12 μm). Interestingly, for the case of SHIs, the strain-depth evolution requires consideration of recovery by ionization energy loss component in addition to the elastic displacement damage. For GaAs, strain builds up throughout the ion range, and the maximum strain increases and then saturates at 0.37% above an ion fluence of 3×1013 Ag/cm2. For 4H-SiC, the maximum strain reaches 4.6% and then starts to recover for fluences above 1×1013 Ag/cm2. Finally, the contribution of irradiation defects and the purely mechanical contribution to the total strain have been considered to understand the response of different compounds to ion irradiation.

Orientation dependence of nickel-based single crystal superalloys in VHCF regime

Aimed at research the deformation orientation in VHCF regime under different temperatures, fatigue behavior of [111]-oriented DD6 single crystal superalloy at 1000 °C and 760 °C was studied. Using the stress range criterion, the [111] orientation shows higher fatigue resistance. This difference decreases with lower stress ranges and almost vanishes near 109 cycles. In contrast, the [111] orientation has lower fatigue resistance than the [001] orientation by using the total strain range criterion. Dislocations are restricted from shearing the γ’ phase due to the lower octahedral resolved shear stress in the [111]-oriented, decreasing the deformation in γ’ phase. Combined with distinctive cross-slip behavior, this further increased the deformation along the γ-channel, significantly enhancing deformation inhomogeneity between the γ’ phase and γ-channels. At elevated temperatures, thermally activated dislocation climb and higher climb stress factor lead to a greater reduction in fatigue performance for [111] orientation at lower stress level.

Temperature distribution in the PGAA system: Collimator, shutter, and filter in TRIGA Mark II reactor

This article examines the impact of temperature on the steel collimator cap and the primary beam shutter. These components will be used to implement the Prompt Gamma Activation Analysis (PGAA) technique in the Moroccan TRIGA Mark-II research reactor. The steel collimator plug is essential for forming the neutron beam, while the main role of the shutter is to stop the beam when the channel is inactive. This study analyzes the effect of temperature on the collimator and shutter system, particularly focusing on the variation in maximum temperature over a month of operation with 8-h cycles per day, the behavior of temperature over 24 h, the total heat flux as a function of the length of the experimental device, the temperature distribution in mild steel (E235) and 304L stainless steel materials, and the total displacement and strain gradient as a function of temperature. All calculations were performed using COMSOL Multiphysics simulation software, based on the finite element method.

Distributed-collaborative surrogate modeling approach for creep-fatigue reliability assessment of turbine blades considering multi-source uncertainty

This paper proposes a substructure-based distributed-collaborative surrogate modeling approach for improving the accuracy and efficiency in the estimation of the creep-fatigue reliability of gas turbine blades with the integration of the Least Absolute Shrinkage and Selection Operator (LASSO), kriging, Distributed Collaborative (DC) strategy and substructure simulation method, called as the substructure-based DCLKM. Further, the creep-fatigue reliability assessment framework is set by combining the proposed substructure-based DCLKM with some theoretical models, which takes into account the uncertainties of structural sizes, applied loads and material properties and the nonlinearity of creep/fatigue damage interaction. Firstly, the total strain range, mean stress, absolute temperature and maximum stress at the critical location are regarded as the first-level output responses, and their required samples are predicted through the fitted surrogate models. Secondly, the creep life and Low-Cycle Fatigue (LCF) life are regarded as the second-level output responses and predicted. Finally, the creep-fatigue damage and reliability assessment are performed for several given applied cycles, respectively. The proposed substructure-based DCLKM is validated on a case study. The results show that the proposed substructure-based DCLKM is feasible with high accuracy and efficiency in the creep-fatigue reliability assessment of turbine blades.

Experimental Characterization and Phase-Field Damage Modeling of Ductile Fracture in AISI 316L

(1) Modeling and characterization of ductile fracture in metals is still a challenging task in the field of computational mechanics. Experimental testing offers specific responses in the form of crack-mouth (CMOD) and crack-tip (CTOD) opening displacement related to applied force or crack growth. The main aim of this paper is to develop a phase-field-based Finite Element Method (FEM) implementation for modeling of ductile fracture in stainless steel. (2) A Phase-Field Damage Model (PFDM) was coupled with von Mises plasticity and a work-densities-based criterion was employed, with a threshold to propose a new relationship between critical fracture energy and critical total strain value. In addition, the threshold value of potential internal energy—which controls damage evolution—is defined from the critical fracture energy. (3) The material properties of AISI 316L steel are determined by a uniaxial tensile test and the Compact Tension (CT) specimen crack growth test. The PFDM model is validated against the experimental results obtained in the fracture toughness characterization test, with the simulation results being within 8% of the experimental measurements. (4) The novel implementation offers the possibility for better control of the ductile behavior of metallic materials and damage initiation, evolution, and propagation.

Association between global longitudinal strain and occurrence of cardiovascular events among pediatric patients following high-dose cyclophosphamide chemotherapy: a prospective cohort study.

The fatal cyclophosphamide cardiotoxicity is associated with high mortality in the adult population, and the study of its effects on children represents a gap in the field. This study aimed to evaluate the potential of global longitudinal strain (GLS) as a predictor of cardiovascular events among children with high-dose cyclophosphamide chemotherapy. This was a prospective cohort study of patients aged 14 years or younger who received high-dose (>120 mg/kg) cyclophosphamide chemotherapy recruited consecutively. Blood collection and echocardiography were performed 1 day before and after cyclophosphamide chemotherapy, and patients were followed up for 30 days with echocardiography. GLS and other echocardiography indicators were calculated accordingly. The primary outcome was the occurrence of cardiovascular events within 30 days after cyclophosphamide chemotherapy. The association between GLS and outcome was analyzed by using univariate and multivariable-adjusted Poisson regression. A total of 29 subjects were included. Among them, 10 patients (34.48%) developed cardiovascular events during a median follow-up of 10 (interquartile range, 5-13) days. Although similar before cyclophosphamide chemotherapy, GLS 1 day after cyclophosphamide chemotherapy was significantly lower in the cardiac injury group than in the noncardiac injury group (-18.33%±1.81% vs. -20.03%±1.49%, P=0.01). In the multivariable analysis adjusted for total cyclophosphamide dose (160 vs. 120-159 mg/kg) and global circumferential strain, GLS remained an independent predictor for cardiovascular events [incidence rate ratio: 1.46, 95% confidence interval: 1.02-2.09, P=0.04]. GLS after cyclophosphamide chemotherapy may be a reliable indicator to predict cardiovascular events in patients receiving cyclophosphamide chemotherapy, which might be essential in optimizing treatment strategies for this high-risk patient group.

Влияние поражения сердца на прогноз у пациентов с системным AL-амилоидозом

AIM. To assess the clinical features as well as the factors affecting prognosis and long-term treatment outcomes in systemic AL amyloidosis patients with cardiac involvement. MATERIALS & METHODS. The trial enrolled 123 systemic AL amyloidosis patients with cardiac involvement who were treated at the RM Gorbacheva Scientific Research Institute in 2004–2023. The patients were 34–85 years of age (median 61 years); there were 61 women (49.6 %) and 62 men (50.4 %). RESULTS. Cardiac disease grades 1, 2, 3a, and 3b were identified in 13.8 %, 50.4 %, 17.9 %, and 17.9 % of AL amyloidosis patients, respectively. Chronic cardiac failure (CCF) developed in 65.9 % (n = 81), and severe cardiac failure was detected in 25.4 % (n = 31) of patients. Most of them (90,2 %), despite CCF, preserved left ventricular ejection fraction (> 40 %) with the mean value of 59.6 % (range 33–78 %). The left ventricular stroke volume index (SVI) was below the normal values (< 41 mL/m2) in 92.7 % of patients. The mean SVI value was 26.1 mL/m2 (range 8.3–49.5 mL/m2). The lower SVI was associated with cardiac disease grades. This parameter appeared to be 30.9 mL/m2, 26.8 mL/m2, 24.8 mL/m2, and 21.4 mL/m2 in grades 1, 2, 3a, and 3b (p = 0.006), respectively. Total global strain (TGS) in the left ventricle myocardium was decreased (< 20 %) in 94.6 % of patients. The mean TGS value was 13.8 % (range 4.4–34.8 %). TGS was diminishing with increasing cardiac disease grade (grade 1 with 17.8 %, grade 2 with 14.6 %, grade 3a with 13.1 %, and grade 3b with 9.6 %) (p = 0.007). Atrial fibrillation was reported in 23 % of patients, supraventricular tachycardia was observed in 31.9 %, and supraventricular extrasystoles were registered in 39.7 %. Ventricular extrasystoles were found in 73.7 % of patients, and ventricular tachycardia was seen in 13.2 %. Sinoatrial block was reported in 6.6 % of patients, and atrioventricular block was identified in 19.8 %. Syncope occurred in 12.3 % of patients. An artificial cardiac pacemaker was implanted in 8 patients. The thromboembolism rate was 13 %: the myocardial infarction rate was 11.4 %, and the rate of acute cerebrovascular accidents was 5.7 %. Atrial clots were detected in 2 (1.6 %) patients. The cumulative incidence of hematologic response for 2 years was 57 % and did not depend on cardiac disease grade, the 2-year rate of cardiac response was 39.1 %. Before achieving hematologic and cardiac responses, mortality was 26.5 % and 29.9 %, respectively. The overall 5-year survival was 62.6 %, and the 5-year hematologic progression-free and major organ impairment-free survival was 39.3 %. Cox regression model confirmed 3 independent predictors of poor prognosis: the level of NT-proBNP ≥ 2500 pg/mL (p = 0.004), SVI < 25 mL/m2 (p = 0.0174), and prior syncope (p = 0.0191). The achievement of hematologic response had a positive effect on survival rates (p < 0.0001). CONCLUSION. A comprehensive assessment of cardiac damage by the time of primary AL amyloidosis diagnosis as well as appropriate treatment of this disease can reduce the risk of early cardiac mortality and enhance chances of not only achieving hematologic response but also improving survival rates.

A comparison of conventional and additively manufactured 316L under thermomechanical fatigue

The present study compares the thermomechanical fatigue (TMF) behaviour of 316L stainless steel manufactured conventionally by hot rolling and additively by laser powder bed fusion (L-PBF). Machined cylindrical specimens were tested under strain-controlled in-phase and out-of-phase TMF loading at a temperature range of 550–750 °C and total mechanical strain amplitudes of εamech = 0.2–0.6 %. While the conventional 316L significantly outperforms the L-PBF 316L under in-phase TMF, their lifetimes are comparable under out-of-phase TMF. Under in-phase TMF, creep damage in the form of intergranular crack networks occurs which is significantly more pronounced for the L-PBF 316L due to the higher amount of interfaces. Under out-of-phase TMF, the damage is mostly due to stress-assisted oxide cracking and the crack propagation is fatigue-dominated. TEM inspection revealed that L-PBF 316L exhibits a cellular dislocation structure in the initial state, which rearranges only slightly during cycling. For conventional 316L similar dislocation cells form during TMF cycling indicating that they represent a stable dislocation arrangement in 316L under TMF loading. This is evidenced by the rather stable cyclic stress response of the L-PBF material when compared to the conventional material.

Fractal Characteristics and Energy Evolution Analysis of Rocks under True Triaxial Unloading Conditions

To investigate the mechanical properties and energy evolution laws of rocks under true triaxial unloading conditions, a study was conducted using a true triaxial rock testing system on three different types of rocks: coal, sandy mudstone, and siltstone. The study examined the mechanical behavior, failure patterns, and fractal dimensions of these rocks under true triaxial unloading conditions. The tests revealed significant variations in stress–strain curves and failure patterns among the different rock types. Observation indicated that rocks with lower peak strength exhibited higher fractal dimensions and increased fragmentation upon failure. Subsequently, based on the experimental data of siltstone, the impact of the unloading rate and particle size distribution on the energy evolution under true triaxial single-sided unloading paths was further investigated using the three-dimensional particle flow software PFC3D 6.0, revealing the micro-mechanisms of rock energy evolution. The study revealed that when the initial stress unloading level was low, the total energy and strain energy at the peak strength exhibited a strong linear relationship with the unloading rate. Before the stress peak, the dissipative energy was mainly composed of frictional energy. After the stress peak, the dissipative energy consisted of frictional energy, damping energy, and kinetic energy. The heterogeneity of rock significantly affected the distribution of dissipative energy, with an increase in rock heterogeneity leading to a decrease in frictional energy and an increase in kinetic energy.

Experimental study on failure mechanism of soft rock-coal bodies in abandoned mines under cyclic dynamic loading

During the construction and operation of a pumped storage power station in an abandoned mine, the soft rock-coal body structure, comprising the roof and the residual coal pillars, encounters a complex stress environment characterized by cyclic loads. The study of its failure mechanism under cyclic dynamic loading holds significant theoretical and practical importance to stay the safety and stability of the abandoned mine pumped storage power station. In this paper, we take “roof-residual coal pillar” soft rock-coal combinations with different percentages of rock as the research object, and study their mechanical properties, failure mechanism, energy evolution characteristics and acoustic emission distribution characteristics through cyclic dynamic loading experiments. The results of the experiment indicate that: (1) Both weak cyclic dynamic loading and high rock percentage enhance the deformation resistance of soft rock-coal combinations. Under low-disturbance horizontal cyclic loading, its peak strength and modulus of elasticity increase with increasing rock percentage. (2) Under low-disturbance horizontal cyclic loading, an increasing trend is observed in the average total strain energy density, dissipation energy density, and elastic energy density of the combinations as the percentage of rock increases. (3) Under low-disturbance horizontal cyclic loading, as the percentage of rock increases in the soft rock-coal combinations, the degree of failure in the rock body part progressively intensifies, while the destruction of the coal portion progressively decreases. (4) The large number of acoustic emission signals are generated at the instant of destabilization and destruction of the coal-rock combinations, mainly dominated by the signals generated by the destruction of the coal body. Acoustic emission counts and absolute energy at key point N2 decrease as the percentage of rock increases. The b value is primarily distributed in the cyclic dynamic loading stage and the failure stage, both displaying zones of sudden increase and sudden decrease in b value.

Mechanical Properties and Energy Damage Evolution Mechanism of Basalt Fiber-Modified Tailing Sand Cementation and Filling Body Mechanics

In order to investigate the mechanical properties of basalt fiber-doped tailing sand cemented filler and the evolution of energy damage, a uniaxial compression test was carried out on the basalt fiber-doped tailing sand cemented filler specimens to analyze the energy dissipation characteristics, and the damage constitutive equations with different basalt fiber contents were established based on damage mechanics. The results show that with the increase of fiber doping and fiber length, the uniaxial compressive strength and ductility of the filling body show a trend of increasing and then decreasing; the optimal value of fiber doping is 0.6%, and the optimal value of fiber length is 9 mm; the total strain energy, elastic strain energy and dissipation energy of basalt fiber-modified tailing sand cemented filling body at peak stress show a trend of increasing and then decreasing, and the energy dissipation energy of the filling body shows a trend of increasing and then decreasing. The energy dissipation energy shows a trend of increasing and then decreasing, and the energy dissipation energy shows a trend of increasing and then decreasing. The total strain energy, elastic strain energy, and dissipation energy at the peak stress show a trend of decreasing after increasing with the fiber doping and fiber length, and the energy damage evolution process can be divided into four stages: no damage stage, stable damage development stage, accelerated damage growth stage, and damage destruction; in addition, the existing damage constitutive model of the fiber-filled body was optimized, and the damage correction factor was introduced to obtain the damage constitutive model of the filled body with different fiber contents, and finally, after the verification of experimental and theoretical models, it was found that the two stress–strain curves coincided well. Finally, after the test and theoretical model verification, it is found that the stress–strain curves of the two are in good agreement, which indicates that the established theoretical model has a certain reference value for engineering practice, and at the same time, it has certain limitations.

New strain configuration of convergence in the Arabia-Eurasia collisional zone: A comprehensive analysis of large shear zones inferred from geodetic and seismic observations

A new strain configuration is presented concerning the ongoing convergence deformation field in the Turkish-Iranian High Plateau (TIHP), E Anatolia-NW Iran. The strain configuration is derived from the contribution of geodetic strain-rate fields using GPS velocity data to reveal new constraints not documented previously in the region. This provides good evidence for novel “highland shear strain zones” by analysis of the combination of interpolated GPS velocity fields and seismological observations with maximum principal strain axes. Both the strain-rate fields and rotational elements of the estimated geodetic deformation exhibit juxtaposed, patchy strain rate partitioning in E Anatolia-NW Iran. These comprise both compressional strain lobes combined with local extensional areas and large shear strain fields in the core of the collision where the rotation rate fields present an unexpected propagation zone of continuous, counterclockwise rotation towards the W. The main results define approximately N-S- and W-E-trending, large, continuous, diagonal shear strain patterns with high total strain rate and maximum shear strain rate, consistent with right-lateral strike-slip and normal focal mechanisms. These are the Longitudinal Shear Zone (LSZ) extending from S to N and dividing the TIHP into the E Anatolia and NW Iran blocks, and the right-lateral Transcurrent Shear Zone (TSZ) extending from E (NW Iran) to W (E Anatolia). These differential movements of the inconsistent LSZ and TSZ shape both the highly buoyant plateau topography and the area, which undergoes migration to the W with respect to stable Eurasia by means of plateau push. Geodetic deformation compatible with fault focal data indicates that the LSZ and TSZ, in the framework of thermal and mechanical changes in the structure of the lithospheric thickness beneath the TIHP, are invaded and shaped by flowing mantle material that triggers and drives lateral escape of convergent crustal blocks, and configures the convergence with a shear-dominated deformation regime. The shear regime is primarily driven by NE- and NW-directed mantle flow fields and associated buoyancy forces due to slab fragmentation and tears in the region, exerting dominant control over the differential evolution of the LSZ and TSZ patterns. The new strain configuration for this convergence illuminates “the highland tectonics of large shear zones” resulting from slab thinning or its absence, and challenges conventional tectonic strain models in the TIHP.

STRUCTURAL ANALYSIS OF A LIGHTWEIGHT ELECTRIC VEHICLE CHASSIS

This study presents a comprehensive investigation into the design and structural analysis of lightweight chassis for electric vehicles. A chassis needs to be able to withstand twist, shock, vibration, and other stresses caused by acceleration, braking, road condition, and shock initiated by other parts of a vehicle. It should carry a maximum load under all operating conditions. Two materials, 304L steel, and Ti-6AL-4V alloy were evaluated, with parameters such as total deformation, equivalent stress, and equivalent elastic strain under consideration. The outcome of the Finite Element Analysis revealed that Ti-6AL-4V can withstand higher stresses than 304L Steel. By investigating the static behaviors of the chassis under static loading due to weight and overload conditions, Ti-6AL-4V was chosen as a suitable replacement for a 304L Steel chassis.

Influence of deep rolling on the [formula omitted]’-martensite formation in the subsurface, geometrically necessary dislocations and corrosion resistance of austenitic stainless steel AISI 304

The influence of deep rolling (DR) parameters (speed, number of passes and pressure) on the equivalent total strain, α’-martensite formation, ultra-microhardness, microstructure, and corrosion resistance of an AISI 304 austenitic stainless steel was investigated. The results showed that increasing DR speed led to less heterogeneous strain distributions and relatively high ultra-microhardness, despite an overall reduction in strain and α’-martensite content. This increase in hardness was related to the rise of geometrically necessary dislocations (GNDs) density, found to be one of the primary microstructural features influencing mechanical behavior under high DR speed. The increase in the number of passes elevated the intensity and depth of strain, leading to a 70% increase in the content of α’-martensite, ultra-microhardness, and producing severe grain refinement. The GNDs density decreased in the refined grain layer and increased sharply below it. Increased pressure induced similar results relative to the number of passes, with less impact. Improvement in the material properties is achieved through the interaction of parameters that result in an increase in the severity of the DR process, i.e, a reduction in speed and an increase in the number of passes and pressure. For severe DR conditions, the materials corrosion resistance in a 3.5% NaCl aqueous solution was significantly improved, with an increase of up to 2488% in the polarization resistance, as assesssed by electrochemical impedance spectroscopy. In potentiodynamic polarization tests, the corrosion potential increased from an average value of −0.274 to −0.14 V, and the corrosion current density decreased by approximately 300%.