Yield Strength Of Material Research Articles

Correlating microstructure and mechanical properties of harvested high dose Zorita light water reactor internals

In this study, microstructural studies and micro-mechanical testing of an ex-plant material harvested from the decommissioned pressurized water reactor (PWR) is carried out. Irradiated 304 stainless steel (SS) components were harvested by the Electric Power Research Institute, U.S. Nuclear Regulatory Commission, and members of the José Cabrera Nuclear Power Station (Zorita) in Spain. The bi-crystalline micro-tensile specimens, atom probe tomography (APT) tips, and transmission electron microscopy (TEM) lamellae were fabricated from the baffle plate materials irradiated to 0.05, 15 and 50 dpa to elucidate microstructural, microchemical, and local mechanical properties changes as a function of dose. TEM and APT studies reveal radiation induced Ni, Cr, and Si rich precipitates in the 15 dpa sample that become smaller and partially redissolve into the matrix of the 50 dpa sample (decreasing size and number density). Dislocation loop and cavity number density and size were quantified as a function of dose as well as swelling. Intergranular Ni and Si enrichments with concomitant Fe and Cr depletion were observed in the 15 dpa sample and were more pronounced in the 50 dpa sample. Micro-tensile testing performed in the scanning electron microscope (SEM) at room temperature and 300 °C shows that the material's local yield strength and ultimate tensile strength decreases with increased dose and elevated test temperature and provides further insights via localized strain mapping. Current and previous mechanical data was compared with calculated values using the dispersed barrier hardening model with inputs of dislocation loops, precipitates, and cavities from microstructural characterization.

Small punch evaluation of mechanical properties for 310S stainless steel considering pre-strain effect

Strain strengthening technology is widely used in practical engineering to increase the allowable stress of materials in pressure vessel manufacturing. Small punch analysis was performed using less material in this study to analyse the influence of pre-strain on the mechanical properties of 310S stainless steel. The results indicated that the material yield strength and ultimate tensile strength increased with pre-strain deformation. Similarly, the small punch characteristic parameters increased owing to the influence of the pre-strain, proving that the small punch test could estimate the evolution of mechanical properties along with pre-strain deformation. Small punch characteristic parameters at different deformation stages were analysed. In addition to the maximum load, small punch parameters at the inflection point were used in the ultimate tensile strength estimation. The small punch deformation features and stress distribution were discussed based on numerical simulations. Finally, an ultimate tensile strength estimation method based on membrane stretching model was proposed. Additionally, the strain hardening parameters considering the effect of pre-strain deformation were discussed.

A novel analytical method for local buckling check of box sections with unequal wall thicknesses subjected to bending

This study develops a novel analytical method to evaluate if box sections, with unequal wall thicknesses under bending, will undergo local buckling prior to reaching their yield strength since the analytical determination of critical local buckling stresses for such sections remains unexplored due to the lack of local buckling coefficients, warranting further investigation in scholarly discourse. Despite not directly computing the local buckling stresses, the developed method specifies a possible critical local buckling stress range by incorporating reference, critical, and equivalent section models, all formulated and developed with uniform wall thicknesses. The formulated method proficiently discerns the occurrence of local buckling by conducting a comparative assessment of the yield strength of the box section material against both the lower (min) and upper (max) bound stresses of the critical local buckling stress range. If local buckling persists unclear after the initial benchmark, the method reaches the final conclusion by comparing the constant wall thickness of the critical section with the web thickness of the box section. The developed method validated against finite element results obtained from linear elastic eigenvalue buckling analyses can be applied to the problem of determining whether such box sections subjected to bending will experience local buckling.

Unveiling yield strength of metallic materials using physics-enhanced machine learning under diverse experimental conditions

In the materials science domain, the accurate prediction of the yield strength of metallic compositions has often resulted in extensive experimental endeavors, leading to inefficiencies in both time and resources. Here, we introduce an innovative approach to predict yield strength, which can be applied to a variety of metallic substances ranging from the simplest pure metals to the most intricate alloys under varying temperatures and strain rates. The fusion of grain boundary sliding mechanism and cutting-edge machine-learning algorithm forges an expansive framework, which can help realize the critical factors influencing yield strength. The validity and wide applicability of the proposed framework were rigorously confirmed through experimental evaluations conducted on selected Fe-based alloys, such as Fe60Ni25Cr15, Fe60Ni30Cr10, and Fe64Ni15Co8Mn8Cu5. This breakthrough study significantly streamlines experimental design processes, optimizes resource utilization, and marks a significant leap forward in creating a reliable predictive framework for realizing material properties.

Theoretical Modeling of Temperature, Strain Rate and Porosity Dependent Yield Strength of Porous Metallic Material

Theoretical Modeling of Temperature, Strain Rate and Porosity Dependent Yield Strength of Porous Metallic Material

Experimental and numerical investigations of S890 and S960 ultra-high strength steel circular hollow section columns

The experimental and numerical investigations of the buckling behaviour and load-carrying capacities of S890 and S960 ultra-high strength steel (UHSS) circular hollow section (CHS) columns were conducted and reported in this paper. The experimental program encompassed tensile coupon tests, initial global and local geometric imperfection measurements and pin-ended column tests. Parallelly, the numerical modelling program was carried out, where the developed finite element (FE) models were validated with reference to the experimental observations and then employed in parametric studies to result in additional numerical data, considering various cross-sectional dimensions and member lengths. Based on the obtained FE and test data, the applicability of the relevant codified design buckling curves in the current European, Australian and American specifications to S890 and S960 UHSS CHS columns was evaluated, since the aforementioned standards only cover the design rules with steel material yield strength no greater than 700 MPa. The assessment results showed that the European code and Australian standard can generally accurately predict the resistances of S890 and S960 UHSS CHS columns, but result in some unsafe data points, while the American specification yielded accurate and consistent resistance predictions. Finally, a revised Eurocode design buckling curve was proposed, accompanied by the reliability assessment through statistical analyses, with the improved design accuracy and consistency revealed.

Model for predicting temperature-dependent indentation yield strength and hardness considering size effects

The development of theoretical models to facilitate access to the mechanical properties of materials has been a long-standing pursuit of scholars. In this study, temperature-dependent yield strength models and temperature-dependent hardness models considering indentation size effects were developed under different loading modes (loading to the same displacement or the same load at different temperatures), respectively. Based on the Force-Heat Equivalence Energy Density Principle, the proposed models are free of any adjustable fitting parameters, and the quantitative relationships among temperature, yield strength/hardness, Young's modulus, and indentation load/displacement were successfully captured. All the available 36 groups of experimental data validate the accuracy of the proposed models over a wide temperature range. The yield strength and hardness of metallic materials over a wide temperature range can be easily predicted by using the developed models. Based on the parametric analysis of the models, it has been theoretically clarified for the first time that the two loading modes have opposite indentation size effects for the same material. Although the indentation size effect all decreases gradually with increasing temperature for different loading modes. The influence of loading modes should be noted in future studies where temperature-dependent indentation size effects need to be considered. This work systematically considers the effects of temperature, loading mode, indentation load/displacement, and Young's modulus on the indentation yield strength and hardness, which is important to facilitate the study of the deformation behavior of materials at different temperatures by indentation methods.

Performance Optimization Design Study of Box-Type Substations Subjected to the Combined Effects of Wind, Snow, and Seismic Loads

As a pivotal node in both urban and rural power grids, the box-type substation not only serves the functions of power conversion and distribution but also need to provide structural support and environmental adaptability. However, deficiencies in strength, stiffness, or vibration characteristics may lead to vibration and noise issues, and extreme environmental changes can pose risks of structural damage. This study aims to verify and optimize the seismic resistance and environmental adaptability of box-type substations through finite element simulation methods. Using SOLIDWORKS, a three-dimensional model of the box-type substation was constructed, and static and dynamic analyses were conducted using Ansys Workbench to comprehensively evaluate the dynamic response of the box-type substation under wind, snow loads, and seismic action. Through iterative simulations and a comparison of multiple design solutions, the structural optimization of the substation was achieved. The optimized structure balances strength and stiffness, significantly reducing the weight of the substation body, with the wall thickness reduced by 60%. Additionally, the phenomenon of stress concentration on the side walls was eliminated, ensuring that the equivalent stress is below the material yield strength. This research provides methods and empirical results for enhancing the performance and reliability of box-type substations under seismic conditions, confirming the feasibility of a lightweight design, while ensuring structural safety.

Effect of Elevated Acetabular Cup on Contact and Failure Analysis in Hip Implants for Different Microseparations and Cup Inclinations Under Routine Gait Activities Using In Silico Approach.

The acetabular cup design plays a critical role in reducing contact stress between femur head acetabular cup. Many studies used ellipsoidal and spheroidal geometry in acetabular cup design to effectively reduce contact stress. The present study focuses on elevated acetabular cup rim with round corner design to reduce contact stress with round corner geometry. The cobalt chromium femur head and cup are considered for finite element (FE) model of hip resurfacing. The gait loads of routine activities of humans like normal walking, stair ascending and descending and sitting down and getting up gait activities are applied to the developed 3D FE model. Five microseparations of 0.5, 1, 1.5, 2 and 2.5mm are considered in the present study. The acetabular cup inclination angle considered for this study are 35°, 45°, 55°, 65° and 75°. The contact stress and von Mises stress plot for each gait activities under these microseparations are analyzed for betterment of longevity of implants. Overall elevated cup rim design helped in reducing contact stress to a greater extent than conventional cup with different geometries. Also, the predicted von Mises stress for all the parameters considered in the current study are well within the yield strength of CoCr material. Therefore, elevated cup rim could be used as a better alternative to spline and, ellipsoidal and circular geometries of cup.

Electromagnetic Design Optimization Integrated with Mechanical Stress Analysis of PM-Assisted Synchronous Reluctance Machine Topologies Enabled with a Blend of Magnets

Permanent Magnet-Assisted Synchronous Reluctance Machines (PMASynRM) provide a low-cost alternative to Surface PM Machines due to the use of relatively lower grades of rare-earth (RE) or RE-free magnets, as the performance degradation due to weaker magnets is compensated by the presence of reluctance torque. However, the weaker magnets suffer from a high risk of demagnetization, leading to unreliable motor operation. Using a blend of RE and RE-free magnets has the potential to overcome this issue. This paper proposes to blend different grades of various rare-earth (RE) and rare-earth-free (RE-free) magnets in six different combinations and utilizes them in two-layer and three-layer U-shaped PMASynRM topologies with both eight-pole and six-pole variations. The rotor of the various designs is then optimized using a differential evolution (DE) based optimization algorithm to obtain low-cost designs with reduced RE magnet volume and minimum demagnetization risk. The optimization of each design is also integrated with the evaluation of mechanical stresses in the rotor laminations so as to maintain the stresses below the material yield strength. Furthermore, the various performance metrics, such as toque–speed/power–speed characteristics, demagnetization, and efficiency maps, are evaluated for each of the optimized and mechanically feasible designs. A quantitative comparison of the various optimized designs is also obtained to highlight the various trade-offs. The results indicate the feasibility of meeting the baseline torque requirement across the entire speed range, even with a 100% reduction in RE magnet volume and less than 5% demagnetization risk, while achieving a cost reduction exceeding 50%. Moreover, the two-layer, eight-pole designs exhibit relatively higher performance, whereas the three-layer, eight-pole designs are found to be the most economical option.

Multi-scale simulation of Mo–Ag laminated metal matrix composites with Mo–Ag diffusion layer and parallel gap resistance welding in solar cells

Thus far, Mo/Ag laminated metal matrix composites (LMMCs) have been widely used as interconnectors in solar cells. In order to enhance the connection strength between Mo–Ag LMMCs and solar cells, a multi-scale simulation technique (MSM) was utilised to simulate the parallel gap resistance welding (PGRW) process. This method involved molecular dynamics (MD) simulation and the finite element method (FEM). The structure of the Mo–Ag diffusion layer was examined by high-resolution transmission electron microscopy (HRTEM), which revealed a thickness of around 5 nm. It exhibited a wedge-shaped configuration that augmented the bonding between Mo and Ag. The characteristics of the Mo–Ag diffusion layer were computed using molecular dynamics (MD), which has a substantial influence on the properties of the interconnectors. The FEM model was provided with these characteristics, and a total of nine sets of orthogonal simulation experiments were devised. The findings indicate that when a voltage of 0.5 V is applied, the distance between the electrodes is 0.15 mm, and the pressure on the electrodes is 8.89 N, the temperature at the interface of the workpiece can reach 940 °C. Furthermore, the internal stress (90 MPa) remains below the material's yield strength (430 MPa). In addition, based on the specifications of nine sets of orthogonal trials, the interconnectors were welded to the solar cells, and further 45° tensile tests were performed on the resulting joints. According to the simulation, the connection strength can achieve a maximum value of 558 gf (5.47 N) using the optimal parameters. Meanwhile, the findings from electron backscatter diffraction (EBSD) revealed that the primary process involved in the connection mechanism of PGRW is the mutual diffusion and recrystallization that occur due to electrode pressure and resistance heat.

Comparative Analysis of Piston Rings Made with Aluminum Titanium Carbide (AlTiC-75-2) and Carbon Cast Steel (AISI 1540) Materials Using Numerical Method

Aim: The main purpose of this study is to perform a comparative analysis of piston rings made with aluminum titanium carbide (AlTiC-75-2) and carbon cast steel (AISI 1540) materials using numerical method. Study Design: Numerical methods. Materials and Methods: The 3D piston rings were modelled with SOLIDWORDS version 2019 and imported to ANSYS 2020 RI environment for simulation and analysis. Results: The study revealed that AISI 1540 and AlTiC-75-2 had maximum deformations of 1.0356 mm and 1.0773 mm, respectively. Also, when the equivalent elastic strains of the piston rings were compared, it was revealed that, the maximum and minimum elastic strain of the AlTiC-75-2 piston was 4.8826e-3 and 2.2581e-5, respectively, whiles the maximum and minimum elastic strain of AISI 1540 was 2.1878e-5 and 2.1878e-5 respectively. Numerical results further showed that AISI 1540 piston suffered the least elastic strain while the AlTiC piston ring endured more elastic strain. Furthermore, results showed that the maximum Von Mises stresses induced in AlTiC-75-2 and AISI 1540 piston rings were 915.2 MPa and 911.27 MPa, respectively, which implies that stresses induced in both rings were beneath the compressive yield strengths of the individual materials, therefore both rings could withstand the load imposed. Conclusion: Result shows that the AISI 1540 ring has high minimum value than AlTiC which makes it more suitable material in terms of failure as against AlTiC-75-2 with a low minimum safety factor of 0.094187 as against 0.10182 for carbon cast steel. The study therefore recommends that AlTiC-75-2 should be considered as one of the most suitable materials for piston ring design.

Coupling effects of multiple strengthening mechanisms in spheroidal microstructure eutectic high-entropy alloys

The yield strength of metallic materials is commonly estimated using linear superposition methods, but this method has limited adaptability to new materials. The mapping relationship between input and output in machine learning methods is difficult to quantify. This study employs a rapid screening method to identify the key strengthening mechanisms that influence the yield strength of typical homogeneous and heterogeneous metallic materials. A non-linear physical neural information network model is developed to describe the yield strength of heterogeneous structures, capturing the main parameters contributing to yield strength from selected physical quantity data. By considering the non-linear strengthening mechanisms arising from interactions among multiple strengthening mechanisms in heterogeneous metal structures, the microstructure and mechanical properties of eutectic high-entropy alloys are optimized through warm rolling and short-time annealing. By inducing microstructural spheroidization and introducing nanoscale precipitates, significant coupling effects of multiple strengthening mechanisms are achieved for eutectic high-entropy alloys. As a result, the yield strength increases by approximately 2.5 times, while plasticity remains nearly unchanged. Transmission electron microscopy, scanning electron microscopy, and electron backscatter diffraction observations provide evidence for the sources of these coupling effects. This study offers guidance for accelerating material design and exploring the physical relationship between microstructure and mechanical properties.

Study on the static and dynamic mechanical properties and constitutive models of 3D printed PLA and PLA-Cu materials

The failure of mechanical properties in 3D printed polylactic acid (PLA) for many functional applications has made exploring ways for improving these properties essential; the use of copper powder for producing a composite material known as PLA-Cu is one of these ways. The mechanical responses of both PLA and PLA-Cu under both static and dynamic loading were studied using a universal testing machine and a split Hopkinson pressure bar apparatus, respectively. This experimental study helped to develop a constitutive model for each material according to their mechanical behavior. However, PLA-Cu, affected by ‘impact embrittlement,’ indicates a purely linear elastic behavior during dynamic conditions. Addition of copper powder increases the yield strength of the composite material significantly as compared to pure PLA, with both materials being strain rate sensitive as they change from static to dynamic states. The calibration of the Johnson-Cook constitutive model with the inclusion of the Cowper-Symonds strain rate term for these materials promises useful information for numerical models, improving the predictive models on their behavior under different loading scenarios.

Dynamic Contact Characteristics Analysis of Heavy-duty Track Rollers

As an important component of the crawler walking device, the track roller needs to withstand strong impact and is prone to failure, which can lead to serious economic losses. This paper focuses on the track roller of the spreader as the research subject and investigates the dynamic contact characteristics between the track roller and the track plate. Using RecurDyn software, a virtual prototype model of the crawler walking device is established to analyze the variation in a vertical dynamic load of the track roller under different working conditions. Simultaneously, a finite element model of the contact between the track roller and the track plate is developed using Ansys Workbench, and its accuracy is verified using Hertz contact theory. Finally, the study discusses various influencing factors on the contact characteristics, including load, curvature of the contacting bodies, and material yield strength. The results indicate that the track rollers experience the highest dynamic load when climbing a slope, reaching a maximum load of 1191.44 kN. Moreover, the maximum contact stress is 1750.4 MPa, and the maximum Mises stress is 921.34 MPa during this operation. Importantly, when the load reaches 1218 kN, the maximum Mises stress of the track roller is 930.2 MPa, which may lead to roller failure after prolonged use. These findings provide valuable insights for the design and optimization of heavy-duty track rollers and offer significant assistance for various tracked vehicles.

Relation of craze to crack length during slow crack growth phenomena in high‐density polyethylene

AbstractThe craze‐crack mechanism occurring in high‐density polyethylene (HDPE) causing slow crack growth and environmental stress cracking is investigated in detail with respect to the relation of crack length and the related craze zone. This is essential for the understanding of the resulting features of the formed fracture surface and their interpretation in the context of the transition from crack propagation to ductile shear deformation. It turns out that an already formed craze zone does not inevitably result in formation of a propagating crack, but could also undergo ductile failure. For the examination, the full notch creep test (FNCT) was employed with a subsequent advanced fracture surface analysis that was performed using various imaging techniques: light microscopy, laser scanning microscopy, scanning electron microscopy, and X‐ray micro computed tomography scan. FNCT specimens were progressively damaged for increasing durations under standard test conditions applying Arkopal, the standard surfactant solution, and biodiesel as test media were used to analyze the stepwise growth of cracks and crazes. From considerations based on well‐established fracture mechanics approaches, a theoretical correlation between the length of the actual crack and the length of the preceding craze zone was established that could be evidenced and affirmed by FNCT fracture surface analysis. Moreover, the yield strength of a HDPE material exposed to a certain medium as detected by a classic tensile test was found to be the crucial value of true stress to induce the transition from crack propagation due to the craze‐crack mechanism to shear deformation during FNCT measurements.Highlights Progress of crack formation in high‐density polyethylene is analyzed by different imaging techniques Determined growth rates depend on distinction between craze zone and crack The ratio of the present crack to the anteceding craze zone is validated theoretically The transition from crack propagation to ductile shear deformation is identified An already formed craze zone may still fail by ductile mechanisms

Influence of shear yield strength of rail material on the shakedown limit in shakedown map

Rail materials with different shear yield strengths can exhibit different rolling contact fatigue (RCF) damage response during cyclic contact loading. The objective of this work is to achieve the actual shakedown limits in the shakedown map for rail materials with different shear yield strengths through RCF simulation tests of wheel-rail, and to investigate the relationship between the shear yield strength (ke) and the shakedown limit. Rolling-sliding tests were performed to investigate the RCF damage states of three types of rail materials with different shear yield strengths. Then, according to the differences of RCF damage states for each rail material and the method of nonlinear curve fitting, the actual shakedown limits for three types of rail materials were obtained. The actual shakedown limits for the three types of rail materials were lower than the original one in the classical shakedown map. With an increase in the shear yield strength (ke) of the rail material, the actual shakedown limit is reduced. Moreover, a relationship emerged which allowed a simple method to be proposed to obtain the actual shakedown limit based on the shear yield strength. The changing process and differences in the impact of different shear stress levels on the microstructural damage transformation of rail materials from the perspective of contact mechanics have been discussed. The behavior of severe accumulation of residual stresses during cyclic loading and more likely initiation of microcracks are the main reasons why rail materials with a higher shear yield strength (ke) under great contact loads are more prone to developing RCF crack damages. That is, the shakedown limit for the material with a higher shear yield strength (ke) is much lower. In view of the application of the shakedown map in the evaluation and prediction for RCF damage of rail materials with different shear yield strengths, different shakedown limits should be applied to different rail materials when analyzing their likely performance.

Calculation Of Minimum Shaft Bearing Diameter Of ORC Turbine-Generator 100 kW And Analysis Using Finite Element Method

This study aims to analyze the strength of a turbine-generator shaft and determine the minimum diameter of the shaft using the Finite Element Method (FEM). The research problem is to ensure the shaft's strength and durability, considering the high rotation speed of the hermetic turbine generator. The methodology involves using Finite Element Method and comparing the calculated minimum diameter with the physical properties of stainless steel 420. The research design includes modeling the shaft using SolidWorks and conducting FEM analysis using Ansys Mechanical Structure. The results show that the maximum von Mises stress is 50.6 MPa, which is below the material's yield strength of 345 MPa. The deformation of the shaft is minimal, and the natural frequencies indicate no critical speed below the rated RPM of the turbine-generator. The implications of this study are that the analyzed shaft design is safe and meets the strength requirements for the turbine-generator.

Thermal and structural analysis of TCABR vacuum vessel during baking process

TCABR is a small-sized tokamak located at the University of São Paulo, in Brazil. It is planned to undergo an extensive upgrade, which includes a baking system. However, this tokamak wasn't designed considering baking as a possible wall conditioning technique. This paper analyzes whether a baking system with ohmic heating could in principle be installed on TCABR, considering the thermal stresses that it might produce on the vacuum vessel. An analytical steady-state heat transfer model was used to estimate the heat fluxes required to reach a target temperature of 200 °C. Thermal and structural transient finite element method models were developed using ANSYS Workbench®. The temperature distribution was used to calculate the thermal stresses, also considering the effects of gravity and vacuum pressure. The stresses produced in the vacuum vessel by baking were below the limit defined by the ASME stress code, but the graphite tiles’ support rails reached stress values above their material's yield strength. The resulting temperature distribution was not uniform, with some regions far from the 200 °C target. A redesign of the baking system will be required to reach a more uniform temperature field and avoid stresses above yield strength for some components.

Seismic behavior and shear capacity prediction of coupled concrete‐filled multicellular steel tube composite shear walls

AbstractIn this paper, a coupled concrete‐filled multicellular steel tube composite shear walls structure (CCSSW) is proposed. A finite element model (FEM) is developed to investigate the seismic behavior of CCSSW, and the model was validated by the tests. The effects of four parameters including axial compression ratio (ACR) on the hysteretic behavior of the CCSSW were studied. Then, a theoretical model for predicting the ultimate shear capacity (USC) of CCSSW was established. The results show that the failure mode of coupled walls exchanged from flexural failure to flexural‐shear failure with increasing the ACR, and it is recommended that the ACR should less than 0.6 to ensure the ductility requirement. To better realize the function of the first line of defense of steel coupling beam (SCB), following recommendations are concluded: the span‐to‐depth ratio range of SCB is 4.0–6.0, the wall stiffness ratio is 2.4–4.7, and low yield strength material should be used for SCB. The maximum error on USC between FEM results and theoretical results is 12.8%, and most of them are less than 10%, indicating the effectiveness of the proposed theoretical model.