Strain-hardening Exponent Research Articles

Influence of printing orientation on power-law hardening and ductile damage parameters for 3D-printed SS316L steel: experimental and FEA approach

In the present investigation, the selective laser melting (SLM) technique has been utilized for the 3-dimensional printing (tensile test specimens) of SS316L steel powder at 00 (horizontal) and 900 (vertical) angles. Further, an experimental and finite element analysis approach has been made to analyse the effect of printed orientation or direction on the Hollomon power law parameters (strain hardening exponent (n) and strength coefficient (K)) and ductile damage parameters (fracture strain (εf), stress triaxiality (η) and strain rate ( ε ̇ )). The influence of printing orientation on plastic deformation behavior has also been analysed. The results revealed that 00 angle 3D-printed specimens exhibited 11.05%, 21.97% and 9.50% more yield strength, tensile strength and elongation than 900 angle 3D-printed tensile test specimens. Further, the strain hardening exponent (n) and strength coefficient (K) (Hollomon power law hardening model parameters) for 00 angle 3D-printed specimens are 35.80% and 32.47% more than the 900 angle 3D-printed tensile test specimens respectively. The fracture strain for 00 angle 3D-printed specimens is 37.82% less than the 900 angle 3D-printed tensile test specimens. The percentage difference between FEA and experimental results is less than 5% which shows the good prediction capability of estimated Hollomon power law parameters and ductile damage model parameters with developed FEA model for 00 and 900 3D printed specimens.

Study on the Mechanical Response Behavior of X80 Pipeline Steel Welding Structure under Tensile Stress

Abstract The weld joint is composed of the weld area and the heat-affected area. The heterogeneity of the organizational structure will lead to local strain mismatch and affect its mechanical properties. This paper studies the strain distribution characteristics of the weld area and the heat-affected area under tensile stress, and reveals the respective strain response mechanism of the two regions. It is found that the weld area has lower yield strength and hardness, greater uniform elongation and strain hardening index. The plastic strain of the weld joint under tensile stress is highly heterogeneous, and the strain response mechanism is mainly based on the processing hardening effect. The strain response of the heat-affected area is weak and is affected by grain-oriented hardening. The research results provide a theoretical basis and experimental basis for the design of pipeline steel welding process and the safety evaluation under plastic deformation conditions.

Multifractal Characteristics of Gain Structures: A Universal Law of Polycrystalline Strain-Hardening Behaviors

The quantitative relationship between material microstructures, such as grain distributions, and the nonlinear strain-hardening behaviors of polycrystalline metals has not yet been completely understood. This study finds that the grain correlation dimension of polycrystals D is universally equal to the reciprocal of the strain-hardening exponent by experimental research and fractal geometry analysis. From a geometric perspective, the correlation dimension of grains is consistent with that of the equivalent plastic strain field, which represents the correlation dimension of the material manifold. According to the definition of the Hausdorff measure and Ludwik constitutive model, the strain-hardening exponent represents the exponent derived from the Dth root of the measure relationship. This universal law indicates that the strain-hardening behaviors are fractal geometrized and that the strain-hardening exponent represents a geometrical parameter reflecting the multifractal characteristics of grain structures. This conclusion can enhance the comprehension of the relationship between microstructure and mechanical properties of materials and highlights the importance of designing materials with non-uniform grain distributions to achieve desired hardening properties.

Local shear fracture properties in heat-affected zone of resistance spot-welded advanced high-strength steel

In the process of resistance spot welding of advanced high-strength steel (AHSS), the development of heat-affected zones (HAZs) considerably modifies the mechanical properties of the weld region. However, the limited reporting in the study of shear behavior in the HAZ hinders the accurate prediction of joint fracture and failure behavior. This study focused on the shear fracture behavior of resistance spot-welded AHSS. Given the limited extent of the HAZ, a miniature shear test was designed and shear fracture tests were conducted on JSC590, JSC980, and JSC1180. These tests facilitated the acquisition and compilation of data regarding the shear mechanical properties of diverse steel grades and their respective HAZs. A hardness-based empirical model for the strength coefficient and the strain-hardening exponent in Hollomon's law was introduced, and this model was subsequently integrated into finite element method calculations. The accuracy of the model was validated by shear strength reproductions, exhibiting errors within the range of 5.4%–13.5% and the averaged error was less than 10%. Further analyses confirmed that stress triaxiality at critical positions varied from 0 to 0.33, indicative of shear-dominant stress conditions. Moreover, the evolution of stress states revealed a notable association between the fracture surfaces across different stress states and steel grades. These findings fill the gap regarding the shear behavior of localized HAZs and expand the understanding of their mechanical behavior under various stress states. It will contribute to accurate fracture prediction by stress triaxiality based fracture criteria, such as Modified Mohr-Coulomb (MMC) model, applied to AHSS.

A Numerical Modelling of V-Bending

In the study, a sheet metal is bent to analyze the punch force, Von Misses stresses and plastic strains on the metal for friction and non-friction cases. The 2-D v-bending forming is modelled in program. Model includes a die, a punch and a blank. Solid mechanics physics interface has been used in program. The analyze has been run with friction and non-friction cases for different strain-hardening exponents and sheet metal thicknesses. The sheet lengths and widths are 60 mm. Thickness of sheet metal is varied between 1.0 to 3.0 mm. The strain hardening exponent has been altered from 0.1 to 0.5. It is computed that the punch force has been increased as thickness of sheet metal and strain hardening exponent decreases. The achieved maximum punch force is at values of 1.12x105 N, 3.75x105 N and 4.05x105 N for thickness of 1.0-mm, 2.0-mm and 3.0-mm respectively when strain hardening exponent is 0.3. Also, as the strain hardening exponent increases from 0.1 to 0.5, the maximum punch force lowers from 2.03x105 N to 8.08x104 N for 1 mm thickness at friction case. Moreover, the maximum punch force reached up to 9.13x104 N for 1 mm thick sheet metal at non-friction case when the strain hardening exponent is 0.1. It is concluded that the maximum Von Misses stress has been calculated at the tip of sheet metal.

Elastic–plastic strain conversion of a thin-plate miniaturized tensile test based on crosshead measurement via an analytical method

This paper underscores the significance of accurate strain measurement in unconventional miniature thin plate specimen (MTPS) tests and proposes a data conversion approach involving an equivalent gauge length (EGL) and a gauge factor (GF). An analytical method is presented to determine EGL for converting elastic–plastic strain data based on the total cross-head deformation of the specimen. The GF values obtained, accounting for various initial geometries of the sample and strain-hardening exponents of the test material, show that, by neglecting elastic elongation, GF only depends on specimen geometries and strain-hardening exponents of the test material, being independent of the applied load, strain rate, and temperature. Validation through Finite Element (FE) simulation and miniaturized tensile tests (MTTs) with digital image correlation (DIC) has demonstrated the sound accuracy of the data conversion method, with the maximum GF errors below 4.82% for selected geometries. The proposed method holds significant implications for the design of MTPS, ductility correction, and comparative analysis of mechanical properties across samples with different dimensions.

SiC nanoparticles additions to squeeze-cast Mg-5.0Al-2.0Ca-0.3Mn alloy: An evaluation of microstructure and mechanical properties

The influences of the SiC nanoparticles (SiCnp) content on the microstructural modification and mechanical properties of the squeeze-cast Mg-5.0Al-2.0Ca-0.3Mn (AXM520) alloy have been investigated. The concentrations of the SiCnp are varied from 0.5 to 3.0 (wt%), and the nanocomposites (NCs) are abbreviated as NC0.5SiC, NC1.0SiC, NC2.0SiC and NC3.0SiC. The as-cast microstructures of the AXM520 alloy and NCs consist of an α-Mg phase, a eutectic of α-Mg and (Mg,Al)2Ca (C36), and an Al8Mn5 phase. Additionally, the SiC phase is also present in the NCs. The continuous network of the C36 phase is fragmented and becomes discontinuous as the content of the SiCnp increases in the NCs. All the NCs exhibit superior tensile and compressive properties than the AXM520 alloy. The NC2.0SiC exhibits the best tensile properties among the NCs employed. The YS of the NCs improves with the increase in the SiCnp content up to 3.0 (wt%). The UTS and %El of the NCs increase up to 2.0SiCnp (wt%), and beyond that, the same declines owing to the agglomeration of the nanoparticles. The discontinuous network of the C36 phase in the NCs inhibits crack propagation, leading to their improved %El. All the NCs exhibit higher strain-hardening exponent (n) and strain-hardening rate (SHR) compared to the AXM520 alloy. The superior ‘n’ and SHR exhibited by the NCs were attributed to the grain refinement and dislocations generation. The strengthening from CTE mismatch contributes the most to the overall strengthening of the NCs. The ‘Zhang and Chen’ model is modified by introducing an agglomeration factor, and the predicted YS of the NCs matches pretty well with the experimentally obtained values.

Unraveling the impacts of fermentation methods on the protein structural, foaming and air-water interfacial properties of buckwheat steamed bread dough liquor

Liquid lamella has crucial impacts on stabilizing gas cells and buckwheat steamed bread (BSB) quality due to the high fiber content and lack of gluten protein in buckwheat. The liquid lamella was collected by ultracentrifugation as the dough liquor (DL). This study explored the composition, foaming and interfacial properties of DL from lactic acid bacteria (LAB), yeast, LAB and yeast cooperate (LAB-yeast), and chemical acidified and yeast (CA-yeast) fermented buckwheat dough, as well as the unfermented buckwheat dough. Compared with the unfermented dough, the DL yield of LAB-yeast, yeast, and CA-yeast fermented dough decreased by 4.09%, 3.93%, and 7.67%, respectively. The protein molecular weight and surface hydrophobicity of DL were dramatically reduced by LAB, LAB-yeast, and CA-yeast fermentation as compared to unfermented DL. Among all DL samples, the unfermented and yeast DL showed the highest protein surface hydrophobicity and surface activity, resulting in the greatest foam stability. The protein in CA-yeast DL displayed the fastest interface diffusion because its DL had the highest amount of low molecular weight protein, the lowest viscosity and protein content. Compared with the unfermented dough, the LAB and LAB-yeast fermentation decreased, while the CA-yeast fermentation increased the strain hardening index (SHI) of the dough. This enhanced strain hardening behavior contributed to a decrease in the average cell area and an increase in cell density, making the crumb structure of CA-yeast fermented BSB homogeneous and dense.

The investigation on microstructure evolution and mechanical behavior of extruded Mg-1.5Al-xLa-Mn (x=0.5, 1, 2wt%) alloys

In this study, the microstructure evolution and mechanical behaviour of Mg-1.5Al-xwt%La-Mn (ALaM-x) (x = 0.5, 1, and 2) alloys with low-cost were investigated. Microstructure analysis of the cast alloys revealed that the Al11La3 was preferentially precipitated, followed by Al2La, and finally Mg12La, as the Al/La ratio decreased. Nonetheless, the main precipitated phase in the alloy was Al11La3 phase, and it gradually coarsened and the content increased, with the increase of La content. The fine rod-like Al11La3 was broken and refined after extrusion, while the coarse Al11La3 was not completely broken, and aggregated unevenly within Mg matrix. As a result, the grain size of the alloys gradually increased, and the strength gradually decreased. When adding 0.5 wt%La, compared with pure Mg, the ALaM-0.5 alloy exhibited finer grain microstructure with an average size of 1.83 μm and a grain refinement rate of 90%; the corresponding tensile yield strength (TYS) and ultimate tensile strength (UTS) are 262.5±3.0 MPa and 275.0±2.4 MPa, with an increase rate of 124.7% and 52.1%, respectively. The calculation and analysis of strengthening mechanism showed that the high strength of the alloy was mainly attributed to fine-grained strengthening with an accounting for up to 42%. Besides, the inverse relationship between the square root of the reciprocal of grain size (d−1/2) and strain hardening exponents (n) was found in this study, and the precipitates were found to delay the weakening trend of strain hardening capacity with decreasing grain size.

Preservation conditions of hot work hardening in die steel with regulated austenitic transformation during exploitation

Die steels with regulated austenitic transformation during exploitation (RATE steels) are a new class of tungsten-free steels for hot forming at operating temperatures up to 750 – 800 °C. High durability of the pressing tool and its long service life are ensured by the ability of these steels to preservation of hot work hardening. This circumstance distinguishes RATE steels from traditional alloy steels, which are prone to softening at high temperatures. However, the temperature ranges for the preservation of hot hardening in RATE steels was not systematically studied, which makes it difficult to use a pressing tool more efficiently. In this paper, we study the mechanical behavior of RATE die steel during thermo-mechanical treatment in a wide temperature range, including the stage of preliminary deformation at lower temperatures and the stage of main deformation at higher temperatures corresponding to operating temperatures of the pressing tool. The thermo-mechanical treatment was carried out using a hardening-deformation dilatometer DIL 805 A/D according to the compression mode. We obtained the true stress-strain curves and determined the mechanical characteristics and strain hardening index. Size of the former austenite grain in the steel structure after thermo-mechanical treatment was measured. The temperature-force conditions for enhancing hot hardening or stabilizing hot hardening, or softening, were established. It is shown that the hardening achieved at the stage of preliminary deformation at a temperature of 450 °C is enhanced at the stage of main deformation at temperatures in the range from 550 to 800 °C, while in this temperature range the tendency to increase hot hardening is weakened.

Further investigation of two-parameter J-A estimation for clamped SET specimens

Based on the J-A two-parameter characterization, this paper presents a systematic study of the crack-tip constraint for clamped single-edge notched tension (SET) specimens. Extensive finite element analyses (FEA) are conducted to obtain the A solutions for the modified boundary layer (MBL) model and the SET specimen. The material used in the analysis is the Ramberg-Osgood power-law material, with varying yield stress and strain hardening exponents. Based on previous studies, the T-stress-related A solutions for MBL problems under small-scale yielding conditions are obtained from FEA results, and the A solutions for the SET specimen are found to scale with normalized applied load under large-scale yielding conditions. By summing up these two solutions, the total A for the SET specimen can be estimated, covering the entire range from small-scale to large-scale yielding conditions. A key geometry factor is introduced as a function of material properties, crack depths and applied load. Some fitting equations are proposed in this estimation method, and a Python program is developed to quickly and accurately obtain the total A for the SET specimen. The results of the present study show good agreement for all the simulated cases. The proposed solutions of constraint parameter A can be used to establish the constraint-corrected J-R curve for SET specimens.

Microstructure characteristics and strain hardening behaviour of Ti17 linear friction welded joints

This study investigated the microstructure variations in Ti17 linear friction welded joints and evaluated the effect of strain rate and post weld heat treatment on the strain hardening behaviour. The welded zone of the as-welded joints consists of equiaxed β grains, while the prior-β grains in the thermal mechanical affected zone are severely deformed. After heat treatment, fine needle-like α S precipitates dispersed in the β matrix strengthen the tensile properties. The fracture mechanism transforms from brittle to ductile. The strain hardening capacity and exponent are negatively correlated with strain rate. At higher strain rates, the strain rate sensitivity increases during the initial stage of deformation.

Constitutive relations of nanoscale hydration products present in engineered cementitious composites from machine learning assisted experimental nanoindentation

In this work, a method to evaluate the stress-strain properties (at nano-scale) of constitutive phases present in the hydration cement matrix is presented. Using an experimental grid nanoindentation using Berkovich indenter, the constituent phases i.e., Low Density Calcium Silicate Hydrate (LD CSH), High Density Calcium Silicate Hydrate (HD CSH) and clinkers are indented upon during different points of Ordinary Portland Cement (OPC) paste hydration. Further, this study is conducted on four other cement pastes: OPC +20% fly ash, OPC +40% fly ash, OPC +0.5% nanosilica and OPC +1% nanosilica. Using experimental grid nanoindentation technique results in a large dataset depending upon the size of the gird. Three different machine learning algorithms including K-means, Gaussian mixture model (GMM) clustering and, support vector machine (SVM) have been implemented. The developed stress-strain evaluation method has allowed to ascertain the constitutive relations as yield stresses of 354 MPa for LD CSH, 393 MPa for HD CSH and 4340 MPa for clinkers, yield strains of 1.8 × 10−2 for LD CSH, 1.1 × 10−2 for HD CSH and 3.7 × 10−2 for clinkers; ultimate stresses of 371 MPa for LD CSH, 424 MPa for HD CSH and 6085 MPa for clinkers, ultimate strains of 2 × 10−2 for LD CSH, 1.4 × 10−2 for HD CSH and 4.4 × 10−2 for clinkers; and strain hardening exponents of 0.85 for LD CSH, 0.72 for HD CSH and 2.1 for clinkers. Elastic modulus, hardness and the stress-strain values obtained from the load vs. displacement curves are used for the clustering analysis and compared with deconvolution results. These properties have been used to test the feasibility of application of machine learning algorithms to classify the grid nanoindentation data. It was found that the machine learning algorithms were indeed capable of clustering the data obtained from experimental grid nanoindentation. This study presents a novel method to evaluate stress-strain properties of the constituent phases present in the cement microstructure and application of machine learning in the field of material characterisation using nanoindentation technique.

Analysis on the Key Parameters to Predict Flow Stress during Ausforming in a High-Carbon Bainitic Steel

Since flow stress is an important parameter in the processing and application of metallic materials, it is necessary to trace the flow stress during austenite deformation. Thermal compression deformation of austenite in a high-strength bainitic steel was conducted using a Gleeble-3500 thermo-mechanical simulator, within the deformation temperature range of 400 °C~900 °C. By analyzing the stress–strain curves and strain-hardening exponent, the effects of strain hardening and dynamic recovery on the dislocation density of the material during the thermal processing were considered in the present work. Based on the general form of the Kocks–Mecking–Estrin (KME) model, the effects of deformation temperature and strain on the key parameters of the model were clarified. Differing from other work which commonly terms m (strain rate sensitivity exponent) and k2 (dimensionless parameters for dynamic recovery) as constants, the current models consider the quantitative relationship between key parameters and deformation temperature and strain. The results show that m is an exponential function related to temperature and strain, which decreases with the increase in strain. Meanwhile, k2 is a temperature-dependent polynomial function that increases as the deformation temperature increases. Finally, a modified constitutive KME model was proposed to predict the austenitic plastic stress with strain. Using established m-ε and k2-T models, the predicted curves are in good agreement with the experimental measurements.

An improved analytic model for extracting plastic mechanical property of matrix in hot-extruded in-situ TiB2/2024 composite based on Berkovich indentation experimental results

Due to the strengthening mechanisms mainly contributed to dispersed nano TiB2 particles, plastic mechanical property of Al matrix in hot-extruded in-situ TiB2/2024 composite, referring to yield strength (YS) and strain hardening exponent (SHE), are considerably improved compared with 2024 Al alloy. In addition, the plastic mechanical property of Al matrix cannot be obtained directly through traditional uniaxial tensile tests. After carrying out dimensional analysis and FE simulations, an improved analytical model with no need of characteristic stress/strain is proposed found on existing model, to extract plastic mechanical property parameters of Al matrix based on sufficient Berkovich indentation experimental results. The indentation experiments carried out using the custom method “G-Series Basic Hardness, Modulus, Tip Cal, Load Control” were implemented in case of four different maximum indentation loads to get indentation load-depth curves (ILDCs) of Al matrix, where the corresponding morphologies of residual indents were obtained by SEM observation. With these experimental results as input, the YS and SHE of Al matrix can be calculated by utilizing the proposed analytic model. To verify the effectiveness of proposed improved model, a unit-cell FE model with same particle volume fraction as the macroscopic composite is established and analyzed, and the calculated results are in good agreement with the uniaxial tensile test results.

Modeling of acoustic field dependent tensile property for metal materials

Acoustic softening is a physical phenomenon with important application significance. Whether for ultrasonic-assisted metal processing or metal materials serving in the acoustic field environment, quantitative characterization of the impact of the acoustic field on material strength have important technological and engineering values. However, there are few reports on theoretical characterization models that can reveal the evolution of metal material strength with acoustic field. Based on the Force-Heat Equivalence Energy Density Principle, considering the equivalent relationship between acoustic energy and elastic deformation energy, the acoustic field dependent yield strength model of metal materials without fitting parameters is developed; considering the equivalent relationship between acoustic energy and elastoplastic strain energy, the acoustic field dependent ultimate tensile strength model considering strain hardening behavior is developed, and only the fitting parameters introduced in the constitutive equation are included in this model. The predicted results of both models are in good agreement with the experimental results. The quantitative effects of strength coefficient and strain hardening index on ultimate tensile strength under different acoustic fields is analyzed. The critical acoustic energy density is proposed to describe the point of abrupt change of ultimate tensile strength. Further, quantitative comparison of the influence on strain hardening effect and yield strength in different acoustic fields is conducted to explain the rapid decline of ultimate tensile strength. Finally, based on the above conclusions, some useful suggestions for safe use of metal materials under acoustic fields and ultrasonic-assisted machining are put forward.

Optimization of fiber aspect ratio for 90 MPa strain-hardening geopolymer composites (SHGC) with a tensile strain capacity over 7.5%

This study developed high-strength strain-hardening geopolymer composites (SHGC) containing 2% (by volume) polyethylene (PE) fibers. A high-strength geopolymer matrix with a compressive strength of over 100 MPa was achieved using liquid crystal display glass powder and ground granulated blast furnace slag. To determine the optimum aspect ratio of PE fibers, five different types of PE fibers with aspect ratios ranging from 300 to 900 were considered. The average bond strength of PE fibers in the high-strength geopolymer matrix was 1.55 MPa, similar to that of high-strength cement matrices. The PE fibers with higher aspect ratios were more effective for improving the tensile performance of high-strength SHGC than those with lower aspect ratios, and a robust strain-hardening characteristic with saturated micro-crack patterns was obtained when the fiber aspect ratio exceeded 600. The energy-based pseudo strain-hardening index (Jb′/Jtip) was found to be 25.3 at a fiber aspect ratio of 600, and it increased to 104.3 with the increase in the fiber aspect ratio up to 900. The best tensile performance—tensile strength of 5.73 MPa, strain capacity of 7.58%, and strain energy density of 309.6 kJ/m3—was achieved in the high-strength SHGC reinforced with PE fibers having an aspect ratio of 900.

Complex Interdependency of Microstructure, Mechanical Properties, Fatigue Resistance, and Residual Stress of Austenitic Stainless Steels AISI 304L.

Stainless steels are important in various industries due to their unique properties and durable life cycle. However, with increasing demands for prolonged life cycles, better mechanical properties, and improved residual stresses, new treatment techniques, such as deep cryogenic treatment (DCT), are on the rise to further push the improvement in stainless steels. This study focuses on the effect of DCT on austenitic stainless steel AISI 304L, while also considering the influence of solution annealing temperature on DCT effectiveness. Both aspects are assessed through the research of microstructure, selected mechanical properties (hardness, fracture and impact toughness, compressive and tensile strength, strain-hardening exponent, and fatigue resistance), and residual stresses by comparing the DCT state with conventionally treated counterparts. The results indicate the complex interdependency of investigated microstructural characteristics and residual stress states, which is the main reason for induced changes in mechanical properties. The results show both the significant and insignificant effects of DCT on individual properties of AISI 304L. Overall, solution annealing at a higher temperature (1080 °C) showed more prominent results in combination with DCT, which can be utilized for different manufacturing procedures of austenitic stainless steels for various applications.

Mechanical behavior of nanorubber reinforced epoxy over a wide strain rate loading

Nanorubber/epoxy composites containing 0, 2, 6 and 10 ​wt% nanorubber are subjected to uniaxial compression over a wide range of strain rate from 8 ​× ​10−4 s−1 to ∼2 ​× ​104 s−1. Unexpectedly, their strain rate sensitivity and strain hardening index increase with increasing nanorubber content. Potential mechanisms are proposed based on numerical simulations using a unit cell model. An increase in the strain rate sensitivity with increasing nanorubber content results from the fact that the nanorubber becomes less incompressible at high strain, generating a higher hydro-static pressure. Adiabatic shear localization starts to occur in the epoxy under a strain rate of 22,000 s−1 when the strain exceeds 0.35. The presence of nanorubber in the epoxy reduces adiabatic shear localization by preventing it from propagating.

A novel flat indentation test method for obtaining stress–strain relationships of metallic materials based on energy density equivalence

For power-law hardening metallic materials under flat cylindrical indentation loading conditions, a theoretical model was derived to describe the relationships among the stress and strain of the equivalent material representative volume element, load, displacement, and diameter of the indenter based on energy density equivalence. Subsequently, a novel flat indentation test method was developed such that the stress vs. strain data points of a material with a known elastic modulus could be directly calculated by utilizing the collected load vs. displacement data points. Numerical verifications were performed on 64 elastoplastic materials with various combinations of elastic moduli, yield strengths, and strain hardening exponents. In addition, flat indentation tests were carried out on 12 metallic materials. The results showed that the stress–strain curves obtained by the proposed method were consistent with those pre-input in finite element analysis and those obtained from uniaxial tensile tests. Furthermore, the proof strength and tensile strength of the experimental materials were obtained according to the predicted Hollomon law parameters, and the relative errors between the predicted and standard test results were mostly within 3%.