For Finite Element Research Articles

Numerical prediction on the fatigue debonding behaviour in a complex bi-material interface: A case study on wrapped composite joints

Debonding is one of the most critical failure modes for bonded joints under fatigue loads. Numerical prediction on the fatigue debonding behaviour of bonded interfaces with complex geometry still remains a problem. This paper proposes a numerical methodology based on fracture mechanics to predict crack growth in a complex bi-material interface and illustrates the prediction procedure by a case study on wrapped composite joints. Interface coupon tests provide the fatigue crack growth properties at the composite-to-steel interface used as inputs for finite element (FE) modelling. The FE model is calibrated against fatigue tests of small scale wrapped composite joints with different steel surface roughness subject to different load levels. A sensitivity analysis is conducted to investigate the influence of key modelling parameters. The calibrated model is validated against fatigue tests on upscaled joints. Good agreements are shown between the test and modelling results in terms of crack growth and stiffness degradation, demonstrating the potential of the proposed numerical methodology for predicting fatigue debonding behaviour of complex bi-material interfaces.

Multiscale Parametrization Of a Friction Model For Metal Cutting Using Contact Mechanics, Atomistic Simulations, And Experiments

In this study, we developed and parametrized a friction model for finite element (FE) cutting simulations of AISI4140 steel, combining experimental data and numerical simulations at various scales. Given the severe thermomechanical loads during cutting, parametrization of friction models based on analogous experiments has been proven difficult, such that the cutting process itself is often used for calibration. Instead, our model is based on the real area of contact between rough surfaces and the stress required to shear adhesive micro contacts. We utilized microtextured cutting tools and their negative imprint on chips to orient chip and tool surfaces, enabling the determination of a combined surface roughness. This effective roughness was then applied in contact mechanics calculations using a penetration hardness model informed by indentation hardness measurements. Consistent with Bowden and Tabor theory, we observed that the fractional contact area increased linearly with the applied normal load, and the effective roughness remained insensitive to cutting fluid application. Additionally, we calculated the required shear stress as a function of normal load using DFT-based molecular dynamics simulations for a tribofilm formed at the interface, with its composition inferred from ex-situ XPS depth profiling of the cutting tools. Our friction model demonstrated good agreement with experimental results in two-dimensional FE chip forming simulations of orthogonal cutting processes, evaluated by means of cutting force, passive force, and contact length prediction. This work presents a proof of concept for a physics-based approach to calibrate constitutive models in metal cutting, potentially advancing the use of multiscale and multiphysical simulations in machining.Graphical abstract

Finite element modeling and modal testing of a wind turbine lattice tower component with interference pin connections

Fatigue failures at fastener holes in structures are undesirable as they can lead to catastrophic mechanical failures. Interference pins create interference fits with joined components to reduce stresses around fastener holes and extend the fatigue life of a structure. In this research, a novel method for finite element (FE) modeling of interference pin connections in a wind turbine lattice tower component was developed. The installation of interference pins was modeled using a two-stage process that causes local stiffness changes in joined members of the component. The local stiffness changes were accounted for in the FE model by using cylinders to represent the interference pins. An experimental setup, including a three-dimensional (3D) scanning laser Doppler vibrometer (SLDV) and a mirror, was used to measure out-of-plane and in-plane natural frequencies and mode shapes of the component. Ten out-of-plane modes and one in-plane mode from the FE model are compared with the experimental results to validate the accuracy of the FE modeling approach. The maximum percent difference between the theoretical and experimental natural frequencies of the component is 3.21%, and the modal assurance criterion (MAC) values between the theoretical and experimental mode shapes are 0.92 or greater, showing good agreement between the theoretical and experimental modal parameters of the component.

Soft tissue material properties based on human abdominal in vivo macro-indenter measurements

Simulations of human-technology interaction in the context of product development require comprehensive knowledge of biomechanical in vivo behavior. To obtain this knowledge for the abdomen, we measured the continuous mechanical responses of the abdominal soft tissue of ten healthy participants in different lying positions anteriorly, laterally, and posteriorly under local compression depths of up to 30 mm. An experimental setup consisting of a mechatronic indenter with hemispherical tip and two time-of-flight (ToF) sensors for optical 3D displacement measurement of the surface was developed for this purpose. To account for the impact of muscle tone, experiments were conducted with both controlled activation and relaxation of the trunk muscles. Surface electromyography (sEMG) was used to monitor muscle activation levels. The obtained data sets comprise the continuous force-displacement data of six abdominal measurement regions, each synchronized with the local surface displacements resulting from the macro-indentation, and the bipolar sEMG signals at three key trunk muscles. We used inverse finite element analysis (FEA), to derive sets of nonlinear material parameters that numerically approximate the experimentally determined soft tissue behaviors. The physiological standard values obtained for all participants after data processing served as reference data. The mean stiffness of the abdomen was significantly different when the trunk muscles were activated or relaxed. No significant differences were found between the anterior-lateral measurement regions, with exception of those centered on the linea alba and centered on the muscle belly of the rectus abdominis below the intertubercular plane. The shapes and areas of deformation of the skin depended on the region and muscle activity. Using the hyperelastic Ogden model, we identified unique material parameter sets for all regions. Our findings confirmed that, in addition to the indenter force-displacement data, knowledge about tissue deformation is necessary to reliably determine unique material parameter sets using inverse FEA. The presented results can be used for finite element (FE) models of the abdomen, for example, in the context of orthopedic or biomedical product developments.

Finite element model updating and response prediction of a frame structure based on optimal sensor placement

This paper proposes an approach for finite element (FE) model updating and response prediction of frame structures based on optimal sensor placement (OSP), which integrates sensor placement optimization, mode expansion, and model updating techniques. Firstly, sensor optimization layout and modal testing analysis are conducted on a bolted laboratory frame structure. The covariance-driven stochastic subspace identification (SSI-COV) method identifies the real-world structure’s natural frequencies, modal damping, and mode shapes. Secondly, the complete mode shapes are expanded using the measured incomplete modal data from the limited number of sensors. Thirdly, a multi-objective function based on frequency and mode shapes is established to adjust the parameters of the FE model. This ensures that the updated model accurately represents the dynamic properties of the actual structure within a specific frequency range. Finally, the Rayleigh damping of the frame structure is estimated, and the damping matrix is assembled to enhance the accuracy of dynamic response prediction in the updated model. By comparing the response prediction results of the updated FE model with and without considering the updated damping effects to the measurement data of the real-world structure, it is demonstrated that the proposed method considering updated damping effects can more effectively predict the structural response.

On thermal and strain-rate dependences of polymethacrylimide (PMI) foam materials

Polymethacrylimide (PMI) foams exhibit great potentials in engineering applications thanks to its outstanding lightweight and superior mechanical properties. However, the temperature and loading rate can greatly affect its mechanical behaviors, which are the key factors in analysis and design of the PMI foam structures for practical applications. Unfortunately, there is lack of fundamental data and constitutive models available concerning the elastic-plastic properties of the PMI foam in various stress states at different ambient temperatures and different strain rates. Therefore, this study aims to fill this knowledge gap by generating basic experimental data and providing a generic modeling solution for PMI foam materials and structures. To better reflect the actual service conditions in practice, different stress states are considered under different temperatures and strain rates. The cyclic loads are applied to characterize the actual mechanical responses of the PMI foam where the initial and subsequent yield surfaces were calibrated and analyzed. Following the experimental results, the elasticity, plasticity, viscosity and damage of the PMI foam are investigated thoroughly, especially for the initial and subsequent yielding behaviors. Further, the thermal and strain rate dependent constitutive models are established and calibrated based on the in-house experimental data for finite element (FE) modeling. A novel damage model is proposed to replicate the phenomenon of the stiffness degradation in compression. It is found that accurate predictions on the mechanical responses of PMI foam can be achieved under different temperatures and different strain rates. This study is anticipated to provide fundamental experimental data and effective constitutive models of PMI foams for real engineering applications, such as lightweight design of sandwich structures under some harsh conditions.

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.

Finite element model updating and damage detection using strain-based modal data in the Bayesian framework

This paper proposes a novel methodology for Bayesian model updating and damage detection of a structural system using strain-based modal data. The strain-based modal data are assumed to consist of the posterior statistics of natural frequencies and strain mode shapes corresponding to measured strains from a classically damped system. The dynamic strain-based equation of the motion is formulated utilizing the energy functional of the structural system and the strain displacement relation. The state variables in the considered strain-based formulation consist of the strains and the elemental rigid body displacements. The methodology is developed by incorporating strain-based formulation into the Bayesian framework for Finite Element (FE) model updating. Besides, additional uncertain parameters in the form of system strain-based modal parameters are introduced in the eigenvalue equation to avoid mode-matching. The model reduction technique is utilized to eliminate the rigid body displacements and the strains that are not measured. Metropolis-Hastings (MH) within Gibbs sampling is proposed to simulate samples from the posterior Probability Density Function (PDF) of the model parameters of the FE model. The effectiveness of the proposed methodology is demonstrated using simulated examples. An experimental study is also conducted to validate the proposed methodology.

Biomechanical Finite Element Simulation of Cochlear Implant Surgical Robot Drilling Through Direct Cochlear Access

AbstractRobotic drilling through direct cochlear access for cochlear implantation (CI) is currently a prominent area in the field of CI surgery. However, the safety of drilling remains an issue due to the limited space within the facial recess. Estimation and control of drilling force are critical to prevent drill‐bit breakthrough, excessive heat generation, and mechanical damage to the facial nerve. The bone drilling process presents a favorable application scenario for finite element (FE) analysis. In this study, a 3D FE model of temporal bone drilling is established for the first time to predict the drilling force. The self‐developed CI surgical robot validates these findings through experimental drilling. The experimental results show that the drilling process can be divided into three stages, and the corresponding force curve can be divided into six zones. The overall trend of temporal bone drilling is two force peaks and one trough in the middle. The drilling force is positively correlated with the feed rate. The FE results found to be in good agreement with the experimental results. Numerical simulation can be utilized as an invaluable tool for assisting in predicting the position of drilling tools and optimizing drilling parameters in the future.

Development of patient-tailored preoperative assessment of percutaneous vertebroplasty.

Percutaneous vertebroplasty (PVP), a minimally invasive surgery technique, has become the common treatment for osteoporotic vertebral compression fractures (OVCF). The complications of PVP will lead to severe damage to spinal neuro systems due to bone cement leakage. A patient tailored preoperative assessment approach was developed to reduce the risks of complications in this study. The porcine OVCF model was fabricated to mimic the patient vertebral fracture in vitro using decalcification process. The 3D reconstructed model based on the imagological examination data acquired from the porcine vertebral bone was implemented for finite element (FE) simulation. The vertebral body with bone cement injected was scanned using CT for comparison with the finite element simulation results. This study showed a practical method for predicting the flow of bone cement in OVCF, which enabled the surgeons to evaluate the bone cement flow during preoperative assessment to reduce the cement leakage risks.

The influence of microstructural characteristics and cell wall material properties on the mechanical behaviors of different tissues of sorghum stems

Sorghum stems comprise different tissue components, i.e., rind, pith, and vascular bundles in the rind and pith regions, of different cell morphologies and cell wall characteristics. The overall responses of stems to mechanical loadings depend on the responses of these tissues themselves. Investigating how each tissue deforms to various loading conditions will inform us of the failure mechanisms in sorghum stems when exposed to wind loadings, which can guide the development of lodging-resistant variants. To this end, numerical analyses were implemented to investigate the effects of cell morphologies and cell wall properties on the overall mechanical responses of the above four tissues under tension and compression. Microstructures of different tissues were constructed from microscopic images of the tissues using computer-aided design (CAD), which were then used for finite element (FE) analyses. Shell finite elements were used to model the cell walls, and the classical lamination model was used to determine the overall mechanical responses of cell walls having different fiber composite arrangements. The results from the numerical analyses helped explain how the loading (boundary) conditions, the cell microstructures, the mechanical properties of cell walls of different tissues, the cell wall thickness, the microfibril angle (MFA) of fiber composites of the cell walls, and the turgor pressure affected the overall mechanical responses of the tissues. Tissue stiffening or softening behaviors were attributed to different microstructural deformations, i.e., local or global buckling of cell walls, cell collapse, densifications of cells, or reorientation and rearrangement of cells. The mechanical properties and thickness of cell walls only affected the stiffness and load-bearing ability of the tissues. The turgor pressure affected the compressive responses but its effect on tensile responses was negligible. The MFA had a significant influence on the stiffness and load-bearing ability when the tissues were loaded along their longitudinal axis, but it had an insignificant effect on loading in the transverse direction. Tissues with smaller cell sizes and denser cells were stronger and stiffer than those with larger cell sizes. The numerical simulations also revealed that rind and rind vascular bundles were stiffer and had higher load-bearing ability than pith and pith vascular bundles.

Numerical Investigation of the Evolving Inelastic Deformation Path of a Solder Ball Joint under Various Loading Conditions

Solder joints of ball grid arrays (BGA) have been widely used to connect electronic components to printed circuit boards (PCBs) and are often subjected to mechanical stress. Several studies have been conducted on the mechanical reliability of solder joints. While these studies have been useful in the industry, detailed studies on how the inelastic deformation path of the solder ball joints evolves under specific loading conditions have not been sufficiently reported. This study aims to understand how the inelastic deformation path evolves when a solder joint is subjected to a constant external force by utilizing the theory of mechanics. It has also been found that the mechanical failure is strongly influenced by the evolution history of the deformation modes in materials. For this study, an elastoplastic constitutive model and a ductile fracture criterion were implemented into the vectorized user-defined material (VUMAT) subroutine of the ABAQUS program for finite element (FE) analysis. With the model, the evolution of the inelastic deformation path of a single solder ball under different loading conditions was numerically analyzed. Three loadings (shear, compression, and bending) were chosen as the basic loading conditions. In addition, combinations of the basic loadings resulted in three dual loadings and one complex loading. The simulation results showed that the shear and bending caused the fracture for both single and dual loadings, but when combined with compression, the fracture was suppressed. The results indicate that fracture is not solely determined by the magnitude of equivalent plastic strain but also by the evolution of inelastic deformation mode. This research offers an improved understanding of the significance of the inelastic deformation path and fracture.

Structural response of monolithic and multi-stacked AA2014-T6 sheet specimens subjected to shock loading

Experimental and numerical investigations of the shock response of AA2014-T6 sheets are presented in the current study. A double-stage shock loading apparatus is utilized for loading the simply supported specimens under the shock loading. The experiments are performed on two different sheet thicknesses i.e., 1 mm and 2 mm. The spatial out-of-plane displacement of the specimens is obtained using 3D digital image correlation (DIC) technique. ABAQUS/Explicit is utilized for finite element (FE) modelling and simulating the shock loading event. A modified loading function is incorporated in the FE model to approximate the change in the specimen loading area and shock loading magnitude for the deformable specimens. The experimentally and numerically obtained out-of-plane displacement of the specimens are compared and agreement between both is quantified using Russell error technique. A series of experiments are conducted to investigate the effect of change in shock loading magnitude on the deformation phenomenon and corresponding energy dissipation. Alloy sheet of 2 mm thickness is observed to be better shock resistant than 1 mm sheet as the plastic dissipation energy per unit mass is higher for 2 mm thick sheet. Additionally, the shock behaviour of layered targets is also investigated for effective thicknesses of 2 mm and 3 mm. The performance of monolithic sheet of 2 mm is observed to be better than layered configuration of (1 + 1) mm. For the effective thickness of 3 mm, the order of decreasing shock performance is observed as (2 + 1) mm, (1 + 2) mm, and (1 + 1 + 1) mm.

Finite element analysis of RC moment-resisting frames to assess effective slab width; a parametric study

In reinforced concrete (RC) moment-resisting frames (MRFs) with cast-in-situ slabs, the slab action as tension flange during lateral loading enhances the flexural capacity of beams in negative moments. This enhancement may lead to strong beam-weak column unfavorable failure mode in these structures. Field observations of RC MRFs during strong ground motion indicated that the effective slab width values considered by the seismic provisions of the design codes are not adequate to guarantee the achievement of the design method of weak beam-strong column. An accurate estimation of effective slab width needs to assess factors such as geometrical characteristics of connection, continuity of models, and imposed story drift level. A 3D spatial two-story RC MRF was developed using finite element analysis (FEA) to explore the effect of mentioned factors on effective slab width. For finite element (FE) modeling of RC MRF, the concrete damaged plasticity (CDP) model is applied. The CDP model parameters are defined using a mesh-independent methodology introduced in the literature. Comparing the FEA results and results obtained from three half-scale RC MRFs, tested under reversed cyclic loading conditions showed an excellent correlation. The results predicted by the FE model in terms of lateral load–displacement response, reinforcement yielding sequence, crack patterns, and failure modes had a considerable agreement with test observations. The validated FE model was used to develop the other models to conduct a parametric study in the next step. Geometric parameters studied in this paper through numerical modeling were longitudinal and transverse beam length and height, and cross-sectional column dimension. Results of the parametric study showed that the effect of the ratio of transverse beam length to height is significantly more than the ratio of longitudinal beam length to height. The trend of effective slab width versus story drift depends on connection geometry, especially the ratio of transverse beam length to transverse beam height. Finally, an equation was driven to predict the effective slab width using linear regression analysis.

Non-intrusive hybrid scheme for multiscale heat transfer: Thermal runaway in a battery pack

Accurate analytical and numerical modeling of multiscale systems is a daunting task. The need to properly resolve spatial and temporal scales spanning multiple orders of magnitude pushes the limits of both our theoretical models as well as our computational capabilities. Rigorous upscaling techniques enable efficient computation while bounding/tracking errors and helping to make informed cost-accuracy tradeoffs. The biggest challenges arise when the applicability conditions of upscaled models break down. Here, we present a non-intrusive two-way (iterative bottom-up top-down) coupled hybrid model, applied to thermal runaway in battery packs, that combines fine-scale and upscaled equations in the same numerical simulation to achieve predictive accuracy while limiting computational costs. First, we develop two methods with different orders of accuracy to enforce continuity at the coupling boundary. Then, we derive weak (i.e., variational) formulations of the fine-scale and upscaled governing equations for finite element (FE) discretization and numerical implementation in FEniCS. We demonstrate that hybrid simulations can accurately predict the average temperature fields within error bounds determined a priori by homogenization theory. Finally, we demonstrate the computational efficiency of the hybrid algorithm against fine-scale simulations.

A priori compression of convolutional neural networks for wave simulators

Convolutional neural networks are now seeing widespread use in a variety of fields, including image classification, facial and object recognition, medical imaging analysis, and many more. In addition, there are applications such as physics-informed simulators in which accurate forecasts in real time with a minimal lag are required. The present neural network designs include millions of parameters, which makes it difficult to install such complex models on devices that have limited memory. Compression techniques might be able to resolve these issues by decreasing the size of CNN models that are created by reducing the number of parameters that contribute to the complexity of the models. We propose a compressed tensor format of convolutional layer, a priori, before the training of the neural network. 3-way kernels or 2-way kernels in convolutional layers are replaced by one-way fiters. The overfitting phenomena will be reduced also. The time needed to make predictions or time required for training using the original Convolutional Neural Networks model would be cut significantly if there were fewer parameters to deal with. In this paper we present a method of a priori compressing convolutional neural networks for finite element (FE) predictions of physical data. Afterwards we validate our a priori compressed models on physical data from a FE model solving a 2D wave equation. We show that the proposed convolutional compression technique achieves equivalent performance in the prediction error as classical convolutional layers with fewer trainable parameters(around 20%) and lower memory footprint.

EVALUATING MESOSCALE STRAIN LIMIT FOR TRANSVERSE PLATE-TO-RHS X JOINTS

Recently, mesoscale strain limit has been introduced for finite element (FE) analysis and FE-based design of welded steel tubular joints. The strain limit criterion appears to be useful particularly for the joints made of high strength steels, considering their lower ductility and higher propensity to fracture failure when subjected to tensile strains. While the latest revised draft of ISO 14346 recommended the use of 5% principal strain as the strain limit for all kinds of tubular joints, a previous study by the authors has demonstrated that a limit lower than 5% principal strain may be required for welded plate connections. In this study, the load-deformation relationship and fracture failure of transverse plate-to-RHS X-joints are investigated to evaluate appropriate strain limit for such type of joints. Based on test and test-validated FE analysis with a high strength steel of grade 700 (i.e., nominal yield stress of 700 MPa), it is suggested that more conservative strain limit should be applied to transverse plate-to-RHS X-joints.

Numerical Analysis of Reinforced Concrete Circular Columns Strengthening With CFRP under Concentric and Eccentric Loadings

The purpose of this study is to explore the numerical behavior of circular RC short columns with different degrees of confinement with CFRP (0%, 25%, 50%, and 100%) wraps under concentric and eccentric loading. The numerical analysis carried out by using an improved concrete plastic-damage model (CDPM) implemented in ABAQUS software for finite element (FE) analysis. The FE model simulated a total of twenty-four numerical specimens. The findings were matched to published experimental test results in the literature. The findings of the FE model and the experimental data were good similar. As a consequence, the model was found to be valid. The numerical results shows that as load eccentricity increased, the load carrying capacity of columns decreased for unconfined specimens, whereas the decline in strength for confined specimens becomes limited as the degrees of confinement ratio increased. In addition, increasing the CFRP confinement ratio improves the column's load-bearing capability at the same load eccentricity.

Modeling of masonry structures using a new 3D cohesive interface material model considering dilatancy softening

This study presents a new 3D multi-yield surfaces material model for masonry mortar joints, which can be used with interface elements for finite element (FE) modeling of masonry structures to capture various failure mechanisms. This model is featured with (1) two hyperbolic yield surfaces, capable of capturing various failure modes of mortar joints, including tensile cracking, shear sliding, and compressive crushing, (2) an unassociated flow rule to capture the ‘dilatancy’ phenomenon in the mortar joints, and (3) the dilatancy softening and variation of mode II fracture energy under different normal stress levels. An implicit Euler backward integration algorithm, combined with local-global Newton-Raphson (NR) solver, is adopted to achieve the predictor-corrector return mapping in the numerical formulation. The error-based auto-adaptive sub-stepping algorithm is employed to achieve the robustness and efficiency in the integration procedure. The developed model is implemented in the general-purpose FE software ABAQUS with the specialized capability of modeling masonry structures. The developed model is validated through three brick-mortar-brick assemblages and three un-reinforced masonry (URM) walls under in-plane (IP) loading or out-of-plane (OOP) loading. The importance of appropriate modeling of dilatancy on simulating the IP and OOP behavior of URM walls is highlighted. The validation results show that the developed constitutive model is capable of modeling masonry structures at various scales with improved accuracy by considering dilatancy softening.

Stress evolution mechanisms under different SSPT-related effects during laser welding

In this study, a thermal-metallurgical-mechanical (TMM) model was developed for finite element (FE) analysis in laser welding of ultra-high-strength steel (UHSS). The solid-state phase transformation (SSPT) model of austenization was improved by introducing a heating rate-dependent coefficient. Seven cases considering different SSPT-related effects (Case 1–5) and different austenization models (Case 5–7) were considered for the simulation of welding stress to study the stress evolution mechanism during welding. The effects include changes in the yield strength, coefficient of thermal expansion, volume strain, and plastic strain, all of which are induced by the SSPT. By comparing the predicted and measured partial austenitized zone (PAZ), it was found the proposed model had good accuracy for the ultra-high heating rates during laser welding. The predicted transverse/longitudinal welding stresses were also in good agreement with the measurements. The results show that each effect can dramatically change the evolution process and the final magnitude and sign of stress. For example, the SSPT-induced plastic strain always results in a plastic strain having the same sign as the stress, and, in return, gives rise to a decrease in the magnitude of stress. In addition, the SSPT-related effects are weakened when the austenization model underestimates the austenite fraction, leading to a larger error in the predicted stress.