For Finite Element Analysis Research Articles

ViscoNet: A lightweight FEA surrogate model for polymer nanocomposites viscoelastic response prediction

Polymer-based nanocomposites (PNCs) are formed by dispersing nanoparticles (NPs) within a polymer matrix, which creates polymer interphase regions that drive property enhancement. However, data-driven PNC design is challenging due to limited data. To address the challenge, we present ViscoNet, a surrogate model for finite element analysis (FEA) simulations of PNC viscoelastic (VE) response. ViscoNet leverages pre-training and finetuning to accelerate predicting VE response of a new PNC system. By predicting the entire VE response, ViscoNet surpasses previous scalar-based surrogate models for FEA simulation, offering better fidelity and efficiency. We explore ViscoNet's effectiveness through generalization tasks, both within thermoplastics and from thermoplastics to thermosets, reporting a mean absolute percentage error (MAPE) of < 5 % for rubbery modulus and < 1 % for glassy modulus in all cases and 1.22 % on tan δ peak height prediction. With only 500 FEA simulations for finetuning, ViscoNet can generate over 20k VE responses within 2 min with 1 CPU, compared to 97 days with 4 CPUs via FEA simulations.

Comprehensive Study of EPDM Rubber Properties: Temperature-Dependent Stiffness, Tensile Behavior and FEA Calibration

Abstract This work examines the temperature-dependent stiffness of Ethylene Propylene Diene Monomer (EPDM) rubber using tensile testing and Dynamic Mechanical Analysis (DMA). Additionally, it provides an appropriate model for Finite Element Analysis (FEA). The tensile tests indicate that EPDM has high rigidity and minimal elongation at −40°C, intermediate characteristics at 23°C, and a decrease in stiffness with rising temperature, up to 80°C. Nevertheless, a sudden rise in rigidity is seen at a temperature of 125°C, which may be ascribed to the strengthening influence of carbon black. The DMA findings confirm this pattern, demonstrating an upward trend in storage modulus and stiffness as temperature increases. At the same time, tan delta and loss modulus fall, suggesting a reduction in viscoelastic damping. The calibration of the Finite Element Analysis (FEA) model, using the Arruda-Boyce, Yeoh 3D, and Mooney-Rivlin 5-parameter models, determines that the Arruda-Boyce model is the most precise in accurately replicating the experimental data. The results indicate that the improved resistance to heat and increased rigidity of EPDM at high temperatures are affected by its material composition. However, more investigation is required to have a comprehensive understanding of the underlying processes.

Lesion Size Location Dependency on Maximum Pressure in Osteochondral Defects: Experiments and Finite-Element Analysis.

Osteochondral defects (OCDs) in the knee joint have significant clinical implications, particularly regarding contact pressures and pressure distribution. Understanding how these factors are influenced by defect size and location is crucial for developing effective therapeutic strategies. The purpose of this study was to investigate the impact of defect size and location on contact pressures and pressure distribution in the knee joint. It was hypothesized that an increase in defect size would result in elevated contact pressures and alterations in pressure distribution, with specific variations related to defect location. Descriptive laboratory study. The study utilized 6 cadaveric knees, including the patella and fibula, subjected to controlled compressive loading for measuring contact pressures. Simultaneously, computed tomography-based models were created for finite-element analysis (FEA) to investigate the impact of varying defect sizes and locations on contact pressures and pressure distribution in the knee joint, excluding the patellofemoral joint. The study employed analysis of variance to assess contact pressure and defect size association. Comparison between medial and lateral femoral condyles at full extension and 30° flexion angle was performed, followed by post hoc testing. Fisher exact test analyzed peak pressure point location and defect size, categorizing them into medial and lateral. An increase in defect size corresponded with heightened contact pressures on both medial and lateral femoral condyles at full extension (P = .013 for medial and P = .024 for lateral). However, this correlation did not yield significant differences at 30° of flexion (P = .674 for medial and P = .333 for lateral). During mechanical testing, the highest pressures occurred near 5 mm defect dimensions. FEAs showed a significant increase in pressure and circumferential-edge stress with 7-mm defects. Peak contact pressure points shifted laterally with more significant defects. Our study demonstrated the impact of defect size, location, and alignment on knee joint contact pressures. Intervening promptly with defects exceeding 3 mm is crucial, as significant stress levels manifest beyond this threshold. Significant increases in contact pressures were noted with larger defect sizes, particularly between 3 and 10 mm at full extension. Peak pressure points shifted with defect size increments, and alignment variations showed minimal stress variation at 30° compared with 0°. FEA validated increasing contact pressures up to 7 mm defect size, beyond which pressures stabilized or slightly decreased. A concentrated pressure distribution on the medial side was observed. These findings inform our understanding of the biomechanical implications of OCDs. In the field of sports medicine, this research offers valuable insights to clinicians and researchers, elucidating key factors influencing knee joint health and the potential consequences of OCDs.

Aircraft Structural Assessments in Data-Limited Environments: A Validated FE Method

Aircraft operators often modify aircraft configurations, install new equipment, and alter airframes to accommodate this equipment, leading to operations in flight envelopes different from original design profile. These modifications necessitate airframe structural assessments, which typically require comprehensive aircraft design data, often unavailable to operators. This study aims to develop and validate a practical method for finite element analysis (FEA) of aircraft structures in the absence of this detailed design data. Focusing on a case study involving structural analysis of an aircraft wing, this study presents assumptions and idealizations used to develop 2.5D finite element (FE) model of the wing. Fidelity of this model is established by comparing FE analysis results with experimental data. Key validation metrics include reaction forces, load distribution at wing-fuselage attachments, and deformation at reference points on the wing under design load. Comparison between FE analysis and experimental results is carried out to substantiates accuracy of these geometric simplifications and idealizations of load-carrying behaviour of structural members. Therefore, practicality of these idealizations in absence of design data is demonstrated. This study offers a novel approach for structural assessments of aircraft without relying on proprietary design data. The validated method enhances capability of aircraft operators to perform effective structural analyses, thereby extending service life of aircraft with continued airworthiness.

Numerical and Experimental Validation for Connecting Nature with Architecture by Mimicking Cranium into a Shell Roof

This study focuses on a structural element bio-mimicked from the human cranium (HC) into a shell element. As the HC is effective in resisting intracranial pressure developed by the brain, a water tank was considered to use a bio-mimicked shape of a shell as a roof. An optimized numerical model was validated experimentally and compared with a conventional specimen. The structural behavior of the bio-mimicked specimen is similar and performs more efficiently than the conventional specimen in capacity ratio, crack formation, and load-carrying capacity. Methodology followed: A Computed Tomography (CT) scan of the HC was obtained in Digital Imaging and Communications in Medicine (DICOM) format for finite element analysis (FEA). From the geometric parameters of the HC, the radius of the curvature-to-thickness ratio was derived for the shell. The span and thickness of the shell under two criteria were considered. The spherical and circular shell behaviors were found to be similar to those of the HC, whereas the elliptical shell behavior was not. We studied the shape effect of the HC with the conventional slab and found that the HC shape has an impact on the behavior and is the most efficient. A bio-mimicked mono column was considered as a supporting column for the water tank and analyzed. Overall, adopting this bio-mimicking of the HC into the shell roof connects nature with sustainable architecture.

Biomechanical Analysis of Orthodontic Miniscrew-Assisted Rapid Palatal Expansion on Dental and Bone Tissues: A Finite-Element Study

Abstract This study aims to delineate the biomechanical responses in both soft and hard tissues, alongside the interactions within the surrounding bone of a human skull subjected to clinical loadings generated by a miniscrew-assisted rapid palatal expansion (MARPE) device. Cone-beam computed tomography (CBCT) scans of a 20-year-old female skull were segmented. The skull bones were meticulously modeled to reconstruct a comprehensive three-dimensional (3D) model for finite-element analysis (FEA). A displacement of 0.125 mm was applied on each side (0.25 mm total) of the MARPE device to simulate one complete turn of the jackscrew. The outcomes revealed that the miniscrews experienced a maximum equivalent von Mises stress of 264.91 MPa. Notably, the separation of the midpalatal suture exhibited a quasi-parallel deformation with an average displacement of 0.247 mm and a standard deviation of 0.006,67 mm. The ratio of the rotational angle to the lateral displacement of the zygomaticomaxillary complex was 0.6436 degree/mm. No fracture of miniscrews was observed during the activation of one turn per day.

Finite element analysis of meniscus contact mechanical behavior based on kinematic simulation of abnormal gait

The meniscus plays a crucial role in the proper functioning of the knee joint, and when it becomes damaged, partial removal or replacement is necessary to restore proper function. Understanding the stress and deformation of the meniscus during various movements is essential for developing effective materials for meniscus repair. However, accurately estimating the contact mechanics of the knee joint can be challenging due to its complex shape and the dynamic changes it undergoes during movement. To address this issue, the open-source software SCONE can be used to establish a kinematics model that monitors the different states of the knee joint during human motion and obtains relevant gait kinematics data. To evaluate the stress and deformation of the meniscus during normal human movement, values of different states in the movement gait can be selected for finite element analysis (FEA) of the knee joint. This analysis enables researchers to assess changes in the meniscus. To evaluate meniscus damage, it is necessary to obtain changes in its mechanical behavior during abnormal movements. This information can serve as a reference for designing and optimizing the mechanical performance of materials used in meniscus repair and replacement.

Investigation on Fracture Behavior of Electroslag Welding Joint with High-Performance Steel

This study aimed to investigate fracture behavior of electroslag welding (ESW) joint with 590-N/mm2 class steel using numerical analysis, covering a range of material scales in the structural level. The extended Mohr–Coulomb (EMC) fracture criterion was employed for finite element analysis (FEA). Uniaxial tensile test and three-point bending test were conducted to analyze the fracture behavior from the material scale and calibrate the fracture criterion. The test specimens consisted of the base metal, heat-affected-zone metal, and welding metal obtained from an ESW joint with a 590 N/mm2 class steel. Subsequently, FEA was conducted for a biaxial tensile test to investigate fracture behavior at a structural scale and verify the feasibility and accuracy of the calibrated fracture criterion. The comparison between the results from the FEA and test suggests that the FEA based on the EMC fracture criterion can accurately predict fracture behavior but tends to overestimate the bearing capacity. Thereafter, the effect of axial force on column was quantitatively investigated. The results suggest that the existence of tensile axial force at column decreases the ductility of ESW joint and shifts the fracture locus from the welding metal to heat-affected zone. However, the force has minimal influence on the pop-in load. Finally, the feasibility of applying the current Japanese specifications designated for the 490 N/mm2 class steel for the 590 N/mm2 class steel was examined. The results indicate that the provision can serve as a safe and reliable guideline for the 590 N/mm2 class steel as well.

An experimental and numerical study on two-way RC slabs with openings strengthened by ferrocement technique

This study investigates the impact of creating a central square opening on reinforced concrete slabs and assesses the strengthening process using ferrocement layers. The investigated key parameters were the opening sizes, type, number, and extension length (outside the opening sides) of steel mesh layers used to strengthen the tested slabs. The experimental program included the preparation and testing of twelve two-way reinforced concrete slabs with identical dimensions, thickness, and reinforcement, but were different with respect to opening sizes and strengthening schemes. Four slabs acted as control specimens without strengthening; one was solid; the other three had different opening sizes; and the other eight slabs were strengthened using a ferrocement layer of 2 cm thickness applied on the bottom of the slab around the openings with various reinforcement schemes which included the number, type, and extension length (outside the opening) of steel mesh. All slabs were supported along the four sides with a clear span of 1 m in both directions and tested under four-point loading. The test results demonstrate that creating an opening in the slab decreases the ultimate load by 21.5 %, 31.9 %, and 40.7 % for opening dimensions (15, 25, and 35 cm), respectively. Using the ferrocement strengthening method helps to increase slabs’ flexural load-carrying capacities and reduce crack propagation from opening corners. The study found that strengthening specimens with opening sizes of 15, 25, and 35 cm increased their flexural load-carrying capacities by 26 %, 33 %, and 34 %, respectively. The expanded steel mesh type also resulted in a higher ultimate load by 6–7 % than the welded mesh type. When the length of the strengthening ferrocement layers was doubled, the ultimate load went up by 6–7 %. Increasing steel mesh layer numbers from 1 to 4 increased the ultimate load by 25 % to 40 % compared to the corresponding un-strengthened slab with an opening. The maximum load of a slab with an opening was achieved by applying a 2 cm thickness of ferrocement layer reinforced with expanded metal mesh, with extension lengths equal to the opening's length. The study utilizes commercial software ABAQUS for finite element analysis (FEA) to validate the experimental results, resulting in a great agreement between the analysis and the experimental findings.

Design of Two-Wheeler Hybrid Electric Vehicle using MATLAB-Simulink

Abstract: This report presents the design and structural analysis of a go-kart using PTC Creo for CAD modelling and ANSYS for finite element analysis (FEA). The aim is to develop a low-cost, comfortable, and durable go-kart with an optimized frame design. The study involves the application of design principles and advanced simulation tools to ensure the go-kart meets safety and performance standards. The best frame design was identified through iterative testing and analysis, focusing on weight distribution, material selection, and structural integrity. The objective of this work is to demonstrate the design procedure and good strength for a Roll cage. This project emphasizes on the practical and engineering applications of the subjects Vehicle Dynamics and Automotive Technology.

Study on the optimal elastic modulus of flexible blades for right heart assist device supporting patients with single-ventricle physiologies.

Patients with single-ventricle physiologies continue to experience insufficient circulatory power after undergoing palliative surgeries. This paper proposed a right heart assist device equipped with flexible blades to provide circulatory assistance for these patients. The optimal elastic modulus of the flexible blades was investigated through numerical simulation. A one-way fluid-structure interaction (FSI) simulation was employed to study the deformation of flexible blades during rotation and its impact on device performance. The process began with a computational fluid dynamics (CFD) simulation to calculate the blood pressure rise and the pressure on the blades' surface. Subsequently, these pressure data were exported for finite element analysis (FEA) to compute the deformation of the blades. The fluid domain was then recreated based on the deformed blades' shape. Iterative CFD and FEA simulations were performed until both the blood pressure rise and the blades' shape stabilized. The blood pressure rise, hemolysis risk, and thrombosis risk corresponding to blades with different elastic moduli were exhaustively evaluated to determine the optimal elastic modulus. Except for the case at 8,000 rpm with a blade elastic modulus of 40 MPa, the pressure rise associated with flexible blades within the studied range (rotational speeds of 4,000 rpm and 8,000 rpm, elastic modulus between 10 MPa and 200 MPa) was lower than that of rigid blades. It was observed that the pressure rise corresponding to flexible blades increased as the elastic modulus increased. Additionally, no significant difference was found in the hemolysis risk and thrombus risk between flexible blades of various elastic moduli and rigid blades. Except for one specific case, deformation of the flexible blades within the studied range led to a decrease in the impeller's functionality. Notably, rotational speed had a more significant impact on hemolysis risk and thrombus risk compared to blade deformation. After a comprehensive analysis of blade compressibility, blood pressure rise, hemolysis risk, and thrombus risk, the optimal elastic modulus for the flexible blades was determined to be between 40 MPa and 50 MPa.

Calibration of micromechanical fracture model parameters for Q355B steel and ER50–6 welds

To calibrate the micromechanical fracture model of Q355B steel and ER50–6 welds, 46 specimens of five types were subjected to monotonic tensile tests. The material constitutive model employed for finite element analysis (FEA) is determined by the Swift-Voce model, which leads to FEA results that closely align with the experimental test results. The parameters of the void growth model (VGM) and the stress-weighted damage model (SWDM) were calibrated, and the VUSDFLD user subroutine was written based on the two models to predict the fracture of each specimen. The prediction results show that the VGM model has good accuracy in the case of high-stress triaxiality. However, the prediction error of the VGM model is relatively large for shear specimens with low-stress triaxiality and significant changes in the Lode angle parameters. In contrast, the SWDM model with Lode angle parameters can predict the fracture of specimens under different stress states more accurately.

The mechanics of prestress and elastic recovery resulting from dimple formation in steel sheets: Comprehensive numerical and experimental studies

Residual stress is rarely considered as an initial condition for Finite Element Analysis (FEA), or used in the component design. A comprehensive numerical and experimental investigation into prestressed steel sheets is conducted. Residual stresses at specific locations were introduced into the steel sheets by dimple formation. FEA is used to simulate dynamic dimple forming of a mild steel disk due to a tool impact and detect the existence of prestress after dimple formation. A physical drop-hammer was used to form a range of dimple sizes in disks to experimentally validate the FEA predictions associated with dimple depth. Dimples were then created using a screw press and the prestress was measured by strain gauges beyond the zone of permanent out-of-plane deformation associated with a dimple. The experimental strain gauge measurements during dimple formation were found to be consistent with FEA predictions. The results demonstrated that the predicted and measured radial and tangentially projected stress components remain in steel sheets after forming a dimple. Furthermore, the predicted prestress was greater near to the dimple formation and occurred at higher magnitudes in the tangential direction than the radial direction. The highest prestress remaining in the disk was at the magnitude of the material’s ultimate tensile stress, predicted in the tangential direction at the edge of the dimple. The numerical and experimental results showed the three stages of prestress formation: the development of stresses during dimple formation, the elastic recovery after the dimple forming, and the final prestressed equilibrium state of the rimmed disk.

On the crashworthiness of aperiodic chiral mechanical metamaterials: design and modeling method

Chiral mechanical metamaterial has become topical in energy absorption for the unusual compression-to-twist deformation determined by the asymmetric chirality geometry of their microstructures. However, the insufficient research on the dynamic crash behavior with high nonlinearity and the lack of efficient design and modeling method have blocked the development of chiral mechanical metamaterials considering crashworthiness. In this work, the structure-property relationship of chiral mechanical metamaterials under medium-strain-rate impact was systematically investigated. We proposed an aperiodic framework considering additive manufacturing which enabled both the ordered and disordered chiral mechanical metamaterials utilizing a screw-theory-based assembly rule. The strut components had variable cross-sections and the joints were fillet-enhanced in order to improve the compressive performance. Meanwhile, the corresponding efficient modeling method for finite element analysis (FEA) was introduced. The constitutive relation, damage criteria, and damage revolution of the 316L stainless steel were established considering strain rate effect. Finally, the deformation mechanisms and energy absorbing capabilities of the proposed chiral mechanical metamaterials were demonstrated and discussed based on the mechanical behaviors and the proposed chirality indexes. The numerical results indicated that the proposed design and modeling method provided an effective paradigm for the crashworthiness design of light-weight materials and structures, facilitating the further applications in fields of automobile, civil engineering, aerospace, etc.

Fuzzy modeling and characterization of mechanical and biological properties of a selective laser melting shape: A comprehensive study

The bone scaffold is a porous structure that possesses suitable biological and mechanical properties similar to those of natural bone, thereby providing a suitable substrate for bone growth. The scaffold plays a temporary role in the bone repair process and is composed of degradable material that gradually degrades over time to enable new bone growth and replacement. The scaffolds are implanted using bone morphogenetics of transplanted bone-protein (BMP-7) and implanted subcutaneously to assess biological properties and tissue growth. This study demonstrates the ability to design and fabricate a titanium scaffold with a porous architecture using the Selective Laser Melting (SLM) method, employing two different geometries. The scaffolds' mechanical properties are assessed via a compression test, and the results are utilized for finite element analysis (FEA), predicting the designed metallic scaffold's optimal geometric shape and porosity percentage. The biological response of the scaffolds is evaluated via simulated body fluid (SBF) and phosphate buffer saline (PBS) analyses. The findings indicate that the 8-sided scaffold has superior mechanical and biological features compared to the circular and 6-sided geometries. To predict the scaffold's specifications before conducting the experiment, a fuzzy modeling system is used to model the effect of inputs such as weight percentage, elastic modulus, porosity, and Poisson ratio on the compressive strength output variable.

A novel explicit design method for complex thin-walled structures based on embedded solid moving morphable components

In this article, a novel explicit approach for designing complex thin-walled structures based on the Moving Morphable Component (MMC) method is proposed, which provides a unified framework to systematically address various design issues, including topology optimization, reinforced-rib layout optimization, and sandwich structure design problems. The complexity of thin-walled structures mainly comes from flexible geometries and the variation of thickness. On the one hand, the geometric complexity of thin-walled structures leads to the difficulty in automatically describing material distribution (e.g., reinforced ribs). On the other hand, thin-walled structures with different thicknesses require various hypotheses (e.g., Kirchhoff–Love shell theory and Reissner–Mindlin shell theory) to ensure the precision of structural responses. Whereas for cases that do not fit the shell hypothesis, the precision loss of response solutions is non-negligible in the optimization process since the accumulation of errors will cause entirely different designs. Hence, the current article proposes a novel embedded solid component to tackle these challenges. The geometric constraints that make the components fit to the curved thin-walled structure are whereby satisfied. Compared with traditional strategies, the proposed method is free from the limit of shell assumptions of structural analysis and can achieve optimized designs with clear load transmission paths at the cost of few design variables and degrees of freedom for finite element analysis (FEA). Finally, we apply the proposed method to several representative examples to demonstrate its effectiveness, efficiency, versatility, and potential to handle complex industrial structures.

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.

Observation and modeling of the thermal runaway of high-capacity pouch cells due to an internal short induced by an indenter

Owing to the complexity of coupling mechanical and electrical solvers for finite element analysis (FEA) of mechanical abuse of a battery, the simulation should be performed by incorporating a local short circuit model activated based on the status of battery elements. However, the approach should also consider various other conditions of the battery simulated, such as the initial state of charge (SOC), for precise simulations of the internal short. This study proposes an approach developed with a mechanical model and single-particle battery model, along with a reaction kinetics model for thermal abuse using LS-DYNA. Several key parameters were selected, such as the activation criteria, kinetic abuse and element integration points during the internal short circuit induced by the indenter. The impact of these key parameters in the FEA on thermal runaway response for various initial SOCs from 25to 100 % were analyzed. The FEA results obtained were compared against experimental results with various parameters such as activation criterion of internal short, kinetic abuse based on accelerating rate calorimetry (ARC) data. Finally, the root causes of the discrepancy between the FEA and experimental results are discussed regarding integration point what solver can make difference during calculation.

Modelling of Intervertebral Disc (IVD) with Structured Mesh and Crosswise Collagen Fibers.

The highly organized collagen network of human lumbar annulus fibrosus (AF) is fundamental to preserve the mechanical integrity of the intervertebral discs. In the healthy AF, fibers are embedded in a hydrated matrix and arranged in a crosswise fashion, giving an anisotropic structure capable to undergo large strains. For finite element analysis (FEA) of spine, modelling a realistic intervertebral disc geometry has always been a challenge. This paper proposes a simple yet efficient workflow details for generating structured mesh of the ground substance of the AF and the method for generating collagen fibers with controllable angles that are embedded in AF.Clinical Relevance- The biomechanical response of spine is usually studied by finite element analysis (FEA) of the assembly of vertebra and IVD and other components. The FEA results are always dependent on the correct generation of the geometry and the material of the components. For IVD, creating structured mesh with crosswise collagen fibers with adjustable angles will provide a better control over the anisotropic property definitions of the IVD and approaching a more realistic simulation.

Impact of different CAD/CAM materials on internal and marginal adaptations and fracture resistance of endocrown restorations with: 3D finite element analysis

PurposeTo assess and compare the impact of various computers aided design/manufacturing (CAD/CAM) materials on internal and marginal discrepancies, fracture resistance and failure probability of Endocrown restorations with 3D Finite Element analysis.Material and methodsForty devitalized human maxillary first molars were collected. After endodontic treatment, they classified into 4 groups (n = 10) based on the materials used for endocrown fabrication. Group V (Vita-Enamic), Group N (Nacera Hybrid), Group T (Translucent Prettau Zirconia) and Group P (Pekkton ivory). All samples were exposed to artificial aging method simulating one year of clinical service. Silicone replica technique and stereomicroscope (25X) utilized to evaluate the marginal and internal gaps of endocrowns at different areas. Fracture resistance test used for cemented specimens followed by qualitative investigation utilizing Stereomicroscopy. Four models representing four endocrown systems used for restoration of severely-damaged endodontically treated upper first molar were generated for finite element analysis (FEA). Axially and centrally static occlusal compressive load was applied. Modified Von Mises and maximum principal stress values on the remaining tooth structure, cement lines and restorative materials were assessed independently. Resulted data were statistically analyzed at P-value ≤ 0.05.ResultsIn the current study, the highest mean values of internal and marginal discrepancies (μm) among studied groups were reported for Zirconia group (100.300 and 102.650) respectively, while the lowest mean value of internal discrepancy (μm) was observed for Nacera group (69.275) and the lowest mean value of marginal discrepancy (μm) was observed for PEKK group (78.4750). Regarding internal discrepancy, Vita-Enamic and PEKK groups did not exhibit any statistically significant differences (P = 0.293), however zirconia and the other tested groups exhibited statistically significant differences in the mean values of the marginal gap region (p 0.05).On the other hand, PEKK group showed the highest mean value of fracture resistance (1845.20 N) and the lowest value was observed for Vita-Enamic group (946.50 N). Regarding to stress distributions through 3D FEA, and according to modified von Mises (mvM) analysis, the greatest possible stress values were noticed in PEKK model in relation to tooth structure, cement line, and flowable composite as the following: (93.1, 64.5, 58.4 MPa) respectively, while Zirconia revealed lower maximum stress values (11.4, 13.6, 11.6 MPa) respectively.ConclusionsStatistically excellent marginal and internal fit was observed for PEKK in relation to other used endocrown materials. Also, PEKK material explained fracture resistance comparable to zirconia value while the lowest value was detected for Vita Enamic material.