Reduce Stress Concentration Research Articles

Polyetheretherketone split post and core for restoration of multirooted molar with insufficient dental tissue remnants by digital techniques: a case report and 3-year follow up

BackgroundMulti-rooted teeth with extensive dental defects often face challenges in stability and biomechanical failure. High-performance polymer PEEK materials, with properties closer to dentin, show promise in reducing stress concentration and preserving tooth structure. This report aimed to explore the use of a highly retentive polyetheretherketone (PEEK) for manufacturing custom-made split post and core for the restoration of grossly destroyed endodontically treated molars.Clinical considerationsA 40-year-old female patient presented with complaints of loss of tooth substance in the posterior mandibular tooth. This case involved the digital design and fabrication of PEEK split post and core to restore multirooted molar with insufficient dental tissue remnants. The restorations were evaluated over a 3-year follow-up using the World Federation criteria (FDI). The restoration was clinically evaluated through intraoral examination, radiographic assessment, and subjective patient satisfaction, and was deemed clinically good according to FDI criteria.ConclusionThe outstanding mechanical properties of PEEK, coupled with the structure of the split post, provide an effective treatment option for weakened multirooted teeth. Simultaneously, the restoration configuration effectively addressed the challenge of varying postinsertion directions, and the interlocking mechanism between the primary and auxiliary posts enhanced the stability of the post and core.

Stem to prevent periprosthetic fracture after notching in total knee arthroplasty.

Improper osteotomy during total knee arthroplasty (TKA) can lead to anterior femoral notching, which increases the risk of periprosthetic fractures due to stress concentration. One potential solution is the addition of an intramedullary stem to the femoral component. However, the optimal stem length remains unclear. In this study, we aimed to determine the optimal stem length using finite element models. Finite element models of femurs were developed with unstemmed prostheses and prostheses with stem lengths of 50, 75, and 100 mm. Under squat loading conditions, the von Mises stress at the notch and stress distribution on four transversal sections of the femur were analyzed. Additionally, micromotion of the prosthesis-bone interface was evaluated to assess initial stability. The unstemmed prosthesis exhibited a von Mises stress of 191.8 MPa at the notch, which decreased to 43.1, 8.8, and 23.5 MPa for stem lengths of 50, 75, and 100 mm, respectively. The stress reduction on four selected femoral transversal sections compared with the unstemmed prosthesis was 40.0%, 84.4%, and 67.1% for stem lengths of 50, 75, and 100 mm, respectively. Micromotion analysis showed a maximum of 118.8 μm for the unstemmed prosthesis, which decreased significantly with the application of stems, particularly at the anterior flange. Intramedullary stems effectively reduced stress concentration at the femoral notch. The 50-mm stem length provided the optimal combination of reduced notch stress, minimized stress-shielding effect, and decreased micromotion at the anterior flange.

Impact and spread dynamics of a viscoelastic droplet on an inclined hydrophilic surface

In this work, the impact of a three-dimensional viscoelastic droplet on an inclined hydrophilic surface is investigated by means of direct numerical simulations. The volume-of-fluid method is adopted to capture the interface, and the Oldroyd-B model is used to describe the rheological behavior of the viscoelastic droplet. The effects of the Weissenberg number (Wi) and the Weber number (We) on the impacting and spreading processes are studied, including the viscoelastic droplet shape, velocity, energy transformation, and stress distribution. Our results are in good agreement with the experimental data in the literature. In particular, the elastic force markedly influences droplet deformation at intermediate Wi values, although this trend diminishes at higher or lower Wi values. With increasing We, the impacting viscoelastic droplet reaches its maximum deformation more rapidly, while the nonmonotonic peak of kinetic energy indicates that the droplet elasticity plays significant role at moderate We. Additionally, the inclination of the surface has a pronounced effect on the droplet spreading process, and the elongated viscoelastic droplet at larger inclination angle is likely to experience a stronger oscillation. According to further analyses, We exerts a modest influence on the change rates of the droplet potential energy and spreading length in the flow direction. However, a larger inclination angle reduces stress concentration and accelerates the change rates. Due to the oscillation dynamics, Wi exhibits a non-monotonic effect on the spreading process and induces a monotonous increase in potential energy of viscoelastic droplets. The above analyses provide insights into the impact mechanism of droplets on an inclined hydrophilic wall and, therefore, will guide the applications in the future.

The supporting structure strength analysis of indexing stamping machine for manufacturing thin-walled inverting steel tubes

Abstract Due to the occurrence of cracks in thin-walled inverting steel tubes during the inverting process leading to fractures, thereby failing to achieve the desired energy absorption effect, they were often manufactured by interstitial stamping process with the manual rotation of thin-walled tubes to reduce stress concentration points, which is not conducive to mass production. Therefore it proposes a new design scheme of the indexing stamping machine for mass production of thin-walled inverting tubes. And the tube supporting structure of the indexing stamping machine will undergo shear stress and axial stress during manufacturing operation. To ensure that the machine can operate properly, ANSYS software is employed to conduct strength and stability analysis for the supporting structure. The calculation results indicate that the main supporting structure can meet the strength requirements of the thin-walled inverting tube forming machine. These study findings provide some references for optimizing the structure design for indexing stamping machines.

Impact of screw tip design on screw anchorage: mechanical testing and numerical simulation

BackgroundScrew loosening is a commonly reported issue following spinal screw fixation and can lead to various complications. The initial cause of screw loosening is biomechanical deterioration. Previous studies have demonstrated that modifications in screw design can impact the local biomechanical environment, specifically the stress distribution on bone-screw interfaces. There are several different designs of screw tips available for clinically used pedicle screws; however, it remains unclear whether these variations affect the local stress distribution and subsequent screw anchorage ability.MethodsThis study conducted comprehensive biomechanical research using polyurethane foam mechanical tests and corresponding numerical simulations to investigate this topic. Models of pedicle screw-fixed osteoporotic polyurethane foam were created with two different clinically used screw tip designs (flat and steep) featuring varying tip lengths, taper angles, and diameters, as well as identical flank overlap areas and thread designs. The anchorage ability of the different models was assessed through toggle and pull-out test. Additionally, numerical mechanical models were utilized to compute the stress distributions at the screw and bone-screw interfaces in the different models.ResultsMechanical tests revealed superior anchorage ability in models utilizing flat-tipped screws. Furthermore, numerical modeling indicated improved anchorage ability and reduced stress concentration tendency in these models.ConclusionChanges in screw tip design can significantly impact the biomechanical anchoring capability of screws. Specifically, flatter tip pedicle screws may mitigate the risk of screw loosening by alleviating stress concentration on bone-screw interfaces.

Hysteretic behavior optimization of hollow laminated viscoelastomer-filled steel tube damper

This study proposes a shape optimization approach for designing hollow laminated viscoelastomer-filled steel tube dampers (HLVSTDs), aiming to reduce stress concentration, enhance energy dissipation capacity, and improve low-cycle fatigue performance. The shape optimization curve is obtained based on the definition of stress contours for HLVSTD bending moments and shear forces, with the assumption that points on the same contour yield simultaneously. Cyclic loading experiments were conducted on four HLVSTDs. Numerical models were established and validated to further investigate the mechanical properties, energy dissipation capacity, and seismic performance of the shape-optimized HLVSTDs. The results demonstrate that the shape-optimized HLVSTDs specimen exhibits excellent energy dissipation capacity and improved low-cycle fatigue performance. The calculated initial stiffness and yield force closely align with experimental values. Compared to non-optimized HLVSTDs, the shape-optimized HLVSTDs exhibit more uniform stress and equivalent plastic strain distributions, effectively reducing the concentration of plastic strains. Additionally, structures equipped with shape-optimized HLVSTDs demonstrate superior seismic performance.

Effect of microstructure evolution on impact toughness in advanced ultra-high strength steel

The microstructure evolution and strength-toughness matching relationship of advanced ultra-high strength steel were studied under the tempering temperature range of 200–400 °C. The Charpy impact absorption energy of U-notch and V-notch focused on the crack initiation and crack propagation processes, respectively. The peak impact absorption energy of the U-notch appeared at 300 °C due to reduced stress concentration from low GND (Geometrically Necessary Dislocations) density. The optimal mechanical properties were found after tempering at 250 °C, where martensitic blocks hindered crack propagation, resulting in the peak impact energy of V-notch.

Research on the Reinforcement Characteristics of Thick Cushion Layer and Rigid Pile Composite Foundation

The rigid pile composite foundation method is the most commonly used method for strengthening weak soil foundations. In this method, piles usually need to pass through weak soil layers, and the pile end falls on a bearing layer with good bearing capacity. Under existing technical conditions, the thicker the weak soil layer, the longer the pile body, and the more difficult it is to ensure the construction quality of the pile. In response to this issue, some scholars have adopted the rigid pile composite foundation method with a thick cushion layer for reinforcement treatment. This article uses PLAXIS 3D (V20.04.00.790) software to establish a finite element model of rigid pile composite foundation with a thick cushion layer and simulate the process of foundation reinforcement. The influence of parameters such as thickness, compression modulus, and shear strength index of the cushion layer on foundation settlement and pile–soil stress distribution is studied, and the reasonable range of these parameters is analyzed under the condition of considering reinforcement effect. Through comparative analysis, it can be concluded that for deep and weak soil areas, the thickness of the cushion layer can range from 0.5 to 2.6. The thickness and compressive modulus of the cushion layer have a significant impact on the settlement of the foundation, the pile–soil stress ratio, and the stress of the pile body, while the shear strength index of the cushion layer has a relatively small impact on these parameters. Reasonably selecting the geometric and mechanical parameters of the cushion layer can effectively reduce stress concentration at the pile top and better play the role of the soil between piles.

Experimental study on seismic behavior of RCS joints with asymmetric friction connections and slabs

This paper introduces a new reinforced concrete column-steel beam (RCS) joint that employs asymmetric frictional connections (AFC) to improve energy dissipation and moment transfer, reducing stress concentrations within the joint’s core. Two RCS joint specimens with AFC and floor slabs were designed and tested under quasi-static loading to analyze the impact of bolt preload on seismic performance. The experimental results demonstrate that RCS joints with AFC and slabs exhibit favorable seismic behavior in terms of bearing capacity, energy dissipation, and stiffness degradation. Increasing bolt preload enhances the bearing capacity, stiffness, and energy dissipation capacity of the joints. The failure occurred at the steel beam splice connections, while only minor micro-cracks appeared in the reinforced concrete column when the joint's bearing capacity dropped below 80% of the peak load. Displacement at the column top was primarily influenced by steel beam and column deformation, with minimal contribution from joint core deformation. The use of AFC effectively reduced deformation in the joint core area, meeting seismic design code requirements for “strong columns-weak beams.”

Heterogeneous structure and dual precipitates induced excellent strength-ductility combination in CoCrNiTi0.1 medium entropy alloy

Developing advanced structural materials with high strength and excellent ductility is crucial for meeting aerospace and military requirements. High/medium entropy alloys (H/MEAs) have garnered significant attention due to their superior mechanical properties. In this study, through severe deformation followed by heat treatment at temperatures in the range of 700–900 °C, we successfully obtained a fully recrystallized structure with double precipitates in non-equiatomic CoCrNiTi0.1. Tensile tests at room temperature revealed that the alloy annealed at 700 ° C for 1 h exhibited exceptional mechanical properties, with a yield strength of 1575 MPa, tensile strength of 1735 MPa, and ductility of 15 %. The ultrahigh yield strength is primarily attributed to the synergistic strengthening mechanisms including precipitation strengthening, grain-boundary strengthening, and HDI strengthening. The FCC/L12 interface facilitated dislocation transfer during deformation, reducing stress concentration and promoting uniform deformation. Additionally, deformation mechanisms such as stacking faults and trace twinning contributed to the alloy's excellent ductility, ensuring substantial work-hardening capability and achieving a remarkable strength-ductility combination. These findings not only offer an effective strategy for enhancing the mechanical performance of non-equiatomic MEAs but also deepen our understanding of synergistic strengthening and deformation mechanisms in alloys.

Harnessing 3D Printing and Electrospinning for Multiscale Hybrid Patches Mimicking the Native Myocardium.

Engineered cardiac tissues show potential for regenerative therapy in ischemic heart disease. Yet, selection of soft biomaterials for scaffold manufacturing is primarily influenced by empirical and compositional factors, raising concerns about arrhythmic risks due to poor electrophysiological integration. Addressing this, we developed multiscale hybrid myocardial patches mimicking native myocardium's structural and biomechanical attributes, utilizing 3D printing and electrospinning techniques. We compared three patch types: pure silicone and silicone-poly(lactic-co-glycolic acid) (PLGA) with random (S-PLGA-R) and aligned (S-PLGA-A) fibers. S-PLGA-A patches with fiber orientation angles of 95-115° are achieved by applying a secondary electrical field using two parallel aluminum enhancers. With bulk and localized moduli of 350-750 and 13-20 kPa resembling the native myocardium, S-PLGA-A patches demonstrate a sarcomere length of 2.1 ± 0.2 μm, ≥50% higher strain motions and diastolic phase, and a 50-70% slower rise of calcium handling compared to the other two patches. This enhanced maturation and improved synchronization phenomena are attributed to efficient force transmission and reduced stress concentration due to mechanical similarity and linear propagation of electrical signals. This study presents a promising strategy for advancing regenerative cardiac therapies by harnessing the capabilities of 3D printing and electrospinning, providing a proof-of-concept for their effectiveness.

Optimizing Structural Steel Spur Gear Design for Reduced Stress Concentrations in Industry 4.0 Using Finite Element Analysis

Abstract: The advent of Industry 4.0 has highlighted the importance of spur gears in power transmission across the automotive, aerospace, and marine industries. However, these gears are susceptible to failure due to bending and contact stresses from fatigue. Designing an involute gear profile presents challenges, particularly in managing tooth root stresses and avoiding interference. This study tackles these issues through comprehensive stress analysis, using modeling and FEM assessment. The focus is on evaluating bending stresses at critical locations and identifying strategies to reduce stress concentrations at the gear tooth root. By enhancing gear robustness, this research could contribute to potential patents in gear technology. Background: Spur gears are crucial for power transmission but often fail due to fatigue-induced stresses and design challenges at the tooth root. Objective: This study aims to address spur gear design challenges through comprehensive stress analysis, using modeling and FEM to assess bending stresses and explore strategies to reduce stress concentrations at the tooth root. Methods: The research uses SolidWorks and ANSYS for FEM analysis, focusing on bending stresses and exploring modifications in gear design using various materials for optimization. Results: The analysis shows strategic modifications to the gear's fillet radius and addendum can reduce stress at the tooth root by 38.26%, with stainless steel being the optimal material for enhanced gear strength. Conclusion: The study emphasizes strategic adjustments in fillet radius and addendum to reduce stress in spur gears, highlighting stainless steel's superior performance for optimized design and enhanced strength.

Strength analysis and structural improvement of the connection between rear shock absorber support and frame of a city bus based on Hypermesh

Abstract In response to the phenomenon of cracking at the rivet holes of the plate connecting the rear shock absorber to the frame of the 6-meter leaf spring of the passenger bus, this article takes the rear shock absorber support and the frame as the research object. Firstly, CATIA software is used to model the object, and Hypermesh is used to divide the mesh to establish a fine element model. The Optistruct finite element solver is used to analyze the strength of the model, and the analysis results are imported into Hyperview 2019 for post-processing to analyze stress distribution and stress concentration. The simulation analysis results show that when a force of 6, 721 N is applied to the rear shock absorber support, the maximum stress value occurs at the rivet holes of the plate connecting the support to the frame, and the maximum equivalent stress value at this point is greater than the yield limit of the frame material, which is consistent with the crack location that occurs during actual vehicle operation. After adopting the strengthening scheme, the stress distribution of the frame is more uniform, greatly reducing stress concentration. The maximum stress value appears on the inner side of the right frame, and the maximum equivalent stress is less than the yield limit of the frame material, avoiding the crack phenomenon. The results indicate that this scheme can not only meet the performance requirements but also provide a reference for structural improvement and optimization design of the connection between the rear shock support and the frame.

Improve the impact property in a novel butt joint of Ti/Al dissimilar metals

The dissimilar metal welding joint is connected by the metallurgical bond of intermetallic compounds at the interface, which easily causes stress concentration at the interface and cracks continuously along the interface, resulting in low reliability in impact environments. A novel multi-layer plug and bolt connection for TC4/7A52 dissimilar metal butt joints is proposed in this manuscript and analyzes the influence mechanism of the structural design on impact toughness. The impact toughness of the Ti/Al composite butt joint is 30.3 J/cm2, which is 2.6 times that of the 7A52 BM. The layered toughening design significantly reduces stress concentrations for the butt joint at impact for the Ti/Al composite butt joint. Upon impact, the Ti/Al composite butt joint does not fracture continuously at the V-notch and exhibits significant macroscopic plastic deformation. For the microstructure of each TC4 and 7A52 layer in the impact fracture, more intragranular slip systems are activated and show a higher dislocation density. Therefore, this structural design can enable dissimilar metals to absorb more impact energy during the impact process.

Comparative study on mechanism of hydrogen embrittlement of Fe–18Mn-0.6C twinning-induced plasticity (TWIP) steel subjected to friction-stir welding (FSW) and tungsten inert-gas (TIG) welding

In present study, we investigated the effect of welding technique on resistance of hydrogen (H) embrittlement in Fe–18Mn-0.6C (wt.%) twinning-induced plasticity (TWIP) steel by using an electrochemical H-charging, thermal desorption spectroscope, and electron microscope. The friction-stir welding (FSW) specimen was less sensitive to H embrittlement relative to base metal and tungsten inert-gas (TIG) welding specimens by differences in microstructure and deformation mechanism. During H-charging of the FSW specimen, numerous dislocations/Σ3 boundaries reduced H diffusion into specimen interior, causing shallowest depth of brittle fracture. In contrast, the depth of brittle fracture in the H-charged TIG specimen was much larger due to rapid H diffusion by decreased grain boundaries including Σ3 annealing twin boundaries. During tensile deformation, the H-charged FSW specimen underwent the reduction in stress concentration by inactive TWIP as well as strong resistance of boundary decohesion. It was because of alleviation of H-enhanced localized plasticity (HELP) mechanism, leading to suppression of H-induced crack growth. Conversely, the H-charged base metal and TIG specimens revealed large stress concentration by active TWIP and weak boundaries owing to strong effects of HELP + H-enhanced decohesion (HEDE) mechanisms, exhibiting rapid H-induced crack propagation.

Enhancing the energy absorption capability of auxetic metamaterials through auxetic cells within re-entrant circular units

Re-entrant circular (REC) auxetic metamaterials have garnered significant attention in structural engineering due to their enhanced energy absorption capability and reduced stress concentration compared to traditional re-entrant auxetic configurations. However, there is considerable potential for further enhancing their design to achieve even greater energy absorption capabilities. This study introduces three novel REC auxetic structures (REC-S, REC-Star and REC-Flower) specifically designed to enhance energy absorption capabilities compared to traditional REC configurations. These structures are formed by deploying an S-shaped, a star, and a newly designed auxetic unit-cell (UC) named Flower into the REC framework and fabricated through 3D printing by using fused deposition modeling (FDM) techniques. Their deformation behavior and mechanical performance are assessed through quasi-static compressive experimental tests and finite element analysis (FEA), with good agreement obtained between the two sets of results. Based on the validated FEA, the effects of the geometrical parameters of the structures on specific stiffness (Es), specific energy absorption (SEA), and Poisson's ratio are further investigated. The results show that the newly designed structures outperform the traditional REC structure with equivalent relative densities (∆ρ) and the REC-Flower has the highest SEA for all relative densities, positioning it as a promising candidate for the next generation of REC structures.

In‐Plane Crushing Response of a Novel Arc‐Curved Hybrid Honeycomb with Negative Poisson's Ratio

Incorporating arc‐curved configuration into auxetic honeycomb can evenly distribute pressure, reduce stress concentration, and avoid fracture. In this work, a novel arc‐curved chiral star‐shaped honeycomb (ACSH) has been proposed by combining the chiral honeycomb (CH), the star‐shaped honeycomb (SSH), and arc‐curved configurations. The crushing response of the ACSH is studied experimentally and numerically. In order to verify the accuracy of simulation, quasi‐static compression experiment is carried out on the ACSH sample fabricated by 3D printing. Subsequently, the crashworthiness of the ACSH is compared with other honeycombs. Particularly, under the crushing velocity of 2 m s−1, the ACSH exhibits exceptional specific energy absorption, which is 179% higher than that of the conventional SSH. Additionally, it is also found that introducing arc‐curved configuration can effectively reduce initial peak stress. Moreover, the effect of functionally graded design on crashworthiness is systematically analyzed. The findings indicate that the initial peak stress decreases with the decrease of gradient rate. When crushing velocity increases to 80 m s−1, the SEA of the ACSH increases with the increase of gradient rate. This work investigates the crushing response of a novel honeycomb, which can provide a reference for designing and optimizing novel lightweight honeycombs with better crashworthiness.

Static and fatigue behavior of concrete bridge deck slabs reinforced with BFRP and steel bars

Using Fiber-reinforced polymer (FRP) has proved great promise as an alternative to conventional steel in bridge constructions owing to its high tensile strength and corrosion resistance. However, using Hybrid reinforced concrete (RC) slabs displayed enhanced stiffness, narrower crack width and larger bending capacity compared with FRP-RC slabs. This paper studies the static and fatigue performance of concrete bridge deck slabs reinforced with hybrid basalt-FRP (BFRP) and steel bars. The main parameters were the effective reinforcement ratio, the FRP-to-steel bars ratio Af/As, and the fatigue limit. The test results exhibited that superior fatigue behavior was achieved in the hybrid-RC slabs because the hybrid bars can better distribute the load and reduce stress concentration. In addition, the fatigue life growths with increasing the effective reinforcement ratio while reverse trend was observed when increasing Af/As ratio. In addition, increasing the upper fatigue load limit deteriorates the slab stiffness and significantly reduces the fatigue life. A regression analysis has been performed and revealed that the concrete deck slab can withstand 2 million cycles after fatigue loading of an upper fatigue load limit of 34 % of its ultimate static capacity.

A novel polyurethane-based mortar for pavement crack repair: Development, characterization, and performance evaluation

In light of the severe hazards posed by pavement cracks on traffic safety and infrastructure longevity, the development of a convenient and effective pavement repair material has become essential. The excellent cohesive strength and resilience of PU offer significant potential as a crack repair material, ensuring enhanced durability and reliability in pavement crack repairs. This study systematically explored the workability, mechanical properties, interface bonding performance, and fracture behavior of PUM as a pavement repair material through mechanical strength tests, interfacial tensile tests, and three-point bending tests based on DIC. The results indicate that the fluidity of PUM can be adjusted through the binder-sand ratio and PD content, enabling customization for various repair scenarios. PUM demonstrates exceptional one-day compressive and flexural strengths, achieving 18.8 MPa and 7.1 MPa, respectively. Furthermore, the bond tensile strength of PUM reaches 4.3 MPa, exhibiting accelerated strength development that meets the requirements for vehicle traffic after repairs. The lower elastic modulus of PUM, ranging from 0.28 to 0.63, indicates improved deformation adaptability. SEM analysis reveals a complex interfacial bonding network between PU and aggregates, considerably enhancing the energy dissipation capacity of PUM with a peak GF value of 205.05 N/m. DIC technology robustly captured the crack progression, revealing significantly reduced stress concentration at the crack tip of PUM, with no through-thickness cracks detected during the three-point bending fracture process. It is recommended that PUM be prepared with an 80 % binder-sand ratio and 5 % PD to achieve an optimal balance of workability, mechanical, and fracture properties.

Effect of margin designs and loading conditions on the stress distribution of endocrowns: a finite element analysis

BackgroundMargin designs and loading conditions can impact the mechanical characteristics and survival of endocrowns. Analyzing the stress distribution of endocrowns with various margin designs and loading conditions can provide evidence for their clinical application.MethodsThree finite element analysis models were established based on the margin designs: endocrown with a butt-joint type margin (E0), endocrown with a 90° shoulder (E90), and endocrown with a 135° shoulder (E135). The E0 group involved lowering the occlusal surface and preparing the pulp chamber. The E90 group created a 90° shoulder on the margin of model E0, measuring 1.5 mm high and 1 mm wide. The E135 group featured a 135° shoulder. The solids of the models were in fixed contact with each other, and the materials of tooth tissue and restoration were uniform, continuous, isotropic linear elasticity. Nine static loads were applied, with a total load of 225 N, and the maximum von Mises stresses and stress distribution were calculated for teeth and endocrowns with different margin designs.ResultsCompared the stresses of different models under the same loading condition. In endocrowns, when the loading points were concentrated on the buccal side, the maximum von Mises stresses were E0 = E90 = E135, and when there was a lingual loading, they were E0 < E90 = E135. In enamel, the maximum von Mises stresses under all loading conditions were E0 > E90 > E135. In dentin, the maximum von Mises stresses of the three models were basically similar except for load2, load5 and load9. Compare the stresses of the same model under different loading conditions. In endocrowns, stresses were higher when lingual loading was present. In enamel and dentin, stresses were higher when loaded obliquely or unevenly. The stresses in the endocrowns were concentrated in the loading area. In enamel, stress concentration occurred at the cementoenamel junction. In particular, E90 and E135 also experienced stress concentration at the shoulder. In dentin, the stresses were mainly concentrated in the upper section of the tooth root.ConclusionStress distribution is similar among the three margin designs of endocrowns, but the shoulder-type designs, especially the 135° shoulder, exhibit reduced stress concentration.