Maximum Equivalent Stress Value Research Articles

Contact between leaked cement and adjacent vertebral endplate induces a greater risk of adjacent vertebral fracture with vertebral bone cement augmentation biomechanically

BACKGROUND CONTEXTAdjacent vertebral fracture (AVF) is a frequently observed complication after percutaneous vertebroplasty in patients with osteoporotic vertebral compressive fracture (OVCF). Studies have demonstrated that intervertebral cement leakage (ICL) can increase the incidence of AVF, but others have reached opposite conclusions. The stress concentration initially increases the risk of AVF, and dispersive concentrated stress is the main biomechanical function of the intervertebral disc (IVD). PURPOSEThis study was designed to validate the hypothesis that direct contact between the leaked cement and adjacent bony endplate (BEP) can inhibit this biomechanical function, trigger adjacent vertebral stress concentration and increase the risk of AVF. STUDY DESIGNA retrospective study and corresponding numerical mechanical simulations. PATIENT SAMPLEClinical data from 97 OVCF patients treated by bone cement augmentation operations were reviewed in this study. OUTCOME MEASURESClinical assessments involved measuring ICL and cement-BEP contact status in patients with and without AVF. Numerical simulations were conducted to compute stress values in adjacent vertebral body's BEP and cancellous bone under various body positions. MATERIALS AND METHODSRadiographic and demographic data of 97 OVCF patients (with an average follow-up period of 11.5 months) treated using bone cement augmentation operation were reviewed in the present study. The patients were divided into 2 groups: those with AVF and those without AVF. Bone cement leakage status was judged via 2 different methods: with or without IVD cement leakage and with and without adjacent vertebral endplate contact. The data from patients with and without AVF were compared, and the independent risk factors were identified through regression analysis. Patients without IVD cement leakage, with IVD cement leakage but without adjacent vertebral endplate cement contact, and with direct adjacent vertebral endplate cement contact were simulated using a previously constructed and validated lumbar finite element model, and the biomechanical indicators related to the AVF were computed and recorded in these surgical models. RESULTSRadiographic analysis revealed that the incidence of AVF was numerically higher, but was not significantly higher in patients with IVD cement leakage. In contrast, patients with direct adjacent vertebral endplate cement contact had a significantly greater incidence of AVF, which has also been proven to be an independent risk factor for AVF. In addition, numerical mechanical simulations revealed an obvious stress concentration tendency (the higher maximum equivalent stress value) in the adjacent vertebral body in the model with endplate cement contact. CONCLUSIONDirect adjacent vertebral endplate cement contact induces a greater risk of AVF through deterioration of the local biomechanical environment. Cement injection, therefore, should be terminated when IVD cement leakage occurs to reduce adjacent vertebral endplate cement contact and reduce the resulting risk of AVF biomechanics.

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.

DESIGN AND ANALYSIS OF THE KOMATSU PC400 EXCAVATOR'S TOOTH BUCKET THICKNESS USING THE FINITE ELEMENT METHOD

Bucket teeth are an important component of an excavator that functions as a material penetrator or digger. This part is prone to failure because it is in direct contact with the ground. This study aims to determine the value of stress, strain, deformation, and safety factors that occur in the Komatsu PC400 excavator bucket teeth against thickness variations of 2.5 mm, 5 mm, 7.5 mm, and 10 mm. This study uses a computer with specifications: processor: Intel (R) Celeron (R) N4000 CPU @ 1.10 GHz, memory: 8 GB. Windows 10 Home Single Language 64-bit Operating System. This computer is equipped with Autodesk Inventor Professional 2023 and ANSYS Workbench R1 2023 software. The method used in this research is a testing method using ANSYS software with a finite element method approach, namely static structural. The simulation results of bucket teeth show the maximum deformation values are 0.16382 mm, 0.13832 mm, 0.1249 mm, and 0.11619 mm, respectively. Furthermore, the maximum equivalent stress values are 108.6 Mpa, 79.712 Mpa, 80.338 Mpa, and 79.992 Mpa, respectively. For the equivalent elastic strain maximum, 0.00052993, 0.00038899, 0.000392, and 0.00039029 were obtained. Then the safety factor value is obtained 3.8214, 5.2062, 5.1657, and 5.188. This shows that the thicker the thickness variation, the better the strength value.

Design and Performance Study of a Six-Leg Lattice Tower for Wind Turbines

A new type of spherical node was used to design a laboratory-scale prototype of a six-leg lattice of steel tubes and concrete for application as a wind turbine tower. Repeated load tests were performed on the prototype tower for several weeks to evaluate its load-carrying capacity, deformation, energy consumption, stress distribution based on damage patterns, hysteresis curves, skeleton curves, strength, and stiffness degradation curves. The findings indicated that the prototype tower underwent thread damage to the high-strength bolts of the inclined web and weld damage between the inclined web and sealing plate. Although the stress differences between different measurement points were significant, the stress values were small at most of the measurement points. The maximum equivalent stress value was 294 MPa, which appeared in the middle layer of the BC surface. The P-Δ hysteresis curve had an inverse “S”-shape, and the bearing capacity was high. The maximum energy dissipation appeared in the 1.75 Δy loading stage. The peak load of the specimen can reach 376.2 kN, and the corresponding peak displacement is 37 mm. However, the average ductility coefficient was only 2.33, indicating little plastic deformation. The maximum strain of the tower column foot is 1800 με, and the force of the inclined web member in the middle layer is the largest. The strain of the transverse web bar increased significantly after the tower yielded, which contributed to maintaining the integrity of the structure.

Research on optimal design of 6in offshore flange connector’s sealing structure

Taking the maximum contact pressure as the objective function for, the optimal design model of the offshore flange connector was established to analyze the impact of the flange cone's angle and the curvature radius of the lenticular gasket's contact surface on the sealing performance of the connector. An optimized three-dimensional model of the offshore flange connector was constructed using the MATLAB software's fmincon function to obtain the optimal size of the cone angle and curvature radius. The maximum contact pressure and maximum equivalent stress values of the non-optimized and optimized offshore flange connectors under the cross combination of two design pressures and six operating temperatures were analyzed by Workbench software, and the sealing performance of the non-optimized and optimized offshore flange connectors was compared according to the sealing judgment basis. The results show that compared with the previously studied offshore flange connector, the sealing structure of optimized offshore flange exhibits maximum increase in contact pressure increase but maximum decrease in equivalent stress. Under actual operating circumstances, the optimized offshore flange connection performs better in sealing and is less prone to breakage.

Numerical Simulation and Application of Radial Steel Gate Structure Based on Building Information Modeling under Different Opening Degrees

The safe and stable operation of the radial gate is highly essential for hydropower stations. As the dynamic load of gate, water flow generally causes the irregular distribution of strength, stiffness, and the stability of the gate structure. Traditional simulation technology is usually used to investigate the impact of water flow on gate structure; however, there is a lack of integration and interaction of building information modeling (BIM) and numerical simulation technology to study this issue. Therefore, this paper proposed a computational framework combing BIM and numerical simulation to calculate and analyze the large complex hydraulic radial steel structure. Firstly, the 3D model of the radial gate was established by MicroStation2020, then, the finite element model was output by using it. Secondly, the change laws of strength, stiffness, and stability of the radial gate were analyzed by Ansys-Workbench2020R2 under different opening degrees. The numerical simulation results show that the maximum equivalent stress value was 142.19 MPa, which occurred at the joint between the lower longitudinal beam and the door blade. The maximum deformation was 3.446 mm, which occurred at two longitudinal beams’ middle in the lower part of the panel. When the opening degree is 0.0 m–9.0 m, the natural vibration frequency increases irregularly with the increase in the opening of the gate. Three main vibration modes of the gate vibration were obtained. It proves that it is feasible to analyze the structural performance of radial gates by using BIM and numerical simulation. Finally, the BIM and numerical simulation information management process was established to make the simulation results more valuable. This study expands the application value of BIM and provides a new research idea for large complex hydraulic steel structural analysis. The information management process described in this research can serve as a guide for gate operation and maintenance management.

Universal fixation system for pad printing of plastic parts.

Pad printing is used in automotive, medical, electrical and other industries, employing diverse materials to transfer a 2D image onto a 3D object with different sizes and geometries. This work presents a universal fixation system for pad printing of plastic parts (UFSP4) in response to the needs of small companies that cannot afford to invest in the latest technological advances. The UFSP4 comprises two main subsystems: a mechanical support system (i.e., support structure, jig matrix and braking system) and a control system (i.e., an electronic system and an electric-hydraulic system). A relevant feature is the combination of a jig matrix and jig pins to fixate complex workpieces with different sizes. Using finite element analysis (FEA), in the mesh convergence, the total displacement converges to 0.00028781 m after 12,000 elements. The maximum equivalent stress value is 1.22 MPa for the polycarbonate plate in compliance with the safety factor. In a functionality test of the prototype performed in a production environment for one hour, the jigs fixed by the plate did not loosen, maintaining the satisfactory operation of the device. This is consistent with the displacement distribution of the creep analysis and shows the absence of the creep phenomenon. Based on FEA that underpinned the structural health computation of the braking system, the prototype was designed and built, seeking to ensure a reliable and safe device to fixate plastic parts, showing portability, low-cost maintenance and adaptability to the requirements of pad printing of automotive plastic parts.

Biomechanical Analysis of Axial Gradient Porous Dental Implants: A Finite Element Analysis.

The porous structure can reduce the elastic modulus of a dental implant and better approximate the elastic characteristics of the material to the alveolar bone. Therefore, it has the potential to alleviate bone stress shielding around the implant. However, natural bone is heterogeneous, and, thus, introducing a porous structure may produce pathological bone stress. Herein, we designed a porous implant with axial gradient variation in porosity to alleviate stress shielding in the cancellous bone while controlling the peak stress value in the cortical bone margin region. The biomechanical distribution characteristics of axial gradient porous implants were studied using a finite element method. The analysis showed that a porous implant with an axial gradient variation in porosity ranging from 55% to 75% was the best structure. Under vertical and oblique loads, the proportion of the area with a stress value within the optimal stress interval at the bone-implant interface (BII) was 40.34% and 34.57%, respectively, which was 99% and 65% higher compared with that of the non-porous implant in the control group. Moreover, the maximum equivalent stress value in the implant with this pore parameter was 64.4 MPa, which was less than 1/7 of its theoretical yield strength. Axial gradient porous implants meet the strength requirements for bone implant applications. They can alleviate stress shielding in cancellous bone without increasing the stress concentration in the cortical bone margin, thereby optimizing the stress distribution pattern at the BII.

Stress analysis and stress fatigue life prediction of RCP impeller based on fluid-thermal-solid coupling

Due to the extreme working conditions of the reactor coolant pump (RCP), it is difficult to repair and replace the structure, so a more accurate technology is needed to analyze the dynamic characteristics of the RCP under extreme working conditions and predict the fatigue life. This paper takes the CAP1400 RCP as the research object, when analyzing the hydraulic excitation characteristics, it is found that resonance may occur when the excitation frequencies are 22fn, 28fn and 33fn, then use the unidirectional fluid-thermal-solid coupling technology to analyze the dynamic stress of the RCP, and then use nCode to calculate the stress fatigue. The results show that the fatigue form of the impeller is mainly stress fatigue, and the maximum equivalent stress value is 100.83 MPa, which appears at the junction of the suction surface of the blade and the front cover plate, and the point with the largest stress fluctuation is at the junction of the suction surface and the hub. The position with the shortest impeller life of the RCP is node 397, in the contact stress concentration area between the suction surface of the impeller blade and the hub, the damage value is 2.833 × 10-12, the cycle life value is 3.53 × 1011 times, and the continuous operation is 364.18 years, which meets the requirements of the RCP. Conforms to the safety criterion of 60 years of safe operation of the RCP.

Risk assessment on offshore pipes

Pipelines are the most frequently failed parts of oil production installations. Therefore, the safety of underwater gas pipelines became a very concerned focus in this study. This study aims to assess the risk of the pipeline due to changes in the new ABC Port shipping line that have the potential to pose a risk of pipeline damage. This study conducted a risk assessment on pipes at PT. XYZ due to anchor dropping, anchor dragging, and sinking ships. Based on the risk assessment that has been carried out on all risks, it is found that the level of risk is in an acceptable area and in the ALARP zone (As Low as reasonably Practicable Risk). Based on the results of the analysis using Ansys structural software, the maximum value of equivalent stress that occurs in the pipe due to dropped anchor can be received is no more than 0.9 of the SMYS (Specified Minimum Yield Stress) value of 4.05E+08 Pa.

Regional differences in bone mineral density biomechanically induce a higher risk of adjacent vertebral fracture after percutaneous vertebroplasty: a case-comparative study.

Adjacent vertebral fracture (AVF) is a frequently observed complication after percutaneous vertebroplasty (PVP) in patients with osteoporotic vertebral compressive fracture. Biomechanical deterioration initially induces a higher risk of AVF. Studies demonstrated that the aggravation of regional differences in the elastic modulus of different components might deteriorate the local biomechanical environment and increase the risk of structural failure. Considering the existence of intravertebral regional differences in bone mineral density (BMD) (i.e. elastic modulus), it was hypothesized in the present study that higher intravertebral BMD differences may induce a higher risk of AVF biomechanically. The radiographic and demographic data of osteoporotic vertebral compressive fracture patients treated using PVP were reviewed in the present study. The patients were divided into two groups: those with AVF and those without AVF. The Hounsfield unit (HU) values of transverse planes from the superior to the inferior bony endplate were measured, and the differences between the highest and lowest HU values of these planes were considered the regional differences of the HU value. The data from patients with and without AVF were compared, and the independent risk factors were identified through regression analysis. PVP with different grades of regional differences in the elastic modulus of the adjacent vertebral body was simulated using a previously constructed and validated lumbar finite element model, and the biomechanical indicators related to AVF were computed and recorded in surgical models. Clinical data on 103 patients were collected in this study (with an average follow-up period of 24.1 months). The radiographic review revealed that AVF patients present a significantly higher regional difference in the HU value and that the increase in the regional difference of the HU value was an independent risk factor for AVF. In addition, numerical mechanical simulations recorded a stress concentration tendency (the higher maximum equivalent stress value) in the adjacent vertebral cancellous bone, with a stepwise aggravation of the adjacent cancellous bony regional stiffness differences. The aggravation of regional BMD differences induces a higher risk of AVF after PVP surgery through a deterioration of the local biomechanical environment. The maximum differences in the HU value of the adjacent cancellous bone should, therefore, be measured routinely to better predict the risk of AVF. Patients with noticeable regional BMD differences should be considered at high risk for AVF, and greater attention must be paid to these patients to reduce the risk of AVF. Level III b.

Structural Integrity of Anterior Ceramic Resin-Bonded Fixed Partial Denture: A Finite Element Analysis Study.

This study was conducted as a means to evaluate the stress distribution patterns of anterior ceramic resin-bonded fixed partial dentures derived from different materials and numerous connector designs that had various loading conditions imposed onto them through the utilization of the finite element method. A finite element model was established on the basis of the cone beam computed tomography image of a cantilevered resin-bonded fixed partial denture with a central incisor as an abutment and a lateral incisor as a pontic. Sixteen finite element models representing different conditions were simulated with lithium disilicate and zirconia. Connector height, width, and shape were set as the geometric parameters. Static loads of 100 N, 150 N, and 200 N were applied at 45 degrees to the pontic. The maximum equivalent stress values obtained for all finite element models were compared with the ultimate strengths of their materials. Higher load exhibited greater maximum equivalent stress in both materials, regardless of the connector width and shape. Loadings of 200 N and 150 N that were correspondingly simulated on lithium disilicate prostheses of all shapes and dimensions resulted in connector fractures. On the contrary, loadings of 200 N, 150 N, and 100 N with rectangular-shaped connectors correspondingly simulated on zirconia were able to withstand the loads. However, two of the trapezoidal-shaped zirconia connectors were unable to withstand the loads and resulted in fractures. It can be deduced that material type, shape, and connector dimensions concurrently influenced the integrity of the bridge.

Biomechanical analysis of different fixation methods for Rorabeck II supracondylar femoral fractures after total knee arthroplasty

BackgroundLocking plate (LP) and retrograde intramedullary nailing (RIMN) are widely used to fix Rorabeck II supracondylar femoral fractures after total knee arthroplasty (TKA). The biomechanical properties of the implant used for treatment influence its longevity. Therefore, we aimed to evaluate the biomechanical stability of different fixations using finite element analysis. MethodsSeven finite element models (FEMs) were established, including LP groups (short LP, long LP, and double LP), RIMN groups (short RIMN and long RIMN), and mixed groups (long LP with short RIMN and long LP with long RIMN). The stress of the implants around the fracture area was calculated to evaluate the biomechanical stability under loads. ResultsStress was mainly distributed around the fracture area in all models. The stress-shielding phenomenon was most evident in the short LP. The trend in maximum equivalent stress values of implants around the fracture area for the seven internal fixations was: short LP (324.63 MPa) > short RIMN (306.37 MPa) > long LP (275.06 MPa) > long RIMN (262.74 MPa) > double LP (203.19 MPa) > long LP with short RIMN (124.42 MPa) > long LP with long RIMN (112.41 MPa). We found that the double LP can better disperse the stress than a single LP, and a long LP with long RIMN can prevent stress concentration and make the stress distribution more uniform. ConclusionFrom the perspective of biomechanics, long LP with long RIMN can stabilize fractures and avoid stress concentration in Rorabeck II supracondylar femoral fractures after TKA.

Estimation of three-point bending behavior using finite element method for 3D-printed polymeric sandwich structures with honeycomb and reentrant core

Sandwich structures are known as ultra-light porous materials. Because the structure has advantages in terms of acoustics, fatigue, and impact resistance that conventional stiffened plates cannot match, it has become a popular material in aerospace, automotive, marine, windmill, and architectural applications. One promising method for decreasing production waste and enhancing flexural stress is to employ Additive Manufacture (AM) technologies for sandwich structure manufacturing. In this study, polylactic acid (PLA), acrylonitrile butadiene styrene (ABS), and polyethylene terephthalate glycol (PETG) sandwich structures with reentrant and honeycomb cores were designed and then a finite element analysis (FEA) was carried out to compare the stress distributions in these sandwich composites. According to the findings, higher flexure stresses and specific energy absorption were obtained in the reentrant sandwich structures compared to honeycomb sandwich structures. A minimum equivalent stress value was found in the ABS material, while a maximum equivalent stress value was found in the PLA material.

Методика проектирования конструктивно-силовой схемы несущей поверхности малого удлинения с использованием топологической оптимизации

The paper proposes an algorithm for designing a power set of the low-aspect lifting plane for the air-to-air short-range unmanned aerial vehicle. The work objective was to reduce the lifting plane mass and to increase its strength characteristics taking into account the operational loads. The algorithm was based on introduction of the topological optimization method in terms of calculating the structure maximum static stiffness under constraints in volume. Calculations of the stress-strain state and topological optimization were carried out using the ANSYS Workbench 19.2 software package. Boundary conditions were determined; load acting on the wing was set. Material suitable for manufacturing the structure using additive technologies was selected for optimization. Topological optimization resulted in obtaining a structural power diagram of the wing power frame. Taking into account the actual operating conditions, a skin of constant thickness was added to the resulting load-bearing frame. To verify the study, comparative analysis of the optimized wing model and its possible analogue made by traditional methods was carried out. Results of this analysis showed that the mass of the optimized lifting plane was by 12.7% less compared to the mass of a typical stamped structure. At the same time, the maximum equivalent stress values for the optimized wing were 755.7 MPa, which was by 10.3% less than for the standard design. Recommendations were given for further stages of designing the resulting lifting plane.

The synergistic effect of mechanical vibration for skin puncturing using polymeric microneedles

The transdermal delivery effect of polymeric microneedles can be significantly improved with the aids of synergetic vibration. The finite element simulation software ANSYS was used to explore the skin puncturing results of microneedles under different vibration frequencies. The dynamic mechanical properties of polymeric microneedles and human skin were also investigated. Meanwhile, puncturing experiments were also performed under different vibration frequencies on abdomen of female mice using polymeric microneedles with different lengths. The results showed that the peak value of maximum equivalent stress and the plastic deformation of skin were the smallest at the vibrative frequency of 200 Hz. The maximum equivalent stresses presented 20%–50% decreases during the second puncturing cycle. Moreover, the puncturing result of longer microneedles (550 μm) is much better than that of shorter ones (350 μm) under the same vibration frequency. The average bottom diameter and penetration depth of the microchannel obtained under the conditions of 200 Hz vibration and 550 μm height microneedles were 671.03 and 367.55 μm, respectively. These results provided an experimental basis to verify the effectiveness of mechanical vibration for skin puncturing.

Two-dimensional analysis method of bonding stress at steel-bamboo interface

The steel-bamboo composite structure is a novel composite system in which structural components are composed of laminated bamboo panel and cold-formed thin-walled steel using structural adhesive. Therefore, the study of the interaction and bonding failure mechanism between bamboo panel, steel and adhesive layer is the prerequisite for ensuring that the system can give full play to the advantages of materials. In this paper, a two-dimensional mechanical model for calculating the interface stress between steel and bamboo is proposed. The theoretical solution not only satisfies the boundary condition of zero bonding shear stress at the end of the adhesive layer, but also solves the normal peeling stress, which cannot be obtained in one-dimensional theory. The maximum value of equivalent stress determined in two-dimensional analysis method agrees well with one-dimensional solution with an average error of 8.92%, which proves that the two-dimensional analysis method is feasible and reliable.

Analisa transient structural disc-brake dengan material yang berbeda menggunakan software finite element

One of the causes of traffic accidents is the vehicle factor caused by the brake system that is not functioning properly. Brakes are a very important component in a vehicle, its function is to reduce the kinetic energy of the vehicle where the safety of the driver is very dependent on this component. Materials are very important role in the design of disc brakes, the main factor in the braking process is friction, and each material has its own friction coefficient. In the automotive industry there are many types of disc brake materials, so it is necessary to conduct a more indepth study on the effect of the disc brake material to determine the deformation, stress and strain that happen during the braking process. The method we used is to design a disc brake on solidworks and simulate it in ansys 19.2 software to find the structural transient values of gray cast iron, aluminum alloy, stainless steel, and titanium alloy materials. The result of this research is a data on the transient structural disc brake of the Vario 125 CBS motorcycle with the highest maximum total deformation happens in the gray cast iron material of 8.4965 mm. For the maximum value of equivalent elastic strain, the highest happens in aluminum alloy material at 0.012275 mm/mm. For the highest maximum equivalent stress value happens in stainless steel material at 1494.3 Mpa.

Finite Element Stress Analysis of PEEK, Glass Fiber and Zirconia Post-Core Sys-tems in Maxillary Central Incisor

Objective: This study aims to analyze structural strength features (such as deformation and stress distributions) of polyether ether ketone (PEEK), glass fiber and zirconia post-core systems utilized in maxillary central incisor roots by means of finite element analysis (FEA).
 Material and Method: The main geometry of maxillary central incisor considered in this study was obtained using an intraoral scanner. Other sub-components were modelled in a parametric computer aided design software based on the data obtained from the literature. Glass fiber, PEEK and zirconia were defined as post materials. 100 N force was applied with 45° angle on the palatal surface of veneered tooth in the FEA set up. The FEA was solved with linear material model and static linear loading assumptions through a commercial FEA code. Visuals and numerical results related to equivalent stress (Von Mises) and deformation distributions were interpreted.
 Results: Maximum equivalent stress value of 32.76 MPa was calculated at the PEEK post-core. The maximum values for glass fiber and zirconia posts were 0.80 MPa and 21.17 MPa, respectively. Maximum equivalent stress values at the tooth roots in the glass fiber, zirconia and PEEK posts were 72.79 MPa, 69.01 MPa and 58.22 MPa respectively.
 Conclusion: The stress magnitude experienced at the PEEK post-cores on the root was lower than glass fiber post and zirconia post. Regarding to this, although, it may be concluded that PEEK may reduce the complications that require tooth extraction in clinical practice, further researches are suggested including clinical trials.

Performance and thermal stresses in functionally graded anode-supported honeycomb solid-oxide fuel cells

Enhancing the performance of anode supported honeycomb solid-oxide fuel cells via operating at higher temperatures is of great interest. However, working at a higher temperature leads to a significant rise in thermal stresses over the allowable limit. Thus, in the current study, functionally graded electrodes are considered to avoid cell failure due to higher thermal stresses. To assess the cell performance and thermal stress distribution, a theoretical investigation of a solid-oxide fuel cell with a honeycomb configuration using functionally graded electrode compositions is conducted through a comprehensive 3D model. The developed model includes the charge transport, mass and momentum transport, energy conservation, electrochemical reaction kinetics, and elastic stress. The model is numerically simulated and validated with the available experimental data. Results indicate that using functionally graded electrodes with grading index m = 1 significantly improves the fuel cell's performance, with an improvement in power density reaching around 60%. In addition, the most beneficial improvement is to reduce thermal stresses at elevated temperatures, for which the maximum value of equivalent stress is reduced to 85% less than the conventional electrode at a temperature of 1150 °C. Accordingly, the fuel cell's maximum power density can be obtained by operating at elevated temperatures with safe thermal stresses. These improvements are particularly attractive for applications requiring compact, reliable, and high-power devices based on fuel cell technology.