Finite Element Method Stress Analysis Research Articles

Evaluation of stress distribution in restorations of maxillary central incisor with post-traumatic enamel-dentin fracture using two different techniques: A micro-computed tomography study

Aim: The aim of this study is to investigate the stress distribution created by two restorative techniques, adhesive reattachment of the fractured fragment and direct composite restoration, used in the treatment of a maxillary central incisor with enamel-dentin fracture. The analysis is conducted using the finite element stress analysis method on a three-dimensional (3D) model prepared based on micro-computed tomography data, following the application of different adhesive procedures on fractured teeth. Methodology: The avulsed left maxillary central incisor was scanned using a micro-computed tomography device. The obtained data was transferred to a computer and used for 3D modeling. In the models, a fracture line was created obliquely at a 45° angle, 3 mm away from the mesial surface towards the distoincisal corner of the tooth. Six restorations were planned on this model: three direct composite restorations and three adhesives, reattachments followed by composite application. The models for the adhesive reattachment method included: (1) internal dentin groove, (2) palatal composite laminate veneer, and (3) double palatal retentive groove. The models for the composite restoration technique included: (1) composite laminate veneer, (2) direct composite restoration following enamel beveling, and (3) composite application after double palatal groove preparation. Upon completion of the restorations, a 100-N force was applied from the palatal direction using the finite element stress analysis method. The results were analyzed to examine the amount and distribution of stress on the restorations and the tooth. Results: In all models, the highest stress values within tooth structures were observed in the enamel. The lowest stress value in the enamel layer was seen in model R-1, whereas the highest stress value was observed in model K-2. For direct composite restorations, the stresses on enamel, dentin, and restoration were relatively similar in each model, with no significant differences noted among these values. Among all applied composite restorations, the lowest stress value was observed in model R-3. When analyzing the stresses generated at the tooth-restoration and tooth-fractured fragment interface of the six models, the lowest stress in the enamel was observed in models R-1 and K-3, while the highest stress was seen in model R-3. Conclusion: According to the data obtained from the models, the shape of the restoration applied on the tooth, the technique used, and the location of the restoration affect the amount and distribution of stress accumulated in the tooth and restoration. However, the stress analysis results are not sufficient to evaluate the clinical success of restorations. There is a need for further studies utilizing different techniques to support the models used. How to cite this article: Olgaç Akgönül Ş, Çelenk S, Adıgüzel Ö. Evaluation of stress distribution in restorations of maxillary central incisor with post-traumatic enamel-dentin fracture using two different techniques: A finite element analysis based on micro-computed tomography data. Int Dent Res 2024;14(2):76-83. https://doi.org/10.5577/intdentres.535

Evaluation of stress distribution of different marginal designs on PEEK and PEKK substructure materials, cortical and cancellous Bone:A finite element analysis

High-performance polymers are used in different fixed prosthesis treatments due to their many advantages such as biocompatibility, shock absorption ability, high fracture resistance. The effects of marginal design on the forces on high-performance polymers are unknown. This study aimed was to investigate the stress distribution of different marginal designs on Polyetheretherketone (PEEK) and Polyetherketoneketone (PEKK) substructure materials, cortical bone and cancellous bone by finite element analysis. A first maxillary molar tooth was modeled in 3D using the "3D Complex Render" method. Considering the ideal preparation conditions (Taper angle was 6°, step depth was 1 mm, occlusal reduction was 2mm), four different configurations were modeled by changing the marginal design (chamfer, deep chamfer, shoulder 90°, shoulder 135°). PEEK, PEKK substructure, and composite superstructure were designed on created models. A total of 150N oblique force from two points and a total of 300N vertical force from three points were applied from occlusall. and the maximum principal stress, minimum principal stress, von Mises stress findings in the cortical bone, spongiose bone, and substructure were examined. The study was carried out by static linear analysis with a three-dimensional finite element stress analysis method. The highest maximum principal stress value in the cortical bone was observed when the PEEK+Shoulder 135° step at vertical force. The highest minimum principal stress value in the cortical bone was observed when the PEEK+Shoulder 90° step, and PEEK+deep chamfer step at oblique force. The highest maximum principal stress value in spongiose bone was observed when the PEEK+Shoulder 90° step. The highest minimum principal stress value in spongiose bone was observed when the PEEK+deep chamfer step at vertical force. The highest von Mises stress value in the substructure was observed when the PEKK+Deep chamfer step at oblique force. The lowest maximum principal stress value in the cortical bone was observed when the PEKK+Shoulder 135° step at oblique force. The lowest minimum principal stress value in the cortical bone was observed when the PEEK+Shoulder 135° step, and PEKK+shoulder 135° step at vertical force. The lowest maximum principal stress value in spongiose bone was observed when the PEEK+Shoulder 90° step. The lowest minimum principal stress value in spongiose bone was observed when the PEEK+Shoulder 135° step and PEKK+Shoulder 135° step at vertical force. The lowest von Mises stress value in the substructure was observed when the PEEK+Deep chamfer step at vertical force. When cortical and spongiose bone stress were evaluated, no destructive stress was observed. Considering the stresses occurring in the substructure the highest stress was observed in the chamfer step.

Finite element stress analysis in mandibular molars with apical root resorption and crown destruction after root canal treatment using various materials

Aim: The objective of this study is to analyze the stress distribution of root canal treated teeth under occlusal forces and aid in the selection of appropriate materials for teeth with root tip resorption and crown destruction, using the finite element stress analysis method (FEM). Methods: The study was conducted on two-rooted lower molar teeth, divided into five groups. The root length was 14 mm, the crown length was 7.5 mm, and the total length was 21.5 mm. It was assumed that the distal canals were resorbed by 4 mm. Group 1 consisted of untreated intact teeth. Group 2 involved filling the mesial canals with gutta-percha, filling the apical part of the distal canal with 4 mm Mineral Trioxide Aggregate (MTA), and fabricating the crown using glass fiber post and IPS e.max materials. Group 3 involved filling the mesial canals with gutta-percha, filling the apical part of the distal canal with 4 mm Biodentin, and manufacturing the crown using glass fiber post and IPS e.max materials. Group 4: The canals were filled with MTA, and an IPS e.max endocrown was used. Group 5: The canals were filled with Biodentin and an IPS e.max endocrown was used. The study examined the effect of a 100 Newton force applied in the occlusal direction on dental tissues using finite element stress analysis. Results: The study found that the application of fiber posts resulted in less stress accumulation in tooth tissues compared to endocrown. Conclusion: The use of Biodentin or MTA in endocrown teeth did not affect the stress in tooth tissues caused by applied force. In conclusion, while fiber posts increase durability by reducing stress in root-end resorbed teeth, the effect of Biodentin or MTA on stress resistance in dental tissues is limited. How to cite this article: Duran S, Şirin DA, Topbaş C. Finite element stress analysis in mandibular molars with apical root resorption and crown destruction after root canal treatment using various materials. J Med Dent Invest 2024;5:e240320. https://doi.org/10.5577/jomdi.e240320

Experimental Construction and Validation of Revised Drucker–Prager Model Using Finite Element Method for Moisture Condensation Zone in Bentonite-Bonded Silica Sand

For predicting casting deformation by FEM (finite element method) thermal stress analysis, this paper experimentally constructed and validated the Drucker–Prager (DP) model and its revised model (RDP) for the condensation zone of bentonite-bonded sand molds. The condensation zone has been known as a remarkably low-strength region in the mold, and its mechanical response should be dominant to the casting deformation. To construct the models through uniaxial and triaxial compression tests, the test pieces reproducing the condensation zone were prepared by permeating water vapor through a test piece of bentonite-bonded sand. The constructed models were then applied to the FEM stress analysis of the triaxial test to validate them by comparing the analytical stress–strain curves with the experiment. The experimental stress–strain curve after permeating water did not show any distinct yielding point; however, the analytical curve with the original DP model clearly exhibited a yielding point due to the yield criterion of the model. The distinct yielding criterion should be essentially fatal to reproduce the stress–strain relationship of the condensation zone. Contrarily, the RDP model reproduced the experimental curve with less than 10 % error and was found to be advantageous for modeling the smooth stress–strain relationship of the condensation zone.

Proposition of new yield criterion for green sand mold and its experimental validation by FEM stress analysis of triaxial compression test

Prediction of the deformation during shape casting by FEM (finite element method) thermal stress analysis has been desired. For such prediction, validated constitutive models are essential for both the casting alloy and the mold. In this paper, two fatal defects in the modified Cam-Clay (MCC) model, which has conventionally been employed for a green sand mold, are clarified. The aim of this paper is to concurrently resolve these defects by a new yield criterion. The defects were those that cause an unreal distinct yielding and dilatancy peak on the stress-strain curve, which was clarified by comparing the true stress-strain curves obtained in the experiment and the FEM stress analysis of a triaxial compression test. A device capable of measuring the true stress during vertical compression was newly developed for the triaxial experiment. These defects inevitably led the MCC model to overestimate the mold strength by approximately 200% of the experimental value. This paper provides a new yield criterion, which employs an additional yield surface with the Drucker-Prager inherent surface, to rectify these defects of the MCC model. As a result of the stress analysis of the triaxial test with the new criterion, the smooth stress-strain curve with neither a peak nor a distinct yielding was reproduced. The calculated compressive stress traced the experimental value with less than a 15% error. Therefore, the new criterion should remarkably improve the accuracy of calculating the mold strength in the FEM thermal stress analyses during casting when compared to the MCC model.

Teeth Restored with Bulk-Fill Composites and Conventional Resin Composites; Investigation of Stress Distribution and Fracture Lifespan on Enamel, Dentin, and Restorative Materials via Three-Dimensional Finite Element Analysis.

the aim of this study was to examine the stress distribution of enamel, dentin, and restorative materials in sound first molar teeth with restored cavities with conventional resin composites and bulk-fill composites, as well as to determine their fracture lifetimes by using the three-dimensional finite element stress analysis method. an extracted sound number 26 tooth was scanned with a dental tomography device and recorded. Images were obtained as dicom files, and these files were transferred to the Mimics 12.00 program. In this program, different masks were created for each tooth tissue, and the density thresholds were adjusted manually to create a three-dimensional image of the tooth, and these were converted to a STL file. The obtained STL files were transferred to the Geomagic Design X program, and some necessary adjustments, such as smoothing, were made, and STP files were created. Cavity preparation and adhesive material layers were created by transferring STP files to the Solidworks program. Finally, a FE model was created in the ABAQUS program, and stress distributions were analyzed. when the bulk-fill composite and conventional resin composite materials were used in the restoration of the cavity, the structures that were exposed to the most stress as a result of occlusal forces on the tooth were enamel, dentin, restorative material, and adhesive material. When the bulk-fill composite material was used in restoration, while the restorative material had the longest fracture life as a result of stresses, the enamel tissue had the shortest fracture life. When the conventional resin composite material was used as the restorative material, it had the longest fracture life, followed by dentin and enamel. when the bulk-fill composite material was used instead of the conventional resin composite material in the cavity, the stress values on enamel, dentin, and adhesive material increased as a result of occlusal forces, while the amount of stress on the restorative material decreased. In the fracture analysis, when the bulk-fill composite material was used instead of the conventional resin composite material, a decrease in the number of cycles required for the fracture of enamel, dentin, and restorative materials was observed as a result of the forces generated in the oral cavity.

The Effects of Using Cements of Different Thicknesses and Amalgam Restorations with Different Young’s Modulus Values on Stress on Dental Tissue: An Investigation Using Finite Element Analysis

Background: In this study, it was aimed to use a finite element stress analysis method to determine the amount of stress on enamel, dentin, restoration, resin cement and glass ionomer cement in amalgam class II disto-occlusal (DO) cavities by using two different cements with different thicknesses and amalgams with different Young’ s modulus values, respectively. Methods: A three-dimensional tooth model was obtained by scanning an extracted human maxillary first molar with dental tomography. A class II DO cavity including 95-degree cavity margin angles was created. Resin cement (RC) and glass ionomer (GI) cement with different Young’ s modulus measures (RC: 7.7 GPa, GI: 10.8 GPa) were used in amalgam. Different thickness combination groups were simulated: 50 μm, 100 μm and 150 μm. Additionally, amalgams with different Young’ s modulus values were used with the same thickness of different cements (Amalgam Young’s modulus: 35 GPa and 50 GPa). A load of 600 N was delivered to the chewing area. The stress distributions on enamel, dentin, restoration, resin cement and class ionomer cement were then analyzed using finite element analysis. Results: The most stress accumulation was observed in the enamel tissue across all groups where resin cement or glass ionomer cement were used in different thicknesses and where amalgam restorations were used with different Young’s modulus values. The least stress accumulation was observed in the cement itself. Conclusions: According to the results obtained, there was no difference between the two cement types in terms of stress accumulations in the models. However, when the same cements with different thicknesses were evaluated, it was concluded that the presence of both glass ionomer and resin cement with a thickness of 150 μm causes less stress on the restoration surface. Furthermore, when the cements were combined with different thicknesses and with different amalgam Young’ s modulus values, it was concluded that 50 GPa causes less stress on restoration surface.

Investigation of Heat Distribution in SOC-Stacks By Multiphysical Modeling

In the scope of clean energy, the solid oxide cell (SOC) offers a promising solution for different applications. The electrolyte, the air electrode and the fuel electrode of an SOC are typically based on yttrium stabilized zirconia (YSZ), lanthanum strontium cobaltite (LSC) or manganite (LSM) and nickel cermet, respectively. It typically operates in a temperature range of 600 – 1000 oC and can be operated as a fuel cell (SOFC), an electrolysis cell (SOEC) or reversibly (rSOC).An SOC-stacks consists of several repeating units, each of which is assembled by various components. Among them, the sealants are important to maintain the reliability and long-term operations of a stack. Several issues lead to high stress in the sealants, including the mechanical load, mismatch of thermal expansion coefficients, and thermal gradients 1. It was indicated that a small temperature gradient near the manifolds results in excessively high tensile stress. This may lead to glass ceramics sealing failure, which is critical in SOC designs 2. Therefore, the authors carry out the elastic stress simulations in an operating SOC-stack due to non-uniform temperature distributions.A previously introduced CFD model 3 is further developed to address coupled chemical and electrochemical reactions in rSOC-stacks. This model has been implemented in the open-source library, OpenFOAM. It considers the major multiphysical phenomena e.g. heat, mass, momentum and charge transport as well as heat radiation and electrochemical reactions and employs a volume-averaged approach 4. The computational requirements can be greatly reduced, which offers the possibility to simulate large stacks in reduced computing time. The temperature distributions derived from the stack simulation are used as inputs for thermal stress analysis, by mapping the interconnect temperatures to the detailed repeating unit. An open-source, finite element method (FEM) based software, Calculix, is applied to simulate the stress distributions. It is assumed all layers are tightly connected without slipping.The SOC-stack design considered in the multiphysical simulation as well as the FEM stress analysis is an in-house design, Mark-F20. It consists of 18 repeating units, each with an active area of approximately 320 cm2. The stack operates in the furnace condition, at a temperature of 700 oC, with CH4 mixture being supplied to the anode in the SOFC-mode (i=0.5 A/cm², U=0.8 V). The flow is in a counter-flow regime. A comparison of temperature distributions in interconnect is conducted between simulation and experiment. A maximum deviation of 10 K can be observed near the fuel inlet. It is acceptable providing the overall temperature variations of 80 K and the uncertainties in the measurements. This low-temperature zone results from the fast endothermic methane steam reforming reaction. The zone near the fuel outlet is cooled down by the inlet airflow on the cathode side. The stress-free temperature is 800 oC. It can be found that the maximum stress appears around the fuel inlet manifold with a magnitude of 100 MPa. The stress is also large near the air inlet manifold with a magnitude of 70 MPa. These areas show higher possibilities of mechanical failure.Consequentially, the stack model that has been developed enables to investigate the heat distribution in SOC-stacks. By comparing temperature distribution and the IV-curve predicted by the model with experimental measurements, good agreements were found.In the future, the sealant failure will be investigated 2 and attention has to be paid to future stack designs. References(1) Blum, L.; Groß, S. M.; Malzbender, J.; Pabst, U.; Peksen, M.; Peters, R.; Vinke, I. C. Investigation of Solid Oxide Fuel Cell Sealing Behavior under Stack Relevant Conditions at Forschungszentrum Jülich. Journal of Power Sources 2011, 196 (17), 7175–7181.(2) Bremm, S.; Dölling, S.; Becker, W.; Blum, L.; Peters, Ro.; Malzbender, J.; Stolten, D. A Methodological Contribution to Failure Prediction of Glass Ceramics Sealings in High-Temperature Solid Oxide Fuel Cell Stacks. Journal of Power Sources 2021, 507, 230301.(3) Zhang, S.; Peters, R.; Varghese, B. A.; Deja, R.; Kruse, N.; Beale, S. B.; Blum, L.; Peters, R. Modeling of Reversible Solid Oxide Cell Stacks with an Open-Source Library. ECS Trans. 2021, 103 (1), 569.(4) Beale, S. B.; Zhubrin, S. V. A Distributed Resistance Analogy for Solid Oxide Fuel Cells. Numerical Heat Transfer, Part B: Fundamentals 2005, 47, 573–591. Figure 1

Investigation of the Effects of Adhesive Materials of Different Types and Thicknesses on Dental Tissue Stress via FEM Analysis.

The aim of this study was to investigate the types and thicknesses of adhesive materials used in restorative treatment in dentistry in class I occlusal and class II disto-occlusal cavities and to examine the effects of stress distribution on enamel, dentin, restoration material, and adhesive material using the finite element stress analysis method. A 3-dimensional geometry of the tooth was obtained by scanning the extracted 26 numbered upper molar tooth with dental tomography. The 3D geometry obtained by using the Geomagic Design X 2020.0 software was divided into surfaces, and necessary arrangements were made. With the Solidworks 2013 software, 2 different cavity modeling, class I occlusal and class II disto-occlusal, with a cavity angle of 95 degrees on the 3D model, as well as 10, 30, and 50 micrometers thick, four types of adhesive materials and the modeling of the bulk-fill composite material on it were made. With finite element stress analysis, the stress distribution was analyzed using the Abaqus software. The materials used in the study are included in the simulation as isotropic linear elastic. Periodontal ligament and jawbone were not included in the analysis. A total of 600 N pressure was applied on the models. In our study, it was observed that the amount of stress on the tooth structures changed when the thickness, elastic modulus, and Poisson ratios of the adhesive material were changed. In addition, when all models are examined, it is seen that when the thickness is increased, more stress is placed on the adhesive material compared to the restoration, while when 50-micrometer-thick adhesive material is used, more stress is placed on the restoration compared to the adhesive material.

EVALUATION OF BIOMECHANICAL EFFECTS OF PROSTHETIC COMPONENTS WITH DIFFERENT MATERIALS ON THE ABUTMENT SCREW

Objectives: The purpose of this study was to evaluate the effects of different resin-based and ceramic superstructure materials and two different abutment types on the stress distribution of the abutment screw using the three-dimensional finite element stress analysis method. Materials and Methods: A three dimensional implant, abutment (zirconia and titanium), abutment screw, crown (zirconia reinforced lithium silicate, lithium disilicate, polymer-infiltrated resin ceramic, and PEEK), and alveolar bone were designed using Rhinoceros 3D modeling software and VRMesh Studio software and combined to form 8 simulations. On the models prepared, loading was made on the lingual tubercule of the maxillary right first premolar crown at an angle of 30° with 150 N force obliquely in the buccolingual direction. The von Mises values obtained from the abutment screw were compared according to the types of abutment and crown materials. Results: The von Mises stress values in the abutment screw were higher in the models using a titanium abutment abutment (on average 1336.24 MPa), and the lower stress values were obtained in the models using a zirconia abutment (on average 964.26 MPa). When the prosthetic material used was changed, no apparent difference was observed in the stress values on the abutment screw. Conclusions: Considering that the abutment screw is the weakest link of the implant system, zirconia abutments can be used reliably in the maxillary first premolar region where aesthetic expectations are high.

Nonlinear Stress Analysis of Compressed Composite Electrode in Sulfide All-Solid-State Lithium-Ion Battery with X-Ray CT

Sulfide solid electrolytes display favorable characteristics for applications in all-solid-state batteries.Various solid electrolytes have been developed so far, but in order to realize high ionic conductivity, it is necessary to apply pressure to reduce voids between the solid electrolytes[1][2]. This is important when preparing an electrode layer. Particularly in cathode, which is a mixture of hard cathode active materials and soft sulfide solid electrolyte, inhomogeneous stress distribution could be generated in the solid electrolyte in cathode. It is expected that this results in non-uniform ionic conductivity. Therefore, by analyzing stress distribution in cathode, ion transport phenomenon in the solid electrolyte can be clarified, and we can obtain insights for optimum battery design. There are mainly two methods for analyzing the stress distribution in powder mixture. One is Discrete Element Method (DEM), which treats powder particles as independent discontinuous bodies and analyzes interactions between powder particles. With DEM, while detailed interactions between voids and particles can be analyzed, stress analysis inside the particles is difficult. Moreover, the calculation cost is very high. Another is the Finite Element Method (FEM), which is a method that captures powder and voids as a continuous body that is divided into small elements for analysis. Although detailed interaction between voids and particles cannot be analyzed, the advantage of FEM is that all the stresses in each small area can be solved and the calculation cost is small. In previous study, ion transportation simulation in a pseudo cathode with linear FEM stress analysis was conducted [3][4]. The numerical ionic conductivity is almost same as the experimental results, but the results have large error range since the Young's modulus of the solid electrolyte must be constant in linear stress analysis. But in reality, the Young’s modulus of powder is not constant [5]. This is because the voids decrease as the stress increases. When the stress is low, the Young's modulus is small since many voids remain and there are rooms to fill the voids. However, when the stress is high, the Young's modulus is large since the powder will not strain with small amount of voids. For high accuracy numerical simulation with small error range, the Young’s modulus should not be constant and non-linear stress analysis should be conducted for FEM.In this study, to focus on the ionic conduction characteristics in the electrode layer, the cathode active material was replaced with an electrochemically stable ZrO2 to suppress the charge / discharge reactions. The prepared composite material was loaded into a cell with excellent airtightness, and three-dimensional structural measurement and strain measurement were performed by X-ray CT. Then, stress analysis by COMSOL was performed using the three-dimensional structural data obtained by X-ray CT.Figure 1 shows the relationship between Young's modulus and stress of a compressed solid electrolyte. As shown, Young's modulus of solid electrolyte has a strong nonlinearity and increases with stress. Figure 2 shows the stress-strain characteristics obtained from experiment, linear stress analysis, and non-linear stress analysis. Previous studies have shown that the Young's modulus of solid electrolytes is in between 25 MPa and 25 GPa.[5] In this study, we set the lower limit of Young's modulus to 25 MPa and the upper limit to 25 GPa for the error range in linear analysis. In linear analysis, error range is heavily dependent of the Young’s modulus of solid electrolyte. On the other hand, in nonlinear analysis, it is possible to reproduce the strain close to that from the experiment. Figure 3 is a cross-sectional view of the stress distribution in non-linear stress analysis results. In this figure, the stress is normalized by applied pressure. As seen in previous studies, materials with high Young’s modulus acts as pillar in a composite and causes stress concentration. [3].However, the relative stress in the solid electrolyte with applied pressure of 200 MPa is higher than that of 100 MPa. This is a result of reflecting the non-linearity of the solid electrolyte. As shown in Fig.1, the Young's modulus of a solid electrolyte with strong nonlinearity increases with increasing stress. As a result, it is considered that the difference in Young's modulus between ZrO2 and solid electrolyte decreases. And thereby causes the stress concentration on ZrO2 to decrease and causes the relative stress of solid electrolyte to increase. The higher the stress on solid electrolyte, the higher the ionic conductivity. We will also discuss the effect of non-linearity of solid electrolyte on ionic conduction characteristics by conducting electricfield analysis based on stress distribution obtained by non-linear analysis in oral presentation. Figure 1

A three-dimensional slope stability analysis method based on finite element method stress analysis

A new three-dimensional slope stability analysis method based on stress calculation by the finite element method is proposed. This method conforms to the uniform assumption of the sliding direction of the rigid limit equilibrium method and can easily be used calculate the three-dimensional sliding direction. By using this method, both the local and global safety factors of the slip surface can be calculated according to the integral mean value theorem. Additionally, an improved ellipsoidal slip surface construction method is proposed for roughly searching for the minimum safety factor and the critical slip surface. A two-stage particle swarm optimization is used to search for the critical slip surface more accurately. Two numerical examples of fixed slip surfaces are provided to confirm the effectiveness of the proposed method and its applicability to nonspherical slip surfaces. The influence of the slip surface mesh grid size, boundary conditions, Poisson's ratio, and dilatancy angle on the calculation results is revealed. Another two numerical examples of searching for the critical slip surface are then provided, and the results of the proposed method are compared with the results of the strength reduction method to confirm the validity of the proposed method.

Stress distribution in the composite electrodes of sulfide all-solid-state lithium-ion batteries

Pressurization of all-solid-state lithium-ion batteries is expected to increase the efficiency of ion transport between solid electrolyte particles. Here, we show the practicality of considering internal stress distribution to explain the ion transport behavior inside a composite electrode containing a sulfide solid electrolyte. Considering internal stress distribution allows for an accurate evaluation in microscale, and phenomenon stemming from nanoscale features is explained. To independently analyze the effect of ohmic overpotential on ion transport, undesired electrochemical reactions are eliminated by replacing active materials in a composite electrode by zirconia. The ionic conductivity of the zirconia composite at different pressures is measured and its three-dimensional structure is visualized by X-ray computed tomography. Graphics processing unit-based large-scale voxel finite element method stress analysis and an electric field numerical calculation are conducted to analyze the effect of stress distribution on the ion transport characteristics of the composite electrode. Experimentally, the ionic conductivity of the zirconia composite decreases drastically as the volume fraction of zirconia increases. The degree to which the ionic conductivity decreases exceeds that expected when considering the volume fraction and tortuosity of zirconia. When stress distribution is also considered, the discrepancy between experimental and numerical results decreases greatly.

Direct observation of hot tearing of Al-7%Si-0.35%Mg alloy

Hot tearing of an Al-7%Si-0.35%Mg alloy T-shaped specimen was analyzed by direct observation of cracking and a finite element method (FEM) stress simulation. The semi-solid state during cooling enables direct observation of corner surface cracks. Crack opening appears to begin before the solid fraction reaches 0.3. However, a liquid phase infiltrates and disturbs the crack opening process. After the onset of the eutectic reaction, crack opening resumes and is detected as hot tearing. The FEM stress analysis revealed that tensile stress concentrates at the corners of the T-shaped specimen. The tensile stress increases with time at the initial stage of solidification, peaks at around 170 s, and then decreases. Microstructural observation of cooled and quenched specimens reveals that if the inter-dendritic liquid phase is adequate and has high fluidity, then healing of the crack occurs.

FEM Modeling on Scratch Behavior of Multiphase Polymeric Systems

In-depth understanding of how the presence of dispersed particles influences the scratch behavior of multiphase polymeric systems requires extensive knowledge of the corresponding local deformation and damage mechanisms during scratching. Effects of particle type, size, and concentration on scratch behavior of multiphase polymeric systems have been investigated based on a three-dimensional finite element method (FEM) modeling effort. Effect of particles location underneath the surface during scratch has also been studied. The results show that the presence of hard and soft particles can drastically affect the stress and strain field development during the scratching process. The FEM stress and strain field analysis explains the experimentally observed scratch-induced damages in multiphase polymeric systems reported in the literature.

Finite Element Method Stress Analysis and Evaluation of the Sealing Performance in Box-Shape Flange Gasketed Connections Subjected to Internal Pressure

Bolted connections inserting gaskets such as box-shape flange connections have been widely used in mechanical structures, nuclear and chemical industry, and so on. They are usually used under internal pressure. In designing the box-shape flange connections with gaskets under internal pressure, it is important to clarify the gasket stress distribution for evaluating the sealing performance of these connections. However, no research in which the sealing performance of these connections is examined under internal pressure has been carried out. Thus, the design for box-shape connection such as thickness of flange cover, number of bolts, gasket width, and so on is not clarified. In this paper, the contact gasket stresses of these connections under internal pressure are analyzed using the finite element method (FEM), taking into account a hysteresis in the stress–displacement curve of the gasket. And then, using the contact gasket stress distributions obtained from FE analysis and the relationship between gasket stress and leak rate obtained from a gasket sealing test (JIS B2490), a method for estimating an amount of leakage is examined. Leakage tests were also conducted to measure an amount of gas leakage using an actual box-shape flange connection with a gasket. The estimated results are in reasonable agreement with the experimental results. In addition, the effect of gasket width, flange cover thickness, and flange cover material is examined on the sealing performances of box-shape flange connections under internal pressure. The effects of the above factors are discussed on the sealing performance in designing box-shape flange connections.

Finite element analysis of the stability of transverse acetabular fractures in standing and sitting positions by different fixation options

BackgroundTreatment of a transverse acetabular fracture type is possible from an anterior approach, a posterior approach or both. Different fixation methods have been described but whether one is superior to the other is still under debate. The aim of the current study was to test the different fixation alternatives of stabilization of transverse acetabular fractures under two basic physiological loading conditions: standing and sitting utilizing a finite element model. Material and methodsA transtectal transverse fracture model was fixed in five different alternatives: an anterior column plate; a posterior column plate; an anterior column plate combined with a posterior column screw; a posterior column plate combined with an anterior column screw; and a posterior column plate and an anterior column plate. In these models, a load of 400N was applied at standing and sitting positions and the displacements were analyzed by using three-dimensional finite element stress analysis method. ResultsIn the model simulating standing human position, overall motion at the posterior column was minimum when two columns were plated (0.071mm). The second best fixation was posterior column plate with an anterior column screw (0.077mm). Overall motion at the anterior column was minimum by posterior column plate with an anterior column screw (0.0326mm). The plating of two columns was associated with motion of (0.0333mm).In the model that simulates sitting position, the motion at the posterior column was minimum when two columns were plated (0.0478mm), and (0.0517mm) when a posterior column plate with an anterior column screw was used. Overall motion in the anterior column was minimum when posterior column plate with an anterior column screw (0.0198mm) was used, whereas the motion was (0.0203mm) when plating of both columns was examined. ConclusionPosterior column plating combined with an anterior column screw has quite comparable results to a both column plating in transverse fractures, suggesting that two column fixations might be unnecessary. This method is also very superior to anterior column plating combined with a posterior column screw in that type of fractures.

FEM and BEM Stress Analysis of Mandibular Bone Surrounding a Dental Implant

In the present work the structural behaviour of a mandible with a dental implant, considering a unilateral occlusion, is numerically analysed by means of the Finite Element Method (FEM) and the Boundary Element Method (BEM). The mandible, whose CAD model was obtained by computer tomography scans, is considered as completely edentulous and only modelled in the zone surrounding the implant. The material behaviour of bone is assumed as isotropic linear elastic or, alternatively, as orthotropic linear elastic. With reference to the degree of osteo-integration between the implant and the mandibular bone, a partial osteo-integration is considered; consequently a nonlinear contact analysis is performed, with allowance for friction at the interface between implant and bone. A model of a commercial dental implant is digitised by means of optical 3D scanning process and fully reconstructed in all its geometrical features. Special attention is drawn to the mathematical reconstruction of the CAD model in order to facilitate the meshing process in the BEM environment and reduce the geometrical imperfections generated during the CAD to CAE translation process. The results of FEM and BEM analyses in terms of stress distribution on the mandible are compared in order to benchmark the two methodologies against accuracy and pre-processing efforts.

FEM and Experimental Stress Analysis of a Jib Crane

Finite Element Method (FEM) and strain gage technique are used for analysing strain and stresses values on a jib cranes according to the standards. API and SAE J987 standards describe the test procedure and state the stress limits for cranes. The crane is constructed on a petroleum platform on the Caspian Sea. FEM was used to determine the critical points, which have high stress on the structure. Strain gages applied on these points are used to measure the strain and then stresses were calculated for each point. FEM and experiments’ results were compered to determine the differences and errors.

Researching the Influence of Carton Stiffness on the Hopper Design of Packaging Machine

Through studying carton stiffness, the hopper design of packaging machine is improved. By using the elastic-plastic theory and finite element stress analysis method, the hopper baffle design of automatic tea packaging machine is optimized in order to reduce the requirements of equipment for paper, solve the problem that automatic packaging machine stop work. At the same time, the stress analysis of carton is taken through the ANSYS to derive that the suction of sucker satisfy the requirements of carton stiffness or not, the carton appear plastic deformation in the force process or not.