Principal Stress Values Research Articles

Does a sloped neck implant design facilitate All-on-4 surgeries? A three-dimensional finite element analysis

Aim: In the treatment of edentulous resorbed mandibles using All-on-4 concept, the distal part of posteriorly tilted implants with a conventional flat neck design is usually embedded in the bone, which may lead to improper installation or positioning of angled multiunit abutments. Bone trimming from the distal area, where the implant neck is embedded in the bone, is typically necessary to avoid this complication. This study aimed to evaluate the biomechanical behavior of a sloped marginal neck configuration of implant posteriorly tilted at 30° in edentulous mandibles using a three-dimensional finite element analysis (FEA). Methodology: The sloped neck implants were posteriorly tilted at 30° without any further operation in the edentulous mandibular model designed using the FEA. The tilted conventional flat neck implants were placed at the same length, diameter, and angle, and 2 mm2 of bone was trimmed from the distal area. Similar multiunit abutments, two conventional flat neck implants axially placed on the anterior side, titanium frameworks, and acrylic resin prosthetic dentures were created for both models. The biomechanical behaviors of the models were evaluated by applying a foodstuff force of 50 N to the incisors, 100 N to the premolars, and 150 N to the molar cantilever. Results: The von Mises stress value of the sloped neck implants (158.489 MPa) was lower than that of the conventional flat neck implants (177.208 MPa). Both the maximum and minimum principal stress values ​​in the surrounding cortical and cancellous bones were within the acceptable physiological limits. Conclusion: Sloped neck implants can be placed easily and are less invasive than conventional flat neck implants; thus, they can be a treatment alternative that can facilitate the All-on-4 concept. How to cite this article: Toprak ME. Does a sloped neck implant design facilitate All-on-4 surgeries? A three-dimensional finite element analysis. J Med Dent Invest 2023;4:e230310. https://doi.org/10.5577/jomdi.e230310 Linguistic Revision: The English in this manuscript has been checked by at least two professional editors, both native speakers of English.

Effect of Oblique SV Wave on the Seismic Response of Mountain Tunnel

In order to study the dynamic response of parallel mountain tunnels under the oblique incidence of seismic waves, based on the display finite element method and using viscoelastic artificial boundary, the oblique incidence of three-way seismic waves was realized by angular incident mode. The displacement and stress distribution characteristics of the tunnel lining under different propagation angles and vibration angles of SV waves were studied. The results show that the oblique incidence of SV wave has a certain effect on the displacement of the double tunnel, the forces in the tunnel are symmetrical and the axis displacement increases with the increase of incident angle, and the vertical displacement changes greatly. The stress of the tunnel lining under the oblique incidence of the SV wave is elliptical. The peak value of the maximum principal stress appears at the maximum span on both sides, and the maximum principal stress decreases with the increase of the vibration angle. The maximum principal stress of the right tunnel is flat. The minimum principal stress of the left and right holes decreases with the increase of vibration angle, and the minimum principal stress of the left hole is 90°∼270°. The distribution of the minimum principal stress in the range is large. Mises stress increases with the increase of the incidence angle of seismic waves.

Comparison between all-on-four and all-on-six treatment concepts on stress distribution for full-mouth rehabilitation using three-dimensional finite element analysis: A biomechanical study.

The current study intended to provide a comparison of biomechanical behaviors of two different treatment concepts for full-mouth rehabilitation with dental implants placed according to the "All-on-four" concept and "All-on-six" concept with analysis of the stress patterns of the implant support system using three-dimensional finite element analysis (FEA). The edentulous mandible was treated with two different implant designs. "All-on-Four" implant placement concept was used in Model 1 with two central axial implants and two distally tilted implants at 17° and in Model 2, "All-on-Six" concept was applied with six vertically placed implants. Individual vertical and horizontal load of 100 N and oblique load of 141 N at 45° was applied to all implants. To evaluate and compare the results in terms of maximum principal stress, we used FEA. All-on-six showed smaller maximum principal stress values on the cortical bone and implants. However, maximum principal stress values obtained on trabecular bone was smaller in the All-on-four design for vertical and horizontal loading conditions. The All-on-six approach showed more favorable biomechanical behavior.

Soil Slope Instability Mechanism and Treatment Measures under Rainfall—A Case Study of a Slope in Yunda Road

The unique geological conditions in Yunnan make it likely for landslides to occur there. For the purpose of exploring the soil slope instability mechanism, this paper takes a slope in Yunda Road, Chenggong, Kunming, as case study and establishes a slope model utilizing FLAC 3D coupled with Geo-studio software. The displacement, strain and deformation rate of the slope under the condition of rainfall are simulated, and the influence of rainfall and rainfall duration on rainfall infiltration is analyzed. The results indicated the following: (1) The effective stress on and shear strength of slope soil at the foot of the slope gradually decreased under rainfall, resulting in the loosening of the slope soil and slip at the foot of the slope. This affected the stability of the upper slope which, in turn, reduced the stability of the whole slope; (2) When the duration of rainfall reached 72 h, the slope stability coefficient Fs = 0.88, indicating a failure state. The increments of principal stress and shear stress at the foot of the slope were the largest, and the strain speed was the fastest, with the maximum values of principal stress and shear stress reaching 0.412 and 0.579, respectively; (3) The maximum total displacement was 2.177 m at the foot of the slope, the maximum vertical Z-axis displacement was 1.673 m in the negative direction of the Z-axis, and the soil at the foot of the slope was 0.6 m in the positive direction of the Z-axis. Our simulation results were consistent with the actual failure of the slope. After analyzing the slope mechanism and adopting targeted treatment measures, the slope was subjected to four rainfall cycles without any sign of landslips, indicating that the effect of our interventions was favorable.

Application of the in-situ stress testing technology for the design of operating pressure of underground gas storage reservoir

The appropriate design of the operating pressure of underground gas storages (UGSs) is of great significance to their safe and profitable operation. In situ stress is basic data for determining the upper limit pressure of UGSs, analyzing fault stability in reservoir areas, and evaluating trap tightness. Generally, the design of the upper limit gas injection pressure of UGSs is a comprehensive geomechanical problem. After research and comparison of measurement methods, it is believed that the measurement of in situ stress induced by hydraulic fracturing can accurately obtain the in situ stress value near the wellbore, and having knowledge about the reservoir stress path will considerably decrease the risk of reservoir and cap rock instability during gas injection and production. Taking Well C1, an oil reservoir-type UGS in Block M, eastern China as an example, this paper introduces the use of hydraulic fracturing (HF) in situ stress testing technology to obtain the minimum principal stress values of the caprock, reservoir and floor intervals of Well C1. The measured minimum principal stress of the caprock is 32.8–36.8 MPa. Because it is an old well, the minimum principal stress of the reservoir is 33.7–34.2 MPa after correction of the in situ stress measurement according to the theory of elasticity. Based on the comprehensive analysis of the measured in situ stress data, it is believed that the safe upper limit of the reservoir-type gas storage in Block M is 27.2 MPa.

Research on stress evolution law and failure characteristics of top coal in fully mechanized caving of extra-thick coal seams

In this study, based on the engineering background of the No. 8222 working face of the Tashan coal mine in Shanxi Province, China, true triaxial experiments were carried out on Geotechnical Consulting and Testing Systems rock mechanics testing machine using cubic coal samples, and the numerical simulation was conducted through the FLAC3D software. Moreover, the stress evolution law of different layers of extra-thick coal seams and the failure mechanism of top coal in the fully mechanized caving were investigated, and the failure structure model of top coal was established. The results show that there are differences in the principal stress values at different layers of the top coal.

Obrada struganjem kaljenih čelika alatima od PcBN

The paper discusses the results of the experimental investigation of the performance of several grades of PcBN cutting composites in conditions of the interrupted machining of hardened steel. Both BH and BL types of PcBN indexable inserts with additions of Si3N4, TiC, and TiCN were tested, and cutting speed varied to assess the possibility of applying these cutting tools in different conditions. It has been shown that BL PcBN can be utilized for turning with shock loads in case of high cutting speed and low depth of cut (0,2 mm). While in the range of comparatively low cutting speeds BL cutting tools are actually inoperable, and because of microchipping of polycrystalline fragments and brittle destruction of the cutting edge, an increase of the cutting speed to 210 m/min changes wear pattern and formation of the wear land. As well as this, measurement of the form and values of the cutting forces impulses revealed the effect of their peak growth by up to 40%. The danger of shock impulses was analyzed by FEM modeling, and it was demonstrated that during impacts, the maximal value of the third Principal stress exceeds the average level of compressive stresses during continuous cutting by 1.6 times, which can cause damage to the cutting tool. The data on the estimation of tool fracture probability depending on loading conditions are presented, and the possibility of reducing such probability is shown.

Evaluation of PEEK and zirconia occlusal rest designs for removable partial dentures based on finite element analysis.

Purpose We aimed to assess removable partial denture occlusal rests composed of polyether-ether-ketone (PEEK) and zirconia, using finite element analysis.Methods Three-dimensional PEEK and zirconia rest models, including the occlusal rest (1.5 mm thickness at the basal portion, 3.0 mm width) and minor connector (1.5 mm thickness, 6.0 mm height), and rest seat models with mechanical properties of enamel were constructed. The radius of transitional curvature between the rest and minor connector was 0.1-0.5 mm. The rest and rest seat model interfaces were set as frictional contacts (μ = 0.1), and the base of the rest seat model was restrained in all the directions. A 100 N downward load was applied perpendicular to the bottom surface of the minor connector. The maximum value of the first principal stress (Max-S1) was compared to the flexural and fatigue strengths of each material. Occlusal rests with 1.0-2.0 mm thickness, 2.0-3.5 mm width, and 0.5 mm radius of transitional curvature were analyzed.Results Max-S1 was observed at the transitional part and decreased with increasing radius of the transitional curvature, rest width, and thickness. PEEK rests with at least 1.5 mm thicknesses and 3.0 mm widths showed lower Max-S1 than the flexural strength. Max-S1 of all PEEK rests exceeded the PEEK fatigue strength, whereas Max-S1 of the zirconia rests was lower than the zirconia fatigue strength.Conclusions Zirconia occlusal rests with conventional metal rest designs have sufficient fatigue strength. PEEK occlusal rests have insufficient fatigue strength and may not withstand repeated mastication.

Stress distribution of endodontically treated mandibular molars with varying amounts of tooth structure restored with direct composite resin with or without cuspal coverage: A 3D finite element analysis.

Decision-making regarding whether cuspal coverage is required or not for the restoration of root canal-treated posterior teeth is still a matter of challenge for the dentist. Four models of endodontically treated mandibular molars with mesio-occlusal (MO) cavity were designed and simulated with direct composite resin restorations. Group 1A - cavity width <½ the intercuspal distance restored without cuspal coverage, Group 1B - same as Group 1A but with cuspal coverage, Group 2A - MO cavity width >½ but <2/3rd the intercuspal distance restored without cuspal coverage, and Group 2B - same as Group 2A but with cuspal coverage. The models received occlusal load to simulate a mastication load. Static finite element analysis (FEA) was adopted for predicting the stress distribution generated in the restored tooth by the loading condition. FEA of the models have shown that the variations in stress values were significant in bulk-fill material compared to enamel and other structures. Comparing the maximum and minimum principal stress values in the overall region demonstrated that 2A was safer, whereas 2B was found to be the worst case. The results indicate that restoration of endodontically treated mandibular molar with loss of one marginal ridge with composite resin without cuspal coverage revealed minimal internal stress values and showed the best performance overall.

Comparative photoelastic stress analysis between all-on-four implant-supported cobalt-chromium framework and carbon fiber reinforced framework with varying cantilever lengths - An in vitro study

CONTEXT: In implant prosthodontics, metal frameworks are used to rigidly spilt the implants together to provide rigidity and stiffness to the prosthesis. However, due to the limitations associated with the metal framework fabrication, the recent advances have made it possible to fabricate metal-free implant-supported prostheses using fiber-reinforced composite frameworks.AIM: This study aimed to evaluate and compare photoelastic stresses between all-on-four implant-supported cobalt-chromium (Co-Cr) framework and the carbon fiber-reinforced composite (CFRC) framework at varying cantilever lengths.MATERIALS AND METHODS: Two photoelastic models of an edentulous mandible were fabricated according to the all-on-four concept. Following this, frameworks with a bilateral cantilever extension of 20 mm, one with CFRC and the other with Co-Cr, were fabricated and were subjected to a progressive load of 120–180 N with an interval of 20 N. The principal stresses (σ) were calculated using the mean maximum fringe order.STATISTICAL ANALYSIS: The quantitative analysis was performed using the Kruskal–Wallis test and Mann–Whitney U-test, P ≤ 0.05.RESULTS: The CFRC framework showed mean principal stress values significantly lower than the Co-Cr framework under all loading conditions; however, deformation of the framework was observed at the cantilever lengths of 15 mm and 20 mm.CONCLUSION: The study and its findings have indicated that the CFRC framework appears suitable for the fabrication of a framework for an “All-on-four” prosthesis. Within the confines of this study, the use of 10 mm as an arbitrary cantilever length recommendation for the CFRC framework and 15 mm for the Co-Cr framework seems reasonable.

Effect of margin design changes on stress distribution in zirconia-based full-crown restorations: A three-dimensional finite element analysis

Aim: The aim of this study was to evaluate the effect of margin design changes on the stress distribution in zirconia-based full-crown restorations using three-dimensional finite element analysis. Methodology: For use in the design of full-crown restorations, tooth number 16 was prepared in chamfer step type on a maxillary tooth jaw model (AG-3: Tipodont, Frasaco, Germany). The prepared tooth was scanned using a desktop scanner, and a three-dimensional finite element analysis model was obtained. Zirconia frameworks are divided into three groups according to the margin design: uniform thickness hood type (Model A), ¾ partial crown form (Model B), and a lingual-band type (Model C). The crown form was completed using feldspathic porcelain as the superstructure material. To determine the stress distribution of the margin design on the restoration, the maximum principal stress (MPa) values under a 600 N vertical load were investigated. Results: The maximum stress on the zirconia framework was observed in Model A (82.90 MPa), and the maximum stress on the tooth was observed in Model B (49.34 MPa). The maximum stress on the feldspathic porcelain was highest in Model A (21.860 MPa), and the minimum stress on the tooth occurred in Model B (13.33 MPa). In the zirconia framework, the lowest stress was 11.54 MPa (Model B). Conclusion: The framework design was shown to affect the force generated on the restoration and transmitted to the tooth. The results of the present study will help dentists determine the ideal infrastructure design for zirconia-based restorations. Lingual band designs were found to be successful. How to cite this article: Güntekin N, Mohammadi R, Tunçdemir AR. Effect of margin design changes on stress distribution in zirconia-based full-crown restorations: A three-dimensional finite element analysis. Int Dent Res 2022;12(Suppl.1):10-5. https://doi.org/10.5577/intdentres.439 Linguistic Revision: The English in this manuscript has been checked by at least two professional editors, both native speakers of English.

The effect of the material used and the pulp chamber extension depth on stress distribution of endocrowns: A three-dimensional finite element analysis

Aim: The aim of this study was to examine the effects of materials used and the depth of extension into the pulp chamber on stress distribution in mandibular molar endodontically treated teeth with endocrown restoration using three-dimensional (3D) finite element analysis (FEA). Methodology: Three-dimensional finite element analysis models were obtained at two different pulp chamber extension depths by taking a tomography of a root canal-treated mandibular molar tooth extracted for periodontal reasons: 2.5 mm (Model A) and 3.5 mm (Model B). Models were divided into the following three groups according to material type used: Vita Enamic (VE), Lava Ultimate (LU), and IPS e.max CAD (EMX). The aforementioned model groups were further divided into the following two subgroups according to the types of cement used: NX3 and MaxCem Elite Chroma (MX). Maximum principal stress (MPa) values under 600 N vertical load were investigated to evaluate the effect of restoration design, material type, and cements used on stress distribution. Results: The maximum stress on the restoration was observed in the EMX material type (13.000 MPa) in the MX cement group in Model A, while the lowest was observed in the LU material (5.932 MPa) in the NX3 cement group in Model A. The areas of highest stress for both Models A and B were observed in the restoration areas corresponding to the enamel margins. Conclusion: Materials with a higher elastic modulus show a higher stress area on the restoration surface, while the stress values they transmit are lower. Materials with the elastic modulus close to dentin have more homogeneous stress distributions within the restoration. How to cite this article: Güntekin N, Mohammadi R, Tunçdemir MT. The effect of the material used and the pulp chamber extension depth on stress distribution of endocrowns: A three-dimensional finite element analysis. Int Dent Res 2022;12(Suppl.1):1-9. https://doi.org/10.5577/intdentres.436 Linguistic Revision: The English in this manuscript has been checked by at least two professional editors, both native speakers of English.

Substantiation and development of innovative container technology for rock mass lifting from deep open pits

Purpose. The research purpose is to substantiate the rational parameters of innovative container technology for transporting mine rocks in open pits with account of technological advantages. Methods. The winding machine normal operation was determined by calculation performed. The container metal structure was designed in the environment of the Compass-3D software complex. The structural elements were tested for normal operation using computer modeling methods in the APM WinMachine 9.7 program, which gives the possibility to obtain the strength calculation values. Findings. The results of modeling the stresses on the wall of the container and the frame, as well as the yield strength are presented. The test calculation confirms the technical feasibility for operating the dragline-based mine winding machines. The influence of the container capacity on the performance of the winding machine has been determined and the dependence of the economic efficiency of the container technology introduction at the open pit depth has been revealed. Originality. For the first time, on the basis of computer modeling, the parameters of stress distribution on the container wall have been substantiated when performing a strength calculation. It has been determined that the maximum stress in the container wall is 117.52 N/mm2; the principal stress value is 83.85 N/mm2. The safety factor for yield strength is 1.8. The maximum load acting on the structure is 957.5 kgf, which does not exceed the calculated value. Practical implications. The practical importance is to improve mining efficiency, reduce the cost of transporting rocks and ensure automatic container unloading. The use of replaceable containers in open pits can significantly change the formation principles of shovels and transport complexes, increase their performance and the efficiency of shovels in the main processes.

A Novel Design to Optimize Biomechanical Properties of Dental Implant

Objective: The main objective of this study is to evaluate a novel design to optimize dental implant biomechanics. According to this objective, evaluations of the resilient implant design which aimed to mimic biomechanical behaviors of natural tooth have been made and outcomes were compared with natural tooth and standard dental implants with using 3D hyper-elastic finite element analysis. Methods: Models used in the study corresponding to conventional dental implant, natural tooth and resilient dental implant design. Hyperelastic model analysis were performed for close presentment of mechanical behaviors of resilient materials like periodontal ligament and medical silicone. Top values of maximum principal stress, minimum principal stress of surrounding bone and displacement of each model were evaluated under axial and non-axial loading conditions with magnitude of 30N, 80N and 100N. Results: Outcomes of finite element study showed reduction on maximum principal stress and minimum principal stress levels with the use of resilient dental implant comparing to the standard implant model. Standard implant model had been observed notably rigid in all loading conditions compared to the other models. Resilient implant model showed similar biomechanical characteristics with natural tooth model within the limitations of this study. Conclusion: According to finite element analysis results; resilient implant design was able to resolve some biomechanical discrepancies and seem to have adequate biomechanical similarity with natural tooth under both axial and non-axial loading conditions.

Biomechanical Behavior of Narrow Dental Implants Made with Aluminum- and Vanadium-Free Alloys: A Finite Element Analysis.

Titanium (Ti) alloys used for narrow dental implants usually contain aluminum (Al) and vanadium (V) for improved resistance. However, those elements are linked to possible cytotoxic effects. Thus, this study evaluated the biomechanical behavior of narrow dental implants made with Al- and V-free Ti alloys by the finite element method. A virtual model of a partially edentulous maxilla received single implants (diameter: 2.7 and 2.9 mm; length: 10 mm) at the upper lateral incisor area, with respective abutments and porcelain-fused-to-metal crowns. Simulations were performed for each implant diameter and the following eight alloys (and elastic moduli): (1) Ti-6Al-4V (control; 110 GPa), (2) Ti-35Nb-5Sn-6Mo-3Zr (85 GPa), (3) Ti-13Nb-13Zr (77 GPa), (4) Ti-15Zr (113 GPa), (5) Ti-8Fe-5Ta (120 GPa), (6) Ti-26.88Fe-4Ta (175 GPa), (7) TNTZ-2Fe-0.4O (107 GPa), and (8) TNTZ-2Fe-0.7O (109 GPa). The implants received a labially directed total static load of 100 N at a 45° angle relative to their long axis. Parameters for analysis included the maximum and minimum principal stresses for bone, and von Mises equivalent stress for implants and abutments. Ti-26.88Fe-4Ta reaches the lowest maximum (57 MPa) and minimum (125 MPa) principal stress values, whereas Ti-35Nb-5Sn-6Mo-3Zr (183 MPa) and Ti-13Nb-13Zr (191 MPa) models result in the highest principal stresses (the 2.7 mm model surpasses the threshold for bone overload). Implant diameters affect von Mises stresses more than the constituent alloys. It can be concluded that the narrow implants made of the Ti-26.88Fe-4Ta alloy have the most favorable biomechanical behavior, mostly by mitigating stress on peri-implant bone.

Vlerësimi i stresit të shfaqur në nofullën e sipërme nga vidat ortodontike nga çeliku dhe zirkoni

This research aims to evaluate the pressure exerted on the upper jaw by steel and zirconium orthodontic screws using finite element analysis. Based on this, two working models were built in which the mechanical processing and dimen- sions of the orthodontic screws were not changed, and two orthodontic screws were placed from the biomaterial steel and zircon. In this study, a scenario of a case treated with extraction was selected, in which the first premolar was extracted, and the canine retraction was performed on continuous arches (steel 0.0016 x 0.0022) and with brackets of 0.0018’’ slot size. Orthodontic screws is placed between the second premolar and the first molar. A closed spring is suspended from the canine in the direction of or- thodontic screw, which applied a force of 1N. Referring to the achieved results, the value of the maximum principal stress (Pmax), in the cortical bone, was identified in or- thodontic screw made of steel, i.e., zirconium. While the value of the maximum principal stress (Pmax), in trabecu- lar bone, has been identified in steel and zirconium. Based on the conclusions of this research, zirconium may also be used for the production of orthodontic screws.

Finite element analysis of coronoid prostheses with different fixation methods in the treatment of comminuted coronoid process fracture

BackgroundComminuted fractures of the coronoid process significantly compromise the stability and function of the elbow joint. Reconstruction of the coronoid process with a prosthesis has been suggested as an alternative to restore the architecture. The purpose of this study was to investigate the strength and stability of various methods for the fixation of a coronoid prosthesis by finite element analysis.Materials and methodsA coronoid prosthesis was designed based on the morphological information from computed tomography images acquired from 64 subjects in whom the top 40% of the coronoid process height was replaced. Four methods for the fixation of the prosthesis were suggested: (1) a double 2.0-mm fixation bolt, anterior to posterior; (2) a double 2.5-mm fixation bolt, anterior to posterior; (3) a single 4.0-mm fixation bolt, posterior to anterior; (4) a single 4.5-mm fixation bolt, posterior to anterior. The integrated prosthesis-bone constructs were analyzed via the finite element analysis of 10 simulated proximal ulna models with loading applied along the axis of the humerus and with three different elbow flexion angles (30°, 90°, and 130°). The maximum principal stress and the total deformation were quantified and compared.ResultsA coronoid prosthesis was developed. The maximum principal stress of the fixation bolts occurred around the neck of the fixation bolt. For a comparison of the strengths of the four fixation methods, the maximum principal stress was the lowest for fixation using a single 4.5-mm fixation bolt. The value of the maximum principal stress significantly decreased with increased elbow flexion angle for all fixation methods. The maximum deformation of the fixation bolts occurred at the head of the fixation bolt. For a comparison of the maximum deformations in the four fixation methods, the maximum deformation was the lowest for fixation using a single 4.5-mm fixation bolt. The value of the maximum deformation significantly decreased with increased elbow flexion angle for all fixation methods.ConclusionsThe present study suggested that fixation of a coronoid prosthesis with a single 4.5-mm fixation bolt from posterior to anterior is an excellent option in terms of the strength and stability.Level of Evidence Experimental study.

New interconnector design optimization to balance electrical and mechanical performance of solid oxide fuel cell stack

Mechanical stability and integrity are the pre-requisites for the long-term stable high power output of solid oxide fuel cell (SOFC) stacks. However, most of the previous research concentrated on improving the electrochemical performance of SOFC stacks, while the mechanical stability is rarely studied. In this study, a three-dimensional electro-thermo-mechanical coupled model is established to study the impact of interconnector (IC) structure on electrical performance and mechanical stability of SOFC simultaneously. It reveals that IC design with discrete ribs can enhance the maximum power density by up to 12.96%. The maximum principal stress value of positive electrode-electrolyte-negative electrode (PEN) is slightly influenced by IC design, while the stress distribution characteristic is obviously dominated by geometrical structure of IC. Compared with symmetrically arranged ICs at anode and cathode side, the unsymmetrical IC design with regularly discrete cubic, staggered discrete cubic, and discrete cylindrical ribs at cathode side and traditional IC design at anode side can respectively decrease the thermal stress of IC by 19.31%, 6.39%, and 12.09%, while the thermal stress of IC can be further released by 29.44% and 16.44% by rounding the corners of regularly arranged, and staggered distributed cubic ribs. By using new IC design, the failure probability of PEN is reduced by up to 28.97%, while increased by 8.37% only for the case with traditional IC at anode side and staggered cubic ribs at cathode side. To balance the electrical power output and mechanical stability, the discrete cylindrical ribs and discrete cubic ribs with rounded corners are better choices.

Finite Element Analysis of an Implant-Supported FDP with Different Connector Heights

All-ceramic fixed dental prostheses (FDPs) tend to fracture in the connector areas, due to the concentration of tensile stresses. This study aimed to evaluate the role of connector height on the stress distribution of a posterior three-unit implant-supported all-ceramic FDP using finite element analysis (FEA). Two titanium dental implants, their abutments, screws, and a three-unit all-ceramic FDP were scanned using a micro-CT scanner. Three 3D models with altered distal connector heights (3, 4, and 5 mm) were generated and analyzed on ABAQUS FEA software. The maximum principal stress values in MPa observed for each model with different connector heights and their respective locations (MA = mesial abutment; DA = distal abutment; F = framework; V = veneer) were: 3 mm—219 (MA), 88 (DA), 11 (F), 16 (V); 4 mm—194 (MA), 82 (DA), 8 (F), 18 (V); 5 mm—194 (MA), 80 (DA), 8 (F), and 18 (V). All the assembled models demonstrated the peak stresses at the neck area on the mesial abutments. The connector height had a significant influence on the stress distribution of the prosthesis. The models with higher distal connectors (4 and 5 mm) had a lower and more uniform distribution of maximum principal stresses (except for the veneer layer) when compared with the model with the smallest distal connector.

In-situ stress of coal reservoirs in the Zhengzhuang area of the southern Qinshui Basin and its effects on coalbed methane development

In-situ stress is a critical factor influencing the permeability of coal reservoirs and the production capacity of coalbed methane (CBM) wells. Accurate prediction of in-situ stress and investigation of its influence on coal reservoir permeability and production capacity are significant for CBM development. This study investigated the CBM development zone in the Zhengzhuang area of the Qinshui Basin. According to the low mechanical strength of coal reservoirs, this study derived a calculation model of the in-situ stress of coal reservoirs based on the multi-loop hydraulic fracturing method and analyzed the impacts of initial fractures on the calculated results. Moreover, by combining the data such as the in-situ stress, permeability, and drainage and recovery data of CBM wells, this study revealed the spatial distribution patterns of the current in-situ stress of the coal reservoirs and discussed the impacts of the in-situ stress on the permeability and production capacity. The results are as follows. (1) Under given fracturing pressure, longer initial fractures are associated with higher calculated maximum horizontal principal stress values. Therefore, ignoring the effects of the initial fractures will cause the calculated values of the in-situ stress to be less than the actual values. (2) As the burial depth increases, the fracturing pressure, closure pressure, and the maximum and minimum horizontal principal stress of the coal reservoirs in the Zhengzhuang area constantly increase. The average gradients of the maximum and minimum horizontal principal stress are 3.17 MPa/100 m and 2.05 MPa/100 m, respectively. (3) Coal reservoir permeability is significantly controlled by the magnitude and state of the current in-situ stress. The coal reservoir permeability decreases exponentially with an increase in the effective principal stress. Moreover, a low lateral pressure coefficient (less than 1) is associated with minor horizontal compressive effects and high coal reservoir permeability. (4) Under similar conditions, such as resource endowments, CBM well capacity is higher in primary structural coal regions with moderate paleotectonic stress modification, low current in-situ stress, and lateral pressure coefficient of less than 1.