Equivalent Stress Values Research Articles

Numerical simulation analyses of single lap joints for wood-PE composites formed with epoxy and acrylic ester adhesives

Wood powder/polyethylene composites (WP/PE) were surface treated by plasma discharge and bonded with epoxy resin and acrylic ester adhesives, respectively. The finite element model of the single lap bonded joints of WP/PE was established through the elastic-plastic finite element method, and the influences of adhesive and lap length on the stress distribution in the adhesive joints were analyzed. The results showed that polar oxygen-containing groups were introduced to the WP/PE surface with the plasma treatment, which improved the bonding properties. The peak values of Mises equivalent stress, peel stress, and shear stress of the bonded joints were mainly concentrated at the end of the bond joint. The peak values of the stress in the lap zone of the high-modulus epoxy resin-bonded joints were higher than those of the low-modulus acrylic ester-bonded joints. With an increased length of the joints, the Mises equivalent stress peak value at the end increased slightly, the peeling stress peak value decreased slightly, and the shear stress peak value changed little. The elastic modulus of the adhesive had a great influence on the stress distribution, and the change in the lap length was not remarkable enough to improve the stress distribution of the adhesive joint.

Investigation of the effect of relative thickness (t0/d0) on the formability of the AA6061 tubes during free bending process

3D free bending technology is a fabrication technology that has drawn more and more attention all over the world in recent years. During the free bending process, the relative thickness (t0/d0) has a great impact on stress–strain distribution and the movement of the neutral layer, thus further affecting the formability and cross-section distortion of the tube. In this study, relative thickness (t0/d0) were set as 0.033, 0.067, 0.1 and 0.133, respectively. A mechanical analysis model was built to analysis the equivalent stress distribution and the displacement of the strain neutral layer (ξ), and the reliability of the theoretical model was verified. The results showed that the equivalent stress is the lowest and its distribution is the most uniform when the relative thickness (t0/d0) was set as 0.067, which leads to the best formability under all conditions. The peak values of equivalent stress under all conditions appear at the 10° cross-section and the 150° cross-section, respectively, which leads to the thickness of the inner and outer tube changes dramatically. Due to the effect of feeding force which increases the compressive stress of the inner tube and reduces the tensile stress of the outer tube correspondingly, the equivalent stress of the inner tube was higher than the values of the outer tube at the same positions. The displacement of the strain neutral layer (ξ) decreases with the increase of the initial thickness of the tube. The lowest values of ellipticity of 3.48% and 2.85% are reached at the two typical cross-sections when the relative thickness is 0.133.

Masonry wall behaviour under explosive loading

This study is based on the data from an experimental investigation of masonry wall behaviour under blast loading. It includes an overview of some crucial aspects dealing with the numerical modelling of brick wall failure under such loading. The masonry walls exposed to the actual and a computational blast wave action are examined. The brittle behaviour of two-phase masonry is described utilising a VUMAT user subroutine in Abaqus Explicit code. The presented description is novel and fully introduced by the authors. The brittle behaviour of masonry includes material damage and base on the implemented equivalent stress value. Moreover, the initial properties are introduced by an additional laboratory dynamic measurement both phases of the masonry. The numerical response of this obstacle is preliminarily verified during laboratory tests, including the strain rate effect, using a Split Hopkinson Pressure Bar. The explosive loading is presented by a rapid pressure wave which is propagated through the ambient air. This complex experiment is implemented numerically mixing newly developed material response inside the eulerian domain described by equations of the state for the air and explosive respectively.The actual experiments are performed using masonry walls for close-in explosions. Finally, the numerical studies are compared with the experiments, resulting in pressure-impulse curves and masobnry failure.

Ti-15Mo Alloy Decreases the Stress Concentration in Mandibular Angle Fracture Internal Fixation Hardware.

Comparison of the mechanical stability of 2.0 plates made of commercially pure titanium (cpTi) and a titanium-molybdenum (Ti-15Mo) alloy and two methods of internal fixation employed mandibular angle fractures, using 3D finite element analysis. Four groups were evaluated. For the cpTi: group Eng 1P, one 4-hole plate and 4 screws 6mm long, in the tension zone of the mandible; group Eng 2P, two 4-hole plates, one in the tension zone of the mandible and the other in the compression zone, both were fixed with 8 screws 6mm long. The same groups were created for the Ti-15Mo alloy. A 100N compressive load was applied to the occlusal surface of the mandibular first molar on the plated side. When considering the von Mises equivalent stress (σ vM) values for the comparison between both groups with one plate, a decrease of 10.5% in the plate and a decrease of 29.0% in the screws for the Ti-15Mo group was observed. Comparing the same groups with two plates, a decrease of 28.5% in the screws was shown for the Ti-15Mo alloy group. No significant differences were observed when considering maximum and minimum principal stresses (σ max, σ min), and maximum principal strain (ε max) to the mandibular bone. The Ti-15Mo alloy plates substantially decreased the stress concentration in the screws for both internal fixation techniques and in the plate for the Ti-15Mo 1 plate group. From a clinical standpoint, the use of Ti-Mo alloy with reduced stiffness will decrease the stress shielding between the hardware and bone, influencing the outcome of the treatment.

FEM analysis in excellent cushion characteristic of ostrich (Struthio camelus) toe pads.

African ostrich (Struthio camelus) is the largest and fastest extent bipedal animal. The ostrich mainly relies on the 3rd toe to support the entire body under high-speed motion. The short and severe impact concentrated on the limited area would produce tremendous momentary internal stress and strain, which may contribute to the phalanges disloaction, soft tissue damage and the like. The vibration and excessive negative acceleration caused by the ground reaction force also affect the stability of the touching process. Therefore, ostrich toe pads are required to have excellent cushion characteristics. However, current studies often explains the cushion properties by analyzing the macro-microscopic structure of the pad organism, and there is a paucity of research on its biomechanical behaviour. Consequently, from the perspective of multi-layer structure and biomaterial assembly, this study aims to explain the biomechanical characteristics of the ostrich toe pads by FEM (Finite Element Method) analysis. Based on results, we deem that the ostrich toe pad could absorb energy and reduce vibration effectively. Firstly, the multi-layer structure of the pads make the stress and strain decay from outside to inside. Secondly, the minimal response frequency of the pad is 164.22 Hz, making it effectively avoid resonance phenomenon. Finally, the composite material model has the best performance in decreasing the negative acceleration peak value, the impact force peak value and the maximal equivalent stress value at velocities of 0.669 m/s and 1.339 m/s. These results help to further understand the buffer mechanism of the ostrich toe pad, and also have important inter-species reference value for the pathogenesis of human foot soft tissue injury.

MATHEMATICAL SUBSTANTIATION OF THE USE OF DIFFERENT TYPES OF CLAMMERS DURING THE RESTORATION OF THE DENTITION WITH DOUBLE-SIDED DISTAL DEFECTS AND THE DEFECT INCLUDED IN THE FRONTAL AREA BY REMOVABLE PROSTHETICS

The basic conditions that ensure good functional qualities and durability of prosthetic structures from the point of view of biomechanics, undoubtedly include an optimal way of fixing a partial removable prosthesis, which consists in the correct choice of the clamping system that ensures reliable fixation of the prosthesis in the given position and at the same time causing a minimum of harm supporting teeth, as well as the most rational distribution of occlusal loads transmitted to the supporting tissues, since it is these factors that determine the durability functioning dentures. The purpose of biomechanical studies is to analyze the stress-strain state of the supporting teeth of partial removable prostheses replacing the included and terminal defects of the dentition when fixing the prosthesis on the supporting teeth with the help of holding and supporting-retaining clamps. The studies were performed on a model of the mandible with overall dimensions of the cross section corresponding to some average dimensions. The first volumetric finite element model was developed to study the stress-strain state of periodontal ligaments of supporting teeth and supporting gingival tissues when the incomplete and bilaterial end defects of the dentition were replaced (1 class 1 subclass by Kennedy) of the mandible by a removable denture with fixation by retaining clamps on the canines and the first premolars. The second volumetric finite element model is designed to study the stress-strain state of periodontal ligaments of supporting teeth and supporting gum tissues when the included and two-sided end defects of the dentition of the lower jaw are replaced by a removable clasp prosthesis with fixation of support-retaining clamps on canines and first premolars with support arms of clamps from the distal sides of premolars. As a result of the studies performed, the following conclusions can be drawn: In both considered variants fixation of removable clasp prostheses loaded with maximum values of equivalent stresses in the periodontium of the supporting teeth is localized at the apex of the alveolar ridge, which indicates the transfer of the "clutching" supporting teeth of the clasp prosthesis. The maximum values f equivalent stresses in the periodontitis of the supporting teeth during fixation of the removable clasp prosthesis by the support-retaining clamps on the canines and the first premolars exceed the corresponding values of the equivalent stresses for the case of fixing the prosthesis with retention clamps by 30-140%! With an increase in gum compliance, the values of equivalent stresses in the periodontitis of the supporting teeth during fixation of the removable clasp prosthesis by the retaining clasps vary insignificantly within 25%, and an increase in the corresponding equivalent stresses with the use of support-holding clasps may be 65%. In order to ensure the maximum sparing regimen of periodontal tissues of supporting teeth and as a result - the possibility of the most prolonged use of the prosthesis without loosening of the supporting teeth, it seems more expedient to give preference to the use of clasp prostheses with the fixation of the retaining clasps.

Research of the influence of highcarbon steel wire drawing speed on stresses and deformations on wire cross section

The parameters of wire production affecting the distribution of residual stresses and strains on the wire cross section are considered. It is determined that the modes of coarse drawing can affect the complex of mechanical properties of thin wire due to the uneven distribution of equivalent stresses and strains. The rough drawing speed is chosen as the investigated parameter.The effect of the coarse drawing rate of high-carbon steel wire on the distribution of equivalent residual stresses and strains over the wire cross section is studied by numerical simulation of wire drawing at different speeds by the finite element method. The values of equivalent residual stresses for the selected drawing route along the wire cross-section zones are determined. The analysis of the equivalent stress distribution over the wire cross section is made.It is shown that the increase in the speed of coarse drawing increases the uniformity of the distribution of equivalent residual stresses, does not have a negative effect on the deformed state of the wire, increases the absolute values of equivalent residual stresses, slightly reduces the absolute values of residual deformations.

Analysis of Pressure Fluctuation and Stress Deformation in Reverse Generation of Large Vertical Axial Flow Pump

In order to study the stability of the reverse generation of a pumping station in the eastern route of the South to North Water Transfer Project, a full numerical simulation of the flow passage was carried out to study the pressure fluctuation and the stress distribution law in the reverse generating condition. At the inlet of the guide blade, the monitoring points are set up in three sections of the inlet and outlet of the runner. The calculation results show that the pressure pulsation at the outlet of the wheel is the largest, the pressure pulsation between the guide vane and the wheel is the second, and the pressure pulsation at the inlet of the guide blade is the smallest. At the inlet and outlet of the impeller, the blade is dominated by the frequency. The flow state is uneven, and the pressure fluctuating from the hub to the rim gradually increases. The results of fluid solid coupling show that the stress mainly concentrates on the blade pressure surface and the root of the suction surface, and the maximum equivalent stress appears at the impeller root of the suction surface of the blade. The maximum equivalent stress value is in the safety range of the blade material, and does not affect the life and failure of the turbine running unit.

Effect of platform switching on peri-implant bone: A 3D finite element analysis

Statement of problemA consensus regarding the effects of platform switching on peri-implant marginal bone levels is lacking. Finite element studies have reported contradictory results. PurposeThe purpose of this finite element analysis study was to evaluate stress distribution in platform-switched (PS) and platform-matched (PM) implants and their surrounding bone. Material and methodsAn implant (4.5×11 mm) was modeled and screwed into a human mandibular bone block using a computer-aided design (CAD) software program. Two separate models were generated: (1) PM, 4.5-mm implant with 4.5-mm-wide abutment and (2) PS, 4.5-mm implant with 3.5-mm-wide abutment. Implant components were modeled with linear isotropic properties and bones with anisotropic properties. Vertical (200 to 800 N) and oblique (50 to 150 N) forces were applied to each model to simulate occlusal loads. Linear elastic analysis was performed using ANSYS Workbench 16. von Mises equivalent stresses in the implant assemblies and peri-implant bone were calculated and compared with independent samples t test (α=.05). Resultsvon Mises equivalent stress values under simulated axial and nonaxial occlusal loads were lower for PM than for PS implant assemblies. However, the differences were not statistically significant. Stress within the peri-implant bone was significantly higher for the PM group than for the PS group (P<.001). ConclusionsPlatform switching decreased stress within peri-implant bone and may help limit marginal bone resorption.

Closure of the hip joint capsule defect with a propylene mesh. Clinical and biomechanical research

Dislocation of the femoral component of the endoprosthesis is one of the most common complications after hip total arthroplasty. The best way of prevention is to prevent the development of primary instability. Even with the proper positioning of endoprosthesis components, there are dislocations associated with the weakness or defect of the capsular-connective structures of the joint. Today, a lot of ways have been developed to strengthen and restore the posterior structures of the capsule of the hip joint with the help of auto and allomaterials, differing in the method of fixation and physical and chemical characteristics.The paper proposes a method of restoring and strengthening the posterior structures of the capsule using polypropylene mesh implants. Objective: to construct a model of the hipjoint capsule after capsulotomy with the help of the specialized software program and to determine the hardness of the defect closed with a polypropylene mesh. Methods: the study was made in a software complex based on the finite element method. A calculation model was constructed consisting of capsule and endoprosthesis femoral head. Two methods of sewing the dissected capsule were studied: seam thread and polypropylene mesh. In the control model, the capsule was not fixed. Results: pictures of the distribution of stress-strain state in the system «endoprosthesis – joint capsule» were obtained. Conclusions: underthe conditions of the kinematic loading of the model, the smallest sizes of the capsule cut opening are in case of its closure with the mesh. In the case of thread, they were 8.5 % higher. The values of equivalent stresses in the model with the mesh were the largest: in the capsule of the joint by 23.8 %, the endoprosthesis head — by 60.4 % compared with the thread fixation. The obtained results indicate that the mesh model is more rigid.

Short dental implant biomechanics in the mandible bone tissue

The aim of the study was to assess the stress-strain state of «short dental implant - lower jaw bone tissue» system in the its osseointegration area under different stress options, of an experimentally developed bone tissue model. Using the finite element analysis method, we investigated a three-dimensional model of an implant with 5.0 mm diameter and 6.5 mm height integrated into the quasi-elastic model of the lower jaw segment with a total deformation modulus of 14 400 MPa and a Poisson's ratio of 0.24 for the cortical layer, for the spongy layer, the general deformation module of 0.2 MPa, Poisson's ratio 0.4. The values of equivalent stresses according to the Genki-Mises criterion for the implant body amounted to 50-76 MPa in the cervical region from the end and inner sides of the implant interface and along the upper edges of the thread edges in the upper third of the implant. Minimum values of 0.1-20 MPa are distributed over the implant body from its cervical part to the top in the lower 2/3. The equivalent von Mises stresses in the bone at the joints of the threaded implant part are minimal - 5-15 MPa. Values of shear stresses in the bone - 2 - 3 MPa, normal vertical stresses - up to 5-13MPa, main tensile stresses - up to 20 MPa, compressive stresses - up to 30-40 MPa. Thus, installing this implant in such model, should not occur irreversible deformations. In our opinion, the structural stability is ensured by the bone tissue features architectonics within 3 mm of the cortical layer, where the maximum stress is redistributed in the future throughout the cortical bone, which can expand the indications for short dental implants use, especially in patients with a limited alveolar bone volume.

Construction of limitation diagrams for truss core stiffness and strength parameters

A truss-core sandwich panel is a promising load-bearing element of lightweight high-stiffness structures. The use of this element in load-bearing structures makes it necessary to know its mechanical and strength characteristics depending on the structure and properties of a typical core cell. Currently, the available results are not sufficient to assess the strength due to the complexity of taking into account all the features of the loading of the core structure in the form of repeated pyramidal and tetrahedral unit cells most common in the production of lightweight truss cores. In the research of the strength properties of a unit cell, it is assumed that the destruction of the truss structure may occur when the yield stress in the material of the core is exceeded or if buckling takes place. The scheme of destruction of the truss structure in the cell will depend on the combination of unit cell equivalent stress values. The critical core buckling stress is usually less than the yield stress. Therefore, when co block diagrams of equivalent stress constraints are constructed, one can observe a rather complex picture of the change in the limit values depending on the azimuthal angle in the plane of the cell base. To analyze limitation diagrams, the easiest way is to introduce a parameter determined by the ratio of the critical buckling stress to the magnitude of the yield stress of the core material. In this case the limitation diagrams will not depend on the specific critical absolute values of stresses, but on their relationship; the nature of the diagrams will not depend on the density of the core. The design parameters of the core are determined on the basis of the construction of other diagrams for the given (required) values of generalized compressive stiffness, transverse shear, generalized critical compressive stresses and transverse shear of a unit cell of the sandwich structure which depend on the relative density of the truss core. The combination of these two constraint diagrams gives a more complete picture of the degree of optimality of the truss core design parameters.

Equivalent Uniaxial Cyclic Tensile Stress as an Energy Characteristic of Metal Fatigue under Multiparameter Loading

A concept of the equivalent stress as an energy characteristic of the material ability to resist deformation and fatigue cracking is introduced based on the principles of physical mesomechanics and synergetics. It is shown that the tensile curve of the material, the fatigue life diagram, and the kinetic curve for fatigue crack growth obtained under common experimental conditions can be considered as unified or "master" diagrams for material behavior description under multiparameter loading. Examples of determining the equivalent stress value and correction functions on the basis of the introduced concept are given for fatigue specimens subjected to biaxial cyclic loading and for in-service fatigue specimens of aircraft structures.

Evaluasi Beton Bertulang terhadap Perlakuan Panas (Tinjauan pada Tegangan Tarik dan Modulus Elastis Tulangan Baja Lateral)

Fires phenomena have made demands to a building planner to protect, evaluate, and predict the performance of a building after a fires process. The main attention was given to the type of material, in this case, the reinforced concrete that used as a structural element, which due to heating and cooling cycles are alternating, and then the elements of reinforced concrete structures undergo a phase change both in the physical and chemical. This research related to the evaluation of reinforced concrete quality with a focus on heat treatment and reviews tensile stress and elastic modulus of the steel reinforcement. Specimens used in this study was a model of the reinforced concrete beam with a concrete cover types K250 and K300, 7.5 mm of rebar diameter and 2 cm of concrete cover thickness. Heat testing performed after 28 days of treatment with closed combustion in the furnace (heat chamber) without loading at a temperature of 1000ºC for 10 hours, holding time for 1 hour, and slows cooling for 10 hours. In normal specimens, the tensile test results show an equivalent stress value of 324.12 MPa. In specimens heat treatment with a concrete cover of K250, the tensile stress value was 259.52 MPa, while in the K300 was 263.76 MPa. Optimum tensile stress value in normal specimens was 568.62 MPa, and in specimens with heat treatment and with the K250 concrete cover was 473.74 MPa and amounted to 494.41 MPa for K300. The value of tensile fracture stress in normal specimens amounted to 552.52 MPa, and in specimens with heat treatment and with the K250 concrete cover amounted to 461.52 MPa and amounted to 465.24 MPa for K300. Elastic modulus values for normal specimen was 1,612,963.61 kg/cm2, while in specimen heat treatment with the K250 concrete cover was 1,287,888.05 kg/cm2 and was 1,311,545.42 kg/cm2 for K300.

Effect of the screw type (S2-alar-iliac and iliac), screw length, and screw head angle on the risk of screw and adjacent bone failures after a spinopelvic fixation technique: A finite element analysis.

PurposeSpinopelvic fixations involving the S2-alar-iliac (S2AI) and iliac screws are commonly used in various spinal fusion surgeries. This study aimed to compare the biomechanical characteristics, specifically the risk of screw and adjacent bone failures of S2AI screw fixation with those of iliac screw fixation using a finite element analysis (FEA).MethodsA three-dimensional finite element (FE) model of a healthy spinopelvis was generated. The pedicle screws were placed on the L3-S1 with three different lengths of the S2AI and iliac screws (60 mm, 75 mm, and 90 mm). In particular, two types of the S2AI screw, 15°- and 30°-angled polyaxial screw, were adopted. Physiological loads, such as a combination of compression, torsion, and flexion/extension loads, were applied to the spinopelvic FE model, and the stress distribution as well as the maximum von Mises equivalent stress values were calculated.ResultsFor the iliac screw, the highest stress on the screw was observed with the 75-mm screw, rather than the 60-mm screw. The bones around the iliac screw indicated that the maximum equivalent stress decreased as the screw length increased. For the S2AI screw, the lowest stress was observed in the 90-mm screw length with a 30° head angle. The bones around the S2AI screw indicated that the lowest stress was observed in the 90-mm screw length and a 15° head angle.ConclusionsIt was found that the S2AI screw, rather than the iliac screw, reduced the risk of implant failure for the spinopelvic fixation technique, and the 90-mm screw length with a 15° head angle for the S2AI screw could be biomechanically advantageous.

Mobile trailer support arm: modeling and analysis of breakage

Calculation of vehicle elements load is a mandatory operation in the engineering of transport. The paper presents the calculation schemes of the static loading of the lever supports of the mobile hopper of bulk materials and determines internal force factors. The numerical values of equivalent stresses distributed on the lever of the mobile hopper of bulk materials are determined. The visualization of the results of calculating the stresses performed by the classical cross-section method and the finite element method is given. The results of both calculations show that the dangerous zone in the cross section of the lever is the neighbourhood of the hydraulic cylinder attachment. The analysis by the loading method shows the risk of breakage in the place of attachment of the hydraulic cylinder bracket from the side of the support wheel. To eliminate the revealed shortage there are proposals and recommendations given by the authors.

LOADING ANALYSIS ON ALLOY WHEELS TYPE-253 SIZE 6.5 X 15JJ BASED ON SNI 1896:2008 WITH FINITE ELEMENT METHOD

This study analyzes the loading on the model wheel-253 size 6.5 x 15JJ based on SNI 1896: 2008 with finite element method. This load analysis tested the resistance to dynamic radial fatigue on alloy wheels by using load simulation with quasi-static failure mode approach ie failure mode which is independent of time, and its resistance to failure is expressed with strength. Test wheels are said to fail if there is crack (crack) by giving the liquid penetrant. Crack conditions in the simulation can be seen from the stress and elastic strain. The equivalent elastic stress and elastic strain values that occur on the rim must be less than the Ultimate Tensile Stress (UTS) and the elastic strain at break. The properties values for Aluminum A356-T6 material for UTS of 228 N/mm 2 and strain elastic fracture values obtained from a plastic material strain of 0.059 m/m.

Experimental and numerical study of mode-I and mixed-mode fracture of ductile U-notched functionally graded materials

In the present study, ductile fracture of the U-notched samples made from bainitic Functionally Graded Steel (FGS) has been studied experimentally and numerically under the mode-I and mixed-mode conditions. The desired FGS plates were fabricated using the Electro Slag Remelting (ESR) technique. Then, the notched specimens were tested under the three-point bending condition. Effects of both the notch geometry and loading point position have also been investigated. A numerical scheme based on kinematic hardening constitutive model as well as Hollomon's equation has been utilized to define the material response including damage evolution. This numerical scheme is also able to predict the damage initiation point based on a method that uses both the stress triaxiality and equivalent stress values. Moreover, material properties of each point within the graded regions have been specified using the strain gradient plasticity theory, instability point concept and area under stress–strain curve. Comparing the experimental results with the numerical ones shows the capability of the numerical scheme. Also, the critical fracture loads of the notched samples made from FGS show the superiority of the present graded material over the homogeneous one.

ENSURING THE STRENTH OF T-JOINT. STRENGTHENED CONNECTION PIPE

Reliability of the entire system is determined by the reliability of its individual components. So, in pipeline transport, as in any system, it is possible to isolate some problematic ele-ments (sections) characterized by high accident rates. These, of course, include shaped products, in particular, T-joints. Thus, it is extremely important to pay special attention to the issues of improving the design of the connecting parts and the technologies for their installation during the construction and repair of pipelines. The purpose of this article is to present the design of a stabilizing device, namely a strength-ened branch pipe, installed as an intermediate part-insertion in place of the tapping hole into the pipeline. Similar in purpose to the products encountered in practice, there is a certain drawback, which is determined by the structural features of the strengthened pipes. Often at the stage of assembling the joint, it becomes necessary to cut the hole in the main line with a diameter much larger than the inside diameter of the pipeline tap, which in turn adversely affects the strength of the entire joint. The article presents the results of the strength analysis of tee connections made in three different designs: in the classical with the use of a T-type TS (tee-stamped) and on the basis of intermediate reinforcement inserts (reinforced butt joint and reinforced connection pipe). In the course of the research it was established that the design of the strengthened connec-tion pipe allows to reduce the peak values of equivalent stresses in the dangerous zone of the T-joints in comparison with the TS-type tees and the nodes strengthened by the branch pipe by 40-45 % and 15-20 % respectively. Also recommendations are given on the choice of strength characteristics and geometric parameters of the proposed connecting part in determining the bearing capacity of the pipeline.

Effect of finish line level of all ceramic crown on stress distribution within dentin of maxillary central incisor with an abfraction lesion

Purpose: to evaluate by means of three dimensional finite element analysis, the effect of finish line location on stress distribution on dentin of maxillary central incisor affected by abfraction lesion and covered with IPS e. max (Lithium di silicate) crown. Statement of the problem: In some cases of abfraction, the tooth need to be covered with full coverage crown, but, location of finish line may affect dentin integrity. Materials and Methods: 3D finite element model of unprepared maxillary central incisor was made. By deleting method, IPS e.max crown was designed and geometric dimensions of prepared tooth were introduced as the following guidelines, 2 mm incisal reduction, 1.5 mm reduction of labial surface and 1 mm circumferential shoulder finish line. The position of labial finish line was designed in three different levels apical to the upper margin of the abfraction lesion (0.5. 1.0 and 1.5 mm) forming three models to be tested (A, B and C) respectively in addition to unprepared control model. Results: For all tested four models, the calculated stresses with 125° applied load were higher than that with 60° with statistical significant differences. The calculated stresses at the control model in both directions of applied load were lower than that in other tested models (A, B and C) with statistical significant differences. For control model at 125° applied load, Von Mises equivalent stress value was (40.27 MPa), whereas, in case of 60° applied load, was (26.33 MPa). For model (A) where the finish line of IPS e.max crown is established 0.5 mm apical to the upper edge of the abfraction lesion, Von Mises equivalent stress values were (22.14 & 39.68 MPa) respectively. Conclusion: In all tested models, maximum stresses increased with increasing the angle of applied load, and model (B and C) provided more favorable stress distribution than that in model (A).