Finite Element Stress Analysis Research Articles

Failure analysis of a crane gear shaft

This research deals with a teeth failure of a gear shaft that served as a part of shipyard crane drive train. Almost all of the teeth of a spiral bevel gear, part of a larger shaft, fractured during normal operation of the crane. Failure analysis combined experimental and numerical research. Visual inspection was employed to determine the fracture location and crack propagation paths. Microscopy, optical and scanning electron (SEM), was used to inspect damaged surfaces of the teeth, reveal possible flaws and fine microstructure of the material. Type of steel used for manufacturing was determined based on chemical composition of the material obtained using optical emission spectrometer with glow discharge source (GDS) sample stimulation. Further, tensile specimens were extracted from the shaft to test the strength of the steel. Additionally, hardness test was performed. All experimental research suggest it is a case of gear teeth spalling, probably caused by excessive contact stresses. To gain better understanding of the failure process, a 3D numerical model of the gear shaft was built and finite element (FE) stress analysis performed. Analysis showed excessive contact stresses at the teeth contact area. Time-varying meshing stiffness (TVMS), an important gear health condition parameter, is determined via FE procedure for several examples of healthy to gradually damaged gear. Obtained results show how spall propagation influences TVMS and, thus, affects gear performance leading to potential failure.

Finite element stress analysis of a total hip replacement in two-legged standing

Finite element stress analysis of a total hip replacement in two-legged standing

Three-dimensional finite element stress analysis of teeth adjacent to a traumatized incisor.

Dental trauma is the cause of several consequences to the injured tooth. However, the stresses and strains at adjacent teeth non-directly impacted as a possible cause of sequelae are still unknown. The aim of this study was to evaluate the stress distribution in incisors adjacent to an upper central incisor when it suffers a frontal impact in order to identify a potential explanation for sequelae in non-traumatized teeth. A three-dimensional (3D) finite element model of the maxillary central incisors, lateral incisors and canines was created from a cone-beam scan of a patient with normal occlusion. Non-linear dynamic impact analysis was performed, simulating the right central incisor being impacted by a steel ball with a velocity of 10m/s. A functional chewing load (100 N) on the palatal surface of the central incisor was simulated for comparison. Displacements, strains and modified von Mises stresses were calculated for the adjacent teeth. During impact on the central incisor, the adjacent teeth showed root displacement. Considerable stress concentrations were observed on the palatal surfaces, proximal and labial surfaces of teeth adjacent to the traumatized incisor. Stresses in the adjacent teeth were higher than stresses calculated during functional biting. Compressive stresses were concentrated at the proximal areas of the adjacent incisors. High levels of deformation were found in the root dentin of adjacent teeth during the traumatic event. A frontal impact on an anterior tooth generated stresses at the roots of adjacent teeth. These stresses may play a role in clinically observed sequelae of teeth adjacent to traumatized teeth.

Finite Element Stress Analysis of Applied Forces to Implants and Supporting Tissues Using the "All-on-Four" Concept with Different Occlusal Schemes.

The aim of this study was to evaluate stress distributions on implants and alveolar bone due to occlusal load produced during chewing by prostheses prepared according to the All-on-Four concept with different occlusal schemes using a finite element analysis method. On standard jaw models, teeth were set in accordance with the basic standards of canine-guided occlusion, group function occlusion, bilateral balanced occlusion (BBO), lingualized occlusion, and monoplane occlusion schemes. Three-dimensional (3D) images of these models were obtained using a surface scanner. Implants, superstructures, the maxilla, and mandible were modeled in the All-on-Four concept with 3D modeling software. Forces were defined on contacts formed in maximum intercuspation, lateral, and protrusive movement position for all 5 occlusion types. Stress outputs were recorded as maximum and minimum principal stresses (Pmax , Pmin ) and von Mises stress values for the implants. The highest Pmax value for the maxilla was observed in cortical bone in the group function occlusion during lateral movement (15.56 MPa). For the mandible, the highest Pmax value was observed on the cortical bone in maximum intercuspation of lingualized occlusion (72.75 MPa). The highest Pmin value for the maxilla was observed during the lateral movement in group function and for the mandible in BBO (-29.23 and -86.31 MPa, respectively). The lowest stress values were observed with canine-guided occlusion in all related conditions and on all structures. With the limitations of this simulation study, considering stresses on alveolar bone and implants in All-on-Four applications, the use of canine-guided occlusion may be suggested.

Finite element analysis of stresses on adjacent teeth during the traction of palatally impacted canines.

To evaluate stresses on maxillary teeth during alignment of a palatally impacted canine (PIC) under different loading conditions with forces applied in vertical and buccal directions. A three-dimensional finite element model of the maxilla was developed from a cone beam computed tomographic scan of a patient with a left PIC. Traction was simulated under different setups: (1) palatal spring extending from a transpalatal bar (TPB) anchored on the first molars (M1) and alternatively combined with different archwires (0.016 × 0.022-inch; 0.018 × 0.025-inch) with and without engaging second molars and (2) a buccal force against 0.018-inch, 0.016 × 0.022-inch, and 0.018 × 0.025-inch archwires with and without engaging the left lateral incisor (I2). Without fixed appliances, stresses were assumed by M1; with fixed appliances, stresses were distributed on all teeth, decreasing mesially toward the midline. Direct buccal pull exerted most stress on neighboring I2 (19-20% with different wire sizes) and first premolar (12-17%), decreasing distally, along a similar pattern with different archwire sizes. When I2 was bypassed, stresses on adjacent teeth increased only by 3-6%. Higher stresses occurred with the lighter round wire. This first research on stresses on adjacent teeth during PIC traction provided needed quantitative data on the pattern of stress generation, suggesting the following clinical implications: use of distal-vertical pull from posterior anchorage (TPB) as initial movement and when using a buccal force, bypassing the lateral incisor and using heavier wires that would minimize side effects.

Dynamical modeling of manipulation process in Trolling-Mode AFM

Dynamical lumped modeling of Trolling-mode AFM in manipulation of bio-samples is presented. The combination of high accuracy and compatibility with physiological conditions makes AFM a unique tool for studying biological materials in liquid medium. However, AFM microcantilever suffers from severe sensitivity degradation and noise intensification while operating in liquid; the large hydrodynamic drag between the cantilever and the surrounding liquid overwhelms the tip-sample interaction forces that are important in controlling the process. Therefore, an appropriate nanoneedle should be long enough to keep the cantilever out of liquid medium and short enough to be able to transmit the required force to push nanoparticle. Nonetheless, a long nanoneedle may deflect under the pushing force; therefore, its bending deflection should be accounted for in governing equations. Moreover, analytical and finite element stress analysis of nanoneedle and cantilever is performed to assure about their selected material and geometry. JKR theory is utilized to model contact mechanics between the needle/surface and the particle. Drag and meniscus forces are used to model the liquid media. Governing equations are solved using ODE45 and the system behavior is simulated. Critical conditions of sliding including critical time and force are obtained and changes of pushing force, needle deflection and indentation depths are illustrated. Also, effects of velocity variations are observed. Then, different heights for nanoneedle are tested and an appropriate one is selected for our purpose (to keep the needle out of liquid and transmit the force appropriately). The simulation is repeated for various biological particles and their behaviors are studied. At the end, the present simulation is validated through comparing the results with a previous work. This comparison shows that the simulation is reliable for the intended purpose.

Hydraulic torque wrench adapter failure analysis

Abstract Flaw appearance, crack occurrence and consequential failures are of serious concern in any mechanical design process. Once failed, parts can be analysed in order to determine the causes of failures. Therefore, failure analysis proves to be a valuable tool in design improvement. This research deals with a failure of hydraulic torque wrench square drive adapter. It is a 1.5″ size adapter capable of handling 15,500 Nm torque. There has been a considerable number of identical failures so an attempt was made to determine the cause. Failure analysis was performed using experimental and numerical approach. Visual examination revealed the location and path of the fracture, while optical microscopy was used to inspect fracture surface and reveal possible flaws. Detailed scanning electron microscopy (SEM) examination at suitable magnifications was employed to characterize fine microstructure of the fractured surface and reveal flaws that served as crack initiation points. Chemical composition of the material was determined using optical emission spectrometer with glow discharge source (GDS) sample stimulation. Maximum tensile strength of the material was derived from the performed hardness test results. Further research employed finite element (FE) analysis to determine stress levels of a loaded square drive adapter. Excessive stress concentration is noticed at a point where actual crack initiated. Optimized design is proposed, capable of handling declared torque. FE stress analysis of optimized square adapter revealed acceptable stress levels and shifting of stress concentration point further along the adapter. Conclusion is that the manufacturer needs to reconsider actual design in order to avoid future failures.

Three-dimensional analysis of unanticipated behavior of a deep excavation

A three-dimensional (3D) effective stress finite element analysis, modified to account for hydrofracturing and gassy soil behavior, is used to examine the potential for the venting of water and gas from a bedrock aquifer and through 13–14 m of low permeability clayey silt between the base of the excavation and the bedrock following excavation to about 24 m in an approximately 40 m thick clayey silt deposit. The clayey deposit contained sand lenses with dissolved gas. The analysis predicts that the exsolution of this dissolved gas, caused by a reduction in total stress due to the excavation, results in liquefaction of the sand in the lenses and consequent lateral deformations of the side slopes. The analysis predicts hydrofracturing through the remaining clayey silt when the excavation reaches its final depth and this explains the venting of water and gas from the underlying aquifer that was observed above a local bedrock high. The presence of gassy sand lenses created weak zones within the clayey deposit that influenced the path of the hydrofracturing. However, the analyses suggest that, for the depth of excavation and bedrock elevation examined, hydrofracturing and subsequent venting would have occurred even if there had been no sand lenses.

Comparative study between conventional and mini dental implants of different diameters supportin g mandibular overdentures. A finite element stress analysis study

This study was conducted to provide an understanding of the biomechanical behavior ofdifferent diameters MDIs and compare it with conventional diameter implants when supportingan overdenture . Three different models were designed .The first model has two standard diameterimplants (3.8x12mm) (D1), the second (D2) has 2 mini-dental implants (2.4x12mm) and the thirdmodel (D3) has 2 of ultra-small diameter (1.8 x 12mm) all implants were placed at canines region.3D finite elements stress analysis was performed to evaluate biomechanical situation in both theimplants and the peri-implant bone under vertical and oblique loading of the overdentures. It can beconcluded that the stress values affecting the peri-implant bone and the implants are reciprocal todental implant diameter and the use of MDIs as overdenture abutments should be limited to caseswith limited bone quantity.

Finite element stress analysis on the effect of an implant alignment, offset and load direction in the posterior mandible

Finite element stress analysis on the effect of an implant alignment, offset and load direction in the posterior mandible

A new method for the treatment of unilateral posterior cross-bite: a three-dimensional finite element stress analysis study

BackgroundStress relieving corticoto mies during the treatment of maxillary expansion are needed in adult patients.MethodsThree-dimensional (3D) finite element model was prepared, and finite element analysis was processed to evaluate the stress distributions within the skull and maxillary teeth during surgically assisted rapid maxillary expansion (SARME) treatment.ResultsExpansion forces generated more stress on the corticotomy-applied part of the maxilla. The stress levels decreased dramatically above the corticotomy line.ConclusionAsymmetric transveral maxillary expansion might be achieved from a symmetric force generating screw during SARME treatment. SARME osteotomies may concentrate the stress in the expanding maxilla and reduce the pain in other parts of the cranium.

Mesh convergence study and estimation of discretization error of hub in clutch disc with integration of ANSYS

Structural analysis is an essential tool for design engineers. Mesh generation is the basic step in any simulation. In practice of finite-element stress analysis, the engineer first needs to know if key stresses are converging, and second if they have converged to a reasonable level of accuracy. In order to achieve results that are reliable when using the finite element method, it must be ensured that an acceptable mesh is used with respect to the shape and size of the elements. Mesh quality and mesh density values are directly linked with the solution accuracy. This paper presents a mesh convergence study on the hub which is the most challenging part in the automotive clutch disc assembly. Finite element analysis convergence defines the relationship between the number of elements or DOF and the analysis accuracy. Discretization error is key concept for the study of mesh convergence study, also discretization is function of number of degree of freedom of model. A detailed comparison of different results is carried out using convergence test based on displacement and energy norms. Error between exact and ANSYS results are compared in this study.

Photoelastic and finite element stress analysis reliability for implant-supported system stress investigation

Aim: To compare the reliability between photoelastic and finite element (FE) analyses by evaluating the effect of different marginal misfit levels on the stresses generated on two different implant-supported systems using conventional and short implants. Methods: Two photoelastic models were obtained: model C with two conventional implants (4.1×11 mm); and model S with a conventional and a short implant (5×6 mm). Three-unit CoCr frameworks were fabricated simulating a superior first pre-molar (P) to first molar (M) fixed dental prosthesis. Different levels of misfit (µm) were selected based on the misfit average of 10 frameworks obtained by the single-screw test protocol: low (<20), medium (>20 and <40) and high (>40). Stress levels and distribution were measured by photoelastic analysis. A similar situation of the in vitro assay was designed and simulated by the in silico analysis. Maximum and minimum principal strain were recorded numerically and color-coded for the models. Von Mises Stress was obtained for the metallic components. Results: Photoelasticity and FE analyses showed similar tendency where the increase of misfit generates higher stress levels despite of the implant design. The short implant showed lower von Mises stress values; however, it presented stresses around its full length for the in vitro and in silico analysis. Also, model S showed higher µstrain values for all simulated misfit levels. The type of implant did not affect the stresses around pillar P. Conclusions: Photoelasticity and FEA are reliable methodologies presenting similarity for the investigation of the biomechanical behavior of implant-supported rehabilitations.

Development of cone-wedge-ring-expansion test to evaluate the tensile HOOP properties of nuclear fuel cladding

We report the development of a cone wedge ring expansion test method to determine the tensile hoop properties of irradiated nuclear fuel cladding in a hot cell. A closed-form solution was developed to explicitly relate the hoop stress σθ to the axial piston loading using the scale factor χ and the shear stress correction factor α, where the χ and α factors are used to convert the applied piston load and the radial dilatation of the ring into the tensile hoop stress-strain curve. The applicability of this new test method was demonstrated by successfully evaluating ring specimens of Zr-4 alloy to failure. The ring specimens deformed uniformly in the axial and circumferential directions until onset of necking. The χ and α factors were successfully determined by using a finite-element stress analysis that benchmarked with applied test load and total work to account for frictional forces and the associated energies dissipation between the different sliding components of the testing system. The tensile hoop strength values obtained using the proposed cone-wedge-ring-expansion test method were 10% higher than values obtained from the tensile evaluation of the cladding material along the axial direction. The variability in results was found to be within the range reported in the literature.

Solid porous Ag–Ag interface bonding and its application in the die-attached modules

Solid porous Ag–Ag interface bonding was introduced with the hillocks growth on a solid porous Ag surface. Porous Ag was fabricated on both Cu substrate and Si die by sintering a hybrid Ag paste. The size, density of grown hillocks was investigated at different heating temperature and time to provide an optimized condition in the interface bonding. The growth mechanism of hillocks on the solid porous Ag structure was discussed and analyzed in detail based on stress-induced migration and finite element stress analysis where solid porous Ag was reduced to a polycrystalline structure. The interface between two porous Ag structures bonded together in the die-attached structure with the bonding strength over 30 MPa, considerably stronger than that of traditional Sn–Pb solders. Furthermore, TEM observation revealed that Ag particles with the size of tens nanometers formed between the solid porous Ag–Ag interface, accumulate together and thus bridged the interface. This study provided a new attractive bonding technology based on the solid porous Ag structure in the die-attached module structures for large area bonding and thicker bonding layer design.

Fatigue behaviour of corrosion pits in X65 steel pipelines

Corrosion pits are a form of geometrical discontinuity that lead to stress and strain concentration in engineering components, resulting in crack initiation under service loading conditions and ultimately fracture and failure. Initiation and propagation of cracks in offshore pipelines can lead to loss of containment and environmental and commercial impacts. In order to prevent such failures, tools to predict the structural integrity of pipelines need to be improved. This work investigates the fatigue behaviour of corrosion pits in API-5L X65 grade steel pipeline utilising numerical and analytical methods. Firstly, load-controlled fatigue tests were carried out on smooth X65 steel samples to establish S–N data. Secondly, local stress–strain behaviour at corrosion pits and its effect on fatigue crack initiation were investigated using elastic-plastic finite element analysis of samples containing a single corrosion pit under cyclic loading. Analysis of stabilised stress–strain hysteresis loops at corrosion pits showed that the local stress ratio at the pit changes from 0.1 to −0.4 while the applied stress amplitude increases with the same stress ratio of 0.1. Analytical methods were also used to predict the local maximum stress and strain at the pit, which showed a similar local stress ratio to the finite element analysis result but lower stress and strain ranges. Finally, fatigue crack initiation life was predicted using the combination of finite element stress and strain analysis and the Smith–Watson–Topper strain–life approach. An advantage of this method for life estimation is that this approach considers the local stress and strains at corrosion pits rather than applied stress.

Finite element analysis of stresses in a flexible bulk solid container

Current theories and design codes pertaining to storage structures for bulk solids have been developed in the context of rigid-walled silos and may not be applicable for smaller and highly flexible containers that are often used for industrial packaging and intermediate storage. The focus of this study is to investigate the effect of wall flexibility on the bulk stresses and wall pressures during storage using finite element analysis. The results show that when the wall stiffness is low, the computed bulk stresses in the vertical bin section are dominated by plasticity, while the stresses in the hopper section remain in the elastic state. In this situation, the wall pressure in the bin section is heavily influenced by the strength of the stored solid, which controls the extent of plastic flow. Overall, the normal wall pressure in the bin section is found to decrease with wall flexibility leading to a corresponding increase in vertical stress in the stored solid. As a consequence, the stresses in the hopper also increase leading to increasing loads on the hopper walls and potential exacerbation of handling issues for cohesive materials in highly flexible containers.

Supercritical cryo-compressed hydrogen storage for fuel cell electric buses

Liquid hydrogen (LH2) truck delivery and storage at dispensing sites is likely to play an important role in an emerging H2 infrastructure. We analyzed the performance of single phase, supercritical, on-board cryo-compressed hydrogen storage (CcH2) with commercially-available LH2 pump enabled single-flow refueling for application to fuel cell electric buses (FCEB). We conducted finite-element stress analyses of Type 3 CcH2 tanks using ABAQUS for carbon fiber requirement and Fe-Safe for fatigue life. The results from these analyses indicate that, from the standpoint of weight, volume and cost, 2-mm 316 stainless steel liner is preferred to aluminium 6061 alloy in meeting the required 15,000 charge-discharge cycles for 350–700 bar storage pressures. Compared to the Type 3, 350 bar, ambient-temperature H2 storage systems in current demonstration FCEBs, 500-bar CcH2 storage system is projected to achieve 91% improvement in gravimetric capacity, 175% improvement in volumetric capacity, 46% reduction in carbon fiber composite mass, and 21% lower system cost, while exceeding >7 day loss-free dormancy with initially 85%-full H2 tank.

A Semi-Infinite Strip Pressed Against an Elastic Half-Plane With Frictional Slip

The subject of this investigation is the plane strain elasticity problem of a finite width semi-infinite strip with its end pressed against a half-plane of the same material with friction. From the existing integral equation solution for a perfect bond, it is shown that the length of the zone of frictional slip and the value of the slip displacement can both be inferred. It is further shown how this method allows a finite element stress analysis of a structure, obtained with the simple assumption of a perfect bond, to be used instead of the more complicated finite element structural analysis with frictional slip. Nonetheless, the results of this simpler finite element analysis can be used to infer the length of the frictional slip zone and the magnitude of the slip displacement. It is expected that this method will be valuable in the analysis of the mechanics of fretting. Damage due to fretting fatigue is initiated due to frictional slip near the edges of the interface between two connected materials. The stress analysis of structures, which includes these frictional slip zones, is considerably more complicated than it is for a perfect bond, often making it impractical to include in a comprehensive finite element model of the complete structure. Thus, the methodology used in this paper should allow the size of the frictional slip zones and the frictional slip displacements to be inferred directly from the stress analysis for a perfect bond.

A Complex shaped crucible frame structure modelling and finite element analysis for stress and deformation

Crucible frame structures are otherwise called as complex frame structures and its study is needed for further improvement in the emerging technology. The frame structure are frequently used an operational system support of other mechanisms of a physical construction and/or steel frame that limits the assembly's extent in this study crucible frame structures are analysed using Finite element analysis and the results are expected in terms of safety for actual use. Based on ANSYS Software, the crucible structure can be meshed (discretized into several parts are called elements). At last, we can apply the boundary conditions and calculate its maximum deformation by applying various loads.