Von Mises Stress Distribution Research Articles

Thermal Stress and Deformation of Hollow Paddle-Shaft Components with Internal High Temperature Molten Salt Flow

Excessive thermal stress and deformation are important reasons causing disservice of high temperature heat exchangers. This paper presents thermal stress and expansion analysis of single-leaf type hollow paddle-shaft components with internal high temperature molten salt flow based on three-dimensional numerical simulations. The results show that the hollow paddles enhance the heat transfer and decrease the maximum thermal stress simultaneously with the expense of a much higher pressure drop than that of solid paddles. The cumulative von Mises stress distribution curve shows that the stress distribution of the component with hollow paddles is more uniform than that with solid paddles. The radial and axial deformations do not differ much for the components with hollow and solid paddles. A larger volume of the fluid space in the hollow paddles leads to stronger heat transfer, smaller maximum thermal stress, and more uniform stress distribution. The effects of the paddle height, the diameter and number of flow holes, the molten salt flow rate, and the material-side heat transfer coefficient are identified. The advantages of hollow paddle designs in both heat transfer and thermal stress (local and overall) performance are revealed. The work in this study can provide a reference for the design and optimization of hollow paddle heat exchangers with high temperature molten salt as working fluid.

Simulation of a Double-Sided Cathode SOFC Comparing Different Electrochemical Reaction Kinetics

A 3D symmetric double-sided cathode SOFC model is constructed considering coupled electrochemistry, fluid dynamics, gas diffusion, heat transfer as well as mechanical properties. The cell geometry constructed is based on the prototype SOFC model tested at Ningbo Institute of Material Technology and Engineering (NIMTE) in China (1). The detailed geometry is shown in Figure 1 (a). In this study, different kinetics expressions for anode and cathode reaction are compared. For anode, the oxidation of hydrogen comprises of different elemental reactions which include adsorption/desorption and charge transfer steps, but for cathode the reaction is simpler, e.g., the reduction of oxygen (2). In this paper, the current density, temperature distribution as a function of different kinetics will be presented. Moreover, the stress distributions will also be carefully analyzed.Preliminary results of electrode current density, temperature and von Mises stress distribution is showed in Figure 1 (b ~ c). Detailed comparation of different distribution in 2D as well as line graph will be extracted with different kinetics. This work will lay foundation for further modelling work when considering different electrochemical kinetics.Figure 1 (a) Model geometry; (b) Electrode current density distribution; (c) Temperature distribution; (d) von Mises stress distribution.

Three-Dimensional Computational Modeling of an Extra-Descending Aortic Assist Device Using Fluid-Structure Interaction

BackgroundThe incidence of heart failure is anticipated to rise by 2030, resulting in more than 8 million adults with this condition in US. Despite the advancement in pharmacological and surgical treatments, some patients progress to severe forms of cardiac dysfunction requiring cardiac transplantation as a last-resort treatment. Cardiac assist devices play an essential role in the recovery of normal cardiac performance through reversible remodeling or in assisting the weak organ to prolong survival rate. However, these devices need to be monitored carefully, as prolonged use may lead to physiological maladaptation and further cardiac complications. The optimization of such devices has done through the development and use of numerical simulations that allow the analysis of in-vivo hemodynamic patterns of blood flow. This study aims to investigate the performance of a model of extra-aortic assist device surrounding the descending aorta through three-dimensional patient-specific modeling. MethodsA three-dimensional model of the aorta was constructed from patient-specific cardiac CT images of a 60-year-old male diagnosed with left ventricular failure at the Tehran Heart Center (THC). Numerical simulation was conducted for two complete cardiac cycles using fluid-structure interaction (FSI) analysis under the assumption that the balloon and the aortic vessel behave as linear elastic materials, and that blood is a Newtonian and incompressible fluid. ResultsThe numerical simulation demonstrated a high correlation between the FSI analysis and clinical data of the patient-specific anatomical and physiological conditions. Blood velocity, pressure, deformation, and strain contours were simulated and analyzed through three-dimensional modeling. Compared to the unassisted aorta, the device provided an increase in blood flow displacement of an additional 15 ml of blood in the descending aorta, brachiocephalic, carotid, and subclavian arteries. The maximum von Mises stress distribution across the aortic vessel was higher than the stress imposed on the system in the unassisted heart, with values of 3.3 MPa and 0.28 MPa, respectively. Numerical investigation of structural responses revealed that no remarkable force was exerted on the aortic valve by the device at the descending aorta. ConclusionWe present the numerical investigation of a counterpulsation device around the descending aorta that has not previously been tested on human or animal models. While this extra-aortic balloon pump (EABP) did not show a significant improvement in coronary perfusion, there is room for improvement in further studies to optimize the geometry of the balloon. Additional investigations are required to determine the efficacy of this device and its safety before in-vivo experimental studies are pursued. This simulation has clinical relevance when choosing an appropriate cardiac assist device to address patient-specific physiological and pathological conditions.

Investigations on the influence of nano reinforcement on strength of adhesively bonded joints

This paper aims to study the effect of adding nano reinforcement on load bearing capacity and shear strength of glass epoxy composite joints bonded by a two-component structural acrylic adhesive. SiC nanoparticles having diameter in the range of 25–40 nm were used to reinforce epoxy adhesive. Nanocomposite adhesives having 0.1, 0.25, 0.5 and 1.0 wt% of SiC nanoparticles were manufactured using in-situ polymerization technique. Results indicated that failure load of the joints having SiC nanocomposite adhesive was higher than that of joint with neat adhesive. Shear strength and load bearing capacity of single lap joints with adhesive having 0.75 wt% of nanoparticles was 38% higher than that of joints with neat adhesive. Distribution of shear stress, von-Mises stress and peel stress were also analyzed to study the effect of reinforcement in adhesive by Finite Element analysis.

Mechanical characterization of composite pipe systems joined using different radii pipes subject to internal pressure

Failure tests for internal pressurized composite pipe system joined by using different radii pipes were carried out by the finite element method and experimental tests. The composite pipes were produced from E glass fiber/epoxy. DP410 and DP490 type adhesives were used to join the composite pipes. The numerical results and experimental results were compared. It was shown that the numerical analyzes results were close to experimental results. Tangential, radial, axial, and shear stress values on composite pipes and adhesive layers were obtained via numerical analyses in the radial direction. Additionally, the von Mises stress distributions were obtained on the adhesive. The effects of adhesive layer lengths, adhesives types, and orientation angle on the effect of the joint zone were investigated.

Characterization of the Subchondral Bone and Pain Behavior Changes in a Novel Bipedal Standing Mouse Model of Facet Joint Osteoarthritis.

Background The subchondral bone parallels with the progression of osteoarthritis (OA). However, the biomechanical properties and histopathological changes of subchondral bone changes in the lumbar facet joint (LFJ) after long-term axial loading on the spine have not been explored. In this study, we aimed to investigate the subchondral bone histopathological changes that occur in the LFJ and pain behaviors in a novel bipedal standing mouse model. Methods Sixteen 8-week-old male C57BL/6 mice were randomly assigned into bipedal standing and control groups. A finite element stimulate model based on the micro-CT data was generated to simulate the von Mises stress distribution on the LFJ during different positions. The spine pain behaviors tests were analysis. In addition, the change in the subchondral bone of the LFJ was assessed by histological and immunohistochemistry staining. Results The computerized simulation of the von Mises stress distribution in the superior articular process of LFJ at the spine level 5 in the lying position increased and reached a maximum value at the bipedal standing posture. The spine pain behavior test revealed that the threshold of pressure tolerance decreased significantly in bipedal groups relative to control groups, whereas the mechanical hyperalgesia of the hind paw increased significantly in bipedal groups relative to control groups. The axial load accelerates LFJ degeneration with increased histological scores in bipedal groups. The expression of type II collagen and aggrecan (ACAN) was significantly decreased in the bipedal groups compared with the control groups, whereas the expression of MMP13 was increased. Compared with the control groups, the osteoclast activity was activated with higher TRAP-positive staining and associated with increased CD-31-positive vessels and GCRP-positive nerve ending expression in the subchondral bone of LFJ. Conclusion Collectively, long-term axial loading induces the development of spine hyperalgesia in mice associate with increased osteoclast activity and aberrant angiogenesis and nerve invasion into the subchondral bone of LFJ that stimulates the natural pathological change in human LFJ OA. These results indicate that aberrant bone remodeling associate with aberrant nerve innervation in the subchondral bone has a potential as a therapeutic target in LFJ OA pain.

Dynamic analysis of offshore wind turbines

For large-scale 5MW offshore wind turbines, the discrete equation of fluid domain and the motion equation of structural domain with geometric nonlinearity were built, the three-dimensional modeling of the blade considering fluidstructure interaction (FSI) was achieved by using Unigraphics (UG) and Geometry modules, and the numerical simulation and the analysis of the vibration characteristics for wind turbine structure under rotating effect were carried out based on ANSYS software. The results indicate that the rotating effect has an apparent effect on displacement and Von Mises stress, and the response and the distribution of displacement and Von Mises stress for the blade in direction of wingspan increase nonlinearly with the equal increase of rotational speeds. Compared with the single blade model, the blade vibration period of the whole machine model is much longer. The structural coupling effect reduces the response peak value of the blade displacement and Von Mises stress, and the increase of rotational speed enhances this coupling effect. The maximum displacement difference between two models decreases first and then increases along wingspan direction, the trend is more visible with the equal increase of rotational speed, and the boundary point with zero displacement difference moves towards the blade root. Furthermore, the Von Mises stress difference increases gradually with the increase of rotational speed and decreases nonlinearly from the blade middle to both sides. The results can provide technical reference for the safe operation and optimal design of offshore wind turbines.

Graphdiyne family-tunable solution to shock resistance

The excellent mechanical properties of Graphdiyne (GDY) family has enabled it as an appealing candidate in the field of impact protection. In this in silico study, Monolayer GDY nanosheets of different morphology including GDY, GY-3, GY-4, GY-5 and GY-6 are assessed under hypervelocity impacts (from 1 to 6 km s−1). Tracking the deformation mechanisms under impacts as well as the Probability density function based on atomic Von Mises stress distribution, the length of acetylenic chain clearly alters ductile behavior as well as the energy dissipation/delocalization rate of GDY family during the impact. Results also suggest the penetration energy is not only determined by the energy delocalization rate but also sensitive to impact velocity for nanosheet with various acetylenic chain length. GY-5 with a much lower energy delocalization rate presents a close penetration energy comparing with GDY at a low impact at ∼2.0 km s−1, its superior ductility granted by long acetylenic chain not only dissipates kinetic energy of projectile via deformation, but also extends time for acceleration during the contact with projectile. Considering the impact resist performance of GDY family in terms of Specific penetration energy, GY-5 with the perfect balance between material density, ductility and Young’s modulus makes it the superior anti-ballistic material for impact velocity at <5 km s−1. For impact velocity >5 km s−1, it induces severer local deformation, and leaves no time for a well-developed distributed pattern as observed in a lower impact velocity scenario. As such, extensive elastic deformation of the nanosheet is not captured under impact, nanosheets with shorter acetylenic chains and hence greater material strength demonstrates superior impact resist. This study provides a fundamental understanding of the deformation and penetration mechanisms of monolayer GDY nanosheets under impact, which is crucial in order to facilitate their emerging applications for impact protection.

A 3D finite element analysis of maxillary molar distalization using unilateral zygoma gear and asymmetric headgear.

The aims of this study were (a) to evaluate the displacement and stress distribution in the maxillary dentition associated with the use of two different unilateral distalization appliances-unilateral zygoma gear (UZG) appliance and asymmetric headgear (AHG)-in non-growing patients; and (b) to assess the effects of fully erupted maxillary third molars on the distalization of the first molar with both appliances by using three-dimensional finite element analysis. Two 3D models of the maxilla were created: one with third molars and one without. Next, two distalizing appliances (UZG and AHG) were added to each model to create four models. Distalization forces were applied, and the resultant displacements were recorded at the mesiobuccal and distolingual cusps and palatal root apex of each molar and the incisal edge root apex of the central incisors. The resulting von Mises stress distributions were evaluated. With the UZG, the first molar showed greater root distalization than the crown in the model with the third molar, whereas the model without the third molar showed distalization and distal tipping of the first molar. With the AHG, the first molar showed a large amount of distal tipping in the model without a third molar. However, this tipping was less than that in the model with third molars. The presence of completely erupted third molars decreased the amount of uncontrolled distal tipping in both appliances. UZG can be considered as an effective option for maxillary molar distalization.

Rosa roxburghii-like hierarchical hollow sandwich-structure C@Fe2O3@C microspheres as second nanomaterialsfor superior lithium storage

Fe2O3, as a promising advanced anode for the next generation lithium ion batteries, behaves high theoretical capacity and rich electrochemical properties. However, the poor cycle performances and low conductivity impede its extensive applications in lithium ion batteries. Herein, the von Mises stress distribution on solid spheres and hollow spheres were simulated by finite element method which confirmed the vital role of porous hollow spheres on strain-relaxation behavior as electrode materials. We also have developed a template method for the first preparation of rosa roxburghii-like hierarchical hollow sandwiched C@Fe2O3@C microspheres as second nanomaterials for superior lithium storage. As an advanced anode for lithium ion batteries, the porous C@Fe2O3@C microspheres exhibit reversible gravimetric capacity (1167 mAh g−1 after 100 cycles at 0.2 C), high rate performance (762 mAh g−1 after 1000 cycles at 1 C) and cycling stability without obvious capacity fading. The excellent performance is ascribed to the hierarchical hollow structure which can better withstand the stress produced in the process of ion embedding/stripping and alleviate the volume change of materials. On the other hand, the double carbon layer can effectively inhibit the self-aggregation effect of nano-scale Fe2O3 and provide a three-dimensional electronic network.

Comparative analysis of thermal stress induced dislocations in 7 kg, 40 kg and 330 kg multi-crystalline silicon ingots grown by directional solidification

In this paper, transient heat and mass transfer numerical simulations have been done to analyse the variation in thermal stress induced dislocations in 7 kg, 40 kg and 330 kg mc-silicon ingots grown using Directional Solidification (DS) furnace. The thermal parameters such as temperature distribution, principal stress, shear stress and von Mises stress distribution are examined. The effect of ingot size on temperature parameters, solid/melt interface, stress distribution and dislocation generation are investigated to obtain essential information needed for system design. It is observed that with respect to increase in size of the ingot the convexity of solid/melt interface decreases and the uniformity in radial and axial distribution of temperature and thermal stress also increase thereby decreasing the dislocation generation in the grown mc-silicon ingot. It shows that furnace design and ingot size play a crucial role in generation of thermal stress induced dislocation and defects in the grown ingot.

Evaluation of deformation in the buccal lamellar bone with finite element analysis in alveolar ridge-splitting/expansion technique

PurposeThe aim of this study was to investigate deformation and stress distribution in the buccal lamellar bone via finite element analysis (FEA) in the application of alveolar ridge-splitting/expansion technique (ARST) in atrophic maxilla and mandible. Material and methodThree-dimensional (3D) solid models of maxilla and mandible were formed using computer software, with an alveolar ridge thickness of 4 mm in the right first molar region. In both models, one horizontal and two releasing vertical osteotomies were made in the atrophic region. Vertical forces varying from 50 N to 1000 N were continuously applied on the midpoint of the horizontal osteotomy and then the axial and total deformation and von Mises stress distribution in the buccal lamellar bone was assessed by FEA. ResultsThe degrees of axial deformation and total deformation and the maximum von Mises stress value under a 50 N force were 0.22 mm, 0.23 mm, and 4.52 MPa in the maxillary buccal lamellar bone and were 0.04 mm, 0.06 mm, and 5.90 MPa in the mandibular buccal lamellar bone, respectively. Similarly, under a 1000 N force, the values were 4.44 mm, 4.75 mm, and 90.49 MPa in the maxillary buccal lamellar bone and were 0.96 mm, 1.1 mm, and 118.02 MPa in the mandibular buccal lamellar bone, respectively. ConclusionThese findings implicate that the ARST used for implant placement or alveolar augmentation can be achieved with the application of lower amounts of force in the maxilla compared to the mandible. It was also revealed that in ARST, the maximum von Mises stress value was lower in the maxillary buccal lamellar bone than in the mandibular buccal lamellar bone. Based on these findings, we consider that the administration of ARST could be biomechanically more stable in the maxilla than in the mandible.

A new proximal femoral nail antirotation design: Is it effective in preventing varus collapse and cut-out?

Objectives This study aims to compare the mechanical features of the existing proximal femoral nail antirotation (PFNA) system and the new PFNA system that we designed using three-dimensional (3D) finite element analysis.Materials and methods This experimental study was conducted between 2019 and 2020. We constructed two femur models with Arbeitsgemeinschaft für Osteosynthesefragen (AO) type A1 fractures using 3D computed tomography scans. The new and standard PFNA designs were inserted into the femur models and subsequently transferred to the program. We investigated the distribution of stress on the tip of the lag screw, the calcar region, lag screw-nail junction, and the additional screw inserted through the greater trochanter (only present in the new PFNA design) using 3D finite element analysis.Results When the von Mises stress distributions in our models were examined, the maximum stress at the lag screw-nail junction was 18 mpa in the new design PFNA, while it was 20 mpa in the classic PFNA model. The maximum stress at the junction of the additional screw that had greater trochanter inlet with the nail was found as 42.5 mpa. The maximum stress on the calcar region was found to be 10 mpa at the new design PFNA, while it was 13 mpa with 30% increase in the classic PFNA. The stress on the tip of the lag screw was found to be 49 mpa in the classic PFNA design, while in the new design PFNA it was found as 28 mpa with a decrease of more than 40%.ConclusionAs per our findings, the new PFNA design leads to reduced stress on the lag screw-nail junction, the calcar region, and the tip of the lag screw.

Strength and stiffness analyses of standard and double mortise and tenon joints

This paper investigated the effect of the tenon length on the strength and stiffness of the standard mortise and tenon joints, as well of the double mortise and tenon joints, that were bonded by poly(vinyl acetate) (PVAc) and polyurethane (PU) glues. The strength was analyzed by measuring applied load and by calculating ultimate bending moment and bending moment at the proportional limit. Stiffness was evaluated by measuring displacement and by calculating the ratio of applied force and displacement along the force line. The results were compared with the data obtained by the simplified static expressions and numerical calculation of the orthotropic linear-elastic model. The results indicated that increasing tenon length increased the maximal moment and proportional moment of the both investigated joints types. The analytically calculated moments were increased more than the experimental values for both joint types, and they had generally lower values than the proportional moments for the standard tenon joints, as opposed to the double tenon joints. The Von Mises stress distribution showed characteristic zones of the maximum and increased stress values. These likewise were monitored in analytical calculations. The procedures could be successfully used to achieve approximate data of properties of loaded joints.

Effects of proximal fibular osteotomy on stress changes in mild knee osteoarthritis with varus deformity: a finite element analysis

BackgroundMany previous studies lack sufficient quantitative evidences about changes in biomechanical properties of the knee in response to proximal fibular osteotomy (PFO). Therefore, the aim of this study was to compare the preoperative and postoperative effects of PFO on mechanical stresses in the knee joint and provide with a biomechanical basis for PFO in the treatment of mild knee osteoarthritis (KOA) with varus deformity.MethodsA total of 10 patients suffering mild KOA with varus deformity were enrolled in this study. Their image data from computerized tomography (CT) and magnetic resonance imaging (MRI) were used for finite element models, and PFO models were established. Static structural analysis was carried out using ABAQUS to compare the von Mises stress distribution and values of the maximal von Mises stress of femoral cartilage, meniscuses, tibial cartilages, and tibial plateau before and after surgery.ResultsThe stress distribution in the cortical bone of the tibial plateau showed that stresses were transferred from the anterior medial area to the posterior medial area after PFO. Values of the maximal von Mises stress in femoral cartilage, medial meniscus, medial tibial cartilage, and tibial plateau after surgery were significantly lower than the preoperative values, with statistically significant differences (P < 0.05). Postoperative values of the maximal von Mises stress of lateral meniscus and lateral tibial cartilage were significantly higher than the preoperative ones, with statistically significant differences (P < 0.05).ConclusionPFO could reduce the stresses in the medial compartment of the knee joint with stress pathways transferring from the anterior medial area to the posterior medial area of the tibial plateau. Therefore, PFO is recommended for the treatment of mild KOA with varus deformity featuring favorably pain-relieving effects.Graphical abstract

On Wave-Induced Elastic Deformations of a Submerged Wave Energy Device

Structural integrity has remained a challenge for design and analysis of wave energy devices. A difficulty in assessment of the structural integrity is often laid in the accurate determination of the wave-induced loads on the wave energy devices and the repones of the structure. Decoupled hydroelastic response of a submerged, oscillating wave energy device to extreme nonlinear wave loads is studied here. The submerged wave energy device consists of an oscillating horizontal disc attached to a direct-drive power take-off system. The structural frame of the wave energy device is fixed on the seafloor in shallow water. Several extreme wave conditions are considered in this study. The nonlinear wave loads on members of the submerged structure are obtained by use of the level I Green-Naghdi equations and Morison’s equation for cylindrical members. Distribution of Von Mises stresses and the elastic response of the structure to the extreme wave loads are determined by use of a finite element method. The decoupled hydroelastic analysis of the structure is carried out for devices built by four different materials, namely stainless steel, concrete, aluminium alloy, and titanium alloy. The elastic response of these devices is studied and results are compared with each other. Points of maximum stress and deformations are determined and the structural integrity under the extreme conditions is assessed. It is shown that the proposed approaches provide invaluable information about the structural integrity of wave energy devices.

Finite element analysis of load-carrying capacity of single lap joints bonded with epoxy/nanoalumina adhesives

Influence of alumina nanoparticles in the epoxy adhesive on the load-carrying capacity of single lap joints was investigated using the finite element method. Nanocomposite adhesives were modelled by reinforcing randomly distributed spherical shaped (at 0.5, 1.0 and 1.5 wt.%) and rod-shaped (at 0.5 and 1.0 wt.%) alumina nanoparticles in the epoxy. 2D finite element was used to discretise the domain of single lap joint comprising nanocomposite adhesives. The load-carrying capacity of single lap joints bonded with nanocomposite adhesive comprising 1.5 wt.% of nanospheres and 1.0 wt.% of nanorods was 58% and 51% more than that of joints with neat adhesive, respectively. The distribution of von-Mises stress, shear stress and peel stress at adherend/adhesive layer interface along the overlap length of the joint was analysed.

Mechanical behaviour of 3D printed vs thermoformed clear dental aligner materials under non-linear compressive loading using FEM

Clear dental aligners are commonly manufactured using thermoplastic materials such as Duran and Durasoft. Using conventional thermoforming methods there are inherent disadvantages including time consumption and poor geometrical accuracies that often occur. The use of digital technologies and 3D printing techniques for producing dental aligners is often preferred where possible. Innovation in 3D printing has resulted in bio-compatible materials becoming more readily available, including Formlabs Dental LT Clear resin, which is a 3D printable and Class IIa bio-compatible material. In this paper, we investigate the difference between thermoplastic materials such as Scheu-Dental Duran and Durasoft and 3D printed Dental LT using Finite Element Analysis (FEA)/Finite Element Modelling (FEM) in a dental aligner case based on an analysis of von Mises stress distribution at molars, incisors and canines for a total of 33161 nodes using Finite Element Analysis (FEA). Maximum von Mises stress distribution at all of the sections under the action of non-linear compressive forces equivalent to human biting force (up to 600 N) were discovered to vary within a range of 0.2–7.7% for Dental LT resin. The Duran and Durasoft cases were comparable, thereby widening the scope for the use of Dental LT in various dentistry applications, including clear aligners.

Fixation of femoral neck fractures with three cannulated screws: biomechanical changes at critical fracture angles

Amaç: Femur boyun kırıklarında koronal planda kırık açısının artması instabiliteyi ve komplikasyonları arttırmaktadır. Bu çalışmadaki amacımız Pauwels sınıflamasında belirlenmiş olan kritik açılardaki (30 derece, 50 derece, 70 derece) biyomekanik değişiklikleri analiz etmektir. Yöntemler: 3D bilgisayarlı tomografi taramasından elde edilen femur modelinde koronal plandaki kırık açısına göre 30, 50 ve 70 derece femur boyun kırığı oluşturuldu. Inverted triangle pozisyonunda 3 adet kanüllü vida yerleştirildi. Vidalar anterior-superior (A), posterior –süperior (B) ve inferior (C) olarak isimlendirildi. Üç model Ansys Workbench programına aktarılarak vidalardaki ve distal kırık yüzeyindeki von mises stres dağılımları kaydedildi. Bulgular: Maximum stres 30 derece kırık modelinde A vidasında 18,06 mpa idi. B vidasında ise 22,13 MPa, C vidasında 16,21 MPa olarak bulundu. 50 derece kırık modeline baktığımızda max stres değerleri A vidasında 68,04 MPa iken B vidasında 89,52 MPa ,C vidasında ise 48,94 MPa olarak bulundu. 70 derece kırık modelinde A vidasında maximum stres 120,02 MPa, B vidasında 138,32 MPa idi. C vidasında ise 98,37 MPa olarak bulundu. Distal kırık yüzeyindeki stres değerleri ise 30, 50, 70 derece modellerde sırası ile 13,54 MPa, 43,80 MPa ve 50,07 MPa idi. Sonuç: Femur boyun kırıklarında kırık açısının 30 dereceden 50 dereceye yükseltilmesi distal kırık yüzeyi ve implantlar üzerindeki gerilimi önemli ölçüde artırmaktadır. Ancak bu artış 50 derecenin üzerindeki açılarda minimumdur.

Mechanical Properties of Cu-Core Solder Balls with ENEPIG Surface Finish

The development of ball grid array (BGA) packages, such as the chip scale package, wafer level package and package on package, has focused on creating electronics packages that are smaller, thinner, higher-performance and capable of higher functionality, among other desirable traits. Among the interconnection materials used in BGA packages, the Cu-core solder ball (CCSB) has many advantages, such as the use of finer pitch, improved electrical conductivity and better controllability of the coplanarity of the chip. In this study, we evaluated the mechanical properties of the CCSB and Sn-3.0Ag-0.5Cu (SAC) by low-speed shear tests, and the von Mises stress distribution and plastic strain distribution were simulated using a finite element method. The diameter of each solder ball was 280 μm, and the outer layer of the CCSB was a plated SAC layer. The shear strength of the CCSB was about 10% greater than that of SAC. The maximum value of the simulated von Mises stress for the CCSB was higher than that of SAC because the Cu-core is stiffer than SAC. The fracture energy of the CCSB decreased by about 50% compared to that of SAC. The maximum value of simulated plastic strain, which is associated with fracture surfaces, was higher with the CCSB than with SAC. We can thus conclude that the Cu-core in the CCSB affects the shear strength and fracture behavior of solder joints.