scholarly journals Effect of material selection on tibial post stresses in posterior-stabilized knee prosthesis

2020 ◽  
Vol 9 (11) ◽  
pp. 768-777
Author(s):  
Chang-Hung Huang ◽  
Yung-Chang Lu ◽  
Lin-I Hsu ◽  
Jiann-Jong Liau ◽  
Ting-Kuo Chang ◽  
...  
Keyword(s):  
Plastic Strain ◽  
Material Selection ◽  
Equivalent Plastic Strain ◽  
Mobile Bearing ◽  
Von Mises Stress ◽  
Stress And Strain ◽  
Fixed Bearing ◽  
Bearing Design ◽  
Tibial Post ◽  
Von Mises

Aims The material and design of knee components can have a considerable effect on the contact characteristics of the tibial post. This study aimed to analyze the stress distribution on the tibial post when using different grades of polyethylene for the tibial inserts. In addition, the contact properties of fixed-bearing and mobile-bearing inserts were evaluated. Methods Three different grades of polyethylene were compared in this study; conventional ultra high molecular weight polyethylene (UHMWPE), highly cross-linked polyethylene (HXLPE), and vitamin E-stabilized polyethylene (VEPE). In addition, tibial baseplates with a fixed-bearing and a mobile-bearing insert were evaluated to understand differences in the contact properties. The inserts were implanted in neutral alignment and with a 10° internal malrotation. The contact stress, von Mises stress, and equivalent plastic strain (PEEQ) on the tibial posts were extracted for comparison. Results The stress and strain on the tibial post for the three polyethylenes greatly increased when the insert was placed in malrotation, showing a 38% to 56% increase in von Mises stress and a 335% to 434% increase in PEEQ. The VEPE insert had the lowest PEEQ among the three materials. The mobile-bearing design exhibited a lower increase in stress and strain around the tibial posts than the fixed-bearing design. Conclusion Using VEPE for the tibial component potentially eliminates the risk of material permanent deformation. The mobile-bearing insert can help to avoid a dramatic increase in plastic strain around the tibial post in cases of malrotation. The mobility allows the pressure to be distributed on the tibial post and demonstrated lower stresses with all three polyethylenes simulated. Cite this article: Bone Joint Res 2020;9(11):768–777.

scholarly journals Evaluation of Bone–Implant Interface Stress and Strain Using Heterogeneous Mandibular Bone Properties Based on Different Empirical Correlations

2021 ◽  
Author(s):  
Mostafa Omran Hussein ◽  
Mohammed Suliman Alruthea
Keyword(s):  
Finite Element ◽  
Group Iv ◽  
Von Mises Stress ◽  
Patient Specific ◽  
Dental Arch ◽  
Stress And Strain ◽  
Bone Implant ◽  
Bone Properties ◽  
Group I ◽  
Von Mises

Abstract Objective The purpose of this study was to compare methods used for calculating heterogeneous patient-specific bone properties used in finite element analysis (FEA), in the field of implant dentistry, with the method based on homogenous bone properties. Materials and Methods In this study, three-dimensional (3D) computed tomography data of an edentulous patient were processed to create a finite element model, and five identical 3D implant models were created and distributed throughout the dental arch. Based on the calculation methods used for bone material assignment, four groups—groups I to IV—were defined. Groups I to III relied on heterogeneous bone property assignment based on different equations, whereas group IV relied on homogenous bone properties. Finally, 150 N vertical and 60-degree-inclined forces were applied at the top of the implant abutments to calculate the von Mises stress and strain. Results Groups I and II presented the highest stress and strain values, respectively. Based on the implant location, differences were observed between the stress values of group I, II, and III compared with group IV; however, no clear order was noted. Accordingly, variable von Mises stress and strain reactions at the bone–implant interface were observed among the heterogeneous bone property groups when compared with the homogenous property group results at the same implant positions. Conclusion Although the use of heterogeneous bone properties as material assignments in FEA studies seem promising for patient-specific analysis, the variations between their results raise doubts about their reliability. The results were influenced by implants’ locations leading to misleading clinical simulations.

Predicting Plastic Flow Behaviour, Failure Mechanisms and Severe Deformation Localisation of Dual-Phase Steel using RVE Simulation

2021 ◽  
Vol 18 (1) ◽  
pp. 8601-8611
Author(s):  
A. K. Rana ◽  
P. P. Dey
Keyword(s):  
Plastic Strain ◽  
Failure Modes ◽  
Volume Fraction ◽  
Ferrite Matrix ◽  
Martensite Phase ◽  
Von Mises Stress ◽  
Dual Phase ◽  
Strain Partitioning ◽  
Deformation Inhomogeneity ◽  
Von Mises

In this work, the von Mises stress and plastic strain distribution of Ferrite-Martensite–Dual-Phase (FMDP) steels are predicted at various stages of deformation. The failure modes and volume fraction effect are identified based on Representative Volume Element (RVE). FMDP steel consists of a typical ferrite-matrix phase, in which martensite-islands are dispersed. Recently FMDP steels are increasingly used to the various car parts in demand. 2D-RVEs are also utilised to predict the orientations effect of the martensite phase in the FMDP steels. Based on the position of the element, the boundary conditions (BC) are given in the RVE of FMDP steel microstructures. The failure modes are examined in the form of severe plastic strain localisation. While the distribution of islands in the microstructure varies, as a result, the deformation inhomogeneity increases with a rise of martensite fraction. The results of numerical computation and the trend of experimental failure shown in the literature are compared. This is signifying that the overall macro-behaviour of FMDP steel, as a consequence of stress-strain partitioning and influence of martensite-island volume fractions (MVFs), can be predicted by the finite element (FE) based 2D-RVE modelling.

scholarly journals Elasto-plastic analysis of the contact region between a rigid ellipsoid and a semi-flat surface

2018 ◽  
Vol 10 (9) ◽  
pp. 168781401879739 ◽  
Author(s):  
Pengyang Li ◽  
Lingxia Zhou ◽  
Fangyuan Cui ◽  
Quandai Wang ◽  
Meiling Guo ◽  
...  
Keyword(s):  
Residual Stress ◽  
Plastic Deformation ◽  
Plastic Strain ◽  
Contact Pressure ◽  
Contact Region ◽  
Three Dimensional ◽  
Von Mises Stress ◽  
Effective Plastic Strain ◽  
Normal Forces ◽  
Von Mises

When the load acting on a mechanical structure is greater than the yield strength of the material, the contact surface will undergo plastic deformation. Cumulative plastic deformation has an important influence on the lifespan of mechanical parts. This article presents a three-dimensional semi-analytical model based on the conjugate gradient method and fast Fourier transform algorithm, with the aim of studying the characteristic parameters of the contact region between a rigid ellipsoid and elasto-plastic half-space. Moreover, normal forces and tangential traction were considered, as well as the contact pressure resulting from various sliding speeds and friction coefficients. The contact pressure, effective plastic strain, von Mises stress, and residual stress were measured and shown to increase with increasing sliding velocity. Finally, when the friction coefficient, contact pressure, and effective plastic strain are increased, the von Mises stress is also shown to increase, whereas the residual stress decreases.

Simulation of Shock Wave Assisted Free and Shape Forming of Metallic Plates in a Shock Tube

2015 ◽  
Vol 813-814 ◽  
pp. 586-591 ◽  
Author(s):  
Kottakota Kalasagarreddi ◽  
Prem Sai Koppuravuri Sobhan ◽  
Vinay Kumar Gundu ◽  
S.R. Nagaraja
Keyword(s):  
Shock Wave ◽  
Shock Tube ◽  
Metal Forming ◽  
Von Mises Stress ◽  
Stress And Strain ◽  
Shock Strength ◽  
Engineering Problems ◽  
Experimental Values ◽  
Von Mises ◽  
Metallic Plates

Due to their complexity, certain engineering problems like finding shock strength, Mach number etc. and the interaction of shock wave with a structure in free and restricted metal forming techniques cannot be achieved in a single experimentation, these can be obtained only through a number of trials and that leads to increase in cost and time. In such cases both cost and time can be reduced by adopting numerical simulations. In this projectcommercial software ANSYS is used to simulate the propagation shock wave through a shock tube, free and shape forming of metallic plates subjected to this shock wave. Shock Mach numbers up to 2.12 have been generated by varying the driver to driven pressure ratios. Thin copper plates of diameter 60mm and thickness of 0.5mm and 0.3mm are subjected to shock wave loadingin order to form into dies.These dies,madeof structural steel are modelled with pre-defined shapes. The plate peakoverpressures ranging from 9 to 20bar have been generated.The midpoint deflection, Von Mises stress and strain are calculated for free forming copper plates. The simulated results are compared with the experimental values available in literature. The simulated results match well with the experimental values.

Chest Deflection vs. Chest Acceleration as Injury Indicator in Front Impact Simulations Using Full Human Body Finite Element Model

2009 ◽  
Author(s):  
Raed E. El-Jawahri ◽  
Jesse S. Ruan ◽  
Stephen W. Rouhana ◽  
Saeed D. Barbat
Keyword(s):  
Finite Element ◽  
Plastic Strain ◽  
Finite Element Model ◽  
Human Body ◽  
Element Model ◽  
Von Mises Stress ◽  
Head Acceleration ◽  
Blunt Impact ◽  
Von Mises ◽  
Impact Simulations

The Ford Motor Company Human Body Finite Element Model (FHBM) was validated against rib dynamic tension and 3-point bending tests. The stress-strain and moment-strain data from the tension and bending simulations respectively were compared with human rib specimen test data. The model used represented a 50th percentile adult male. It was used to compare chest deflection and chest acceleration as thoracic injury indicator in blunt impact and belted occupants in front sled impact simulations. A 150 mm diameter of 23.4 kg impactor was used in the blunt impact simulations with impact speeds of 2, 4, and 8 m/s. In the Front sled impact simulations, single-step acceleration pulses with peaks of 10, 20, and 30 g were used. The occupants were restrained by 3-point belt system, however neither pretensioner nor shoulder belt force limiter were used. The external force, head acceleration, chest deflection, chest acceleration, and the maximum values of Von Mises stress and plastic strain were the model outputs. The results showed that the external contact force, head acceleration, chest deflection, and chest acceleration in the blunt impact simulations varied between 1.5–7 kN, 5–28 g, 18–80 mm, and 8–40 g respectively. The same responses varied between 7–24 kN, 13–40 g, 15–50 mm, and 16–46 g respectively in the front sled impact simulations. The maximum Von Mises stress and plastic strain were 50–127 MPa, and 0.04–2% respectively in the blunt impact simulations and 72–134 MPa, and 0.13–3% respectively in the sled impact simulations.

scholarly journals Investigation on Yield Behavior of 7075-T6 Aluminum Alloy at Elevated Temperatures

2020 ◽  
Author(s):  
Jianping Lin ◽  
Xingyu Bao ◽  
Yong Hou ◽  
Junying Min ◽  
Xinlei Qu ◽  
...  
Keyword(s):  
Aluminum Alloy ◽  
Aluminum Alloys ◽  
Plastic Strain ◽  
Elevated Temperatures ◽  
Equivalent Plastic Strain ◽  
Yield Behavior ◽  
State Dependency ◽  
Yield Criteria ◽  
Yield Loci ◽  
Von Mises

Abstract Aluminum alloys have drawn considerable attention in the area of automotive lightweight. High strength aluminum alloys are usually deformed at elevated temperatures due to their poor formability at room temperature. In this work, the yield behavior of 7075 aluminum alloy in T6 temper (AA7075-T6) within the temperature ranging from 25 ℃ to 230 ℃ was investigated. Uniaxial and biaxial tensile tests with the aid of induction heating system were performed to determine the stress vs. strain curves and the yield loci of AA7075-T6 at elevated temperatures, respectively. Von Mises, Hill48 and Yld2000-2d yield criteria were applied to predicting yield loci which were compared with experimentally measured yield loci of the AA7075-T6. Results show that yield stress corresponding to the same equivalent plastic strain decreases with increasing temperature within the investigated temperature range and the shape of yield loci evolves nearly negligibly. The experimental yield locus expands with an increase of equivalent plastic strain at the same temperature and the work hardening rate of AA7075-T6 exhibits obvious stress-state-dependency. The non-quadratic Yld2000-2d yield criterion describes the yield surfaces of AA7075-T6 more accurately than the quadratic von Mises and Hill48 yield criteria, and an exponent of 14 in the Yld2000-2d yield function gives the optimal predictions for the AA7075-T6 at all investigated temperatures.

scholarly journals Contact Stresses in a Fixed-Bearing Total Ankle Replacement

2017 ◽  
Vol 2 (3) ◽  
pp. 2473011417S0002 ◽  
Author(s):  
Nicoló Martinelli ◽  
Silvia Baretta ◽  
Alberto Bianchi Castagnone Prati ◽  
Francesco Malerba ◽  
Carlo Corrado Bonifacini ◽  
...  
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Stance Phase ◽  
Gait Cycle ◽  
Contact Stresses ◽  
Von Mises Stress ◽  
Third Generation ◽  
Fixed Bearing ◽  
Element Analysis ◽  
Von Mises

Category: Ankle, Ankle Arthritis, Basic Sciences/Biologics Introduction/Purpose: Third-generation ankle implants with good clinical results continued to increase the popularity of total ankle arthroplasty (TAA) to address end-stage ankle osteoarthritis preserving joint movement. Newer TAA used fixed-bearing designs, with a theoretical increase of contact stresses leading to a higher polyethylene wear. The purpose of this study was to investigate the contact stresses in the polyethylene component of a new third-generation TAA, with a fixed-bearing design, using 3D finite element analysis. Methods: A three-dimensional finite element model was developed based on the Zimmer Trabecular Metal Total Ankle (ZTMTA) and a finite element analysis was employed to evaluate the contact pressure, contact area and Von Mises stress in the polyethylene articular surface in the stance phase of the gait cycle. Results: The peak values were found at the anterior regions of the articulating surface, where reached 19.8 MPa at 40% of gait cycle. The average contact pressure during the stance phase of gait was 6.9 MPa. The maximum von Mises stress of 14.1 MPa in the anterior section was reached at 40% of the gait cycle. For the central section the maximum von Mises stress of 10.8 MPa was reached at 37% of the gait cycle, whereas for posterior section the maximum of 5.4 MPa was reached at the end of the stance phase (60% of the gait cycle). Conclusion: Although, the average von Mises stress was less than 10 MPa, high peak pressure values were recorded. Advanced models to quantitatively estimate the wear are needed to assess polyethylene and metal component survivorship.

A randomized controlled trial of fixed- versus mobile-bearing total knee arthroplasty

2018 ◽  
Vol 100-B (7) ◽  
pp. 925-929 ◽  
Author(s):  
M. P. Abdel ◽  
M. E. Tibbo ◽  
M. J. Stuart ◽  
R. T. Trousdale ◽  
A. D. Hanssen ◽  
...  
Keyword(s):  
Total Knee Arthroplasty ◽  
Randomized Controlled Trial ◽  
Knee Arthroplasty ◽  
Controlled Trial ◽  
Mobile Bearing ◽  
Fixed Bearing ◽  
Randomized Controlled ◽  
Total Knee ◽  
Bearing Design ◽  
Ks Function

Aims It has been suggested that mobile-bearing total knee arthroplasty (TKA) might lead to better outcomes by accommodating some femorotibial rotational mismatch, thereby reducing contact stresses and polyethylene wear. The aim of this study was to determine whether there is a difference between fixed- and mobile-bearing versions of a contemporary TKA with respect to durability, range of movement (ROM) and function, ten years postoperatively. Patients and Methods A total of 240 patients who were enrolled in this randomized controlled trial (RCT) underwent a primary cemented TKA with one of three tibial components (all-polyethylene fixed-bearing, modular metal-backed fixed-bearing and mobile-bearing). Patients were reviewed at a median follow-up of ten years (IQR 9.2 to 10.4). Results There was no difference in durability, as measured by survivorship free of revision for any reason, nor in mean maximal ROM at ten years (p = 0.8). There was also no difference in function, as measured by Knee Society (KS) function scores (p = 0.63) or the prevalence of patellar tilt (p = 0.12). Conclusion In this clinical RCT, the mobile-bearing design of TKA was found to be reliable and durable, but did not provide better maximum knee flexion, function or durability ten years postoperatively compared with a posterior-stabilized, fixed-bearing design incorporating either an all-polyethylene or a modular-metal-backed tibial component. Cite this article: Bone Joint J 2018;100-B:925–9.

Shear Ram Height Characterization for Copper Wire Bond Shear Test

2012 ◽  
Vol 229-231 ◽  
pp. 674-677 ◽  
Author(s):  
Z. Sauli ◽  
V. Retnasamy ◽  
A. H. M. Shapri ◽  
N. A. Z. Rahman ◽  
W.M.W. Norhaimi ◽  
...  
Keyword(s):  
Shear Test ◽  
Copper Wire ◽  
Equivalent Strain ◽  
Von Mises Stress ◽  
Stress And Strain ◽  
Strain Response ◽  
Element Analysis ◽  
Ball Bond ◽  
Wire Bond ◽  
Von Mises

The work here investigates the height effect during a shearing process of a copper ball bond in a wire bond. Finite element analysis was used to investigate this analysis.The effects of the shear ram height on the stress and strain response of the copper ball bond were investigated. The results obtained hows there is a significant effect of the shear height to the Von Mises stress and equivalent strain response to the copper ball bond during the shearing simulation.

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