scholarly journals Sensitivity of the Stress Field of the Proximal Femur Predicted by CT‐based FE Analysis to Modeling Uncertainties

2021 ◽  
Author(s):  
Sina Youssefian ◽  
Jarred A. Bressner ◽  
Mikhail Osanov ◽  
James K. Guest ◽  
Wojciech B. Zbijewski ◽  
...  
Keyword(s):  
Stress Field ◽  
Proximal Femur ◽  
Fe Analysis ◽  
Modeling Uncertainties

Thermal Simulation of an Arbitrary Residual Stress Field in a Fully or Partially Autofrettaged Thick-Walled Spherical Pressure Vessel

2008 ◽  
Vol 130 (3) ◽  
Author(s):  
M. Perl
Keyword(s):  
Residual Stress ◽  
Temperature Field ◽  
Stress Field ◽  
Pressure Vessel ◽  
Fe Analysis ◽  
Stress Fields ◽  
Equivalent Temperature ◽  
Residual Stress Field ◽  
Spherical Pressure ◽  
The Ideal

The equivalent thermal load was previously shown to be the only feasible method by which the residual stresses due to autofrettage and its redistribution, as a result of cracking, can be implemented in a finite element (FE) analysis of a fully or partially autofrettaged thick-walled cylindrical pressure vessel. The present analysis involves developing a similar methodology for treating an autofrettaged thick-walled spherical pressure vessel. A general procedure for evaluating the equivalent temperature loading for simulating an arbitrary, analytical or numerical spherosymmetric autofrettage residual stress field in a spherical pressure vessel is developed. Once presented, the algorithm is applied to two distinct cases. In the first case, an analytical expression for the equivalent thermal loading is obtained for the ideal autofrettage stress field in a spherical shell. In the second case, the algorithm is applied to the discrete numerical values of a realistic autofrettage residual stress field incorporating the Bauschinger effect. As a result, a discrete equivalent temperature field is obtained. Furthermore, a FE analysis is performed for each of the above cases, applying the respective temperature field to the spherical vessel. The induced stress fields are evaluated for each case and then compared to the original stress. The FE results prove that the proposed procedure yields equivalent temperature fields that in turn simulate very accurately the residual stress fields for both the ideal and the realistic autofrettage cases.

A Validated Numerical Model for Residual Stress Predictions in an Eight-Pass-Welded Stainless Steel Plate

2014 ◽  
Vol 777 ◽  
pp. 46-51 ◽  
Author(s):  
Vipulkumar I. Patel ◽  
Ondrej Muránsky ◽  
Cory J. Hamelin ◽  
Mitch D. Olson ◽  
Michael R. Hill ◽  
...  
Keyword(s):  
Residual Stress ◽  
Stainless Steel ◽  
Stress Field ◽  
Steel Plate ◽  
Fe Analysis ◽  
Contour Method ◽  
Stainless Steel Plate ◽  
Residual Stress Field ◽  
Longitudinal Residual Stress ◽  
Welding Processes

Welding processes create a complex transient state of temperature that results in post-weld residual stresses. The current work presents a finite element (FE) analysis of the residual stress distribution in an eight-pass slot weld, conducted using a 316L austenitic stainless steel plate with 308L stainless steel filler metal. A thermal FE model is used to calibrate the transient thermal profile applied during the welding process. Time-resolved body heat flux data from this model is then used in a mechanical FE analysis to predict the resultant post-weld residual stress field. The mechanical analysis made use of the Lemaitre-Chaboche mixed isotropic-kinematic work-hardening model to accurately capture the constitutive response of the 316L weldment during the simulated multi-pass weld process, which results in an applied cyclic thermo-mechanical loading. The analysis is validated by contour method measurements performed on a representative weld specimen. Reasonable agreement between the predicted longitudinal residual stress field and contour measurement is observed, giving confidence in the results of measurements and FE weld model presented.

Three-Dimensional Dynamic Explicit Finite Element Analysis of Charpy Impact Test

2016 ◽  
Vol 879 ◽  
pp. 1905-1910 ◽  
Author(s):  
Yasuhito Takashima ◽  
Tsunehisa Handa ◽  
Fumiyoshi Minami
Keyword(s):  
Stress Field ◽  
Impact Load ◽  
Contact Stiffness ◽  
Three Dimensional ◽  
Charpy Impact ◽  
Charpy Impact Test ◽  
Fe Analysis ◽  
Charpy Specimen ◽  
Explicit Finite Element ◽  
The Impact

Dynamic explicit finite element (FE) analysis of the Charpy impact test was conducted in this study to investigate the inertial effect on the stress field ahead of the V-notch in a Charpy specimen. The deformation behavior of the Charpy specimen and the constraint effect on the stress field in the plastic zone near the V-notch were numerically simulated using three-dimensional FE analysis, while considering the contact of the specimen with the striker and anvil. The effect of the strain rate on the flow stress and the increase in temperature during impact loading were included in the dynamic analysis. This analysis shows that the impact load exhibits oscillation and the contact stiffness between the specimen and the striker affects the oscillation of the impact load. The analysis was validated by comparison with experimental results obtained using an instrumented Charpy impact testing machine, which measured the impact load and the load point displacement. The oscillation of the load–time curve was recorded. The magnitude and period of the peak inertia load obtained by the FE analysis were almost consistent with the experimental results. The contact stiffness between the specimen and the striker affected the stress field near the V-notch in the specimen. This indicates that the stress field in the Charpy specimen should be analyzed by the dynamic analysis procedure considering the contact stiffness based on the Hertzian contact theory.

A Novel Dynamic Bone Stress Evaluation Method of Postoperative Proximal Femur During Gait by Using Elastic Multi Body Analysis Based on Finite Element Analysis

2017 ◽  
Author(s):  
Yukiko Nakamura ◽  
Kazuhiko Adachi ◽  
Nungna Wi ◽  
Mitsuaki Noda
Keyword(s):  
Finite Element ◽  
Stress Distribution ◽  
Boundary Conditions ◽  
Hip Joint ◽  
Proximal Femur ◽  
Dynamic Stress ◽  
Fe Analysis ◽  
Patient Specific ◽  
Time Varying ◽  
Multi Body

A proximal femur fracture due to osteoporosis is one of serious health care problems in aging societies. Osteosynthesis with pin or screw type of implants, such as Hansson pin (HP), Dual SC Screw (DSCS), is widely used for femoral neck fracture treatment in Japan. Unfortunately, some complications such as secondary fractures, especially peri-prosthetic fractures, may occur during postoperative rehabilitation period. In order to reveal the potential cause of the postoperative fracture from the viewpoint of the biomechanics, authors had already performed the dynamic stress analysis of the treated proximal femur based on finite element (FE) analysis. The final goal of our project is to establish the reliable postoperative bone fracture risk assessment method in response to the daily activity including mainly walking. The aim of this study is to propose a novel elastic multi body analysis method based on FE analysis for proximal femur biomechanics. Patient-specific 3D left hip joint FE model was constructed from an elderly female volunteer’s CT images. The model consists of the pelvis, proximal femur, cartilage and DSCS, as multi bodies. The dynamic loading and boundary conditions were applied to the model for simulating a gait motion. Direction and magnitude of the loads varies in response to the gait motion. The time dependent loading forces; hip contact, gluteus medius, gluteus maximus, tensor fasciae latae and adductor, acting around the hip joint was obtained by inverse dynamic analysis of a human gait using in-house lower-limb musculoskeletal model. These loading and boundary conditions for simulating the gait motion are the major technical advantages of the proposed multi body analysis comparing with the conventional static FE analysis. Time varying stress distribution during the gait was evaluated by using dynamic explicit method via ABAQUS. In order to visually demonstrate dynamic stress distribution, we examined the time varying von Mises stresses at the representative points located on the cortical surface of the proximal femur; femoral head, fracture surface and around the lateral insertion holes. The results indicate significant increase of the stresses around the proximal lateral insertion holes for DSCS treatment. Maximum stress values are good agreement with the previous static FE analysis, on the other hand, these biomechanical discussions based on the stress time histories are only obtained from the proposed method. It is indicated that the proposed method is feasible to support the better pre- and postoperative clinical decisions, which is the main contribution of this study.

Validation of subject-specific automated p-FE analysis of the proximal femur

2009 ◽  
Vol 42 (3) ◽  
pp. 234-241 ◽  
Author(s):  
Nir Trabelsi ◽  
Zohar Yosibash ◽  
Charles Milgrom
Keyword(s):  
Proximal Femur ◽  
Fe Analysis ◽  
Subject Specific

Evaluation of Crack Tip Stress Field Using Combination of Advanced Implementation of Over-Deterministic Method and FE Analysis

2014 ◽  
Vol 627 ◽  
pp. 273-276 ◽  
Author(s):  
Jakub Sobek ◽  
T. Pail ◽  
Václav Veselý
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Stress Field ◽  
Crack Tip ◽  
Fe Analysis ◽  
Deterministic Method ◽  
Element Analysis ◽  
Java Programming ◽  
Higher Order Terms ◽  
Selection Of

Creation of an automatic utility to determine the values of coefficients of higher order terms of Williams power series by usage of over-deterministic method applied to results of finite element analysis is a main goal of this research. The developed procedure based on the support of Java programming language considerably simplifies analyses on optimization of selection of FE nodal results for improvement of accuracy of the near-crack-tip fields’ approximation using Williams series.

Observation of secondary slip systems in tungsten bicrystals

1984 ◽  
Vol 42 ◽  
pp. 478-479
Author(s):  
J. R. Fekete ◽  
R. Gibala
Keyword(s):  
Stress Field ◽  
Grain Boundaries ◽  
Deformation Behavior ◽  
Stress Axis ◽  
Polycrystalline Materials ◽  
Slip Systems ◽  
Metallic Materials ◽  
Twist Boundary ◽  
Secondary Slip ◽  
Plane Normal

The deformation behavior of metallic materials is modified by the presence of grain boundaries. When polycrystalline materials are deformed, additional stresses over and above those externally imposed on the material are induced. These stresses result from the constraint of the grain boundaries on the deformation of incompatible grains. This incompatibility can be elastic or plastic in nature. One of the mechanisms by which these stresses can be relieved is the activation of secondary slip systems. Secondary slip systems have been shown to relieve elastic and plastic compatibility stresses. The deformation of tungsten bicrystals is interesting, due to the elastic isotropy of the material, which implies that the entire compatibility stress field will exist due to plastic incompatibility. The work described here shows TEM observations of the activation of secondary slip in tungsten bicrystals with a [110] twist boundary oriented with the plane normal parallel to the stress axis.

Bone and Bone Marrow Blood Flow in Blastic Crisis of Chronic Granulocytic Leukaemia

1979 ◽  
Vol 18 (06) ◽  
pp. 290-292 ◽  
Author(s):  
R. Lahtinen ◽  
T. Lahtinen
Keyword(s):  
Bone Marrow ◽  
Cell Proliferation ◽  
Blood Flow ◽  
Proximal Femur ◽  
Blastic Crisis ◽  
Normal Bone ◽  
Chronic Granulocytic Leukaemia ◽  
Washout Curves ◽  
Bone Marrow Blood

SummaryA l33Xe washout method has been used for measuring changes of blood flow in the proximal femur of a patient with the blastic crisis of chronic granulocytic leukaemia. In the hyperplastic phase the blood flow was highly increased and over three times greater than in the hypoplastic phase of the disease and over thirteen times greater than the value in normal bone. The bone circulation and especially the first component of the two-exponential bone washout curves appeared to reflect cell proliferation and neoplastic activity of the whole bone marrow. The method may provide clinically important information in the follow-up of selected haematological diseases.

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