Experimentally tested computer modeling of stress fractures in rats

2011 ◽  
Vol 110 (4) ◽  
pp. 909-916 ◽  
Author(s):  
Michal Stern-Perry ◽  
Amit Gefen ◽  
Nogah Shabshin ◽  
Yoram Epstein
Keyword(s):  
Three Dimensional ◽  
Muscle Stiffness ◽  
Male Rats ◽  
Cyclic Loads ◽  
Fe Model ◽  
Stress Distributions ◽  
Fe Modeling ◽  
Sprague Dawley ◽  
Modeling Methodology ◽  
Strain Stress

The objective of this study was to develop a finite-element (FE) modeling methodology for studying the etiology of a stress fracture (SF). Several variants of three-dimensional FE models of a rat hindlimb, which differed in length or stiffness of tissues, enabling the analyses of mechanical strains and stress in the tibia, were created. We compared the occurrence of SFs in an animal model to validate locations of peak strains/stresses in the FE models. Four Sprague-Dawley male rats, age ∼7 wk, were subjected to mechanical cyclic loads of 1.2 Hz and ∼6 N, which were delivered to their hindlimb for 30 min, 3 times/wk, up to 12 wk, by using a specially designed apparatus. The results showed that 1) FE modeling predicted the maximal strains/stresses (∼220,0 με and ∼29 MPa, respectively) between the mid- and proximal thirds of the tibia; 2) in a longer shin, greater and more inhomogeneous tensile strains/stresses were evident, at the same location; 3) anatomical variants in shin length influenced the strain/stress distributions to a greater extent with respect to changes in mechanical properties of tissues; and 4) bone stiffness was more dominant than muscle stiffness in affecting the strain/stress distributions. In the animal study, 35,000 loading cycles were associated with the formation of a SF. The location of the identified SF in the rat limb verified the FE model. We find the suggested model a valuable tool in studying various aspects of SFs.

Residual Stress Prediction for Non-Axisymmetric Vessel Penetration Welds

2008 ◽  
Author(s):  
Kazuo Ogawa ◽  
Nobuyoshi Yanagida ◽  
Koichi Saito
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Three Dimensional ◽  
Measurement Data ◽  
Fe Model ◽  
Stress Distributions ◽  
Dimensional Finite Element ◽  
Stress Prediction ◽  
Three Dimensional Finite Element ◽  
Good Agreement

Residual stress distribution in an oblique nozzle jointed to a vessel with J-groove welds was analyzed using a three-dimensional finite element method. All welding passes were considered in a 180-degree finite element (FE) model with symmetry. Temperature and stress were modeled for simultaneous bead laying. To determine residual stress distributions at the welds experimentally, a mock-up specimen was manufactured. The analytical results show good agreement with the experimental measurement data, indicating that FE modeling is valid.

Design of a rotor blade tip for the investigation of dynamic stall in the transonic wind-tunnel Göttingen

2016 ◽  
Vol 120 (1232) ◽  
pp. 1509-1533 ◽  
Author(s):  
B. Lütke ◽  
J. Nuhn ◽  
Y. Govers ◽  
M. Schmidt
Keyword(s):  
Experimental Data ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Numerical Data ◽  
Dynamic Stall ◽  
Navier Stokes ◽  
Fe Model ◽  
Stress Distributions ◽  
Cfd Simulations ◽  
Blade Tip

ABSTRACTThe aerodynamic and structural design of a pitching blade tip with a double-swept planform is presented. The authors demonstrate how high-fidelity finite element (FE) and computational fluid dynamic (CFD) simulations are successfully used in the design phase. Eigenfrequencies, deformation, and stress distributions are evaluated by means of a three-dimensional (3D) FE model. Unsteady Reynolds-averaged Navier-Stokes (RANS) simulations are compared to experimental data for a light dynamic stall case atMa= 0.5,Re= 1.2 × 106. The results show a very good agreement as long as the flow stays attached. Tendencies for the span-wise location of separation are captured. As soon as separation sets in, discrepancies between experimental and numerical data are observed. The experimental data show that for light dynamic stall cases atMa= 0.5, a factor of safety ofFoS= 2.0 is sufficient if the presented simulation methods are used.

FE Modeling of Elliptical Concrete-Filled Steel Tubular Members Subjected to Pure Bending

2013 ◽  
Vol 859 ◽  
pp. 105-108
Author(s):  
Xiong Zhao ◽  
Xu Kuan Li ◽  
Qing Xin Ren ◽  
Tai Cheng ◽  
Xiao Lian Long
Keyword(s):  
Failure Modes ◽  
Steel Tube ◽  
Fe Model ◽  
Stress Distributions ◽  
Fe Modeling ◽  
Pure Bending ◽  
Element Analysis ◽  
Elliptical Section ◽  
As Stress ◽  
Good Agreement

This paper reports a finite element analysis of the flexural behaviour of concrete-filled steel tubular members with elliptical section. A set of test data were used to verify the FE modeling. generally, good agreement was achieved. Typical curves of moment (M) versus deflection at mid-span (um), as well as stress distributions of steel tube and concrete of the composite members were compared and discussed. The results clearly show that the FE model is available for predicting the load-bearing capacities and the failure modes of the specimens.

Effect of Deep Cold Rolling on Residual Stress Distributions Between the Treated and Untreated Regions on Ti–6Al–4V Alloy

2016 ◽  
Vol 138 (11) ◽  
Author(s):  
Andre Lim ◽  
Sylvie Castagne ◽  
Chow Cher Wong
Keyword(s):  
Residual Stress ◽  
Cold Rolling ◽  
Tool Path ◽  
Rolling Direction ◽  
Three Dimensional ◽  
Fe Model ◽  
Stress Distributions ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element ◽  
Step Over

The residual stress distributions caused by the deep cold rolling (DCR) process, with a focus on the distributions at the boundary of the treatment zone, are examined in this study. A three-dimensional finite-element (FE) model, validated with experimental residual stress data, is used to study the effect of the process. The residual stress distribution in the crosswise direction (perpendicular to rolling direction) shows a region of tensile residual stress at the start and end of the track that may be a cause for concern. The reason for this region of tensile stress is likely to be due to the reduced treatment of the start and end zones due to the step over and the tool path taken. Other factors that cause a difference between the steady state and the transient zone of the burnished area are also investigated. It is shown that the net material movement causes larger plastic deformation in the boundary zone between the burnished and unburnished region of DCR.

Application of Sub-Modeling in the Finite Element Analysis of a Large Fixed Tubesheet Heat Exchanger

2017 ◽  
Author(s):  
Bingjun Gao ◽  
Bin Liu ◽  
Junhua Dong ◽  
JinHua Shi
Keyword(s):  
Finite Element ◽  
Stress Field ◽  
Maximum Stress ◽  
Fe Model ◽  
Fe Modeling ◽  
Element Analysis ◽  
Modeling Methodology ◽  
Stress Point ◽  
Solid Plate ◽  
Coarse Model

There are enormous tubes in large fixed tubesheet heat exchangers making it difficult to model all the tubes and tubesheet connections in detail for a finite element (FE) analysis. Alternatively, an equivalent solid plate with various simplified tube connections are employed in the FE modeling. But this fails to yield an accurate stress field around the connecting region of tubes and the tubesheet. Given that the maximum stress of the equivalent solid plate generally occurs adjacent to the solid tubesheet, a novel finite element modeling methodology is proposed in this paper. A two part process is used. The first part is a coarse FE model and the second part is a more detailed FE model. In the coarse FE model, the equivalent solid plate is employed in the central region of the tubesheet with simplified tube connections such as equivalent cylinder by multi-points contacting. And quasi detailed tube and tubesheet connections are used in the coarse FE model for the region adjacent to the solid plate, in which the tube and the tubesheet are simply connected with same nodes. This means that both tubesheet and tubes are established in this quasi detailed FE modeling region. Although both the weld and contacting condition between the tube and the tubesheet are not included, the coarse model is enough to yield a believable stress field for the determination of the maximum stress point of the quasi detailed FE modeling region. In the second part, the sub-model methodology is utilized in the predetermined maximum stress point, in which the detailed connecting structure of the tube and the tubesheet is included, such as the weld and the contact condition. The proposed modeling methodology is helpful to have an insight into the stress around the connecting region of the tube and tubesheet for the effective evaluation of the tubesheet and the connection.

Preliminary Analysis on Inclined Concrete-Filled Steel Tubular Stub Columns with Circular Section under Axial Compression

2011 ◽  
Vol 88-89 ◽  
pp. 46-49 ◽  
Author(s):  
Qing Xin Ren ◽  
Yan Bo Lv ◽  
Lian Guang Jia ◽  
De Qing Liu
Keyword(s):  
Failure Modes ◽  
Stress Distributions ◽  
Fe Modeling ◽  
Steel Tubes ◽  
Element Analysis ◽  
Circular Section ◽  
Composite Columns ◽  
Strain Stress ◽  
Stub Columns ◽  
As Effects

This paper reports a finite element analysis of the compressive behaviour of circular inclined CFST stub columns. A set of test data were used to verify the FE modeling. Typical curves of vertical load versus longitudinal strain, stress distributions of concrete, interaction of concrete and steel tubes, as well as effects of important parameters that determine failure modes of the composite columns were investigated. The results clearly show that the FE modeling is available for predicting the capacities of the circular inclined specimens.

Structural and Thermal Analyses of Pressure Vessel Bottom Head With Penetration Holes

2005 ◽  
Author(s):  
David W. Wu ◽  
Raymond K. Yee
Keyword(s):  
Finite Element ◽  
Pressure Vessel ◽  
Thermal Analyses ◽  
Three Dimensional ◽  
Fe Model ◽  
Stress Distributions ◽  
Pressure Loading ◽  
Stress Concentrations ◽  
Control Rod ◽  
Vessel Bottom

The paper presents a three-dimensional (3-D) finite element (FE) model of a nuclear pressure vessel and the analyses results under typical loadings using ANSYS finite element code. Structural analyses of the vessel with internal pressure loading and thermal transient loading are described. The main focus of the analysis is on the bottom head shell with the Control Rod Drive (CRD) penetration holes. The vessel support skirt and selected CRD housing/welds that attached to the bottom head shell are included in the model. The objective of this study is to assess the bottom head stress distributions of a nuclear pressure vessel, especially the stress concentrations due to the CRD penetration openings. The calculated stresses around uphill oblique holes in the vessel are compared with those around the normal facing center penetration hole. The preliminary results and conclusions drawn from the study are presented in the paper.

On the Thermal Performance Characteristics of Three-Dimensional Multichip Modules

2004 ◽  
Vol 126 (3) ◽  
pp. 374-383 ◽  
Author(s):  
Wen-Hwa Chen ◽  
Hsien-Chie Cheng ◽  
Chih-Han Lin
Keyword(s):  
Heat Transfer ◽  
Heat Conduction ◽  
Thermal Performance ◽  
Three Dimensional ◽  
Empirical Models ◽  
Thermal Design ◽  
Fe Model ◽  
Fe Modeling ◽  
Ir Thermography ◽  
Design Guideline

The study explores the thermal performance of three-dimensional (3-D), vertically stacked multi-chip modules (the so-called MCM-V) in natural convection through finite element (FE) modeling and experimental validation. A modified Infrared (IR) thermography-based thermal characterization (IRTTC) technique that integrates a 3-D heat conduction FE modeling and a two-phased IR thermography measurement process is proposed. In contrast to the conventional IRTTC technique (Chen et al. [1]), the technique can improve the resolution of the captured thermal images so as to attain better characterization of the chip junction temperature. The effectiveness of the proposed modified IRTTC technique is confirmed by means of the thermal test die (TTD) measurement. Furthermore, for facilitating subsequent parametric thermal design, a direct FE approach (DFEA) is also introduced. The DFEA simply incorporates existing empirical models for heat transfer (HT) coefficients to describe the surface heat transfer to the ambient through convection and radiation in the proposed heat conduction FE model. Through the modified IRTTC technique and the TTD measurement, the validity of the proposed FE modeling, including the proposed heat conduction FE model and the applied empirical models for HT coefficients, is verified. With the validated FE modeling, four different chip stacking structures of MCM-V packages, including the thick-die-attach, pyramid, cross and dummy-die types, are investigated. In addition, some essential design factors, affecting the thermal performance of the MCM-V, are also extensively explored through parametric FE study. Eventually, an extensive thermal design guideline is accordingly provided.

Methods for making stereoslides and -prints, with freeze-etched olfactory epithelium as example

1984 ◽  
Vol 42 ◽  
pp. 704-705
Author(s):  
Bert Ph. M. Menco ◽  
Ido F. Menco ◽  
Frans L.T. Verdonk
Keyword(s):  
Electron Microscope ◽  
Olfactory Epithelium ◽  
Three Dimensional ◽  
Supporting Cell ◽  
Structural Features ◽  
Extensive Study ◽  
Sprague Dawley ◽  
Freezing Method ◽  
Respiratory Epithelia ◽  
Three Dimensional Presentation

Previously we presented an extensive study of the distributions of intramembranous particles of structures in apical surfaces of nasal olfactory and respiratory epithelia of the Sprague-Dawley rat. For the same structures these distributions were compared in samples which were i) chemically fixed and cryo-protected with glycerol before cryo-fixation, after excision, and ii)ultra-rapidly frozen by means of the slam-freezing method. Since a three-dimensional presentation markedly improves visualization of structural features micrographs were presented as stereopairs. Two exposures were made by tiling the sample stage of the electron microscope 6° in either direction with an eucentric goniometer. The negatives (Agfa Pan 25 Professional) were reversed with Kodak Technical Pan Film 2415 developed in D76 1:1. The prints were made from these reversed negatives. As an example tight-junctional features of an olfactory supporting cell in a region where this cell conjoined with two other cells are presented (Fig. 1).

scholarly journals Comparison of Tooth- and Bone-Borne Appliances on the Stress Distributions and Displacement Patterns in the Facial Skeleton in Surgically Assisted Rapid Maxillary Expansion—A Finite Element Analysis (FEA) Study

Materials ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1152
Author(s):  
Rafał Nowak ◽  
Anna Olejnik ◽  
Hanna Gerber ◽  
Roman Frątczak ◽  
Ewa Zawiślak
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Three Dimensional ◽  
Element Model ◽  
Rapid Maxillary Expansion ◽  
Stress Distributions ◽  
Maxillary Expansion ◽  
Facial Skeleton ◽  
Element Analysis ◽  
Maxillary Constriction

The aim of this study was to compare the reduced stresses according to Huber’s hypothesis and the displacement pattern in the region of the facial skeleton using a tooth- or bone-borne appliance in surgically assisted rapid maxillary expansion (SARME). In the current literature, the lack of updated reports about biomechanical effects in bone-borne appliances used in SARME is noticeable. Finite element analysis (FEA) was used for this study. Six facial skeleton models were created, five with various variants of osteotomy and one without osteotomy. Two different appliances for maxillary expansion were used for each model. The three-dimensional (3D) model of the facial skeleton was created on the basis of spiral computed tomography (CT) scans of a 32-year-old patient with maxillary constriction. The finite element model was built using ANSYS 15.0 software, in which the computations were carried out. Stress distributions and displacement values along the 3D axes were found for each osteotomy variant with the expansion of the tooth- and the bone-borne devices at a level of 0.5 mm. The investigation showed that in the case of a full osteotomy of the maxilla, as described by Bell and Epker in 1976, the method of fixing the appliance for maxillary expansion had no impact on the distribution of the reduced stresses according to Huber’s hypothesis in the facial skeleton. In the case of the bone-borne appliance, the load on the teeth, which may lead to periodontal and orthodontic complications, was eliminated. In the case of a full osteotomy of the maxilla, displacements in the buccolingual direction for all the variables of the bone-borne appliance were slightly bigger than for the tooth-borne appliance.

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