Local Variations of Strain and Strain Rate in Roll Bite Region During Rolling of Steels

1998 ◽  
Vol 120 (1) ◽  
pp. 86-96 ◽  
Author(s):  
Ampere A. Tseng ◽  
Shi R. Wang ◽  
A. C. W. Lau
Keyword(s):  
Finite Element ◽  
Cold Rolling ◽  
Strain Rate ◽  
Hot Rolling ◽  
Numerical Approach ◽  
Spatial Variations ◽  
Rate Variation ◽  
Strain And Strain Rate ◽  
Before And After ◽  
Roll Bite

A combined experimental-numerical approach has been developed to quantify the strain rate variation of the workpiece in the roll bite region. In this approach, cold rolling experiments at a production mill were conducted first. Then tensile and microhardness tests were performed on workpieces before and after cold rolling to establish the relationship between the microhardness and plastic strain of the material. Microhardness measurements were also conducted in the roll bite region on a partially cold rolled workpiece. A finite element rolling simulation was performed to predict the spatial variations of the strain and strain rate. Through microhardness matching, it was found that the finite-element predicted strains agree very well with those actually existing in the rolled workpiece. Consequently, the finite-element predicted strain rates, whose time-accumulation directly gave strains which matched the actual strains, were verified. Finally, a finite-element simulation of both cold and hot rolling was conducted to assess the effect of several major rolling parameters on the strain rate variation in the bite region. Results show that the spatial variations of strain rate in the roll bite region are extremely nonuniform for both cold and hot rolling.

scholarly journals Embedded axonal fiber tracts improve finite element model predictions of traumatic brain injury

2019 ◽  
Vol 19 (3) ◽  
pp. 1109-1130 ◽  
Author(s):  
Marzieh Hajiaghamemar ◽  
Taotao Wu ◽  
Matthew B. Panzer ◽  
Susan S. Margulies
Keyword(s):  
Traumatic Brain Injury ◽  
Finite Element ◽  
Brain Injury ◽  
Strain Rate ◽  
Brain Tissue ◽  
Brain Injuries ◽  
Characteristic Curve ◽  
Strain And Strain Rate

AbstractWith the growing rate of traumatic brain injury (TBI), there is an increasing interest in validated tools to predict and prevent brain injuries. Finite element models (FEM) are valuable tools to estimate tissue responses, predict probability of TBI, and guide the development of safety equipment. In this study, we developed and validated an anisotropic pig brain multi-scale FEM by explicitly embedding the axonal tract structures and utilized the model to simulate experimental TBI in piglets undergoing dynamic head rotations. Binary logistic regression, survival analysis with Weibull distribution, and receiver operating characteristic curve analysis, coupled with repeated k-fold cross-validation technique, were used to examine 12 FEM-derived metrics related to axonal/brain tissue strain and strain rate for predicting the presence or absence of traumatic axonal injury (TAI). All 12 metrics performed well in predicting of TAI with prediction accuracy rate of 73–90%. The axonal-based metrics outperformed their rival brain tissue-based metrics in predicting TAI. The best predictors of TAI were maximum axonal strain times strain rate (MASxSR) and its corresponding optimal fraction-based metric (AF-MASxSR7.5) that represents the fraction of axonal fibers exceeding MASxSR of 7.5 s−1. The thresholds compare favorably with tissue tolerances found in in–vitro/in–vivo measurements in the literature. In addition, the damaged volume fractions (DVF) predicted using the axonal-based metrics, especially MASxSR (DVF = 0.05–4.5%), were closer to the actual DVF obtained from histopathology (AIV = 0.02–1.65%) in comparison with the DVF predicted using the brain-related metrics (DVF = 0.11–41.2%). The methods and the results from this study can be used to improve model prediction of TBI in humans.

Finite Element Analysis and Experimental Study on the Effect of Extrusion Ratio during Hot Extrusion Process of Aluminium Matrix Composites

2017 ◽  
Vol 67 (4) ◽  
pp. 428 ◽  
Author(s):  
Dhanalakshmi Sathishkumar ◽  
P. Sivakumar ◽  
K. Shanmuga Sundaram ◽  
S. Anand
Keyword(s):  
Finite Element ◽  
Strain Rate ◽  
Hot Extrusion ◽  
Extrusion Process ◽  
Fe Analysis ◽  
Extrusion Ratio ◽  
Aluminium Matrix ◽  
Matrix Composites ◽  
Aluminium Matrix Composites ◽  
Strain And Strain Rate

The finite element (FE) analysis on the effect of extrusion process parameter namely, extrusion ratio at different billet temperatures on the plastic strain and strain rate of aluminium matrix composite during hot extrusion process has been dealt. The dynamic explicit FE code in ANSYS 15.0 workbench was used for simulation. The FE analysis was carried out on the SiC reinforced aluminium matrix composites for three extrusion ratios 4:1, 8:1 and 15:1, for the billet temperatures in the range 350 °C - 450 °C in steps of 50 °C. The plastic strain and strain rate were found to increase with increase in the extrusion ratio. A minimum strain and strain rate was found to occur at the billet temperature of 450 °C. The silicon carbide particles reinforced aluminium matrix composites were then extruded at the optimised temperature of 450 °C for various extrusion ratios as mentioned above. The effect of extrusion ratio on the microstructure and surface quality of extruded rod was studied.

Analysis of Heat Transfer and Straightening of Continuous Casting Slab Using 3D Finite Element Method

2011 ◽  
Vol 418-420 ◽  
pp. 1698-1702
Author(s):  
Qing Guo Liu ◽  
Xing Zhong Zhang ◽  
Zheng Yi Jiang ◽  
Yan Chao Sun ◽  
Bao Jun Shi ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Finite Element Method ◽  
Finite Element ◽  
Strain Rate ◽  
Three Dimensional ◽  
Three Dimension ◽  
Element Analysis ◽  
Strain And Strain Rate ◽  
Three Dimensional Finite Element ◽  
Element Method

The straightening of curved slab results in a greater straightening strain. During the process of multi-point straightening, the peak value of the straightening strain rate will appear at each straightening point. If the strain rate is too large, the straightening cracks will appear. Solidification and heat transfer of a slab is analyzed and the generation of the solidified shell and the three-dimension temperature field of the slab are calculated by using three-dimensional finite element method (FEM). Based on the finite element analysis of five-point straightening of the curved slab, the strain and strain rate of each straightening point were obtained, which is a base of the analysis of straightening cracks.

Right and Left Ventricular Strain and Strain Rate in Young Adults before and after Percutaneous Atrial Septal Defect Closure

2011 ◽  
Vol 28 (7) ◽  
pp. 730-737 ◽  
Author(s):  
Claudio Bussadori ◽  
Pedro Oliveira ◽  
Carmelo Arcidiacono ◽  
Antonio Saracino ◽  
Elisa Nicolosi ◽  
...  
Keyword(s):  
Young Adults ◽  
Atrial Septal Defect ◽  
Strain Rate ◽  
Septal Defect ◽  
Left Ventricular ◽  
Defect Closure ◽  
Atrial Septal Defect Closure ◽  
Left Ventricular Strain ◽  
Strain And Strain Rate ◽  
Before And After

scholarly journals Two-dimensional speckle tracking echocardiography in goats: repeatability, variability, and validation of the technique using an exercise test and an experimentally induced acute ischemic cardiomyopathy.

2019 ◽  
Author(s):  
Aurelia A Leroux ◽  
Marie Moonen ◽  
Frédéric Farnir ◽  
Stefan Deleuze ◽  
Charlotte Sandersen ◽  
...  
Keyword(s):  
Strain Rate ◽  
Rotation Rate ◽  
Speckle Tracking ◽  
Ischemic Cardiomyopathy ◽  
Animal Species ◽  
Radial Strain ◽  
Two Dimensional ◽  
Pathological Changes ◽  
Strain And Strain Rate ◽  
Before And After

Abstract Background : Two-dimensional speckle tracking (2DST) technique has been validated in numerous animal species, but neither studies of repeatability, nor measurements after exercise or in animals with cardiac disease have been reported in goats. Therefore, the aim of this study was to validate this technique in goats for further clinical and experimental applications in this species. This study was divided into several steps. First, a standardized echocardiographic protocol including several right parasternal short-axis views at papillary muscles level was performed three times at one-day intervals in ten healthy adult unsedated Saanen goats to test repeatability and variability of 2DST measurements. Then, the same measurements were performed immediately before and after a standardized exercise on treadmill in seven of the goats, and at 24h after induction of an experimental ischemic cardiomyopathy in five of the goats, to test the reliability of the technique to assess physiological and pathological changes. Results: Global and regional measurements of radial and circumferential strain and strain rate, radial displacement, rotation and rotation rate were obtained. Comparisons were performed using ANOVA II (p<0.05). Caprine 2DST measurements demonstrated a good repeatability for global measurements except for the late diastolic peak of the circumferential and radial strain rate. Segmental 2DST measurements were also repeatable except for the anteroseptal segment diastolic peaks and several rotation and rotation rate measurements. Overall variability was moderate to high. Segmental and global peak values obtained after exercise and after myocardial ischemia were significantly different than curves obtained at baseline. Conclusions: The results of this study are consistent with those previously described in other animal species and humans. 2DST echocardiography is a valid technique to evaluate physiological and pathological changes in myocardial function in goats, despite the technical limitations observed in this species.

Macro-Micro Biomechanics Finite Element Modeling of Brain Injury Under Concussive Loadings

2016 ◽  
Author(s):  
X. Gary Tan ◽  
Andrzej J. Przekwas ◽  
Raj K. Gupta
Keyword(s):  
Finite Element ◽  
Brain Injury ◽  
White Matter ◽  
Strain Rate ◽  
Material Behavior ◽  
Tau Proteins ◽  
Beam Model ◽  
Strain And Strain Rate ◽  
Starting Point ◽  
Macro Scale

Traumatic brain injury (TBI) occurs in many blunt, ballistic and blast impact events. During trauma axons in the white matter are especially vulnerable to injury due to the rapid mechanical loading of brain. The axonal pathology leads to cytoskeletal failure and disconnection. The microtubules are one of major structural components of the cytoskeleton filamentous network. By bridging the macroscopic forces acting on the whole brain with the cellular and subcellular failure, the macro-micro computational models in both time and space can help us better understand the complex biophysics and elucidate the injury mechanism of both severe and mild TBI (concussion). At the macroscopic scale we developed the high-fidelity anatomical human body finite element model (FEM) to predict intracranial pressures and strain and strain rate fields of brain in the blast event. The macro-scale models and the coupled blast and biomechanics approach were validated against test data of shock wave interacting with a surrogate head in the shock tube. The mechanical deformation of brain tissue was mapped to the white matter tracts to obtain local axonal strain and strain rate for the micromechanical models. We developed the micromechanical FEM of myelinated axons interconnected with the oligodendrocyte by the processes, utilizing a novel beam element free of rotational degrees of freedom (DOFs). The numerical results reveal the possible mechanism of impact-induced axon injury including demyelination, breakup of processes, and axonal varicosity. We also investigate the dynamic response of microtubules bundles under traumatic loading. Different from the commonly discrete bead-spring models, a network of microtubules cross-linked with microtubule-associated-protein (MAP) tau proteins was modeled by the nonlinear beam model. Tau protein is modeled by the rate-dependent bar element for its complicated material behavior. The model considers the rupture of microtubule and the failure of tau-tau interface and tau-microtubule interface. The simulation result of the combined effects of the failure of the cross-linked architecture and elongation and bending of the bundle are possibly correlated to the axonal undulations following traumatic loading observed in the experiments. The developed macro-micro biomechanics models can be used as a starting point for modeling the neurobiology effects and guide the design of novel injury protection strategies.

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