scholarly journals Analysis of the Elastoplastic Response in the Torsion Test Applied to a Cylindrical Sample

Materials ◽  
2019 ◽  
Vol 12 (19) ◽  
pp. 3200
Author(s):  
Sebastián Andrés Toro ◽  
Pedro Miguel Aranda ◽  
Claudio Moisés García-Herrera ◽  
Diego Javier Celentano
Keyword(s):  
Large Strain ◽  
Twist Angle ◽  
Strain Tensor ◽  
Torsion Test ◽  
Cylindrical Sample ◽  
Image Correlation ◽  
Experimental Methodology ◽  
Lagrange Strain ◽  
Fixed End ◽  
1045 Steel

This work presents an experimental and numerical analysis of the mechanical behavior of a fixed-end SAE 1045 steel cylindrical specimen during the torsion test. To this end, an iterative numerical–experimental methodology is firstly proposed to assess the material response in the tensile test using a large strain elastoplasticity-based model solved in the context of the finite element method. Then, a 3D numerical simulation of the deformation process of the torsion test is tackled with this previously characterized model that proves to be able to predict the development of a high and localized triaxial stress and strain fields caused by the presence of high levels of angular deformation. Finally, the obtained numerical results are analytically studied with the cylindrical components of the Green–Lagrange strain tensor and experimentally validated with the measurements of shear strains via Digital Image Correlation (DIC) and the corresponding torque – twist angle curve.

Determination of Shear Stress-Strain Curve From Torsion Tests for Loading-Unloading and Cyclic Loading

1997 ◽  
Vol 119 (1) ◽  
pp. 113-115 ◽  
Author(s):  
Han-Chin Wu ◽  
Zhiyou Xu ◽  
Paul T. Wang
Keyword(s):  
Shear Stress ◽  
Cyclic Loading ◽  
Large Strain ◽  
Strain Curve ◽  
Strain Range ◽  
Torsion Test ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Modified Method ◽  
Fixed End

This paper discusses a method, based on Nadai’s solution, which can be used to determine the true (Cauchy) shear stress-strain curve of a material by means of torsion test of a solid shaft. The method is shown to be applicable to loading, unloading and cyclic loading. It is also applicable to fixed-end torsion of a solid shaft in the large shear strain range. A modified method has also been derived for the case of free-end torsion of a tubular specimen in the large strain range.

NONLINEAR ANALYSIS OF FUNCTIONALLY GRADED CIRCULAR PLATES UNDER DIFFERENT LOADS AND BOUNDARY CONDITIONS

2008 ◽  
Vol 08 (01) ◽  
pp. 131-159 ◽  
Author(s):  
RECEP GUNES ◽  
J. N. REDDY
Keyword(s):  
Nonlinear Analysis ◽  
Strain Tensor ◽  
Homogenization Method ◽  
Functionally Graded ◽  
Gradient Material ◽  
Graphical Form ◽  
Circular Plates ◽  
Geometrically Nonlinear Analysis ◽  
Steady State Heat Transfer ◽  
Lagrange Strain

Geometrically nonlinear analysis of functionally graded circular plates subjected to mechanical and thermal loads is carried out in this paper. The Green–Lagrange strain tensor in its entirety is used in the analysis. The locally effective material properties are evaluated using homogenization method which is based on the Mori–Tanaka scheme. In the case of thermally loaded plates, the temperature variation through the thickness is determined by solving a steady-state heat transfer (i.e. energy) equation. As an example, a functionally gradient material circular plate composed of zirconium and aluminum is used and results are presented in graphical form.

Self-Organisation of the Heat Resistant Steel Structure Following Dynamic Non-Equilibrium Processes

2015 ◽  
Vol 220-221 ◽  
pp. 917-921 ◽  
Author(s):  
Mykola Chausov ◽  
Pavlo Maruschak ◽  
Olegas Prentkovskis ◽  
Andriy Pylypenko ◽  
Valentyn Berezin ◽  
...  
Keyword(s):  
Dissipative Structure ◽  
Steel Structure ◽  
Image Correlation ◽  
Experimental Methodology ◽  
Resistant Steel ◽  
Heat Resistant Steel ◽  
Heat Resistant ◽  
Equilibrium Processes ◽  
Equilibrium Process ◽  
Non Equilibrium

Using an original experimental methodology and software for contactless investigation into strains applying the method of digital image correlation, conditions for DNP realization in the test setup with pre-set rigidity have been found. Strain velocities have been determined to be equal to 2...10 s–1 in the processes of forming and developing a dissipative structure of heat resistant steel under the DNP (dynamic non-equilibrium process).

scholarly journals White-light speckle image correlation applied to large-strain material characterization

2009 ◽  
pp. 377-392
Author(s):  
Giovanni B. Broggiato ◽  
Luca Cortese
Keyword(s):  
Material Characterization ◽  
Plastic Material ◽  
Large Strain ◽  
Equivalent Stress ◽  
Tensile Tests ◽  
Equivalent Strain ◽  
Image Correlation ◽  
Plastic Behavior ◽  
Full Field ◽  
Measurement Devices

In experimental mechanics, the possibility of tracking on component surfaces the full-field stress and strain states during deformation can be utilized for many purposes such as formability limits determination, quantification of stress intensification factors, material characterization and so on. Concerning the last topic, an interesting application could be a direct identification of the elasto-plastic material response up to large deformation. It is well known, in fact, that with traditional measurement devices it is possible to retrieve the true equivalent stress versus true equivalent strain data from tensile tests only up to the onset of necking, where localization starts to occur. This work aims to show how from the knowledge of a tensile test full-field strain and of load data it will be possible to obtain the full-stress field as well as the complete material elasto-plastic behavior.

Surrogate POD Models for Parametrized Sheet Metal Forming Applications

2013 ◽  
Vol 554-557 ◽  
pp. 919-927 ◽  
Author(s):  
Hamdaoui Mohamed ◽  
Guénhaël Le Quilliec ◽  
Piotr Breitkopf ◽  
Pierre Villon
Keyword(s):  
Finite Element ◽  
Sheet Metal ◽  
Sheet Metal Forming ◽  
Metal Forming ◽  
Optimization Problems ◽  
Strain Tensor ◽  
Forming Limit ◽  
Work Piece ◽  
Displacement Fields ◽  
Lagrange Strain

The aim of this work is to present a POD (Proper Orthogonal Decomposition) based surrogate approach for sheet metal forming parametrized applications. The final displacement field for the stamped work-piece computed using a finite element approach is approximated using the method of snapshots for POD mode determination and kriging for POD coefficients interpolation. An error analysis, performed using a validation set, shows that the accuracy of the surrogate POD model is excellent for the representation of finite element displacement fields. A possible use of the surrogate to assess the quality of the stamped sheet is considered. The Green-Lagrange strain tensor is derived and forming limit diagrams are computed on the fly for any point of the design space. Furthermore, the minimization of a cost function based on the surrogate POD model is performed showing its potential for solving optimization problems.

Input Data Determination for Large Strain Simulations

2015 ◽  
Vol 751 ◽  
pp. 124-130
Author(s):  
Jan Džugan ◽  
Martina Maresova ◽  
Jan Nachazel
Keyword(s):  
Numerical Simulations ◽  
Input Data ◽  
Large Strain ◽  
Fem Simulation ◽  
Material Behavior ◽  
Production Costs ◽  
Image Correlation ◽  
Compression Tests ◽  
Material Models ◽  
Strain Measurements

Numerical simulations are widely used for forming processes optimizations nowadays. They significantly contribute to improvement of forgings quality and production costs reduction. The crucial points of the numerical simulations are material input data and implemented material models. The paper is dealing with overview of methods for the input data measurement. There are discussed tests with various options of strain measurements as well as modifications of compression tests. Part of the paper is dealing with 3D strain measurements by Digital Image Correlation (DIC) enabling local strains measurements. DIC enables direct comparison of strains experimentally measured and strains obtained by numerical simulations, which is going to be presented. Finally, possibilities of complex material description considering plastic damage are presented. The last approach is the most accurate providing the most information on material behavior for FEM simulation, the procedure includes measurements on samples of various geometries with various stress strain conditions. Examples of sample sets for these measurements are shown here together with material models describing multiaxial plastic flow and damage.

Experimental Methodology Using Digital Image Correlation to Assess Ballistic Helmet Blunt Trauma

2011 ◽  
Vol 78 (5) ◽  
Author(s):  
Dixie M. Hisley ◽  
James C. Gurganus ◽  
Andrew W. Drysdale
Keyword(s):  
Digital Image Correlation ◽  
Blunt Trauma ◽  
Digital Image ◽  
Performance Test ◽  
Skull Fracture ◽  
Diffuse Axonal Injury ◽  
Image Correlation ◽  
Experimental Methodology ◽  
Available Energy ◽  
Deformation Velocity

As modern helmets have become quite capable of defeating the penetration capabilities of ballistic threats, Soldiers may experience head injuries due to blunt trauma caused by helmet back face deformation (BFD). Possible resulting injuries include skull fracture, hematoma, concussion, contusion, diffuse axonal injury, etc. Some of these injuries have been associated with traumatic brain injury. In order to assess potential injury mechanisms prior to fielding new helmets, we have developed a means to experimentally replicate and measure helmet BFD that can be correlated to injury criteria. In this study, helmet performance test methodology is developed using a digital image correlation (DIC) technique. DIC provides the capability to measure dynamic displacements, thereby providing the ability to calculate deformation, velocity, and acceleration rates. We have shown that digital image correlation is an experimentation technique that accurately captures BFD area and rate of deformation for impacts against combat helmets. We used the DIC data to calculate a new metric; the available energy that could potentially impact a Soldier’s head. Our study shows that DIC data upholds the hypothesis that helmet BFD mechanically loads the skull similar to a direct impact from a less-than-lethal projectile or blunt object impact. The available energy obtained from DIC measurements was used to calculate the blunt criterion (BC) for helmet standoff distances of 12.7 mm (0.5 in) and 19.1 mm (0.75 in), which in turn can provide a prediction of the probability of abbreviated injury scale (AIS) levels and, in particular, skull fracture. DIC can be used to provide dynamic helmet performance data that will allow increased understanding of BFD and quantitative assessment and validation of helmet performance results. Knowledge of the conditions leading to head trauma obtained through DIC experimentation should enable the selection of new energy-absorbing materials for helmets; thus, allowing new helmet design candidate performances to be objectively evaluated. Test data and characterization of helmet response could then be used to achieve improved warfighter survivability.

scholarly journals Sustained scleral stiffening in rats after a single genipin treatment

2019 ◽  
Vol 16 (159) ◽  
pp. 20190427 ◽  
Author(s):  
Bailey G. Hannon ◽  
Stephen A. Schwaner ◽  
Elizabeth M. Boazak ◽  
Brandon G. Gerberich ◽  
Erin J. Winger ◽  
...  
Keyword(s):  
Digital Image Correlation ◽  
Digital Image ◽  
Image Correlation ◽  
Brown Norway ◽  
Post Injection ◽  
Functional Studies ◽  
Multiple Treatments ◽  
Lagrange Strain ◽  
Norway Rats

Scleral stiffening has been proposed as a therapy for glaucoma and myopia. Previous in vivo studies have evaluated the efficacy of scleral stiffening after multiple treatments with a natural collagen crosslinker, genipin. However, multiple injections limit clinical translatability. Here, we examined whether scleral stiffening was maintained after four weeks following a single genipin treatment. Eyes from brown Norway rats were treated in vivo with a single 15 mM genipin retrobulbar injection, sham retrobulbar injection, or were left naive. Eyes were enucleated either 1 day or four weeks post-injection and underwent whole globe inflation testing. We assessed first principal Lagrange strain of the posterior sclera using digital image correlation as a proxy for scleral stiffness. Four weeks post-injection, genipin treatment resulted in a 58% reduction in scleral strain as compared to controls ( p = 0.005). We conclude that a single in vivo injection of genipin effectively stiffened rat sclera for at least four weeks which motivates further functional studies and possible clinical translation of genipin-induced scleral stiffening.

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