Investigation of Finite Deformations and Shear Banding: Theory and Experiment

1991 ◽  
Vol 44 (11S) ◽  
pp. S20-S26
Author(s):  
A. E. Bayoumi ◽  
R. B. Joshi ◽  
H. M. Zbib
Keyword(s):  
Plastic Flow ◽  
Shear Banding ◽  
Shear Bands ◽  
Processing Technique ◽  
Material Behavior ◽  
Image Processing Technique ◽  
Deformation Pattern ◽  
Anisotropy Ratio ◽  
Small Magnitude ◽  
Flow Anisotropy

An experimental method using a digital image processing technique is developed for the purpose of characterizing material behavior at large elastoplastic deformations and the associated phenomenon of localization of plastic flow into shear bands. This allows for a detailed description of the evolution of the nonuniform deformation pattern in the post-localization regime. The experimental results are utilized to calibrate a recently developed gradient-dependent constitutive equation which takes into account the effect of heterogeneous plastic flow, anisotropy and large deformations. The measured values of the gradient coefficients are of small magnitude suggesting that higher order gradients are important only in the highly inhomogeneous region as expected. Moreover, it is found that anisotropic effects become significant in the post-localization regime where the anisotropy ratio changes considerably.

The Realities of Friction in Metal Plastic Flow With Corresponding Results During Metal Cutting

2019 ◽  
Author(s):  
Wolfgang Lortz ◽  
Radu Pavel
Keyword(s):  
Internal Friction ◽  
Strain Rate ◽  
Plastic Flow ◽  
Cross Sections ◽  
Chip Formation ◽  
Metal Cutting ◽  
Material Behavior ◽  
Deformation Pattern ◽  
Low Velocity ◽  
As Stress

Abstract Metal cutting is a dynamic process with two types of friction: on the one hand, external friction between two different bodies, and on the other hand, an internal friction inside the same material, due to plastic flow. These two different types of friction lead to different chip formation processes. In the case of built-up-edge (BUE), low velocity creates low energy, resulting in a self-hardening effect with BUE. With increasing velocity, the energy will increase and will result in high temperatures with a built-up-layer (BUL). Furthermore, under special circumstances, friction will lead to a self-blockade (a self-blocking state). This situation describes the third stage in metal plastic flow — the creation of a segmental chip. In this case the internal friction takes over. One question arises: “How can we determine these two types of different friction?” For solving these phenomena new fundamental equations based on mathematics, physics and material behavior have to be developed. This paper presents newly developed equations, which deliver the theoretical distribution of yield shear stress as well as strain rate with corresponding grid deformation pattern in metal plastic flow. For an actual cut, the plastic deformation pattern remains when the process is stopped, and therefore the theoretical result can be compared with cross-sections of the relevant chip formation areas — contrary to outputs such as stress, strain rate and temperatures which are all functions of position and time. All this will be shown and discussed in the paper, and stands in good agreement with experimental results.

Plastic flow in dynamic compression of a Zr-based bulk metallic glass

2006 ◽  
Vol 21 (6) ◽  
pp. 1570-1575 ◽  
Author(s):  
W.H. Jiang ◽  
F.X. Liu ◽  
D.C. Qiao ◽  
H. Choo ◽  
P.K. Liaw
Keyword(s):  
Metallic Glass ◽  
Bulk Metallic Glass ◽  
Free Volume ◽  
Plastic Flow ◽  
Dynamic Compression ◽  
Maximum Shear Stress ◽  
Shear Banding ◽  
Shear Bands ◽  
Free Volume Model ◽  
Geometrically Constrained

Using geometrically constrained specimens, the plastic flow behaviors of the as-cast and the relaxed Zr52.5Cu17.9Ni14.6Al10.0Ti5.0 bulk metallic glass in the dynamic compression were investigated. Both alloys exhibit a significant plasticity in the dynamic compression. The plastic deformation in both alloys is still inhomogeneous, which is characterized by the serrated plastic flow and the formation of shear bands. Free volumes affect the shear banding and the plastic flow. The reduced free volume results in the deviation of the shear banding direction from the maximum shear stress. The relaxed alloy exhibits the obvious stress overshoot, which is consistent with the theoretical prediction using a free volume model.

scholarly journals Viscous Shear Banding in Cutting of Metals

2018 ◽  
Vol 140 (11) ◽  
Author(s):  
Dinakar Sagapuram ◽  
Koushik Viswanathan
Keyword(s):  
Plastic Flow ◽  
Flow Instability ◽  
Liquid Metals ◽  
Shear Banding ◽  
Shear Bands ◽  
Local Deformation ◽  
Flow Rule ◽  
Sliding Mechanism ◽  
Viscous Shear ◽  
Local Shear

Shear banding is a type of plastic flow instability with often adverse implications for cutting and deformation processing of metals. Here, we study the mechanics of plastic flow evolution within single shear bands in Ti- and Ni-based alloy systems. The local shear band displacement profiles are quantitatively mapped at high resolution using a special micromarker technique. The results show that shear bands, once nucleated, evolve by a universal viscous sliding mechanism that is independent of microstructural details. The evolution of local deformation around the band is accurately captured by a momentum diffusion equation based on a Bingham-type flow rule. The predicted band viscosity is very small, compared to those of liquid metals. A plausible explanation for this small viscosity and fluid-like behavior at the band, based on phonon drag, is presented.

Viscous Shear Banding in Cutting of Metals

2018 ◽  
Author(s):  
Dinakar Sagapuram ◽  
Koushik Viswanathan
Keyword(s):  
Plastic Flow ◽  
Flow Instability ◽  
Liquid Metals ◽  
Shear Banding ◽  
Shear Bands ◽  
Local Deformation ◽  
Bingham Flow ◽  
Sliding Mechanism ◽  
Viscous Shear ◽  
Local Shear

Shear banding is a type of plastic flow instability with often adverse implications for cutting and deformation processing of metals. Here, we study the mechanics of plastic flow evolution within single shear bands in two different (Ti and Ni-based) alloy systems. The local shear band displacement profiles are quantitatively mapped at high resolution using a special micro-marker technique. The results show that shear bands, once nucleated, evolve by a universal viscous sliding mechanism that is independent of microstructural details. The evolution of local deformation around the band is accurately captured using a simple momentum diffusion model by assuming Bingham flow rheology for the band material. The predicted band viscosity is very small, comparable to those of liquid metals. A plausible explanation for this small viscosity and fluid-like behavior at the band, based on phonon drag, is presented.

A New Image Processing Technique for STEM

1974 ◽  
Vol 32 ◽  
pp. 432-433
Author(s):  
Yasushi Kokubo ◽  
Hirotami Koike ◽  
Teruo Someya
Keyword(s):  
Electron Microscopy ◽  
Image Processing ◽  
Scanning Electron Microscopy ◽  
Elastic Scattering ◽  
Field Emission ◽  
Processing Technique ◽  
Image Processing Technique ◽  
Energy Analyzer ◽  
Scanning Microscope ◽  
Scanning Electron

One of the advantages of scanning electron microscopy is the capability for processing the image contrast, i.e., the image processing technique. Crewe et al were the first to apply this technique to a field emission scanning microscope and show images of individual atoms. They obtained a contrast which depended exclusively on the atomic numbers of specimen elements (Zcontrast), by displaying the images treated with the intensity ratio of elastically scattered to inelastically scattered electrons. The elastic scattering electrons were extracted by a solid detector and inelastic scattering electrons by an energy analyzer. We noted, however, that there is a possibility of the same contrast being obtained only by using an annular-type solid detector consisting of multiple concentric detector elements.

A Comparative Study of Ant and Genetic Algorithms in Digital Mammography

2018 ◽  
pp. 194-200
Author(s):  
J. Magelin Mary ◽  
Chitra K. ◽  
Y. Arockia Suganthi
Keyword(s):  
Genetic Algorithm ◽  
Image Processing ◽  
Medical Image ◽  
Medical Image Processing ◽  
Processing Technique ◽  
Input Image ◽  
Image Processing Technique ◽  
Computational Time ◽  
Image Mining ◽  
The Individual

Image processing technique in general, involves the application of signal processing on the input image for isolating the individual color plane of an image. It plays an important role in the image analysis and computer version. This paper compares the efficiency of two approaches in the area of finding breast cancer in medical image processing. The fundamental target is to apply an image mining in the area of medical image handling utilizing grouping guideline created by genetic algorithm. The parameter using extracted border, the border pixels are considered as population strings to genetic algorithm and Ant Colony Optimization, to find out the optimum value from the border pixels. We likewise look at cost of ACO and GA also, endeavors to discover which one gives the better solution to identify an affected area in medical image based on computational time.

An Enhanced Technique for Classification of Fruits using Shape Color and Texture Features

2017 ◽  
Vol 7 (7) ◽  
pp. 408
Author(s):  
Yashpal Jitarwal ◽  
Tabrej Ahamad Khan ◽  
Pawan Mangal
Keyword(s):  
Image Processing ◽  
Texture Features ◽  
Automatic Classification ◽  
Processing Technique ◽  
Image Processing Technique ◽  
Advance Technique ◽  
Time Required ◽  
Fruit Sorting ◽  
Human Inspection

In earlier times fruits were sorted manually and it was very time consuming and laborious task. Human sorted the fruits of the basis of shape, size and color. Time taken by human to sort the fruits is very large therefore to reduce the time and to increase the accuracy, an automatic classification of fruits comes into existence.To improve this human inspection and reduce time required for fruit sorting an advance technique is developed that accepts information about fruits from their images, and is called as Image Processing Technique.

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