Determination of the Macroscopic Plastic Yield Behaviour of Microcracked Materials

2010 ◽  
pp. 789-796
Author(s):  
V. Monchiet ◽  
E. Charkaluk ◽  
D. Kondo
Keyword(s):  
Plastic Yield ◽  
Yield Behaviour

Determination of Poisson’s Ratio by Spherical Indentation Using Neural Networks—Part I: Theory

2000 ◽  
Vol 68 (2) ◽  
pp. 218-223 ◽  
Author(s):  
N. Huber ◽  
A. Konstantinidis ◽  
Ch. Tsakmakis
Keyword(s):  
Poisson Ratio ◽  
Indentation Test ◽  
Inverse Function ◽  
Elastic Half Space ◽  
Spherical Indentation ◽  
Isotropic Hardening ◽  
Plastic Yield ◽  
Load Response ◽  
Reduced Modulus

When studying analytically the penetration of an indenter of revolution into an elastic half-space use is commonly made of the fraction Er=E/1−ν2. Because of this, only Er is determined from the indentation test, while the value of ν is usually assumed. However, as shown in the paper, if plastic deformation is involved during loading, the depth-load trajectory depends on the reduced modulus and, additionally, on the Poisson ratio explicitly. The aim of the paper is to show, with reference to a simple plasticity model exhibiting linear isotropic hardening, that the Poisson ratio can be determined uniquely from spherical indentation if the onset of plastic yield is known. To this end, a loading and at least two unloadings in the plastic regime have to be considered. Using finite element simulations, the relation between the material parameters and the quantities characterizing the depth-load response is calculated pointwise. An approximate inverse function represented by a neural network is derived on the basis of these data.

Determination of Poisson’s Ratio by Spherical Indentation Using Neural Networks—Part II: Identification Method

2000 ◽  
Vol 68 (2) ◽  
pp. 224-229 ◽  
Author(s):  
N. Huber ◽  
Ch. Tsakmakis
Keyword(s):  
Neural Networks ◽  
Poisson’S Ratio ◽  
Inverse Function ◽  
Poisson's Ratio ◽  
Spherical Indentation ◽  
Plastic Yield ◽  
Different Depths ◽  
Unloading Stiffness ◽  
First Time

In a previous paper it has been shown that the load and the unloading stiffness are, among others, explicit functions of the Poisson’s ratio, if a spherical indenter is pressed into a metal material. These functions can be inverted by using neural networks in order to determine the Poisson’s ratio as a function of the load and the unloading stiffness measured at different depths. Also, the inverse function possesses as an argument the ratio of the penetration depth and that depth, at which plastic yield occurs for the first time. The latter quantity cannot be measured easily. In the present paper some neural networks are developed in order to identify the value of Poisson’s ratio. After preparing the input data appropriately, two neural networks are trained, the first one being related to Set 2 of the previous paper. In order to avoid an explicit measurement of the yield depth, the second neural network has to be trained in such a way, that its solution intersects with that of Set 2 at the correct value of Poisson’s ratio. This allows to identify Poisson’s ratio with high accuracy within the domain of finite element data.

Plastic Yield Behaviour of Porous Metals

1992 ◽  
Vol 35 (4) ◽  
pp. 275-280 ◽  
Author(s):  
D. N. Lee ◽  
H. S. Kim
Keyword(s):  
Porous Metals ◽  
Plastic Yield ◽  
Yield Behaviour

The plastic yield behaviour of polymethylmethacrylate

1968 ◽  
Vol 3 (2) ◽  
pp. 183-190 ◽  
Author(s):  
P. B. Bowden ◽  
J. A. Jukes
Keyword(s):  
Plastic Yield ◽  
Yield Behaviour

Determination of plastic yield stress from spherical indentation slope curve

2008 ◽  
Vol 62 (15) ◽  
pp. 2260-2262 ◽  
Author(s):  
Wenyi Yan ◽  
Qingping Sun ◽  
Peter D. Hodgson
Keyword(s):  
Yield Stress ◽  
Spherical Indentation ◽  
Plastic Yield

Galactic orbits of stars

1966 ◽  
Vol 25 ◽  
pp. 93-97
Author(s):  
Richard Woolley
Keyword(s):  
Globular Cluster ◽  
Potential Field ◽  
High Velocity ◽  
Velocity Vector ◽  
Variable Stars ◽  
The Sun ◽  
Proper Motions ◽  
Rr Lyrae ◽  
The Galaxy

It is now possible to determine proper motions of high-velocity objects in such a way as to obtain with some accuracy the velocity vector relevant to the Sun. If a potential field of the Galaxy is assumed, one can compute an actual orbit. A determination of the velocity of the globular clusterωCentauri has recently been completed at Greenwich, and it is found that the orbit is strongly retrograde in the Galaxy. Similar calculations may be made, though with less certainty, in the case of RR Lyrae variable stars.

Distance to SN 1987A and the LMC

1999 ◽  
Vol 190 ◽  
pp. 549-554
Author(s):  
Nino Panagia
Keyword(s):  
Angular Size ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Light Curves ◽  
Distance Modulus ◽  
Absolute Size ◽  
Sn 1987A

Using the new reductions of the IUE light curves by Sonneborn et al. (1997) and an extensive set of HST images of SN 1987A we have repeated and improved Panagia et al. (1991) analysis to obtain a better determination of the distance to the supernova. In this way we have derived an absolute size of the ringRabs= (6.23 ± 0.08) x 1017cm and an angular sizeR″ = 808 ± 17 mas, which give a distance to the supernovad(SN1987A) = 51.4 ± 1.2 kpc and a distance modulusm–M(SN1987A) = 18.55 ± 0.05. Allowing for a displacement of SN 1987A position relative to the LMC center, the distance to the barycenter of the Large Magellanic Cloud is also estimated to bed(LMC) = 52.0±1.3 kpc, which corresponds to a distance modulus ofm–M(LMC) = 18.58±0.05.

International determination of the total motion of the pole

1961 ◽  
Vol 13 ◽  
pp. 29-41
Author(s):  
Wm. Markowitz
Keyword(s):  
Secular Motion ◽  
The Future

A symposium on the future of the International Latitude Service (I. L. S.) is to be held in Helsinki in July 1960. My report for the symposium consists of two parts. Part I, denoded (Mk I) was published [1] earlier in 1960 under the title “Latitude and Longitude, and the Secular Motion of the Pole”. Part II is the present paper, denoded (Mk II).

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