Computation of stresses and deformations for a two-dimensional sliding contact between an elastic layer and a rigid indenter with a rounded profile

2003 ◽  
Vol 38 (2) ◽  
pp. 161-168 ◽  
Author(s):  
M. J Jaffar
Keyword(s):  
Thin Layer ◽  
Layer Thickness ◽  
Contact Pressure ◽  
Elastic Layer ◽  
Sliding Contact ◽  
Rigid Foundation ◽  
Two Dimensional ◽  
Flat Punch ◽  
Contact Width ◽  
Indentation Problem

The two-dimensional indentation problem of an elastic layer by either a wedge with a rounded tip or a flat punch with rounded corners in the presence of friction is investigated numerically. Contact stresses and deformations are presented when the layer is either bonded or resting without friction on a rigid foundation. Moreover, a set of asymptotic solutions for the contact pressure is obtained for an unbonded thin layer (the contact width is significantly larger than the layer thickness). The effects of several parameters on the results are examined.

Adhesive Contact of Flat-Ended Wedges: Theory and Computer Experiments

1999 ◽  
Vol 121 (1) ◽  
pp. 128-132 ◽  
Author(s):  
Leng Yongsheng ◽  
Hu Yuanzhong ◽  
Zheng Linqing
Keyword(s):  
Contact Pressure ◽  
Brownian Dynamics ◽  
Computer Experiments ◽  
Adhesive Contact ◽  
Dynamical Theory ◽  
Elastic Half Space ◽  
Finite Width ◽  
Flat Punch ◽  
Closed Form Solutions ◽  
Contact Width

We give the closed-form solutions for the two-dimensional adhesive contact of a flat-ended wedge with an elastic half-space, including contact pressure distribution and load-contact width relationship. The approach is derived from contact mechanics in plane-strain elasticity and fracture mechanics concepts. The contact pressure has stress singularities both at the edges of contact due to molecular attractive forces and at the wedge corners, and is compared with those without adhesion. Under zero load, we find the contact strip has a finite width which is greater than that of the wedge end, and the central region of contact is under compression, similar to that of a flat punch problem, while the regions near the contact edges are under tension. Unlike the usual experiments with smooth and low modulus materials, we conduct molecular dynamics (MD) experiments via embedded-atom method (EAM), brownian dynamics algorithm and dynamical theory of crystal lattices. The results, including the “pull-off” force for contacting surfaces to peel apart, conform reasonably well with those derived from a continuum model.

Stresses and Deformations in Elastic Layers Indented by a Conical Punch

1995 ◽  
Vol 209 (3) ◽  
pp. 201-205 ◽  
Author(s):  
M J Jaffar
Keyword(s):  
Layer Thickness ◽  
Elastic Layer ◽  
Present Method ◽  
Numerical Solutions ◽  
Surface Deformation ◽  
Gibbs Phenomenon ◽  
Contact Radius ◽  
Rigid Foundation ◽  
Triangular Form ◽  
Elastic Layers

The numerical solutions to problems of the contact between an elastic layer in complete adhesion with a rigid foundation (bonded layer) or resting without friction on a rigid foundation (unbonded layer) and a frictionless rigid cone (conical punch) are presented. The present numerical scheme is a modification of that developed by the author for a smooth indenter profile. The modified analysis uses the Fejér method in order to eliminate completely the Gibbs phenomenon at the neighbourhood of the singularity. Calculations are performed to examine the effects of the layer thickness and/or the layer compressibility on the results. It was found that as the layer thickness was decreased then the contact pressure approaches a triangular form for unbonded layer and bonded layer with Poisson's ratio v < 0.5; for an incompressible layered surface (v = 0.5) the pressure gradient tends to zero at the contact ends. Moreover, the contact radius and the surface deformation depend not only on the layer thickness but are also influenced by the layer compressibility. The present method showed excellent agreement with the existing solutions when the layer becomes either a half-space or thin.

Friction Effects on the Edge-of-Contact Stresses for Sliding Contact Between a Flat Punch With Rounded Corners and a Half Space

2017 ◽  
Vol 84 (12) ◽  
Author(s):  
G. B. Sinclair
Keyword(s):  
Closed Form ◽  
Half Space ◽  
Contact Pressure ◽  
Contact Stresses ◽  
Sliding Contact ◽  
Flat Punch ◽  
Title Problem

For the title problem, the punch is assumed to be pressed vertically into the horizontal upper surface of the half space, then slide horizontally sideways. A range of such configurations is identified that permit Shtaerman’s solution for the contact pressure for a rigid frictionless punch to be modified so that it applies to a deformable punch and also yields the contact stresses when the punch slides in the presence of friction. Closed-form expressions are obtained for the peak edge-of-contact stresses. These edge-of-contact stresses can fluctuate significantly with even modest amounts of sliding.

scholarly journals Investigation of the Heteroepitaxial Process Optimization of Ge Layers on Si (001) by RPCVD

Nanomaterials ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 928
Author(s):  
Yong Du ◽  
Zhenzhen Kong ◽  
Muhammet Toprak ◽  
Guilei Wang ◽  
Yuanhao Miao ◽  
...  
Keyword(s):  
High Temperature ◽  
Buffer Layer ◽  
Layer Thickness ◽  
Growth Temperature ◽  
Crystalline Quality ◽  
Initial Growth ◽  
Two Dimensional ◽  
High Quality ◽  
Reduced Pressure

This work presents the growth of high-quality Ge epilayers on Si (001) substrates using a reduced pressure chemical vapor deposition (RPCVD) chamber. Based on the initial nucleation, a low temperature high temperature (LT-HT) two-step approach, we systematically investigate the nucleation time and surface topography, influence of a LT-Ge buffer layer thickness, a HT-Ge growth temperature, layer thickness, and high temperature thermal treatment on the morphological and crystalline quality of the Ge epilayers. It is also a unique study in the initial growth of Ge epitaxy; the start point of the experiments includes Stranski–Krastanov mode in which the Ge wet layer is initially formed and later the growth is developed to form nuclides. Afterwards, a two-dimensional Ge layer is formed from the coalescing of the nuclides. The evolution of the strain from the beginning stage of the growth up to the full Ge layer has been investigated. Material characterization results show that Ge epilayer with 400 nm LT-Ge buffer layer features at least the root mean square (RMS) value and it’s threading dislocation density (TDD) decreases by a factor of 2. In view of the 400 nm LT-Ge buffer layer, the 1000 nm Ge epilayer with HT-Ge growth temperature of 650 °C showed the best material quality, which is conducive to the merging of the crystals into a connected structure eventually forming a continuous and two-dimensional film. After increasing the thickness of Ge layer from 900 nm to 2000 nm, Ge surface roughness decreased first and then increased slowly (the RMS value for 1400 nm Ge layer was 0.81 nm). Finally, a high-temperature annealing process was carried out and high-quality Ge layer was obtained (TDD=2.78 × 107 cm−2). In addition, room temperature strong photoluminescence (PL) peak intensity and narrow full width at half maximum (11 meV) spectra further confirm the high crystalline quality of the Ge layer manufactured by this optimized process. This work highlights the inducing, increasing, and relaxing of the strain in the Ge buffer and the signature of the defect formation.

scholarly journals Studies on the autophosphorylation of the insulin receptor from human placenta. Analysis of the sites phosphorylated by two-dimensional peptide mapping

1988 ◽  
Vol 252 (2) ◽  
pp. 607-615 ◽  
Author(s):  
J M Tavaré ◽  
R M Denton
Keyword(s):  
Thin Layer ◽  
Insulin Receptor ◽  
Peptide Mapping ◽  
Beta Subunit ◽  
Two Dimensional ◽  
Intact Cells ◽  
Tyrosine Residues ◽  
Domain 3 ◽  
Receptor Beta

1. A partially purified preparation of human placental insulin receptors was incubated with [gamma-32P]ATP in the presence or absence of insulin. The 32P-labelled insulin-receptor beta-subunits were then isolated, cleaved with trypsin followed by protease V8 and the [32P]phosphopeptides generated were analysed by thin layer electrophoresis and chromatography. This approach revealed that insulin stimulates autophosphorylation of the insulin-receptor beta-subunit in vitro on at least seven tyrosine residues distributed among three distinct domains. 2. One domain (domain 2), containing tyrosine residues 1146, 1150 and 1151 was the most rapidly phosphorylated and could be recovered as mono-, di- and triphosphorylated peptides cleaved by trypsin at Arg-1143 and either Lys-1153 or Lys-1156. Multiple phosphorylation of this domain appears to partially inhibit the cleavage at Lys-1153 by trypsin. 3. In a second domain (domain 3) containing two phosphorylated tyrosine residues at positions 1316 and 1322 the tyrosines were phosphorylated more slowly than those in domain 2. This domain is close to the C-terminus of the beta-subunit polypeptide chain. 4. At least two further tyrosine residues appeared to be phosphorylated after those in domains 2 and 3. These residues probably residue within a domain lying in close proximity to the inner face of the plasma membrane containing tyrosines 953, 960 and 972, but conclusive evidence is still required. 5. The two-dimensional thin-layer analysis employed in this study to investigate insulin-receptor phosphorylation has several advantages over previous methods based on reverse-phase chromatography. It allows greater resolution of 32P-labelled tryptic peptides and, when coupled to radioautography, is considerably more sensitive. The approach can be readily adapted to study phosphorylation of the insulin receptor within intact cells.

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