Effect of Surface Asperity on Interfacial Contact Process Controlled by Power Law Creep—Numerical Study of Viscoplastic Adhering Process

1995 ◽  
Vol 117 (3) ◽  
pp. 330-335 ◽  
Author(s):  
Y. Takahashi ◽  
M. Tanimoto
Keyword(s):  
Power Law ◽  
Numerical Study ◽  
Contact Process ◽  
Equivalent Strain ◽  
Type I ◽  
Intimate Contact ◽  
Interfacial Contact ◽  
Bond Interface ◽  
Power Law Creep ◽  
Element Technique

An interfacial contact process due to power law creep is studied using a finite element technique. The contact process is assumed to be produced by power law creep alone after initial intimate contact by instantaneous plastic deformation, i.e., no diffusional mechanisms for void shrinkage are taken into account. Also, the surface oxide film is not considered. If the bonded material is deformed, then the deformation is influenced by the initial faying surface wauiness with the asperity angle αo, and the contact process is achieved by two modes; surface folding at the bond-interface (type I) and interfacial expansion (type II), where the surface folding is the phenomenon that two faying surfaces are overlapped to each other. The surface folding phenomenon occurs preferentially when αo is less than 30 deg (as the surface wauiness height decreases). On the other hand, the interfacial expansion is dominant at αo > 45 deg. This can be explained in terms of the distribution of equivalent strain (stress) in the vicinity of the bond-interface.

Experimental Study of Interfacial Contacting Process Controlled by Power Law Creep

1995 ◽  
Vol 117 (3) ◽  
pp. 336-340 ◽  
Author(s):  
Y. Takahashi ◽  
M. Tanimoto
Keyword(s):  
Power Law ◽  
Contact Process ◽  
High Vacuum ◽  
Deformation Mode ◽  
Experimental Results ◽  
Void Coalescence ◽  
Bonding Pressure ◽  
Interfacial Contact ◽  
Asperity Angle ◽  
Power Law Creep

Interfacial contacting processes under a high temperature and a high bonding pressure (T = 973 K, P = 30 MPa) are experimentally studied, using oxygen free copper. The faying surfaces were machined by lathe, resulting in controlled regular surface asperities. The asperity angle of surface ridges was changed from 10 to 60 deg. The change in the interfacial deformation mode with the asperity angle has been investigated. Results show the interfacial contact process is strongly influenced by the asperity angle (shape of surface ridge). The bonding tests were carried out in high vacuum atmosphere (10−4 Pa) so that the surface oxide film need not be considered. Experimental results are in good agreement with the results calculated by a finite element model, in which the interfacial contact is assumed to be produced by power law creep alone. It was thus suggested that void coalescence is governed by power law creep under the present test conditions (T = 973 K and P = 30 MPa) except for the final stage of bonding. Experimental results also suggest that the elementary rate process of interfacial contact due to power law creep is classified into two types; surface folding and interfacial expansion. Here, the surface folding is the phenomenon that two faying surfaces are overlapped to each other and the interfacial expansion means that the bonded interface area is extended along the bond-interface.

Effect of Bulk Deformation on Viscoplastic Adhering Process—A Numerical Study of Solid State Pressure Welding

1993 ◽  
Vol 115 (2) ◽  
pp. 171-178 ◽  
Author(s):  
Y. Takahashi ◽  
T. Koguchi ◽  
K. Nishiguchi
Keyword(s):  
Solid State ◽  
Strain Rate ◽  
Numerical Study ◽  
Contact Process ◽  
Element Model ◽  
Equivalent Strain ◽  
Bulk Deformation ◽  
Intimate Contact ◽  
Rate Determining Step ◽  
Asperity Angle

Viscoplastic intimate contact process of uneven surfaces is numerically studied by using the finite element model proposed in our previous paper. The model treats only the case that the interfacial contact is the rate determining step of the solid state bonding process. The distribution of the equivalent strain rate around the void surface is strongly influenced by the bulk constraint conditions, i.e., the interfacial deformation is greatly affected by the bulk deformation. The strain rate at the void tip is strikingly increased by the bulk deformation, which accelerates the void shrinkage on the bond interface. If the bulk is deformed, the contacting process is also affected by the asperity angle α0 due to surface waviness. When α0 < 30 deg, the bonded area growth is mainly produced by the folding phenomena of the faying surfaces.

scholarly journals Three Regions in the Power-Law Creep Regime of TiAl

1992 ◽  
Vol 33 (12) ◽  
pp. 1182-1184 ◽  
Author(s):  
Yukio Ishikawa ◽  
Kouichi Maruyama ◽  
Hiroshi Oikawa
Keyword(s):  
Power Law ◽  
Power Law Creep ◽  
Creep Regime

scholarly journals Free Convective MHD Flow Past a Vertical Cone with Variable Heat and Mass Flux

2013 ◽  
Vol 2013 ◽  
pp. 1-8 ◽  
Author(s):  
J. Prakash ◽  
S. Gouse Mohiddin ◽  
S. Vijaya Kumar Varma
Keyword(s):  
Boundary Layer ◽  
Power Law ◽  
Mass Flux ◽  
Numerical Study ◽  
Convection Boundary Layer ◽  
Vertical Cone ◽  
Local Skin ◽  
Surface Mass ◽  
Flow Past ◽  
Power Law Exponent

A numerical study of buoyancy-driven unsteady natural convection boundary layer flow past a vertical cone embedded in a non-Darcian isotropic porous regime with transverse magnetic field applied normal to the surface is considered. The heat and mass flux at the surface of the cone is modeled as a power law according to qwx=xm and qw*(x)=xm, respectively, where x denotes the coordinate along the slant face of the cone. Both Darcian drag and Forchheimer quadratic porous impedance are incorporated into the two-dimensional viscous flow model. The transient boundary layer equations are then nondimensionalized and solved by the Crank-Nicolson implicit difference method. The velocity, temperature, and concentration fields have been studied for the effect of Grashof number, Darcy number, Forchheimer number, Prandtl number, surface heat flux power-law exponent (m), surface mass flux power-law exponent (n), Schmidt number, buoyancy ratio parameter, and semivertical angle of the cone. Present results for selected variables for the purely fluid regime are compared with the published results and are found to be in excellent agreement. The local skin friction, Nusselt number, and Sherwood number are also analyzed graphically. The study finds important applications in geophysical heat transfer, industrial manufacturing processes, and hybrid solar energy systems.

A simple FE approach to study microstructural influences in power-law creep

2012 ◽  
Vol 52 (1) ◽  
pp. 73-76 ◽  
Author(s):  
Cornelia Pein ◽  
Christof Sommitsch
Keyword(s):  
Power Law ◽  
Power Law Creep

scholarly journals Rapid mantle flow with power-law creep explains deformation after the 2011 Tohoku mega-quake

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Ryoichiro Agata ◽  
Sylvain D. Barbot ◽  
Kohei Fujita ◽  
Mamoru Hyodo ◽  
Takeshi Iinuma ◽  
...  
Keyword(s):  
Power Law ◽  
Mantle Flow ◽  
Power Law Creep
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