An X-FEM investigation of deflection/penetration of hydro-fractures at material discontinuities

2019 ◽  
pp. 604-610
Author(s):  
M. Vahab ◽  
Sh. Akhondzadeh ◽  
A. R. Khoei ◽  
N. Khalili
2018 ◽  
Vol 9 (6) ◽  
pp. 779-792 ◽  
Author(s):  
Katarzyna Majewska ◽  
Magdalena Mieloszyk ◽  
Wieslaw Ostachowicz

Purpose The purpose of this paper is to study if it is possible applying infrared thermography (both vibro and pulsed) to detect and localise material discontinuities as well as to find the place where the inclusion was introduced. Design/methodology/approach The experimental investigation is performed on samples manufactured during infusion process. The measurements were performed on three four-layered rectangular composite samples with discontinuities. The discontinuities introduced in the samples were as follow: all three samples between first and second layer counting form the bottom two optical fibres (OFs) were embedded and additionally: sample no. 1 – one of the OF was broken, sample no. 2 – the drop of water was introduced, and sample no. 3 – the little amount of dust was introduced. Findings For some discontinuities, the vibrothermography is excellent tool (placement of broken OF, drop of water), for same is not sufficient (healthy OFs or dust). For dust, the pulsed thermography seems to be the required tool. Different approaches (vibrothermography and pulsed thermography) for the same sample will confirm that for same defects vibrothermograpy is better and for some pulsed thermography – complex combination of different thermography approaches is needed to have complex response about sample structural condition. Originality/value The presented paper is an original research work. There are very limited literature papers applying both vibro and pulsed thermography for one problem. The assessment of different discontinuities (inclusions) and detailed analysis is presented.


2011 ◽  
Vol 133 (3) ◽  
Author(s):  
Haofeng Chen ◽  
Weihang Chen ◽  
Tianbai Li ◽  
James Ure

In this study, both the lower and upper bound shakedown limits of a closed-end composite cylinder with or without a cross-hole subject to constant internal pressure and a cyclic thermal gradient are calculated by the linear matching method. Convergence for the upper and lower bound shakedown limits of the composite cylinders is sought and shakedown limit interaction diagrams of the numerical applications identifying the regions of reverse plasticity limit and ratchet limit are presented. The effects of temperature-dependent yield stress, material discontinuities, composite cylinder thickness, and the existence of the cross-hole on the shakedown limits are discussed for different geometry parameters. Finally, a safety shakedown envelope is created by formulating the shakedown limit results of different composite materials and cylinder thickness ratios with different cross-hole sizes.


Author(s):  
Chetan P. Nikhare

Abstract Origami concept came up as an emerging technique for sheet metal bending or folding and is called as Origami-based sheet metal (OSM) folding. This process fits right in criteria of effectiveness, efficiency, and sustainable manufacturing due to minimal resources required to make the fold or bend. In this process, the line was created on which the bend was supposed to perform. Traditionally the intermittent material was removed from that line with a through cut. Then the bend was performed. During bending the force required was very less and thus it can also be called as easy bend operation. Because the material and removed all the way through the thickness of the metal, these part after bending cannot be used to contain particles smaller than the cut width or liquid solution due to leakage issue. To overcome this issue, this paper investigates the material discontinuities with a blind cut, where the material through the thickness was not completely removed. For this 4 sample types were created. Three additional variables were added in placing the sample during bend operation. Experiments were performed and bending deformation and springback were analyzed. After analyzing the results, it was found that significant thickness difference regions in the sample, smaller clearance, smaller width or cut, and width of cut facing punch are the best variable to have a better bending and less springback.


1998 ◽  
Vol 120 (4) ◽  
pp. 336-341 ◽  
Author(s):  
E. Madenci ◽  
S. Shkarayev ◽  
R. Mahajan

In this study, the effect of underfill on the level of stress concentrations is investigated and possible failure sites are identified by using a global/local finite element approach. The global elements capture the exact singular behavior of the stresses near the geometric and material discontinuities. Application of the strain energy density criterion indicates the possible failure sites and how they shift due to the presence of underfill.


1991 ◽  
Vol 246 ◽  
Author(s):  
Lev Truskinovsky

AbstractLocalized phase transitions, as well as shock waves, can be modeled by material discontinuities satisfying appropriate jump conditions. One can show that the classical system of Rankine-Hugoniot jump conditions is incomplete in the case of subsonic phase boundaries. The supplementary condition which generalizes the condition of phase equilibrium, can be obtained from the traveling wave solution of the truly dynamic system of equations describing the interface structure.


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