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Interface Damage (interface + damage)

Distribution by Scientific Domains

Engineering	75%

Selected Abstracts

A simplified analysis of interface failure under compressive normal stress and monotonic or cyclic shear loading

INTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 4 2005
Zenon Mróz
Abstract Interface damage and delamination is usually accompanied by frictional slip at contacting interfaces under compressive normal stress. The present work is concerned with an analysis of progressive interface failure using the cohesive crack model with the critical stress softening and frictional traction present at the contact. Both monotonic and cyclic loadings are considered for anti-plane shear of an elastic plate bonded to a rigid substrate by means of cohesive interface. An analytical solution can be obtained by neglecting the effect of minor shear stress component. The analysis of progressive delamination process revealed three solution types, namely: short, medium and long plate solutions. The long plate solution was obtained under an assumption of quasistatic progressive growth of the delamination zone. In view of snap back response, the quasistatic deformation process cannot be executed by either traction or displacement control. The states of frictional slip accompanied by shake down or incremental failure are distinguished in the case of cyclic loading, related to load amplitude and structural dimensions. The analysis provides a reference solution for numerical treatment of more complex cases. Copyright © 2005 John Wiley & Sons, Ltd. [source]

Combining interface damage and friction in a cohesive-zone model

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 5 2006
Giulio Alfano
Abstract A new method to combine interface damage and friction in a cohesive-zone model is proposed. Starting from the mesomechanical assumption, typically made in a damage-mechanics approach, whereby a representative elementary area of the interface can be additively decomposed into an undamaged and a fully damaged part, the main idea consists of assuming that friction occurs only on the fully damaged part. The gradual increase of the friction effect is then a natural outcome of the gradual increase of the interface damage from the initial undamaged state to the complete decohesion. Suitable kinematic and static hypotheses are made in order to develop the interface model whereas no special assumptions are required on the damage evolution equations and on the friction law. Here, the Crisfield's interface model is used for the damage evolution and a simple Coulomb friction relationship is adopted. Numerical and analytical results for two types of constitutive problem show the effectiveness of the model to capture all the main features of the combined effect of interface damage and friction. A finite-step interface law has then been derived and implemented in a finite-element code via interface elements. The results of the simulations made for a fibre push-out test and a masonry wall loaded in compression and shear are then presented and compared with available experimental results. They show the effectiveness of the proposed model to predict the failure mechanisms and the overall structural response for the analysed problems. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Hybrid germanium/silica optical fibers for endoscopic delivery of erbium:YAG laser radiation

LASERS IN SURGERY AND MEDICINE, Issue 1 2004
Charles A. Chaney MS
Abstract Background and Objectives Endoscopic applications of the erbium (Er):YAG laser have been limited due to the lack of an optical fiber delivery system that is robust, flexible, and biocompatible. This study reports the testing of a hybrid germanium/silica fiber capable of delivering Er:YAG laser radiation through a flexible endoscope. Study Design/Materials and Methods Hybrid optical fibers were assembled from 1-cm length, 550-,m core, silica fiber tips attached to either 350- or 425-,m germanium oxide "trunk" fibers. Er:YAG laser radiation (,,=,2.94 ,m) with laser pulse lengths of 70 and 220 microseconds, pulse repetition rates of 3,10 Hz, and laser output energies of up to 300 mJ was delivered through the fibers for testing. Results Maximum fiber output energies measured 180±30 and 82±20 mJ (n,=,10) under straight and tight bending configurations, respectively, before fiber interface damage occurred. By comparison, the damage threshold for the germanium fibers without silica tips during contact soft tissue ablation was only 9 mJ (n,=,3). Studies using the hybrid fibers for lithotripsy also resulted in fiber damage thresholds (55,114 mJ) above the stone ablation threshold (15,23 mJ). Conclusions Hybrid germanium/silica fibers represent a robust, flexible, and biocompatible method of delivering Er:YAG laser radiation during contact soft tissue ablation. However, significant improvement in the hybrid fibers will be necessary before they can be used for efficient Er:YAG laser lithotripsy. Lasers Surg. Med. 34:5,11, 2004. © 2004 Wiley-Liss, Inc. [source]