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Titolo:
A LOCAL MODULUS ANALYSIS OF RAPID CRACK-PROPAGATION IN POLYMERS
Autore:
IVANKOVIC A; WILLIAMS JG;
Indirizzi:
UNIV LONDON IMPERIAL COLL SCI TECHNOL & MED,DEPT MECH ENGN LONDON SW72BX ENGLAND
Titolo Testata:
International journal of fracture
fascicolo: 4, volume: 64, anno: 1993,
pagine: 251 - 268
SICI:
0376-9429(1993)64:4<251:ALMAOR>2.0.ZU;2-Z
Fonte:
ISI
Lingua:
ENG
Soggetto:
DYNAMIC FRACTURE; STRESS INTENSITY; TOUGHNESS; MECHANICS; ARREST; STATE;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
29
Recensione:
Indirizzi per estratti:
Citazione:
A. Ivankovic e J.G. Williams, "A LOCAL MODULUS ANALYSIS OF RAPID CRACK-PROPAGATION IN POLYMERS", International journal of fracture, 64(4), 1993, pp. 251-268

Abstract

This work is concerned with the analysis of rapid crack propagation (RCP) in Polymethylmethacrylate (PMMA), Polycarbonate (PC) and two-layer PMMA/PC systems. Remarkably constant crack speeds were observed, andhigher crack speeds corresponded to the higher preloads. Uniform fracture surfaces were associated with these constant speed RCPs. An indirect method was used to characterise dynamic fracture properties of thematerials. The method relies on the recorded crack length histories and boundary conditions which are incorporated in a dynamic Finite Element (FE) code to generate the crack resistance (G(ID)). The numerical simulation of the constant speed RCPs generated highly scattered G(ID)data. Very large variations of the computed G(ID) with the crack length did not correspond to fracture surface appearances. Geometry dependent and multivalued crack resistance results with respect to the crackspeed cast doubt on the uniqueness of G(ID). In this work, attempts were made to overcome these difficulties by exploring the concept that the anomalies arise from large local strains around the rapidly movingcrack tip, resulting in the crack 'seeing' a low local modulus. It isdemonstrated that the critical source of error on the analysis of RCP, is the improper linear elastic representation of the material behaviour around the propagating crack tip. Since the parameters describing the behaviour of the materials near the propagating crack tip were unknown, local non-linear effects were approximated by a local low modulus strip along the prospective crack path. The choice of the local modulus was justified by measurements of the strain histories along the crack path during RCP. The local strip low modulus model generated a larger amount of the kinetic energy in the sample and the crack resistance was reduced compared to results from the single constant modulus approach. Most importantly, G(ID) data were nearly independent of the crack length, crack speed and the specimen size. This local modulus concept was also successfully applied to the analysis of RCP in the duplex specimen configuration.

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Documento generato il 26/09/20 alle ore 01:27:36