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Titolo:
THE INFLUENCE OF TEMPERATURE ON DYNAMIC FAILURE MODE TRANSITIONS
Autore:
RITTEL D;
Indirizzi:
TECHNION ISRAEL INST TECHNOL,FAC MECH ENGN IL-32000 HAIFA ISRAEL
Titolo Testata:
Mechanics of materials
fascicolo: 3, volume: 30, anno: 1998,
pagine: 217 - 227
SICI:
0167-6636(1998)30:3<217:TIOTOD>2.0.ZU;2-O
Fonte:
ISI
Lingua:
ENG
Soggetto:
LOADED PRENOTCHED PLATES; PROPAGATING SHEAR BANDS; CRACK INITIATION; POLYCARBONATE; FRACTURE; PMMA;
Keywords:
DYNAMIC FRACTURE; FAILURE MODE TRANSITIONS; POLYMERIC MATERIALS; GLASSY TRANSITION; FRACTOGRAPHY;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Science Citation Index Expanded
Citazioni:
24
Recensione:
Indirizzi per estratti:
Citazione:
D. Rittel, "THE INFLUENCE OF TEMPERATURE ON DYNAMIC FAILURE MODE TRANSITIONS", Mechanics of materials, 30(3), 1998, pp. 217-227

Abstract

A failure mode transition from opening to shear has been reported in shear impact experiments of commercial polycarbonate with increasing impact velocity (Ravi-Chandar, K., 1995. On the failure mode transitions in polycarbonate under dynamic mixed mode loading. Int. J. Solids and Structures 32 (6/7), 925-938; Rittel, D., Levin, R., Maigre, H., 1997. On dynamic crack initiation in polycarbonate under mixed-mode loading. Mech. Res. Comm. 24 (1), 57-64). Impact velocities ranged typically from 20 to 60 m/s and the experiments were carried out at room temperature. Similar transitions have been reported for metallic materials and shear band formation at high velocities has been related to crack-tip adiabatic heating and material softening. This paper investigates the role of crack-tip heating in the observed transition. Results are reported and discussed for high velocity (50-60 m/s) shear impact experiments of commercial polycarbonate whose temperature is varied in therange of -120 degrees C to +70 degrees C. Up to -40 degrees C, fracture proceeds along an initial kink angle of typically 60 degrees. At -25 degrees C the kink angle is reduced to 40 degrees and less. At room temperature and above, the specimens no longer fracture by separation. A 2-3 mm shear band is then clearly noticeable at the crack-tip. Scanning electron and optical fractographic examination of the specimens confirm the initial operation of a shear fracture mechanism at -25 degrees C (T-eq = 0.59 T-g in [K]), in contrast with an opening fracture mechanism at lower temperatures (crazing). Assuming that shear failure results from local heating above the glass transition temperature (150degrees C), the crack-tip temperature elevation is estimated to be atleast 175 degrees C. Significant crack-tip temperature changes put limitations on the usual assumptions of isothermal dynamic crack initiation. (C) 1998 Elsevier Science Ltd. All rights reserved.

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Documento generato il 27/11/20 alle ore 02:24:44