Accession Number : ADA304451

Title :   Photoelastic Studies of Crack Propagation and Arrest in Polymers and 4340 Steel.

Descriptive Note : Annual rept. 15 Jul 77-30 Sep 78,

Corporate Author : MARYLAND UNIV COLLEGE PARK DEPT OF MECHANICAL ENGINEERING

Personal Author(s) : Irwin, G. R. ; Kobayashi, T. ; Fourney, W. L. ; Metcalf, J. T. ; Dally, J. W.

PDF Url : ADA304451

Report Date : DEC 1978

Pagination or Media Count : 330

Abstract : This report describes the progress made during the fourth year on a research program dealing with the dynamic characterization of fracture. The significant findings during the past year include: (1) An evaluation of the BCL procedure for determining K sub IDm' indicated that BCL reference curves predict velocities that are too high and predict values of the stress intensity factor which are too low. (2) An evaluation of the MRL procedure for determining K sub Ia showed that K sub Ia was within 4.5 per cent of the photoelastically determined value of K sub Im. (3) A new ultra high speed recording system was developed for recording dynamic fringe patterns in birefringent coatings. (4) Studies of the stress intensity factor associated with propagating cracks in 4340 steel gave a a vs K relation which compared favorably with results previously published by BCL. (5) Comparisons of crack behavior in duplex specimens fabricated from plastic/plastic and steel/steel indicate that the processes of crack propagation, crack arrest and crack re-initiation are similar in both types of specimens. (6) The investigation of crack propagation in ring specimens with mechanically simulated thermal stresses showed significant differences in the stress intensity factor associated with static crack extension and dynamic crack propagation. Dynamic propagation occurs at much lower values of K than static crack extension. (7) Studies of dynamic crack propagation in CT specimens (Homalite 100) fabricated with and without face grooves indicated that the effect of the face grooves is not significant on crack behavior. (8) The physical and mechanical properties of Araldite B were determined and found to be in close agreement with results published previously.

Descriptors :   *POLYMERS, *STEEL, *CRACK PROPAGATION, *PLASTICS, VISCOELASTICITY, ARRESTING(PROCESS), DISPLACEMENT, FRACTURE(MECHANICS), COATINGS, STRAIN GAGES, CREEP, BIREFRINGENCE, BONDING, CALIBRATION, THERMAL STRESSES, PHOTOELASTICITY, STRESS CONCENTRATION.

Subject Categories : Properties of Metals and Alloys
      Plastics
      Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE