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Title:Embrittling effect of small elastic stress waves on crack toughness in a structural steel
Author(s):Shoemaker, Alan Kent
Subject(s):Embrittling Effect
Elastic Stress Waves
Crack Toughness
Abstract:The reduction in static crack toughness, as measured by fracture mechanics KIc* values, was studied in an A 201B structural grade steel for the embrittlement caused by small amplitude elastic stress waves superimposed on the static stress state of an edge notched ¾ in. thick specimen. The stress waves were generated by five different methods of impacting the edge of the specimen on the side opposite to the crack tip when a static load existed on the specimen. The data showed a reduction 23% in the static KIc* over a temperature range of -220°F to -180°F when the specimen was impacted by a 1.312 in. diameter steel ball, 12 in. steel bar or hammer. A maximum transient tensile strain of 37.5 μ in/in normal to the crack was shown to cause crack extension. The transient strain was measured before and during the fracture test by high resistance strain gages fixed to the specimen ahead of the crack tip. A discussion of the waves measured in a long rod and a large plate is given in order to interpret the transient strain recordings made on the specimen. A four-point bending specimen was fractured by this method of embrittlement to show that this phenomenon is not just peculiar to one specimen geometry. The embrittlement was attributed to two effects: 1) a reduction in crack toughness value necessary for crack extension due to the rate at which the transient strain increased and 2) the superposition on the static KI value of the stress intensity factor, KI tran., caused by the stress wave amplitude. The possibility of damage, due to small stress waves, being done at the crack tip when crack extension does not occur is discussed. Data for 0.0005 in. radius and fatigue cracked notches showed consistent crack toughness values for the temperature range investigated. The theoretical and practical implications of this investigation are discussed.
Issue Date:1965-09
Publisher:Department of Theoretical and Applied Mechanics. College of Engineering. University of Illinois at Urbana-Champaign
Series/Report:TAM R 284
Genre:Technical Report
Sponsor:American Iron and Steel Institute, Committee on Properties of Iron and Steel
Rights Information:Copyright 1965 Board of Trustees of the University of Illinois
Date Available in IDEALS:2021-11-04

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  • Technical Reports - Theoretical and Applied Mechanics (TAM)
    TAM technical reports include manuscripts intended for publication, theses judged to have general interest, notes prepared for short courses, symposia compiled from outstanding undergraduate projects, and reports prepared for research-sponsoring agencies.

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