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Determination of Stress Intensity Factor Distributions for "Interface" Cracks in Incompressible, Dissimilar MaterialsThe present study was undertaken in order to develop test methods and procedures for measuring the variation of the stress intensity factor through the thickness in bimaterial specimens containing cracks within and parallel to the bond line using the frozen stress photoelastic method. Since stress freezing materials are incompressible above critical temperature, and since thick plates are to be employed which tend to produce a state of plane strain near the crack tip, the interface near tip fracture equations reduce to the classic form for homogeneous materials. Moreover, zero thickness interfaces do not exist when materials are bonded together. It was decided early on that it would be important to insure a uniform straight and accurate crack tip region through the thickness of the body to reduce scatter in the SIF distribution through the thickness. It was also observed that rubberlike materials which were desired to be modeled exhibited significant tip blunting prior to crack extension and that some blunting of the tip would provide a more realistic model. It should be noted that, in normal stress freezing photoelastic work, it is considered good practice to avoid utilizing data near bond lines in photoelastic models due to the bond line stresses which inevitably develop when two parts are bonded together. Thus, the present study involves certain exploratory aspects in deviating from standard practice in stress freezing work. With the above ideas in mind, several different test methods were investigated and are described in the following sections and appendices. The geometry selected for the program was a thick, edge cracked specimen containing a bond line.
Document ID
19980017339
Acquisition Source
Langley Research Center
Document Type
Contractor Report (CR)
Authors
Smith, C. W.
(Virginia Polytechnic Inst. and State Univ. Blacksburg, VA United States)
Date Acquired
September 6, 2013
Publication Date
January 1, 1997
Subject Category
Structural Mechanics
Report/Patent Number
NAS 1.26:206491
NASA/CR-97-206491
Funding Number(s)
CONTRACT_GRANT: NAG1-1622
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.
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