Accession Number : ADA195695

Title :   Further Study of the Dynamic Tensile Failure of Concrete.

Descriptive Note : Final rept. 15 Jun 87-14 Feb 88,

Corporate Author : SRI INTERNATIONAL MENLO PARK CA

Personal Author(s) : Gran, James K ; Seaman, Lynn

PDF Url : ADA195695

Report Date : Apr 1988

Pagination or Media Count : 129

Abstract : This report describes a small follow-up effort to a previous study of dynamic tensile failure of concrete in which our long-range objective is to understand and quantify the micromechanics of dynamic tensile failure of concrete. In the previous study, we developed an experimental technique to apply dynamic tension to 5-cm-diameter x 76-cm-long concrete rods at a strain rate of about 10/s, and we performed posttest computations with a simple one-dimensional strain softening model to interprete an initial set of experiments. In the current effort, our primary task was to scrutinize the technique for observing microcracks in damaged specimens and to quantify the microcracks in some of the specimens already tested. A second task was to computationally interpret more of the experimental results. Third, we made a preliminary step toward computing the strength and modulus of a material cell containing several interacting cracks. Three methods for inspecting the concrete specimens for microcracking were evaluated. The first method was to use a scanning electron microscope (SEM) to view the concrete surface. We found this method to be unsatisfactory because of extensive cracking caused by evacuating the specimen. The second method was to replicate the specimen surface with acetylcellulose replicating film and to view the film with the SEM. This method introduces uncertainties in identifying cracks. The third method was to a view a polished concrete surface with an optical microscope at a magnification of 100x. This is the preferred method for observing microcrack damage produced in the dynamic tension tests. (sdw)

Descriptors :   *CONCRETE, *FAILURE(MECHANICS), *TENSILE STRENGTH, CELLS, COMPUTATIONS, CRACKS, DAMAGE, DYNAMIC TESTS, DYNAMICS, ELECTRON MICROSCOPES, ELECTRONIC SCANNERS, INTERACTIONS, LABORATORY PROCEDURES, MATERIALS, MECHANICS, MICROCRACKING, MICROSCOPES, OPTICAL EQUIPMENT, STRAIN RATE, SURFACES, TENSION

Subject Categories : Ceramics, Refractories and Glass

Distribution Statement : APPROVED FOR PUBLIC RELEASE