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An Investigation of Crack Propagation With a Wedge Indenter to Improve Rock Fragmentation Efficiency.

Authors
Larson-DA; Morrell-RJ; Mades-JF
Source
MISSING :28 pages
Link
NIOSHTIC No.
10005778
Abstract
The Bureau of Mines conducted basic experiments to study the process of crack propagation with a wedge indenter. The work was conducted under plane stress conditions in a hard, brittle limestone. The purpose of these experiments was to first gain an understanding of the basic crack propagation process under a sharp indenter, and second, to determine how the crack propagation process could be used to improve mechanical fragmentation systems. Three methods of rock fracture with the wedge indenter were investigated in this program. These were the confined indentation tests, the unconfined splitting tests, and the edge chipping tests. The confined indention tests represent worse case conditions for crack growth, and formed the lower bound on fracture efficiency. The unconfined splitting tests represented best case conditions and fixed the upper bound of fracture efficiency. The edge chipping tests represented an idealized fragmentation process based exclusively upon the highly efficient fracture propagation process. Edge chipping achieved a specific energy of 25 in.Lbf/in3 compared with conventional drag cutters, which required a specific energy of at least 2,385 in.Lbf/in3. Thus edge chipping is up to 100 times more efficient than conventional drag cutting. Because of these promising results, more work is planned with the fracture propagation process in three dimensions.
Publication Date
19870101
Document Type
IH; Report of Investigations;
Fiscal Year
1987
NTIS Accession No.
NTIS Price
Identifying No.
RI 9106
NIOSH Division
TCRC;
Source Name
MISSING
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