Materials and Mechanics of Rate Effects in Brittle Fracture. Progress Report, October 1979-October 1980 PDF Download
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Author: Publisher: ISBN: Category : Languages : en Pages :
Book Description
Energy balance methods have been used to find the crack driving force in elastic fractures. The fracture toughness of cracked steel bars have been measured using these techniques. Crack tip dislocations have been shown to protect the crack tip by having a stress intensity value that is opposite in sign from the applied stress intensity value. Thus, crack tip dislocation plasticity shields the crack from the external stress intensity factor. In the fatigue of LiF single crystals a relationship between monotonic and fatigue hardening responses has been established using a statistical model for fatigue deformation.
Author: Publisher: ISBN: Category : Languages : en Pages :
Book Description
Energy balance methods have been used to find the crack driving force in elastic fractures. The fracture toughness of cracked steel bars have been measured using these techniques. Crack tip dislocations have been shown to protect the crack tip by having a stress intensity value that is opposite in sign from the applied stress intensity value. Thus, crack tip dislocation plasticity shields the crack from the external stress intensity factor. In the fatigue of LiF single crystals a relationship between monotonic and fatigue hardening responses has been established using a statistical model for fatigue deformation.
Author: Publisher: ISBN: Category : Languages : en Pages :
Book Description
A thermodynamic formulation for a crack driving force has been experimentally used in linear elastic fracture mechanics, elastic plastic fracture mechanics and creep fracture. In linear elastic and elastic plastic fracture mechanics, mechanical stability criteria are established from the load versus the load point displacement in two test specimens that differ only in crack area. These tests have also been used to measure the fracture toughness in several heat treated steels. Creep cracking of PMMA has shown that there is a sharp transition to unstable fracture in a plot of the log of the steady state crack velocity versus the crack driving force at several selected temperatures. In addition, it has been shown that the athermal crack driving force is independent of rate and temperature. A new method for electronically recording the crack driving force versus the crack area has been used on double cantilevered beam specimens. Temperature and crack rate dependences have been measured near the ductile to brittle transition temperature in a low carbon steel.
Author: Publisher: ISBN: Category : Languages : en Pages :
Book Description
The slow, isothermal, propagation of cracks was analyzed by introducing the fracture mechanics concepts into molecular rate theory. Relations between thermodynamic variables and measurable quantities such as crack velocities, specimen temperature and crack extension force were derived. The shape and distribution of the rate controlling obstacles were left unspecified in the theory. The theory was applied to published crack propagation data in PMMA and agreement between theory and data is found. A literature survey of crack velocity data in a wide selection of materials including inorganic glasses, ceramics, polymers and metals shows the correlation that the crack extension force is inversely proportional to the crack activation area. In rapid crack propagation, a new technique, measuring the complimentary boundary condition to the applied boundary condition was used to deduce the stress intensity factor and the crack velocity during crack propagation in DCB specimens. The technique is easier to use and gives better results than the electro-potential methods of measuring crack length during rapid fracture. The shear force in a rapidly wedged DCB specimen is multiplied by the square root of the time after the wedge strikes the specimen, this product is nearly constant during fracture, from its slight time dependence we deduce how K/sub ID/ and the crack velocity vary as a function of time. Time is eliminated and K/sub ID/ is plotted versus crack velocity.
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Author: ![Materials and Mechanics of Rate Effects in Brittle Fracture. Progress Report, October 1975--October 1976. [PMMA]. PDF](https://books.google.com/books/content/images/frontcover/NBTcwQEACAAJ?fife=w80-h100)
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Author: United States. National Bureau of Standards