Fractography

About: Fractography is a research topic. Over the lifetime, 5043 publications have been published within this topic receiving 86068 citations.

New features of the low temperature ductile shear failure observed in bulk amorphous alloys

Abstract: Fractographic studies of ductile shear failure under the uniaxial compression for rod–like samples of the Zr41.2Ti13.8Ni10Cu12.5Be22.5 and Cu50Zr35Ti8Hf5Ni2 bulk amorphous alloys at temperatures 300 and 77 K are presented. The mechanisms of shear deformation and failure appeared to have characteristics in common with other amorphous alloys prepared in the form of thin ribbons. However, there were a number of new fractographic features observed due to the bulk character of the samples and to the large supercooled liquid region of these alloys.

Caustic Stress Corrosion Cracking of Mild Steel

Abstract: The stress corrosion cracking (SCC) behavior of cold worked mild steel in hot, aqueous, 33 pct NaOH solutions was studied with prefatigue cracked double cantilever beam specimens. SCC kinetics were studied under freely corroding potentials (E corr ≈ −1.00 VSHE) and potentiostatic potentials of −0.76 VSHE near the active-passive transition. The pH of the liquid within the crack was determined and fractography was studied by scanning electron microscopy. Cracking was transgranular atE corr, intergranular at −0.76 VSHE, and produced no detectable change in crack liquid pH from that of the bulk solution. Crack rates were dependent upon temperature, potential, and stress intensity (K 1). The apparent activation energy in Region II, where crack growth rate was independent ofK, was ∼ 24kJ/mol for both cracking modes. This was considered to be due to mixed rate control involving activation polarization and mass transport processes. The mechanism of cracking was entirely consistent with metal dissolution at –0.76 VSHE and may involve hydrogen embrittlement and/or dissolution effects atE corr.

Application of fractography to core and outcrop fracture investigations

Abstract: Purpose of this paper is to introduce geologists to the principles of fractography, especially those principles that govern the formation of fracture surface structures commonly observed in rocks. A knowledge of the inception mechanics governing the formation of a fracture's tendential and transient structures should provide geologists with a method to distinguish natural from coring-induced and handling-induced fractures in oriented core samples, and show how coring-induced fractures may be assisted in their formation by stresses that can be attributed to the drilling process. 118 figures.

The relationship between microstructure, fracture and abrasive wear in Al2O3/SiC nanocomposites and microcomposites containing 5 and 10% SiC

Abstract: Alumina/SiC nanocomposites are much more resistant to severe wear than monolithic alumina. In order to clarify the mechanisms responsible for these improvements, alumina and alumina/SiC nanocomposites with 5 and 10 vol.% SiC and various alumina grain sizes were fabricated. For comparison, a 10 vol.% SiC “microcomposite” was also fabricated using 3 μm SiC particles. The extent of cracking beneath hardness indentations was examined and the specimens were tested in abrasive wear. Quantitative surface fractography of the worn surfaces was carried out. The wear properties depended strongly on the grain size in pure alumina, but were independent of the alumina grain size in the nanocomposites. This is consistent with the idea that much of the improvement in wear resistance when SiC is added to alumina stems from a reduction in the size of the individual pullouts owing to the accompanying change in fracture mode. In addition, crack initiation by plastic deformation during abrasion and indentation was found to be strongly inhibited when 10 vol.% nanosized SiC was added to alumina. The addition of 3 μm “micro-sized” SiC did not have the same effect. The ability of fine SiC particles to suppress cracking is attributed to the blocking of twins and dislocation pileups by intragranular SiC nanoparticles. This reduces the length of the twins or pileups and hence their ability to nucleate microcracks.