Morphologies, failure fracture surface

Failure Investigation. The clamp was nonmagnetic and the stamped identification on the side of the U-shaped shells indicated that they were fabricated from forged 304 austenitic stainless steel. Visual examination of the fracture surfaces revealed they were entirely brittle and exhibited a very coarse fracture morphology. Liquid penetrant inspection revealed the presence of additional cracks in the fractured half of the clamp. There was no cracking present in the high-strength steel fasteners. 

Failure Morphologies. Ductile failure of notched polycarbonate specimens has long been recognized to occur with shear yielding from the notch tip (6). This occurs for the block polymers for all rates of test. Hull and Owen (5) recently reported from micrographic studies of impact fracture surfaces that the brittle failure of polycarbonate involves the formation and breakdown of a craze at the notch tip. The ductile-... 

Post-failure studies of the fracture surface morphology of bulk semi-crystalline polymers are more difficult than those of amorphous materials due to the more complex multiphase structure associated with semi-crystalline materials However, it was shown that some fractographic details point to the formation of a stress whitened region ahead of a notch prior to final fracture of the material. In particular, stress-whitened regions were easily visible in semi-crystalline polymers such as LDPE and HDPE The resulting, macroscopically apparently brittle fracture... 

Fracture Surface Morphology. While a complete study of fracture surface morphology and the micromechanisms of failure is still in progress, preliminary examination revealed major differences between the modified and neat PVC s. These are now being interpreted in order to elucidate the micromechanism of failure. 

Fracture surface analysis of fibers can provide useful information. In particular, for noncrystalline fibers, the following fracture parameters can be obtained from an analysis of features on the fracture surface morphology the mirror constant, an estimation of fracture toughness K c, failure stress, flaw-to-mirror radius ratio, fracture surface energy, and the time to failure. 

The unmodified epoxy system showed cracks at different planes on the smooth glassy surface, indicating brittle failure, while the fracture surfaces of the rubber-modified ones were rough, indicating massive shear deformation Figure 15.1. The morphology appeared as a phase-separated one with the dispersion of small rubber domains in the epoxy matrix. However, the particle size increased with increase in rubber content due to the coalescence process. 

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