Fracture Surface Analysis

When metallic material is broken, breakage mode will vary by various reasons such as material property, degree of stress which caused breakage, repeated effect of stress increase and decrease, temperature, time, and environment conditions, etc. Cause of breakage can be roughly identified from the breakage mode by observing fracture surface of the broken metallic material with electron microscope, etc. Fracture surface analysis is a powerful tool for fracture cause investigation.

Photo on the upper left is fracture surface instantaneously broken with little deformation of the material under impact loading at low temperature. This is called brittle fracture. Photo on the upper right is fracture surface of high temperature crack of weld metal of stainless steel, and columnar structure during solidification can be observed.

Photo on the lower left is fracture surface of fatigue fracture observed after long-time effect of repeated stress increase and decrease. As a feature of the fracture surface of fatigue fracture, fine striped pattern called striation can be observed. Photo on the lower right is fracture surface occurred after tearing off the material by the loading of a large force. Fine dents called dimples cover entire surface and it is called ductile fracture.