No abstract

No abstract

Adiabatic shear bands in steel are sometimes referred to as "white martensite". These bands are a unique and definitive indication of dynamic high speed deformation. Often the location, intensity and thin lathe (shear band) geometry make it difficult to confirm by x-ray diffraction or micro-hardness testing. Even with light non-standard micro-hardness test loads, detection is an insidious aspect except that explosive forces are necessary. Therefore, metallography is from a practical perspective the most powerful evaluation method to determine the effect. Extreme care in sample preparation and etching must be exercised. In this matter EDS analysis verified the white bands were not from the mating stainless steel components. The adiabatic effect occurs in one dynamic event, not to be confused with impact fatigue [1], a progressive failure [2]. The following examples were documented from ordnance components. Adiabatic effects occur most often by abusive pressures (5 times the factory test pressures) or severe obstruction in shotgun locking notch areas. The notch is observed to be upset and deformed. A cross section through the notch indicates a crescent shaped adiabatic shear band. In 70-30 brass cartridges, the classic wedge shear band has been characterized in 5.56 mm high speed SCAMP (Small Caliber Ammunition Manufacturing Process) products, as a rare but significant longitudinal failure mode in ballistic testing [3]. This matter involves threaded joints in steel where the forces are explosively high.