MECHANICAL TESTING

Sharp Notch Tensile Testing - ASTM E 338

"Standard Test Method for Sharp-Notch Tension Testing of High-Strength Sheet Materials"
ASTM E338 covers the determination of a comparative measure of the resistance of sheet materials to unstable fracture originating from a very sharp stress-concentrator or crack. It relates specifically to fracture under continuously increasing load and excludes conditions of loading that produce creep or fatigue. The quantity determined is the sharp-notch strength of a specimen of particular dimensions, and this value depends upon these dimensions as well as the characteristics of the material. In addition to the sharp-notch strength, the yield strength ratio is also determined.

This method is not intended to provide an absolute measure of resistance to crack propagation which might be used in calculations of the strength of structures. However, it can serve a number of purposes.

In the research and development of materials it can be used to understand how fracture characteristics are affected by such variables as chemical composition, processing, heat-treatment, etc.

In design applications, it is often used to compare the relative crack-propagation resistance of a number of materials which are otherwise equally suitable for an application, or to eliminate materials when an arbitrary minimum acceptable sharp-notch strength can be established.

ASTM E338 can be used for specifications of acceptance and quality control when there is a sound basis for establishing a minimum acceptable sharp-notch strength

The sharp-notch strength may decrease rapidly through a narrow range of decreasing temperature. This temperature range and the rate of decrease depend on the material and its thickness. The temperature of the specimen during each test are therefore controlled and recorded. Tests are conducted throughout the range of expected service temperatures to ascertain the relation between notch strength and temperature. For design applications, care should be taken that the lowest and highest anticipated service temperatures, they are included in the testing program.

In addition to performing Sharp-Notch Tensile Testing for you, Touchstone can assist you in the development of your complete test program.

Index of Mechanical Testing