Downloaded from https://www.everyspec.com MIL-STD-1312B ASTM E74 Verification of Calibration, Devices for Verifying Testing Nachines ANSI B46.1 Surface Texture (Surface Roughness, Waviness, and Lay) 30. SIGNIFICANCEOF ALIGNMENTAND DYNAMIC VERIFICATION ,,. while it is relatively easy to measure the forces applied to 30.1 a specimen under static condition, it is essential to ensure that excessive bending loads are not induced and to verify that the amplitude of the dynamic forces applied to the specimen agrees with the amplitude of the indicated loads within acceptable limits.
I 30.2 The presence of unknown and undesirahle bending loads induced through fatigue machine and/or fixture misalignment may severely reduce the fatigue life of test specimens and, hence, must be controlled within reasonable limits. I 30.3 The accuracy of the indicated loads may be dependent upon several factors which include: ,.: b. Configuration of the testing machine fixtures and specimen adapters. : a. Configuration of the specimen, including dimensions. c. Specimen material properties, including density, static and dynamic stress-strain characteristics, and material damping coefficient. d. Load settings of the testing machine controls. e. The waveform of the load cycle. f.
The frequency of the load cycle. 30.4 Ideally, the loads applied to a specimen in a fatigue test should be verified for each combination of the above factors. It is recognized, however, that within certain limits of variation, the effects of an individual factor on the loads IMY be small or reasonably predictable. 40. DEFINITIONS 40.1 Fatigue-testing machine. A device for applying repeated load cycles to a specimen. ,.: 40.2 Load. The force applied to the specimen. In the case of ~gue-testing machines, load is usually measured in units of pound-force or newtons. 8