Downloaded from https://www.everyspec.com MIL-STD-1312B Strain readings from Parameter Gage 1 GaKe 2 Gage 3 E!2@L ‘2400 lb load 573 570 604 603 Mean strain = 587 Minus mean 587 587 587 587 D~fference 14 17 17 16 Ave’ragedifference of gages 1 plus 3 frommean: 14 + 17 = 15.5 2 Average difference of gages 2 plus 4 from mean: 17 + 16 = 16.5 2 Maximum value frommean = ~15.52 + 16.52= 22.64 Percent bending = Maximum value from mean x 100 = 2264 = 3.86% MEAN m Rotate Alignment Cell 45 Degrees:
Strain readings from Parameter Gage 1 Gage 2 Gage 3 Gage 4 2400 lb’load 610 609 580 578 Mean strain = 594.3 Calculate as above for percent bending = 3.62% Average bending = 3.86 + 3.62 = 3.75%; i.e., less than 6% 2 80. PROCEDUREFOR DYNAMIC VERIFICATION OF FATIGUE MACHINES 80.1 General. Dynamic verification of the fatigue machine is required over the entire load range and frequency range where fatigue information ia desired for each type of specimen to be teated. The overall verification conaista of procedures covering both static alignment and dynamic operating conditions. 80.2 Measurementof dynamicstrains.
The instrumentationused to recordthe dynamicoutputof the transducershallbe the same a s that used to record the static strains. Using the null- balance method, adjuat the bridge ao that the peak of the load signal ia tangent to the ground trace on the oscillo- scope when the signal is switched rapidly between the dynamometer and ground. When using the dual beam oscillo- scope, adjust the bridge ao that the peak of the strain, signal is tangent to the ground signal and the adjustment to achieve a tangent relative to the applied dynamic load. 15