Downloaded from https://www.everyspec.com MIL-STD-1312B 1. Obtain the static load - strain (or a quantity proportional to strain) relationship for the dynamometer using a static testing machine or dead weights. NOTE 1: Whenever the term “strain” is used in this recommended practice, it is understood that any quantity proportional to strain is acceptable. 2. loading at each of the desired maximum and minimum loads and teat frequencies in the fatigue testing machine. Measure the straina in the dynamometer during cyclic 3. instrumentation readings to loads-using the static load-strain relationship.
This approach assumes that the load strain relationship for the dynamometer la the same under cyclic loading as it is under static loading. The extent to which this assumption is justified is not known precisely at this time. Convert the measured straina or appropriate 60.2 Strain transducer. The dynamometer shall be instrumented with a transducer in such a way as to permit a determination of the average strain in the uniform section of the dynamometer and determination of the amount or percent of bending applied to the dynamometer when it is subjected to an axial load. The transducer shall be sensitive to force changes of 0.2 percent of the maximum load of the dynamometer range. a.
One acceptable transducer consists of not less than four nominally identical electrical resistance strain gages mounted longitudinally on the uniform section of the dynamometer, at points equally distributed around the section and equidistant from the ends of the section. Provision shall be made for recording the strain sensed by each gage individually for evaluating the amount of bending in the dynamometer. For determination of average strains, provision shall be made for connecting diametrically OppOsed gages in series,each pair in oppositearms of a Whetstone bridge.
In the other two arms of the bridge, four gagesidenticalto the four gagesabove shallbe mountedtransverselyon the dynamometerand connectedin pairs so as to providetemperaturecompensation(ace Figure 2). NOTE 2: The use of 90-degree rosette gages is acceptable.’ NOTE 3: Transducers for uae on electromagnetic systems should be ,, made from nonmagnetic materiala such as titanium. 1 11