The Art of Practical and Precise Strain Based ... - Webprofile.info

More documents

Recommendations

Info

Strain-Based Measurement Introduction:the fill fluid. Gases dissolved within the fill fluid can result in cavitationunder certain operating conditions. The implication of having acompletely oil-filled rigidly-confined volume is that the oil, whenheated, will tend to expand, but cannot. The internal pressure will risedramatically with increasing temperature producing large case strain,as shown in Figure 1-31.FIGURE 1-31. Fluidic Damping, Thermal Implications:Housing Distortion created by internal pressure risewith increasing temperature MassAcceleration FoundationSeals:Highly-Stressed atHigh TemperaureDamping FluidThe inclusion of an internal gas-filled expansion-absorbing bladder toaccommodate the fluid volumetric expansion is workable in the largeraccelerometer designs but is difficult to implement with the more miniaturizeddesigns. In completely fluid-filled designs, the pressure mayrise by as much as 2,000 psi per 100 degrees F. As a consequence, thisinternal pressure will act upon the available internal area producingforces that will stress the integrity of the sensor seals and will mechanicallystress the structure of the accelerometer. The loss of dampingfluid cannot be confirmed by visual inspection due to the small volumeof fluid present internally and the high possibility of the fluid beingexternally sourced. To detect the loss of damping fluid, an initial fre-CHAPTER 1-60 The Art of Practical and Precise Strain Based Measurement 2nd Edition © 1999
MagnitudeofResponseMagnitudeofResponseApplications Note 1-10:quency-sweep of the accelerometer is performed to establish the maximumresponse peak at a known and controlled temperature.FIGURE 1-32. Detection of Damping Fluid Leakage:Magnitude Response Plot BeforeThermal Cyling1z = .7ThermalCycling1w/w 0logHot/ ColdIncreased Peak is evidence of leakage1z = .51logw/w 0Magnitude Response Plot AfterThermal Cycling Showing Evidenceof Damping Fluid LeakageThe accelerometer is then thermally cycled several times from low to hightemperature and the frequency sweep is repeated. By comparing the initialfrequency sweep to the post thermal-cycling sweep, any increase in themaximum response peak is a direct indication of damping-fluid loss (Ref-The Art of Practical and Precise Strain Based Measurement 2nd Edition © 1999 CHAPTER 1-61
Page 1 and 2:
The Art of Practical andPrecise Str
Page 3 and 4:
Special Credits:Mrs. Helen Pierson,
Page 5 and 6:
Table of ContentsBy James G. Pierso
Page 8 and 9:
ContentsApplications Note 4-10:Lead
Page 10:
ContentsCHAPTER 8Electrical Conside
Page 13 and 14:
CHAPTER 1Strain-BasedMeasurementInt
Page 15 and 16:
Applications Note 1-1: Introduction
Page 17 and 18:
Applications Note 1-1: Introduction
Page 19 and 20:
Applications Note 1-2:The Art of Ap
Page 21 and 22: Applications Note 1-31. The presenc
Page 23 and 24: Applications Note 1-3result in a pe
Page 25 and 26: Applications Note 1-4:The measureme
Page 27 and 28: Applications Note 1-4:uncertainty i
Page 29 and 30: Applications Note 1-5:All strain-ba
Page 31 and 32: Applications Note 1-6:Applications
Page 33 and 34: Applications Note 1-6:ical size of
Page 35 and 36: Applications Note 1-6:and where:j i
Page 37 and 38: Applications Note 1-6:5. millivolts
Page 39: Applications Note 1-6:.Electrodynam
Page 44 and 45: Strain-Based Measurement Introducti
Page 104: Strain-Based Measurement Introducti
show all

The Art of Practical and Precise Strain Based ... - Webprofile.info

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?