Inherent problems in force measurement

Pontius, Paul E.; Mitchell, Richard A.

doi:10.1007/bf02325907

Cited by 7 publications

(8 citation statements)

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“…This occurred even after many cycles and the zero shift in the strain signal had been accommodated. The discrepancy is a result of the hysteresis effects (12) and is an important consideration when analysing the experimental results. …”

Section: Experimental Methodsmentioning

confidence: 99%

Forces in a Heavy-Duty Drive Chain during Articulation

Hollingworth

Hills

1986

Proceedings of the Institution of Mechanical Engineers, Part C:

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A rigid-body analysis is presented of the forces which occur in a chain bearing during articulation. Coulomb frictional effects due to unlubricated contact are included, as these provide the energy source for deleterious wear processes and affect the force distribution. The analysis differentiates between the two types of chain bearing-open end leading or open end trailing-and the results show that the force characteristics in each are significantly different. Experimental verification of the chain link tension is good. NOTATIONpin-bush normal contact force in articulating bearing link in tight span articulating chain link, precedes link Lo link engaged on sprocket number of teeth in driver sprocket number of teeth in driven sprocket chain link tension from tight span chain link tension immediately preceding articulating bearing bush internal radius bush outside radius bush-roller normal contact force in articulating bearing sprocket tooth force, upon articulating bearing total angle of articulation instantaneous angle of articulation coefficient of Coulomb friction between articulating pin-bush pair coefficient of Coulomb friction between articulating roller-bush pair nominal pressure angle angle of repose for pin-bush normal contact force with respect to corresponding link force angle of repose for bush-roller normal contact force with respect to the engaged tooth force 4 + m -e

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Section: Experimental Methodsmentioning

confidence: 99%

Forces in a Heavy-Duty Drive Chain during Articulation

Hollingworth

Hills

1986

Proceedings of the Institution of Mechanical Engineers, Part C:

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“…When the applied force acting upon a force transducer, such as a load cell, is changed rapidly to a new level and then remains constant, the force indicating system of the transducer yields a value that drifts, or creeps, with time before reaching equilibrium (providing that the transducer is sufficiently well-behaved to reach a stable value). As described By Pontius and Mitchell [ 4 ], this creep is largely attributable to thermoelastic effects: the adiabatic heating and cooling of elastic load supporting elements within a load cell as they undergo deflection in response to changes in the applied force. A rheological model for load cell behavior by Mitchell and Baker [ 5 ] shows that the load cell output following a sudden application (or release) of force can be described as a function of time by

where r is the load cell output, or response, t is time since the force application, and a 0 is the equilibrium response as t becomes very large.…”

Section: Load Cell Creep Responsementioning

confidence: 99%

Creep and creep recovery response of load cells tested according to US and international evaluation procedures

Bartel

Yaniv

1997

J. Res. Natl. Inst. Stand. Technol.

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The 60 min creep data from National Type Evaluation Procedure (NTEP) tests performed at the National Institute of Standards and Technology (NIST) on 65 load cells have been analyzed in order to compare their creep and creep recovery responses, and to compare the 60 min creep with creep over shorter time periods. To facilitate this comparison the data were fitted to a multiple-term exponential equation, which adequately describes the creep and creep recovery responses of load cells. The use of such a curve fit reduces the effect of the random error in the indicator readings on the calculated values of the load cell creep. Examination of the fitted curves show that the creep recovery responses, after inversion by a change in sign, are generally similar in shape to the creep response, but smaller in magnitude. The average ratio of the absolute value of the maximum creep recovery to the maximum creep is 0.86; however, no reliable correlation between creep and creep recovery can be drawn from the data. The fitted curves were also used to compare the 60 min creep of the NTEP analysis with the 30 min creep and other parameters calculated according to the Organization Internationale de Métrologie Légale (OIML) R 60 analysis. The average ratio of the 30 min creep value to the 60 min value is 0.84. The OIML class C creep tolerance is less than 0.5 of the NTEP tolerance for classes III and III L.

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“…Normal imperfections in the alignment of loading machines and force transducers can result in significant bending, shear, and twist components of deformation in the force transducer. To minimize the errors due to these nonaxial components of deformation, it is desirable to sample the response of the force transducer at several symmetrically distributed positions [ 7 , 8 ]. For this reason, the response of each force transducer was obtained at five positions relative to the axis of the machine (0°, 90°, 180°, 270°, 360°).…”

Section: Measurement Proceduresmentioning

confidence: 99%

Summary of the intercomparison of the force standard machines of the National Institute of Standards and Technology, USA, and the Physikalisch-Technische, Bundesanstalt, Germany

Yaniv

Sawla

Peters

1991

J. RES. NATL. INST. STAN.

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A comparison of force measurements performed at the National Institute of Standards and Technology, USA, and at the Physikalisch-Technische Bundesanstalt, Germany is reported. The focus of the study was the intercomparison of the forces realized by the two Institutes rather than the measurement process. The transfer standards used in the comparison consisted of force transducers and associated readout instrumentation. The results of the intercomparison reveal that over a range of 50 kN to 4.5 MN, the forces realized at NIST and at PTB compare favorably. For forces up to 900 kN the agreement is within ±40 ppm; above 900 kN the agreement is within ± 100 ppm.

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Inherent problems in force measurement

Cited by 7 publications

References 0 publications

Forces in a Heavy-Duty Drive Chain during Articulation

Forces in a Heavy-Duty Drive Chain during Articulation

Creep and creep recovery response of load cells tested according to US and international evaluation procedures

Summary of the intercomparison of the force standard machines of the National Institute of Standards and Technology, USA, and the Physikalisch-Technische, Bundesanstalt, Germany

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