Development of elastic proving devices for the control of force standard machines

Weiler, W. W.; Sawla, A.

doi:10.1088/0022-3735/6/8/027

Cited by 2 publications

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“…With such machines, it is possible to produce known forces to relative standard uncertainties of 1 × 10 −5 or better. Considerable resources are required to establish a deadweight machine of capacity 500 kN or above, and in this range force standards often consist of more complex machines utilizing smaller weights with lever amplification, or machines using hydraulic amplification [3]. With machines using hydraulic amplification, it is possible to produce known forces to relative standard uncertainties of 5 × 10 −5 or better.…”

Section: Introductionmentioning

confidence: 99%

A novel hydraulic force standard machine

McIlraith

Clarkson

2002

Meas. Sci. Technol.

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A hydraulic force standard machine covering the range 40 kN-1.5 MN has been designed, built and tested. Preliminary measurements indicate that this force standard can be self-calibrated to a relative standard uncertainty of 1 × 10 −4 or better and is linear to 0.31 kN. The design of this force standard is suitable for much larger machines generating forces up to 20 MN. The special features of this machine include the use of controlled clearance for the limitation of oil flow, thus enabling the generation of high pressures and large forces, the use of journal bearings external to the high-pressure region to give high stiffness against side thrusts, and a method of calibration that involves determining the slope of the curve force versus pressure. This calibration procedure is essentially a null method that is largely independent of load cell properties such as hysteresis, creep, long-term drift and state of calibration, in contrast to current build-up calibration techniques that are strongly dependent on load cell properties.

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Section: Introductionmentioning

confidence: 99%

A novel hydraulic force standard machine

McIlraith

Clarkson

2002

Meas. Sci. Technol.

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“…A commonly used method for the establishment of absolute standards of pressure [l, 21 and force [3,41 employs the principle of the hydraulic ram, where a piston surrounded by a cylinder is acted upon by oil at pressure P. In the case of the pressure standard, the upthrust on the piston due to the pressure P is opposed by the downward force exerted by local gravity g on the piston and on weights supported by it. At balance P=mg/A, where m is the total mass of the piston and the supported weights and A is the effective area of the piston.…”

Section: Introductionmentioning

confidence: 99%

Analysis of Controlled Clearance Seals

MacIlraith¹,

Fitzgerald²

1992

Metrologia

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An analytic approach, based on thin-wall theory, to analysis of the "controlled clearance" method bf restricting the gap between a shaft and a surrounding cylinder is presented. A modified form of thin-wall theory allows this analysis to be extended to seals with outside to inside diameter ratios up to 2,3. The effects of (a) the supply pressure, the jacket pressure, the pressure dependence of the viscosity of the oil and the geometry of the system on (b) the deformation of the cylinder, the pressure profile in the gap between the shaft and the cylinder and the flow of oil are illustrated. A path using this information is given for the design of a controlled clearance seal. It is shown that when the jacket pressure and the supply pressure are equal (reentrant cylinder condition) the supply pressure needed to close the gap is infinite. The difference between this result and that for a cylinder with a built-in end, for which the supply pressure for closure is finite, is discussed. Experimental tests are described and the results are shown to agree with computed figures based on the theory. This work is of particular relevance to hydraulically actuated standards of pressure and force, where "simple" piston-cylinder assemblies suffer excessive deformations at pressures beyond 50 MPa.

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Development of elastic proving devices for the control of force standard machines

Cited by 2 publications

References 0 publications

A novel hydraulic force standard machine

A novel hydraulic force standard machine

Analysis of Controlled Clearance Seals

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