Manufacturing Technology Today

S. S. K. Titus ¹, S. K. Jain ¹

Affiliations
1 Force and Hardness Standards, National Physical Laboratory, New Delhi, IN
2 Force and Hardness standards, National Physical Laboratory, New Delhi, IN

Abstract

The SI unit of force is more accurately realized through calibrated dead weights and is linked to the international prototype kilogram or a dead weight force close to 10N. As there is a growing need for traceable, accurate measurements involving micro and nano forces, such mass based force standards do not remain practicable for realizing such low forces. In view of this, National Metrological Institutes (NMIs) have started developing their indigenous facilities for realizing the small forces in order to disseminate the same to the user industries. In this paper, we have discussed the recent trends in the emerging field of low force metrology. The efforts made at NPL to take force measurement capacity to fraction of a Newton are described. A newly designed frame used in a dead weight system for generating the lowest possible force step of 0.5N is reported. The feasibility studies undertaken to increase our capability in realizing small forces further to the mili and nano Newton ranges are also briefly described.

Keywords

Low Force Metrology, Force Compensating Balance, Electrostatic Balance.

Full Text

     

S. K. Jain ¹, Rajesh Kumar ¹, S. S. K. Titus ¹

Affiliations
1 Force and Hardness Standards, National Physical Laboratory, New Delhi, IN

Abstract

Material hardness evaluation is one of the most important and commonly used methods of material or product testing. However, the hardness measurements being done in the industry are of limited accuracy due primarily to non-availability of standard hardness blocks having very precise and accurately assigned hardness values traceable to national primary standard. The National Physical Laboratory has recently added the primary standard of Brinell hardness scale to the other already available Vickers and Rockwell hardness primary standards. The uncertainty of the Brinell hardness standard is within ±1.5% for HB1/1 to HB1/30 and is within ±1.0% for other HB scales, which is reaffirmed through comparison with precision hardness standard blocks. Some of the salient features of the machine are described and the measurement results obtained on standard hardness blocks are reported.

Keywords

Brinell Hardness, CMC, Dead Weight Force, Standard Hardness Blocks.

Full Text

     

S. K. Jain ¹, Harish Kumar ¹, S. S. K. Titus ¹

Affiliations
1 National Physical Laboratory (CSIR), Dr K S Krishnan Marg, New Delhi, IN

Abstract

A new 1 MN force standard machine using dead weight force up to 100 kN and lever multiplication of dead weight force up to 1000 kN has recently been installed at NPL (I). The metrological performance of the machine including the uncertainty of the force realized and its relative deviation from the force values measured by precision force transfer standards calibrated in the PTB force standard machine of equivalent uncertainty has been evaluated. The measurement results affirm the estimated uncertainty of the force realized, which is within ±20 ppm on the dead weight side and within ±90 ppm on the lever side. The construction and operational mechanism are described and the measurement results are reported in this paper.

Keywords

Force Standard Machine, Lever Cum Dead Weight Machine, CMC.

Full Text