REVERSIBLE BONDED STRAIN GAGE :: essays research papers

ABSTRACT For accurately measuring thermal colours, particularly on large complex body parts where welded stemma seconds pecknot be utilize, a reversible bonded emphasis gage was developed. Basically it is a special polyimide strain gage which is same on both the base side and carry on side so that it stern be utilize both ways. It canful be used to measure strains at temperatures under 250oC (482oF) of a structure made of aluminum alloys or composites (to which its delicate to weld a strain gage).These gages can be can be peeled after winning demand app atomic number 18nt strain measurements in a furnace and can be attached reverse side up at a required point on a structure. To measure mechanical stresses on structures at high temperatures it is essential to measure seeming thermal stresses accurately in the first place. In practice, several strain gages in a inner circle are used to obtain calibration data. The apparent strain and gage factor change of all the g ages in the pack are expect to be same which is not so in practice, in antagonism of great efforts to reduce scatter of apparent strain. Since reversible strain gages can be reattached to the test structure after taking apparent strain readings, the error caused due to apparent strain scatter (by using contrastive strain gages) can be reduced to great extent. In this report the thermal characteristics of the reversible strain gage repeatability of apparent strain, gage-factor change, creep, drift and the payoff for a given mechanical strain were investigated.INTRODUCTIONThere are several problems associated with elevated temperature measurements, static or dynamic, the basic one creation that alloys useful as strain gages at these temperatures are also nice temperature sensors. Firstly, installation of the strain gage is a problem and secondly the apparent strain and change in gage factor makes it very difficult to measure the actual strain. In aerospace industry we come ac ross a lot of situations when very accurate strain measurements at high temperatures are required, but in spite of a lot of improvement in new high temperature strain gages most of them are welded types. Hence, they cannot be used on materials like aluminum alloys or composites. In this paper, a reversible bonded strain gage is described for use at temperatures under 250o (482oF) that can be applied to a structure made of materials commonly used in aerospace industry like aluminum alloys and various composites. Aircraft wings are often subjected to high temperature and high acoustic noise level and the application program of reversible strain gages to accurately measure the stresses is the main motivation foot choosing this paper for review.