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Minimum radius of curvature

The exibility of a strain gage is characterized by the minimum radius of curvaturewhich it will withstand, without any auxiliary measures, in each direction respectively. The polyimide carriers of series Y and C strain gages are exible to an extent that they can be bonded around edges. Although the carrier materials of the other strain gage series are more brittle, they can also be easily prepared for application to smaller radii by thermal pre-forming. Exception: V series strain gages have a bigger radius of curva- ture because of their specic potting.

Fatigue life

If a strain gage is subjected to an alternating strain which can be superimposed over a static mean strain, an increase in the number of load cycles may create changes with regard to the zero point. The fatigue life is dependent upon the number of strain cycles and their amplitude and is independent of applied strain duration.
remainingzero point error(in m/m)1030100300 failurenumber of load cycles w(in mm/m) ε alternating strain n Example diagram of the fatiguelife of strain gages

Alternative bonding materials

For each strain gage series, the relevant bonding materials are specied. With regard to bonding technique, the HBM range of accessories distinguishes among cold and hot curing adhesives as well as spot welding methods. One of the most important selection criteria is the application temperature range of the individual bonding materials. Strain Gages and Accessories17