Standard Test Method for Ambient Temperature Fatigue Life of Metallic Bonded Resistance Strain Gages

Importancia y uso:

4.1 Strain gages are the most widely used devices for measuring strains and for evaluating stresses in structures. In many applications there are often cyclic loads that can cause strain gage failure. Performance characteristics of strain gages are affected by both the materials from which they are made and their geometric design.

4.2 The determination of most strain gage performance characteristics requires mechanical testing that is destructive. Since strain gages tested for fatigue life cannot be used again, it is necessary to treat data statistically. In general, longer and wider strain gages with lower resistances will have greater fatigue life. Optional additions to strain gages (integral lead wires are an example) will often reduce fatigue life.

4.3 To be used, strain gages must be bonded to a structure. Good results, particularly in a fatigue environment, depend heavily on the materials used to clean the bonding surface, to bond the strain gage, and to provide a protective coating. Skill of the installer is another major factor in success. Finally, instrumentation systems shall be carefully selected and calibrated to ensure that they do not unduly degrade the performance of the strain gages.

4.4 Fatigue failure of a strain gage often does not involve visible cracking or fracture of the strain gage, but merely sufficient zero shift to compromise the accuracy of the strain gage output for static strain components.

Subcomité:

E28.01

Volúmen:

03.01

Número ICS:

19.060 (Mechanical testing)

Palabras clave:

fully reversed strain; gage factor; gage resistance; strain gages; strain gage fatigue life; strain gage fatigue test apparatus; super sensitivity; zero shift;