Strain Gage Installation Tutorial. (That rocks!)

Bi-axial strain gages, often referred to as Poisson strain gages, are 90° tee rosette gages, aligned with the principal strains in uniaxial stress loading. They are also used extensively in column load cells and simple cantilever beam transducer applications.

T-rosettes are used where the direction of the principle strains are known. Strains at 90° enable calculation of the stresses at the measurement location, not possible with a single strain gage. Commonly used where tensile or compression material property tests are performed, they enable calculation of Poisson’s ratio as well as Young’s modulus. Using a T-rosette for this apparently simple test allows the user to make transverse sensitivity corrections for maximum accuracy of the test results.

In column load cells for example, the Tee Rosette strain gages are utilized to cancel bending strains and for cantilever beam applications, these sensors allow for gaging a single side of the spring element to reduce cost.

The tee rosettes minimize the number of gages needed for testing and provide reduced installation time and potential errors.

Tee rosettes Strain gages are also used to determine the Poisson’s Ratio for a material in accordance with ASTM standards.

They are also used where direct tension measurements, such as a bolt in tension or suspension rod in compression, is desired. A full bridge, produced by using two Tee-rosette strain gages, in this situation minimizes pickup due to bending. Tee rosettes can also be deployed for bending measurements, especially useful on large infrastructure such as wind turbine towers. Adjacent gages on the same backing will see identical temperature and therefore eliminate thermal outputs due to differential temperatures across the structure. Additionally, 45° alignment marks are provided on each T-Rosette gage so it may be accurately applied to a shaft to measure torsion.