ASTM E 1561 : 2026

1.1The primary use of three-element strain gage rosettes is to determine the directions and magnitudes of the principal surface strains and stresses. This practice defines a reference axis for each of the two principal types of rosette configurations used and presents equations for data analysis. This definition is important for consistency in reporting results and for avoiding ambiguity in data analysis—especially when computers are used. There are several possible sets of equations, but the set presented here is perhaps the most common.

1.2The equations presented in Section 4 of this practice are derived from infinitesimal (linear) strain theory. They are accurate for the low strain levels normally encountered in the stress analysis of typical metal test objects. They become detectably inaccurate for strain levels greater than about 1 %. Rosette data reduction for larger strains is beyond the scope of this practice.

1.3This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.