Volume 18, Issue 4 (July 1990)
Plastic Strain Ratio (r) for Sheet Metal: Effect of Gage Length and Width Measurement Locations Using Reduced Section Specimens
Recent advances in computer-controlled testing technology have resulted in the capability of determining r-values during routine tension testing. During axial straining, there are differences in width reduction over the length of the reduced parallel section due to shoulder constraint. Because of these changes in width reduction, the magnitude of the calculated r-value is dependent upon the gage length and width measurement location. The use of a 50 mm (2 in.) or less longitudinal strain sensor with a single transverse center width sensor does not presently comply with ASTM Test for Plastic Strain Ratio r for Sheet Metal (E 517). Yet the data from this work demonstrate that excellent r-value results can be obtained using a 50 mm (2 in.) longitudinal sensor with a single center transverse sensor while still maintaining a 57 mm (2¼ in.) reduced parallel section which complies with ASTM Tests and Definitions for Mechanical Testing of Steel Products (A 370) and Tension Testing of Metallic Materials (E 8).