Three rail shear test

Fig. 3.24. Schematic drawings of loading fixtures in (a) two rail shear and (b) three rail shear test. After...

A more practical method is to use the two-rail or three-rail shear test (ASTM D 4255) (Figures 17.46 and 17.47), although Lockwood has questioned the reproducibility [65] of the test. The ASTM is not strictly a standard, but is referred to as a guide. 

The two-rail shear test is only suitable for the determination of shear moduli. The three-rail shear does give a better approximation to pure shear as the compressive load is applied parallel to the clamped edges of the specimen. 

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