Push/Pull Four-Point-Bending Apparatus

The figure depicts an improved apparatus for three- or four-point bending tests of stripe specimens. In a bending test, the specimen is subjected to tension along its top surface and compression along its bottom surface, or vice versa. A three- or four-point bending fixture of older design is capable of pushing from one side only, so that it can bend the specimen in one direction only; that is, it can induce either tension or compression (but not both) on the top or bottom surface. The present apparatus is capable of pushing on a specimen from either side and thus bending the specimen in either direction. Thus, for example, the apparatus can be used to perform a test in which the applied stress is varied continuously from a maximum tension through zero to a maximum compression.