Several techniques are reviewed for obtaining fracture toughness, impact energy, or flow data from subsized specimens. These specimens are useful when there is insufficient material or space (e.g., reactor vessel surveillance programs) for larger, more conventionally sized specimens. Such specimens are useful in other situations where, because of the structural configuration, it is appropriate to use small specimens (e.g., fusion first wall structures). The data obtained from these specimens may be (1) correlated with actual structural response or the response of larger specimens, (2) compared with test results on similar sized specimens (useful in tracking shifts in material behavior), or (3) used to provide input to fracture models.

Techniques for testing specimens of compact-tension, Charpy V-notch, and compression specimen geometries are described. Comparison is made with results from larger specimens in terms of ASTM validity criteria where possible.

Some of the specimens had been machined to substandard size from an ample amount of source material. For example, compact-tension specimens as small as 3 mm thick tested with valid fracture toughness results are discussed. Miniature Charpy specimens of similar size are also reviewed.

Other standard size specimens have been constructed from very small pieces of a limited volume of material. This approach may be useful to nuclear reactor surveillance programs. Rebuilt Charpy specimens consist of a crack tip region comprised of the original specimen to which two end tabs have been attached. The crack tip region of a compact-tension specimen is constructed from broken Charpy bars which are press-fit into a second piece of material with compact-tension shaped geometry. Results of testing these specimens are compared with those obtained from the original specimens of similar size.