Standard Test Method for Small Punch Testing of Metallic Materials

Importancia y uso:

4.1 The safety margins provided in the design for a component or structure can be reduced throughout its service life by aging. Aging is the process by which the physical and mechanical characteristics of component or structure materials change with time or use; this process may proceed by a single aging mechanism or a combination of several aging mechanisms.

4.2 The term “safety margin” is used in a broad sense, meaning the safety state (that is, integrity and functional capability) of components in excess of their normal operational requirements (1).

4.3 The determination of mechanical properties such as yield strength, tensile strength, and ductile-to-brittle transition temperature of structural components is, hence, desirable for optimization of operating procedures and inspection intervals, as well as repair strategies and residual lifetime assessment. Current standardized mechanical tests require relatively large volumes of test material that cannot be extracted from in-service equipment without post-sampling removal repair (2).

4.4 The need to obtain estimates of the mechanical properties of components without post-sampling removal repair has led to the development of small punch (SP) test techniques based on penetration/bulge tests of miniaturized test specimens (often disk-shaped, or square) (3-5). It can be considered as a quasi-nondestructive technique because of the very limited amount of material to be sampled. It is an efficient and cost-effective technique and has the potential to provide estimates of the material properties of the specific component, identifying the present state of damage and focusing on the most critical (most stressed, most damaged) locations in the component. Examples of empirical correlations that have been established between small punch test results and mechanical properties for specific classes of materials are provided in Appendix X1.

4.5 This test method can be also used for identifying the most suitable materials with respect to their resistance against operational damage, like neutron irradiation, thermal aging, etc., as well as for optimization of their chemical composition, thermal heat treatment, etc. This test method is beneficial in the study of the effect of radiation damage when test specimen dimensions are limited by small irradiation volume or high activity.

4.6 Due to the small sample size, this test method also allows estimating mechanical properties of non-uniform materials such as welds (6). Examples of weld techniques that produce narrow geometric gradients include electron beam or laser beam welds, and metal coatings (7, 8). This test technique provides a more direct means of estimating material properties than indirect methods based on laboratory simulations of the localized regions or analytical predictions based on generalized methods.

Subcomité:

E10.02

Volúmen:

12.02

Número ICS:

49.035 (Components for aerospace construction)

Palabras clave:

crosshead speed; deflection; displacement; ductile-to-brittle transition temperature; extensometer; failure; force; fracture; fracture energy; punch; strain; stress; ultimate tensile strength; yield stress;