Influence of the notch shape of pre-notched small punch specimens on the creep failure time

• Three techniques used to achieve the initial notch in the SPCT specimens.
• For WEDM and TLIM the notch was blunted.
• PLIM yields a perfect crack without a rounded tip.
• Stress distribution at the notch tip during the test has been analyzed.

Nowadays, there are standards for determining the creep-fracture properties of a material. However, a sufficient amount of material to be tested is usually required, something that is not always possible or convenient. In certain cases where not enough material is available for carrying out conventional tests to determine these properties of the material to be analysed, there are now several non-standard tests that can achieve this purpose. One of them, the Small Punch Creep Test (SPCT), basically consists of punching, under a constant load, a miniature specimen in which the sides of the specimen are clamped between two dies. One of the greatest challenges at present is to obtain the creep-fracture properties of a material from this type of test using pre-notched specimens. To achieve this initial notch in the SPCT specimen prior to creep-fracture testing, there are several techniques which are being used at present. The main objective of this paper is to analyse the differences between these techniques, taking into account the shape of the pre-notch obtained and the stress distribution at the pre-notch tip during the test. In this way, it is possible to determine which of them is the most appropriate for estimating the creep-fracture properties of the material used.

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