Proposal of a new hybrid weight drop test based on the Pellini test

Abstract

The high mechanical stresses that may be linked to the operation of French Navy ships and in particular the operating conditions of submarines must be considered right from the preliminary design phases. The failure to define special requirements may expose large-sized parts or weld fabricated assemblies to the risk of sudden fracture in the presence of flaws or cracks, right from the phase of admission of the naval platform to active service. This risk needs to be ruled out through laboratory tests. As early as the 1950s, Pellini’s work led to the development of several tests aimed at preventing this type of risk. The best known of these tests is the eponymous test or drop weight test. While this test became fundamental to determining the characteristic brittleness temperature of ferritic steels, Pellini also developed other less well-known tests. The impact of preparing the test pieces for this Pellini test gave rise to numerous studies, the guiding principle being to consolidate the resulting reference nil-ductility transition temperature (RT_NDT), which is a key element in guaranteeing the service life of a nuclear reactor component in service. The work presented in this article focuses on fracture behaviour and the prevention of sudden fractures on nuclear propulsion components. The study is focused on the work of William S. Pellini in order to propose a “modified” Pellini test giving access to a toughness transition (type T0) with a test that costs less to implement and requires less material. This article presents an experimental strategy and makes a comparison between different test results obtained on several parts to give credit to the approach and build a strategy to standardise the method.