BS EN ISO 15653:2018 pdf free.Metallic materials — Method of test for the determination of quasistatic fracture toughness of welds.
BS EN ISO 15653 specifies methods for determining fracture toughness in terms of stress intensity factor (K), crack tip opening displacement or CTOD (δ) and experimental equivalent of the J-integral for welds in metallic materials (J).
BS EN ISO 15653 complements ISO 12135, which covers all aspects of fracture toughness testing of parent metal and which needs to be used in conjunction with this document. This document describes methods for determining point values of fracture toughness. It should not be considered a way of obtaining a valid R-curve (resistance-to-crack-extension curve). However, the specimen preparation methods described in this document could be usefully employed when determining R-curves for welds. The methods use fatigue precracked specimens which have been notched, after welding, in a specific target area in the weld. Methods are described to evaluate the suitability of a weld for notch placement within the target area, which is either within the weld metal or within the weld heat-affected zone (HAZ), and then, where appropriate, to evaluate the effectiveness of the fatigue crack in sampling these areas.
5 Principle
This document specifies procedures for the determination of fracture toughness on notched-plus- fatigue-cracked specimens taken from welds. It pertains to situations where the fatigue crack tip is
a) located in relation to a weld feature of interest, referred to as “weld positional” (WP), and
b) specificallylocatedwith I namicrostructureofinterest,referredtoas”speci ficmicrostru ctu re”(S M).
Metallographic examination of the weld is used to confirm that the target weld feature and/or microstructure is indeed present at the crack tip and in sufficient quantity for testing.
Specimen geometry and notch orientation are chosen, and a fatigue crack then extended from the specimen’s notch tip into the target weld feature or microstructure by applying a controlled alternating force to the specimen. The purpose of the test is to determine weld fracture toughness in the absence of significant residual welding stresses. To achieve this and to produce a straight-fronted fatigue crack,modifications to the fatigue precracking procedure may be required. These modifications are usually necessary when testing as-welded or partially stress-relieved welds.
The fracture toughness test is performed and evaluated in accordance with Iso 12135, but subject to additional requirements of this test method regarding post-test analysis (see 12.2.1, 12.2.2 and 12.2.3) and qualification (see 12.3).
Post-test metallography is often required to make certain that the crack tip was located in the target weld feature and/or microstructure and to determine the significance of pop-ins.
The sequence of operations is summarized in Figure 1.
6 Choice of specimen design, specimen orientation and notch location
6.1 Classification of target area for notching
A specimen selected for weld positional (WP) testing is intended to test a defined weld region with respect to a reference position (e.g. the weld metal centreline).
A specimen selected for specific microstructure (SM) testing is intended to sample a specific microstructure along the whole or part of the crack front length within the central 75 % of the specimen thickness.