Question

2. Explain why Charpy impact specimens of steels fractured in the middle of the ductile to brittle transition region fail by brittle fracture in the center and ductile fracture at the edges (See Ref. [10], p. 89).

Answer 1

A finite part simulation of the Charpy take a look at is developed so as to model the ductile
to brittle transition curve of a pressure vessel steel. the fabric (an A508 steel) and also the experimental results ar given during acompanion paper.

The projected simulation includes an in depthdescription of the fabric viscoplastic behavior over a good temperature vary. Ductile behavior is sculptured victimization changed
Rousselie model. The Beremin model is employed to explain brittle fracture. The Charpy take a look at is simulated employing a full 3D mesh and accounting for adiabatic heating and make contact with between the specimen, the striker and also the anvil.

The developed model is like minded to represent ductile tearing. victimization brittle failure parameters known below −150◦C, it'sattainable to represent the transition curve up to −80◦C forward that the Beremin stress parameter σu is freelance of temperature. Above this temperature, a temperature dependent Beremin stress parameter, σu, shouldbe accustomed properly simulate the transition curve. Quasi–static and dynamic tests will then be systematically sculptured.

Charpy V–notch impact tests ar still wideaccustomed study the fracture properties of steels. This take a look at was 1st projectedquite a century past. The take a look at is straight forward to perform and has been wideused since then. This testing mode was ab initioaccustomed confirm gross characteristics likethe Charpy fracture energy CVN.

Instrument Charpy devices ar currently used which permitto live the full force displacement curve from that a lot of data is gained.

However these knowledge ar representative of the fabric and of the specimen so it remains troublesome to transfer these knowledge to actual massive structures.

In this paper, a micromechanical analysis of the Charpy take a look at is projected. The aim is to work out model parameters that ar intrinsic to the fabric. The parameters ar then accustomedsimulate the Charpy take a look at so gross characteristics is foretold and compared to actual tests so as to validate the model. This strategy permits one to transfer the results of the tests to larger structures with associate degree enlarged level of confidence.

The first numerical simulation of the Charpy take a look at was projected by Norrisvictimization plane strain conditions. Effects of fabric rate sensitivity, of temperature dependence, of the 3D pure mathematics and of specimen size were studied during a series of theoretical papers lacking of comparisons with experiments.