Fracture Mechanics

Second of four problems on the A533B-1 welded plate: same temperature as Problem 1 LLAW (−120 ℃), same region, same measured residual-stress profile — the only variable is that post-weld heat treatment (PWHT) was applied. Here we run LLHT in mechCalc's BS 7910 Clause 7 fracture-assessment calculator and watch a counter-intuitive result: its primary SIF is actually higher than LLAW, yet the assessment point lands lower, because the residual K_I^S drops from 46 to 5.

One of the four A533B-1 welded-plate problems: the LLAW specimen — as-welded, −120 ℃, low load ratio. It is the first of the four to fracture (1.27 MN). This post walks step by step through entering, computing, and reading the FAD in mechCalc's BS 7910 Clause 7 Fracture Assessment Calculator, to see exactly how the residual K_I^S of 46 MPa·m^0.5 pushes the deepest-point assessment point to K_r=2.59, far beyond the Failure Assessment Line.

In the fracture-mechanics and fitness-for-service (FFS) literature, FITNET is a name you cannot avoid. This article traces the origins of the FITNET EU project from public sources: how it descends from SINTAP, who led and funded it, its scale, what the four modules of the FITNET FFS Procedure each cover, and why its fracture module is highly comparable to BS 7910.

A set of large welded A533B-1 steel plates tested in four-point bending to fracture, built to answer a question engineers keep asking: where exactly does welding residual stress push the assessment point on the Failure Assessment Diagram (FAD)? We first lay out the background and the shared method, then break the four specimens (LLAW / LLHT / HLAW / HLHT) into four problems, give the FAD inputs and results for each, and compare each result with the original literature, to see what residual stress and post-weld heat treatment each contribute.

FFS in one minute: can a structure with a flaw keep running? What methods do engineers use to decide?

A guide to BS 7910:2019 Clause 7 fracture assessment: starting from the two failure modes, it uses a single Failure Assessment Diagram (FAD) to tie together the fracture-mechanics principle, the K_I / σ_ref / K_r / L_r calculation chain, and the standard assessment steps — with original diagrams and a live worked example.

A walkthrough of the two K_mat estimation routes in BS 7910:2019 Annex J — the lower-shelf equation and the Master Curve — with full derivations, the T_K confidence margin explained, and three worked verification examples.

A walkthrough of the latest ASME BPVC Section XI Appendix Y models for fatigue crack growth and stress-corrosion cracking in austenitic, ferritic and nickel-base alloys, with a code-based online calculation guide.

How KTA 3206 treats fatigue crack growth in a Leak-Before-Break (LBB) argument: the Paris-Erdogan equation in the steady-state region, constants for ferritic and austenitic steels, the NUREG/CR-6176 term for high-temperature water, and a worked example.

An introduction to Leak-Before-Break (LBB): what it means, where it applies and where it does not, the main codes, the three analysis steps, and a nuclear piping example.