Brittle Crack Arrestability Evaluation in Thick Steel Plates
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Solution Overview
Problem
The existing methods for evaluating brittle crack arrestability in steel plates, particularly in large structures, face inefficiencies due to Fracture Pass Deviation (FPD) where the brittle crack deviates from the embrittled region to the base metal, making it difficult to accurately determine the steel plate's crack arrestability.
Innovation Solution
A method involving finite element analysis and fusion welding to manage residual stresses in the embrittled region, forming a fusion zone in the base metal to balance stresses and prevent crack deviation, ensuring the crack propagates through the embrittled region, with specific conditions for the fusion zone's placement and dimensions to maintain stress balance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an embrittled region is formed at the notch tip to promote brittle crack generation and propagation, then crack propagation is enhanced, but Fracture Pass Deviation occurs where the crack deviates from the embrittled region to the base metal making evaluation ineffective
Solution Approach 1:
The patent applies preliminary anti-action by forming a fusion zone in advance at a specific position relative to the embrittled region. This fusion zone creates compressive residual stress that counteracts the tensile residual stress in the embrittled region before crack propagation begins, preventing the crack from deviating to the base metal and ensuring it propagates through the embrittled region as intended for accurate evaluation
Solution Approach 2:
The patent changes the stress state parameters by controlling the position and dimensions of the fusion zone relative to the embrittled region. By adjusting the distance d and length L of the fusion zone according to specific formulas, the residual stress distribution is modified to achieve stress balance, transforming the stress parameters to prevent crack deviation
2Productivity
If fusion welding is performed to form an embrittled region, then crack propagation is promoted, but tensile residual stress is generated causing crack deviation to base metal
Solution Approach 1:
The patent converts the harmful tensile residual stress generated by fusion welding into a beneficial configuration by strategically placing a fusion zone that generates compressive residual stress. This compressive stress counterbalances the tensile stress, and the harmful effect of residual stress is transformed into a beneficial stress balance that prevents crack deviation while maintaining test efficiency
Solution Approach 2:
The patent applies local quality by creating a localized fusion zone with specific dimensions and position relative to the embrittled region. The fusion zone is not uniformly distributed but is precisely positioned at distance d from the embrittled region with length L, creating localized stress compensation exactly where needed to prevent crack deviation without affecting the overall embrittling effect
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach significantly improves the effectiveness of crack arrestability testing by preventing FPD, enhancing test efficiency and accuracy regardless of varying testing conditions, thus providing reliable evaluations for steel plates.
Implementation Method 1
it is possible to remove a compressive residual stress in a base metal outside the embrittled region by forming a fusion zone in the base metal region
Implementation Method 2
by forming a fusion zone in the base metal region, in which a compressive residual stress is generated, to remove the compressive residual stress, the tensile residual stress in the embrittled region is removed
Implementation Method 3
by applying an impact load to the V-notch via a wedge while applying a predetermined stress to the test piece
Implementation Method 4
by cooling the test piece to a predetermined temperature, and by applying an impact load to the V-notch
Data Source
Figure 1
AI summary
Provided is a method for evaluating brittle crack arrestability of a steel plate. The present invention is a method for evaluating brittle crack arrestability of a steel plate by using a large test piece, in which a notch, at which a brittle crack is generated, is disposed on one edge in a central portion in a stress-application direction of the large test piece, in which an embrittled region having a predetermined length L extending in a propagation direction of the brittle crack is formed at a tip of the notch or formed so as to include the tip, and in which a fusion zone spaced from the embrittled region is disposed in at least one location in the test piece after the embrittled region is formed. The fusion zone is formed on one side or both sides of the embrittled region at a distance d from the embrittled region, where d is determined in relation to a thickness t of the steel plate, and a length of the fusion zone is determined by adding ΔL1 (0.3L to -0.3L) to a length L of the embrittled region and by subtracting ΔL2 (0 to 0.4L) from the length L, where ΔL2 denotes a distance between an edge of the test piece and an edge of the fusion zone. With this, since the brittle crack generated in the notch propagates without deviating from the predetermined embrittled region, FPD is prevented, which makes it possible to obtain effective CAT results.