Weld Delayed Fracture Evaluation Using Crack Initiation Load
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Solution Overview
Problem
Existing methods for evaluating delayed fracture properties of welds in metal materials, such as the gap test method and tensile shear strength tests, fail to quantitatively assess hydrogen-induced delayed fracture due to variations in residual stress and microstructure caused by welding, leading to inaccurate evaluations.
Innovation Solution
A method involving hydrogen introduction, tensile load application, and evaluation of crack initiation load based on displacement-load curves, with specific conditions for nugget diameter and tensile speed, allows for accurate quantification of hydrogen-induced delayed fracture properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If the strength of steel material is increased to reduce weight, then weight reduction is achieved, but susceptibility to hydrogen embrittlement and delayed fracture increases
Solution Approach 1:
The patent changes the evaluation parameters from conventional methods (nugget diameter, tensile shear strength) to a new parameter system based on displacement-load curves. By introducing hydrogen and applying controlled tensile loads, the patent evaluates delayed fracture properties through crack initiation load and displacement at crack initiation, which are more sensitive to hydrogen embrittlement effects in high-strength steel welds
Solution Approach 2:
The patent replaces the conventional mechanical evaluation method (tensile shear strength test) with a hybrid electrochemical-mechanical method. Hydrogen is introduced through electrochemical means (immersion in hydrochloric acid or cathodic charging), and the evaluation is performed through mechanical tensile testing with detailed curve analysis, providing a more comprehensive assessment of hydrogen-induced delayed fracture
2Reliability
If conventional evaluation methods (gap test method, tensile shear strength test) are used, then evaluation of weld strength is performed, but accurate quantification of hydrogen-induced delayed fracture properties is not achieved
Solution Approach 1:
The patent introduces feedback mechanisms through detailed analysis of displacement-load curves. By monitoring the relationship between displacement and load during tensile testing, the patent identifies specific points (crack initiation point, maximum load point) that provide feedback on the hydrogen embrittlement state. This feedback enables precise quantification of delayed fracture properties that conventional methods miss
Solution Approach 2:
The patent performs preliminary hydrogen introduction before mechanical testing. By immersing the welded specimen in hydrochloric acid or applying cathodic charging prior to tensile testing, the patent ensures that hydrogen is adequately introduced into the weld zone in advance. This preliminary action allows the subsequent mechanical test to accurately reveal hydrogen-induced delayed fracture characteristics
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
The proposed method enables precise quantification of hydrogen-induced delayed fracture properties by using the crack initiation load as an index, providing a reliable assessment of material superiority or inferiority in hydrogen resistance.
Implementation Method 1
a phenomenon called delayed fracture is more likely to occur... herein particularly refers to a hydrogen embrittlement fracture caused by entry of hydrogen into a steel material
Implementation Method 2
applying a tensile load to the test material into which hydrogen has been introduced and acquiring a displacement-load curve
Implementation Method 3
evaluating a crack initiation load based on the displacement-load curve
Data Source
Figure 1(a)~1(b)
Figure 2~3(a)
Figure 3(b)
AI summary
The present invention is directed to providing a method for evaluating delayed fracture properties of a weld of a metal material, which can quantitatively evaluate the delayed fracture properties of the weld with high accuracy. The method for evaluating delayed fracture properties of a weld of a metal material includes: a hydrogen introduction step of introducing hydrogen into a test material composed of two or more metal materials having a weld; a tensile load application step of applying a tensile load to the test material into which hydrogen has been introduced and acquiring a displacement-load curve; and a first evaluation step of evaluating a crack initiation load based on the displacement-load curve.