Thin-Walled Pipe Fracture Toughness Testing via Segmented Specimen
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Solution Overview
Problem
Current methods are inadequate for measuring in-plane fracture toughness of thin steel pipes used in the oil and gas industry, as standard fracture toughness test specimens require thicker material than typically available, making it difficult to assess resistance to hydrogen-induced cracking (HIC) in critical directions.
Innovation Solution
A method and apparatus that involve machining a notched component from the pipe material with a central notch oriented in the S-L or S-T direction, and coupling lateral extensions to increase the effective thickness, allowing for standard fracture toughness testing that provides valid measurements compliant with ASTM standards.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If standard fracture toughness test specimens (SEB or CT type) are used, then valid FT measurements can be obtained, but sufficient material thickness is required which is not available in thin pipe walls
Solution Approach 1:
The test specimen is divided into two separate components: a thin-walled pipe segment containing the actual material to be tested, and a separate thickening component (extension piece) that provides the required thickness. These segments are assembled together to form a complete test specimen that meets ASTM standards while using only a small amount of actual pipe material.
Solution Approach 2:
A thickening component acts as an intermediary element between the thin pipe wall and the testing machine. This intermediary component provides the missing thickness dimension, allowing the thin-walled pipe segment to be tested according to standard procedures without requiring the full thickness that would normally be needed.
2Adaptability or versatility
If pipe wall thickness is reduced to accommodate thin pipe applications, then equipment design flexibility is improved, but ability to perform standard FT tests in S-T and S-L directions is lost
Solution Approach 1:
The testing system is segmented into the actual pipe material segment and a separate thickening component. This allows the pipe wall thickness to remain thin for design flexibility while the added component enables standard testing procedures to be performed on the assembled specimen.
Solution Approach 2:
The solution addresses the thickness dimension problem by adding material in the thickness direction through the thickening component, while maintaining the original thin dimensions in the plane of the pipe wall. This dimensional addition allows standard testing without compromising the thin-walled design.
3Ease of manufacture
If FT tests are performed in directions other than S-T and S-L, then testing can be conducted with available material, but the FT values cannot be reliably used to estimate in-plane fracture toughness
Solution Approach 1:
The specimen is segmented to include the thin-walled pipe portion with the specific orientation needed for S-T or S-L testing, combined with a thickening component that provides structural support. This segmentation allows the critical thin-walled section to be oriented correctly for in-plane fracture toughness testing while still meeting dimensional requirements.
Data Source
AI summary
A method of testing a material sample of a type used in a wall of a structure in a standard test for in-plane fracture toughness evaluation. The method comprises obtaining a sample having a lateral length no larger than a thickness of the wall of the structure, shaping the sample to have (a) a bottom surface, (b) a profiled top surface having a central notch, (c) a first coupling feature on a first side of the central notch, and (d) a second coupling feature on a second side of the central notch, assembling a test specimen which increases the width of the sample beyond the lateral width by coupling a first lateral extension to the first coupling feature and a second lateral extension to the second coupling feature, and applying a standard fracture toughness test to the so-assembled test specimen and sample to evaluate the fracture toughness of the sample.