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API - WI 2348 Methodology to provide Mechanical Assurance in DCB test

API - WI 2348 Methodology to provide Mechanical Assurance in DCB test. Supporting for Work Group 085c Double –Cantilever-Beam (DCB) Test. API Winter Meeting - Dallas/Addison Tue 21th 2014 - 8:00 am. Outline. Summary of activities to date Results of CRC experimental program (Shell)

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API - WI 2348 Methodology to provide Mechanical Assurance in DCB test

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  1. API - WI 2348Methodology to provide Mechanical Assurance in DCB test Supporting for Work Group 085c Double –Cantilever-Beam (DCB) Test API Winter Meeting - Dallas/Addison Tue 21th 2014 - 8:00 am

  2. Outline • Summary of activities to date • Results of CRC experimental program (Shell) • Conclusions and next steps WI targets • To review the compliance formula existing for Chevron notch, how does it match with EDM configuration. • EDM configuration to be adopted. Existing EDM 35 mm or EDM 32 mm (Line-up). • Correct Young modulus to be used for Compliance formula

  3. Summary of activities to date – FEA models Numerical analysis through FEA model of DCB specimens (2D and 3D) with Chevron and EDM. Contribution from USS, V&M and Tenaris Main Conclusions • EDM line up (shorter) configuration has the smallest difference considering variation of P/B vs. crack length with respect to Chevron notch • EDM lineup specimen has more similar initial cracking driving force to Chevron starter specimen than current standard EDM specimen. EDM line up configuration has been adopted by NACE TM0177 ballot • For cracks exceeding 2 inches long, the percentage variation of lift load is lower than 3%.Therefore the same variation in compliance is expected • Difference of 5% in Compliance between Current equation and 3D Model could be attributed to a slight geometric difference between them (currently under review) and will be verified after Experimental program.

  4. Summary of activities to date – Experimental program Experimental program on DCB specimens with EDM notch is being conducted at CRC (Shell Lab in Calgary – Canada). This work has been donated by Shell. Activity under progress Scope of work and experimental procedure Material: Grade C110 ODxWT177.8x11.51 mm. Mechanical Properties : YS = 113 ±2ksi ; UTS = 126,5±2ksi; mean Hardness cross section 25.5±1 RC. Compliance determination: Load and line displacements will be measured by a clip-on gage monitored during the test. An average value of compliance will be obtained for each specimen/condition. Compliance determination will be performed at Shell Canada labs (CRC). Evaluated geometries: Two EDM configuration with four discrete crack lengths per each EDM configuration will be evaluated. Triplicates will be performed for each geometry. Total number of specimens 24. EDM 1 EDM 2

  5. Summary of activities to date – Young modulus Proactive discussion has been performed to get consensus on proposal for changing Young’s modulus that is being currently used in DCB compliance analysis. Based on contributions from Vallourec, NSSMC and Tenaris primary consensus achieved was to recommend : 210 GPa (30,5 x106 psi) for T95 and C110 material. However, taking into account that API 5C3 standard has stated a Young modulus value of 30,0 x 106 psi (207 Gpa),a final consensus was achieved to recommend such value as the right one to be used for Compliance check. Therefore the Young modulus value of 29,0 x 106 psi (200 Gpa) currently used on DCB compliance analysis, is recommended to be changed to a 30,0 x 106 psi (207 GPa) Proposal was submitted to the API RGPP (Resource Group on Performance Properties) to be considered. RGPP accepted the proposal.

  6. Experimental Program at CRC - ResultsBackground: Crack / Slot Locations B ai = 1.25 inch 31.75mm Bn 32 mm Chevron slot Chevron starter specimen ai Chevron with precrack (0.04”-0.12”) (2.065-3.048mm) from chevron base slot ai = 1.38 inch 35.05 mm 35 mm EDM EDM current standard away from base 0.13” (3.302mm) slot ai = 1.25 inch 31.75 mm 32 mm EDM EDM line up with Chevron base slot 0.13”

  7. Experimental Program at CRC - ResultsCompliance for Different Configurations

  8. Experimental Program at CRC - ResultsCompliance for Different Configurations – Larger crack length

  9. Experimental Program at CRC - ResultsCompliance for Different Configurations – Shorter crack length

  10. Experimental Program at CRC - ResultsExperiments vs. USS FEA New Chevron re-analysis (in the presentation) was performed by using experimental Chevron data and a/h = 2.25 and the fitted curve is very similar to the old compliance equation, with slightly variation for shorter crack length.

  11. Experimental Program at CRC - ResultsComparison 32 & 35 EDM vs. new Chevron

  12. Comments from CRC testing (Szklarz) • As received order of stiffness from more to less: Chevron, 32 mm EDM, 35 mm EDM • As cracks grow the order becomes 32 EDM, chevron and 35 EDM. More chevron data will be obtained. • The two EDM configurations are not exactly the same. The 35 mm is slightly less stiff as expected because it has a longer slot (more material removed) • At long cracks the compliance difference in percentage becomes less because the numbers are larger. • The good news is that the modulus given is accurate as seen by the long cracks in the chevron DCB data. • It seems the existing chevron compliance formula becomes less accurate for short cracks. It is good for 40 mm and longer. • The chevron compliance equation will change as more tests are done. • All the equations are similar for long cracks. • A simple factor between the equations does not seem possible. • Waiting for arrival of the remaining chevron DCBs. • Data from Chevron testing not include old data but the new one . Calculated crack length should be used for the calculation for the compliance analysis.

  13. Discussions from WG internal meetings 32 EDM configuration is closer to the Chevron compliance equation than the 35 EDM configuration. More testing are needed on shorter crack to figure out what the numbers for the crack length is. To collect more data for Chevron evaluation and re-analysis on all the data for Chevron using the new crack length definition (a/h = 2.25).

  14. Conclusions and next steps • For longer crack length any equation fit for compliance • For shorter crack length there are discrepancies that need to be studied further. • 32 EDM configuration seems to be better than 35 EDM configuration to be used. • Action Items pending • Tenaris is working on machining for more Chevron specimens to be shipped to CRC Calgary for testing in shorter crack length (Completed and already sent to CRC) • To schedule the Chevron specimens for testing at CRC (Karol Szklarz) • To go back and re-analyze all the data for Chevron using the crack length definition. (Karol Szklarz).

  15. Deliverables from the WI to recommend NACE TM0177 • Young modulus to be used for Compliance formula. Already taken by TM0177 ballot as per WI 2348 revision with George Waid. • EDM configuration as Line up (32 mm). Also already taken by such ballot. • Compliance formula to be included in Appendix D . Not yet consensus has been achieved on which equation is the best to be recommended. Nevertheless the current Chevron notch equation is included in Appendix D on TM0177 ballot. It is expected WI 2348 will be getting consensus before next API Summer meeting at June.

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