Estimation of Correct Long-Seam Mismatch Using FEA to Compare the Measured Strain in a Non-Destructive Testing of a Pressurant Tank: A Reverse Problem

Estimation of Correct Long-Seam Mismatch Using FEA to Compare the Measured Strain in a Non-Destructive Testing of a Pressurant Tank: A Reverse Problem

Chitaranjan Pany
Copyright: © 2021 |Pages: 13
DOI: 10.4018/IJSVST.2021010102
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Abstract

This paper discusses the design criterion of a pressurant steel tank made of HSLA 15CDV6 and proof pressure test (PPT) as a non-destructive examination. An inverse Ramberg-Osgood relation is used to represent the stress-strain curve of the material. Elasto-plastic finite element analysis (FEA) has been carried out to examine the adequacy of the design. Experimental stress analysis has been carried out from the measured strains and found maximum effective stress is at LS joint (max. measured strain location). Strain obtained from FEA is compared reasonably well with the proof pressure test (PPT) data at most of the strain gauge locations except at one long-seam (LS) joint. So, to explain the causes of difference in strains near one LS, parametric studies have been performed in a 3D FEA with varying LS mismatch to find the correct mismatch as a reverse engineering problem. It is found that a mismatch value of 0.9 mm will give the required strain at PPT, which is measured only 0.4 mm. The failure pressure estimated through nonlinear FEA/analytical expressions found to meet the design.
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Finite Element Analysis

The HSLA steel pressurant tank in Figure 1 is basically a cylindrical shell capped with torispherical end domes. The cylindrical shell portion of the tank will be stressed high under internal pressure and hence it governs the design. The shell thickness is arrive at based on membrane shell theory, considering the weld mismatch effects (Harvey,1985).

Figure 1.

Configuration of pressurant tank: measured thickness (t) in mm) /weld mismatch(long-seam(LS) and cir-seam(CS)) in mm and Bi-directional (hoop and meridional) strain gauge(SG) locations. Maximum measured LS planner weld mismatch = 0.4 mm at location 2a, 2b and maximum measured CS planner weld mismatch = 0.6 mm at location 3a,3b

IJSVST.2021010102.f01

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