Threaded-pipe connectors are commonly employed in jointing pipelines in hydraulic and pneumatic systems. In an effort to avoid catastrophic incidences from the pipeline deteriorating, it is crucial to comprehend physical and mechanical properties on the thread connections. This paper is purportedly focused on the stress-and-strain analyses of the threaded pipe connector made of Al-6061-T6 (1 1 4 PT), the material of construction of aircraft structures and petroleum facilities, under preload and with internal pressure. Under the preloaded junction, both first and last threads in the pipeline connection are at most susceptible. With the internal pressure, the threaded-contact stress becomes more homogeneously distributed. Because of the contact stress, poising on the first few threads under the preloaded stage, being flattened, the last thread bears the highest contact stress. Finally, we execute an empirical experiment to reveal deformation phenomenon for the threaded-pipe connector, whose result corroborates the previous simulation studies.

ARTICLE INFO ABSTRACTArticle history:Today, environmental issues have become a matter of worldwide concern.In particular, automobile industries engage in considerable research and investment to develop high-efficiency and ecofriendly cars. Most ecofriendly cars use natural gas or hydrogen gas instead of fossil fuels. In this regard, low-weight and high-pressure vessels have gradually been developed to increase the driving distance of a car. However, most pressure vessels installed in cars develop many defects over time owing to shocks sustained when the car is being driven. Such defects can cause the explosion of the pressure vessel. Therefore it is important to prevent such explosions due to internal defects. The use of shearography for measuring the internal defects of objects afford many advantages. It is a non-contact and non-destructive method, and it is not limited by the object shape. In this study, the internal defect deformation and strain of an aluminum liner that is used in a CNG bus for the fuel storage tank is measured using shearography. It is important to measure the strain and deformation in order to detect defects and repair the pressure vessel. To verify the accuracy of the shearography measurement method, the measurement results of shearography, out-of-plane ESPI, and FEM are compared quantitatively.