Tensile testing pipe products presents unique challenges. Additionally, operators may inadvertently crush the ends of a specimen while gripping. Since full pipe samples are often over-sized, they require grips with a large opening; some pipe samples are so large that operators must cut a reduced section from the sidewall.
To prevent the test machine's grip jaws from crushing the full pipe samples, we inserted metal plugs into the ends of pipe (reference: ASTM A370). This technique is commonly used on pipe under 50 mm (2 in) in diameter. Using this method, we were able to use the machine's standard
in-head crosshead grips with V-grooved jaws. The crosshead grips provide an economical solution for testing large full pipe samples and allow you to test samples up to full machine capacity. We've also tested smaller-diameter specimens using a variety of external
wedge-action grips.
When testing flat samples (cut from the side wall of a pipe), operators can flatten the specimen ends and use either conventional grip faces or grip faces with curved surfaces. To capture strain, we used an industrial style extensometer designed for large specimens (up to 89 mm in diameter). Finally, to collect data and calculate results, we used
Partner™ Software. The software's specimen selection feature allowed us to enter pipe dimensions and automatically calculated the cross-sectional area for either full-section pipe or a machined specimen section. This saved us many hours of tedious calculations.
Because of the high forces required to break steel tube, we selected a hydraulically powered universal testing system (model 300DX) for this test. This SATEC™ Series frame provided the high capacity we needed, along with several nice options for testing large and heavy pipe and tube samples.