Stress and Deflection of Small-diameter and Thin-wall Pipes under Four-point Loading

Small-diameter and thin-wall pipes were difficult to prepare standard specimens and accurately load on due to their size constrains, when the stress-corrosion resistance testing was carried out. Four-point loading method was used to study the axial stress loading problem of navicular specimens of the small-diameter and thin-wall pipes, and the formulas for calculating the stress and bending deflection were deduced; the stress of the specimens was simulated by ANSYS software, and then the effect of load stress, chord height, wall thickness and outer radius on the error between calculated stress and actual stress was analyzed; finally, the lab tests were used to evaluate the error between calculated stress and actual stress of navicular specimens of the small-diameter and thin-walled pipes. The results show that:under the same condition, the error of the loading stress of positive-bending specimens was larger than that of reverse-bending specimens; the stress error increased with the increase of the outer radius, but didn't change with the loading stress; the effect of pipe wall thickness on the stress error was complicated; the influence of chord height on the stress error was the most significant; only when the chord height of reverse-bending specimens was less than 5 mm and the chord height of positive-bending specimens was less than 4 mm, the stress error between calculated stress and actual stress of navicular specimens of the small-diameter and thin-walled pipes was within the acceptable range in engineering.