小直径薄壁管件四点加载时的应力与挠度

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

由于自身尺寸的限制,小直径薄壁管件在进行抗应力腐蚀性能检测时,难以制备出标准试样并准确加载。使用四点加载的方法研究了小直径薄壁管件舟形试样轴向应力加载问题,推导出了加载应力与弯曲挠度的计算公式;并结合有限元软件进行应力模拟,分析了加载应力、弦高、壁厚、外半径对计算应力和模拟应力之间误差的影响;最后采用试验的方式评估了小直径薄壁管件舟形试样的计算应力与实际应力的误差。结果表明:在相同条件下,正弯时试样加载应力的误差一般比反弯时的大;应力误差随外半径的增大而增大,但几乎不随加载应力的改变而改变;管材壁厚对应力误差的影响较为复杂;弦高对应力误差的影响最为显著,仅当反弯时弦高小于5mm和正弯时弦高小于4mm时,小直径薄壁管件舟形试样的计算应力与实测应力间的误差在工程允许范围内。

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 thinwall 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 thinwalled 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 5mm and the chord height of positive-bending specimens was less than4 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.