Method for detecting axial residual stress of small-inner-diameter pipeline

The invention discloses a method for detecting the axial residual stress of a small-inner-diameter pipeline. A small-inner-diameter pipeline part with the length of 600mm is cut from one end of a to-be-measured small-inner-diameter pipeline and is used as a detection element; a first strain gauge is pasted at the position at a distance of 300mm to the end portion of the detection element and a second strain gauge is pasted at the position at an included angle of 180 degrees with the first strain gauge along the circumferential direction, wherein the two strain gauges are pasted totally and thelength directions of the two strain gauges are consistent with the length direction of the detection element; an initial value is measured and an instrument is reset; parts at distances of 20mm to the two sides of the central part of the detection element are set and a circular ring with the length of 40mm is cut down along the peripheral direction based on the two parts, a final value of the axial residual stress is measured, and an average value of residual stresses of two testing points is calculated, so that the axial residual stress value of the small-inner-diameter pipeline is obtained.The method is simple; the strain gauge positions and the cutting position are selected reasonably; and the residual stress of the detection element can be measured quickly and accurately.