METHOD FOR STRENGTHENING ELONGATED CYLINDRICAL PRODUCTS Russian patent published in 1999 - IPC

FIELD: strengthening pump rods in process of making them and after operation for powered depth-pump oil production. SUBSTANCE: method comprises steps of elastic and plastic deformation of product by lengthwise loading and torsion deformation at setting optimal modes of plastic deformation of product; carrying out lengthwise loading at rate (0.12-12.0) mm/s until elongation value of product exceeds by 0.1-9.0 times elongation value corresponding to proportionality range; then fixing value of elasto-plastic deformation of product, interrupting for 0.25-60 s and realizing torsion deformation at rate 0.002-1.8 rpm/s at simultaneous controlling value of lengthwise loading effort, terminating torsion deformation when loading effort is decreased by 1.25-4 times; after pause equals to 0.25-30 s completely unloading product from lengthwise tension load at rate 0.12-14.0 mm/s and after pause equals to 0.25-30.0 s completely removing torque at rate 0.01-1.8 rpm/s. EFFECT: enhanced quality of strengthening due to increased fatigue strength of product material.