DISTRIBUTION OF BENDING STRESSES ALONG A ROD ON "UP" AND "DOWN" INTERVALS OF A WELL ZENITH ANGLE
The article presents data of studies of bending stresses with account of their non-linear distribution along rods' length during column longitudinal movement "up" and "down" on "up" and "down" intervals of a well zenith angle. Bending stresses of longitudinal-cross deformation are defined by solving of the fourth degree differential equation allowing to consider not only shaft curvature radius, but also cutting forces in rods crossing sections. It is shown that amplitudes of bending stresses change near threaded connection due to reduction of curvature radius may be comparable with endurance limit of rod material and sometimes even overpass it. Just this fact explains the great number of rods' failures in oil and gas fields.