Tensile Strength of Threaded Rods Made by 3D Printing of Polymeric Material

The extension of 3D printing processes for parts made of polymeric materials highlighted the possibility of manufacturing threaded surfaces through such processes. In principle, the operation of a threaded joint involves tensile forces in the threaded rod. The dimensional characteristics of the threaded surface and some input factors in the 3D printing process can influence the tensile strength of threaded rods made of polymeric materials. An experimental research aimed at the tensile behavior of a threaded joint was designed, using a plastic screw and a special steel nut. A factorial experiment was designed and implemented to identify an empirical mathematical model capable of highlighting the influence of the dimensional characteristics of the threaded surface and some of the input factors in the 3D printing process on tensile strength. The test samples from polymeric materials were manufactured by 3D printing, then subjected to tensile tests. The mathematical processing of the experimental results allowed the determination of a mathematical model that allows the inclusion of the ordering of the factors taken into account in terms of the intensity of the influence that these factors exert on the tensile strength of the threaded rods. It was found that the diameter of the threaded rod exerts the strongest influence on the tensile strength of the threaded rod obtained by 3D printing, increasing the diameter of the threaded rod causing an increase in the maximum deformation of the rod. Increasing the thread pitch leads to a decrease in the maximum deformation of the threaded rod.

Determination of the coefficient of friction in a screw joint loaded with a controlled torque

The aim of this article is mechanism description for the measuring the friction coefficient in the threads of threaded joint and consecutive experimental measuring of friction coefficient. The coefficient of friction in the threads of a bolt and nut depends on a number of factors, in particular the roughness of the surfaces, the properties of the lubricating film and the angle of the side of the thread. The coefficient is a function of the heat treatment, the quality of the surface protection substance, the size of the screw load and the pitch angle of the thread. The principal parameters of the measuring was fastening torque, which was choose by the torque wrench, axial strength, measured by axial force sensor, and calculated friction coefficient. The friction coefficient was calculated through the use of exponential equation of the torque balance in the screw. The value of the friction coefficient was examined on the threaded joint of size M20 without the plastic lubricants and with the plastic lubricants. Measured values of friction coefficient was close to values listed in the norm and makes argument that plastic lubricants can decrease the friction coefficient in the threads of threaded joint.

Reducing the risks of rejects when assembling a stepped cylindrical body by direct control of the input size

An indirect control of a stepped assembled cylindrical body by the input size to a curved pipe by combined verification of the radial runout of the middle section of the body and the limiting gauge of the diametrical dimensions of the centering thickenings of the body is considered. It is shown that it is impossible to achieve the specified accuracy of a part by complete interchangeability, and the probabilistic method does not exclude errors in identifying defects. A direct control of the input size of a stepped cylindrical body is proposed by installing it with extreme centering nubs into roller prisms with right angles and checking the size perpendicular to the face of the prism. Keywords: stepped assembled cylindrical body, error, size, shape, basing, threaded joint, adjacent cylinders, contours [email protected]

Influence of transverse ultrasonic vibrations on the efficiency of threaded joint assembly

The disadvantages arising during assembly of threaded joints are considered. The existing methods of improving the quality of a threaded joint are analyzed and the most promising one is identified - the use of ultrasound at the assembly stage. Dependence of the unscrewing moment on the main technological parameter, which is vibration amplitude is obtained.