STUDY OF THE EFFECT OF MILLING CONDITIONS ON THE PHYSICAL AND MECHANICAL CHARACTERISTICS OF THERMOPLASTICS FOR SHIPBUILDING

The study objective is to investigate the effect of mechanical working of thermoplastics on their physical and mechanical characteristics under tension and bending. The task to which the paper is devoted is a systematic assessment of changes in the yield strength and elastic modulus of unreinforced thermoplastics (low density polyethylene and unplasticized polyvinyl chloride) used in small-capacity shipbuilding when the milling parameters (spindle rotation speed and feed per tooth) are varied, and to determine the optimal cutting conditions. Research methods: experimental milling of samples using CNC machine equipment under various operating conditions; conducting standard physical and mechanical tests for tensile strength (GOST 11262-2017) and static bending (GOST 4648-2014) using the REM 10 A 1 2 testing machine with an extensometer (a total of 840 samples were tested); methods of statistical analysis of arithmetic mean and median indicators. Novelty of the work: for the first time, a comprehensive systematic study is conducted of the effect of machining modes on the key mechanical characteristics in tension and bending of unreinforced sheet thermoplastic polymers used for small-capacity shipbuilding. Study results: changing the spindle rotation speed and feed per tooth leads to a change in the yield strength and elastic modulus of the materials under tension and bending by up to 10–12 %, which is within the range of statistical variability of the experimental data and instrumental errors. Conclusions: milling modes do not have a significant effect on the physical and mechanical properties of homogeneous thermoplastics. Selecting machining parameters based on the criterion of maximum strength is not advisable, which makes it possible to optimize cutting modes based on the criteria of productivity and surface quality.