Design Analysis and Fabrication of a Tensile Creep Testing Machine

This work covers the design analysis and fabrication of a tensile creep test machine for determining the creep curve for thermoplastic materials (Teflon) and light metals (aluminum, lead) that creep easily. The apparatus consists of four primary systems which are the load application system, the heat generation and control system, the strain measuring system and then the frame and the Specimen grip. The insulating material for the heating chamber is clay and the maximum temperature the chamber can hold is 300°C. The maximum amount of load that would not topple the machine is 2457N and the dial indicator measures a maximum extension of 10 mm with an accuracy of 0.01 mm. Any specimen to be used on the machine must be designed to have a cross sectional end diameter of 16 mm, a gauge length of 65 mm and an overall length of 145 mm. Creep Tests were carried out using Teflon/Polytetrafluoroethylene as the test specimen at a constant load of 0.44MPa and at varying temperatures of 80°C, 100°C and 120°C for a duration of two hours; the results show that at constant load and varying temperature, the elongation increases with time and also the creep rate decreases with time as temperature increases. Secondly, Creep tests were carried out on Teflon/Polytetrafluoroethylene test specimen at a constant temperature of 100°C and at varying stresses of 1 kg, 2 kg and 3 kg for duration of two hours. The results show that at constant temperature and at varying load, the extension and the creep rate increases with time as the load increases. These Creep curves show excellent agreement with experimentally determined data using stress relaxation.