The design and assembly of a compact setup for testing helical springs and bolted joints

Abstract

At the University of Girona, the students of the bachelor of mechanical engineering perform tests on a compression spring and a bolt connection within the context of the course on machine elements. The goal of this master's thesis is to design and realize a compact and interactive device to load these components. After a thorough test phase, the new device was compared with the old one with regard to measuring accuracy and ergonomics. Furthermore, a manual is provided so that the students know how to use the device. The device is capable of applying a compressive force from zero to 1000N onto the spring and a tensile force from zero to 5000N on the whether or not preloaded bolt connection. The device is manually driven. Furthermore, the applied force is measurable with an accuracy of at least 5% and the compression of the spring with an accuracy of at least 0.5 mm. The device is not larger than 800mm x 350mm x 350mm. Finally, the device is considerably more ergonomic in use than the old device. After a thorough study of the problem, a division was made into subproblems. The best solution was always chosen by means of a SWOT analysis. The total was then elaborated in a 3D design by the means of the design package 'PTC CREO'. The force on the components is applied by means of a trapezium lead thread in combination with an "anti-backlash" nut. In order to obtain a controllable, effortless movement a worm wheel transmission has been chosen.