Desenvolvimento de uma máquina para ensaio de fadiga por flexão

Abstract

Knowledge regarding the properties of materials is of utmost importance for engineering applications. Chemical, physical and mechanical properties of material vary from one to another and due to these differences, it is possible to take advantage of the current technology and well-being. The study of these properties is necessary for the development of new equipment or products and an important property is the fatigue resistance of materials used for manufacturing of components which will be subjected to cyclic loads because fatigue failure can occur unexpectedly. The goal of this work is to design and build a machine for bending fatigue testing to be used in the study of the behavior of metallic materials found in flat geometry, common in several machining processes, allowing the study of fatigue resistance by varying the parameter of milling, for example. Machine design has been split in two large groups named structural and dynamic, consisting of parts and accessories with the aim of, together, performing fatigue tests. As distinct bending fatigue test standards require specimens with varied dimensions, the machine was built in order to enable testing of specimens with different sizes and shapes. AISI 1020 and AISI 1045 steels were predominantly employed in the manufacture of the machine, however, polymeric materials were occasionally used for specific purposes. An electronic circuit consisting basically of an Arduino microcontroller, an encoder, a photodetector and an interruption sensor was developed and built to count the number of cycles and halt the test immediately after specimen fracture. Machine validation tests were performed using eight annealed AISI 1020 steel specimens and indicated that the machine presents satisfactory performance, thus allowing to collect reliable data for plotting Wöhler curve.