Concept design of a multipurpose fatigue testing rig for spreader components

Abstract: As one of the world leaders in crane spreaders, Bromma Conquip has a high reputation for reliable, high performing crane spreaders. Their success has largely been due to their emphasis on finite element analysis (FEA) during the development of their spreaders. In order to further improve their spreaders as well as verifying their FEA, they have a desire to perform more real testing on certain spreader components. This desire evolved in to a master thesis project where the task was to design and dimension a fatigue testing rig, which could perform fatigue testing on three selected spreader components.The focus of the thesis was on the design and dimensioning of the main steel structure of the fatigue testing rig and the fixation tools for the three selected spreader components. Limitations were made so that the hydraulic system and control system for the test rig would not be covered in this thesis.The thesis is founded on an information retrieval where important aspects concerning fatigue are established and where different types of standardized fatigue testing machines are studied. To gain further knowledge about component fatigue testing, several study visits where carried at the fatigue testing laboratories within bigger Swedish manufacturing companies, from which vital information concerning the structure of a test rig as well as test setup and test procedure was retrieved.Several different concepts for the test rig were generated during a brainstorming session, where all the aspects from the information retrieval were taken into consideration. With the use of Pugh matrix, a concept based on gas cut steel plates that mounts together with bolted joints was selected. Its modular design and the ease of manufacturing made it score well above the other concepts. Initial tests of the concept’s revealed that the geometry of the test rig needed to be changed, due to stress concentrations and geometric constraints.The design of the final concept was made simultaneously as the design the fixation tools, in order to ensure that all the interfaces matched up. To reduce the stress on the test rig, one of the fixation tools was designed basically as an independent load bearing structure within itself. The final dimensioning of the test rig shows that it could withstand an equivalent stress of 48 MPa, twice the stress that it is subjected to.