On behalf of and in collaboration with Valmet AB this thesis has been fulfilled and executed at their development department in Sundsvall. Valmet AB design, develop and manufacture machines and equipment for the pulp, paper and energy industry. One of their key products is the TwinRoll press. The TwinRoll press consist, among others, of a part called mantle section which in terms of manufacturing is rather complex. This part itself consists of frame ribs, which during operation endure high loads in a high amount of cycles during its life-span. Due to this, fatigue failure sometimes occurs, which in consequence causes mantle section failure. Theoretical determination of the fatigue strength has been proven difficult, which has created needs for experimental fatigue testing. The goal with the thesis was to define a method for fatigue testing and to design and develop a rig which could perform the testing according to the defined method. The initial part of the project consisted of a literature study about fatigue testing and how it normally is performed. Then the work with the test method started and the loads during normal operation was specified, as well as parameters that might affect the test results. This part was important as the parameters could be transformed into requirements which the test rig needed to satisfy. When the method for testing and the measurable requirements were done, concepts were generated via individual sketching and brainstorming. A final concept was chosen for detailed design in SolidWorks after using methods like voting and Pugh’s concept selection matrix. The rig was modelled and drawings for manufacturing was produced, and then dimensioned through both simulations with FEM and calculations by hand. The final construction was then inspected with VR-technology. The conclusion of the thesis was that the frame ribs should, as a suggestion, be fatigue tested with constant stress amplitudes until failure, and then repeated for other stress values until the amount of generated data is enough for evaluation in a stress-number-diagram. A Wöhler-curve should then be generated for desired probability of failure and finally be evaluated in a Haigh-diagram. The developed test rig will perform testing on one frame rib at a time with a high frequency hydraulic cylinder, were the sample used is a piece of the mantle section. Furthermore, the sample is fixed in both directions to correspond to stress generated by shrinkage which an entire frame rib normally withstands.
| Identifer | oai:union.ndltd.org:UPSALLA1/oai:DiVA.org:uu-353399 |
| Date | January 2018 |
| Creators | Müllback, Rasmus |
| Publisher | Uppsala universitet, Industriell teknik |
| Source Sets | DiVA Archive at Upsalla University |
| Language | Swedish |
| Detected Language | English |
| Type | Student thesis, info:eu-repo/semantics/bachelorThesis, text |
| Format | application/pdf |
| Rights | info:eu-repo/semantics/openAccess |
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