Re-evaluating the Main Beam Design of Metso Crane Grab Type Model 2
Wallenius, Eero (2024)
Wallenius, Eero
2024
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Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi:amk-2024051010627
https://urn.fi/URN:NBN:fi:amk-2024051010627
Tiivistelmä
The possibilities for improving the design of Metso Crane Grab Type Model 2 main beam are investigated through analysis of material properties, manufacturing procedures as well as strength calculations, simulations, and fatigue and buckling analysis. The existing design was carefully examined to find unnecessary features that could be removed, or any features that complicate the manufacturing of the beam that could be improved. Alternative materials and beam profiles were examined to find the best possible solution for the purpose. Three beam profiles and material alternatives were selected for comparison. The external load carried by the machine was set to 91.2 kN and, with this load, the maximum internal moment was found to be 36158500 N∙mm and maximum shear force 37.2 kN. The IPE 400 beam exhibited the lowest bending stress value of 31.3 MPa and the highest value was found in the current beam design with an RHS 200 x 400 mm beam profile with a 6 mm wall thickness at 49.9 MPa. The IPE 400 beam, with 1.0577 structural steel as material, also showed the lowest deflection value of -1.243 mm whereas the current design had a value of -1.692 mm. The section modulus calculations showed that, in terms of bending, smaller beam profiles could be applicable. The most suitable material, of the materials selected for comparison, was found to be 1.4404 stainless steel as it had sufficient strength properties and best corrosion resistance in sulfuric acid conditions. In terms of manufacturing cost, the cheapest beam option was the 1.0577 structural steel beam with the IPE 400 profile and the current design was found to be the most expensive alternative. The availability of acid resistant steels in the desired profiles was found to be limited especially for the required length. A fatigue analysis of a butt-welded joint in the middle of the beam, in the case of the 6mm wall RHS profile, was conducted. The number of cycles for the analysis was set to 1500000, with each cycle consisting of lowering the machine to the cell and lifting the cathode plates. The stress range during the cycle was found to be 53.8 MPa and the limit design stress range 53.6 MPa, indicating a non-safe design. To overcome this, the wall thickness should be increased to 8 mm. Another option would be to use two butt-joints in the beam in areas with a lower stress range. The buckling analysis showed that no web or lateral torsional buckling in the IPE 400 beam would occur.