| Manitoba Hydro is Canada's largest hydro utility company currently owning fourteen hydropower-generating stations with a total capacity of over 7500 MW. Both emergency intake gates and spillway gates are used in each. Currently, design guidelines for gate wheels and roller paths do not consider the fatigue life of these elements. It is this lack of knowledge in the structural performance of gate wheels, which constitutes the basis of the present research investigation.;A finite element (FE) analysis was conducted on a three-dimensional contact stress model of a roller and a plate using the ANSYSRTM finite element program. The stress-based multi-axial theory was used to assess the fatigue life of rollers and roller paths. Very high strains were observed in Roller R1, whereas, much lower strains were found in Rollers R2 and R3 as compared to Roller R1. Likewise, high strains were observed in Plates P1 and P2, whereas, lower strains were found in Plates P3-P6. Large visible cracks were observed in Roller R1 and in Plates P1 and P2, whereas, no sign of any crack or damage was observed in Rollers R2 and R3 and in Plates P3-P6. Plates P1 and P2 exhibited a maximum indentation of 1.48 mm and 1.21 mm, respectively, after one million and 0.82 million cycles, while the stainless steel heat-treated plates suffered a much smaller surface indentation, which ranged from 0.02 mm to 0.12 mm after 400,000 cycles. The test results demonstrated that the cast iron wheel and Plates P1 and P2 performed very poorly under fatigue loading while high carbon steel Rollers R2 and R3 performed extremely well.;The FE results indicated that high stress values in contact areas, both in rollers and in plates, were critical. The maximum values of all types of stresses were found in these zones. The trend of stresses found in the contact area of roller and plate were consistent with those found in the literature. Laboratory test results and FE results were in good agreement.;The fatigue lives of Roller R1 and Plates P1 and P2, under the influence of both normal and tangential forces, was half a million cycles. The fatigue lives of Rollers R2 and R 3 and Plates P3-P6 were very high as compared to those of Roller R1 and Plate P1. Laboratory test results, visual inspection and SEM results of rollers and plates supported the fatigue analysis results. High principal compressive and tensile contact stresses under the influence of both normal and tangential forces, evidenced by both FE results and literature review, were the main cause of fatigue failure of roller and plate. High contact stresses are fatal to the fatigue life of rollers and plates. (Abstract shortened by UMI.);An experimental investigation was carried out at the University of Manitoba in Winnipeg, Canada, which involved the testing of three wheels and six plates under cyclic loading. One of the wheels, R1, was made of cast iron while the other two wheels, R2 and R3, were made of high carbon steel. The material in two of the roller path plates, P1 and P2, was medium carbon steel with no heat treatment. The material in the other four plates P3 to P6, was heat-treated stainless steel. Eight cyclic tests were conducted, two on each of Rollers R1 and R2 and four on Roller R3. The wheels were subjected to radial compressive loads of approximately 753 kN to 903 kN that remained fairly constant while the wheels were "rolled" over the roller paths for a number of cycles that also varied from 200,000 to a million cycles. At the end of each cyclic test, the test setup was dismantled and indentation profiles were measured in roller paths. Scanning electron microscope tests were also conducted on all specimens to measure the extent of damage in specimens. |
