Hydraulic Grips and Controller for Variable Amplitude Fatigue Testing of Structural Connections, Interfaces, and Cables

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Fatigue deterioration under cyclic loading is well known to have a major, negative impact on the safety of engineered structures, the societal cost of infrastructure maintenance, and the weight and energy efficiency of machinery, vehicles, and other mechanical systems. As new materials, systems, and connection technologies emerge, it is critical that they be researched and developed with a clear understanding of their fatigue behaviour and how to improve this behaviour in order to maximize performance, safety, and economy. While the problem of fatigue deterioration presents a challenge in the development of these technologies, the need for this research from a societal perspective has never been more pressing, as progress in this area is seen as the key to the development of “greener” and more economically sustainable buildings, urban infrastructure, and transportation / energy systems in the coming decades. Against this background, the co-applicants of this proposal are currently overseeing world-class research programs investigating: new connection concepts for rapidly constructible / easily reconfigurable urban infrastructure systems, new welding technologies for lightweight metal structures, new cable connection solutions for long span bridges, and the performance assessment of welded connections in piping systems used by the energy sector. The current proposal requests funds for components of an experimental fatigue testing frame, which would allow Waterloo researchers to expand the breadth and substantially intensify the pace of this world-leading research. The requested equipment includes: 1) one set of hydraulic grips (along with two sets of inserts) compatible with one of our existing 100 kN fatigue testing frames, and 2) a modern digital controller capable of introducing complex VA loading histories at high frequency to enable rapid fatigue testing. Without this equipment, the progress of the research planned by the applicants will be critically handicapped due to the current high utilization rate of the somewhat comparable test frames at Waterloo and elsewhere for other purposes. The proposal to repurpose an existing 1970s vintage test frame with a new digital controller and a safer and more application-suitable grip set is innovative and will result in a high cost savings by extending the service life of the working parts of an existing 100 kN test frame, which would otherwise be underutilized and (in fact) unsafe to keep in operation. The resulting testing system will be heavily utilized by high numbers of HQP, with minimal demand on the limited available technician support. It will be highly versatile and reconfigurable as needs change, with an expected life of 15-20 years or more. The results of the enabled research will lead to substantial societal benefits in terms of reduced infrastructure-related energy consumption and life-cycle operation and maintenance costs.