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G'day All,
Please refer to the attached document for information regarding a research project I'm currently undertaking. I need to spread the word as far as possible so feel free to link-to or post the document wherever you think a set of gyro-oriented eyes may see it...
Cheers
Gdday Steve,
It is a very good analysis studies on the failure mode of the gyro's hub bar. If I may suggest that you may want to include a 'fitness for purpose" studies by employing *CTOD (crack tip opening displacement) test to determine traditionally used aluminium alloy (6061T3) material for its fracture toughness properties subjected to dynamic loadings. A reverse failure mode studies (your intention) on the failed hub bars will yield result on the type of failure mode such as brittle fracture or ductile fracture.
It is common to see the fracture (crack openings) occurs at the bolt holes but nonetheless also occur adjacent on the lead or trail edge of the hub bar where the actual parent material is.
*CTOD determine the fracture mechanics properties of ductile materials and can be thought of as the simulated opening of a pre-existing fatigue crack prior to fracture.
This type of test is gaining popularity in the oil & gas industries to predetermine failure before it actually happen.
Cheers
Lou
G'day Lou,
Thanks for your interest in my project, and I appreciate your suggestion regarding CTOD - I recall briefly brushing over the topic in a structural mechanics subject last year, but I'll go back and do some more reading on it.
Indeed as part of my project I am intending to look at the suitability of current hub-bar designs, with the ultimate aim of determing a fatigue life, most likely with an S-N curve method. As part of this I will be looking very carefully at the comparison between Al 6061 and alternative materials. The challenges that lie with this are accurately modeling the loads a hub-bar experiences, and encompassing the varying designs of hub-bars that are currently in use. Ideally I will be able to establish a model whereby basic hub-bar parameters (i.e. length, width, thickness, pre-cone angle etc.), and operational parameters such as AUW, GAG cycles etc. can be entered in to return a fatigue life for that particular scenario.
I've also been doing some reading on rotary wing component usage-monitoring and am excited by the idea of self-contained units encompassing a strain gauge, microprocessor and numerical display that can be applied directly to a component, and based on the loads the component experiences, a percentage value of component life remaining is displayed. This is likely beyond the scope of this particular project, but one of the reasons I chose this topic is that it's an area I can continue to dabble with well beyond my graduating from uni, so who knows, you may see me on New Inventors in a few years with a gyroplane hub-bar usage-monitor...;)
I might take this opportunity to put out the word that I'm very interested in hearing about any research people know of, or may have conducted themselves, even if it's as simple as, say, reading up on material properties. Even if you have a mere hunch as to what could be a major issue, please feel free to let me know....