Non-Flying Report 6 Apr 24. The Palmgren-Miner Rule and Cake
It was evident from the forecast and Storm Kathleen that it was going to be a “no-fly” day and so it proved.
However, that did not deter those who dutifully reported to Hangar 4 and remained to undertake some essential admin on the aircraft fleet and also to learn more from Deputy Dear Leader Nigella about the fascinating Palmgren-Miner Rule, something wot Nigella knows a lot about.
In 1945, Milton A. Miner popularised a rule that had first been proposed by Arvid Palmgren in 1924. The rule, variously called Miner's rule or the Palmgren–Miner linear damage hypothesis, states that where there are k different stress magnitudes in a spectrum, Si (1 ≤ i ≤ k), each contributing ni(Si) cycles, then if Ni(Si) is the number of cycles to failure of a constant stress reversal Si (determined by uni-axial fatigue tests), failure occurs when:
Usually, for design purposes, C is assumed to be 1. This can be thought of as assessing what proportion of life is consumed by a linear combination of stress reversals at varying magnitudes.
All super stuff. Then we learnt about aero-elasticity regarding aircraft structures - the phenomena that emerge due to the interaction of aerodynamic (in particular unsteady), inertial, and elastic forces emerging during the relative movement of a fluid (air) and a flexible body (aircraft).
At some stage it was noted that a three club members had quietly slipped off, one to eat cake, thoughtfully provided this week by Rob……..
……and two had gone to play darts in the club room.
Back to business. Under Nigella’s careful direction we then set about weighing R35 (apparently it is something you have to do now and then to see how many more pies you can fit in the cockpit) and then measuring how long it is to find out if it’s got any shorter since last year.
You then bodge some cool sums that tell you that R35 is safe to fly for another year!
It got all too much for Will who wished he gone off to play darts when he thought that Nigella was going to launch into his famous lecture on the wing root bending moment (WRBM).
We’ve got to find someone else to do the Blog 😍
