Stephen, It is indeed considered in the metallurgy that the creep of steel is negligible, but in the piano trade, it is a very different story. Experiments have been made, then data exists somewhere. I'll try to translate what have been given to me : Even under the elastic domain, a piano string is subject to a slow deformation with time. The creep begin at 40% of the breaking strain (Krichen = creep in German). The most the temperature and the solicitation, the faster the process ( from usual shop temperature to a hotness like in a hot summer day the effect is accelerated ten times from 23?c to 35?c (or 72F to 95F) The experiments where conducted on a 12 years lasting on tensed strings at different tensions - Klaus Fenner wrote a text in German that describe these '(1978) - have no translation at this date. The results are very clear and well known. While the first creep occur (tension applied) there is a broking of the molecular organization that wake up a counter-force (seems like histeresis to me). This last is changing the strain resistance of the string to the better breaking strain limit is higher). Slowly, with time, the creep disappear totally. The name of the initial effect when a string is first tension applied is the Kosler effect. It have been noticed that a string was sour at first, then ring clearer. This is due (partially) to the performance loss of modulus of elasticity E, that, because of the dislocation counter-force, have its properties back after a few hours, then evolve depending of the creep and the annealing (may be another English word describe better the internal annealing in question ?) . The dislocation phenomena of the steel is said to be essential . The most important part of the loss of the energies provided by the pianist occur in the string and the bridge, and NOT in the soundboard (!) It is suggested that you conduct the experiment yourself if you mark the length of a string (marker, tape) tense a 800 N , measure the elongation and keep it at that tension for 6 months ore one year, then intense and measure it, if no creep should occur, your string should be back to its original length. The arrangement of the molecular dislocation is said to be of primal importance for the internal amortizing of the string (viscous/elasticity) I wanted to say about the 4 kind of strings that are produced by Stephen PAULELLO, that a full methodology will be available, as well as more data on them, in September. The strings are made with a slower anneling time than Roslau blue or red, and that is the main reason for their propreties. On the Mas Cabre 'Pure sound' strings, I've always been told it was only stainless wire that was annealed to commeon sizes, based on the discovering that stainless have the same density than on kind of wire that was current in Europe, Firmini string. Others say me that some other metal is in the mix, but I don't see how a wire maker can obtain special alliages in small quantities from the metallury trade so doubt remains at this time (and i am not found of the tone this wire gives). What type of wire are you planning ? for what era(s). Greetings. Isaac OLEG > > Isaac wrote: > > >This is to obtain the plastic deformation that happens > with time, but > >under the normal elastic limit, and at once. > > Plastic deformation under constant stress with time is creep. Steel > doesn't creep. The likely explanations for "settling" have been > discussed under the separate thread, but time dependent plastic > deformation is not one of them. > > Any plastic deformation that occurs in a piano string after > installing it and bringing it to pitch must be due to a sudden > increase in stress above the existing elastic limit - i.e. > resulting > from a hard blow. Such plastic deformation is essentially > instantaneous. The elastic limit is shifted to the new > higher point. > The same blow after that will not produce additional plastic > deformation in that string. The only influence of time in this > context is "when does the blow that pushes it over the limit occur > after stringing?" > > A well designed scale should keep strings well below the elastic > limit of the wire material being used, so even hard blows will not > result in plastic deformations. >
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