>According to Youngs paper of 1952 the Modulus divided by the >density of the string results in a consant (25.5*10^10th). It >appears to me that this constant is supposed to be the same >regardless of material, which would mean that E is the product of D >* this constant. Ric, Young's modulus is not an easy parameter to determine experimentally. Using bulk tensile testing, even with fancy equipment, you can't get a very accurate value, partly because real materials never behave completely linearly (even steel wire). There are additional complications that make tensile testing of wire a very difficult experimental procedure, adding to the inaccuracies in determining the modulus for a wire specimen. It is primarily a material dependent property, but can be affected to some extent by mechanical working (and heat treatments). Consequently, a small range of moduli will be relevant for a given material according to how it has been physcially processed. Accurate measurement of Young's modulus can be done by sonic and similar techniques which measure the vibrations of the metallurgical structure at the atomic level. All are involved and generally expensive. There is no general correlation between density and modulus. Compare brass, denser but the modulus is considerably lower than that of steel. >In any case it seems to me that there is some significant amount >of confusion surrounding Young Modulus and it perhaps is more >important in a practical scaleing sense then we assume. It has little practical use for scaling since it is not a controllable factor in wire manufacture. It is essentially determined by the choice of material. >This fits well with your call to empirical testing for breaking strength / %'s The only way to determine the capabilities of your wire is with tensile testing. Stephen -- Stephen Birkett http://real.uwaterloo.ca/~sbirkett
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