HEAT DEVELOPED IN FORGING.


M. Tresca has lately presented to the Academy of Sciences some very
interesting experiments on the development and distribution of heat
produced by a blow of the steam hammer in the process of forging. The
method used was as follows: The bar was carefully polished on both
sides, and this polished part covered with a thin layer of wax. It was
then placed on an anvil and struck by a monkey of known weight, P,
falling from a height, H. The faces of the monkey and anvil were exactly
alike, and care was taken that the whole work, T = PH, should be
expended upon the bar. A single blow was enough to melt the wax over a
certain zone; and this indicated clearly how much of the lateral faces
had been raised by the shock to the temperature of melting wax. The form
of this melted part could be made to differ considerably, but
approximated to that of an equilateral hyperbola. Let A be the area of
this zone, b the width of the bar, d the density, C the heat capacity,
and t-t0 the excess of temperature of melting wax over the temperature
of the air. Then, assuming that the area, A, is the base of a horizontal
prism, which is everywhere heated to the temperature, t, the heating
effect produced will be expressed by

Ab x d x C(t-t0)

Multiplying this by 425, or Joule's equivalent for the metrical system,
the energy developed in heat is given by

T1 = 425 AbdC(t-t0).