| 摘要 |
<p>A non-developable surface is formed from a fabricated approximation of the required shape, by injecting fluid under press. until the required deformation is obtained; heat may be applied at the same time, partic. with thermoplastic materials. Metal may need annealing before and/or after the pressure is applied. A torus of circular section can thus be formed from one of square section: the latter can be fabricated from two coaxial cylindrical sleeves joined top and bottom by circular rings. A sphere can be formed from a surface of revolution whose cross section is an octagon; this surface is composed of a cylinder, two conical frusta and two circular discs. If a sheet of uniform thickness is used, a sphere results when press. is applied; if the circular discs are thicker than the rest, the surface becomes ellipsoidal.</p> |
