Adhesive Fracture of Bonded Plate or Membrane Strips

One of the few exact non-linear solutions applying to adhesive debonding is for the deformations in a pressurized thin plate strip of infinite length subjected over its span to externally applied pressure and temperature. For example, if the ends of the span are clamped (bonded) to a substratum leaving an unbonded span to be loaded by pressure or temperature, critical values of these latter quantities, at which debonding may occur, can be calculated using an energy balance criterion. To date, only the limiting cases of the general thin plate solution have been used to deduce these critical pressure or temperature loadings: (1) the plate thickness to span ratio is sufficiently large that nearly all the strain energy is in bending, i.e., the “thick plate” case, and (2) the opposite case wherein the ratio is sufficiently small that mainly stretching energy is involved, i.e., the “membrane”. This last case, for example, has applications to the adhesion of paints and coatings. The purpose of this paper is to present the results of calculations for pressure criticality over the range of all plate thickness between the aforementioned two previously available limiting cases.     

The Superconductive Critical Magnetic Field of Beryllium

We have measured the temperature dependence of the superconductive critical magnetic field of three samples of beryllium from three different sources. The irregular geometric shape of one sample prevented a complete analysis of the data, but the data for the other two samples were well represented by the BCS model of superconductivity. The values of T _c and H _c (0) are found to be sample dependent. For the purest sample studied, T _c =24.34±0.02 mK, H _c (0)=107.7±0.2 T and (/V)=32.9±0.3 J/cm³ K². By a very small extrapolation of the data as a function of purity, it is inferred that the critical parameters for pure Be are: T _c =24.38±0.02 mK, H _c (0)=107.9 T±0.2 T and (/V)=33.0±0.3 J/cm³ K².