The problem of tube collapse by external pressure has been investigated experimentally. A graphical solution developed to simplify inelastic collapse design problems was shown to agree with the test results. The von Karman reduced modulus was used in the graphical solution to correct for the stress redistribution caused by yielding. The effects of the geometric imperfections of ovality and wall thickness variations on collapse pressure were shown to be related to the stress-strain behavior of the material. The concept of a critical time'' was discussed in regard to creep-buckling phenomenon. (auth)

Graphite expands linearly with irradiation at temperatures below 250 deg C and develops stored energy of the lattice because of interstitial and vacancy defects. Radiation changes such as stored energy and dimensional expansions can be removed by thermal annealing in which the graphite is removed from the radiation field and heated to a temperature above the irradiation temperature. The thermal annealing of irradiated graphites shows that the greater the irradiation dose, the greater is the recovery obtained at a given temperature. In periodically irradiated graphites, the 200 deg C stored energy no longer increases as it does in continuously irradiated graphites. Thermal annealing not only removes radiation damage but redistributes and creates it. (H.G.G.)