THE TUBE STRESS-STRAIN PROPERTIES OF BRITTLE MATERIALS TO 5000 F. Sixth Monthly Report

Additional furnace work using the 25-kw induction power supply indicated reliable long-time performance at 4500 deg F. The detailed check out of the prototype, flat, gas bearing was completed. Bearing operatlon was very stable at 0.0005-in. gap. The design of the spherical bearing was begun. The grips were checked with a single graphite specimen and indicated satisfactory performance with specimen failure at the anticipated ultimate stress. The loading system was assembled, aligned, and operational check out completed. Design study of the optical strain analyzer was continued. (auth

THE TRUE STRESS-STRAIN PROPERTIES OF BRITTLE MATERIALS TO 5000F. Tenth Monthly Report

Runs on the zirconia-coated graphite established that the ultimate strength of this material is 30 to 100% greater than previously reported. This greater strength was apparently obtained because the gas bearings eliminate all bending moments in the specimens and the radiant heating provides more even and measurable temperatures. The ultimate strength of one pyrolytic graphite specimen was found to be over 33,600 psi at 4000 deg F. The performance of the resistance-heated furnace was very satisfactory. The gas bearings were dismounted, cleaned, plated, and are being reinstalled. Some limit switches were added to the load frame to provide protection from overtravel. (auth

THE TRUE STRESS-STRAIN PROPERTIES OF BRITTLE MATERIALS TO 5000F. Tenth Monthly Report

Runs on the zirconia-coated graphite established that the ultimate strength of this material is 30 to 100% greater than previously reported. This greater strength was apparently obtained because the gas bearings eliminate all bending moments in the specimens and the radiant heating provides more even and measurable temperatures. The ultimate strength of one pyrolytic graphite specimen was found to be over 33,600 psi at 4000 deg F. The performance of the resistance-heated furnace was very satisfactory. The gas bearings were dismounted, cleaned, plated, and are being reinstalled. Some limit switches were added to the load frame to provide protection from overtravel. (auth

THE TUBE STRESS-STRAIN PROPERTIES OF BRITTLE MATERIALS TO 5000 F. Sixth Monthly Report

Additional furnace work using the 25-kw induction power supply indicated reliable long-time performance at 4500 deg F. The detailed check out of the prototype, flat, gas bearing was completed. Bearing operatlon was very stable at 0.0005-in. gap. The design of the spherical bearing was begun. The grips were checked with a single graphite specimen and indicated satisfactory performance with specimen failure at the anticipated ultimate stress. The loading system was assembled, aligned, and operational check out completed. Design study of the optical strain analyzer was continued. (auth

DETERMINATION OF THE TRUE STRESS-STRAIN PROPERTIES OF BRITTLE MATERIALS TO 5000 F. Ninth Monthly Report

The development of the system and techniques to permit determination of strains at right angle to the axis of loading in the specimen was continued. An additional optical system was developed to accept the lateral image of the gage points and project a vertical image of the same proportion to the apertures of the strain analyzer. Using a dummy specimen of steel in the load train, the automatic pressure control system for the gas-bearing universals was operated. A fluctuation of gas pressure occurred within the bearings. Multiple progressive fracture planes were observed throughout the gage length of fractured graphite and tungsten. (M.C.G.