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Stagnation temperature probes with single platinum or gold coated shields made of silica (or other material of low thermal conductivity) were built for use at high supersonic speeds and elevated temperatures. For free-stream Reynolds numbers of the order of 40,000 the temperature recovery factor of the probes reaches .996. It decreases with decreasing Reynolds number and increasing temperature. At temperatures up to 8000 K the major thermometric losses of the probes are conduction losses. A single calibration curve is obtained for each probe by relating the calibration data to the flow conditions inside the probe. This calibration curve facilitates the evaluation of flow data from measured pressure and temperature data alone without resorting to any assumptions. Small probes of 1 mm height at tho air entrance wore successfully used for temperature surveys of turbulent boundary layers on the nozzle wall of the. hyporsonic tunnel.

The Goodrich block fatigue test is commonly used to determine the (compression) fatigue behavior of tire cord in rubber. An investigation has been conducted into the origin of the loss of cord strength under different load conditions and at different running times. To this end the retained strengths and the force-strain curves of the fatigued cords were measured. The location of the cord fractures and a SEM analysis provided valuable extra information about the fatigue mechanism. The strength loss of the cords appeared to be mainly caused by the strength loss of the filaments. Changes in cord geometry and filament interaction occurring during the fatigue process play no or a very small role in the loss of cord strength. Depending on the load, the filaments show bending, tension-tension, and fretting fatigue damage. The severest fatigue load seems to be high tension combined with a certain amount of compression. Principle of the GBF TestThe Goodrich block fatigue (GBF) test is used by both tire and tire cord manufacturers to determine the (compression) fatigue behavior of tire cord in rubber. The cords are embedded in rubber blocks (Figure 1 ), which are clamped at the circumference of two synchronously rotating discs (Figure 2). If one disc is canted relative to the other, the rubber-cord specimens are loaded cyclically in compression and extension. Adjusting the angle and distance between the two discs provides the desired amount of compression and extension. After a specified number of cycles, the rubber is removed from the cords, which are subsequently tested for retained strength. , 1 FIGURE 1. Schematic drawing of the GBF specimen.FIGURE 2. Principk of the GBF tester (the deformation of the specimen is exageertted)Although the GBF test is described in ASTM D885-62T, it is by no means fully standardized. The construction and dimensions of the specimen and the test conditions vary with each user, those used within Akzo are described in detail in reference 13. OBJECTIVEIn general, the GBF test provides an impression of the (compression) fatigue behavior of the tire cord and permits prediction of the fatigue behavior of the cord in the tire. To improve the fatigue resistance of the cords and predict their fatigue behavior in the tire with sufficient accuracy, it is necessary to understand the

Naturally turbulent boundary layers on a cooled flat plate have been investigated at several distances from the leading edge of the plate at a Mach number of 5.2 for three rates of steady-state heat transfer to the surface. Measurements of Pitot and static pressures and of total and wall temperatures made it possible to compute velocity profiles, static-temperature profiles, and boundary-layer parameters without resorting to assumptions. The data demonstrate that the Reynolds analogy between skin friction and heat transfer is valid for all conditions of the present experiments. With increasing rate of heat transfer to the surface, the skin-friction coefficient was found to decrease, a phenomenon opposite to that predicted by theories and empirical relations. On the basis of the present data and other published results of compressible and incompressible turbulent boundary-layer skin friction, a simple relation was devised which describes closely the variation of the skin-friction coefficient with Mach number, heat-transfer rate, and momentum-thickness Reynolds number.