Effect of Bubble Inclusions on the Mechanical Properties of Cast Poly-Methyl Metacrylate

Bubble inclusions present in cast acrylic plastic generally degrade the mechanical properties of the material. To evaluate the effect of bubbles on the mechanical strength of acrylic plastic, 120 tensile and compressive test specimens were machined from massive acrylic castings with bubble inclusions. The specimens were tested under uniaxial loading condition and effect of bubbles on tensile and compressive strength noted. The stress raiser effect of bubbles caused the tensile specimens to fail at stresses 7 to 30 percent lower than observed in specimens without bubbles. The compressive yield strength was not affected by bubbles. However, here the bubbles served as stress raisers also and caused cracks to initiate at the bubble surfaces when the yield strength of acrylic plastic was reached.

Induced Flow Reciprocating Pump Theory Supported by New Performance Data

Reciprocating pumps have been employed in conjunction with air vessels and fluid accumulators for a long time in order to reduce maximum cylinder pressures and energy wastage in friction. More recently, diaphragm pumps, run at high speed, have been built utilizing a hydraulic accumulator or capacitance in conjunction with a hydraulic inductance, in order to greatly increase the flow output. Volumetric efficiencies of over 250 percent have been obtained. The present paper describes briefly this induced flow principle and then compares theoretical solutions with experimental measurements taken in the first commercially available pump of this type.

Differential Pressure Transmitters, Span-Shift Errors With Static Pressure

The author reviews methods of calibrating low-differential (25–300 in. H2O) D.P. transmitters at high (up to 3000 psig) static pressure. Various test methods are described along with discussion of their merits. Included are use of one or more deadweight testers (gas or liquid) and use of a high-pressure mercury manometer as a standard. Five D.P. transmitters of different construction are tested and their static span-shift performance reported.

A Photographic Study of Spark-Induced Cavitation Bubble Collapse

The collapse of spark-induced cavitation bubbles in a flowing system was studied by means of high speed photography. The migration of cavitation bubbles toward a nearby solid boundary during collapse and rebound was observed. Near its minimum volume the bubble typically formed a high speed microjet, which struck the nearby surface causing individual damage craters on soft aluminum.

Drag Reduction by Ejecting Additive Solutions Into Pure-Water Boundary Layer

Drag reduction caused by ejecting additive solutions from a slot into a pure-water boundary layer on a flat plate has been systematically studied. Results include drag measurements for a plane boundary, smooth and rough, with various openings of the slot and with various concentrations and discharges of the ejected additive solution. Conclusions have been drawn on the additive requirement in external flows and on the ejection technique for an optimum drag reduction.

Forced-Convection Mass Transfer From Wetted Grooves

A wetted-wall column was used to measure liquid flow rates in capillary grooves on vertical surfaces. The test facility contained interchangeable grooved surfaces (2-in. OD) which contacted a liquid reservoir in such a way that the test surfaces were partially wetted by capillary action. The wetted portion was exposed to a forced-convection air stream, so that surface evaporation took place because of the different partial pressures of the vapor at the liquid-vapor interface and at the center of the air stream. All data were obtained in steady-state and nearly isothermal conditions. Experimental results with carbon tetrachloride on brass surfaces were in agreement with approximate predictions, which were computed for evaporative heat transfer and then related to mass transfer by using Reynolds analogy for pipe flow.