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https://resolver.caltech.edu/CaltechETD:etd-05232003-090926
Authors: Hudson, Donald Ellis
Year: 1942
DOI: 10.7907/Z2V9-C551
<p>(1) The mean damping capacity of steel over a stress range of several hundred pounds per square inch is a physical property of the material, the value of which can be checked accurately by successive tests on the same specimen, with the apparatus and method developed in the course of this investigation.</p>
<p>(2) The results of the damping capacity test can be duplicated accurately for successive specimens of the same material.</p>
<p>(3) There is a strong possibility that although the general trend of the stress-damping capacity relationship may follow a simple law, the true relationship for a material such as steel is extremely complex and somewhat erratic.</p>
<p>(4) The stress-damping capacity relationship indicates that for steel the damping does not follow the viscous friction law, although for low stresses the assumption of constant damping would not be far in error. In the case of brass, the internal friction was practically independent of stress for the stress range covered in the tests.</p>
<p>(5) The damping capacity of the specimens tested was found to be a function of the maximum torsional stress set up in the specimen rather than a function of the maximum shear stress or of the maximum normal stress.</p>
<p>(6) In the case of materials whose damping capacity decreases with decreasing stress, the apparent damping capacity measured from a solid test specimen is lower than the true specific damping capacity of the material.</p>https://thesis.library.caltech.edu/id/eprint/1966Dynamic Effects on the Gas Exchange Process in Two Stroke Cycle Engines
https://resolver.caltech.edu/CaltechETD:etd-05132003-163847
Authors: Kyropoulos, Peter Rudolf
Year: 1948
DOI: 10.7907/EDNA-1J88
Recent investigations of fuel injection in spark ignition engines have aroused new interest in two stroke cycle engines. The performance of such engines is very much affected by the dynamic behaviour of the fresh air introduced and the exhaust leaving the cylinder through ports, receivers and silencers. The present investigation has as its aim the clarification and establishment of trends in the performance of two stroke engines with particular reference to crank case scavenged engines.
The basic relations governing the flow of air and gas through the whole system are investigated one by one and their interdependence is established. The investigation covers: pulsations in the cylinder, accelerations in the ducts, effect of variable port area, effect of throttling in the ports. The basic differential equation for free oscillation of the exhaust gas in the system comprising receiver, exhaust pipe, and silencer is set up and a method is developed which allows calculation of an equivalent length for the system. With this equivalent length, the natural frequency of the system can be calculated.
An experimental investigation is presented which was carried out on a single cylinder compression ignition engine with crank case scavenging. The volumetric efficiency of the engine was determined as a function of exhaust system configuration at various brake mean effective pressures and at constant engine speed. The pressure in the exhaust near the port was measured (by means of a quartz and crystal pickup) as a function of crank angle.
The results are presented in the form of plots of volumetric efficiencies as function of brake mean effective pressure for various configurations and as photographic records of pressure as a function of crank angle.
It is concluded that a simple frequency analysis is insufficient for the determination of the exhaust behaviour. Criteria for good exhaust systems are established. The trends predicted in the theoretical analysis of the report are, in general, well verified.
The need for further investigation is indicated and an outline of research is presented.https://thesis.library.caltech.edu/id/eprint/1767The Anemometric Application of an Electrical Glow Discharge in Transverse Air Streams
https://resolver.caltech.edu/CaltechETD:etd-11032003-110318
Authors: Mettler, Ruben Fred
Year: 1949
DOI: 10.7907/RTBA-4692
The possibility of using an electrical glow discharge for quantitative turbulence measurements is experimentally investigated. It is found that a glow discharge is stable in a transverse air stream throughout the subsonic velocity range, and at supersonic air velocities up to a Mach number of 1.5, with no indication that this Mach number represents an upper velocity limit. A calibration procedure is developed and used in measuring the decay of turbulence behind a grid at low subsonic velocities. Comparison with decay measurements made independently with a hot wire anemometer under similar flow conditions shows that the glow discharge data is as yet quite badly scattered and somewhat inconsistent.
A quantitative theory of the dark current anemometer is presented and gives results which agree in form with reported experimental results. A qualitative theory of the mechanism of the glow discharge anemometer and the first steps of the corresponding quantitative analysis are also presented.https://thesis.library.caltech.edu/id/eprint/4383The Influence of Metal Grain Structure on the Attenuation of an Ultrasonic Acoustic Wave
https://resolver.caltech.edu/CaltechETD:etd-01052007-131306
Authors: Roney, Robert Kenneth
Year: 1950
DOI: 10.7907/V3FK-SM37
Apparatus is described for the study of the propagation of ultrasonic acoustic waves in solid bodies and its applications in metallurgy. In particular, the anisotropy of attenuation in cold worked aluminum and the effect of anneal are demonstrated. Reflections from individual crystal faces are identifiable in bodies with average grain diameter of 0.17 mm. A critical discussion is given of a theoretical effect of grain size on wave attenuation as advanced by Mason and McSkimin(9), and an empirical relation reported by Roth(7). The theory is extended to cover the complete range from that explored by Mason to that reported by Roth. Experimental deviation from the theoretical effect indicates other factors besides average grain size are effective in materials with asymmetrical grain structure.https://thesis.library.caltech.edu/id/eprint/37