Seminar Series - 1996-1997

Date:  Tuesday, April 22, 1997
Time:  3:30 p.m.
Place:  306 Bancroft Hall

Effects of Shear Deformation on Orthotropic Cylindrical Beams

Orthotropic cylindrical beams are used in industry in a variety of applications, i.e., rollers, shafts etc. In these cases, care and attention is paid to beam deflection and natural frequencies. Typical analysis does not include the effects of shear deformation. The proposed analysis will attempt to demonstrate that including shear deformation will result in greater predicted deflection and lower natural frequencies. These results will then be compared against known data and solutions to test validity. The problem approach involves the development of equations of motion, strain displacement relationships, and constitutive relationships. To ensure ellipticity of the problem, the orthotropic constitutive matrix must be verified to be positive definite. Extensive code development and problem bench marking against known solutions will be used to verify results. 
 

Electrospinning of a Dielectric Viscous Fluid

A general hydrodynamic model of electrospinning of a charged fluid is developed for the first time. The model incorporates effects of electric forces, pondermotive forces, viscous forces, and surface tension. The following problems are considered: formation of meniscus, jet initiation, and stationary spinning of a charged dielectric viscous fluid in the elctric field. Existence of a stable Taylor cone is analyzed. An expression for the maximum radius of a stable jet is obtained. The results corroborate well with the experimental data available. 
 

Processing Flaws in PZT Transducer Rings

The microstructures and the chemical composition of semi-finished PZT transducer rings at various stages of fabrication have been studied by SEM and EDS in order to understand the causes of failure of the PZT rings. SEM observation shows that large pores with lenticular shape formed initially in the PZT rings at the stage of cold-pressing and microcracking took place around the pores during poling, the final stage of fabrication in which a strong DC electric field is applied. Microcracks were found in connections with sharp cusps formed by two grains at the edge of large pores, and the microcracking mode shows, to some certain extent, correlation with grain size, i.e., intergranular with small grains and transgranular with large grains. In addition, our EDS reveals imhomogeneous distribution of constituted elements, i.e., Pb, Ti and Zr, in the assintering PZT rings. Evaporation of PbO and formation of a liquid phase, which is rich in Ti, might be the causes of the inhomogeneity. 
 

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