The ability to produce precision ring shaped parts using the turning process depends significantly on the workholding characteristics. Workholding parameters such as the number of jaws and chucking force are known to influence the roundness tolerance of ring shaped parts commonly used in bearing applications. Experimental trial and error methods are often used in practice to optimize the workholding parameters to achieve the desired part quality. This thesis develops a systematic mathematical approach for optimizing these parameters using a finished cut roundness prediction model and a model for determining the reaction force between the chuck jaws and the ring. The roundness prediction model is verified through experiments for different cutting conditions. The optimization approach takes as input the required roundness tolerance, geometry and mechanical properties of the ring, cutting forces, and the coefficient of friction between the jaws and the ring. The output consists of the minimum number of jaws and the range of acceptable chucking forces that satisfy the required tolerance while preventing slip of the ring. Simulation examples are used to illustrate the proposed workholding optimization approach for a hard turning application. In addition, based on the optimization model, the thesis proposes a novel concept of dynamic chucking force control that promises to yield part roundness that is superior to conventional chucking.

In this thesis, we have analyzed the coupling gap dependent micro-ring loss in a single ring all-pass filter configuration using the two dimension (2D) finite difference time domain (FDTD) and EIM (effective index method). We utilized a new analysis scheme by calculating the transmission signal as a function of input wavelength and fitting the transmission spectrum with a phenomenological ring loss parameter. This novel scheme circumvents the complex waveguide mode analysis process, when the coupling gap is narrow and the all-pass coupling region becomes multi-mode. We first find that the radiation loss increases rapidly with decreasing coupling gap width. Our results show that the intrinsic bending losses of silicon micro-rings (on oxide) with the radius of 1.5 £gm, 2.5£gm, and 5£gm are about 20 dB/cm, 3 dB/cm, 1 dB/cm for TE polarization modes, respectively. For TM modes, the intrinsic bending losses with the radius of 1.5£gm, 2.5 £gm, and 5£gm are about 2573 dB/cm, 64 dB/cm, and 0.8 dB/cm, respectively. Next, we find that power coupling coefficients of the single ring all-pass filter configuration using the ring to ring couplers are much higher than the bus to ring couplers. The radiation losses of the ring to ring couplers for TM modes are improved significantly in all coupling gap widths. In a high-density integrated optics circuit, specially designed ring coupling region device structure is needed to address this serious optical loss issue.

Thesis (Ph.D.)--Ohio University, March, 2008. / Abstract only has been uploaded to OhioLINK. Includes bibliographical references (leaves 115-125)

Düsseldorf, Universiẗat, Diss., 2002.

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