This paper is motivated by a computer experiment conducted for optimizing residual stresses in the machining of metals. Although kriging is widely used in the analysis of computer experiments, it ...cannot be easily applied to model the residual stresses because they are obtained as a profile. The high dimensionality caused by this functional response introduces severe computational challenges in kriging. It is well known that if the functional data are observed on a regular grid, the computations can be simplified using an application of Kronecker products. However, the case of irregular grid is quite complex. In this paper, we develop a Gibbs sampling-based expectation maximization algorithm, which converts the irregularly spaced data into a regular grid so that the Kronecker product-based approach can be employed for efficiently fitting a kriging model to the functional data.
Mechanical micro-cutting methods such as micro-grooving, micro-turning, and micro-milling are emerging as viable alternatives to lithography based micromachining for applications in optics, ...semiconductors and micro moulding. However, certain factors limit the range of workpiece materials that can be processed using these methods. For difficult-to-machine materials such as mould and die steels and sintered ceramics, limited cutting tool and machine stiffness and/or strength pose significant barriers to the efficient use of mechanical micromachining methods. In addition, when cutting at the microscale, the effect of tool/machine deflection on the dimensional accuracy of the machined feature can be pronounced. This chapter describes a novel hybrid mechanical micromachining process called Laser-Assisted Mechanical Micromachining, or LAMM, that is designed to overcome the aforementioned limitations of mechanical micro-cutting methods. The chapter describes the basic idea behind LAMM and the development of a LAMM-based prototype system for micro-grooving, experimental characterisation and modelling of the laser assisted microgrooving process, and concludes with a discussion of future directions of this technology.
Current emphasis in manufacturing industries is on achieving higher levels of product quality. For machined parts, the surface texture constitutes one of the most important aspects of product quality ...that often determines its functional characteristics. In order to accomplish the goal of producing parts conforming to the functional requirements, it is necessary to gain a better understanding of the surface generation mechanism. The focus of this thesis is on developing analytical models to describe the surface texture generated in the end milling process. This process is widely used in the aerospace industry to machine a wide range of work materials and complex geometrical shapes. Models are developed for predicting the two- and three-dimensional surface texture generated in peripheral and slot end milling. These models incorporate the ideal effects of tool geometry and process kinematics, and non-ideal effects of cutter/spindle runout, cutter flexibility, and tool wear. Model verification is performed through actual machining experiments. Significant improvements in the prediction of the slot floor surface geometry are obtained by explicitly modeling the effects of the radial rake and the end tooth relief angles. It is shown that, in general, these angles are important and, depending on their magnitudes, can affect the surface texture parameters greatly. The effect of end mill flexibility on the slot floor surface texture is examined in detail. It is found that the extent to which back-cutting impacts the floor surface texture is governed by the compliance of the end mill. The effect of tool flank wear on the surface texture produced in peripheral end milling is investigated experimentally and a preliminary model presented. A computer-based framework to study certain functional properties of machined surfaces in a tribological environment is also described. The utility of this framework is demonstrated through the use of end milling surface texture prediction models developed in this thesis.
Addresses the modeling and prediction of the holding force in an electromagnetic chuck used in precision machining. First, an analytic model termed the magnetic circuit model was developed and ...compared with experimental holding force data. It was found that this model, although simple in form, was limited in its range of application. The discrepancies in the model were attributed to its inability to accurately represent the leakage flux and the non-uniform distribution of the magnetic flux. A three-dimensional finite element model was then developed to overcome these limitations. Predictions with this model were found to be in better agreement with the experiments, yielding prediction errors within 25% for most cases. The finite element model also provides an explanation for the decrease observed in the measured holding force past its maximum value.
