Z.Y. Wang’s research while affiliated with University of Nevada, Las Vegas and other places

Failure of polycrystalline cubic boron nitride (PCBN) cutting tools, resulting from microcrack development, is one of the major causes of tool replacement in the machining of advanced materials. In this research, the J-integral method is applied to study the relationship between crack growth in a cutting tool and tool life in a hybrid machining process. Results show that with the decrease of the cutting temperature and its gradient in the cutting tool, the J value decreases and the tendency for micro crack propagation in the tool declines. Therefore, tool wear and early fracture rates are remarkably reduced.

A new approach for machining of Inconel 718 is presented in this paper. It combines traditional turning with cryogenically enhanced machining and plasma enhanced machining. Cryogenically enhanced machining is used to reduce the temperatures in the cutting tool, and thus reduces temperature-dependent tool wear to prolong tool life, whereas plasma enhanced machining is used to increase the temperatures in the workpiece to soften it. By joining these two non-traditional techniques with opposite effects on the cutting tool and the workpiece, it has been found that the surface roughness was reduced by 250%; the cutting forces was decreased by approximately 30–50%; and the tool life was extended up to 170% over conventional machining.

A new approach for the machining of tantalum is presented. The new approach is a combination of traditional turning and cryogenically enhanced machining (CEM). In the tests, CEM was used to reduce the temperature at the cutting tool/workpiece interface, and thus reduce the temperature-dependent tool wear to prolong cutting tool life. The new method resulted in a reduction of surface roughness of the tantalum workpiece by 200% and a decrease of cutting forces by approximately 60% in experiments. Moreover, cutting tool life was extended up to 300% over that in the conventional machining.

Recent study and development activity in the field of precision ultrasonic machining (USM) process has focused on the ceramic (Al2O3). This paper first analyzes the USM process, mechanism, dynamics, and trends. It then discusses, in detail, the USM process applications on the ceramic (Al2O3).

This paper presents a technique for machining of advanced ceramics with liquid nitrogen (LN2) cooled polycrystalline cubic boron nitride (PCBN) tool, titanium alloys, Inconel alloys, and tantalum with cemented carbide tools. With LN2 cooling, the temperature in the cutting zone is reduced to a lower range, therefore, the hot-strength and hot-hardness of the tool remain high, and the temperature-dependent tool wear reduces significantly under all machining conditions. The surface roughness of all materials machined with LN2 cooling were found to be much better than the surface roughness of materials machined without LN2 cooling after the same length of cutting.

This paper presents an analysis of the entry process and tool fracture in the milling operation. Equations representing different types of initial contacts are derived. Experimental and theoretical results reveal that the direction of the cutting force and the initial location on the rake face determine the entry fracture in milling cutters.

Ultrasonic machining process is an efficient and economical means of precision machining of ceramic materials. However, the mechanics of the process with respect to crack initiation and propagation, and stress development in the ceramic workpiece subsurface are still not well understood. This article presents experimental simulation of the process mechanics in an attempt to analyze the material removal mechanism in machining of ceramic (Al2O3). It is found that low-impact force causes only structural disintegration and particle dislocation. The high-impact force contributes to cone cracks and subsequent crater damage.

This paper reports the wear characteristics of a CBN tool in the turning of an advanced structural ceramic (silicon nitride) under dry cutting and cryogenic cooling conditions. A cooling system is designed to control the cutting temperatures on the tool by circulating cryogenic coolant through a reservoir built on the top of the cutting tool. This arrangement maintains the tool's hot-strength at its desirable range to resist tool wear in the cutting process. Experiments show that the tool wear significantly reduces with cryogenic cooling. Finite element analysis is used to estimate cutting temperatures on the tool and to reveal the reasons for different wear characteristics in the two cases. The analysis shows that the maximum temperature on the tool falls from 1153°C (without liquid nitrogen cooling) to 829°C (with liquid nitrogen cooling).

This paper presents concepts of an Internet assisted manufacturing system for agile manufacturing practice. It consists of a CAD/CAPP/CAM/CAA integrated Central Network Server (CNS) which links to local FMS, or CNC machines by means of cable connections. After a local user inputs the product information, the CNS can generate complete CAD/CAPP /CAM/CAA files and control the remote FMS or CNC machines to accomplish the whole production process. This system uses Internet as an interface between a user and the CNS and allows a local user to operate remote machines connected to the Internet. This paper also proposes to build a network of manufacturing database and a research database to improve the manufacturing agility.

This paper presents a dynamic analysis of the ultrasonic machining process based on impact mechanics. Equations representing the dynamic contact force and stresses caused by the impinging of abrasive grits on the work, are obtained by solving the three-dimensional equations of motion. The factors affecting the material removal rate have been studies. It is found that the theoretical estimates obtained from the dynamic model are in good agreement with the experimental results.