Papers by Author: Michael N. Morgan

Abstract: The grinding process has particular interest in that contact temperatures have great significance for quality and integrity of machined surfaces. Hardened surfaces may be damaged by softening and or being stressed, being hardened or re-hardened, burned or cracked. It is important in grinding for the fluid to remove heat from the grinding contact zone to avoid thermal damage to the workpiece surface and/or sub-surface layers. The cooling effect of grinding fluid can be quantified by the convective heat transfer coefficient (CHTC) acting in the grinding zone. This paper presents values of the CHTC based on measured grinding temperatures. The paper also presents a new convective heat transfer model based on principles of applied fluid dynamics and heat transfer. Predicted values for the CHTC calculated from the model are compared with results from experiment obtained under a range of grinding conditions and with experimental data. The results demonstrate that the new CHTC model improves the accuracy of prediction and helps explain the variation in the value of CHTC under varying process conditions. Results also show that convection efficiency strongly depends on the grinding wheel speed, grinding arc length and fluid properties.

Abstract: This work comparatively studied the performances of straight cemented carbide tools and PVD coated carbide tools in high speed dry turning of Ti-6Al-4V alloy. Systematic machining tests have been performed and the tool life data were analysed using multiple linear regression method to establish extended Taylor tool life models. The wear mechanisms for both tools have been investigated in detail through SEM observation and X-ray energy dispersive microanalysis (EDS).

Abstract: This paper reports on the results of an experimental study in vibratory mass finishing. The machining performance of abrasive media produced entirely from recycled thermally treated glass is compared with that of conventional ceramic and polyester based media. Tests were completed in a vibratory trough machine over a range of work materials. It has been demonstrated that the recycled glass media can match the performance of conventional media in respect of surface finish (Ra), burr removal and ‘brightness’. The wear rate and self-attrition rate were also found to compare favourably with that of conventional media. The results of this study show considerable promise for the wider use of this highly innovative media.

Abstract: In order to obtain the effective depth of cut on the ground surface, a new grinding process model taking into account thermal expansions of the grinding wheel and the workpiece, elastic deformations of the grinding machine, the grinding wheel and the workpiece and the wheel wear was proposed. Using proposed model, the effective depth of cut was calculated using measured results of the applied depth of cut and the normal grinding force.

Abstract: It is considered that the contact stiffness between the grinding wheel and the workpiece depends on the number of the abrasive grains in contact with the workpiece and the support stiffness of a single abrasive grain. In this paper, the calculating method of the theoritical contact stiffness of grinding wheel in grinding operation was proposed. Comparing calculated results of the contact stiffness in grinding operation with measured it in the stationary state, the contact stiffness of the grinding wheel in grinding operation was investigated.

Abstract: The boundary layer of air rotating with the grinding wheel can result in fluid starvation in the contact region. The boundary layer acts a barrier to fluid penetration and prevents fluid reaching the contact region and the fluid is deflected elsewhere. Such a situation is inefficient and wasteful. This work reports on an investigation of the air boundary layer aimed at increasing understanding of boundary layer for development of improved fluid delivery systems. The work reported focuses on the outcomes of experimental tests using the Laser Doppler Anemometry technique. Three velocity components of the air flow around the periphery of a rotating grinding wheel were measured for a range of wheel speeds. The contour distribution of the velocity and the turbulent distribution of velocity clearly show the air flow motion around the grinding wheel.

Abstract: The delivery of grinding fluid to the contact zone is generally achieved via a nozzle. The nozzle geometry influences the fluid velocity and flow pattern on exit from the nozzle orifice. It is important to the efficiency of the process and to the performance of the operation that the fluid is delivered in a manner that ensures the desired jet velocity has adequate coverage of the contact zone. Often, assumptions about adequate coverage are based on visual inspections of the jet coherence. This paper provides new insight into the internal nozzle flows and the coherent length of a wide range of nozzle designs. The work presents a new analytical model to predict coherent length which is shown to correlate well with measured data from experiment. Recommendations are given to guide a user to optimal design of nozzles to ensure adequate fluid supply to the contact zone.

Abstract: This paper describes the structure, content and relations employed in the development of an intelligent grinding database. The intelligent database has been constructed in MS Access with Visual Basic support code. The database was developed as an integral feature of an intelligent grinding assistant (IGA  ). The IGA  has been implemented and evaluated on a cooperating partners CNC machine tool.

Abstract: A thermal model has been implemented in industrial operations where reliability and robustness are important. To fully exploit the potential and usefulness of the thermal model it is necessary to tune the model to accommodate a wide range of wheel / workpiece combinations whilst also satisfying different quality criteria. Implementation is relatively simple and thermal damage to the workpiece can be avoided in most grinding operations. The monitoring process can also be used to aid in optimising dressing intervals or as a tool to identify deteriorating conditions. It is important to understand how to develop and implement strategies to satisfy different user needs. This paper reports on issues associated with tuning the model. Guidance is provided to assist with implementation of the thermal model either as a stand alone monitoring tool or as a fully integrated embedded feature of an intelligent control system. The paper has been prepared in response to queries on this matter from industrial practitioners.

Abstract: The grinding fluid is typically used to provide functions such as lubrication and cooling in order to reduce surface grinding temperatures effectively in order to achieve better work-piece surface integrity and higher wheel life. This paper investigates the convection heat transfer coefficient of fluid based on the fluid dynamic and thermal modelling within the grinding zone under different grinding condition. This work makes it possible to determine a suitable value of the useful flowrate fluid through the grinding contact arc under optimization of the wheel speed, work speed and jet velocity of nozzle. Its simplicity and accuracy allow application to a wide range of grinding situations from shallow to high efficiency deep grinding.