Stuart Barnes

Surface hardening of steel using a high power diode laser

Heat treating the surface of medium carbon steels to produce a hardened layer whilst retaining a tough core is widespread throughout general engineering and may be accomplished by using a number of different sources of energy; flame and induction heating being common. In addition, the use of high power lasers is also a well-established process. The benefits attributed to the use of lasers are that they provide localised heat input, negligible distortion, the ability to treat specific areas, access to confined areas and short cycle times. Nd:YAG and CO, systems have both been used in this application for a number of years but restrictions to the wide spread use of lasers can be related to factors such as capital cost, perceived reliability of equipment, low area coverage rates and complexity of operation. Recently, a new category of high power industrial lasers has become commercially available which have the potential to overcome some of these barriers. Based on semi-conductor technology, high power diode lasers are reliable, easy to use, compact systems capable of producing a relatively large output spot. The current work has investigated the relationships between laser power and processing speed when using a 1.2 kW diode laser to harden a plain carbon and an alloy steel. The steels, British Standard 080M40 and 817M40, have similar carbon contents (0.4%), similar Mn contents (0.8%), but in addition 817M40 contains 1.75% Ni, 0.8% Cr and 0.25% Mo. Laser powers in the range 400-1000 W were used in conjunction with surface speeds of 50-1700 mmVmin. Microstructural examination of the treated surfaces revealed that conditions within the range examined were capable of producing structural changes and associated increases in hardness. Affected depths and maximum hardness achieved varied with power and speed, as well as with steel type. Hardened depths of greater than 0.5 mm were observed in both the plain carbon and the alloy steels. As would be expected, the maximum hardening effect was observed in the alloy steel, as was the maximum hardness. The work has demonstrated the technical capability of diode lasers in surface hardening both plain carbon and alloy steel with practical case depths being achieved

Effect of Heat Treatment on the Drilling Performance of Aluminium/SiC MMC

The extremely abrasive reinforcing phases present in metal matrix composites (MMCs) are known to dominate their machining behaviour. Consequently, the properties of the matrix material are often ignored. The work reported here investigated the influence of matrix microstructure on the drilling performance of a 2618 aluminium alloy reinforced with 18% silicon carbide particles. The drills used were 8 mm diameter, titanium nitride coated K10 carbide with through-tool cooling. The workpiece material was drilled in four heat treatment conditions: as-extruded, solution treated and solution treated and aged for 12 and 20 hours. Drilling performance was assessed by measuring the wear on the drills, cutting forces, surface finish and the condition of the worn cutting edges. The results indicated that softer as-extruded and solution treated materials produced less wear and lower cutting forces than the harder aged materials. However, the height of the burrs produced during drilling were found to be greater with the softer materials and the quality of the drilled surface was also inferior. Examination of the worn cutting edges indicated that the wear mechanism was primarily one of abrasion although some attrition and edge chipping was also observed. It was concluded that when drilling these materials, the heat treatment condition of the matrix exerts a significant influence on machinability.

The Effect of Workpiece Temperature on the Machinability of an Aluminum/SiC MMC

Metal matrix composites (MMCs) are becoming an increasingly important class of engineering material which are finding applications both in the automotive and aerospace industries. However, their machinability is regarded as poor due to the severe abrasive tool wear observed during machining. Prior to an investigation into the laser-assisted turning of an aluminium/silicon carbide MMC, the machining behaviour of the material after pre-heating to 200, 300, and 400 degrees C was investigated. The results indicated that at cutting speeds from 20-90 m/min the wear rate increased with increasing workpiece temperature although the wear mechanism remained one of abrasion. The presence of a built-up edge (BUE) was noted and a strong correlation found between its presence and the amount of wear produced. The results of this work show that within the range of parameters investigated, the pre-heating of the MMC had a detrimental effect on its machinability.

Machining of aluminium based metal matrix composites

Although metal matrix composites (MMCs) are generally regarded as extremely difficult to machine, it is also acknowledged that their machining behaviour is not fully understood. The work reviewed here confirms this widely held view but also suggests that the machinability of these materials can be improved by appropriate selection of the reinforcing phase, its volume fraction, size, and morphology as well as the composition and hardness of the matrix material. Cemented carbide tools can be used to machine some of the less abrasive materials at slow speeds but if higher production rates are required or the more abrasive materials are to be machined, polycrystalline diamond tooling is required.

Adaptive manufacturing scheduling: a flexible and configurable agent-based prototype

To improve the decision support tools available to manufacturing engineers operating in less than certain environments, an agent-based manufacturing scheduling system has been developed. In this paper, the application of intelligent agents to manufacturing problems is discussed and a description of the developed system is provided. The proof-of-concept demonstrator was developed using the JADE platform, XML ontology and a message passing system based on the contract-net protocol. The system was designed to be generic, allowing it to be tailored to suit a wide variety of different manufacturing problems. To demonstrate this, the system was used to model an existing manufacturing cell within Rolls-Royce. The system successfully produced schedules of comparable quality to the existing control system, with the added capability to proactively adapt to changing circumstances. Further work includes the development of a statistical analysis tool set to support and further testing to quantify the operational benefits of the agent-based scheduler.

Through-Tool Coolant Drilling of Aluminum/SiC Metal Matrix Composite

Through-tool coolant was applied to the drilling of an aluminium/SiC MMC. Titanium nitride coated, solid carbide drills were used to investigate the effect of the coolant application method on the performance of the drilling operation. Holes were produced dry, with conventional coolant and with through-the tool coolant. The results provided strong evidence that the conventional application of coolant was having no beneficial effect on the cutting operation compared to dry drilling. However, through-tool cooling gave a significant improvement in performance in terms of tool wear, cutting forces, surface finish and the height of the burrs produced. [S0094-4289(00)02104-6].

Effect of Laser Pre-Treatment on the Machining Performance of Aluminum/SiC MMC

Although the abrasive reinforcement in MMCs primarily controls their machining behavior, the properties of the matrix also exert an influence. A 1200 W diode laser was used, due to the large fotprint (5×0.3 mm) and the short wavelength (0.94 μm) to pre-treat a 2618 (18% SiC) alloy. The laser heating and self-quenching of the material modified the matrix properties. Machining performance was then assessed by measuring tool wear and edge condition, cutting forces, surface finish, and sub-surface damage. Results indicated that pre-treatment gave less wear, lower forces, and less sub-surface damage although abrasion remained the primary wear mechanism.

Knowledge intensive CAD in product design validation

Use of Computer Aided Engineering (CAE) for design validation in a product development cycle has been pursued as a state-of-the-art strategy to compete in the global competition. However, the combined use of CAD and CAE is still impractical to solve non-linear design problems that are multi-disciplinary in nature, even allowing for the speed offered by the advancement of computer computation. In order to bridge the gap for the full deployment of a computer aided/virtual design alternative, a methodology that involves the combined use of CAE and Artificial intelligent (AI)/knowledge intensive approach is proposed. Starting with a breakdown of attributes of a design task, a number of potential artificial intelligent algorithms are screened. Followed by a subsequent training schema, the most suitable AI algorithm is then selected. After the crystallization of the final knowledge database, the application can then be deployed into modules for subsequent or further new applications. The proposed model was illustrated with a case study for the design of a plastic toaster cover with respect to a heat test.

Low relative speed moving vehicle detection using motion vectors and generic line features

This paper presents a new approach to the detection of a vehicle with low relative speed to a monocular moving camera, for complementing moving vehicle detection using motion vectors from H.264/AVC encoder. This method makes use of the generic horizontal line features that exist on most vehicles as a clue of localizing moving vehicles. Further filtering and grouping of these detected lines followed by ego motion compensation can effectively detect moving vehicle with low relative speed for application in advanced driver assistance system. Our test results show a high detection rate of over 90%.

Study of Cutting Speed Variation in the Ultrasonic Assisted Drilling of Carbon Fibre Composites

Ultrasonic assisted drilling (UAD) has been proven effective for the thrust force reduction as compared to conventional drilling (CD) for same machining parameters. The following research was focused on the examination of exit delamination, machined surface and cutting temperature measurement in UAD and a comparison to that in CD at the cutting speeds of 0.942 m/min, 9.42 m/min, 94.2 m/min and 282.6 m/min at a constant feed rate of 0.05 mm/rev in the through-hole drilling of CFRP material. X-Ray computed tomography (CT) was used to identify the exit delamination, internal damage, circularity and center deviation in CD and UAD. A maximum of 82.8% reduction in the center deviation and 33.2% reduction in circularity of the holes were found when drilled in UAD as compared to those in CD. Furthermore, the cutting temperature in the drilling of CFRP has been measured and compared for both the cases of CD and UAD. Ultrasonic assistance produced 10°C higher cutting temperature than that in CD at the cutting speed of 282.6 m/min while at lower cutting speeds (0.942 m/min and 9.42 m/min), the cutting temperatures with and without ultrasonic assistance did not have a significant difference (2°C and 4°C respectively).