In order to simulate foreign object damage (FOD) phenomenon in aircraft high-pressure compressor ... more In order to simulate foreign object damage (FOD) phenomenon in aircraft high-pressure compressor blades made of a nickel-based super-alloy, Johnson-Cook (J-C) plasticity model was used. For prediction of materialÕs plastic behavior at temperature of 400°C (working temperature of the blades) in the range of strain rates associated with the FOD phenomenon (in order of 10 6 s 21), material parameters of A, B, C, n and m for the J-C plasticity model had to be determined experimentally. Parameters of A, B and n with values of 1108, 699 MPa and 0.5189, respectively, were obtained from quasi-static tensile tests. Moreover, m was determined to be 1.2861, also through quasi-static tensile tests with a strain rate of 1 s 21 at three temperatures of 475, 550 and 625°C. However, in order to determine C, firstly a steel ball was impacted on the surface of a flat specimen made of a precipitation-hardening alloy, and then, the impact site was 3D scanned to obtain the induced crater profile. Finally, the impact test (ballistic) was simulated using Abaqus, and a C value of 0.0085 was determined by comparing the actual crater profile with the one obtained from the simulation through a trial-and-error approach.
The limitations of significant tool wear and tool breakage of commercially available fluted micro... more The limitations of significant tool wear and tool breakage of commercially available fluted micro-end mill tools often lead to ineffective and inefficient manufacturing, while surface quality and geometric dimensions remain unacceptably poor. This is especially true for machining of difficult-to-machine (DTM) materials, such as super alloys and ceramics. Such conventional fluted micro-tool designs are generally down scaled from the macro-milling tool designs. However, simply scaling such designs from the macro to micro domain leads to inherent design flaws, such as poor tool rigidity, poor tool strength and weak cutting edges, ultimately ending in tool failure. Therefore, in this article a design process is first established to determine optimal micro-end mill tool designs for machining some typical DTM materials commonly used in manufacturing orthopaedic implants and micro-feature moulds. The design process focuses on achieving robust stiffness and mechanical strength to reduce too...
We present experimental evidence of reusable, reliable cyclic olefin copolymer (COC) moulds in so... more We present experimental evidence of reusable, reliable cyclic olefin copolymer (COC) moulds in soft contact lens manufacturing. The moulds showed high performance surface roughness characteristics despite >20 kW exposure to 365 nm ultraviolet (UV) light from repeated use. Ultra-precision manufacturing techniques were used to fabricate transparent COC mould inserts and to produce soft contact lenses from liquid monomer compositions. Both polymer and silicone hydrogels were fabricated with more than 60 individual uses of the moulds. White light interferometry measured the surface roughness (Sa) of the COC moulds to be almost unchanged before and after repeated use (Sa 16.3 nm before vs. 16.6 nm after). The surface roughness of the prototyped lenses and that of commercially available soft contact lenses were then compared by white light interferometry. The surface roughness of the lenses was also nearly unchanged, despite undergoing more than 60 uses of the COC moulds (lens Sa 24.4 ...
Rotary ultrasonic-assisted machining (RUAM) processes have been recognized as leading, non-tradit... more Rotary ultrasonic-assisted machining (RUAM) processes have been recognized as leading, non-traditional, high-precision machining processes that have been recently developed to machine a vast range of advanced, hard-to-machine, brittle materials like reinforced composites, ceramics, and metallic alloys to a very high surface finish in an efficient and cost-effective manner. As the field of materials engineering further progresses in search of materials with very high hardness and resistance to wear for use in the biomedical, energy, aerospace, automobile, and optical industries, so too must the machining processes progress in order to fulfill the demand for manufacturing the components. RUAM processes have been shown to reduce cutting forces and improve tool life during machining of very hard and brittle materials so far. Therefore, from the very first implementation of ultrasonic energy for higher-quality machining in the late 1920s to today's advanced computer numerical control RUAM 5-axis machining centers, this review examines the development history, the working mechanisms, and the critical performance of each RUAM process, which influence the process outputs. The advancements, applications, limitations, and future perspective of RUAM processes are also discussed in detail with the aim of providing clear insight into the future of RUAM, for further development and to extend the range of its applications.
Micro-milling is a precision manufacturing process with broad applications across the biomedical,... more Micro-milling is a precision manufacturing process with broad applications across the biomedical, electronics, aerospace, and aeronautical industries owing to its versatility, capability, economy, and efficiency in a wide range of materials. In particular, the micro-milling process is highly suitable for very precise and accurate machining of mold prototypes with high aspect ratios in the microdomain, as well as for rapid micro-texturing and micro-patterning, which will have great importance in the near future in bio-implant manufacturing. This is particularly true for machining of typical difficult-to-machine materials commonly found in both the mold and orthopedic implant industries. However, inherent physical process constraints of machining arise as macro-milling is scaled down to the microdomain. This leads to some physical phenomena during micro-milling such as chip formation, size effect, and process instabilities. These dynamic physical process phenomena are introduced and d...
In order to simulate foreign object damage (FOD) phenomenon in aircraft high-pressure compressor ... more In order to simulate foreign object damage (FOD) phenomenon in aircraft high-pressure compressor blades made of a nickel-based super-alloy, Johnson-Cook (J-C) plasticity model was used. For prediction of materialÕs plastic behavior at temperature of 400°C (working temperature of the blades) in the range of strain rates associated with the FOD phenomenon (in order of 10 6 s 21), material parameters of A, B, C, n and m for the J-C plasticity model had to be determined experimentally. Parameters of A, B and n with values of 1108, 699 MPa and 0.5189, respectively, were obtained from quasi-static tensile tests. Moreover, m was determined to be 1.2861, also through quasi-static tensile tests with a strain rate of 1 s 21 at three temperatures of 475, 550 and 625°C. However, in order to determine C, firstly a steel ball was impacted on the surface of a flat specimen made of a precipitation-hardening alloy, and then, the impact site was 3D scanned to obtain the induced crater profile. Finally, the impact test (ballistic) was simulated using Abaqus, and a C value of 0.0085 was determined by comparing the actual crater profile with the one obtained from the simulation through a trial-and-error approach.
The limitations of significant tool wear and tool breakage of commercially available fluted micro... more The limitations of significant tool wear and tool breakage of commercially available fluted micro-end mill tools often lead to ineffective and inefficient manufacturing, while surface quality and geometric dimensions remain unacceptably poor. This is especially true for machining of difficult-to-machine (DTM) materials, such as super alloys and ceramics. Such conventional fluted micro-tool designs are generally down scaled from the macro-milling tool designs. However, simply scaling such designs from the macro to micro domain leads to inherent design flaws, such as poor tool rigidity, poor tool strength and weak cutting edges, ultimately ending in tool failure. Therefore, in this article a design process is first established to determine optimal micro-end mill tool designs for machining some typical DTM materials commonly used in manufacturing orthopaedic implants and micro-feature moulds. The design process focuses on achieving robust stiffness and mechanical strength to reduce too...
We present experimental evidence of reusable, reliable cyclic olefin copolymer (COC) moulds in so... more We present experimental evidence of reusable, reliable cyclic olefin copolymer (COC) moulds in soft contact lens manufacturing. The moulds showed high performance surface roughness characteristics despite >20 kW exposure to 365 nm ultraviolet (UV) light from repeated use. Ultra-precision manufacturing techniques were used to fabricate transparent COC mould inserts and to produce soft contact lenses from liquid monomer compositions. Both polymer and silicone hydrogels were fabricated with more than 60 individual uses of the moulds. White light interferometry measured the surface roughness (Sa) of the COC moulds to be almost unchanged before and after repeated use (Sa 16.3 nm before vs. 16.6 nm after). The surface roughness of the prototyped lenses and that of commercially available soft contact lenses were then compared by white light interferometry. The surface roughness of the lenses was also nearly unchanged, despite undergoing more than 60 uses of the COC moulds (lens Sa 24.4 ...
Rotary ultrasonic-assisted machining (RUAM) processes have been recognized as leading, non-tradit... more Rotary ultrasonic-assisted machining (RUAM) processes have been recognized as leading, non-traditional, high-precision machining processes that have been recently developed to machine a vast range of advanced, hard-to-machine, brittle materials like reinforced composites, ceramics, and metallic alloys to a very high surface finish in an efficient and cost-effective manner. As the field of materials engineering further progresses in search of materials with very high hardness and resistance to wear for use in the biomedical, energy, aerospace, automobile, and optical industries, so too must the machining processes progress in order to fulfill the demand for manufacturing the components. RUAM processes have been shown to reduce cutting forces and improve tool life during machining of very hard and brittle materials so far. Therefore, from the very first implementation of ultrasonic energy for higher-quality machining in the late 1920s to today's advanced computer numerical control RUAM 5-axis machining centers, this review examines the development history, the working mechanisms, and the critical performance of each RUAM process, which influence the process outputs. The advancements, applications, limitations, and future perspective of RUAM processes are also discussed in detail with the aim of providing clear insight into the future of RUAM, for further development and to extend the range of its applications.
Micro-milling is a precision manufacturing process with broad applications across the biomedical,... more Micro-milling is a precision manufacturing process with broad applications across the biomedical, electronics, aerospace, and aeronautical industries owing to its versatility, capability, economy, and efficiency in a wide range of materials. In particular, the micro-milling process is highly suitable for very precise and accurate machining of mold prototypes with high aspect ratios in the microdomain, as well as for rapid micro-texturing and micro-patterning, which will have great importance in the near future in bio-implant manufacturing. This is particularly true for machining of typical difficult-to-machine materials commonly found in both the mold and orthopedic implant industries. However, inherent physical process constraints of machining arise as macro-milling is scaled down to the microdomain. This leads to some physical phenomena during micro-milling such as chip formation, size effect, and process instabilities. These dynamic physical process phenomena are introduced and d...
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Papers by Lorcan O'Toole