Coating characterization of TiN & TiAIN on burr formation in drilling pragmatic investigation

Burrs are source of dimensional errors, jamming and misalignment in the assembly process. They may cause short circuits in electrical components and may reduce the fatigue life of the part. Furthermore, burrs can be a safety hazard to personnel because they are usually sharp. This scientific research investigates the characterization of 8 mm diameter, 120° point angle of coated drill tool in burr formation. The exit burrs were investigated using two different types of popular coatings, namely TiN and TiAlN. The effect of cutting speed and feed rate of the tool in burr formation onto the workpiece are discussed. In this study, the exit burr height was measured using optical microscope. Moderately harder material, 304L series stainless steel was used in the evaluation of the super coatings. The experiments were conducted using CNC HAAS Milling Machine. These experiments can be classified as hard drilling based on the experimental values and machining conditions

Three-Dimensional Finite Element Analysis of Conventional and Ultrasonic Vibration Assisted Micro-Drilling on PCB

Recent advancement in society’s demands has forced industries to produce more and more precise micro parts. With an advancement in engineering sciences, current manufacturers in various fields such as aerospace, medical, electronics, automobile, biotechnology, etc. have achieved the potential to fabricate miniaturized products, but with numerous technical challenges. Dimensional accuracy and surface integrity of the machined components are the key challenges and at the same time, cost minimization is strongly desired. To meet these challenges and demands, improvements in machining regarding new procedures, tooling, tool materials and modern machine tools are highly essential. Micromachining has shown potential to achieve the fast-growing needs of the present micro manufacturing sector. Additionally, new machining techniques like ultrasonic machining, laser drilling, etc. have been developed as an alternative source to reduce obstructions caused during macro/micro machining. The present research aims to perform three-dimensional (3D) finite element dynamic analysis for micro-drilling of multi-layer printed circuit boards (PCBs). Both conventional and ultrasonic vibration assisted micro-drilling (UVAMD) FE simulations have been compared to predict and evaluate the effect of process parameters on the output responses like stress generation and reaction forces and burr formation on the workpiece surfaces. The Lagrangian based approach is followed for the FE simulation including the mass and inertial properties of the proposed FE model. The predicted FE results are compared with the past experimental work for thrust force evaluation and burr formation on workpiece surfaces. The present work is supported with modal and harmonic analysis of stepped and conical horns along with micro drill bit. Here, horns made up of Aluminum 6061-T6, Titanium and Mild steel are chosen with micro drill bit of 0.3 mm diameter with varying tool materials (Tungsten carbide and High speed steel). The effects of natural frequencies with different mode shapes within the range of 15-30 kHz are shown. The frequency responses of micro drill with displacement conditions have been presented for longitudinal modes. The present simulation results will be helpful to conduct proper experimentation in order to achieve efficient machining and surface finish. The results enumerate that the drilling parameters have a strong influence on thrust forces and stresses occurring in micro-drilling. Ultrasonic assisted micro-drilling has a good potential in reduction of forces generated by vii selecting proper machining parameters. The FE simulation of UVA micro machining can further be enhanced and extended to various materials like plastics, sheet metal, other PCBs, etc. to predict the performance with varying machining and geometrical parameters

Protective hood

Protective hood is intended to give limited protection to head and neck. It is an interface device of a properly selected and configured protective ensemble during fire fighting and related emergency response activities

Ultrasonically-assisted drilling of carbon fibre-reinforced plastics

Carbon fibre-reinforced plastics (CFRP) are widely used in aerospace, automobile and other structural applications due to their superior mechanical and physical properties. CFRP outperform conventional metals in high strength-to-weight ratio. Usually, CFRP parts are manufactured near to net-shape;however,machining is unavoidable when it comes to assembly. Drilling the holes are essential to facilitate riveting and bolting of the components. However, conventional drilling (CD) induces different types of damages such as cracking, fibre pull-out, sprintling and delamination due to the abrasive nature, inhomogeneity and anisotropy of CFRP. A novel technique, ultrasonically-assisted drilling (UAD) is hybrid machining technique in which highfrequency (typically above 20 kHz) vibration are superimposed on a standard twist drill bit in axial direction using ultrasonic transducer. UAD has shown several advantages such as thrust force reduction, improving surface quality and lower bur-formation in drilling of conventional metals. UAD has also effectively been used for drilling brittle materials. [Continues.

Hybrid micro-machining processes : a review

Micro-machining has attracted great attention as micro-components/products such as micro-displays, micro-sensors, micro-batteries, etc. are becoming established in all major areas of our daily life and can already been found across the broad spectrum of application areas especially in sectors such as automotive, aerospace, photonics, renewable energy and medical instruments. These micro-components/products are usually made of multi-materials (may include hard-to-machine materials) and possess complex shaped micro-structures but demand sub-micron machining accuracy. A number of micro-machining processes is therefore, needed to deliver such components/products. The paper reviews recent development of hybrid micro-machining processes which involve integration of various micro-machining processes with the purpose of improving machinability, geometrical accuracy, tool life, surface integrity, machining rate and reducing the process forces. Hybrid micro-machining processes are classified in two major categories namely, assisted and combined hybrid micro-machining techniques. The machining capability, advantages and disadvantages of the state-of-the-art hybrid micro-machining processes are characterized and assessed. Some case studies on integration of hybrid micro-machining with other micro-machining and assisted techniques are also introduced. Possible future efforts and developments in the field of hybrid micro-machining processes are also discussed

Literature Review on Repair methods for Damaged Offshore Joints

Offshore structures subject to severe environmental loading may exhibit fatigue damage over time. In particular, fatigue cracks are a significant concern in welded components. Previous work has been published regarding the mitigation measures for many types of damage in steel structures. In addition, codes and standards, as for example, ISO, NORSOK, API, DNV, suggest suitable methods for mitigation and fatigue life improvement of welded components. Repair methods such as dry welding, structural clamps, remedial grinding, stop-hole drilling, and member removal can permanently or temporarily resolve the joint's fatigue damage. Mitigation methods like weld improvement techniques and grout filling can enhance the fatigue life of joints. The selection of repair methods is challenging as many parameters can influence the mitigation performance, such as crack size, location, and local detail geometry. Particularly, the repair method is different if the repair is to be performed in the atmospheric zone, splash zone, or in the submerged zone. The thesis aims to study different repair methods for fatigue damage in welded components and compare in terms of applicability, time off work, cost, fatigue life gain, and work deployment process. Analytic hierarchy process and Multi-criteria dimensional analysis are used to study the influence of selection criteria while choosing the suitable mitigation method. Case studies are performed based on the assumption of the crack size and location to select suitable mitigation measures. The conclusions are drawn regarding the selection criteria and work execution process

METHODS FOR HIGH-PRECISION AND MINIMALLY INVASIVE MICRO-ELECTRODE INSERTION IN DEEP BRAIN STIMULATION

Ph.DDOCTOR OF PHILOSOPH

Experimental and numerical analysis of conventional and ultrasonically-assisted cutting of bone

Bone cutting is widely used in orthopaedic, dental and neuro surgeries and is a technically demanding surgical procedure. Novel surgical methods are continually introduced in orthopaedic, neuro and dental surgeries and are aimed at minimising the invasiveness of the operation and allowing more precise cuts. One such method that utilises cutting with superimposed ultrasonic vibration is known as ultrasonically- assisted cutting (UAC). The main concern in bone cutting is the mechanical and thermal damage to the bone tissue induced by high-speed power tools. Recent technological improvements are concerned with the efforts to decrease the force required by the surgeon when cutting the bone as well as increases in surgery speed. A programme of experiments was conducted to characterise properties of a bone and get a basic understanding of the mechanics of bone cutting. The experiments included: (a) nanonindentation and tension tests to obtain the properties for the finite element (FE) bone cutting model, (b) high-speed filming to observe the chip formation process, which influences thermomechanics of the cutting process in conventional drilling (CD) and ultrasonically-assisted drilling (UAD) and, (c) plane cutting and drilling experiments to measure the levels of force and temperature rise in the bone tissue. Novel two-dimensional finite element (FE) models of cortical bone cutting were developed for conventional and ultrasonically-assisted modes with the MSC.MARC general FE code that provided thorough numerical analysis of thermomechanics of the cutting process. Mechanical properties such as the elastic modulus and strain-rate sensitivity of the bone material were determined experimentally and incorporated into the FE models. The influence of cutting parameters on the levels of stress, penetration force and temperature in the bone material was studied using conventional cutting (CC) and ultrasonically-assisted cutting (UAC). The temperature rise in the bone material near the cutting edge was calculated and the effect of cutting parameters on the level of thermal necrosis was analysed. The necrosis depth in bone was calculated as a distance from the cut surface to the point where the thermal threshold level was attained. Comparative studies were performed for the developed FE models of CC and UAC of bone and the results validated by conducting experiments and using data from scientific publications. The main outcome of the thesis is an in-depth understanding of the bone cutting process, and of its possible application in orthopaedics. Recommendations on further research developments are also suggested

Ultrasonic Enhancement of Pulsed Electrochemical Machining

Electrochemical machining (ECM) has gained prominence in the field on precise machining and has been subjected to a lot of study in order to bring its use to commercial levels. One of the key issues of electrochemical machining is the lack of proper flushing ECM by-products. Ultrasonic assisted ECM is often used to minimize the flushing issue. This study attempts a novel variation in ultrasonic assistance of ECM by introducing ultrasonic waves in the flowing electrolyte without vibrating tool or workpiece. This ensures intense agitation in the inter-electrode gap (IEG) with relatively simpler set-up. Aluminum 6061 is used as a workpiece material to drill holes. Stainless steel tubes coated with Teflon is used as tool. The Teflon coating minimizes the effect of stray current. Use of pulsed DC current and ultrasonic vibration improves the quality of the ECM’ed holes. The intense ultrasonic cavitation disturbs the anodic reaction in IEG negatively affecting MRR. On the other hand, the de-agglomeration of ECM by-products and depassivation of anodic workpiece improves surface roughness by approximately 50% and the taper angle of the hole by approximately 75%

Ultrasonic Enhancement of Pulsed Electrochemical Machining

Electrochemical machining (ECM) has gained prominence in the field on precise machining and has been subjected to a lot of study in order to bring its use to commercial levels. One of the key issues of electrochemical machining is the lack of proper flushing ECM by-products. Ultrasonic assisted ECM is often used to minimize the flushing issue. This study attempts a novel variation in ultrasonic assistance of ECM by introducing ultrasonic waves in the flowing electrolyte without vibrating tool or workpiece. This ensures intense agitation in the inter-electrode gap (IEG) with relatively simpler set-up. Aluminum 6061 is used as a workpiece material to drill holes. Stainless steel tubes coated with Teflon is used as tool. The Teflon coating minimizes the effect of stray current. Use of pulsed DC current and ultrasonic vibration improves the quality of the ECM’ed holes. The intense ultrasonic cavitation disturbs the anodic reaction in IEG negatively affecting MRR. On the other hand, the de-agglomeration of ECM by-products and depassivation of anodic workpiece improves surface roughness by approximately 50% and the taper angle of the hole by approximately 75%