There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

비만아 부모의 돌봄 경험: q 방법론

In the laser treatment of a workpiece (9), e.g. for surface hardening, melting, alloying, cladding, welding or cutting, the adverse effect of reflectivity of the surface, when a pure, monochromatic laser (6) is used, is remedied by the simultaneous application of a relatively shorter wavelength beam (1). The two beams (1)(5) may be combined by a beam coupler (4) or may reach the workpiece (9) by separate optical paths (not shown). The shorter wavelength beam (1) improves the coupling efficiency of the higher- powered laser beam (5).

Laser Material Processing

Nanoscale hydroxyapatite particles for bone tissue engineering

Additive manufacturing is a technology rapidly expanding on a number of industrial sectors. It provides design freedom and environmental/ecological advantages. It transforms essentially design files to fully functional products. However, it is still hampered by low productivity, poor quality and uncertainty of final part mechanical properties. The root cause of undesired effects lies in the control aspects of the process. Optimization is difficult due to limited modelling approaches. Physical phenomena associated with additive manufacturing processes are complex, including melting/solidification and vaporization, heat and mass transfer etc. The goal of the current study is to map available additive manufacturing methods based on their process mechanisms, review modelling approaches based on modelling methods and identify research gaps. Later sections of the study review implications for closed-loop control of the process.

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Additive manufacturing methods and modelling approaches: a critical review

Fundamentals of Laser Processing.- Basics of Lasers.- Laser Materials Interactions.- Laser Machining.- Manufacturing Processes: An Overview.- Laser Drilling.- Laser Cutting.- Three-Dimensional Laser Machining.- Laser Micromachining.- Laser Fabrication.- Laser Forming.- Laser-Based Rapid Prototyping Processes.- Laser Welding.- Special Topics in Laser Processing.- Laser Interference Processing.- Laser Shock Processing.- Laser Dressing of Grinding Wheels.- Lasers Processing in Medicine and Surgery.

Laser Fabrication and Machining of Materials

Tribological behavior of plasma-sprayed carbon nanotube-reinforced hydroxyapatite coating in physiological solution.

Spark plasma sintering of graphene reinforced zirconium diboride ultra-high temperature ceramic composites

In this work, pure nickel and nickel composite coatings (Ni–Al 2 O 3 , Ni–SiC, and Ni–ZrO 2 ) were deposited from Watts bath using direct current (DC), pulsed current (PC), and pulsed reverse current (PRC) electrodeposition conditions. Detailed investigations on the effect of deposition conditions on the evolution of surface microstructure, crystallographic micro-texture, microhardness, and sliding wear behavior of pure nickel and nickel composite coatings are presented. For all the coatings, the PC and PRC deposition conditions resulted in more random/weak crystallographic texture compared to DC deposition. The composite coatings deposited using PC and PRC deposition also exhibited significant improvement in microhardness and wear resistance due to enhanced reinforcement of nanoparticles in the coatings. Also, the effect of nanoparticle content of the electrolyte bath on the surface microstructure, tribological properties, and level of reinforcement in the Ni–Al 2 O 3 composite coating is investigated. The reinforcement of nanoparticles in the Ni–Al 2 O 3 composite coatings increased linearly with the amount of nanoparticle loading in the electrolyte bath. The microhardness and wear resistance of the Ni–Al 2 O 3 composite coatings also improved with increasing Al 2 O 3 content in the coatings.

Effect of electrodeposition conditions and reinforcement content on microstructure and tribological properties of nickel composite coatings

Fe-based bulk metallic glasses exhibit very high hardness, elastic modulus/limit and wear/corrosion resistance. In the present investigation, an attempt has been made to develop an amorphous coating with Fe 48 Cr 15 Mo 14 Y 2 C 15 B 6 bulk metallic glass on AISI 4140 substrate by laser surface processing. Following coating, the microstructure and phase aggregate were analyzed by scanning electron microscope and X-ray diffraction, respectively. Microhardness and wear resistance were assessed using Vickers microhardness tester and ball-on-plate wear testing machine, respectively. The coating thickness varied directly with incident laser power and interaction time. Despite trials with wide range of process parameters, the present experiments were unable to retain complete amorphous surface microstructure after laser surface coating. Numerical prediction of the thermal profile and related parameters suggest that the cooling rate and thermal gradient experienced by the coated zone were fairly high. Yet failure to retain amorphous/glassy microstructure of an otherwise bulk metallic glassy alloy suggests that compositional changes (solute redistribution) within the coated zone and across the coating–substrate interface are responsible for nucleation and growth of crystalline phases from the melt. However, correlation between coating parameters and surface microstructure and properties allowed determination of the optimum conditions that ensured fine grained uniform microstructure with a significant improvement in hardness and wear resistance.

Sandip P. Harimkar

Papers

Laser Fabrication and Machining of Materials

Tribological behavior of plasma-sprayed carbon nanotube-reinforced hydroxyapatite coating in physiological solution.

Spark plasma sintering of graphene reinforced zirconium diboride ultra-high temperature ceramic composites

Effect of electrodeposition conditions and reinforcement content on microstructure and tribological properties of nickel composite coatings

Laser surface coating of Fe–Cr–Mo–Y–B–C bulk metallic glass composition on AISI 4140 steel