Takushi Saito

Laser welding of plastics transparent to near-infrared radiation

This paper deals with a development of laser welding of colored plastics. Welding of thermoplastics using near-IR lasers has been seen in wide industrial application. Most of thermoplastics are transparent to near-IR laser. Particular characteristic of near-IR laser radiation has the ability to heat the interface between the transparent part and absorbent one colored with pigments. However, it is difficult to weld a pair of transparent materials by a laser beam, since there is no absorption region within them. In this paper, the influence of near-IR transparent plastics on the yield strength of their weldments has been studied: various colored plastics transparent to diode laser radiation were tested as the welding material. The heat transfer within a welding system was also analyzed and assessed the appropriate absorptivity and transmittance of overlapping colored plastic.

Surface temperature monitoring of convex molten polymer using interferometric tomography with direct cylindrical reconstruction

Temperature monitoring and control of a convex molten polymer sheet and surrounding cooling air flows are demanded in order to improve both the productivity and the quality of the polymer sheet products. The accurate measurement of temperature is desired when molten polymer changes its phases. An intrusive thermometer such as a thermocouple has difficulty because a molten polymer blown out from a ring die is extremely thin. Also temperature measurement with an infrared camera is not applicable since the polymer film is lightly transparent for the infrared radiation and the intensity of infrared radiation from the polymer film is too weak. In this research, we proposed a novel method for non-intrusive temperature measurement with the quantitative interferometer in conjunction with direct cylindrical computer tomography, and discussed its feasibility for measuring the temperature distribution on a convex surface.

Dispersion control of immiscible polymer blend using selective heating by infrared laser irradiation: Numerical study

In this study, two-phase immiscible polymer blend with selective radiation heating by infrared laser is studied numerically. The phase-field model of a non-isothermal flow, which accounts for laser induced temperature field, two-phase flow with interfacial tension and Marangoni effect, was developed. This model was used to simulate a droplet deforming in shear flow with various shear rate, droplet size and laser irradiation power. Based on the simulation results the effect of the selective radiation heating by infrared laser to the droplet deformation, the break-up situation and the micro-structure of the polymer blend was discussed. The paper concludes with suggestions for future research and potential applications.

Supervisory level control of robot plasma spray coating process with task level modification based on process database

This paper focuses on implementing supervisory level control of robot plasma spraying on internal surface of a free-form tubular shape found in gas turbine engine parts. Plasma spray process is used for applying Thermal Barrier Coating (TBC) onto a surface of gas turbine parts to provide layer of anti-corrosion and heat resistance made out of ceramic material built up during plasma spray deposition. At the core of the supervisory control lie three important components. First is the planning level. Second is the Task Level and third is the Process level implementation. In the scope of this paper, we will describe this supervisory level control structure and provide focus on the Torch Speed Modification in Task Level Implementation.

Formation of Electro-Conductive Part on Polymeric Material Surface by CO2 Laser Irradiation

In this study, a method to directly form an electrically conductive layer on the surface of polymeric material by using infrared laser irradiation was investigated. Polyacrylonitrile, which was shaped into a small disk 20 mm in diameter and 5 mm thick, was used as a test specimen. The conditions for pyrolysis were obtained by referencing the conditions for commercial carbon fiber. First, the specimen was processed in air at a relatively low temperature (around 250°C) for the stabilization treatment (i.e., fireproofing), then its surface was heated at a higher temperature (above 1000°C) for the carbonization treatment (i.e., graphitizing). Both an infrared furnace and a carbon dioxide laser were used as heating devices to find optimal conditions. Property changes in the material due to the thermal treatment were measured using Fourier transform infrared spectroscopy, and the electrical conductivity of the carbonized surface was measured using a four-probe method. The results showed that an electrical conductivity of 11.4 S/cm (siemens per centimeter) was achieved with a laser intensity of 8.6 W/cm2 for 5 min for the stabilization, and a laser intensity of 34 W/cm2 for 10 s for the carbonization.Copyright

Electric Charge of Micro and Nano Bubbles by Interferometric Laser Imaging Technique

In this paper we investigated ζ potential of microbubbles by electrophoresis method. The individual bubble diameter measured by means of interferometric laser imaging technique. The experimental results showed that different methods for producing microbubbles which were pressurizing dissolution method, swiveling gas-liquid two-phase flow method and electrolysis method did not make difference in the resultant values of ζ potential. In order to understand the mechanism of charging characteristic of microbubbles, we changed the pH of the deionized water and added alcohols or a surfactant to the deionized water. The results showed that the absolute value of the ζ potential increased when the pH increased. ζ potential was drastically changed by alcohols and surfactant which easily absorbed on the air-water interface. Moreover, simultaneous measurement of ζ potential and diameter of shriking microbubble resulted that bubbles shose diameter is less than 3 μ m were observed by using Mie theory.© 2011 ASME

Visualization Study of Spreading Behavior in Coating Process of High Viscous Fluid

This paper deals with a high viscous fluid behavior under the coating head of Melt Transcription Molding Process, which is one of a novel polymer processing recently developed. Flow field analysis of the process is the key issue to determine the optimum process conditions. Thus a simplified experimental apparatus was constructed to model the coating process under iso-thermal condition, and the particle image velocimetry (PIV) was applied to visualize the flow field. The results showed that the flow condition was significantly influenced by the feed rate of the high viscous fluid and the geometry of the die exit. Pressure distribution on the coated surface was also estimated according to the strain rate in the field. Obtained result was compared with the pressure profile experimentally measured, and they showed quantitative agreement. By summarizing these results, optimum conditions to stabilize the coating flow was discussed.

Local Radiation Heating Technique of Polymeric Materials Using Functional-Dye

In this study, the authors added a functional dye to a material which was transparent in initial state, to locally change the radiation absorption coefficient of the material. By using this material, we proposed a radiation heating technique that can achieve a selective local heating in three-dimensional system and investigated its feasibility. Temperature change of the test sample was measured in the experiment, and the characteristic of the presenting technique was investigated. To obtain better understanding of the presenting technique, numerical simulation of the temperature distribution inside the sample was also performed. In the experiment, photochromic dye and thermochromic dye were used as functional dyes and they were individually added to thermoplastic polymeric material (polystyrene) by using organic solvent (tetrahydrofuran). Then the material containing the dye was dried and processed to give a certain shape for the experiment. He-Cd laser and Ar ion laser were properly used as the excitation and the heat sources according to the type of dye. Experimental result showed that local heating of the material was achieved only in quite thin surface region in case of photochromic dye. On the other hand, local heating inside the material was successfully achieved in case of thermochromic dye. However, it was also observed that the heating point was moved to the upstream direction of the laser beam. To examine the solution of this problem, effect of the laser irradiation conditions on the moving speed of the heating point was discussed based on the numerical simulation results.© 2007 ASME

Interferometric CT measurement of three dimensional temperature distribution around cylinder surface

In the present study, non-intrusive interferometric technique was developed for the temperature field visualization of cylinder surfaces of melting polymer and surrounding fluid flows. Since the temperature is determined as the integration of refractive index, neither span wise temperature distribution nor temperature around the curved surface could be obtained by the conventional interferometers. For such distributed fields, computed tomography is one of the significant techniques that makes an internal structure clear and facilitates the understanding of the volumetric structure in fluid. The interferometer and thermocouple were firstly compared to assess the validity of the present technique and both measured results agreed well. The technique was applied to the tomographic measurement of metal cylinder with angular temperature gradient.