Naoya Hamada

Laser heat sealing of the polymer coated steel sheet

The polymer coated thin steel sheet is widely used for materials requiring the heavy corrosion resistance. The surface of this material has strong corrosion resistance, however, the edge or joint section should be sufficiently sealed off against the environment to prevent rusting. The tight rolling of the sheet edge is one of the sealing techniques. In this study, we applied the laser heat welding of polymer in order to enhance the sealing performance. The influence of processing parameters such as the laser wavelength, energy density was examined using the PET film coated (Ni plated) steel sheet. By optimizing the laser parameters, rusting in the roll joint was successfully prevented in accelerated corrosion test.The polymer coated thin steel sheet is widely used for materials requiring the heavy corrosion resistance. The surface of this material has strong corrosion resistance, however, the edge or joint section should be sufficiently sealed off against the environment to prevent rusting. The tight rolling of the sheet edge is one of the sealing techniques. In this study, we applied the laser heat welding of polymer in order to enhance the sealing performance. The influence of processing parameters such as the laser wavelength, energy density was examined using the PET film coated (Ni plated) steel sheet. By optimizing the laser parameters, rusting in the roll joint was successfully prevented in accelerated corrosion test.

Mechanism of anisotropic stress generation in laser peening process

The purpose of this work is to investigate mechanism of anisotropic residual stress generation in laser peening. Residual stress induced by multiple pulse irradiation is simulated using stress distribution of single pulse. Contribution of each irradiation spot to the stress field is assumed to be additive, and the Mises yield condition is considered as constraint for the field addition process. The result explains well the anisotropic stress generation. The model can be applied to optimize the residual stress field.The purpose of this work is to investigate mechanism of anisotropic residual stress generation in laser peening. Residual stress induced by multiple pulse irradiation is simulated using stress distribution of single pulse. Contribution of each irradiation spot to the stress field is assumed to be additive, and the Mises yield condition is considered as constraint for the field addition process. The result explains well the anisotropic stress generation. The model can be applied to optimize the residual stress field.

Study of metal drilling characteristics with Q-switched CO2 laser

In spite of recent rapid progress of high power solid state laser, CO2 laser systems are still useful for metal drilling with hole diameter of about 100 µm and depth of several tens of µm, because it requires large pulse energy of about 100 mJ with high beam quality. Mechanically Q-switched CO2 laser systems are favorable for such application with high repetition rate (>10 kHz) [1,2] and have the advantage of cost performance.In spite of recent rapid progress of high power solid state laser, CO2 laser systems are still useful for metal drilling with hole diameter of about 100 µm and depth of several tens of µm, because it requires large pulse energy of about 100 mJ with high beam quality. Mechanically Q-switched CO2 laser systems are favorable for such application with high repetition rate (>10 kHz) [1,2] and have the advantage of cost performance.