森田 昇

The final goal of this research is to construct a laser processing system to manufacture stepped shapes or free-form surfaces using the information of detected laser processing sound. In order to achieve this goal, basic investigations concerning the analysis of the characteristics of laser processing sound are necessary. The purpose of this report is focused on the analysis of the frequency characteristics of a detected sound of a single pulse laser beam, and to clarify those of a continuous pulse laser beam by calculation.

A radiation of the electron called exoelectron from the machined surface is observed with less energy than usual work function, and it is known that this phenomenon is sensible to changes of crystal structure and surface structure. This paper describes the result of examining the possibility of photo stimulated exoelectron emission as a method of the process monitoring and surface evaluation. As a result of cutting experiment in vacuum atmosphere, it is confirmed that electron emission is observed during the distruction of materials and that there is a relationship between cutting conditions and emission behavior on the machined surface. These results show the possibility of exoelectron emission for new method of process monitoring and surface evaluation.

Laser processing is an important manufacturing technology in machining difficult-to-cut materials. It is known that a sound is generated when laser processing is carried out, the intensity of the sound changing according to the processing conditions. The purpose of this research is to clarify experimentally the relationship between the material removal characteristics and the pressure level of the processing sound when a low and a high frequency laser beam are applied to the processing of ceramic materials.

This report describes molecular dynamics simulations of tensile tests of single crystal pure iron. There are a few experimental data of plastic region tensile tests of pure iron. In this simulation, strain range are elastic and plastic region, and to fracture point and temperature conditions are 100K to 1100K.In this report, different three kinds of models of tensile directions ([001], [011] and [111]) are used. They are axis of rotational symmetry of bcc-type crystals. In the simulation results, stress-strain diagrams are important. They are different from polycrystal iron's in macro-scale. The stress-strain diagrams differ from tensile directions and temperatures. In tensile tests of [001] and [011] directions, we find second elastic regions after plastic regions. In second elastic regions, crystal structure types are changed from bcc-type. We find two types of structure phase transitions.

This report describes simulations of uniaxial tensile tests of single crystal pure iron using molecular dynamics and proposal of new calculation method of Young's modulus of polycrystal pure iron. There is a few experimental data of tensile properties of pure iron.In the simulations, tensile directions are [001], [011] and [111], which are axis of rotational symmetry of bcc-type crystals and temperature conditions are 100K-1100K. As results, we have tensile properties, especially stress-strain diagrams are important..From this, Young's modulus of single crystal pure iron are calculated. Young's modulus are different from tensile directions and tend to lower value in high temperature.We propose new calculation method of Young's modulus of polycrystal iron.It is the average of young's modulus of single crystal pure iron.