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Contact damage of glass is one of the most crucial issues for glass products. To develop strong and tough glass products and to compare damage resistance among glass compositions, a simple method for evaluating the mechanical response of glass during contact is required not only for glass mechanists but also for glass customers and suppliers. Although it is well known that the quasi‐static Vickers indentation test is one of the simplest and most useful methods to evaluate hardness and brittleness in glass, the indentation response of glass under the indenter at higher impact velocities remains to be quantitively understood because of the difficulty of measurement and limited experimental works. In this study, therefore, the dynamic indentation behavior of soda‐lime glass is evaluated by using a lab‐made free‐drop indentation set‐up with the coils for detecting electromotive forces (EMFs). The cono‐spherical indenter made of tungsten carbide attached with a neodymium magnet was employed to generate the EMFs when the indenter passed through the coils located near the glass sample. The impact load versus indentation depth curve during the impact within a few tens of microseconds was successfully obtained both for an elastic contact and for an inelastic contact. Under an elastic condition, where no residual indent nor any cracks were left on the glass surface after the test, it is confirmed that there is almost no hysteresis in the impact load versus indentation depth curve and that the curve can be reproduced by the Hertzian analytical solution. Under an inelastic condition, on the other hand, it is found that the hysteresis in the impact load versus indentation depth curve stems from inelastic phenomena, such as plastic deformation (shear flow and/or permanent densification) and cracking. These results suggest that the dynamic indentation technique based on electromagnetic induction phenomena is a useful and effective tool for evaluating the mechanical responses of glasses during the impact. [ABSTRACT FROM AUTHOR]

We developed a far-infrared spectroscopic ellipsometer for measuring the complex permittivity of high-permittivity materials in the terahertz (THz) region and demonstrated the dielectric function of SrTiO3 single crystal at 0.75-21 THz. The responses of the Slater, Last, and O6 displacive modes, which are all optical phonon modes of SrTiO3 at room temperature, were clearly observed. The complex permittivity measured by the ellipsometer agreed with the permittivity simulated by a damped harmonic oscillator model. The far-infrared spectroscopic ellipsometry is useful to analyze the phonon modes of high-permittivity materials, which enable us to understand the contribution of the ionic polarizations to the low-frequency permittivity. [ABSTRACT FROM AUTHOR]