Oblique impact of ice hockey and plastic pucks with a rigid surface

The collision of a disk with a rigid surface is analysed in this paper assuming that the disk slides throughout the collision at glancing angles or grips the surface at other angles of incidence. Experimental results are presented for an ice hockey puck and a plastic disk, showing that there is no rolling involved, as assumed in previous studies. Measurements are presented of the outgoing speed, angle and spin as a function of the angle of incidence, and the results are described in terms of the normal and tangential coefficients of restitution plus the coefficient of sliding friction. The experiment would be suitable for use in a student laboratory.

Tadeusz Krwawicz, MD: The inventor of cryosurgery in ophthalmology

Tadeusz Krwawicz (1910–1988) pioneered the use of cryosurgery in, as ophthalmology. The idea arose in 1959 while experimenting because on lyophilization to store corneas and lenses for transplantation it was difficult to remove the lens without damage the capsule was usually torn. Subsequent experiments on rabbits revealed that touching the lens with a wire cooled to 203°K (–70°C) resulted in firm attachment of the lens capsule and subcapsular masses. A cryoextractor was developed and employed for clinical use in cataract extraction, likewise in intumescent cataracts and lens subluxation. Cataract surgery utilizing cryoextraction led to substantial progress to ophthalmology by reducing the number of complications, particularly capsule rupture, and resulted in achieving better outcome compared to other methods. This surgery soon and for almost 20 years became a routine method used all around the world in cataract removal. Simultaneously, Krwawicz developed techniques for corneal refractive surgery—partial lamellar removal of the corneal stroma and temporary interlaminar introduction of a plastic disk in order to change the corneal curvature. Krwawicz presented other ophthalmic interests—his research concerned immunology, histology, histochemistry, biochemistry of ocular tissue, and mainly corneal and experimental surgery with a particular focus on the pathology of the cornea.

Study on Photoelastic Method for Measuring Elastohydrodynamic Lubrication Pressure in Line Contact

In the present paper, a new method for measuring elastohydrodynamic lubrication (EHL) pressure in line contact is proposed, which is based on the photoelastic technique. The pressure distribution of EHL film and the inner stresses in the friction pairs are fundamental issues to carry out EHL research. The film thickness, pressure and temperature have been successfully obtained with solving the basic equations such as Reynolds equation and energy equation simultaneously or separately, with numerical model of EHL problem. The film thickness can be also measured with the optical interference technique. However, the pressure measurement is still a problem which has not been well solved yet, so as the inner stresses inside the friction pairs. With the experimental mechanics, the photoelastic technique is a possible method to be used for measuring the pressure distribution of EHL film and inner friction pair in the line contact. Therefore, A flat plastic disk and a steel roller compose the frictional pairs of the photoelastic pressure measuring rig with combining the monochromatic LED light source, polarizer CCD camera and stereomicroscope to form the whole pressure measuring system of the line contact EHL. The experimental results with the rig display the typical features of EHL pressure. This shows that the method is feasible to be used for measuring the pressure of EHL film and the inner stresses of the friction pairs in the line contact.