Rigid polyurethane (PUR) foam is products used as a biomedical material for medical device testing. Thermal stability is a very important parameter for evaluating the feasibility of use for testing surgical instrument load during drilling. This work aimed to perform experimental measurements to determine the dependence of the mechanical properties of a certified PUR on temperature, strain rate and density. Experimental measurements were realised for three types of the PUR samples with different density 10, 25 and 40 pounds per cubic foot. The samples were characterised in terms of their mechanical properties evaluated from tensile and compression tests at temperatures of 25 °C, 90 °C and 155 °C. Furthermore, the structures of the samples were characterised using optical microscope, their thermal properties were characterised by thermogravimetric analysis, and their density and stiffness with the effect of temperature was monitored. The results show that it is optimal not only for mechanical testing but also for testing surgical instruments that generate heat during machining. On the basis of experimental measurements and evaluations of the obtained values, the tested materials are suitable for mechanical testing of medical devices. At the same time, this material is also suitable for testing surgical instruments that generate heat during machining.

The purpose of this study was to experimentally measure and simulate thermal diffusion in the surrounding of specific dental drills with cylindrical and conical drills. The investigation was performed under different drilling conditions, with and without cooling and at different revolution speeds. During the experimental investigation, drilling into a polyurethane (PUR) foam block, was performed with and without cooling, and at three different revolution speeds, 800 rpm, 3,000 rpm and 5,000 rpm. Finite element method (FEM) simulation of the thermal diffusion during drilling into PUR foam was also performed. As a result, different temperature diffusion was found in the surroundings of the individual drills. During specific drilling conditions, some of the drills produce very high heat, as opposed to the other tested drills. The results from the numerical FEM analysis are consistent with the experiments, and it is evident that the shape of the drill and the drilling conditions affect the results. The measurements in our experiment were performed under specific conditions that resembled mechanical drilling and did not match the reality of drilling in dental surgery, which is very often interrupted and the drilling force is reduced by the dentist’s hand. The actual temperature is probably much lower. The finite element (FE) analysis of temperature rise during drilling can be useful for shape optimization of the drill when the target function is lower in temperature.

Rigid polyurethane (PUR) foam, which has an extensive range of construction, engineering, and healthcare applications, is commonly used in technical practice. PUR foam is a brittle material, and its mechanical material properties are strongly dependent on temperature and strain rate. Our work aimed to create a robust FE model enabling the simulation of PUR foam machining and verify the results of FE simulations using the experiments’ results. We created a complex FE model using the Arbitrary Lagrangian–Eulerian (ALE) method. In the developed FE model, a constitutive material model was used in which the dependence of the strain rate, damage initiation, damage propagation, and plastic deformation on temperature was implemented. To verify the FE analyses’ results with experimentally measured data, we measured the maximum temperature during PUR foam drilling with different densities (10, 25, and 40 PCF) and at various cutting speeds. The FE models with a constant cutting speed of 500 mm/s and various PUR foam densities led to slightly higher T${}_{max}$ values, where the differences were 13.1% (10 PCF), 7.0% (25 PCF), and 10.0% (40 PCF). The same situation was observed for the simulation results related to various cutting speeds at a constant PUR foam density of 40 PCF, where the differences were 25.3% (133 mm/s), 10.1% (500 mm/s), and 15.5% (833 mm/s). The presented results show that the ALE method provides a good match with the experimental data and can be used for accurate simulation of rigid PUR foam machining.

In studies testing the effect of hippotherapy on the human body, no one has yet compared the involvement of the same specific muscles in exercises on a gymnastic (pommel) horse vs. a walking horse. To improve the correct riding seat and to compare the differences in electromyographic activity, we conducted an experimental study to measure the activity of selected muscles on a set of probands of both sexes during three exercises on a gymnastic horse vs. a walking horse. We measured the activity of eight selected muscles, expressed as the percentage value of the maximal voluntary contraction. Maximal voluntary contraction of each muscle was electromyographically measured using Janda’s strength muscle test. These values were used as a standard for values obtained from exercising on a gymnastic horse and a walking horse. The effect of the studied factors was tested by analysis of variance. The muscle activity was statistically significantly affected by the studied factors. It was higher when riding a living horse than a gymnastic horse and in females compared to males. Although the exercises on a gymnastic horse generated lower muscle activity than those on a walking horse, there was a variation among individual muscles that justified further study.