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Results of numerical analysis of the influence of pulse shaper geometry on wave signals in the split Hopkinson pressure bar experiment are presented. Five pulse shapers, i.e. square, ring, cross, star and disk ones have been analysed. It has been assumed that the disc pulse shaper is the reference geometry to assess the remaining types of pulse shapers. The results of numerical analyses have shown that pulse shapers with shapes different than disk are highly capable of minimizing high-frequency Pochhammer-Chree oscillations and, thus, reduce dispersion of waves propagating in the bar. The greatest damping ability has been observed while using the ring pulse shaper at both low and high impact velocities of the striker.

The simple method of determining thermal diffusivity of solid materials at room temperature using the pulsed infrared thermography (IRT) is proposed. The theoretical basis of the method and experimental results are presented. The study was conducted on austenitic steel 316L. The obtained results show that the thermal diffusivity value of the tested steel determined by means of pulsed infrared thermography is very approximate to the values given in the literature, obtained by using more complicated methods. The differences between these values are 0.5%.Keywords: thermal diffusivity, pulsed infrared thermography, heat conduction, austenitic steel W niniejszej pracy przedstawiono prostą metodę wyznaczania dyfuzyjności cieplnej ciał stałych w temperaturze pokojowej przy wykorzystaniu aktywnej termografii podczerwieni. Zaprezentowane zostały teoretyczne podstawy metody oraz wyniki badań doświadczalnych. Badanie przeprowadzono dla stali austenitycznej 316L. Otrzymane rezultaty pokazują, że wyznaczona wartość dyfuzyjności cieplnej badanej stali jest bardzo bliska wartościom podanym w literaturze, otrzymanym za pomocą bardziej skomplikowanych metod. Różnica między tymi wartościami sięga zaledwie 0,5%.

The results of experimental and numerical analysis of the influence of the non-axisymmetric pulse shaper position on recorded wave signals in the split Hopkinson pressure bar experiment are presented. The paper focuses attention on the problem of wave signal disturbances caused by a bending wave resulting from non-axisymmetric pulse shaper positions and, moreover, different shaper thickness, striker impact velocities and Wheatstone bridge configurations. The obtained results of analyses indicate that the effect of the non-axisymmetric pulse shaper position may be neglected if deviation from the bar axis does not exceed 20%.

The problem of specimen geometry imperfections for ductile materials in the split Hopkinson pressure bar (SHPB) experiments is presented in this paper. Impact of five types of imperfections most frequently encountered in experimental practice and the resulting errors in the position of the specimen in relation to the axis of the bars on the reflected and the transmitted wave profile and on the shape of the stress-strain curve was analysed. The problem was considered based on numerical analyses using a finite element method. It was found that imperfections disturb mainly the beginning and end portions of the reflected and transmitted pulses, which is reflected in the stress-strain curve profile. However, for ductile materials, influence of specimen geometrical imperfections is small, and therefore the SHPB experiments results can be considered reliable from a practical point of view. In the case of all the analysed imperfections, it can be assumed that for imperfection angles α ≤ 0.3°, errors in determination of the stress-strain curves can be omitted.