In this paper, the basic cutting characteristics such as cutting forces, cutting power and its distribution, specific cutting energies were determined taking into account variable tool corner radius ranging from 400 to 1200 μm and constant cutting parameters typical for hard turning of a hardened 41Cr4 alloy steel of 55 ± 1 HRC hardness. Finish turning operations were performed using chamfered CBN tools. Moreover, selected roughness profiles produced for different tool corner radius were compared and appropriate surface roughness parameters were measured. The measured values of Ra and Rz roughness parameters are compared with their theoretical values and relevant material distribution curves and bearing parameters are presented.

This paper presents a comprehensive methodology for measuring and characterizing the surface topographies on machined steel parts produced by precision machining operations. The performed case studies concern a wide spectrum of topographic features of surfaces with different geometrical structures but the same values of the arithmetic mean height Sa. The tested machining operations included hard turning operations performed with CBN tools, grinding operations with Al2O3 ceramic and CBN wheels and superfinish using ceramic stones. As a result, several characteristic surface textures with the Sa roughness parameter value of about 0.2 μm were thoroughly characterized and compared regarding their potential functional capabilities. Apart from the standard 2D and 3D roughness parameters, the fractal, motif and frequency parameters were taken in the consideration.

It is well known that the magnitudes of the coefficients of the discrete Fourier transform (DFT) are invariant under certain operations on the input data. In this paper, the effects of rearranging the elements of an input data on its DFT are studied. In the one-dimensional case, the effects of permuting the elements of a finite sequence of length N on its discrete Fourier transform (DFT) coefficients are investigated. The permutations that leave the unordered collection of Fourier coefficients and their magnitudes invariant are completely characterized. Conditions under which two different permutations give the same DFT coefficient magnitudes are given. The characterizations are based on the automorphism group of the additive group Z_N of integers modulo N and the group of translations of Z_N. As an application of the results presented, a generalization of the theorem characterizing all permutations that commute with the discrete Fourier transform is given. Numerical examples illustrate the obtained results. Possible generalizations and open problems are discussed. In higher dimensions, results on the effects of certain geometric transformations of an input data array on its DFT are given and illustrated with an example.

The tribological behavior of the PVD-TiAlN coated carbide inserts in dry sliding against two-phase (α-β) titanium alloy,Ti6Al4V grade, was investigated. A modified pin-on-disc device was used to conduct experiments under variable normal load and sliding speed. Scanning electron microscopy (SEM) and X-ray micro-analyses by EDS were applied for observations of wear scars and wear products. It was revealed that the increase of sliding speed contributes to decreasing the friction coefficient under a low normal force, whereas the increase of the normal loading causes the friction coefficient is less sensitive to changes in the sliding speed and its values are equal to μ = 0.26-0.34. The adhesive nature of wear along with severe abrasive action of the Ti alloy were documented.

The aim of this study was to assess sand accumulation in the gastrointestinal tract and fecal sand excretion in Silesian foals using three diagnostic methods and taking into account the sex and age of the animals. Another aim of the study was to compare the three diagnostic methods. The study was carried out on 21 clinically healthy Silesian foals (10 females and 11 males) from 9-28 weeks old grazed on permanent pasture. The sand intake was assessed using a sedimentation test, abdominal ultrasonography and a quantitative evaluation of sand per 100 g of stool. In the sedimentation test, the sand was palpable in the stool of 57.1% of the horses, and clearly visible in 42.9% of the animals. The ultrasound examination revealed the presence of sand in the gastrointestinal tract in 66.7% of the horses. It was limited to a single location in 60% of the horses, while it was present in several regions in 40% of the horses. The mean amount of sand was 0.14 ± 0.33 g per 100 g of stool. It did not exceed 0.1g in 71.4% foals, while it ranged from 0.1-0.5 g in 23.8% foals. In 4.8% of the animals, it amounted to 1.6 g per 100 g of stool. There was no correlation between age and gender and the results. There was a positive correlation between the ultrasound examination and the sedimentation test.

Sand may be accumulated in the gastrointestinal tract of foals without any clinical signs. The amount of sand excreted in the stool is not an indicator of the amount of sand accumulated in the gastrointestinal tract. An abdominal ultrasound examination should be combined with a sedimentation test for more specific results.