| Abstract [eng] |
For the purpose of improvement of physical and mechanical qualities of natural leather, a mechanical softening process is applied. A number of particular softening technologies can be used, i.e. by means of a vibration punch, or using rotating shafts in flow machines, etc. The main issue encountered in the process of leather softening is unavailability of metering tools for determination of softening effect. Softness of leather is determined based on it’s rigidity, while the rigidity is calculated on the basis of measuring relation elongation at a certain tensioning. For the purpose of assessment of leather softness, or, to be more precise, relational fluidity, two experiments have been performed on 113 samples of softened leather, i.e. volume-based dual-axis tensioning and single-axis tensioning. Graphical rendering of the dependence of the relational fluidity, measured according to the principle of volume-based dual-axis tensioning, S0, on the thickness of leather has shown that the samples could be classified under two categories. For this purpose, a structural-change problem had to be resolved. As more possible structural change-points were identified, the structural-change problem was resolved two times more. The calculations have resulted in mean values and dispersion range values (point values and range values), as well as relevant correlations for the groups of the samples. All the sample range measured using volume-based dual-axis tensioning have shown a dispersion of relative fluidity value, S0, below that when measured using single-axis tensioning, S1. Reliability ranges of relative fluidity mean and dispersion values for S0 samples range are more narrow compared to that of the S1 samples range. The outcome has also shown that average square deviation of relative fluidity measurement performed using single-axis approach exceeds that of measured using volume-based dual-axis tensioning. Therefore, volume-based dual-axis tensioning is to be treated as a more accurate technique, yielding more reliable results. Most of the cases have shown a slight negative correlation between the thickness of the sample and relative fluidity. It is nor possible to assert that the thicker is the sample the power is it’s fluidity value, as fluidity in fact is dependent on some other qualities of leather as well. Furniture manufacturers who use natural leather for upholstery purposes should more rely on relative fluidity values obtained through using volume-based dual-axis tensioning, as this approach resembles the load on leather in the actual use of furniture in the closest manner. |
