**Preface**

This reprint contains 14 articles published in the Special Issue, "Use of Modern Materials in Technological Processes Accompanied by Frictional Heating".

Analytical one-dimensional models of unsteady heat generation due to friction in the tribosystem of two semi-bounded bodies made of FGM have been developed [1-6]. The key assumptions of the models relate to how the thermal conductivity exponentially increases as the distance from the contact surface increases; meanwhile, these models meet the conditions for perfect frictional thermal contact. The exact solutions for the corresponding boundary-value problems of heat conduction were obtained using the mathematical apparatus of the Laplace integral transform. Cases of slipping with a constant specific power of friction [1] and its time profile, taking into consideration the time of the contact pressure increase [2], were considered. The influence of the thermal sensitivity of the FGM components on the temperature field, which resulted from friction during single braking with constant deceleration, was investigated [3]. An analytical model was proposed to determine the temperature of a friction system containing one homogeneous element and the other made of FGM [4]. A methodology for determining the heat partition ratio in a friction couple made of FGM was developed [5]. This methodology was adapted to determine the maximum temperature of the disc brake system operating in a repetitive short-term (RST) mode of operation [6]. The influence of the flash temperature on the maximum temperature during RST braking in a system that consists of two elements made of homogeneous materials was investigated [7].

A comparative analysis of the railway brake temperature modes was carried out using axisymmetric (2D) and spatial (3D) numerical models with FEM [8].

Appropriate numerical models for railway solid and ventilated brake discs have also been developed [9].

The effect of adding a carbon-containing additive to the friction material of the wet clutch on the temperature generated by friction has been studied [10]. For the same system, the effect of ceramic and intermetallic powder additives on the tribological properties and temperature field was also investigated [11].

The problem of the identification of the unknown temperature for frictional heat generation in a cylindrical tribo-couple was analyzed [12].

An approach to determine the stress state of bi-material structures with interfacial homogeneous ribbon-like deformable inclusions has been proposed [13]. The influence of FGM on the stress–strain state of ribbon-reinforced composites was investigated as well [14].

### **Aleksander Yevtushenko and Michal Kuciej** *Editors*
