Key Engineering Materials Vol. 685

Abstract: This paper presents the thermophysical model of crystallization of the coating at the conditions of imperfect contact between the coating and sunstrate. The model takes into account the heat exchange of coating with the environment and with the substrate. The influence of thermal resistance of the interface and concentration of filler in the coating on the change of temperature during cooling is investigated.

Abstract: In the paper the results of Lamb wave ultrasonic technique for evaluation of AA2024T3 specimens during tensile testing are presented. Three piezoelectric transducers (PZT) used as an actuator and two sensors were glued on the specimen surface using epoxy adhesive. Two frequencies of testing signals (50 kHz and 335 kHz) were used. The set of static tensile tests were performed. The recorded signals were processed to calculate the informative parameters to evaluate the changes of the stress-strain state of the specimen and its microstructure.

Abstract: Experimental results of Lamb wave technique investigation for evaluation of fatigue state of AA2024T3 specimens under cyclic loading conditions are presented. Analysis of acoustic signal data obtained by the piezoelectric transducers network was done through the calculation of two parameters: maximum envelope and 2^nd central moment. Understanding of relations between acoustic signals features and emergent damages will provide the ability to determine the state of the structure and evaluate the defects, therefore assume the preventative measures and avoid accidents.

Abstract: In this article, selective laser sintering of fine metal powder of pure Ni with the size fractions 56 ... 80 microns was conducted. Algorithm development process of laser sintering of fine powders was created, allowing to obtain defect-free samples. Investigation of the material structure of obtained samples was carried out.

Abstract: The paper describes a method of pattern cutting of sheet articles using the elastic medium pressure. Research works have been conducted into feasibility of the suggested pattern cutting using finite element simulation method. The experimental research was conducted into deformation processes during rotational separating stamping of sheet articles by means of elastic medium pressure so that to confirm relevance of the mathematical simulation results. The optimum design process parameter value combinations have been determined for implementing the rotary pattern cutting process.

Abstract: In this paper, the isothermal model of the initial stage of ion implantation process taking into account internal boundary is presented. It is assumed that implantable impurity generates mechanical perturbations. These waves can propagate with different velocities before and after the border. The examples of the waveform evolution at transition across the boundary for different combinations of the model parameters are presented.

Abstract: The paper considers issues of a mathematical model development of a “deformation zone - main electric drive” concerning hot plate mills. The dependence of the calculation of rolling torque on features of high deformation zone is given. Based on the obtained expressions, the structural diagram of the deformation zone model has been developed. The paper specifies the structure of the mathematical model for electric drive speed control system based on the known equations of synchronous motor. After the comparison of the transient processes of the electric drive coordinates and rolling settings obtained at the modeling and oscillography at the mill the conformity of the developed model to the studied object has been proved. The provided mathematical model is recommended to analyze the dynamic percussion leads that occurred at hot plate mill. The model obtained allows it to improve the reliability of the electromechanical system owing to the adaptation of the rolling schedule at the real-time operation mode.

Abstract: A new system for converting combustion heat into electric power was proposed on the basis of countercurrent burner with thermoelectric element embedded in a wall separating incoming fresh mixture and combustion products. The wall serves as heat exchanger between combustion products and the fresh mixture. Numerical simulations showed that almost whole combustion heat may be transferred through the thermoelectric element in such system and the total thermal efficiency attained a value close to the conversion efficiency of the thermoelectric device itself.

Abstract: In this paper, contact conditions between cutting tool and work material, strength of cutting tool are analyzed. Experimental and theoretical studies of contact load distribution on the artificial flank wear-land that appears on the cutter in a free orthogonal turning disk of titanium alloy (Ti-6Al-2Mo-2Cr) are described. Calculations of internal stresses by the method of finite elements show that for the sharp cutter the main stresses into cutting wedge near to the cutting edge are compression stresses, very large (10 000 MPa) and exceed ultimate compression stress for cemented carbide. Decreasing of main stress with appearance of wear on the flank explains ability working of cutter even at large wear on the flank. Increasing of cutter’s break off probability with appearance of large wear on the flank is explained by increasing of zone where the internal stresses are large enough (more or equal 3 000 MPa) and increasing of defects probability into this zone, which serves as source of cracks. Abbreviation and symbols: m/s – meter per second (cutting speed v); mm/r – millimeter per revolution (feed rate f); MPa – mega Pascal (specific contact load as stress σ or τ); h_f – the width of the flank wear land (chamfer) of the cutting tool, flank wear land can be natural or artificial like in this paper [mm]; x_h – distance from the cutting edge on the surface of the flank wear land [mm]; σ_h – normal specific contact load on the flank land [MPa]; τ_h – shear (tangential) specific contact load on the flank land [MPa]; HSS – high speed steel (material of cutting tool); P_{y r} – radial component of cutting force on the rake face [N]; P_z – tangential component of cutting force [N]; γ – rake angle of the cutting tool [°]; α – clearance angle of the sharp cutting tool [°]; α_h – clearance angle of the flank wear land [°]; b – width of a machined plate or disk [mm]; σ_-UTS - ultimate compression stress [MPa]; σ_UTS - ultimate tensile stress [MPa].

Abstract: The article presents data on dependence of the myocardial electrical impedance on the temperature. These data have high clinical relevance because radio frequency energy-induced destruction of the myocardium in the course of surgical treatment of cardiac arrhythmias should be performed transmurally. Insufficient transmural myocardial damage results in recurrence of cardiac arrhythmias. Therefore, achieving transmural treatments of the myocardium is of high significance.Studies were performed by using 20 isolated hearts. To evaluate the effectiveness of radio frequency exposure, we studied two temperature settings: myocardial normothermia (36.6 °C) and myocardial hypothermia (20 °C). The depth of destruction as well as the temperatures of the epicardial, endocardial, and intramural myocardium at the points of impact were estimated. Data showed that lower temperature decreases tissue electrical impedance and results in a greater depth of damage.