Archive of Mechanical Engineering

Rising technical standards of customers, legal requirements and the trend to minimize maintenance effort raise the thermal, mechanical and tribological loads on components of combustion engines. In this regard, emphasis is laid on improving the piston ring - cylinder liner tribosystem, one with the highest energy losses. An efficient performance has to be guaranteed during its lifetime. Tribological investigations could be carried out on engine test benches, but they are highly cost-intensive and time-consuming. Therefore, a damage-equivalent test methodology was developed with the analogous tribological model, "ring-on-liner". The research was carried out under two characteristic operating conditions. One with a "standard" operating system, modelled in line with ideal lubrication conditions, and the other "extreme abrasive" operating system, typical to a system running on a lubricant contaminated by abrasive particles. To optimize the tribological loading capacity of the cylinder liner, with focus on these two operating conditions, numerous nitride coatings have been investigated. The key aspects being seizure resistance, running-in characteristics and long term wear behaviour.

Hydrodynamic three tilting-pad journal bearing is analyzed in the paper. It is shown that, when assembling that type of not controlled bearing, it is impossible to obtain a small clearance between the pad and the journal at high frequency of journal rotation. In a static state, i.e. when the journal is immobile, such a bearing should be assembled with a large interference between the pads and the journal in order to guarantee the small clearance at rotation. At start, when the hydrodynamic lubricating wedges between the pads and journal are absent, the bearing would work with dry friction, resulting in quick wear of pads and high load of the drive motor. Apart of that, it is impossible to control the power consumption and temperature regime neither for idle nor for working rotation of the journal. The proposed automatic control gives a possibility to regulate the clearance between the pads and the journal by measuring and controlling the axial force of the pad load, and in such a way to improve work conditions of the bearing.

The paper deals with experimental investigations of a set of metal "2-delta" gaskets of different depth. The gaskets were examined under assembly conditions, i.e. placed in their seats and loaded with the compressive assembly force with no operating pressure applied to the closure. The electric resistance wire strain gauges were used to measure the circumferential and axial strains at the inner cylindrical surface of the gaskets. The plastic deformations of the contact surface of the seats were measured after disassembly of the closures. The material tests were carried out to determine real mechanical properties of materials applied for the gaskets and the seats. The results of experiment were compared with the analytical approach. The plastic deformations were taken into account in the analytical solution of the contact region between the gasket and the seats. The results of experiment and analytical approach were verified by FEM calculations, which take into account linear hardening of the material, friction and contact effects.

In this paper, the authors present a robot for pipe inspection and exploration, which has in its structure a module for the maintenance of a constant pressure force between the robot's wheels and the inside diameter of the pipe. The paper starts with a short introduction about necessity of the presented solution followed by design aspects and finalizing with the test of the developed compliant module.

The Variable Frequency Drive (VFD) is used to control the speed of the pumpmotor to attain the desired flow rate and fluid level in a fluid system. An AC drive provides efficient flow control by varying the pump-motor speed. The comparison of energy requirements and costs in a system where a throttling device is used for flow control on a centrifugal pump with the power used when an variable frequency drive (VFD) is used to control the same flow, evidently shows potential savings. In this system, AC Motor Frequency drive and static pressure transmitter, turbine type flowmeter and Analog/Digital cards, micro-control unit and computer connection are designed specially to control flow rate, fluid flow type (turbulence or laminar) and water level at the different conditions with different PID parameters.

An elaborate study executed in the direction of exploring energy saving potential shows that more than 20% of electrical energy used in industry is used for pump systems. Experts calculate that more than 30% of this energy can be saved by improving control and diagnosis for pump systems. Unfortunately, the application ratio of such system is small and consequently a large demand for such technological advanced systems can still be observed in the pump industry. Because of this reason and still growing demand of saving energy in industry, two Universities in Germany and Switzerland together with leading German pump manufacturer decided to join their knowledge and skill to work on the project called "Smart Pump". This paper presents one of the first results of this project, which goal is the development of future control methods and diagnosis systems for intelligent pumps.

In this paper, the author presents the possibility of using phase trajectory for detecting damage in an axial piston pump. The wear on main part of pump elements, such as the rotor and the valve plate, was investigated, and phase trajectories were determined based on vibration signal measured in three directions on the pump's body. In order to obtain a quantitative measure of the analyzed trajectory, the At_{p,i} parameter was introduced, and the relation between this parameter and the wear on the pump's parts was determined.

In this paper, the author compares the of characteristics of subsystems obtained by the approximate and exact method in order to answer to the question - if the approximate method can be used to nominate the characteristics of mechatronic systems. Frequency - modal analysis has been presented for a mechanical system, i.e. transverse-vibrating clamped-free beam. Consequently, the model of the beam was presented in a five-vertex hypergraph. This model, in the case of approximate frequency-modal analysis, can be imitated in a three-vertex hypergraph. Such formulation could be the introduction to synthesis of transverse-vibrating complex beam systems with constant cross-section.