Rimantas Didžiokas

The impact of the internal welding defects on the joint strength

The paper looks at the impact of the internal welding defects on the strength of joints. The tension tests provided the values of the welded joint strength limits depending on the area of sporadic voids, slag intrusions and the field of discontinuities. Considering the results of the conducted experiments, the mathematical relationships between the strength of the welded joint and defected area were concluded. In presence of all three defects, the distance of the defects from the weld surface was measured. It is deduced that the defects nearer to the surface reduce the strength of the welded joint more than those noticed in deeper layers.

Investigation of the hydrodynamic processes of a centrifugal pump in a geothermal system

AbstractThe hydrodynamic and thermodynamic processes of geothermal well extraction are investigated and presented in this paper. The paper presents mathematical models for a multi-level centrifugal pump and pipeline system. The mathematical models were used to evaluate gas (nitrogen) emission in water and its effects on hydrodynamic processes. Experimental studies and mathematical modelling showed that the gas content of the fluid increases the pressure and flow pulsations within a centrifugal pump. The variation in the height of the liquid column in extraction has an influence on characteristics of the multistage centrifugal pump used in wells.

Dynamic Processes of Rotating System with Coupling

The article concerns dynamics and vibration of a high power rotating system with toothed wheel coupling that inserts elastic plate packets. Theoretical modeling and simulation of the rotating system with toothed wheel coupling have been provided by a finite element method. Complex model involved a rotating system, hydrodynamic bearings and coupling. The dynamics of semi-couplings and plates have been simulated. Experimental measurement of vibration has been measured with stationary machine condition monitoring and a diagnostic system.

Modeling and Diagnostics of Heavy Impeller Gyroscopic Rotor with Tilting Pad Journal Bearings

The work presents the study of dynamics of heavy impeller rotor and failure diagnostics of tilting-pad journal bearings. The started rubbing process in the bearings at resonance and increased rubbing phenomenon in both bearings by measurement of radial gaps, were identified experimentally in situ. The rotational speed was established when gravitational force became dominant compared to rotor gyroscopic force. Rotating system model was designed, simulated and verified.

Influence of the Secondary Raw Materials on the Mechanical Properties of Multilayer Films

Recycling and usage of secondary raw materials in production is one of the most topical issues. Usage of secondary raw materials is one of the most topical issues in both economic and ecological (environmental) sense. Such a layered film on the market has lower price because secondary raw material prices is significant lower compared with the original material, the PET granules. Currently producing a layered film the middle layer composes up to 50 % of recycled material. In todays market in order to maintain a high level of competitiveness usage of 50 % of recycled materials is inadequate, therefore to use more recycled material amount and in such way to reduce product cost further researches are necessary.

Equivalent mechanical parameters of oscillating rotary motors used in transport equipment

Abstract In various appliances and equipment of sundry transport means there is a lot of diverse mechanisms of periodical movement. So, the various piston or membrane pumps of fuel feeding and lubrication systems, circulation pumps, air and refrigerating coolant compressors, etc. are the typical examples of innovative and well promising application of the oscillating motors. In these cases the moving part of a motor can be directly connected to the working body of driven mechanism without the additional gears. Consequently, the drive can be simplified in design and improved in efficiency and reliability. Application of the oscillating rotary motors, if used in the aforesaid devices, strictly depends on specific properties of mechanical system of a motor aggregated with the driven mechanism and considered as the one‐piece unit on the whole. So, this study analyses how the properties of mechanical system, comprised of two moving parts interconnected eccentrically or centrically, can be evaluated by the equi...

Diagnostics Modeling of Vertical Rotor Vibration

This paper deals with condition monitoring and vibration diagnostics of vertical sulphuric acid pumps running in continuous long term operation mode. The task of experimental testing and theoretical modeling – to increase reliability and efficiency of vertical pumps through elimination of rotor lateral vibration. On the basis of experimental testing results analysis the dynamic model was designed and simulated. The reason of high vibration of the pump rotor is the rotor technological bow and cavitation phenomenon that take place in the pump.