Department for Vibration and Thermal Strength Research

Head of Department:
Doc. Sci. (Eng.), Professor

Shulzhenko Nikolai Grigorievich

E-mail: shulzh@ipmach.kharkov.ua

Department for Vibration and Thermal Strength Research

The Department was founded in 1996 and based on the Department for Thermal Elasticity and Creep of Machine Parts, which was created in 1972 together with the founding of IPMash NAS of Ukraine. At the time of setting up the Department, its key staff were trained in Academician A.P. Filippov's scientific school. Till 1996, the Department was headed by A.N. Podgorny, Academician NAS of Ukraine. The Department is staffed with 14 persons, including 2 Doctors and 7 Candidates of Science. The scientific and applied research results of department employees are reflected in 7 monographs and numerous articles in scientific journals. The department has prepared 24 Candidates and 1 Doctor of sciences.

Main research topics

  • Thermal strength of machine elements
  • Structural dynamics
  • Diagnostics and resource of rotor units

Basic research

  • Dynamics, strength and service life of power machinery
  • Diagnostics of the vibration and thermal stress state of machines and structures

Applied research

  • Method and hardware for vibration diagnostics of rotor units
  • Dynamics of spatial structures of machines and apparatus
  • Analysis of strength and durability of steam turbine and internal combustion engine components
  • Analysis of vibrations and strength of hydraulic turbine components
  • Strength analysis and optimisation of thoroidal electrophysical units
  • Dynamic and strength of spacecraft systems units
  • Evaluating the residual resource of power machinery

COMPLETED RESEARCH

1. Techniques and computer programs based on the finite-element method (FEM) for solving the following problems:

analysis of nonstationary thermal fields and the stress-strain state in plane and axisymmetrical structural elements with considiration of contact interaction, plasticity, creep and material fatigue

analysis of nonstationary thermal fields and the stress-strain state of 3D structural elements in the Cartesian and cylindrical coordinate systems with considiration of contact interaction, plasticity, creep and material fatigue

analysis of free and forced vibrations and dynamic compliance of spatial rod structures

• analysis of fracture strength of structural elements based on the mechanics of brittle failure with account of non-standard loading conditions

analysis of 2D electromagnetic fields and additional losses of synchronous turbo generator rotors under different operating conditions

2. Software for stress-strain state 3D analysis, natural frequencies and modes of constructions with cracks based on multigrid FEM.

The software has an advanced input and output interface and units for modeling of runners in Francis turbines and steam turbines diaphragms .
Prototypes of instrumentation that was tested on turbine-driven sets:

  • contactless and contact eddy-current vibration transducers (detectors);
  • contactless eddy-current relative displacement (shift) meters, vibration displacement meters and rotor speed meters with appropriate signal digital convertation;
  • device for measuring the twist angle by marks on the shafting.

3. Automated system for analysis and diagnostics of the rotor vibration state for preventing occurrence of emergencies, increasing the reliability and operational safety.

4. System for diagnostic of thermal stress state and resource work-out of high-temperature rotors (resource counter)

    Resource counter is used for diagnostic of thermal stress state and estimation of resource work-out of high-temperature rotors by actual regimes of turbine work. These regimes are determined by parameters of automated control system of technological processes (ACS TP). The work-out resource estimation is performed due to continuous computer modeling of thermo-mechanical processes in high and middle pressure cylinders of turbine during operation.
    Resource counter is provided with graphical interface (fig. 1), which shows resource work-out at the moment. Also it shows the evaluation in time of temperature and stress in zones of diagnostic during day.
    Resource counter working stages:
      - experimental-calculated determination of steam parameters and heat exchange conditions using ACS TP data;
      - calculated determination of heat and thermal stress state;
      - formulating of load cycles and elastic-plastic deformations;
      - determination of material damage under cyclic loading and creep using the experimental curves of fatigue and durability;
      - evaluation of resource work-out.

Stopping and hot starting of turbine 10.11.2012 Graphical interface of resource counter

    Resource work-out caused by low-cycle fatigue and creep are carried out on all regimes of turbine operation. These regimes are determined by ACS TP. That’s why there are no reasons to setup thermocouples, sensors and other equipment.
    Resource counter can use not only ACS TP data but also dependences that are given in form of tables. These tables reflect the instructions of start-up and stopping regimes of turbines. This allows to estimate the influence of operation regimes on resource work-out and to make recommendations for improvements to decrease damage of rotor and to extend term of use.
    Using resource counter will let to:
      - determine the most dangerous operation regimes via stress-strain state analysis of high-temperature rotors
      - determine sparing maneuvering regimes of operation;
      - develop recommendations for optimization of start-up, stopping and maneuvering regimes of turbine. This will give fuel economy by reducing the start-up regime and will decrese resource work-out of turbine.
    Resource counter was tested on T-250/300-240 turbine on combined heat and power plant No 5 (Kharkiv). The developed technology of diagnostics of resource work-out can be used to create similar systems for other steam turbines.

5. Estimation of fracture toughness of high-temperature elements of power equipment under low-cycle fatigue and creep

    The fracture toughness estimation method of high-temperature elements of construction is developed. The elements of construction operate under cyclic loading and creep of material with the surface and subsurface cracks. The estimation method involves the numerical integration of crack growth from initial value to the critical size with multi-mode static and cyclic loading. The summation of crack growth rate of all modes is used. Crack growth rates are defined from Paris’ type equations through stress intensity factor at the crack tip or its scope. Numerical integration of kinetic equations is carried by Euler’s method with automatic step selection and control of breakaway-stop of crack. FEM analysis of stress and displacements distribution in the vicinity of crack tip is used to calculate the stress intensity factor.
    The proposed method allows to simulate various situations in multi-mode operation of power equipment with detected or hypothetical cracks taking into account non-stationary temperature fields, material aging, corrosive environment and other factors.
    The durability is defined as the time at which the stress intensity factor reaches a critical value of fracture toughness.

Evaluation of crack resistance

    It is possible to use kinetic diagram of different complexity, which take into account the asymmetry of the loading cycle, the effect of crack closure or to use the total kinetic diagram, which taking into account the thresholds of breakaway crack and accelerate its growth before the destruction.
    Designed for working and projected energy facilities.
    The estimation of fracture toughness of steam turbine rotor of South-Ukrainian NPP, root joints of blades of gas turbine GTK-10 and other devices is performed.
    The proposed method became part of the normative document of the Ministry of Energy and Coal Industry of Ukraine.
    This method will develop to use scattered damage in the material. So, there is no need to use Paris' type kinetic diagrams. Instead, the data long-term strength of smooth specimens is used.

BASIC RESEARCH

Development of mathematical models of creep in solids, considering stressed state type; the initial and strain anisotropy, the failure rate profile and other factors.

Further development of numerical methods for solving initial-boundary problems in thermal mechanics based on the FEM, implicit and explicit time integration scheme considering physical and geometric nonlinearity, thermal contact interaction, inhomogeneity and dependence of material properties on temperature and other factors.

Development of methods for analysis of crack kinetics under cyclic loading and creep considering material properties degradation.

Developing models and finite element based methods for analysis of statics and dynamics of elastic bodies that contain crack type defects and consider contact of the banks.

Development of methods and algorithms for strength analysis and optimization of helical-shaped laminated solenoids considering strength constraints and various temperature conditions.

Further development of multigrid FEM for solving contact problems in the mechanics of a strained solid with cracks.

Development of models and numerical methods for solving nonstationary 2D and 3D magnetic thermal mechanics problems for inhomogeneous medium with nonlinear dependence of magnetic permeability on field intensity and temperature.

Development of models and methods for numerical analysis of thermal contact interaction of solids under high-frequency electromagnetic action.

Development and improvement of methods, technologies and tools for rotor technical condition analysis and diagnostics by the vibration parameters.

Development of methods for automated vibration diagnostics of rotor units.

APPLIED RESEARCH

Calculations of thermal and thermal stress state, resource estimation of high-heated steam turbine components in different operating modes.

Evaluation of machinery structure units crack resistance under multi-mode loading considering abnormal loading conditions.

Numerical modeling of thermomechanical processes in constructions under plasticity and creep strain conditions with account of variable thermal force action, elements contact conditions, material properties and other factors.

Calculation of stress-strain state and the natural frequencies of Kaplan and Francis turbines impellers and details with account of crack impact on the strength and vibration characteristics.

Analysis of steam turbines diaphragms stress-strain state with considiration of contact bearing on and the impact of crack-type failures in the blading.

Analysis of strength and optimal design by strength criteria of solenoids and different types coils considering composite structure delamination in current-conducting elements.

Evaluation of stress-strain state for the quasistatic and dynamic states of rotors with contacting cracks.

Numerical simulation of two-dimensional electromagnetic fields and additional losses in the rotor of a synchronous turbo generator during a short-circuit fault and non-symmetric load.

Analysis of the process of assembling/disassembling the drill-chuck joint in drilling machine using induction heating.

Software for balancing turbo generator rotors on acceleration and balancing test bench.

Methodology and software for vibration monitoring data visualization based on vibration parameters for real-time analysis of the vibration state of turbine sets.

Technology for vibration monitoring, analysis and diagnostics of the vibration state of high-capacity turbines.