FINITE ELEMENT ANALYSIS ON DYNAMIC CHARACTERISTICS OF THE BUILDING FRAME

The article deals with the study of the dynamic characteristics of the building frame by finite element method, using the method of regulating the stiffness of the system. The spectrum of frequencies and forms of natural vibrations of the building frame is obtained. The pulsation component of the wind load on the two main axes of the building is determined and a static calculation is made taking into account this load. Different variants of the frame modeling differed in the thickness of floor slabs and stiffening diaphragms. Variation of the geometric characteristics of the elements of the frame of the building allowed to choose the best option of the design scheme. The level of dynamic comfort is estimated by the results of the analysis of acceleration of the upper floor of the frame.

Presentations in FAM-C And FDM-A Methods and Some Problems of a Signals Theory

The FDM-A diagnostic method [2, 4] based on a frequency modulation measurement of a pulsation component as well as the FAM-C method of an alternating current frequency have been elaborated in Air Force Institute of Technology. These methods to define a level of an assembly abrasive wear as well as its localization during a normal work of a power unit. A diagnostic signal is derived from onboard generators or alternators. Each damaged part of the generator’s or alternator’s power unit is a vibration generator or modulator. The vibration is turned into oscillation in onboard generators or alternators. After many years of the FAM-C and FDM-A methods’ using it is possible to localize and define value of many faults of power units: a coupling eccentricity, a shaft skew, extender longitudinal clearances of turbine engine’s rotor assembly, a frictional resistance of bearings, a smoothness of bearing’s rolling and a bearing cage, a break of rolling bearing’s separator, a misalignment of a rotor assembly’s support, etc. In FAM-C and FDM-A methods two kinds of presentations are used: first a presentation as characteristic patterns (analogous to Fourier spectrum lines but providing to observe periodical and stochastical phenomena) as well as the presentation of the frequency versus time. From the point of view of authors in many cases they are similar to presentations known from a theory of a radio signals transmission. It is possible to find carrier wale and side spectrum lines, beats caused by summation of two signals with approximate frequencies as well as many others. If analogy is so univocal, it is possible to use many systems and dependences used in telecommunication. For example: coherence demodulation (synchronous), which authors intend to use for separation characteristic patterns of two different mechanical assemblies with approximate vibration frequencies. At the end there are presented authors’ considerations, related to superposition of signals and beats as well as reflection of these phenomena in observed power units.

Some Problems of a Diagnosis of Turbine Engine Bearings Using FAM-C Method

Diagnostic FDM-A method [2] based on a measurement of frequency modulation of a pulsation component as well as FAM-C method based on a measurement of a alternating current’s frequency have been developed in Air Force Institute of Technology. These methods provide to define a level of a sub-assembly’s abrasive wear and its localization during normal work of a power unit. It is possible to define numerous parameters of bearings and their kinematics pairs as well as a rotor assembly. They are: a level of a bearing rolling friction, smoothness of a bearing cage’s motion, a quantity of a radial clearance. It also provides to detect resonances in elements as well as observe a shape and a relative height of characteristic patterns, from which it is possible to calculate, among others, a quantity of a mechanical quality factor of a kinematics pair – it is possible to define an operating time reserve of the kinematics pair to resonance.

Photospheric Variability in EUVE Observations of β Canis Majoris (B1 II-III)

The only pulsating early-type star observed by EUVE, the β Cephei variable β CMa, displays periodic variability in its Lyman continuum which is basically consistent with the long-known optical and UV variability. The amplitude of the primary pulsation component is significantly larger in the EUV than in the optical or UV. This is consistent with a temperature change being the explanation for the variability. It is notable that the pulsations have been detected in the Lyman continuum because this part of the spectrum is formed in a much higher layer of the photosphere than either the UV or optical continua.