توجه: محتویات این صفحه به صورت خودکار پردازش شده و مقاله‌های نویسندگانی با تشابه اسمی، همگی در بخش یکسان نمایش داده می‌شوند.
۱SEISMIC WAVE INTERACTION WITH A CIRCULAR TUNNEL LINING OF NONUNIFORM THICKNESS EMBEDDED WITHIN A POROELASTIC FORMATION
اطلاعات انتشار: پانزدهمین کنفرانس سالانه مهندسی مکانیک، سال
تعداد صفحات: ۸
An exact analysis for two–dimensional dynamic interaction of monochromatic progressive plane compressional and shear seismic waves with a permeable circular tunnel lining of circumferentially varying wall thickness buried in a boundless porous elastic fluid–saturated formation is presented. The novel features of Biot dynamic theory of poroelasticity in conjunction with the translational addition theorems for cylindrical wave functions, along with the appropriate wave field expansions and the pertinent boundary conditions are employed to develop a closed–form solution in form of infinite series. The effects of liner eccentricity, interface permeability, formation material type, incident wave frequency, and angle of incidence on the hoop stress amplitude are evaluated and discussed for representative values of the parameters characterizing the system.<\div>

۲SOUND SCATTERING FROM A SUBMERGED MULTILAYERED CYLINDRICAL SHELL WITH FUNCTIONALLY GRADIENT MATERIAL PROPERTIES
اطلاعات انتشار: پانزدهمین کنفرانس سالانه مهندسی مکانیک، سال
تعداد صفحات: ۸
An exact treatment based on the inherent background coefficients that describe the background amplitudes in the scattered field is employed to investigate the scattering of timeharmonic plane acoustic waves by an arbitrarily thick hollow isotropic functionally graded cylinder submerged in and filled with non–viscous compressible fluids. The mechanical properties of the graded shell are assumed to vary smoothly and continuously with the change of volume concentrations of the constituting materials across the thickness of the shell according to a power law distribution. The original inhomogeneous shell is approximated by a laminate model, for which the solution is expected to gradually approach the exact one as the number of layers increases. The transfer matrix (T–matrix) solution technique, which involves a system global transfer matrix formed as the product of the individual transfer matrices by applying continuity of the displacement and stress components at the interfaces of neighboring layers, is employed to solve for the modal scattering coefficients. Limiting cases are considered and good agreements with the solutions available in the literature are obtained.<\div>

۳Common Failure Modes of Electro–pumps in Industries
اطلاعات انتشار: سومین کنفرانس تخصصی پایش وضعیت و عیب یابی، سال
تعداد صفحات: ۸
This paper investigates the common faults of electro–pumps using vibration. The pumps studied in
this research include various types of electro–pumps in some industries such as water and waste
water, petrochemical complexes, and power plants. Using vibration analysis of, the major faults of
these pumps are extracted and the effect of the support type is examined. As a result, three faults
of imbalance, bearings faults, and misalignment are recognized as the important causes of electropumps
failures.<\div>

۴Necessity of condition monitoring for estimating the residual lifetime of rolling element bearings
نویسنده(ها): ،
اطلاعات انتشار: سومین کنفرانس تخصصی پایش وضعیت و عیب یابی، سال
تعداد صفحات: ۱۰
Rolling element bearings are the most widely used components in rotating machinery.
Estimation of their remaining useful life in order to increase the reliability and
availability of them is a critical issue in the field of condition monitoring of these
machinery. The defect propagation in these components is inherently stochastic. This
factor causes that their remaining useful life prediction be a challenging problem. In this
paper a method to predict the defect area of rolling element bearings is proposed using
RLS adaptive algorithm and fatigue damage mechanics approach. First, two models are
developed to correlate the statistical features of vibration signals and the defect size on
inner and outer races. After construction of diagnostic models, healthy bearings are tested
under operating conditions and the generated vibration signals are collected from the time
of initial defects until the final failure of the bearing. Using RLS adaptive algorithm,
diagnostic models, and the extracted vibration signals, the parameters in the mechanistic
model are updated and the area of defect can be predicted. The results of experimental
tests show that this approach can determine the defect area on both inner and outer rings
of roller bearings and as a result, their remaining lifetime can be predicted reliably.<\div>

۵The use of Level Crossing Rate for estimation of bearing defect size
نویسنده(ها): ،
اطلاعات انتشار: سومین کنفرانس تخصصی پایش وضعیت و عیب یابی، سال
تعداد صفحات: ۱۱
In this paper a new approach to determine the defect size of rolling element bearings is
proposed. This approach is based on the statistical characteristics of the vibrations signals
generated by rolling element bearings. Although some statistical parameters such as RMS and
kurtosis have some capabilities to detect the bearing faults, these parameters for accurate
estimation of defect size are not adequate. For the first time in this study the number of level
crossings of a specific level is introduced as a suitable parameter for rolling bearing defect size
estimation. The acceleration signal of rolling bearings has been measured and crossing analysis
showed that the number of crossings is proportional to the defect size on inner and outer races.
The results of experimental tests proved that this parameter can determine the defect length of
rolling bearings with a good approximation.<\div>
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