scholarly journals Анализ методов расчёта крутильных колебаний судовых валопроводов

2020 ◽  
Vol 44 (3) ◽  
pp. 71-79
Author(s):  
Keyword(s):  
Finite Element ◽  
Accurate Method ◽  
Natural Oscillation ◽  
Calculation Methods ◽  
Oscillating Systems ◽  
Experimental Values ◽  
Similar Accuracy ◽  
Oscillation Frequencies ◽  
Elastic Characteristics

Рассмотрены невыясненные вопросы крутильных колебаний судовых валопроводов с целью повышения точности расчета собственных частот крутильных колебаний путем определения наиболее точного метода приведения системы к дискретному виду. Исследуются две крутильноколеблющиеся системы: экспериментальная установка простой конструкции (двухопорный вал с массами, имеющий привод от электродвигателя) и более сложная – главный пропульсивный комплекс портового буксира РБТ проекта 378. Для этого решается ряд задач: расчет установок двумя методами (с помощью классических уравнений определения инерционных и упругих характеристик системы и программ, использующих методы конечных элементов); торсиографирование названных систем для определения значений экспериментальных значений частот собственных колебаний; сравнительный анализ полученных расчетным и экспериментальным путем значений частот собственных колебаний: на его основе определяются наиболее точные методы расчета. Установлено, что оба рассматриваемых расчетных метода дают результаты приблизительно одной точности. Отмечено, что исследованные модели относительно просты с точки зрения их анализа и определения характеристик. Картина может измениться в случае более сложных систем: тогда один из рассмотренных методов может показать явное преимущество. Ключевые слова: крутильные колебания, метод конечных элементов, судовая энергетическая установка. The outstanding issues of torsion vibrations of vessels' shaft lines in order to improve the accuracy of calculating the natural frequencies of torsion vibrations by determining the most accurate method of reducing the system to the discrete form. Two torsion-oscillating systems are studied: an experimental installation of a simple design (a two – support shaft with weights, driven by an electric motor) and a more complex one – the main propulsive unit of RBT project 378 port tug. With this purpose a number of problems have to be solved: calculation of installations with two methods (using classical equations for determining the inertial and elastic characteristics of the system and programs using finite element methods); torsiography of these systems to determine the values of experimental values of natural oscillation frequencies; comparative analysis of calculated and experimental values of natural oscillation frequencies and determination of the most accurate calculation methods on its basis. It has been found that both calculation methods being considered lead to results of approximately similar accuracy. It is noted that the studied models are relatively simple in terms of their analysis and characterization. The picture may change in the case of more complex systems: then one of the methods considered may show a clear advantage. Keywords: torsion vibrations, finite element method, ship power plant.

Vibration Control of Oscillating System Based on Governing Visco-Elastic Characteristics of Absorber by Means of External Electric Signal

2008 ◽  
Vol 144 ◽  
pp. 220-225 ◽  
Author(s):  
V.A. Bilyk ◽  
E.V. Korobko ◽  
G.N. Reizina ◽  
E.A. Bashtovaya ◽  
E.B. Kaberdina ◽  
...  
Keyword(s):  
Shear Stress ◽  
Oscillation Frequency ◽  
Electric Field Intensity ◽  
Natural Oscillation ◽  
Smart Devices ◽  
Electric Signal ◽  
Oscillating Systems ◽  
Damping Decrement ◽  
Natural Oscillation Frequency ◽  
Elastic Characteristics

Electro-rheological fluids (ERF) allow us to create «smart» devices. One of the basic directions of application of such materials is damping in oscillating systems. This work describes simulation model and offers the results of experimental research by rheological properties and damping characteristic of ERF. Control signal is defined by electric field intensity, which is changed within the bounds of 0…0.5 kV/mm. Amplitude of oscillation – up to 5 mm, oscillation frequency is modified within the bounds of 0.5…5 Hz. The logarithmic damping decrement and natural oscillation frequency of oscillating system, shear stress and viscosity of ERF are determined.

scholarly journals ANALYSIS OF CALCULATION METHODS FOR DETERMINATION OF SURGE PILE MATERIALS VOLUME

2019 ◽  
Vol 1 (1) ◽  
pp. 203-211
Author(s):  
Valerij Sal'nikov ◽  
Andrej Basargin ◽  
Andrej Astapov
Keyword(s):  
Accurate Method ◽  
Crushed Stone ◽  
Calculation Methods ◽  
Volume Determination ◽  
Volume Calculation ◽  
Parallel Section ◽  
Wet Condition

Nowadays we have to handle the tasks for volume determination of surge pile materials (sand, coal, crushed stone) on industrial objects and building grounds. The type of work is necessary for keeping record of supplied and consumed materials, and also for their piling. This article gives com-parative analysis of 3 calculation methods for land works (horizontal sections, cone, vertical parallel section) in AutoCADCivil 3D. The object of research was the sand, delivered and piled in the Novosibirsk river port. The sand is a rather difficult substance to be calculated as it gets settled down in wet condition and blown away in dry one. The results of the research showed that the most accurate method for sand volume calculation is vertical parallel section one in AutoCADCivil 3D.

Determination of the effective stiffness of a unidirectional layer by the finite element method and approximate formulas

2021 ◽  
Vol 87 (3) ◽  
pp. 40-50
Author(s):  
I. P. Olegin ◽  
T. V. Burnysheva ◽  
N. A. Laperdina
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Elastic Properties ◽  
Volume Content ◽  
Theory Of Elasticity ◽  
Effective Stiffness ◽  
The Finite Element Method ◽  
Approximate Formulas ◽  
Elastic Characteristics

Layered composites formed by unidirectional layers are widely used in aviation in the most loaded areas of the aircraft. Data on the elastic properties of the layers are required for the strength and stiffness calculation of structural elements made of such materials. There are two possible approaches to address the problem. The first approach is based on solving the problem of micromechanics using methods of the theory of elasticity. The second approach consists in developing a simplified model of a unidirectional layer. Analysis of the model can provide for fairly simple formulas for determination of the effective stiffness of a unidirectional layer. A comparative analysis of the results obtained in both approaches revealed the limits of applicability of approximate formulas derived for evaluating the effective characteristics of the different types of composites depending on the volume content of fibers. The effective elastic characteristics of unidirectional composites are determined by the finite element method in the framework of the linear theory of elasticity. The boundary value problem is solved for a characteristic representative element selected in accordance with the physical and geometric parameters of the medium of an ordered structure. A set of algorithm-programs has been developed under ANSYS environment which automates calculations of the elastic characteristics of materials depending on the volume content of fibers at different ratios of the elastic properties of fibers and binder, and on the parameters of the curvature of the fiber cross-sectional profile. The results obtained by the numerical method are compared with the data obtained experimentally and by approximate formulas.

scholarly journals Research Of Dynamic Characteristics Of A Three-axis Micromechanical Gyroscope-Accelerometer

2021 ◽  
Vol 2086 (1) ◽  
pp. 012206
Author(s):  
I E Lysenko ◽  
D Y Sevostyanov ◽  
N F Kidyaev ◽  
A V Kovalev
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Dynamic Characteristics ◽  
Element Model ◽  
Natural Oscillation ◽  
Geometric Parameters ◽  
Original Design ◽  
Micromechanical Gyroscope ◽  
Micromechanical Device ◽  
Oscillation Frequencies

Abstract In this paper, an original design of a micromechanical gyroscope-accelerometer is proposed. A parametrizable geometric and finite element model of a micromechanical device is presented. The dynamic characteristics of the structure are studied and the dependences of the natural oscillation frequencies on the geometric parameters of the gyroscope-accelerometer are obtained.

Development of HPLC Method for the Purity Test by Design of Experiments and Determination of Activation Energy of Hydrolytic Degradation Reactions of Sofosbuvir

2020 ◽  
Vol 16 (7) ◽  
pp. 976-987
Author(s):  
Jakub Petřík ◽  
Jakub Heřt ◽  
Pavel Řezanka ◽  
Filip Vymyslický ◽  
Michal Douša
Keyword(s):  
Activation Energy ◽  
Design Of Experiments ◽  
Mobile Phase ◽  
Hydrolytic Degradation ◽  
Isoconversional Method ◽  
Hplc Method ◽  
Organic Modifier ◽  
Calculation Methods ◽  
Degradation Reactions

Background: The present study was focused on the development of HPLC method for purity testing of sofosbuvir by the Design of Experiments and determination of the activation energy of hydrolytic degradation reactions of sofosbuvir using HPLC based on the kinetics of sofosbuvir degradation. Methods: Following four factors for the Design of Experiments were selected, stationary phase, an organic modifier of the mobile phase, column temperature and pH of the mobile phase. These factors were examined in two or three level experimental design using Modde 11.0 (Umetrics) software. The chromatographic parameters like resolution, USP tailing and discrimination factor were calculated and analysed by partial least squares. The chromatography was performed based on Design of Experiments results with the mobile phase containing ammonium phosphate buffer pH 2.5 and methanol as an organic modifier. Separation was achieved using gradient elution on XBridge BEH C8 at 50 °C and a flow rate of 0.8 mL/min. UV detection was performed at 220 nm. The activation energy of hydrolytic degradation reactions of sofosbuvir was evaluated using two different calculation methods. The first method is based on the slope of dependence of natural logarithm of the rate constant on inverted thermodynamic temperature and the second approach is the isoconversional method. Results and Conclusion: Calculated activation energies were 77.9 ± 1.1 kJ/mol for the first method and 79.5 ± 3.2 kJ/mol for the isoconversional method. The results can be considered to be identical, therefore both calculation methods are suitable for the determination of the activation energy of degradation reactions.

Development of an HPLC-UV Method for Quantification of Stattic

2019 ◽  
Vol 15 (6) ◽  
pp. 568-573
Author(s):  
Soheil Sedaghat ◽  
Ommoleila Molavi ◽  
Akram Faridi ◽  
Ali Shayanfar ◽  
Mohammad Reza Rashidi
Keyword(s):  
High Performance ◽  
Accurate Method ◽  
Plasma Samples ◽  
Promising Target ◽  
Relative Standard ◽  
Dimerization Inhibitor ◽  
Oncogenic Protein ◽  
First Time ◽  
Transcription 3

Background: Signal transducer and activator of transcription 3 (STAT3), an oncogenic protein found constitutively active in many types of human malignancies, is considered to be a promising target for cancer therapy. Objective: In this study for the first time, a simple and accurate method has been developed for the determination of a STAT3 dimerization inhibitor called stattic in aqueous and plasma samples. Methods: A reverse-phase high-performance liquid chromatography (RP-HPLC) composed of C18 column as stationary phase, and the mixture of acetonitrile (60%) and water (40%) as mobile phase with a UV detection at 215 nm were applied for quantification of stattic. The developed method was validated by Food and Drug Administration (FDA) guideline. Results: The method provided a linear range between 1-40 and 2.5-40 µg mL-1 for aqueous and plasma samples, respectively, with a correlation coefficient of 0.999. The accuracy (as recovery) of the developed method was found to be between 95-105% for aqueous medium and 85-115% for plasma samples. The precision (as relative standard deviation) for aqueous and plasma samples was less than 6% and 15%, respectively. The sensitivity of the developed method based on FDA guideline was 1 µg mL-1 for aqueous and 2.5 µg mL-1 for plasma samples. Conclusion: These results show that the established method is a fast and accurate quantification for stattic in aqueous and plasma samples.

Is it necessary to calculate Young’s modulus in AFM nanoindentation experiments regarding biological samples?

2020 ◽  
Vol 12 ◽  
Author(s):  
S.V. Kontomaris ◽  
A. Malamou ◽  
A. Stylianou
Keyword(s):  
Young’S Modulus ◽  
Biological Samples ◽  
Young's Modulus ◽  
Reference Sample ◽  
Nonlinear Behavior ◽  
Accurate Method ◽  
Accurate Solution ◽  
Hertz Model ◽  
Work Done

Background: The determination of the mechanical properties of biological samples using Atomic Force Microscopy (AFM) at the nanoscale is usually performed using basic models arising from the contact mechanics theory. In particular, the Hertz model is the most frequently used theoretical tool for data processing. However, the Hertz model requires several assumptions such as homogeneous and isotropic samples and indenters with perfectly spherical or conical shapes. As it is widely known, none of these requirements are 100 % fulfilled for the case of indentation experiments at the nanoscale. As a result, significant errors arise in the Young’s modulus calculation. At the same time, an analytical model that could account complexities of soft biomaterials, such as nonlinear behavior, anisotropy, and heterogeneity, may be far-reaching. In addition, this hypothetical model would be ‘too difficult’ to be applied in real clinical activities since it would require very heavy workload and highly specialized personnel. Objective: In this paper a simple solution is provided to the aforementioned dead-end. A new approach is introduced in order to provide a simple and accurate method for the mechanical characterization at the nanoscale. Method: The ratio of the work done by the indenter on the sample of interest to the work done by the indenter on a reference sample is introduced as a new physical quantity that does not require homogeneous, isotropic samples or perfect indenters. Results: The proposed approach, not only provides an accurate solution from a physical perspective but also a simpler solution which does not require activities such as the determination of the cantilever’s spring constant and the dimensions of the AFM tip. Conclusion: The proposed, by this opinion paper, solution aims to provide a significant opportunity to overcome the existing limitations provided by Hertzian mechanics and apply AFM techniques in real clinical activities.

Determination of Charge Coefficient of Piezoelectric Films Using a Combined Finite Element Model and Dynamic Loading Technique

2020 ◽  
Vol 835 ◽  
pp. 229-242
Author(s):  
Oboso P. Bernard ◽  
Nagih M. Shaalan ◽  
Mohab Hossam ◽  
Mohsen A. Hassan
Keyword(s):  
Finite Element ◽  
Dynamic Loading ◽  
Material Properties ◽  
Accurate Determination ◽  
Substrate Material ◽  
Experimental Results ◽  
Piezoelectric Composite ◽  
Piezoelectric Film ◽  
Piezoelectric Charge

Accurate determination of piezoelectric properties such as piezoelectric charge coefficients (d33) is an essential step in the design process of sensors and actuators using piezoelectric effect. In this study, a cost-effective and accurate method based on dynamic loading technique was proposed to determine the piezoelectric charge coefficient d33. Finite element analysis (FEA) model was developed in order to estimate d33 and validate the obtained values with experimental results. The experiment was conducted on a piezoelectric disc with a known d33 value. The effect of measuring boundary conditions, substrate material properties and specimen geometry on measured d33 value were conducted. The experimental results reveal that the determined d33 coefficient by this technique is accurate as it falls within the manufactures tolerance specifications of PZT-5A piezoelectric film d33. Further, obtained simulation results on fibre reinforced and particle reinforced piezoelectric composite were found to be similar to those that have been obtained using more advanced techniques. FE-results showed that the measured d33 coefficients depend on measuring boundary condition, piezoelectric film thickness, and substrate material properties. This method was proved to be suitable for determination of d33 coefficient effectively for piezoelectric samples of any arbitrary geometry without compromising on the accuracy of measured d33.

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