Research on the Approximate Calculation Method of the Fundamental Frequency and Its Characteristics on a Tensioned String Bridge

As a new type of composite bridge, the dynamic structural characteristics of a tensioned string bridge need to be deeply studied. In this paper, based on the structural characteristics of a tensioned string bridge, the Rayleigh method is used to derive formulas for calculating the frequencies of vertical, antisymmetric and lateral bending vibrations. The characteristics of the vertical and lateral bending vibration frequencies are summarized. The fundamental frequencies of the antisymmetric vertical bending and lateral bending of the tensioned string bridge are the same as that of the single-span beam under the corresponding constraint conditions. The shape and physical characteristics of the main cable have no effect on the frequency. The vertical bending symmetrical vibration frequency of the tensioned string bridge is greater than the corresponding symmetrical vibration frequency of the simply supported beam. The shape and physical characteristics of the main cable have a greater impact on the vertical bending symmetrical vibration frequency than the lateral bending frequency, and the vertical bending symmetrical vibration frequency increases with an increasing rise-to-span ratio. The tension force of the main cable has no influence on the frequency of tensioned string bridges. The first-order frequency of the tensioned string bridge is generally the vertical bending symmetrical vibration frequency. By adopting a tensioned string bridge structure, the fundamental frequency of a structure can be greatly increased, thereby increasing the overall rigidity of the structure. Finally, an engineering example is applied with the finite element parameter analysis method to study the vibration frequency characteristics of the tensioned string bridge, which verifies the correctness of the formula derived in this paper. The finite element analysis results show that the errors between the derived formula in this paper and the finite element calculation results are less than 2%, indicating that the formula derived in this paper has high calculation accuracy and can meet the calculation accuracy requirements of engineering applications.

Structural and Infrared Spectroscopy of Polyvinylpyrrolidone/Multi-walled Carbon Nanotubes Nanocomposite

In this work, polyvinylpyrrolidone (PVP)/ Multi-walled carbon nanotubes (MWCNTs) nanocomposites were prepared with two concentrations of MWCNTs by casting method. Morphological, structural characteristics and electrical properties were investigated. The state of MWCNTs dispersion in a PVP matrix was indicated by Field Effect-Scanning Electron Microscopy (FESEM) which showed a uniform dispersion of MWCNTs within the PVP matrix. X-ray Diffraction (XRD) indicate strong bonding of carbonyl groups of PVP composite chains with MWCNTs. Fourier transfer infrared (FTIR) studies shows characteristics of various stretching and bending vibration bands, as well as shifts in some band locations and intensity changes in others. Hall effect was studied to test the type of charge carriers which was shown to be P-type. The electrical conductivity was shown increased for the pure PVP and pure MWCNT from (2.047×10-5) (Ω.cm)-1 and (3.683×101) (Ω.cm)-1 to (2.51×102 and 2.36×102) (Ω.cm)-1for both concentrations of nanocomposites, which indicate the conductivity was enhancement by using the carbon nanotubes.

Functional Group Evaluation of Hydrogenated Vegetable Oil Using FTIR Method

This study aimed to predict the functional group changes in the natural form to hydrogenated form of vegetable oils using FTIR spectroscopic method. The edible oil, which are palm oil, groundnut oil, sesame oil, and vanaspathi(hydrogenated vegetable oil) were observed with relative intensities of the peak and characteristic area percentage of peaks. It is found that trans fatty acids at the peak of 966.34cm-1 in the region of 980-960cm-1 strong C=C bending vibration due to the presence of alkene disubstituted (trans) observed in the hydrogenated form of vegetable oil. Because the nutritional composition of the vegetable oil is intensely reduced and long-term consumption will bringadversative health problems for humans. Keywords: FTIR, Palm oil, Groundnut oil, Sesame oil, Vanaspathi, Transfats

Generation and Evolution Conditions of Polygonal Wear of High-Speed Wheel

Wheel polygonal wear has long been a problem that confused the safety of railway operation which has important theoretical value and research significance. In this paper, the conditions of polygonal wear of high-speed wheel are analyzed based on the wear model and verified by the field measured data. Considering the wheel track interaction caused by rotation, a finite element model of wheelset rotor dynamics is established. The effects of rotor speed, mass eccentricity, wheelset, and track flexibility on the vibration characteristics of wheelset rotor system and wheel polygonal wear characteristics are analyzed by beam element and solid element, respectively. The results show that the wheel longitudinal vibration is the main reason of wheel polygonal wear, and the wheel polygonal wear follows the law of “constant frequency and divisible.” Its “constant frequency” comes from the wheel track contact vibration, which stimulates the third-order vertical bending vibration of wheelset and the eighth-order coupled bending vibration of track, and the order is equal to the ratio of “constant frequency” to the wheelset rotation frequency.

Analysis and Study on Bending Vibration Frequency of New Corrugated Steel Web Composite Box Girder

In order to accurately analyze the bending vibration frequency of the new composite box girder, the effects of web folding effect, shear lag, and shear deformation are comprehensively considered in this paper, and the elastic control differential equation and natural boundary conditions of the composite box girder are established by using the Hamilton principle. A one-span composite box girder with corrugated steel webs is used as a numerical example. The effects of height span ratio, width span ratio, web thickness, cantilever plate length, and fold effect on the vertical vibration frequency of the new composite box girder are analyzed. The results show that the analytical solution is in good agreement with the finite element solution. When considering the shear lag and fold effect, the vibration frequency of composite box girder decreases. With the increase in order, the influence of shear lag and fold effect on its frequency becomes stronger. The changes of height span ratio and web thickness of composite box girder have a great influence on its folding effect, while the changes of width span ratio and cantilever plate length have little influence on it. The conclusion can provide a reference for the design of medium section new composite bridge in practical engineering.

Application of Elastic Fastenings of Equipment to Increase Vibration Frequency of the Wagon Body

Improving dynamic performance is a priority when designing new rolling stock. The frequency of natural bending vibrations of the body is one of the most important standardised indicators, a preliminary assessment of which allows obtaining optimal body designs.The objective of the work is to assess the prospects for the use of elastic fastenings of equipment to increase the natural vibration frequency of wagon bodies of suburban electric trains. Calculations were based on the finite element method and block Lanczos method. It is shown that it is advisable to use the rigid area tool and linearly elastic finite elements to calculate the frequencies in the simulation. The main ranges of fastening stiffness are highlighted, where the effect of using elastic supports is different. It is proposed to determine the stiffness of fastenings according to a given vibration frequency of the equipment. When the equipment is rigidly attached, the relative mass of the equipment does not affect the body bending vibration frequency. With elastic fastening, a greater effect can be achieved with a larger relative weight of the equipment. The effect of using resilient mounts increases with heavier equipment located closer to the centre of the body.It is shown that the effect of shear admittance of fastenings on the body vibration frequency is within 1 % and may not be considered in the simulation. In the considered example of a wagon body of a suburban electric train, the use of elastic supports allows an increase in the frequency of oscillations of the body by 3–10 %.

Isolasi dan Identifikasi Saponin dari Ekstrak Leunca (Solanium ningrum L) Secara Spektrofotometri Infra Merah

Penelitian ini dilakukan untuk mengisolasi dan mengidentifikasi senyawa saponin dengan maserasi menggunakan etanol 95% sampai mendapat ekstrak kering sebanyak 20 gram dengan dipanaskan menggunakan evaporator. Ekstraksi kedua dilakukan menggunakan corong pisah dengan pelarut dietil eter dan n-butanol. Identifikasi saponin dilakukan dengan tiga parameter uji diantaranya uji busa, uji warna dan gugus fungsi menggunakan Spektrofotometer Infra Merah. Hasil pengukuran Spektrofotometri Infra Merah menunjukkan Ekstrak Daun Launca mengandung beberapa gugus fungsi sebagai berikut : gugus –OH (puncak yang lebar pada bilangan gelombang 3444,87 cm-1), regang –CH alifatik simetri (bilangan gelombang 2926,01 cm-1 dan2854,65 cm-1, regang C=C tidak terkonjugasi pada bilangan gelombang 1606,7 cm-1, adanya regang C-H (bilangan gelombang 1074,35 cm-1 dan 1045,42 cm-1), dan adanya vibrasi bengkokan simetris C-O pada bilangan gelombang 1386,82 cm-1.Kata kunci: Daun leunca; spektrofotometer infra merah; saponin Isolation and Identification of Saponin from Leunca (Solanium ningrum L) Extract by Infrared SpectrophotometryABSTRACTThis research was conducted to isolate and identify saponin compounds by maceration using 95% ethanol to obtain 20 grams of dry extract by heating using an evaporator. The second extraction was carried out using a separating funnel with diethyl ether and n-butanol as solvents. Saponin identification was carried out with three test parameters including foam test, color test and functional group using Infrared Spectrophotometer. Infrared Spectrophotometry measurement results show that the Launca Leaf Extract contains the following functional groups: -OH group (wide peak at wave number 3444.87 cm-1), aliphatic symmetrical -CH stretch (wave number 2926.01 cm-1 and 2854 ,65 cm-1, unconjugated C=C stretch at wave number 1606.7 cm-1, presence of CH stretch (wave number 1074.35 cm-1 and 1045.42 cm-1), and the presence of symmetrical bending vibration of CO at wave number 1386.82 cm-1.Keywords: Infrared spectrophotometer; leunca leaf; saponin

Structural Dynamics of Real and Modeled Solanum Stamens: Implications for Pollen Ejection by Buzzing Bees

An estimated 10% of flowering plant species conceal their pollen within tube-like anthers that dehisce through small apical pores (poricidal anthers). Bees extract pollen from poricidal anthers through a complex motor routine called floral buzzing, whereby the bee applies large vibratory forces to the flower stamen by rapidly contracting its flight muscles. The resulting deformation and pollen expulsion depend critically on the stamen's natural frequencies and vibration mode shapes, yet these properties remain unknown. We performed experimental modal analysis on Solanum elaeagnifolium stamens to quantify their natural frequencies and vibration modes. Based on morphometric and dynamic measurements, we developed a finite element model of the stamen to identify how variable material properties, geometry and bee weight could affect its dynamics. In general, stamen natural frequencies fell outside the reported floral buzzing range, and variations in stamen geometry and material properties were unlikely to bring natural frequencies within this range. However, inclusion of bee mass reduced natural frequencies to within the floral buzzing frequency range and gave rise to an axial-bending vibration mode. We hypothesize that floral buzzing bees exploit the large vibration amplification factor of this mode to increase anther deformation, which may facilitate pollen ejection.