Secondary Spring Research Articles

The Vibration Characteristics Analysis of Fiber-Reinforced Thin-Walled Conical–Cylindrical Composite Shells with Artificial Spring Technique

In this paper, the vibration characteristics (free vibration and forced vibration) of fiber-reinforced thin-walled conical–cylindrical composite shells (FTCCS) are analyzed by combining theory and experiment. Based on the classical shell theory and Kirchhoff–Love assumption, the overall structure of the FTCCS is theoretically modeled. The artificial spring technology is used to simulate the arbitrary boundary conditions at the joint, which is divided into a main spring and a secondary spring. At the same time, the displacement functions of the two sub-structure shells of the FTCCS are established by the orthogonal polynomial method, and the energy function of the FTCCS is constructed according to the continuity condition of the bolt joint. Then, the vibration characteristics of the FTCCS are solved using the Rayleigh–Ritz method and the modal superposition method. Finally, the TC300/epoxy resin-based fiber-reinforced thin-walled conical–cylindrical composite shells are selected as the research object, and the rationality of the mathematical model is verified by pulse, frequency sweeping and resonance excitation tests. The experimental results show that the errors between the natural frequency and the resonance displacement calculated by the theory and the experimental results are 1.75–4.76% and 3.79–9.28%, which confirms the rationality of the proposed model. By changing the length of the shell, the lamination angle and the semi-cone angle of the conical shell, the vibration characteristics parameters under different conditions are calculated to evaluate the influence of three physical parameters on the vibration characteristics of the FTCCS.

Theoretical and experimental investigations of vibration and damping behaviors of carbon fiber-reinforced composite thin shells with partial bolt looseness constraints

In this paper, the vibration and damping behaviors of fiber-reinforced composite thin shells under partial bolt looseness boundary conditions are investigated both theoretically and experimentally. Based on Love's shell theory, the complex modulus approach, and Hooke's law, a theoretical model of fiber-reinforced composite thin shells is constructed. A non-uniform artificial spring technique is proposed to accurately describe the non-uniform looseness in the bolt constraint positions and their interval locations, in which the two kinds of artificial springs, namely the “main spring” and “secondary spring”, are taken into account separately. After the natural characteristics, damping properties, and vibration responses are solved by the Rayleigh-Ritz method, strain energy approach, and Duhamel integral method, detailed measurements are undertaken on a CA 500 carbon/epoxy composite shell specimen to examine vibration and damping characteristics as well as to validate the proposed model. By comparing the theoretical results with the experimental ones, the maximum calculation errors of natural frequencies, resonant responses, and damping ratios are within an acceptable level. In addition, the influences of partial bolt looseness constraints on the vibration characteristics of such shell structures are also investigated here.

Performance evaluation of CFRP spring for freight car with lowering bed height in scale model

In recent years, there has been an increase in the volume of 40-ft marine high-cube containers handled in logistics in Japan. In Japan, the height of 40-ft marine high-cube containers limits the number of sections where they can be transported by rail. To solve this problem, it is necessary to develop a new freight car with a cargo bed height of 700 mm, which is 300 mm lower than a conventional freight car (bed height: 1000 mm) currently in use. For this purpose, a new carbon fiber reinforced plastic (CFRP) model secondary suspension spring with a lowered spring height has been developed to expand the possibilities of lowered bed height. Previous research has shown that the proposed CFRP spring is effective as a space- saving spring and it has nonlinear spring characteristics. Tests were conducted using different materials and shapes for the components of the spring. This paper shows the factors that change the nonlinear characteristics of the proposed CFRP spring.

低床化用台車に搭載した鉄道貨車の低床化を目的とした縮尺模型用CFRPばねの性能評価

In recent years, the handling volume of 40-ft ocean high-cube containers has increased in logistics in Japan. In Japan, the height of 40-ft ocean high-cube containers limits the number of sections where they can be transported by rail. To solve this problem, it is necessary to develop a new freight car with a cargo bed height of 700 mm, which is 300 mm lower than a conventional freight car (cargo bed height: 1000 mm) currently in use. For this purpose, a new carbon fiber reinforced plastic (CFRP) model secondary suspension spring with a lowered spring height has been developed to expand the possibilities of lowered bed height.

Nondimensional translational characteristics of elastomer components

Elastomer components are used in both primary and secondary spring stages in bogies of rail vehicles. The design of spring components of a bogie requires knowledge of the calculation of the elastic properties of these components. An elastomer spring component is typically analyzed in the dimension to be investigated. Calculated force-displacement curves are directly related to the material and dimension of the component itself. The objective of this paper is to establish generalized or, in other words, universally valid force-displacement characteristics by breaking the entanglement with component size. The advantage of this approach is the extended validity of the results for a specific spring shape of any size. The simulations are performed only once for each shape and may be converted to any other size using the proposed methodology. A numerical study of a layer spring with rectangular cross-sectional area and fixed edges on both top and bottom sides serves as a reference example.

Modelling and Sensitivity Analysis of Influencing Parameters in Displacement of Dynamic Bodies

The mathematical modelling in relation to the Six-degree freedom system of train suspension is developed and simulated for their dynamic characteristics. The important challenge in the suspension system is vertical displacement obtained from the vehicle body. To reduce vertical displacement, an analysis of the model is done by variation of parameters such as stiffness of spring and damping coefficient. The model has been created by deriving the equations of a system using Newton’s law. The developed model has the potential to analyse the dynamic characteristics of the suspension system for both displacement of the vehicle body and displacement of the wheel. The outcome of this research revealed that Secondary spring stiffness is the most dominant factor to influence the displacement of the vehicle body; Primary damping coefficient is the most dominant factor to influence displacement of the wheel.

Nonlinear Visco-Poroelasticity of Gels With Different Rheological Parts

Abstract A polymeric gel contains a crosslinked polymer network and solvent. Gels can swell or shrink in response to external stimuli. Two typical kinetic processes are involved during the deformation of gels: the viscoelastic and poroelastic responses. Viscoelasticity of gels is generated from local rearrangement of the polymers, while poroelasticity is generated from solvent migration. The coupled time-dependent behaviors of gels can be formulated by coupling a spring-dashpot model with a diffusion–deformation model. Different combinations of spring and dashpot and different ways of dealing with the coupling between solvent migration and rheological models—either through the spring or dashpot—induce significantly different constitutive behaviors and characteristic time-dependent responses of gels. In this work, we quantitatively study how different rheological models coupled with solvent migration affect the transient behavior of gels. We formulate the visco-poroelastic gel theory for the Maxwell model, the Kelvin–Voigt model, and the generalized standard viscoelastic model. In addition, for generalized standard viscoelastic model, we also discuss the different coupling through the secondary spring or the dashpot. The models are implemented into finite element codes, and the transient-state simulations are performed to investigate the time-dependent deformation and frequency-dependent energy dissipation of different rheologically implemented gel models. The result shows that different combinations of spring and dashpot give the gel solid-like properties and liquid-like properties under different time scales; in addition, the coupling of solvent migration with the dashpot in the rheological model results in restrictions of solvent migration under certain length scales.

Functional Factors of Biomass Burning Contribution to Spring Aerosol Composition in a Megacity: Combined FTIR-PCA Analyses

Whether the spring season brings additional pollution to the urban environment remains questionable for a megacity. Aerosol sampling and characterization was performed in the urban background of the Moscow megacity in spring 2017, in a period of a significant impact of mass advection from surrounding fire regions. Parametrization of Angstrom absorption exponent (AAE) on low and high values provides periods dominated by fossil fuel (FF) combustion and affected by biomass burning (BB), respectively. The period identification is supported by air mass transportation from the south of Russia through the regions where a number of fires were observed. Functionalities in entire aerosol composition, assigned to classes of organic, ionic compounds, and dust, are inferred by diffusion refection infrared Fourier transmission (FTIR) spectroscopy. Functional markers of urban transport emissions relate to modern engine technology and driving cycles. Regional BB functionalities indicate the fire impacts to the spring aerosol composition. The development of the advanced source apportionment for a megacity is performed by means of combined ambient FTIR data and statistical PCA analysis. PCA of FTIR spectral data differentiate daily aerosol chemistry by low and high AAE values, related to FF- and BB-affected spectral features. PC loadings of 58%, 21%, and 11% of variability reveal the functional factors of transport, biomass burning, biogenic, dust, and secondary aerosol spring source impacts.

Climate Driven Changes in Timing, Composition and Magnitude of the Baltic Sea Phytoplankton Spring Bloom

Spring phytoplankton blooms contribute a substantial part to annual production, support pelagic and benthic secondary production and influence biogeochemical cycles in many temperate aquatic systems. Understanding environmental effects on spring bloom dynamics is important for predicting future climate responses and for managing aquatic systems. We analyzed long-term phytoplankton data from one coastal and one offshore station in the Baltic Sea to uncover trends in timing, composition and size of the spring bloom and its correlations to environmental variables. There was a general trend of earlier phytoplankton blooms by 1–2 weeks over the last 20 years, associated with more sunshine and less windy conditions. High water temperatures were associated with earlier blooms of diatoms and dinoflagellates that dominate the spring bloom, and decreased diatom bloom magnitude. Overall bloom timing, however, was buffered by a temperature and ice related shift in composition from early blooming diatoms to later blooming dinoflagellates and the autotrophic ciliateMesodinium rubrum.Such counteracting responses to climate change highlight the importance of both general and taxon-specific investigations. We hypothesize that the predicted earlier blooms of diatoms and dinoflagellates as a response to the expected temperature increase in the Baltic Sea might also be counteracted by more clouds and stronger winds. A shift from early blooming and fast sedimenting diatoms to later blooming groups of dinoflagellates andM. rubrumat higher temperatures during the spring period is expected to increase energy transfers to pelagic secondary production and decrease spring bloom inputs to the benthic system, resulting in lower benthic production and reduced oxygen consumption.

Assessing seasonal dynamics of Guillain-Barré syndrome with search engine query data.

In previous studies, data deriving from Google Trends showed promising correlation with disease incidence trends assessed with public health control systems. The aim of this work is to use search engine query data to investigate seasonal dynamics in Guillain-Barré syndrome (GBS) in the USA. Average Google monthly search volumes for GBS from 2008 to 2017 were analysed for the USA overall and on regional base with generalized estimating equation models. Association with monthly historical temperature variations was tested. Monthly search volume for GBS displayed the greatest positive anomaly for October, clustering with September and November. Region-wide analysis confirmed this pattern and showed secondary spring (Feb/Apr) subpeaks in Pacific and Midwest. Association of GBS search volume with month-to-month temperature variations showed J-shaped relationship, with the highest peak occurring in months with greatest temperature falls, and subpeak in months with sharpest temperature rises. This study represents the first approach in investigating digital epidemiology of GBS and establishing possible links with traditional epidemiology. Cold season GBS peak has been observed by some traditional studies; hypothetical pathogenic relationship with infectious antecedents is supported from finding GBS peaks clustering with greatest temperature change. Further studies are needed to compare these findings to traditional public health approaches.

“QUEM NOS SALVARÁ DA MÍDIA?”: A REPRESENTAÇÃO DA PRIMAVERA SECUNDARISTA EM ARTIGO DA REVISTA ÉPOCA

Este artigo tem como objeto a representação construída pelo discurso da mídia sobre o movimento que ficou conhecido como Primavera Secundarista ocorrido no Brasil em 2016. Sendo um movimento de resistência dos estudantes de Ensino Médio contra as propostas de reforma e ajustes fiscais do governo brasileiro no âmbito da educação, a Primavera Secundarista envolveu jovens de várias partes do Brasil que ocuparam mais de 1000 escolas em todo o território nacional. Nosso objetivo, com este estudo, é analisar e compreender as estratégias usadas pela mídia para representar esse movimento. Utilizamos como corpus para a análise um artigo de opinião publicado na página on line da revista Época, assinado pelo colunista Fernando Schüler intitulado “E quem nos salvará de Ana Júlia?”. À luz do construto teórico-metodológico da Análise de Discurso Crítica (ADC), embasamo-nos, principalmente, nos escritos de Fairclough (2004) e Ramalho e Resende (2011), desenvolvendo assim, um estudo de caráter qualitativo, com foco no significado representacional. Compreendendo a linguagem como o lugar privilegiado de lutas e tensões sociais, discutimos as estratégias linguísticas e ideológicas utilizadas na produção do artigo e percebemos como resultado a construção, por parte da mídia, de uma imagem desqualificada do movimento Primavera Secundarista.

Modeling dynamic behavior of MDOF systems with multiple bilinear springs

A computational scheme is presented in this paper to simulate dynamical behavior of multiple degrees of freedom (MDOF) systems with multiple bilinear springs. In the proposed scheme, a bilinear spring is modeled using by two parallel springs - a primary spring and a secondary spring. The primary spring is an ordinary linear spring having identical stiffness in tension and compression, and is active for tension and compression. The secondary spring, whose stiffness characterizes the bilinearity, is active only during compression. It is employed in connection with the Newmark integration method and the linear complementarity problem (LCP) formulation to obtain time-domain responses of dynamical systems with bilinear springs due to initial disturbances and harmonic excitations. The scheme described in this paper is effective in dealing with the sudden transition from tension to compression and vice versa simultaneously for all bilinear springs. Numerical results for bilinear oscillators with finite bilinearity ratios and impact oscillators with an infinite bilinearity ratio show that the proposed bilinear spring model is accurate, generic and valid for bilinearity ratios ranging from zero to infinity. Orderly and chaotic behavior of viscously damped 3-DOF system under harmonic excitation is studied for a wide range of excitation frequencies and bilinear ratios to demonstrate the effectiveness and applicability of the proposed model for MDOF bilinear systems.

Method for secondary spring load equalization of railway vehicles with two-stage spring suspension: Modeling and optimal regulation

To ensure running safety, the secondary spring loads of railway vehicles must be well equalized. Due to the coupling interactive effects of these hyper static suspended structures, the equalization adjustment through shimming procedure is quite complex. Therefore, an effective and reliable method in application is developed in this paper. Firstly, the best regulation of spring load is solved based on a mechanical model of the secondary suspension system, providing a target for actual adjustment. To reveal the relationship between secondary spring load distribution and shim quantity sequence, a forecasting model is constructed and then modified experimentally with consideration of car body’s elastic deformation. Further, a gradient-based algorithm with a momentum operation is proposed for the load optimization. Effectiveness of the whole method has been verified on a test rig. It is experimentally confirmed that this research provides an important basis for achieving an optimal regulation of spring load distribution for multiple types of railway vehicles.

Proposal of stiffness of triple spring of a passenger railway vehicle

The article deals with the calculation of stiffness of a secondary suspension spring built in a bogie of a rail vehicle with a tilting car body. The vertical stiffness of the springs was calculated using the ANSYS program. The results were compared with calculated values afterwards. The lateral stiffness was evaluated in a similar manner. Analyt-ical method by Gross, Wahl, Budrick, Timoshenko and Ponomarieva was used for comparison with numerical values. The ANSYS simulation was performed for calculating the vertical stiffness of the triple springs. The most suitable analytical method is a method by Timoshenko and Ponomarieva, where the percentage difference was the smallest. The obtained data will be used as an input for the design of coil springs which will be implemented in a model of a vehicle with a tilting car body, for which the comfort values during transition in curve will eventually be determined.

Rotations of Pendulum When Its Pivot Oscillates Chaotically

This paper investigates the possibility of energy generation via pendulum rotations when the source of vertical excitation is chaotic in nature. The investigations are conducted using an additional height-adjustable mechanism housing a secondary spring to optimize a configuration of experimental pendulum setup. Chaotic oscillations of the pendulum pivot are made possible at certain excitation conditions due to a piecewise-linear stiffness characteristic introduced by the modification. A velocity control method is applied to maintain the rotational motion of the pendulum as it interacts with the vertical oscillator. The control input is affected by a motor, and a generator is used to quantify the energy extraction. The experimental results imply the feasibility of employing a pendulum device in a chaotic vibratory environment for energy harvesting purpose.

Processes controlling the seasonal variations in <sup>210</sup>Pb and <sup>7</sup>Be at the Mt. Cimone WMO-GAW global station, Italy: a model analysis

Abstract. We apply the Global Modeling Initiative (GMI) chemistry and transport model driven by NASA's MERRA assimilated meteorological data to simulate the seasonal variations in two radionuclide aerosol tracers (terrigenous 210Pb and cosmogenic 7Be) at the WMO-GAW station of Mt. Cimone (44°12′ N, 10°42′ E; 2165 m a.s.l.; Italy), which is representative of free-tropospheric conditions most of the year, during 2005 with an aim to understand the roles of transport and precipitation scavenging processes in controlling their seasonality. The total precipitation field in the MERRA data set is evaluated with the Global Precipitation Climatology Project (GPCP) observations, and generally good agreement is found. The model reproduces reasonably the observed seasonal pattern of 210Pb concentrations, characterized by a wintertime minimum due to lower 222Rn emissions and weaker uplift from the boundary layer and summertime maxima resulting from strong convection over the continent. The observed seasonal behavior of 7Be concentrations shows a winter minimum, a summer maximum, and a secondary spring maximum. The model captures the observed 7Be pattern in winter–spring, which is linked to the larger stratospheric influence during spring. However, the model tends to underestimate the observed 7Be concentrations in summer, partially due to the sensitivity to spatial sampling in the model. Model sensitivity experiments indicate a dominant role of precipitation scavenging (vs. dry deposition and convection) in controlling the seasonality of 210Pb and 7Be concentrations at Mt. Cimone.

Enhancing the isolation performance by a nonlinear secondary spring in the Zener model

In order to obtain an isolator with low resonance amplitude as well as good isolation performance at high frequencies, this paper explores the usage of nonlinear stiffness elements to improve the transmissibility efficiency of a sufficient linear damped vibration isolator featured with the Zener model. More specifically, we intend to improve its original poor high-frequency isolation performance and meanwhile maintain or even reduce its already low resonance amplitude by adding a nonlinear secondary spring into the isolator. Its isolation performances are evaluated under two input scenarios namely force transmissibility under force input and displacement transmissibility under base excitations, respectively. Thereafter, both analytical and numerical study is performed to compare the high-frequency transmissibility as well as resonance condition of the nonlinear isolator with its corresponding linear one. Results show that the introduction of nonlinear secondary spring in the Zener model can achieve an ideal improvement, i.e., reducing the transmissibility at high frequencies and meanwhile suppressing the resonance amplitude. It is also shown that both force and displacement transmissibility of the nonlinear Zener model decreases at the rate of 40dB/decade at high frequencies, which has not been achieved by the isolators with rigidly connected linear or nonlinear damper. As nonlinear spring is easier to fabricate and can have wider range choices of nonlinear parameters than a nonlinear damper, this new model can promote practical applications of such nonlinear vibration isolators.

The global tropospheric ammonia distribution as seen in the 13-year AIRS measurement record

Abstract. Ammonia (NH3) plays an increasingly important role in the global biogeochemical cycle of reactive nitrogen as well as in aerosol formation and climate. We present extensive and nearly continuous global ammonia measurements made by the Atmospheric Infrared Sounder (AIRS) from the Aqua satellite to identify and quantify major persistent and episodic sources as well as to characterize seasonality. We examine the 13-year period from September 2002 through August 2015 with a retrieval algorithm using an optimal estimation technique with a set of three, spatially and temporally uniform a priori profiles. Vertical profiles show good agreement (∼ 5–15 %) between AIRS NH3 and the in situ profiles from the winter 2013 DISCOVER-AQ (DISCOVER-Air Quality) field campaign in central California, despite the likely biases due to spatial resolution differences between the two instruments. The AIRS instrument captures the strongest consistent NH3 concentrations due to emissions from the anthropogenic (agricultural) source regions, such as South Asia (India/Pakistan), China, the United States (US), parts of Europe, Southeast (SE) Asia (Thailand/Myanmar/Laos), the central portion of South America, as well as Western and Northern Africa. These correspond primarily to irrigated croplands, as well as regions with heavy precipitation, with extensive animal feeding operations and fertilizer applications where a summer maximum and a secondary spring maximum are reliably observable. In the Southern Hemisphere (SH) regular agricultural fires contribute to a spring maximum. Regions of strong episodic emissions include Russia and Alaska as well as parts of South America, Africa, and Indonesia. Biomass burning, especially wildfires, dominate these episodic NH3 high concentrations.

Determination of Stiffness of Triple Spring Built in a Bogie of a Rail Vehicle

The article deals with the calculation of stiffness of a secondary suspension spring built in a bogie of a rail vehicle with a tilting car body. The vertical stiffness of the springs was calculated using the ANSYS program. The results were compared with calculated values afterwards. The lateral stiffness was evaluated in a similar manner. Analytical method by Gross, Wahl, Budrick, Timoshenko and Ponomarev was used for comparison with numerical values. The ANSYS simulation was performed for calculating the vertical stiffness of the triple springs. The most suitable analytical method is a method by Timoshenko and Ponomarev, where the percentage difference was the smallest. The obtained data will be used as an input for the design of coil springs which will be implemented in a model of a vehicle with a tilting car body, for which the comfort values during transition in curve will eventually be determined.

Phytoplankton productivity and size composition in Lake Simcoe: The nearshore shunt and the importance of autumnal production

Abstract Primary production by phytoplankton helps fuel hypolimnetic oxygen depletion as well as food web productivity, and is thought to have been affected by dreissenid mussel colonization in Lake Simcoe. Measured by short-term 14 C uptake, areal and volumetric rates of photosynthetic carbon uptake (production) were lower in nearshore ( a (Chl a ) concentrations were also lower at nearshore sites, except in summer (June–Aug.). Production increased from May to an annual maximum in September (350 mg C m − 2 d − 1 nearshore and 650 mg C m − 2 d − 1 offshore) and remained high through November; its annual minimum ( − 2 d − 1 ) was in February. A secondary spring maximum occurred in April in the offshore (450 mg C m − 2 d − 1 ) but not the nearshore (30 mg C m − 2 d − 1 ). Chl a and production of net phytoplankton (> 20 μm) was greatest from August through November at offshore sites (median contribution > 35% of total) but was much less at nearshore sites (median contribution a were dominated by nanoplankton (2–20 μm), with median contributions > 40% in most seasons. The lower production at nearshore than offshore sites supports previous inferences that dreissenid mussels have caused differential loss of planktonic primary production, especially of net phytoplankton, in nearshore waters. The results from Lake Simcoe are consistent with evidence from other lakes that dreissenids can have major impacts on seasonal blooms of diatoms as the mussels continue to spread within and among North American lakes.