Suspension Modes Research Articles

Characterisation and Spatial Distribution of Sediments on the Cote d'Ivoire Continental Shelf (Abidjan to Assinie)

The continental shelf of Côte d'Ivoire, particularly the Abidjan-Assinie area, has been studied due to its importance and potential, although little research has focused on its sedimentological aspects. Sediment samples were collected using a Shipeck grab, and grain size analyses revealed the presence of fine sands, medium sands, and rarely very fine sands. These sands exhibit a skewness toward finer grains, which is abundant, followed by nearly symmetrical and highly skewed towards finer grains, describing five (05) types of sorting. Deposited in a more or less turbulent environment or due to excess load, the sands have been transported in water — as indicated by their shiny, abraded state — by saltation, suspension, and mixed modes. These sands preferentially reside in a continental domain.

Modal coupling characteristics of primary hunting in metro vehicles: Carbody suspension modes and hunting modes

Due to coupling with carbody suspension modes in railway vehicles, primary hunting can lead to significant low frequency swaying of the carbody, severely deteriorating ride quality. In order to address this issue, this paper conducts a detailed investigation into the coupling effect between suspension modes and hunting modes of metro vehicles. Initially, a simplified lateral dynamics model is established, and a continuous modal tracking method is adopted for track suspension modes and hunting modes. The results indicate that when the modal frequency of one hunting mode approaches that of corresponding suspension mode, the damping ratio of the two modes exhibits abnormal variation, and the modal frequency curve veers or is slightly disturbed. In exploring the coupling characteristics of hunting modes and suspension modes, revealing the variation trends and similarity of modal shapes, polar diagrams of modal shapes are presented, and the correlation distance is calculated. Equivalent conicity exerts a substantial influence on the effect of modal coupling, influencing minimum damping ratio and modal shape similarity within the modal coupling zone. To ensure sufficient stability margin for metro vehicles, it is necessary to avoid excessively low equivalent conicity. Finally, the phenomenon of vibration response deterioration within the modal coupling zone is confirmed through both a simplified model and a full DOF model.

FLUVIAL SEDIMENTOLOGY OF THE RIVER ETHIOPE SEDIMENTS, NIGER DELTA, SOUTHERN NIGERIA

Despite modern advances in the study of rivers globally, there remains a plethora of work to be done especially in the area of fluvial sedimentology of some present-day river systems. Previous studies on fluvial sedimentology of the sediments of the river Ethiope (in southern Nigeria) are meagre. Grain size analytical methods are indispensable to infer siliciclastic sediments' hydrodynamic conditions, transportation mode(s), and sedimentary environments. Twenty-eight samples (n=28) of the river Ethiope sediments were selected and studied using granulometric analyses (mechanical sieving and pebble morphometric methods). The granulometric analyses results revealed that the obtained sediments were comprised of 82.75% sand, 9.33% gravel, and 7.92% mud. A ternary diagram of sand-gravel-mud shows the sediments are mainly gravelly sand, with few indicating slightly gravelly sand, gravelly muddy sand, muddy sand, and sandy gravel. The grain size statistical analysis shows that the river Ethiope sediments consist of medium to coarse, poorly-sorted to moderately well-sorted, strongly coarse skewed to strongly fine skewed, and very platykurtic to extremely leptokurtic sands. The pebble morphometric analysis revealed that the pebbles range in shape from bladed (B) 22%, compact-bladed (CB) 17%, compact (C) 16%, compact-platy (CP) 16%, compact-elongated (CE) 12%, platy (P) 5%, to elongated (E) 5%. The integration of bivariate plots, ternary diagrams, and C-M patterns plotted for the sediments of the river Ethiope indicated a fluvial environment with sediments characterised by low to moderately high energy that transport sediments of different sizes and grades through saltation, traction, and suspension modes. This study also confirms that sediment transport modes such as saltation, traction, and suspension typify river environments. In general, the existing sedimentologic models derived from grain size analysis of sediments and pebble morphometric methods obtained from modern-day rivers can be applied to better understand transport modes, sedimentary processes, and palaeoenvironments of their ancient counterparts.

Growth Instability of 2D Materials on Non-Euclidean Surfaces.

Chemical growth of two-dimensional (2D) materials with controlled morphology is critical to bring their tantalizing properties to fruition. However, the growth must be on a substrate, which involves either intrinsic or intentionally introduced undulation, at a scale significantly larger than the materials thickness. Recent theory and experiments showed that 2D materials grown on a curved feature on substrates can incur a variety of topological defects and grain boundaries. Using a Monte Carlo method, we herein show that 2D materials growing on periodically undulated substrates with nonzero Gaussian curvature of practical relevance follow three distinct modes: defect-free conformal, defect-free suspension and defective conformal modes. The growth on the non-Euclidean surface can accumulate tensile stress that gradually lifts the materials from substrates and progressively turns the conformal mode into a suspension mode with increasing the undulation amplitude. Further enhancing the undulation can trigger Asaro-Tiller-Grinfield growth instability in the materials, manifested as discretely distributed topological defects due to strong stress concentration. We rationalize these results by model analyses and establish a "phase" diagram for guiding the control of growth morphology via substrate patterning. The undulation-induced suspension of 2D materials can help understand the formation of overlapping grain boundaries, spotted quite often in experiments, and guide how to avoid them.

H2O2 assisted steel slag nanocomposite for degradation of organic pollutant in an advanced oxidation process for suspension and Spin-Coated mode

Electrical Furnace Steel slag (EAF) was converted into steel slag nanocomposite (SSNC) by solvothermal preparation technique and assisted by H2O2 for Fenton and photo-Fenton-like degradation of six different dyes in both suspension and spin-coated modes. The physico-chemical properties were evaluated using various characterization tools. The result reveals that the EAF-SSNC exhibited nanocomposite behaviour. As a substrate for studying the advance oxidataion processes, methylene blue (MB) was first used. The kinetic study followed the pseudo-first-order reaction kinetics. The effect of operating factors was studied using the response surface methodology. Based on the optimum parameters, five reusability test was performed for both suspension and spin-coated mode, where 92.89% of MB was degraded in the fifth cycle for suspension mode and 88.21% for spin-coated mode. The photodegradation efficiency of methylene blue, methyl red, rhodamine-B, Congo red, acid blue-25, and methyl orange were 85.84%, 74.62%, 70.53%, 58.66%, 45.21%, and 40.38%, respectively, at a neutral pH. The effect of scavenger and total organic carbon (TOC) were analyzed. Moreover, the degradation pathway was identified using an LC-mass spectrometer. This work showed that slag nanocomposite is effective for dye degradation and lowering the overall cost of the Fenton process at a neutral pH.

Linear stability analysis of a high-speed rail vehicle concerning suspension parameters variation and active control

An Eigen root analysis is fulfilled for a high-speed rail vehicle concerning suspension parameters variation and active control using a simplified lateral-dynamics-intended model. The model is verified to be capable of reflecting the modal features of both carbody suspension modes and hunting modes. Subsequently, the effects of suspension parameters and the active yaw damper (AYD) on the vehicle modes are examined with various wheel/rail conicities. It shows that the frequency of hunting motion does not linearly increase with the vehicle speed but saturates to a value over 300 km/h. The crucial influential suspension parameters of the vehicle modes include the series stiffness and damping coefficient of the yaw damper, the longitude positioning stiffness on the wheelset, the series damping of the lateral damper, and the lateral stiffness of air springs. Sky-hook damping/stiffness control of AYD helps to increase the modal damping for bogie hunting concerns. For a large conicity of 0.37 case, a minimum of 400 kN·s/m is suggested for the damping control and 10 MN/m for stiffness control. Moreover, the damping control would adequately relieve the carbody hunting with a conicity of 0.11, and the stiffness control still works fine even with an extremely small conicity of 0.07.

Textural characteristics, mode of transportation and depositional environment of the Stormberg Group in the Eastern Cape, South Africa: evidence from grain size and lithofacies analyses

Abstract The Stormberg Group comprises the Molteno, Elliot and Clarens formations and is one of four stratigraphical groups that make up the Karoo Supergroup in South Africa. The group is the highest unit in the Karoo Basin, representing the final phase of preserved sedimentation. The major problem with the Stromberg Group is that the mode of transport, hydrodynamic energy conditions and depositional environment are still poorly understood. For the present paper, grain size and lithofacies studies on selected sandstones from the Molteno, Elliot and Clarens formations were performed so as to elucidate their textural characteristics, depositional processes, sedimentation mechanisms and hydrodynamic energy conditions and to discriminate different depositional environments. The statistical parameters of grain size distribution (mean grain size, standard deviation, skewness and kurtosis) show that the sandstones are predominantly unimodal, fine grained, moderately well sorted, mesokurtic and near symmetrical. The bivariate diagrams of the aforementioned statistical parameters demonstrate that river and aeolian dune had the greatest impact on the depositional environments. Likewise, the C-M pattern (Passega diagram) shows that the sandstones were mostly deposited through tractive current process. Furthermore, the C-M diagram reveals the prevalence of rolling, suspension and graded suspension modes of sediment transportation. Seventeen sedimentary lithofacies were identified and grouped into seven lithofacies associations. These lithofacies associations indicate braided channel, overbank and swamp deposits for the Molteno Formation, alluvial fan/floodplain and playa deposits for the Elliot Formation and aeolian deposits for the Clarens Formation.

Hybrid Active–Passive Actuation Approach of Passively Levitated Thrust Self-Bearing Machines

Passively levitated thrust self-bearing machines with combined armature windings have recently been introduced. These machines reach higher reliability and compactness while being lower cost than their actively suspended counterparts. However, they result in small axial restoring force and stiffness at low speeds since the axial guidance relies on passive phenomena arising from induced currents. The axial destabilizing stiffness produced by the permanent magnet centering bearings as well as the axial load, therefore, prevent the rotor from levitating below a threshold speed. This article introduces and develops a solution to this problem based on a hybrid active–passive actuation approach of these thrust self-bearing machines. The approach consists of regulating the rotor axial position through the direct-axis component of the currents flowing in half of the combined winding until reaching the threshold speed beyond which passive axial suspension can be achieved. Since the active operation solely requires the addition of an axial position sensor, the benefits related to passive levitation are only slightly affected. Extensive experimental investigations corroborate the force and torque model derived for the active operation and highlight that the transitions between suspension modes have a limited impact on the rotor axial position and spin speed, validating the proposed hybrid active–passive actuation approach.

Research on Energy Reclaiming Active Suspension Control Strategy Based on Linear Motor and Hydraulic Hybrid System

Based on linear motor and hydraulic hybrid energy reclaiming suspension, control strategy for multi-mode switched active suspension is designed. By establishing a quarter vehicle suspension system model, a fuzzy sliding mode controller is designed to control the active suspension system, and design active suspension mode switching strategy to select and switch suspension modes of vehicles under different conditions, it improves the performance of active suspension as well as the feed-ability of the suspension. The accuracy of the model and control strategy is verified by simulation, at the same time, a quarter suspension bench is built for test. The test results show the effectiveness of the simulation. The energy-feed test shows that the energy-feed efficiency of the designed energy reclaiming suspension can reach 17.54%.

Active damping of rotating platforms using integral force feedback

This paper investigates the use of Integral Force Feedback (IFF) for the active damping of rotating mechanical systems. Guaranteed stability, typical benefit of IFF, is lost as soon as the system is rotating due to gyroscopic effects. To overcome this issue, two modifications of the classical IFF control scheme are proposed. The first consists of slightly modifying the control law while the second consists of adding springs in parallel with the force sensors. Conditions for stability and optimal parameters are derived. The results reveal that, despite their different implementations, both modified IFF control scheme have almost identical damping authority on the suspension modes.

Textural characteristics, mode of transportation and depositional environment of the Cretaceous sandstone in the Bredasdorp Basin, off the south coast of South Africa: Evidence from grain size analysis

Abstract A total of 92 representative sandstone samples of the Bredasdorp Basin in boreholes E-AH1, E-AJ1, E-BA1, E-BB1 and E-D3 have been investigated for their grain size characteristics. Grain size textural parameters and their cross plots, linear discriminate functions (LDFs), C–M (C = first percentile and M = median) diagram and log–probability plots were calculated and interpreted to understand the mode of transportation and hydrodynamic conditions and also to unravel the depositional environments of the sediments. The grain size textural parameters revealed that the Bredasdorp sandstones are unimodal, predominantly fine-grained, moderately well-sorted, mesokurtic and near symmetrical. The bivariate plots of grain size textural parameters indicate that the depositional environments had been influenced mainly by river/beach/coastal dune conditions. The LDF plots show that the sediments are turbidity current deposits in a shallow marine environment. The C–M diagram revealed that the studied sandstones were mainly deposited by traction currents and beach process. In addition, the grain size log–probability curves and C–M diagram show the predominance of suspension and saltation modes of sediment transportation. Based on the inter-relationship of the various statistical parameters, it is deduced that the Bredasdorp Basin are mainly shallow marine deposits with signature of beach and coastal river processes.

Model showing influence of tectonics and energy condition of the fluvial environment on facies architecture: A case history of Quaternary alluvial deposits of Purna basin, central India

Present work includes identification of lithofacies and reconstruction of depositional environments including controls of tectonics, and energy condition of the medium on sedimentation pattern of alluvial deposits of Purna basin, central India. The basin exhibits good development of dominantly areno-argillaceous sediments along with restricted occurrences of boulder-pebbly lithounits, covering together an area of 6,522 km2. These sediments are also characterized by preservation of various calcrete morphotypes, vertebrate remains and Youngest Toba Tuff (YTT) ash in certain stratigraphic units. The work is based on detailed field and lithological studies of 20 river-cut sections exposed along the course of Purna river, representing entire alluvial deposits in both vertical and lateral profiles. Three lithofacies associations have been identified, i.e., (1) gravelly facies association (FA-1), (2) sandy facies association (FA-2) and, (3) silty-clayey facies association (FA-3). These associations consist of total 10 lithofacies distributed as: (i) matrix supported massive gravelly (Gmm) facies, (ii) matrix supported gravelly (Gmg) facies, (iii) horizontally stratified gravelly (Gh) facies, (iv) planar stratified gravelly (Gp) facies (FA-1), (v) horizontal sandy (Sh) facies, (vi) planar cross stratified sandy (Sp) facies, (vii) low angle cross bedded sandy (Sl) facies, (viii) massive sandy (Sm) facies (FA-2), (ix) laminated sandy (Fl) facies, and (x) palaeosol (P) facies (FA-3). Various architectural elements have also been identified. Based on lateral and vertical profiling of the lithofacies architecture, it is interpreted that gravel dominated facies in the mountainous region of the basin area are deposited by medium to high energy debris flow,whereas sandy and silty-clayey facies in the plain area are because of saltation and suspension modes of deposition under medium to low energy condition of depositing medium. The tectonic and topographical controls are well reflected on the sedimentation pattern and the same has been illustrated by proposing a model. Discussions along with the model have also been made on the progressive development of bazada or, pediment zone along the northern margin of the basin marked by the foothills of Satpura mountain ranges.

Dynamic response of a high-speed train under a type of gust with different durations

In order to study the effect of different gust durations on the safety of a high-speed train passing by a wind-break breach at a speed of 120 km/h, the root locus method is used to analyze the suspension modes of the train under different speeds. The original gust is obtained based on the Unsteady Reynolds-averaged Navier-Stokes (URANS) model when the train passes by a 12 m breach between two windbreaks with a normal crosswind speed of 32 m/s. A group of scaling factors for stretching and compressing the time windows is applied to change the gust duration without changing the amplitude. The results show that when the gust duration is close to the natural period of the suspension system, the train responses and derailment coefficient of the train can be amplified. As the attack angles of the first and second wheelset are still in the clockwise direction when overlooking the wheelset, the first wheelset is more vulnerable than the second wheelset. When the gust duration is longer than the natural period of lower sway, the initial fluctuation of the train response can be relieved.

Experimental Modal Analysis of an Aircraft Wing Prototype for SAE Aerodesign Competition

This work presents an experimental modal analysis of an aircraft wing prototype, designed by the Aerodesign team of the University of Brasilia, and performs a ground vibration testing of the prototype. The dynamic response data were acquired using the software LabVIEW, and the modal parameters were identified through the EasyMod toolbox. The modal parameters are characterised for the first seven vibration modes of the structure, with the firsts two being suspension modes of vibration. The effect of small changes in the experimental procedure on the identified modal parameters is discussed. It was observed that the use of an excitation signal as a logarithmic sine sweep and with a frequency range of excitation between 2 to 150 Hz resulted in less noise and more accurate measurement of the structure’s response. Results for different modal identification methods were verified using the Modal Assurance Criterion (MAC), and good correlation was achieved.

Vehicle suspension force and road profile prediction on undulating roads

Controllable suspension systems have the capability of changing suspension forces. One control approach is to define a cost function with the aim of optimising either ride comfort or handling. Such controllers are usually reactive and not pro-active. Controllers can benefit significantly by having a priori knowledge of the effect that changing the suspension settings will have on the suspension forces. This is especially true for vehicles traversing very rough terrain. This paper addresses the a priori knowledge needed by predicting what the suspension forces will be before changing the suspension setting. The proposed approach involves estimating sprung and unsprung mass acceleration, estimating the road excitation, and then predicting the suspension forces. A quarter car model is used to illustrate the concept. Thereafter, the concept is extended to a nonlinear multibody dynamics model and finally validated experimentally. Results indicate that the suspension force in a different suspension modes can be predicted before switching suspension modes.

Multi-Modes Control for Semi-Active Suspension Systems

The aim of this work is to design and analyze multi-modes semi-active suspension using a Continuously Variable Damper (CVD). A modeling approach for the CVD is presented, and three suspension modes are developed. The studied damper can achieve different suspension modes by controlling the actuation force, which makes its damping adjustment more efficient. By applying an appropriate control strategy to the damper based on minimizing the quadratic gap between the control actuation force for each mode and a control target, satisfaction of both ride comfort and driving safety can be realized. The control target is synthesized using CRONE-SkyHook approach. Performances of the proposed method are validated through a speed bump profile and a real measured road profile.

Grain size distribution and environmental implications of Rosetta beach, Mediterranean Sea coast, Egypt

Grain-size analysis of beach sediments along Rosetta beach of the Nile delta coast has been carried out to reveal the depositional environment condition, energy and hydrodynamic conditions, as well as the mode of transportation along the study area. In total 56 beach samples were collected, distributed along 3 profiles parallel to the shoreline and covering the shoreline, semi-wet area, and the dry backshore area. The study showed the great sensitivity of the interrelationships of various grain size statistical parameters (mean size, sorting, skewness, and kurtosis) to the slight variations in the compositional formula of the sediment mixture. Distribution of the textural parameters revealed the dominance of unimodal pure sand sediments, mainly Nile sand sources. The fluctuation between moderately well-sorted to well-sorted sediments and from coarse skewed to fine skewed under leptokurtic to platykurtic nature was distinguished at different localities and relevant environmental implications. Different discrimination tools as bivariate cross plot of grain size parameters, Linear Discrimination Functions (LDF), skewness and kurtosis relationship as a non-dimensional expression of sediment/energy simulation, Energy Process diagram, and mode of transportation (C-M diagram), indicates the marine signature followed the riverine input as a function of the sediments locality. Depositional processes were mainly hydraulically controlled through active energy processes of the marine environment. The fluvial nature of sediment demonstrated the graded suspension and saltation modes as the prime factors for transportation, influenced by marine and turbidity environment actions, within a shallow agitated marine environment.

Impact Behavior of Hydrophilic Micron Particles on a Planar Gas-Liquid Interface.

The behavior of hydrophilic micron particles impacting on the gas-liquid interface has been further experimentally studied using a high-speed camera at different surface tensions and dynamic viscosities of liquids. The results show that the impact behavior exhibits suspension and submergence modes, whose boundary cannot be clearly identified because the overlap between the impact velocity ranges occurs because of the unstable pinning of the three-phase contact line on the surface of hydrophilic particles. The liquid properties have little effect on the wettability of hydrophilic particles but greatly influence the hydrodynamic and capillary force exerted on the particles, leading to the expansion of the suspension mode range. In addition, the penetration probability changes little with the decrease in surface tension, while it significantly reduces with the increase in dynamic viscosity. A penetration probability model is predicted as an exponential function of the inertial and supporting forces, and the experimental values agree well with the predicted values. The outcomes of this research will be helpful for understanding the mechanism of particle-interface interaction and providing guidance for enhancing the separation of hydrophilic fine ash via a bubble scrubbing system.

PREDICTING THE DEPOSITIONAL ENVIRONMENTS AND TRANSPORTATION MECHANISMS OF SEDIMENTS USING GRANULOMETRIC PARAMETERS, BIVARIATE AND MULTIVARIATE ANALYSES

Grain size distribution and classes present in sedimentary rocks are responsive to the physical changes of the transporting media and the basin of deposition. Analyzing grain size data is germane in reconstructing the sedimentary processes including identifying the palaeoenvironment of deposition. Twenty-three (23) samples, mainly sandstones, collected within latitude 6 055’-6 059’N and Longitude 005 044’-005 053’E in the Anambra Basin, were subjected to granulometric analysis, where grain size parameters (mean grain size, sorting, skewness, and kurtosis) sensitive to environmental conditions were calculated. These parameters were integrated with bivariate and multivariate analyses. Graphics mean (Mz) in the study area range from 1.1 to 2.27 ɸ with an average value of 1.7 ɸ, suggesting that grains are predominantly fine to medium; sorting range from 0.71 to 1.36 ɸ with an average value of 1.02 ɸ, suggesting sediments are moderately sorted; skewness range from -0.57 to 0.51 ɸ with an average value of 1.28 ɸ suggesting coarsely skewed to fine skewed with a predominating near symmetrical skewness and kurtosis range from 0.57 to 1.51ɸ, with an average of 1.28 ɸ suggesting a very platykurtic to leptokurtic character. Bivariate scatter plots of the grains size parameters predicted the environment of deposition as a shallow marine. Multivariate analysis calculated from established functions suggested environments that range from the beach (backshore) to shallow marine (subtidal). The integration of the granulometric parameters, bivariate and multivariate plots predict an environment that is dominated by high energy indicating that the sediments of the study area were deposited in a shallow marine environment. In addition, the Visher and Passega’s C-M diagrams characterized the transport mechanism of the sediments as predominantly by saltation although traction and suspension modes also play some roles. Keywords: transportation mechanism, granulometric parameters, bivariate analysis, multivariate analysis http://doi.org/10.35180/gse-2019-0002

A concept of active mount for space applications

Sensitive payloads mounted on top of launchers are subjected to many sources of disturbances during the flight. The most severe dynamic loads arise from the ignition of the motors, gusts, pressure fluctuations in the booster and from the separation of the boosters. The transmission of these dynamic forces can be reduced by mounting payloads on passive isolators, which comes at the expense of harmful amplifications of the motion at low frequency due to suspension resonances. To bypass this shortcoming, this paper presents a novel concept of active mount for aerospace payloads, which is easy to install, and meets two objectives. The first one is a high damping authority on both suspension resonances and flexible resonances without compromising the isolation and large stability margins of the closed loop system due to the collocation of the actuator and the sensor. The second one is a broadband reduction of the dynamic force transmitted to the payload, which was achieved in terms of 16 dB. The concept is presented in the first part of the paper and studied numerically and experimentally on a single degree of freedom isolator. A commercial isolator has been chosen for the purpose of the demonstration. The second part of the paper is dedicated to experimental validations on multi-degree of freedom scaled test benches. It is shown that the force feedback allows damping of both suspension and flexible modes (first and second modes, respectively), and significantly reducing the force transmitted in some broad frequency ranges.