Cylinder Assembly Research Articles

Metagratings for underwater acoustic wavefront manipulation

Metagratings are flat periodic assemblies of small scatterers, engineered to achieve effects such as steering, beamforming, or absorption. They have recently received attention in both electromagnetism and acoustic fields. In this work, we report the design, modeling, and experimental characterization of metagratings to steer underwater acoustic wavefronts towards anomalous directions (i.e. not classically allowed by Snell-Decartes relationships) with high efficiency (close to 100%). They are build from simple assemblies of small brass cylinders, hold by 3D-printed plastic supports, and can redirect ultrasonic wavefronts either in reflection mode (when placed in front of a reflective surface like e.g. the water / air interface) or in transmission mode. Furthermore, we demonstrate how metagratings build from an asymmetrical pattern of multiple basic elements can achieve near perfect asymmetrical transmission: a wavefront incident from side of the structure is fully transmitted, while a similar wavefront incoming from the other side is fully reflected, achieving an acoustic one-way mirror effect. This work combine theoretical analysis, finite element modeling, and experimentation in water tanks to explore and demonstrate the potential of such metagratings for various applications in underwater acoustics, like communication, noise mitigation, and stealth.

INCREASING THE DURABILITY OF HYDRAULIC CYLINDERS OF LIFTING AND TRANSPORTING MACHINES

Most lifting and transporting and loading and unloading machines have a hydraulic drive. One of the most common actuators that perform reciprocating and rotary movements are hydraulic cylinders, characterised by one-sided wear of the rod seals. Known rod assemblies are elastic sleeves mounted in the hydraulic cylinder housing, which covers the rod with a guaranteed gap. During the unit operation, a gap seal forms in the gap between the rod and the sleeve, which prevents the leakage of the working fluid from the high-pressure cavity and centres the rod in the sleeve. However, to ensure the reliable centring of the rod, the intensive flow of the working fluid through the gaps is required, which leads to significant leaks of the working fluid and a decline in the unit efficiency. The optimal gap does not ensure centring, leading to reduced unit durability due to uneven wear of the sleeve and rod. Therefore, the development of new designs of rod seals that ensure self-centring is an urgent task. The development trends of modern hydraulic drives of construction, track, and loading and unloading machines aim at increasing the pressure of the working fluid up to 32 MPa. It imposes specific requirements on the designs of seals of hydraulic cylinders – the core executive bodies. The analysis of the factors that reduce the durability of reciprocating pair seals shows that it is possible to divide them into several types: wear, aging, operational, and design factors. The article aims to develop and describe a fundamentally new design of a self-centring rod seal, which can increase the durability of hydraulic cylinders of lifting-transporting and loading-unloading machines without using additional devices. The analysis of trends in the development of constructions of rod units of hydro cylinders showed that fundamentally new types have emerged among the existing designs, which simultaneously perform two functions – rod guides and sealing. The most notable among them are combined active and passive rod seals. Passive combined seals of rod assemblies of hydro cylinders differ from traditional ones in that they allow rod movements in the radial direction and allow slight distortions of the rod, compensating for assembly and installation inaccuracies of the assembly. Active combined seals have the same advantages as passive combined seals but additionally compensate for the wear of the guide sleeve, which increases the durability of the entire rod assembly of the hydraulic cylinder. Keywords: hydraulic drive of lifting and transporting machines, hydraulic cylinder rod assembly, sealing, one-sided wear of the rod assembly, self-centring.

Simulating the sealing performance of the double rubber cylinder assembly in an intelligent pipeline isolation tool

Intelligent pipeline isolation tools (IPITs) are widely used for pipeline maintenance and repair. Therefore, authors mainly study the sealing performance of double rubber cylinder IPIT. This study first analyzed the material and geometric properties of the rubber cylinders in an IPIT to establish a numerical finite element model of cylinder mechanical behavior. The influence of the cylinder hardness, camber angle, and short-side length on the sealing performance was subsequently investigated by systematically altering the established model according to the control variable method. Next, the response surface methodology was employed to evaluate the change in model sealing performance according to the coupled action of multiple rubber cylinder parameters and identify their optimal values.

Michael Addition Inducing Self-Assembly to Construct Mechanochromic BP Film.

Liquid crystalline blue phase (BP) with 3D cubic nanostructure has attracted much interest in the fields of photonic crystals due to their unique optical properties and the ability to control the flow of light. However, there remains a challenge for simultaneously achieving self-assembly and mechanochromic response of soft 3D cubic nanostructures. Herein, a scalable strategy for the preparation of soft 3D cubic nanostructured films using oligomerization of the Michael addition reaction, which can induce the assembly of double-twisted cylinders for collective replication, remodeling, recombination, and growth, with a phase transition from BPII to BPI, and to chiral nematic phase, is presented. The prepared BP patterns can be obtained by Michael addition oligomerization reaction and composite mask photopolymerization, which present distinct mechanochromic sensitive due to patterns derived from different BP state, and the pattern can be reversibly erased and recurred by mechanical force and temperature. The average domain size of BPII prepared using this strategy can achieve 96µm, which is 2.5 times larger than that obtained using the conventional cooling approach. This work provides new insights into the self-assembly and selective chemochromism of functional materials and devices.

Micromechanical analysis of composite materials considering material variability and microvoids

One of the main challenges for fiber-reinforced polymers (FRP) is the difficulty to predict their mechanical behavior. At the microscale, the properties of the constituents, their spatial distribution and the defects arising from manufacturing affect the mechanical behavior. In this work, statistically representative volume elements (SRVEs) are proposed based on a micromechanical finite element model to determine the effect of content, distribution and size of microstructural defects and, material uncertainties on the elastic mesoscale properties of FRPs. To that end, different cylindrical void sizes are considered as well as irregular shaped voids between fiber tows (inter-fiber voids). Fibers and voids are randomly distributed in a SRVE. An uncertainty quantification and management analysis is employed to obtain statistical descriptors of the effective mesoscale mechanical properties of FRPs. The results obtained are compared with analytical models. It is demonstrated that, for carbon fiber/epoxy composites, SRVEs with lateral dimensions equivalent to 15 times the average fiber diameter and a length of 0.01 mm along the longitudinal direction remain statistically representative with or without the presence of voids. The results show that the presence of voids reduces the transverse and shear elastic properties of FRPs. The smaller the voids are, the bigger is the reduction. Regarding the presence of inter-fiber voids, the reduction is lower. This trend is well predicted by the Mori–Tanaka mean field theory. However, the relative difference between the numerical and the analytical predictions increases for high void volume fractions. Regarding the effective longitudinal Young’s modulus, the rule of mixtures, the Mori–Tanaka mean field theory and the concentric cylinder assembly model provide similar predictions for the mean value, but the uncertainty is overestimated by the analytical models because the properties of the fibers take a single value for each calculation with the analytical model, while they more realistically change from fiber to fiber in the numerical SRVEs.

Effect of Form Defect in Thin-Walled Cylinder Assembly

Effect of Form Defect in Thin-Walled Cylinder Assembly

Nonlinear Vibration Feature Recognition Method for Reciprocating Compressor Cylinder Based on VMD-Multifractal Spectrum

The failure probability of piston ring abrasion occupies the forefront in reciprocating compressor cylinder assembly. Due to the reciprocating friction between the piston ring and cylinder liner, the local vibration signal contains typical nonstationary characteristics with a seriously overlapped frequency band of impact signals, while the different featured signals are coupled with each other. Therefore, the identification of cylinder friction and abrasion fault modes has always been a hot and difficult problem in fault diagnosis of reciprocating compressors. In order to monitor the friction and abrasion between low linear speed nonmetallic piston ring and cylinder liner of reciprocating compressor in refinery and provide a theoretical basis for preventive maintenance, an analysis method based on VMD-multifractal spectrum was presented in this paper. First, the feasibility of the proposed method was proven based on the cylinder vibration experiment of a reciprocating compressor in the laboratory. Then, an in-service reciprocating compressor in a refinery was taken as the research object, from which the cylinder friction vibration signals were processed by using variational mode decomposition to obtain a band-limited intrinsic mode function (BLIMF). Multifractal detrended fluctuation analysis is employed in the final abrasion pattern identification. The results show that the proposed method based on VMD-multifractal spectrum analysis can effectively obtain the abrasion state of a piston ring, which can avoid blind overhaul or provide the basis for preventive maintenance and a practicable engineering route for the study of the piston ring abrasion degree.

Modular All-Metal Ultrawideband Cylindrical Array for Multifunction Operation

Legacy cylindrical phased array systems are constrained to narrowband operation due to antenna element limitations amid a growing need to support advanced multifunctional platform requirements. In this article, a notch-based all-metal ultrawideband (UWB) antenna element suitable for cylindrical arrays is introduced. The proposed element is designed to operate over 2.75–10 GHz while being highly amenable to a cylindrical architecture via modularized assembly of compact scalable column facets. The primary enabling technical innovations are: 1) a new shunt-loaded stepped-impedance (SI) gap design scheme to improve low-frequency performance without increasing profile and 2) the design of a tongue-and-groove azimuthal crosswall that precisely conforms to the wedge-shaped unit cell for simple yet robust cylinder assembly. For a proof-of-concept demonstration, a 120° sector array is built having a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$12^{\prime \prime }$ </tex-math></inline-formula> outer diameter and 21 columns—each comprising eight single-polarized elements (168 total feed points). Measurements are presented for active phase-mode impedance and embedded element patterns of a central element, demonstrating good agreement with full-wave simulations.

Dosimetric analysis of intracavitary brachytherapy applicators: a practical study.

PurposeIntracavitary brachytherapy is one of the important methods of gynecological cancer treatment. The effect of attenuation is not considered in the dose calculation method released by the American Association of Physicists in Medicine Task Group No. 43 Report. In this study, the effect of high-dose rate brachytherapy applicators on dose distribution was measured using Gafchromic films and well-type ionization chamber.Materials and MethodsA plan created by the treatment planning system was first executed using a well-type ionization chamber with a water equivalent elasto-gel in place for charge collection. Again, same plan was executed using central tandems of various angulations with different diameters of vaginal cylinders and charge collection was measured. For in vitro dose measurements this plan was also executed on tandem and vaginal cylinder assembly with Gafchromic films fixed on the surface of vaginal cylinder.ResultsThe results show that the central tandem when used with different vaginal cylinders resulted in increase in effective attenuation of the beam. The central tandem of 300 angulations when used with a 35-mm diameter vaginal cylinder results in maximum attenuation whereas the 0º tandem when used with 20-mm diameter vaginal cylinder results in least attenuation of the beam.ConclusionDue to the attenuation by various applicators used in brachytherapy for the treatment of gynecological cancers, it can be concluded that the difference between practical dose and the treatment planning system calculated dose should be considered for the correct estimation of the dose to the target and the organs-at-risk.

INTEGRITY ASSESSMENT OF AN AIRCRAFT CYLINDER ASSEMBLY WITH A CRACK

The repeatability of the air-cooled piston engine cylinder assembly failure due to a crack in the cylinder head, as well as its severity from the aspect of crew and passenger safety were the main motives for our research. In this paper an integrity assessment of a cylinder assembly with a crack was performed. By modeling cracks of different lengths in the cylinder head and considering the values of stress intensity factors and J-integral values at a given crack length on the one hand and determining the critical values of these fracture mechanics parameters on the other hand, the stability of the crack was examined. As part of the research, the dependence of the crack length on the stress intensity factor was established. The methodology proposed in this paper can be adapted to assess the integrity of other similar structural elements.

Design of Hydraulic Floor Crane

These hydraulic floor cranes provide an efficient, low-cost alternative to other material handling equipment. Strong, robust, sturdy and built to very standard, these cranes are maneuverable in loading, unloading and shifting of heavy loads. Crane structure consists of chassis, vertical column, horizontal arm, and the hydraulic pump with cylinder assembly. The box crane can take heavy loads effectively, avoids damage under rough and unskilled handling. The hydraulic crane was invented in Newcastle by William Armstrong in about 1845 to help load coal into barges at the Quayside. In this paper the design and analysis of a hydraulic floor crane having arm motion in the vertical.

Seismic response of cylinder assemblies in axial flow

Earthquakes are a great challenge for the safety of nuclear reactors. To address this challenge, we need to better understand how the reactor core responds to seismic forcing. The reactor core is made of fuel assemblies, which are themselves composed of flexible fuel rods immersed in a strong axial flow. This gives rise to strongly coupled fluid–structure interactions whose accurate modelling generally requires high computational costs. In this paper, we introduce a new model able to capture the mechanical response of the reactor core subjected to seismic forcing with low computational costs. This model is based on potential flow theory for the fluid part, and Euler–Bernoulli beam theory for the structural part, allowing us to predict the response to seismic forcing in presence of axial flow. The linear equations are solved in the Fourier space to decrease computational time. For validation purposes, first we use the proposed model to compute the response of a single cylinder in axial flow. We then implement a multiple-cylinder geometry made of four fuel assemblies, each made of $8\times 8$ cylinders, corresponding to an experimental facility available at CEA. The comparison between numerical results and experiments shows good agreement. The model can predict correctly the added mass. It can also capture qualitatively the coupling between assemblies and the effect of confinement. This shows that a potential flow approach can give insight into the complex fluid–structure interactions within a nuclear reactor and, in particular, be used to predict the response to seismic forcing at low computational cost.

Mechanical anti-lock braking system using pneumatic system and solenoid valve with low cost manufacturing

PurposeThe Purpose of this study is to prove the possibility of developing low cost mechanical anti – lock braking system (ABS) for the passenger’s safety.Design/methodology/approachThe design methodology of the proposed newer mechanical ABS comprises of two units, namely, the braking unit and wheel lock prevention unit. The braking unit actuates the wheel stopping as and when the driver applies the brake, whereas the wheel lock prevention unit initiates wheel release to prevent locking and subsequent slip/skidding. The brake pedal with master cylinder assembly and double-arm cylinder forms the braking unit, brake pad cylinder, movable brake pad, solenoid valve and dynamo forms the wheel lock prevention unit. The dynamo coupled with the rotor energises/de-energises the solenoid values to direct airflow for applying brake and release it, which makes the system less energy-dependent.FindingsThe braking unit aids in vehicle stops, by locking the disc with the brake pad actuated by a double-arm cylinder. The dynamo energises the solenoid valve to activate the brake pad cylinder piston for applying the brake on the disc. Instantaneously, on applying the brake the dynamo de-energises the solenoid to divert the pneumatic flow for retracting the brake pad thereby minimizing the braking torque. The baking torque reduction revives the wheel rotating and prevents slip/skidding.Originality/valueMechanical ABS preventing wheel lock by torque reduction principle is a novel method that has not been evolved so far. The system was designed with repair/replacement of the parts and subcomponents to support higher affordability on safety grounds.

A Triboelectric Piston–Cylinder Assembly with Condition‐Monitoring and Self‐Powering Capabilities

The condition monitoring of piston–cylinder‐reciprocating machinery usually relies on vibration and acoustic sensors installed on the outer surface of cylinders. However, vibration and acoustic signals are susceptible to external interference from other accessories, and require an external power supply, which limits its widespread application. Herein, based on the lateral sliding mode of triboelectric nanogenerator (TENG), a novel reciprocating device with condition‐monitoring and self‐powering capabilities is proposed, called piston–cylinder triboelectric nanogenerator (PCTN). The effects of different factors, including mean piston speed, number of piston rings, materials of piston ring and cylinder, on the output characteristics of PCTN are investigated, respectively. Two typical fault cases, that is, piston ring missing and coil fracture, are investigated to verify the condition‐monitoring capability of PCTN. Piston ring missing faults can be effectively identified based on the variations in peak and root‐mean‐square (RMS) values of short‐circuit current (I sc). Coil fracture faults can be identified and located by analyzing changes in time–domain curve and time–‐frequency spectrum of I sc. Herein, a theoretical and experimental basis for the widespread application of PCTN in reciprocating machinery is provided.

Revisiting the Industrial Pneumatic Technology—An Innovative Development for an Increased Energetic Efficiency

Abstract A new pneumatic cylinder assembly is proposed as an alternative to classical cylinders which are well known for their poor energetic efficiency. The new system comprises an added expansion volume which permits to recover the energy content of a filled cylinder by a real thermodynamic expansion instead of simply releasing the filled air to the atmosphere. The energetic performance of the new system is evaluated and compared with the performance of an equivalent single cylinder producing the same mechanical work. The paper explains the operation principle and properties through numeric simulation and presents a small experimental prototype.

Simulation-driven parameter study of concentric Halbach cylinders for magnetorheological robotic grasping

Due to their peculiar property of controlled stiffness and strength under an external magnetic field, magnetorheological (MR) fluids show great potential in developing hybrid robotic grippers that in the future could offer the same versatility as the human hand. This demands for sufficiently strong, compact and switchable magnetic field sources for which permanent magnets are often overshadowed by electromagnets. However, permanent magnets possess higher magnetic flux densities per mass unit, and when assembled in certain ways, they allow to control their joint magnetic field. Within this paper, an extensive parameter study is conducted using grid search for the design of concentric Halbach cylinder assemblies based on finite element simulations. The influence of decisive geometric and material properties on the performance of these magnetic activation mechanisms is studied. These include the magnets’ shapes, sizes and number; the cylinders’ radii and number of pole pairs; and the relative permeabilities of the MR fluid and the grasped object. The performance of a design is measured by a multi-objective function that considers: the mean magnetic flux densities generated in the mechanism’s ON and OFF-state, the magnetic field’s inhomogeneity (i.e. standard deviation) in the ON-state, and the total magnet area for both cylinders. This work concludes by deriving guidelines for the most optimal design of concentric Halbach cylinders for a cylindrical radial bellow gripper.

Defluffing machine for dinanath grass seeds (Pennisetum pedicellatum)

Traditionally, defluffing (separation of nucleus seeds from fluffy seed) of dinanath grass seeds (Pennisetum pedicellatum) is cumbersome and time consuming. Hence, a defluffing machine consisting of feeding chute, feed rollers, serrated cylinder assembly, grading unit and power transmission unit was developed considering the physical properties of the dinanath seed and evaluated its performance at ICAR-Indian Grassland and Fodder Research Institute, Jhansi (2019). The mean values of seed dimensions (length × width × thickness) for fluffy seed and nucleus seed were computed as 6.20×2.77×1.83 mm3 and 2.44×0.82×0.58 mm3 respectively. The average bulk densities of fluffy and nucleus seeds were 7.65 kg/m3 and 613.63 kg/m3 respectively. The optimum machine performance like defluffing capacity (4.9 kg/h), defluffing efficiency (92.1%) and nucleus seed recovery (22.82%) were found at 7 % moisture content and 545 rpm of serrated cylinder speed about 76 % processing cost saving using the machine could be done as compared to traditional manual defluffing. Drastic reduction (99.7%) in volume of fluffy seed was achieved after defluffing.

Re-entrant transition as a bridge of broken ergodicity in confined monolayers of hexagonal prisms and cylinders

The entropy-driven monolayer assembly of hexagonal prisms and cylinders was studied under hard slit confinement. At the conditions investigated, the particles have two distinct and dynamically disconnected rotational states: unflipped and flipped, depending on whether their circular/hexagonal face is parallel or perpendicular to the wall plane. Importantly, these two rotational states cast distinct projection areas over the wall plane that favor either hexagonal or tetragonal packing. Monte Carlo simulations revealed a re-entrant melting transition where an intervening disordered Flipped-Unflipped (FUN) phase is sandwiched between a fourfold tetratic phase at high concentrations and a sixfold triangular solid at intermediate concentrations. The FUN phase contains a mixture of flipped and unflipped particles and is translationally and orientationally disordered. Complementary experiments were conducted with photolithographically fabricated cylindrical microparticles confined in a wedge cell. Both simulations and experiments show the formation of phases with comparable fraction of flipped particles and structure, i.e., the FUN phase, triangular solid, and tetratic phase, indicating that both approaches sample analogous basins of particle-orientation phase-space. The phase behavior of hexagonal prisms in a soft-repulsive wall model was also investigated to exemplify how tunable particle–wall interactions can provide an experimentally viable strategy to dynamically bridge the flipped and unflipped states.

The phycobilisome core-membrane linkers from Synechocystis sp. PCC 6803 and red-algae assemble in the same topology.

The phycobilisomes (PBSs) of cyanobacteria and red-algae are unique megadaltons light-harvesting protein-pigment complexes that utilize bilin derivatives for light absorption and energy transfer. Recently, the high-resolution molecular structures of red-algal PBSs revealed how the multi-domain core-membrane linker (LCM ) specifically organizes the allophycocyanin subunits in the PBS's core. But, the topology of LCM in these structures was different than that suggested for cyanobacterial PBSs based on lower-resolution structures. Particularly, the model for cyanobacteria assumed that the Arm2 domain of LCM connects the two basal allophycocyanin cylinders, whereas the red-algal PBS structures revealed that Arm2 is partly buried in the core of one basal cylinder and connects it to the top cylinder. Here, we show by biochemical analysis of mutations in the apcE gene that encodes LCM , that the cyanobacterial and red-algal LCM topologies are actually the same. We found that removing the top cylinder linker domain in LCM splits the PBS core longitudinally into two separate basal cylinders. Deleting either all or part of the helix-loop-helix domain at the N-terminal end of Arm2, disassembled the basal cylinders and resulted in degradation of the part containing the terminal emitter, ApcD. Deleting the following 30 amino-acids loop severely affected the assembly of the basal cylinders, but further deletion of the amino-acids at the C-terminal half of Arm2 had only minor effects on this assembly. Altogether, the biochemical data are consistent with the red-algal LCM topology, suggesting that the PBS cores in cyanobacteria and red-algae assemble in the same way.

Optimisation of various thermodynamic parameters for minimum temperature gradient along cylinder liner

In a piston cylinder assembly, high temperatures are found in cylinder combustion spaces and the cylinder temperature is maintained by the water flowing through the engine jacket. Heat transfer takes place from in-cylinder gases to liner, from the liner to the coolant in the jacket. Generally, the water is treated as the most effective coolant, but the boiling point is raised by the coolant which is glycol based. It also gives lubrication to the pump seal, reduces the liner deterioration/wear and inhibits/avoids freezing. In the current research, different coolant mixture fractions at different flow rates, at various crank angles, are investigated for the control of the cooling rate which subsequently reduces liner distortion. The three-dimensional computational fluid dynamic (CFD) simulation is done here. Here the conjugate heat transfer analysis is used to investigate the heat transfer rate during the cooling in jacket of the engine by means of CFD. The CFD simulation results were certified/confirmed by laboratory tests performed in similar conditions.