External Ribs Research Articles

Research on Reinforcement Technology for Cover Beam Structures of in-service Bridge

In order to determine a suitable reinforcement technology for the cover beam structure of a bridge in service, a model of a bridge in Shanxi Province was created and analyzed. Three different reinforcement methods were simulated using the finite element method, and these methods were then compared and analyzed. The results indicate that all three reinforcement methods can enhance the bridge’s performance, with the effectiveness ranked as follows: increasing the cross-section, applying external prestress, and attaching steel sheets. Considering factors such as economy, feasibility, and safety, it is recommended to reinforce the cover beam of the bridge by strengthening the external prestressed ribs in combination with affixing steel plates. This approach not only effectively reduces the stress and displacement of the cover beam structure but also redistributes the stress on the cover beam. Importantly, this method does not hinder bridge traffic and minimizes the impact on the clearance under the bridge.

Study on generating rolling method for manufacturing cylindrical parts with external cross ribs

As the main structure of launch vehicle, cylindrical parts with reinforced ribs are mainly manufactured by milling, rolling and welding methods, which have a long manufacturing cycle and low material utilization. This paper proposes a new generating rolling method for manufacturing cylindrical parts with external cross ribs integrally. The generating rolling device is developed, the flow mechanism of cylindrical parts with external cross ribs is revealed and methods to minimize the underfill defects of ribs are proposed. Simulation and experiment results show that longitudinal rib is mainly formed by gradual material accumulation in the groove under circumferential compressive strain, and transverse rib is mainly formed by gradual material accumulation in the groove under axial compressive strain. Compared with longitudinal or transverse rib, the material flow of cross rib is more difficult due to small circumferential and axial compressive strain, resulting in the underfill phenomenon. Rib structure also affects the flow of material. When the rib sparsity is large or the height-width ratio is small, the rib is subjected to small radial tensile strain and circumferential compressive strain, resulting in low rib height and uneven rib filling. The proposed forward and reverse rolling method and billet preforming method can reduce the defects of uneven filling of longitudinal rib and underfill of cross rib.

Effect of the Configuration and Shape of External Ribs of Sealed Enclosures of Electronic Devices on Heat Removal Efficiency

Introduction. Modern computing and electronic devices are constructed on the basis of radio-electronic components, such as processors, graphics processing units, etc. During operation, these components emit tens of watts of thermal energy. Therefore, effective excess heat removal from both semiconductor electronic devices and electronic systems as a whole through the use of passive or active cooling systems represents an important research problem. Aim. To study the influence of the configuration and shape of external ribs of sealed enclosures of electronic devices, which use solely passive cooling systems inside, on the efficiency of heat removal from the processor for eachenclosure design under consideration based on their comparative analysis. Materials and methods. Simulation experiments were carried out using 3D parametric models of various device types, which were developed in the SolidWorks Flow Simulation software environment. These models differed in terms of configuration of thermal channels formed by the external enclosure ribs. Results. The conducted simulation experiments allowed the authors to study the cooling process of processors installed in modern electronic devices. The influence of the configuration and shape of the enclosure ribs on excess heat removal from the processor was studied in a passive cooling mode and when blowing the devices with air moving from above (perpendicular to the cover) or laterally (parallel to the cover) with a gradual increase in a processor power from 10 to 25 W. A ribbed enclosure with passive cooling was shown to ensure a more effective heat removal from a 10 W processor compared to a non-ribbed enclosure (the temperature drop is 4.1 °C). For a 25 W processor, this value comprises 11.01 °C. When blowing the device, the direction (perpendicular or parallel) of air movement significantly affects the cooling efficiency of the heated surface (with a processor power of 45 W, the difference is more than 10 °C). Conclusion. The developed 3D models effectively simulate the cooling system of heat-loaded high-power radio-electronic components located in sealed enclosures, due to the implementation of their external ribbing.

Compressive performance of welded hollow spherical joints with external triangular ribs

This study addresses the axial compressive performance of welded hollow spherical (WHS) joints with external triangular ribs. External triangular ribs are able to postpone the local buckling of the joint during axial loading, and thus strengthen the compressive capacity of it. A simplified analytical model is proposed to elucidate the stress distribution on the hollow sphere of axial-loaded WHS joints with external triangular ribs. Then a simplified solution for the yield strength of axial-loaded WHS joints is deduced based on the elastic thin shell theory. The simplified solution indicates that the yield strength of WHS joints with external triangular ribs can be expressed by a coefficient related to the specifications of the ribs and the joints multiply by that of WHS joints without external ribs. Compression tests on 6 full-scale specimens of WHS joints with varied configurations of triangular ribs are conducted. It shows that the failure mode and the strength enhancement of the specimens vary as the specification of the triangular ribs change, and the triangular ribs enhance the strength of the joints up to 77 %. A refined FE model is established and calibrated against the findings from the experiments. Parametric studies on the design parameters which may affect the compressive response of the WHS joints with triangular ribs are fully investigated. It is shown that the compressive yield strength of the joint rises with the increase of the number, height and thickness of the triangular ribs, and decreases with the increase of the angle-of-elevation of the triangular ribs. It is also shown that the effect of the ratio of the diameter of the sphere to that of the steel tube on the compressive yield strength of the joint is much lighter than the others, and deemed as negligible. Regression analysis on the experimental and numerical data is carried out to obtain a practical formula for the compressive capacity of WHS joints with external triangular ribs. This formula is incorporated with the previously developed formula for the compressive capacity of WHS joints with external trapezoidal ribs, to form a general formula applicable for WHS joints with either external triangular ribs or external trapezoidal ribs.

An alternative solution for insulating a burning chamber with high temperature walls

Usually, the industrial halls, who are in most cases poorly insulated and have high permeability, are heated with hot air generators or convecto-radiators. Using convecto-radiators is improper and hot air generators, although it is more appropriate, it consumes a very high amount of energy. This paper continues the topic discussed in a previous article [1] in which we presented an alternative heating solution to the existing ones. The heating system mentioned uses an environmentally friendly and cheap fuel (biomass). This paper presents an alternative solution to insulate a burning chamber (BC) with high temperature walls that uses pellets as fuel. This technical solution has the benefit of supplying heating agents to various types of heat consumers and to optimize the construction costs through the materials used. The BC is design with external ribs on here longitudinal direction. For insulating and cooling the BC, a metallic case was design through which atmospheric air is circulated. Three constructive solutions of BCs were analysed. The paper presents the modelling results of the constructive solutions and the calculation method. The calculation was made applying the physical laws that govern this type of heat transfer and was made with discretization segments. Determining the parameters of each segment will allow the user to optimize the equipment design. The main purpose of the study is to conceive an alternative technical solution for insulating the BC, that should be cheaper, easy to implement and able to prepare a second thermal agent for heating.

Optimization of Flat Ends in Pressure Vessels.

The application of flat ends in pressure boilers is inevitably associated with the presence of stress concentration, which is observed in the vicinity of the junction of the cylinder and the closing flat plate. The analyzed flat end plates with stress relief grooves fall into the group of solutions recognized by the respective Standards of Calculations of Pressure Vessels. Unfortunately, no clear evidence is given in the Standards on how to choose the best groove parameters. This opens up the problem of the optimal choice of the groove parameters providing a minimum stress level. Even for the optimal values defining the stress relief groove geometry, certain plastic deformations are observed in the groove area for materials which exhibit elastic-plastic properties. Such a situation is completely unacceptable during exploitation, and a suitable reduction of the operating pressure is necessary. This paper discusses the effectiveness of other designs for flat ends used in pressure vessels. The proposed modifications took the form of external ribs applied around the top of the endplate circumference. The dimensions of these ribs were set using parametric optimization. The results of the study encouraged the authors to perform a more general analysis with the use of topology optimization. The results of all performed studies proved that the reduction of stress concentration and the full elimination of plastic deformation are possible. All numerical calculations were made using the finite element code (FEM), Ansys.

A linear guide-based actuation concept for a novel morphing aileron

ABSTRACTThis paper deals with the actuation system design of a full-scale morphing aileron for regional aircraft. The aileron is allowed to smoothly change its geometrical configuration and perform the in-flight transition from a baseline shape to a set of optimal morphed ones pre-defined on the basis of aerodynamic requirements. The design of such innovative aileron is aimed not only at substituting the conventional aileron installed on a real aircraft but also to provide additional functionality. The aileron is free to rotate around its main hinge axis and it is also allowed to smoothly modify camber with two independent actuation systems. In such manner it can be used also during cruise with a symmetric deflection between the two half wings in order to reduce drag in off design condition. To accomplish variable aileron shape, a rigid-body mechanism was designed. The proposed aileron architecture is characterised by segmented adaptive ribs rigidly linked each other with spanwise reinforcements such as spars and stringers in a multi-box arrangement. Each rib is split into two movable plates connected by means of rotational hinges in a finger-like mechanism. The mechanism is driven by a load-bearing actuator by means of a kinematic chain opportunely tied based on the structural requirements in terms of shape to be matched and load to be withstood. The proposed device is an innovative arrangement of the quick-return mechanism composed of a beam leverage, commercial linear guides and a crank. The actuator shaft is directly inserted in the crank, which transmits the rotation to the linear guide that slide along a rail moving upward or downward the beam thus resulting in a camber variation. The entire aileron is moved by three leverages internally contained and distributed along the first two bays while the most external ribs are considered passive and their movement slaved. Two actuation layouts are analytically and numerically studied, the analytical theory is presented and validated by means of a multi-body simulation. Moreover, a linear static analysis was carried out under the hypothesis of glued contact between linear guides components simulating a jamming condition. This assumption has been formulated because it represents the most severe condition that envelop all the operative loads to which the actuation system is subjected. The analyses conducted are preliminarily aimed to verify that no failure occur under the imposed loads. In this first design loop, the vertical static force acting on the linear carriage exceeded allowable value and then a new configuration with double-sided linear guides was then investigated.

The effect of external helical ribs tube on the heat transfer and pressure drop performance for multi - tube heat exchanger

The pressure drop and heat transfer characteristic for cross flow of turbulent air over helical rectangular ribs tubes heat exchanger were studied experimentally and numerically. The study includes the design and manufacturing of four models of multi-tube heat exchangers. Each model has three tubes in a line arrangement. Experiments were performed for Reynolds number range from (7200–31400) using different rib pitch to diameter ratios (P/D = 1.3, 1.5 and 1.8) with different ribs pitch angles. The height to diameter ratio of rib (h/D = 0.05) and width to diameter ratio is (w/D = 2) were fixed. The water flows with different rates inside the tubes with a range of (2, 3, 4, 5, 6 and 7) L/min. Three values for the inlet water temperatures to test tube were used. In the present numerical part, commercial software ANSYS Fluent 16.2 was employed to determine the heat transfer coefficient and pressure drop for the different models of cross flow heat exchangers. The results declared that the average Nusselt number and Pressure drop of the corrugated model has a relatively high different from that of the smooth models. In addition, the experimental and numerical were compared and gave a good agreement between them.

New insights into Mesozoic cycad evolution: an exploration of anatomically preserved Cycadaceae seeds from the Jurassic Oxford Clay biota

Most knowledge concerning Mesozoic Era floras has come from compression fossils. This has been augmented in the last 20 years by rarer permineralized material showing cellular preservation. Here, we describe a new genus of anatomically preserved gymnosperm seed from the Callovian–Oxfordian (Jurassic) Oxford Clay Formation (UK), using a combination of traditional sectioning and synchrotron radiation X-ray micro-tomography (SRXMT). Oxfordiana motturii gen. et sp. nov. is large and bilaterally symmetrical. It has prominent external ribs, and has a three-layered integument comprising: a narrow outer layer of thick walled cells; a thick middle parenchymatous layer; and innermost a thin fleshy layer. The integument has a longitudinal interior groove and micropyle, enveloping a nucellus with a small pollen chamber. The large size, bilateral symmetry and integumentary groove demonstrate an affinity for the new species within the cycads. Moreover, the internal groove in extant taxa is an autapomorphy of the genus Cycas, where it facilitates seed germination. Based upon the unique seed germination mechanism shared with living species of the Cycadaceae, we conclude that O. motturii is a member of the stem-group lineage leading to Cycas after the Jurassic divergence of the Cycadaceae from other extant cycads. SRXMT—for the first time successfully applied to fossils already prepared as slides—reveals the distribution of different mineral phases within the fossil, and allows us to evaluate the taphonomy of Oxfordiana. An early pyrite phase replicates the external surfaces of individual cells, a later carbonate component infilling void spaces. The resulting taphonomic model suggests that the relatively small size of the fossils was key to their exceptional preservation, concentrating sulfate-reducing bacteria in a locally closed microenvironment and thus facilitating soft-tissue permineralization.

Determination of the crack-initiation and propagation conditions in a styrene-acrylonitrile water-filter housing with external ribs based on destructive pressure tests

Abstract Fatigue cracks were initiated during the operation of a water-filter housing made from styrene-acrylonitrile (SAN). Using a destructive pressure test, it was confirmed that the sharp transition between the wall and the vertical external ribs of the filter housing at the point of the increased external diameter is the critical area of the water-filter housing. This is a consequence of the stress concentration due to the combined action of the sharp edges of the vertical external ribs and the increased stiffness due to the thicker wall and the mounting of the upper part of the housing onto the filter head. During the destructive pressure tests a crack was initiated on the external surface in the same place and spread in the same direction as the fatigue crack during the operation of the water filter. At the critical point the actual loads due to the stress concentrator are approximately 3.2 times higher than that expected based on the water pressure in the pipeline. The tensile strength of the styrene-acrylonitrile from the water-filter housing was comparable with the literature data. The fracture toughness of styrene-acrylonitrile is low and comparable to the fracture toughness of polymethylmethacrylate. The critical crack depth for the occurrence of an uncontrolled rupture for a continuously increasing load is approximately 100 μm, while the plane-strain condition occurs at a thickness of about 1 mm. A rapidly growing crack in the wall tends to grow in a layer of plane-strain conditions, and from the internal- to the external-wall surface. The possibility of determining the fracture toughness with a destructive pressure test of the housing or a pressure vessel with an external surface stress concentrator was achieved.

Capacity of a nineteenth century iron-arch bridge in Leeds, UK

Leeds Bridge crosses the River Aire in the city centre of Leeds, UK. Built in 1871, this grade II-listed iron-arch structure is currently restricted to vehicles over 7·5 t (other than buses and fire engines) due to a weak deck. A proposed trolleybus system was planned to go over the bridge, requiring it to be reassessed. The single 32 m skew span bridge is made up of ten arched ribs – two external ribs made from cast iron with the eight internal ribs, plus all the cross-girders and bracing, made from wrought iron. This paper describes the assessment of the bridge using a three-dimensional space-frame model supplemented by a three-dimensional finite-element model of one rib. The assessment concluded that the strengthening requirements to carry the required vehicle loading would be limited to replacement of the mass concrete infill.

Numerical modeling and experimental validation of axially loaded slender sandwich panels with soft core and various rib configurations

In this paper experimental and analytical investigations of axially loaded sandwich panels are presented. Large scale slender panels with and without ribs were tested. A robust analytical model applicable to panels of various slenderness ratios was developed. It accounts for geometric non-linearity through a rigorous P-Delta analysis, including the initial out-of-straightness profile and end eccentricities. The excessive shear deformation of the soft core and its effect on the overall stiffness and global buckling is accounted for. Additionally, the model detects localized skin wrinkling or crushing. The model showed reasonable agreement, within ±20%, with test results for strength and stiffness and was used in a parametric study. It was shown that the addition of a longitudinal rib connecting the skins at mid-width resulted in 180% increase in axial strength, by changing failure mode from skin wrinkling to global buckling. Adding longitudinal external ribs to the internal one changed failure mode to skin crushing and increased stiffness by 40% but did not enhance strength. Axial stiffness and strength also increased as skins or ribs became thicker, or their Young’s modulus increased, or as core shear modulus increased, however, failure mode varied depending on length. As the amplitude of out-of-straightness increased, failure load always reduced, weather governed by global buckling or skin wrinkling.

Analyses of a leaking styrene-acrylonitrile water-filter housing

Fatigue cracks were found in water-filter housings made of styrene-acrylonitrile. These cracks initiated on the external surface, along the sharp corner between the wall of the housing and the vertical external ribs or at a pre-existing crack in the base of the water-filter housing. The reason for the crack was the high stress concentration due to an inappropriate design or the poor quality of the filter housing in combination with water-pressure impacts during the operation of an electromagnetic water valve and taps.

Evaluation of the seismic performance of composite bridge pier consisting of steel pipes with external ribs and concrete using limit displacement method

Evaluation of the seismic performance of composite bridge pier consisting of steel pipes with external ribs and concrete using limit displacement method

Detection and Tracking Strategies for Autonomous Aerial Refuelling Tasks Based on Monocular Vision

Detection and tracking strategies based on monocular vision are proposed for autonomous aerial refuelling tasks. The drogue attached to the fuel tanker aircraft has two important features. The grey values of the drogue's inner part are different from the external umbrella ribs, as shown in the image. The shape of the drogue's inner dark part is nearly circular. According to crucial prior knowledge, the rough and fine positioning algorithms are designed to detect the drogue. Particle filter based on the drogue's shape is proposed to track the drogue. A strategy to switch between detection and tracking is proposed to improve the robustness of the algorithms. The inner dark part of the drogue is segmented precisely in the detecting and tracking process and the segmented circular part can be used to measure its spatial position. The experimental results show that the proposed method has good performance in real-time and satisfied robustness and positioning accuracy.

Molluscan marginalia: hidden morphological diversity at the bivalve shell edge

Molluscan shells exhibit a high and largely neglected diversity of serrations and crenulations at the growing margin. A survey of living and Cenozoic fossil bivalves indicates that serrations, in which the external ribs or interspaces between ribs extend radially beyond the general contour of the valve margin, may be symmetrical or asymmetrical. Projections whose adumbonal edge more nearly parallels the shell edge than the abumbonal edge occur on the posterior valve margins of many limids, cardiids and donacids, as well as in the arcid Anadara and a few concentrically ridged tellinids. In many cardiids, posterior serrations form as extensions of ribs, whereas ventral and anterior projections are extensions of rib interspaces. Asymmetrical serrations are almost always found on shell edges that are polished, indicating that the mantle extends slightly over the valve margin to the outside. I tentatively suggest that asymmetrical serrations enable the valves to close around siphons or other mantle extensions without injuring these soft tissues, so that the bivalve can maintain sensory contact with the environment even while the shell is shut. A preliminary comparison with brachiopods indicates that the diversity of conditions at the shell edge is much higher in bivalves. Together with the largely warm-water and marine distribution of marginal modifications in bivalves, these comparisons reflect the higher metabolic potentials of bivalves relative to brachiopods, and show that the shell edge is a rich source of evidence about function and mode of life in fossils.

Ultrastructure of excretory system in Bothrioplana semperi (Platyhelminthes, Turbellaria)

The ultrastructure of flame bulbs and epithelium of excretory canals in Bothrioplana semperi (Turbellaria, Seriata) have been studied. The flame bulbs consist of two cells, the terminal cell and the proximal canal cell. The weir is formed by two rows of longitudinal ribs. The ribs of the internal row originate from the flame cell, external ribs are formed by the proximal canal cell. Each external rib has a remarkable bundle of microfilaments, originating in the cytoplasm of the first canal cell distally to the bases of external ribs. Membrane of internal ribs is marked by small electrondense granules, separate or fused to an electron-dense layer, continuous to dense “membrane,” connecting both external and internal ribs. Sparse internal leptotrichs originate from the bottom of the flame bulb cavity. External leptotrichs are lacking. Septate junction is present only in proximal canal cell at the level of tips of cilia. The apical surface of the canal cell bears rare short microvilli. The basal membrane of canal cells forms long invaginations that may reach nearly the apical membrane. The epithelium of excretory canals lacks the cilia. The ultrastructure of flame bulbs and epithelium of the excretory canals in B. semperi shares representatives of suborder Proseriata (Seriata). The contradiction exists in interpretation of the structure of flame bulbs in Proseriata. Ehlers and Sopott-Ehlers assumed that the external ribs are derivatives of the proximal canal cell and internal ones are outgrowths of the terminal cell, while Rohde has found conversely: the external ribs are outgrowths of the terminal cell, the internal ones are outgrowths of the proximal canal cell. However, the illustrations provided by Rohde do not enable to ascertain what cells the internal and external ribs derive from, while illustrations provided by Ehlers justify his interpretation. The order of weir formation in B. semperi confirms the viewpoint of Ehlers. The implication of ultrastructure of flame bulbs in Proseriata, especially of the order of flame bulb formation, in the Platyhelminthes phylogeny has been discussed.

Modeling wind ribs effects for numerical simulation external pressure load on a cooling tower of KAZERUN power plant-IRAN

In this paper, computer simulation of wind flow around a single cooling tower with louver support at the base in the KAZERUN power station in south part of IRAN is presented as a case study. ANSYS FLOTRAN, an unstructured finite element incompressible flow solver, is used for numerical investigation of wind induced pressure load on a single cooling tower. Since the effects of the wind ribs on external surface of the cooling tower shell which plays important role in formation of turbulent flow field, an innovative relation is introduced for modeling the effects of wind ribs on computation of wind pressure on cooling tower's shell. The introduced relation which follows the concept of equivalent sand roughness for the wall function is used in conjunction with two equations <TEX>${\kappa}-{\varepsilon}$</TEX> turbulent model. In this work, the effects of variation in the height/spacing ratio of external wind ribs are numerically investigated. Conclusions are made by comparison between computed pressure loads on external surface of cooling tower and the VGB (German guideline for cooling tower design) suggestions.

Compressible hearing aid

A compressible hearing aid includes an exterior deformable skin (12) which bounds an internal region which is filled, at least in part, with an open-cell foam (18), the foam can be wrapped around or molded to contain an audio output transducer (16a-2). The skin is not self-supporting and in response to applied forces from user's ear canal, the skin and the foam both deform and readily compress exhibiting a reduced volume. Though compressed, the foam exerts an outward force against the skin thereby continuing to form an elongated seal between the skin and the external periphery of the user's dynamically changing ear canal. As the volume of the ear canal increases, the skin and open-cell foam expand, exhibiting an increased internal volume, while maintaining a comfortable seal with the ear canal. A plurality of external ribs (12'-1) carried on the skin not only reduces feedback but promotes drying of the ear canal and promotes retention of the hearing aid in the ear canal.

Changes in Hydraulic Roughness Coefficients for Circumferentially Strained M294 Pipe

When a culvert or storm drainage pipe is being sized on the basis of discharge capacity requirements, knowledge of the hydraulic roughness of the pipe is required. Hydraulic roughness is typically influenced by both the roughness of the pipe material and the inside pipe wall profile (e.g., smooth, corrugated, etc.). When subjected to external loads associated with field installations (e.g., backfill, compaction, etc.), the inside wall profile of thermal-plastic pipe products, like high-density polyethylene (HDPE) M294 drainage pipe, often changes due to circumferential strain. As lined HDPE pipe strains circumferentially, the structural external ribs reduce in diameter, which causes the inside liner to develop a longitudinal corrugated wall profile. Variations in the hydraulic roughness of M294 Type S drainage pipe with 24-in. (0.61-m) diameter that were based on external circumferential strain rates ranging from approximately 0 to 2.4% were identified in this study, conducted at the Utah Water Research L...