Outer Web Research Articles

Study on the forming quality of double-base gun propellants based on extrusion 3D printing technology

In order to improve the forming quality of 3D printed gun propellants, rosette-shaped 19-perf double-base gun propellants with different geometric dimensions (inner diameter and web thickness) were printed by extrusion 3D printing technology based on conventional double-base propellant formulations. The printed gun propellants were characterized in terms of surface structure, inner diameter and web thickness dimensional uniformity, and density. The effects of geometrical dimensions (inner diameter and web thickness) and printing process parameters (line width and flow compensation) on the forming quality of gun propellant were studied. The results showed that printed rosette-shaped 19-perf double-base gun propellants have a good surface structure with a clear outer profile and inner diameter from 1.5 mm to 3.0 mm. When the printing process parameters were the same, the larger the geometry, the higher the dimensional uniformity of the printed gun propellant. When the printing model was the same, the decrease in printing line width and the increase of printing flow compensation in the printing process parameters had the same effect on the dimensional uniformity of the printed gun propellant. The rosette-shaped 19-perf gun propellant with a model inner diameter and web thickness of 1.5 mm had the best dimensional uniformity at the printed line width and flux compensation of 0.45 mm and 1.0, respectively, with relative standard deviations of 2.699%, 1.986%, and 2.458% for inner diameter, inner and outer web thickness, respectively. The density of the printed propellant ranged from 1.565 to 1.606 g·cm−3. This study has a guiding significance for the application of extrusion 3D printing technology in the field of gun propellant.

The Effect of Preload Loss on the Mechanical Properties of Grid Structure Connected with Bolted-Ball Joints

Bolt-ball joints are widely adopted in grid structures due to their high installation accuracy and short construction period. Since the bolt is inside the joint, it is challenging to evaluate its health status from outside the structure. A finite-element plane-truss structure model, based on the actual grid structure, was constructed to investigate the influence of the rod’s preload on the overall stiffness and bearing capacity of the grid structure. Moreover, a model of the grid structure, with a bolt-ball joint connection, was constructed to analyze the influence of the preload loss in bolted-ball joints on the overall mechanical performance of the local members and structures. The results show that the release of preload on the outer web rod is less effective in terms of the overall stiffness and bearing capacity of the structure than on the inner web rod. The preload of the larger span direction rod plays an important role, and the preload of the upper chord has a greater impact, while the preload of the web rod and the upper chord in the smaller span direction has no significant effect on the normal stress in the surrounding rods.

Structural Response of an Extra-Wide Concrete Self-Anchored Suspension Bridge under Static Vehicle Loads: Testing and Numerical Simulations

The finite element (FE) analysis by ANSYS software based on field test was used to study the structural performance of an extra-wide concrete self-anchored suspension bridge under static vehicle loads. The longitudinal, transverse and vertical stresses of the extra-wide girder were analyzed, and the changing criteria of girder stresses induced by vehicle loads were presented. Additionally, the effects of the shear lag on extra-wide box girders were investigated. The results showed that the maximum shear lag coefficient was 1.89 at the junction of bottom plate and outer web at the middle of midspan. Moreover, the non-uniformity of cable force is perceptible under eccentric load. Furthermore, an optimization measure for comparable bridges and essential health monitoring locations were outlined.

Effect of Forming Parameters on Profile Thinning of Flexible 3D Multi-Point Stretch Bending

The ABAQUS finite element simulation software is used to simulate the flexible multi-point three-dimensional stretch bending process of aluminum profiles. The effect of process parameters on the web thickness of rectangular profile in flexible multi-point three-dimensional stretch bending is studied by orthogonal experiment and range analysis. The process parameters used in the experiments include pre-stretching value, post-stretching value, the number of multi-point dies and friction coefficient. The optimal combination of process parameters is obtained by numerical simulation and experimental verification. When the aluminum profile is completed flexible multi-point stretch bending according to the best parameters, the thickness thinning of outer web and inner web is the smallest. The experimental result is closed to the numerical simulated results. The effectiveness of the numerical simulation is verified by the corresponding experimental methods.

Using Fiber Optic Sensors for Bridge Monitoring

This paper presents the data obtained from monitoring a steel Struss bridge using Fiber Bragg Grating (FBG) sensors before and after a proposed repair for a crack propagation in the end plates. This paper details the operating mechanism behind the FBG sensors and advantages of using FBG sensors over resistive foil strain gauges for bridge structural health monitoring and also details how cracks on the outer web’s end plate originated and then provides a step-by-step guide to the completed repair. This technology can be use in other practical applications where structural health monitoring is needed.

Effects of global and local ply-reinforcements of critical components on crush performances of 2D tri-axially braided CFRP J-shaped fuselage frame

With the development of aircraft industry, there is an urgent demand for pursuing higher crashworthiness design standard of fuselage. However, there is a challenge for improving the crush performances of fuselage with low design and fabrication cost. To explore optimal design areas, effects of global and local ply-reinforcements of critical components on crush performances of 2D tri-axially braided CFRP J-shaped fuselage frame are predicted with validated continuum damage model. The finite element model composed of three critical components (e.g. outer flange, web, and inner flange) can accurately predict the experimental maximum failure load and breakage mode. Then, the crush behaviours of fuselage frame with global and local ply-reinforcements are respectively compared among three parts. It is found that local ply-reinforcements slightly increase structural stiffness, failure load, and SEA but global ply-reinforcements present greater improvements, especially for the outer flange and web. Further, effects of ply number of each part on crush behaviours of fuselage frame are predicted. Results show that increasing ply number presents higher performances but the SEA only increases for global ply-reinforcement of outer flange. It is concluded that globally reinforcing the outer flange has the highest reinforcement efficiency with a low increase of weight. This study provides a preferential reinforcement design idea for the fuselage to keep the light-weight and high-strength.

Simulation of winding web on surface winder (Stress distribution, tension and slippage of wound roll)

Surface winding processes are simulated up to 49-70 laps by means of a FEM commercial software. The simulation model is composed of a flexible web with linear-isotropic nature, rigid core and rigid drum (or rigid two drums and a rider roll). Stress distributions of wound rolls, tension (tangential stress) change during winding and layer slippage are investigated. The main results are as follows. In case of single-drum surface winding, the roll stresses become larger as a friction coefficient between web layers, nip load, drum diameter or a line tension increases, or Young’s modulus decreases. Poisson’s ratio has little effect. The roll stresses depend on not only WIT (increased tension of the outermost layer due to the nip load), but a decreasing rate of tension at a web point during winding, and they have a cross relation with a value obtained by integrating a web tension varying curve from the start point where the web enters the roll to the end of winding. In case of two-drum surface winding with differential drum speeds, the web tension varies complicatedly at three nip zones and is larger between the rider roll and the second drum. The tension of the outermost layer decreases with increase in the roll diameter. The slippage occurs as the outer web layer pulls the inner in the roll rotational direction and is larger at the outer web layers. When speeds of the two drums are equal, the first drum drives the roll and the tension is larger between the second and the first drum. The slippage is the same as the differential drum speed case in the range of 2/3 of the roll thickness, but in the rest range, the slippage occurs in the opposite direction.

Theoretical Investigations for the Verification of Shear Centre and Deflection of Sigma Section by Back Propagation Neural Network Using Python

AbstractThe most important challenges in the construction field is to do the experimentation of the designing at real time. It leads to the wastage of the materials and time consuming process. In this paper, an artificial neural network based model for the verification of sigma section characteristics like shear centre and deflection are designed and verified. The physical properties like weight, depth, flange, lip, outer web, thickness, and area to bring shear centre are used in the model. Similarly, weight, purlin centres with allowable loading of different values used in the model for deflection verification. The overall average error rate as 1.278 percent to the shear centre and 2.967 percent to the deflection are achieved by the model successfully. The proposed model will act as supportive tool to the steel roof constructors, engineers, and designers who are involved in construction as well as in the section fabricators industry.

INFLUENCE OF CURVED WEB CLOSED STEEL SECTIONS IN BRIDGE DESIGN

A bridge is nowadays more than a structure that connects people over an obstacle. When a bridge has to be built in an urban area, either it has to be a landmark or it should blend away in the environment. The use of curved steel panels is one option to obtain these requirements. However, due to a lack of knowledge, engineers end up with a conservative design to implement these structural elements. For that reason, a Finite Element Model is made of a railway bridge, where the outer webs of the main girders have a varying web curvature. Six different models are made and compared. The most important parameters that are compared are the deformations and the stresses in the webs. The study finds that curved webs have an equal or even better behavior than flat webs, even with smaller web thickness. This makes that designers can use curved webs in their design, without needing extra steel to make their design safe.

A High-Frequency Model of a Circular Beam with a T-Shaped Cross Section

This paper derives an analytical model of a circular beam with a T-shaped cross section for use in the high-frequency range, defined here as approximately 1 to 50 kHz. The T-shaped cross section is composed of an outer web and an inner flange. The web in-plane motion is modeled with two-dimensional elasticity equations of motion, and the left portion and right portion of the flange are modeled separately with Timoshenko shell equations. The differential equations are solved with unknown wave propagation coefficients multiplied by Bessel and exponential spatial domain functions. These are inserted into constraint and equilibrium equations at the intersection of the web and flange and into boundary conditions at the edges of the system. Two separate cases are formulated: structural axisymmetric motion and structural non-axisymmetric motion and these results are added together for the total solution. The axisymmetric case produces 14 linear algebraic equations and the non-axisymmetric case produces 24 linear algebraic equations. These are solved to yield the wave propagation coefficients, and this gives a corresponding solution to the displacement field in the radial and tangential directions. The dynamics of the longitudinal direction are discussed but are not solved in this paper. An example problem is formulated and compared to solutions from fully elastic finite element modeling. It is shown that the accurate frequency range of this new model compares very favorably to finite element analysis up to 47 kHz. This new analytical model is about four magnitudes faster in computation time than the corresponding finite element models.

A high-frequency model of a circular beam with a T-shaped cross section

This paper derives an analytical model of a circular beam with a T-shaped cross section for use in the high-frequency range, defined here as approximately 1 to 50 kHz. The T-shaped cross section is composed of an outer web and an inner flange. The web in-plane motion is modeled with two-dimensional elasticity equations of motion, and the left portion and right portion of the flange are modeled separately with Timoshenko shell equations. The differential equations are solved with unknown wave propagation coefficients multiplied by Bessel and exponential spatial domain functions. These are inserted into constraint and equilibrium equations at the intersection of the web and flange and into boundary conditions at the edges of the system. Two separate cases are formulated: structural axisymmetric motion and structural non-axisymmetric motion and these results are added together for the total solution. The axisymmetric case produces 14 linear algebraic equations and the non-axisymmetric case produces 24 linear algebraic equations. These are solved to yield the wave propagation coefficients, and this gives a corresponding solution to the displacement field in the radial and tangential directions. The dynamics of the longitudinal direction are discussed but are not solved in this paper. An example problem is formulated and compared to solutions from fully elastic finite element modeling. It is shown that the accurate frequency range of this new model compares very favorably to finite element analysis up to 47 kHz. This new analytical model is about four magnitudes faster in computation time than the corresponding finite element models.

Experimental and numerical investigation on assessing local bearing behavior of a pultruded GFRP bridge deck

In this study, a methodology proposing size reduction of flat steel bearing plates that are commonly used in experimentally evaluating composite deck to transfer and distribute simulated vehicles loads to the top of bridge deck specimens is presented. The proposed methodology considers the tire-to-deck effects based on both a contact pressure distribution model and finite element (FE) simulation results. Ultimate capacity and associated failure modes for the following two loading cases: (i) moment-dominated, and (ii) moment-shear coupled loads were experimentally evaluated. Experimental results showed that the ultimate capacity for moment-dominated loading case is 35.60 kN, while capacity for the same composite deck when subjected to a moment-shear coupled load is 44.34 kN. Experimental results indicated that the initiation of failure for both loading cases was in the form of the development of longitudinal cracks at both top flanges and at outer web section near the loading side. Finite element models that consider lamina damage were developed and analyzed. A good agreement between numerical and experimental results is achieved.

Yachihe Bridge, China: engineering the world’s longest cable-stayed steel truss

Yachihe Bridge in China is the longest steel-truss, cable-stayed bridge in the world and the tenth longest overall. Completed in 2016, its 800 m main span carries the new Guiyang–Qianxi dual carriageway over the Yachihe River gorge. It is also the first cable-stayed bridge to be erected using a cable crane, and its concrete-box-girder side spans feature the first use of cable anchorages in the middle of the outer web. Furthermore, geometry alignment during deck closure was achieved by adjusting cable forces rather than by using counterweights. This paper describes the configuration and numerical analysis of the innovative cable anchorage, discusses the challenges and solutions involved in using a cable crane for construction and details the novel closure techniques adopted for the steel-truss deck.

Opposed-Piston Crankshaft System Dynamics Simulation and Durability Analysis in a Neotype Two-Stroke Diesel Engine

For the opposed-piston and opposed-cylinder (OPOC) diesel engine with higher power density, recently it has drawn even more attentions than ever in several developed countries, such USA and Germany, et al, which is regarded as a technical innovation to further reduce emission, and decrease fuel consumption, attributed to outstanding thermal efficiency and engine package downsizing. To explore the interrelation of this special crank system in concept design stage, the multi-body dynamics and durability of the piston-opposed crankshaft system was investigated. Firstly the optimized function model of the unique crankshaft system in an OP2S (Opposed-piston two stroke) engine was established. Then it was to figure out the influence of all structural design parameters on OPE crankshaft averaged output torque, respectively. The calculated results show that the initial crank angle difference between inner crank web and outer crank web was the most critical contributor to elevate the averaged torque output than other structural parameters. The parametric 3D model of crankshaft system was refreshed automatically based on the optimized variables. Finally an OPE crankshaft prototype was manufactured and bend fatigue experiment was carried out in a relevant laboratory to obtain the material S-N Curve. The HCF (High Cycle Fatigue) result was indicated that the minimum safety factor on crank journal fillets can reach relevant estimation criterion without crankshaft failure occurring for an engine speed sweep.

Redstart Bird (Passeriformes, Muscicapidae) with Non-Typical Plumage — Interspecific Hybrid or Eastern Subspecies in Fauna of Ukraine

Abstract A redstart male in plumage resembling that of the Common Redstart, Phoenicurus phoenicurus (Linnaeus, 1758), but with black throat extending downwards the central part of the breast was recorded in Dnipro City (Central Prydniprovia, i. e. Central Ukraine) in April, 2014. Song, calls and behavior of the male were typical of the Black Redstart, Phoenicurus ochruros (Gmelin 1774). The male was breeding with the Black Redstart female and successfully reared two nestlings. Both adults were captured and examined. The male with unusual colors of plumage exhibited strong resemblance to phenotype of males from the subspecies phoenicuroides of Black Redstart. Examination of specimens belonging to the subspecies in collection of Zoological Museum (NMHH of NAS of Ukraine) revealed that according to wingtip formula, the non-typical male is also similar to those of that race, in particular ones from Tyva (situated on border between the Upper Yenisei region and Mongolia). However, some plumage characters (signs of white color on emargination of outer web on some tertials and secondaries as trait of the subspecies gibraltariensis of the Black Redstart, as well as whitish belly and paler rufous color on lower breast and underparts as peculiarities of the Common Redstart) seem to indicate hybrid origin of the recorded male. The redstart male exhibiting both traits of the Common Redstart and Black Redstart was found for the first time in all period of expansion of gibraltariensis subspecies from west border of Ukraine eastwards and southwards.

Wing morphology and plumage characteristics of the eastern form of Eurasian Reed Warbler Acrocephalus scirpaceus fuscus in Cyprus

The breeding distribution of Eurasian Reed Warblers Acrocephalus scirpaceus in the Western Palearctic is highly fragmented and their taxonomy is complex. Eastern Mediterranean populations lie between the ranges of the nominate scirpaceus and the eastern race fuscus. The aim of this study was to use biometrics and plumage criteria to elucidate the racial affinities of Reed Warblers breeding at a site in Cyprus. The population appears to belong to fuscus, but has notably short and rounded wings. Either true emargination or a narrowing of the outer web of the fourth primary was observed in adults. The results are discussed in relation to the wing lengths of passage Reed Warblers in Cyprus.

Clinal pattern of morphological variation in Sakesphorus luctuosus (Lichtenstein, 1823), with comments on the enigmatic Sakesphorus hagmanni Miranda-Ribeiro, 1927 (Passeriformes: Thamnophilidae)

Sakesphorus luctuosus (Glossy Antshrike) is endemic to Brazil, harboring two subspecies. The nominal subspecies is widespread in the Amazon region, and S. l. araguayae is endemic to the Rio Araguaia valley. In this paper we investigated the hypothesis that S. l. araguayae represents the end of a cline. We examined 588 specimens housed in Brazilian, North American and European museums and based our conclusions on plumage coloration and morphometric characters. We found no significant differences in morphometric characters between subspecies, except for culmen length, which was slightly shorter in S. l. araguayae, but with wide overlap in measurements. The main proposed diagnostic character between subspecies (length of the white tips to tail feathers) showed clinal variation, with northern birds showing more white on the tail, and southern birds showing less white on the tail, irrespective of hydrographic basin. The other diagnostic character proposed (width of the white edges to the outer webs of the scapular feathers) showed high individual variation and no taxonomic consistency. We conclude that S. l. araguayae is a junior synonym of the nominal taxon. On the other hand, S. hagmanni, known only from the holotype and long thought to be a junior synonym of the nominal taxon, proved to be a unique specimen that should be considered as species inquirenda until further investigations determine its status.

Workplace Field Testing of the Pressure Drop of Particulate Respirators Using Welding Fumes

In a previous study, we concluded that respirator testing with a sodium chloride aerosol gave a conservative estimate of filter penetration for welding fume aerosols. A rapid increase in the pressure drop (PD) of some respirators was observed as fumes accumulated on the filters. The present study evaluated particulate respirator PD based on workplace field tests. A field PD tester was designed and validated using the TSI 8130 Automatic Filter Tester, designed in compliance with National Institute for Occupational and Safety and Health regulation 42 CFR part 84. Three models (two replaceable dual-type filters and one replaceable single-type filter) were evaluated against CO(2) gas arc welding on mild steel in confined booths in the workplace. Field tests were performed under four airborne concentrations (27.5, 15.4, 7.9, and 2.1 mg m(-3)). The mass concentration was measured by the gravimetric method, and number concentration was monitored using P-Trak (Model 8525, TSI, USA). Additionally, photos and scanning electron microscopy-energy dispersive X-ray spectroscopy were used to visualize and analyze the composition of welding fumes trapped in the filters. The field PD tester showed no significant difference compared with the TSI tester. There was no significant difference in the initial PD between laboratory and field results. The PD increased as a function of fume load on the respirator filters for all tested models. The increasing PD trend differed by models, and PD increased rapidly at high concentrations because greater amount of fumes accumulated on the filters in a given time. The increase in PD as a function of fume load on the filters showed a similar pattern as fume load varied for a particular model, but different patterns were observed for different models. Images and elemental analyses of fumes trapped on the respirator filters showed that most welding fumes were trapped within the first layer, outer web cover, and second layer, in order, while no fumes were observed beneath the fourth layer of the tested respirators. The current findings contribute substantially to our understanding of respirator PD in the presence of welding fumes.

Experimental Evidence for the Amelioration of Shadow Competition in an Orb‐Web Spider Through the ‘Ricochet’ Effect

AbstractStationary predators such as spiders can face competition from conspecifics simply by virtue of the spatial positioning of their webs. Shadow competition, wherein a predator ‘upstream’ restricts access to prey for another individual further ‘downstream’, can affect the foraging success of stationary predators. However, in spiders that build orb‐webs in proximity to each other, insect prey often ‘ricochet’ off the outer web and land on the inner web. In this study, I asked whether the negative effect of shadow competition could be compensated for by the ricochet effect. I experimentally show that despite a strong spatial advantage to a spider on the outer side in terms of prey interceptions, the likelihood of prey intercepting the inner web is increased through the ricochet effect. I also show that the degree of overlap between the webs significantly influences both the number of prey intercepted as well as the number of ricochets. This study shows experimentally that a spider that builds its web close to a conspecific’s web suffers very little cost in terms of lost prey interception.

Thinking about Feathers: Adaptations of Golden Eagle Rectrices

“Happy is the man whose lot it is to know The secrets of the earth.” EuripidesThe striking black and white plumage of the juvenile Golden Eagle (Aquila chrysaetos) provides an excellent opportunity to examine the possible selective forces influencing the strategic placement of dark pigment in birds. The conflict between opposing selective pressures (first, toward large white patches, which may allay aggression in adults, and second, toward dark plumage to promote camouflage and limit solar and abrasive wear) provides the stage whereon are revealed a score of pigmentation traits of potential adaptive value.The general pigmentation trend is for zones that are more exposed to the sun to be darker than elsewhere. More specifically: (1) for rectrices and remiges, outer webs are darker than inner; (2) for those few feathers (e.g., central rectrices, some scapulars, and some tertials), where both inner and outer webs are heavily and nearly equally solar exposed, pigmentation is supplied similarly on both webs; (3) outermost primaries and rectrices are darkest of all and are structurally similar; (4) for central rectrices, subject to high levels of abrasion with substrate, the tip is paler (resultant flexibility may limit breakage); and (5) pigment is heavier along or on the rachis than on the webs.Many of the traits listed above for the Golden Eagle are also found in other families of birds. Traits of the tail common to many species were a terminal pale tip, a subterminal dark band, rachis darker than vane, and outer webs darker than inner for both remiges and rectrices. The most widespread traits likely have adaptive value.