Bar Thickness Research Articles

Bond Behaviors between Ribbed BFRP Bars and Ecological High Ductility Cementitious Composites

Direct pull-out method was conducted to explore the bond stress-slip response of ribbed basalt fiber reinforced polymer (BFRP) bars embedded in ecological high ductility cementitious composites (Eco-HDCCs). The effects of the embedment length and cover thickness on the bond properties between Eco-HDCCs and the bars were described. Results indicate that the failure characteristics of the specimens depend on the embedment length and cover thickness of the BFRP bars. As the embedment lengths of the bars increase, the ultimate bond stress decreases while the ultimate slip increases. Besides, both the ultimate bond stress and ultimate slip show an increasing trend if the specimen has a cover thickness of less than 45 mm, while the increasing trend is slower if the specimen has a cover thickness of more than 45 mm. In addition, the strain of the specimen surface depends on the cover thickness, and the strain increases when the cover thickness is in a range of15 mm–35 mm. Moreover, certain embedment lengths and cover thicknesses of the BFRP bars are recommended in the structural design of bridge deck link slabs. The bond stress-slip relationship models of the BFRP bars in Eco-HDCCs are proposed based on the test results.

Effect of MS Rings’ Confinement on Lateral Deformations of M 25 Grade Circular RCC Columns under Axial Compression Loads

Confinement has been always a key concern area for researchers in present and in past also. The metal confinement of RCC columns has been extensively used from long time like concrete-filled steel tube (CFST) columns etc. In the present work mild steel rings have been used as confining material. In this paper based on experimental work, it is aimed to improve the axial compression strength and lateral deformation characteristics of circular RCC columns confined by mild steel (MS) rings. Total 45 nos. of specimen of size 150 mm dia. and 300 mm height were prepared during the experimental work. These specimen were tested and results were analyzed.These MS rings confined circular RCC columns of M 25 grade concrete were experimentally studied for different variables like (i) % of column main vertical steel bars (ii) thickness of MS rings (iii) spacing of MS rings. It was found that the MS ring confinement effectively helped in reducing lateral deformation of circular RCC column specimen resulting in improved axial compressive load capacity of circular RCC columns also. As MS rings are made up of conventional material i.e. mild steel pipes, the technique has a vast application area. In rural part of India this technique can be conviniently used for the efficient confinement of RCC columns.

Analysis of a Lightweight Aluminum Vehicle Chassis in a Simulation-Based Design Approach

This study investigates different chassis designs through a simulation-based design approach. The inherent aluminum ductility and softness could make chassis a daunting modification if not analyzed properly. Structural finite element analysis is comprehensively performed on a vehicle chassis for static loading cases up to 1G in equivalent acceleration. The analysis of the vehicle chassis of both A36 steel and 6061 aluminum for the scenarios of bump, front impact, side impact and a rollover. The von Mises stresses and displacement results showed that the steel chassis possessed higher safety factor in all load cases. The safety factors for an aluminum clone of the steel chassis in some load cases are below 1.0, hence indicating that the failure criterion has been triggered and failure would occur under the 1G load. The original aluminum chassis deformation is far more severe than steel reaching as high as 9.88 mm for the bump loading. A modified aluminum chassis is proposed, by optimizing the wall thickness of the rectangular bars. The slight increase in weight resulted in overcoming the deficiency of aluminum in load carrying capacity. An evaluation matrix procedure is implemented to analyze the trade offs between cost, weight and safety factor for the three chassis materials.

Genesis of giant, bouldery bars in a Miocene gravel-bed river: Insights from outcrop sedimentology, UAS-SfM photogrammetry, and GPR

ABSTRACTBedsets of bouldery intraformational conglomerate partly fill a narrow, 40-m-deep paleovalley in the Arikaree Group (lower Miocene) in Nebraska, USA. Entire bar successions are exposed in 3D, offering an opportunity to improve upon sedimentological models for coarse-grained fluvial deposits. Using unmanned aircraft, structure-from-motion photogrammetry, and ground-penetrating radar, we offer the first comprehensive assessment of the lithofacies and stratigraphic architecture of this regionally unique fluvial conglomerate. We interpret three lithofacies associations: (1) beds of chaotic breccias lining the exhumed valley wall (colluvium), (2) < 5-m-thick units dominated by horizontal to gently inclined (2–3°) beds of granule to pebble conglomerates, and (3) 10–24-m-thick units of steeply inclined (∼ 30°) beds of bouldery conglomerates, which dominate the channel fill. The deposit comprises at least four stories, but its thickest part is a deep scour filled by a single story of steeply inclined bouldery deposits. The direction of accretion of the giant bars was toward the paleovalley wall, where contemporaneous valley-side colluvium and bar deposits are juxtaposed. We propose that increased discharge in a high-order trunk stream rapidly eroded the friable sandstone of the underlying Monroe Creek–Harrison formations, amassing resistant, large concretions that were subject to valley-slope mass movements and fluvial transport (subaqueous traction, grainflow, and debris flow). Giant accretion surfaces formed as fluvial bars migrated over the edges of deep scours. Thus, the funneling of increased discharges through a confined paleovalley amplified the magnitudes of valley and bed erosion, water depth, stream competence, and bar thickness, preserving an exceptionally thick, coarse-grained deposit.

Increase in Coating Thickness of Epoxy-Coated Steel Reinforcing Bars for Concrete Deck Replacement

Increase in Coating Thickness of Epoxy-Coated Steel Reinforcing Bars for Concrete Deck Replacement

Comprehensive measurement techniques and multi-index correlative evaluation approach for structural health monitoring of highway bridges

The bridge is damaged under the long-term traffic load, climate and geological conditions, which may lead to serious traffic interruption and economic loss. This study presents an integrated measurement technique in conjunction with a multi-index correlative evaluation approach for structural condition assessment of bridges. Using a typical highway bridge in China as a case study, the concrete strength, thickness of bridge deck pavement, thickness of the bottom plate of the hollow plate, crack development, cover thickness of steel bars etc. were systematically monitored. Most importantly, a series of static load tests were conducted and the results were analysed using a developed multi-index correlative evaluation model to assess the current structural capacity of the bridge. The results show that comprehensive measurements and the multi-index correlative evaluation approach provide an effective means for structural health monitoring of bridges, and can provide theoretical basis for the highway bridge monitoring under similar complicated environmental conditions.

3-d topology optimization of modulated and oriented periodic microstructures by the homogenization method

This paper is motivated by the optimization of so-called lattice materials which are becoming increasingly popular in the context of additive manufacturing. Generalizing our previous work in 2-d we propose a method for topology optimization of structures made of periodically perforated material, where the microscopic periodic cell can be macroscopically modulated and oriented. This method is made of three steps. The first step amounts to compute the homogenized properties of an adequately chosen parametrized microstructure (here, a cubic lattice with varying bar thicknesses). The second step optimizes the homogenized formulation of the problem, which is a classical problem of parametric optimization. The third, and most delicate, step projects the optimal oriented microstructure at a desired length scale. Compared to the 2-d case where rotations are parametrized by a single angle, to which a conformality constraint can be applied, the 3-d case is more involved and requires new ingredients. In particular, the full rotation matrix is regularized (instead of just one angle in 2-d) and the projection map which deforms the square periodic lattice is computed component by component. Several numerical examples are presented for compliance minimization in 3-d.

Robust Optimization Design of Metro Handrails

This paper presents the robust design and response surface method (RSM) based on finite element analysis for the optimization design of metro handrails. The response surface can be created for each output parameter. Sequential quadratic programming is used for the optimization of metro handrails. Taguchi design is employed to investigate the sensitive controlling factors for the strength and mass of metro handrails, by taking the material density, the column and cross bar thickness as controlling factors, and the acceleration, the elastic modulus and the fluctuation of material density as uncontrollable factors. Then, the best combination of controlling factors is found. The results by different methods show that the method of Taguchi design can improve the robustness of the structural performance and reduce the mass.

Numerical simulation and experimental research on the comprehensive performance of the shell side of the spiral wound heat exchanger

In this paper, the spiral wound heat exchanger (SWHE) partial geometric models with different tube diameters (6 mm < d0 < 14 mm), tube pitches(2 mm < Z < 14 mm) and spacing bar thickness (2 mm < S2 < 4.5 mm), were established. Numerical simulation and performance comparison were carried out using water as the heat transfer fluid. The numerical results showed that the heat transfer performance of the shell side was optimized when the tube diameter, the tube pitch, and the spacing bar thickness was 6, 14, and 3.5 mm, respectively. Moreover, the experimental research on the heat transfer of Y-type and K-type SWHEs was conducted on the water vapor at a constant volume flow rate in the tube side and the liquid water at volume flow rates in the range of 1.5–7 m3/h in the shell side.. The experimental data showed that the heat transfer coefficient of Y-type SWHE was 3.4–17.9% higher than K-type SWHE under the same condition. The pressure drop of Y-type SWHE is 9.8–61% lower than K-type SWHE. The ratio of performance evaluation factors (PEC) of the Y-type to K-type SWHE is was greater than 1, so the heat transfer performance of Y-type was better than K-type SWHE. Additionally, the comparisons between experimental data and the numerical results show that the relative errors are in the acceptable range. Therefore, the numerical results are correct and trustable.

Mini-ants manage vision miniaturisation

Miniaturisation doesn't seem to be a problem for Ant-Man when he climbs into his suit and shrinks, but the mini-superhero could face challenges he hadn't bargained for. For example, water and air become super sticky at microscopic scales and tiny creatures lose heat faster than bulkier bodies. But what effect does being small have on vision and the way that mini-beasts see the world? Does shrinking the eye affect how much detail an animal can see and how well objects stand out from the background? Intrigued by the question, Ajay Narendra from Macquarie University, Australia, turned to Ant-Man's namesakes. ‘Quantifying this in ants was really a no-brainer’, he chuckles, pointing out that ants rely heavily on vision and they vary enormously in size. But, most importantly, there were hordes of different species right on Narendra's doorstep.Choosing to investigate the vision of ants ranging in size from massive bull ants (Myrmecia tarsata) to medium-sized jack jumpers (Myrmecia nigrocincta), and tiny spiny ants (Polyrhachis nr aurea) and Rhytidoponera inornata, Ravindra Palavalli-Nettimi and Yuri Ogawa braved the insects’ vicious stings, bringing a handful back to the lab. Cautiously painting clear nail varnish over the insects’ eyes, Palavalli-Nettimi and Ogawa produced almost perfect minute casts of the structures to measure the lens size and number. Not surprisingly, the eyes of the biggest bull ants had the largest (∼22 μm wide) – and highest number of (∼2627) – lenses, while the middle-sized jack jumpers squeezed a similar number (∼2483) of smaller lenses into their eyes. Meanwhile, both of the smaller ant species had far fewer lenses, with the eyes of the tiny R. inornata containing only ∼227 minute lenses, averaging 12.75 μm across. But how well could the ants see in practice?Knowing that Laura Ryan and Nathan Hart had recently developed a technique that allowed them to assess how clearly sharks see – by measuring minute voltage changes in the eye – Palavalli-Nettimi and Ogawa adapted the method to record how well the ants could see flickering black and white bars as the duo varied the bar thickness and how well they stood out from the background. ‘The most challenging task was to obtain a good signal-to-noise ratio in the smallest ant’, says Palavalli-Nettimi, who resorted to shielding the delicate ant eyes from stray electric and magnetic fields with a Faraday cage so he could record the weak voltages.Amazingly, when the team eventually compared the ants’ eyesight, the minute R. inornata could see almost as clearly as the heftiest M. tarsata bull ants. ‘The smallest ants had only 8% of the facets [lenses] of the largest ants, but had 80% of their spatial resolution’, says Narendra. And, when the team compared how well objects stand out for the differently sized insects, the heavyweight bull ants had the upper hand, able to pick out faint objects that were only 6.4% brighter than their background, in contrast to the diminutive R. inornata ants, which could only distinguish objects that were 74.1% brighter. ‘This shows that smaller ants place more emphasis on spatial resolving power than contrast sensitivity’, says Narendra. However, when the team compared how long the insects’ eyes took to respond when a light flicked on, the smaller ants response time was ∼260 ms, in contrast the bull ants’ speedy ∼106 ms, ‘which may allow them [R. inornata] to improve their contrast sensitivity’, says Narendra.So, the eyesight of mini-ants is poorer than that of their outsized cousins, but not as weak as their size difference might suggest, and Narendra is keen to see how other insect species deal with the challenge of miniaturisation.

Analogue of Electromagnetically Induced Transparency in an S-Shaped All-Dielectric Metasurface

We proposed and numerically investigated an analogue of electromagnetically induced transparency (EIT) all-dielectric metasurface that features one asymmetric S -shaped silicon resonator in the unit cell and generates high transparency, high Q -factor resonance in the near infrared spectral region. Breaking the symmetry of the S -shaped structure could provide a pathway to excite a trapped magnetic mode that coupled to a bright electric dipolar moment, achieving a sharp EIT-like response. And the Q value of the resonance can be easily modified by altering the asymmetric degree of the structure. In particular, the transparency window will almost maintain its symmetric shape and high transmission of 97%, but shift accordingly as the structural parameters (silicon bar's length, width, or thickness) vary in a large range, because of the very small detuning between the two coupled modes. The proposed S -shaped all-dielectric metasurface could ease fabrication challenges and have potential applications in biochemical sensing, narrowband filters, optical modulations, and slow light devices.

Применение метода сечений для определения коэффициента интенсивности напряжений по фронту полуэллиптической поперечной краевой трещины в растянутой полосе

The article presents the developed method of analytic determination of the stress intensity factor distribution along the front of a semi-elliptical edge transverse crack in a flat bar stretched by constant stresses. The calculation is based on the method of sections. According to the method, the equilibrium equation for the normal force is written, which comes to the equality of the normal forces at the free end of the bar and in the plane of the crack. We show that between the values of the stress intensity factor at the deepest point and at the point coming to the surface, one can introduce a rigid constraint depending on the ratio of the crack depth to its half-length and the ratio of the crack depth to the bar thickness. The introduction of this connection allowed to use only one equilibrium equation in the calculation. To test the obtained data for a bar of infinite width, we compared this data and the results of calculating the stress intensity factor from the approximation formulae available in the reference literature. The possibility of using the developed methodology for a flat bar of finite width is justified by comparing the results of calculation by the proposed method with numerical values obtained in the process of solving the problem by the finite element method in the ANSYS software environment

D.C conductivity of In2O3: SnO2 thin films and manufacturing of gas sensor

Compounds were prepared from In2O3 doped SnO2 with different doping ratio by mixing and sintering at 1000oC. Pulsed Laser Deposition PLD was used to deposit thin films of different doping ratio In2O3: SnO2 (0, 1, 3, 5, 7 and 9 % wt.) on glass and p-type wafer Si(111) substrates at ambient temperature under vacuum of 10-3 bar thickness of ~100nm. X-ray diffraction and atomic force microscopy were used to examine the structural type, grain size and morphology of the prepared thin films. The results show the structures of thin films was also polycrystalline, and the predominate peaks are identical with standard cards ITO. On the other side the prepared thin films declared a reduction of degree of crystallinity with the increase of doping ratio. Atomic Force Microscopy (AFM) measurements show the average grain size exhibit to change in non-systematic manner with the increase of doping ratio with tin oxide. The average grain size increases at doping ratios 1, 5 and 7 % from 52.48 to 79.12, 87.57, and 105.59 nm respectively and decreases at residual doping ratio. The average surface roughness increases from 0.458 to 26.8 nm with the increase of doping ratio. The gas sensing measurements of In2O3:SnO2 thin films prepared on p-Si to NO2 gas showed good sensitivity and Maximum sensitivity (50) obtained for In2O3:SnO2 prepared on p-Si at operating temperature 573 K and doping ratio 7 % and 9 %. Maximum speed of response time (8 sec) at operating temperature 573 K and doping ratio 1 %.

Estimation of Residual Stress in Selective Laser Melting of a Zr-Based Amorphous Alloy.

An accurate estimation of residual stresses is crucial to ensure dimensional accuracy and prevent premature fatigue failure of 3D printed components. Different from their crystalline counterparts, the effect of residual stress would be worse for amorphous alloys owing to their intrinsic brittleness with low fracture toughness. However, the generation of residual stress and its performance in 3D printed amorphous alloy components still remain unclear. Here, a finite element method combined with experiments and theoretical analyses was introduced to estimate the residual stress in selective laser melting of a Zr-based amorphous alloy. The results revealed that XY cross scanning strategy exhibits relatively low residual stress by comparison with X and Y strategies, and the residual stress becomes serious with increasing bar thickness. The residual stress, on the other hand, could be tuning by annealing or preheating the substrate. The above scenario is thoroughly understood according to the temperature gradient mechanism and its effect on microstructure evaluation.

What is a normal pharynx? A videofluoroscopic study of anatomy in older adults.

Structural and functional pharyngeal changes occur with age. How these affect swallowing in healthy older adults is not well defined. This study presents quantitative pharyngeal anatomic features in healthy adults using videofluoroscopic study of swallowing (VFSS). This will help our understanding of the normal changes in swallowing that occur with age and illustrate what may constitute normal variation compared with abnormal swallow function. 138 mixed gender adults with no history of dysphagia were recruited and underwent a standardized VFSS protocol. Parameters including age, BMI, and gender were correlated with the presence of a cricopharyngeal bar, spinal changes and pharyngeal wall thickness at rest. 46% of participants had notable spinal changes. 8% of participants demonstrated cricopharyngeal bars and 12% of subjects revealed osteophytes. Age positively correlated with the presence of a cricopharyngeal bar (rs = 0.281, p < 0.001) and presence of osteophytes (rs = 0.334, p < 0.001). The incidence of cricopharyngeal bars in adults over 70years old was 16%. A significant number of healthy adults with no swallowing complaints have variant pharyngeal anatomic findings such as cervical vertebral osteophytes and cricopharyngeal bars. This must be taken into account when assessing patients with dysphagia complaints to avoid misattribution of symptoms to these potentially asymptomatic variants. This ensures correct recommendations are made regarding management including diet modification, compensatory strategies, and surgical intervention.

A method to determine the depowdered height in lattices manufactured by electron beam melting

After completing a part in electron beam melting (EBM), a depowdering operation is required to separate the sintered but unmelted powder from the manufactured part. Depowdering lattice structures can be difficult or even impossible due to their intrinsic shape. The aim of this paper is to propose a criterion to ensure that a lattice structure manufactured by EBM can be depowdered. The objective is to use this criterion during the design phase of lattice structures to make them manufacturable and depowderable. Experiments are conducted on depowdering octet-truss lattice structures with variable bars thickness and mesh sizes. Different criteria are introduced, among them the criterion “hydraulic diameter” of a lattice structure, inspired by the Darcy–Weisbach hydraulic law used to calculate the pressure drop in a pipe. This criterion can be determined using only geometrical characteristics of lattices available in the CAD model of the part. Results show that the levels of depowdering for lattice structures are proportional to this hydraulic diameter. As a validation, a bike stem has been manufactured following the criterion and has demonstrated its efficiency.

The role of Tin Oxide Concentration on The X-ray Diffraction, Morphology and Optical Properties of In2O3:SnO2 Thin Films

Alloys were performed from In2O3 doped SnO2 with different doping ratio by quenching from the melt technique. Pulsed Laser Deposition PLD was used to deposit thin films of different doping ratio In2O3 : SnO2 (0, 1, 3, 5, 7 and 9 % wt.) on glass substrate at ambient temperature under vacuum of 10-3 bar thickness of ∼100nm. The structural type,grain size and morphology of the prepared alloys compounds and thin films were examined using X-ray diffraction and atomic force microscopy. The results showed that all alloys have polycrystalline structures and the peaks belonged to the preferred plane for crystal growth were identical with the ITO (Indium – Tin –Oxide) standard cards also another peaks were observed belonged to SnO2 phase. The structures of thin films was also polycrystalline, and the predominate peaks are identical with standard cards ITO. On the other side the prepared thin films declared decrease a reduction of degree of crystallinity with the increase of doping ratio. Atomic Force Microscopy AFM measurements showed the average grain size and average surface roughness exhibit to change in systematic manner with the increase of doping ratio with tin oxide. The optical measurements show that the In2O3:SnO2 thin films have a direct energy gap Egopt in the first stage decreases with the increase of doping ratio and then get to increase with further increase of doping ration, whereas reverse to that the optical constants such as refractive index (n), extinction coefficient (k) and dielectric constant (εr, εi) have a regular increase with the doping ratio by tin oxide and then decreases.

A quantitative model of paleowind reconstruction using subsurface lacustrine longshore bar deposits – An attempt

The paleo-atmospheric flow field is an important component of climate. However, the difficulty of constraining paleowind fields using geological information hinders quantification of paleo-atmospheric conditions. In this paper, it is proposed that the geometric characteristics of lacustrine longshore bars, widespread in both modern and ancient shallow lakes, can be used as proxies for paleowind fields. The self-organizational model of longshore bar formation indicates that bar geometry and dimensions are determined by breaking waves. Accordingly, a simple geometric model is proposed that incorporates empirical constraints, including: 1) the ratio of paleowater depths between bar crest and adjacent landward trough is constant, and 2) the bar landward slope reaches the angle of repose. The model suggests that the parameters longshore bar thickness (t), topographic slope of the bar-basement (α) and paleo-fetch of the basin (F) are sufficient to constrain paleowave conditions, and hence, based on wave statistics and wind-wave relationships, paleowind conditions. The method is then applied to an ancient example, the Dongying Depression in East China, to determine wind direction and strength during part of the Eocene (~45.0–44.2 Ma). The results show that contemporaneous northerly and southeasterly winds existed, with highest wind speeds of 6.9–13.5 m s−1 and 7.5–18.2 m s−1, respectively. These findings provide a new perspective on delineating paleowind conditions. Error analyses reveal that for a sufficiently large lake (fetch exceeding 30 km), calculation errors will be small to negligible, if longshore bar thickness is determined as precisely as possible. The method is applicable only for bars whose formation conforms to the self-organizational model.

Variable Thermal-Force Bending of a Three-Layer Bar with a Compressible Filler

Deformation of a three-layer elastoplastic bar with a compressible filler in a temperature field is considered. To describe the kinematics of a pack asymmetric across its thickness, the hypothesis of broken line is accepted, according to which the Bernoulli hypothesis is true in thin bearing layers, and the Timoshenko hypothesis is valid for a filler compressible across the its thickness, with a linear approximation of displacements across the layer thickness. The work of filler in the tangential direction is taken into account. The physical stress-strain relations correspond to the theory of small elastoplastic deformations. Temperature variations are calculated from a formula obtained by averaging the thermophysical properties of layer materials across the bar thickness. Using the variational method, a system of differential equilibrium equations is derived. On the boundary, the kinematic conditions of simply supported ends of the bar are assumed. The solution of the boundary problem is reduced to the search for four functions, namely, deflections and longitudinal displacements of median surfaces of the bearing layers. An analytical solution is derived by the method of elastic solutions with the use of the Moskvitin theorem on variable loadings. Its numerical analysis is performed for the cases of continuous and local loads.

The Vibrations Study of DAMMAR Based Composite Bars Reinforced with Natural Fibers by Using a New Euler - Bernoulli Theory

In the paper it is presented a new Euler - Bernoulli theory based on an assymetrical distribution of strains towards the median plane, the area subjected to compression has a transversal stretching, while the area subjected to tensile has a transversal contraction. This theory takes into account the transversal contraction factors and consequently the eigenpulsations of bars vibrations with rectangular section depend on the ratio between the bars width and thickness. This theory is experimentally verified for Dammar based composite bars reinforced with cotton, flax, silk and hemp fibers. For the considered bars, we have experimentally determined the eigen frequencies and the damping factor values.