Effect Of Geometrical Characteristics Research Articles

A comparative analysis of the performance of turbo roundabouts based on geometric characteristics and traffic scenarios

ABSTRACT This study aimed to investigate the effect of geometric characteristics and traffic scenarios on the performance measures, including delay, volume to capacity (v/c) ratio, capacity, and the level of service (LOS) in basic and rotor turbo roundabouts. In addition, it attempted to compare turbo roundabouts using performance measures based on geometric characteristics and traffic scenarios. The results showed that performance measures reduced significantly by increasing the diameter of four-leg turbo roundabouts although they improved in three-leg turbo roundabouts. Further, four- and three-leg basic turbo roundabouts had a better performance by changing the balanced to imbalanced traffic flow scenario compared with four- and three-leg rotor turbo roundabouts. Additionally, substituting four- and three-leg basic turbo roundabouts for rotor four- and three-leg turbo roundabouts increased the performance measures. Overall, the basic turbo roundabouts had a better performance compared to the rotor turbo roundabout under unsaturated and saturated traffic conditions .

Electrically-assisted mechanical clinching of AA6061-T6 aluminum to galvanized DP590 steel: effect of geometrical features on material flow and mechanical strength

The mechanical clinching as an alternative joining process for fabricating lightweight aluminum to steel assemblies may face the challenges when joining low-ductility aluminum alloy to high-strength steel. Several researches have been focused on applying the electrically-assisted processes in various fields due to energy efficiency as well as practical simplicity, in order to improve the formability. This paper concentrates on the electrically-assisted mechanical clinching (EAMC) of AA6061-T6 aluminum to galvanized DP590 steel. To this end, a combination of experimental and numerical clinching tests was performed using extensible die at different penetration depths, in which controlling the material flow was obtained by applying newly defined chamfer ratioRCin order to guarantee the strong mechanical interlock. The joint section parameters, failure loads, and failure modes were measured. The effects of the geometrical features on material flow and mechanical strength of clinched joints were analyzed using a FE model. The results showed that the defined parameterRCgreatly increased the strength with the use of the EAMC process, which came with a reduction in forming load.

Vibration characteristic of moderately thick graphene reinforced composite functionally graded plate based on state-space levy method combined with higher order shear deformation theory

In this paper, the mechanical properties of graphene reinforced composite functional gradient (GRC-FG) plates under plane load conditions are studied in depth. The plate consists of a segmented patterned graphene reinforcement layer and the mechanical properties of the composite are simulated by extending the Halpin-Tsai micromechanical model. The governing equations are derived from Reddy’s third-order shear deformation theory (HSDT) and the Hamiltonian principle. For the study of two opposite side simple supports and the solution of the coupled motion equation, we use state space eigenvectors to solve. The effects of geometric features and boundary conditions on material properties were investigated.

Determinants of injury severity for truck crashes on mountain expressways in China: A case-study with a partial proportional odds model

The fast economic growth in China has dramatically increased the number of heavy traffic and the length of the expressway network, with consequent road safety issues emerging in particular in mountainous expressways. This study positions itself at the intersection of these issues by analysis determinants of injury severity for truck crashes on mountainous expressways in China. A sample of 2695 heavy truck crashes occurring on four mountain expressways in Jiangxi and Shaanxi (China) between 2006 and 2015 was analysed to uncover the effect on crash injury severity of geometric, driver, crash, truck and environmental characteristics. Given that the expansion of the expressway network is underway, model findings focused on the effect of geometric characteristics and suggested that road design should have curves that are neither too sharp nor too long, as well as longitudinal gradients not too steep. Also, model findings indicated a need for the toughening of deterrence measures and the bolstering of police enforcement with respect to aberrant driver behaviour (e.g., driving without a valid license, without seat belts, or while intoxicated) and most relevantly overloading of the trucks.

High energy absorption efficiency of thin-walled conical corrugation tubes mimicking coconut tree configuration

In this study, a new tubular corrugated configuration mimicking the coconut tree profile, here named “conical corrugation tube” (CCT), was proposed, in an attempt to enhance the energy absorption, minimize the initial peak crushing force, and stabilize the crushing process. The effects of geometrical features, especially tapered angle and wavelength of CCTs on the deformation mode and energy absorption characteristics, were investigated through a series of numerical simulations. The results showed that the deformation modes of CCTs could be mainly classified into four modes, which were clearly influenced by the tapered angle and the wavelength of the CCTs. Moreover, the initial peak force of the CCTs was reduced significantly compared with that of the circular straight tube and the tapered tube. In addition, the undulation of the load-carrying capacity parameter, which is used to evaluate the stability of the crushing force, is minimized, and the CCTs produced smoother force-displacement curves compared with the circular straight tube and the tapered tube. Finally, a theoretical model was proposed to predict the mean crushing force of CCTs under dynamic impact loading. The theoretical results showed a good agreement with the numerical results.

Shear behavior of RC interior joints with beams of different depths under cyclic loading

Extensive reinforced concrete interior beam-column joints with beams of different depths have been used in large industrial buildings and tall building structures under the demand of craft or function. The seismic behavior of the joint, particularly the relationship between deformation and strength in the core region of these eccentric reinforced concrete beamcolumn joints, has rarely been investigated. This paper performed a theoretical study on the effects of geometric features on the shear strength of the reinforced concrete interior beam-column joints with beams of different depths, which was critical factor in seismic behavior. A new model was developed to analyze the relationship between the shear strength and deformation based on the Equivalent Strut Mechanism (ESM), which combined the truss model and the diagonal strut model. Additionally, this paper developed a simplified calculation method to estimate the shear strength of these type eccentric joints. The accuracy of the model was verified as the modifying analysis data fitted to the test results, which was a loading test of 6 eccentric joints conducted previously.

A study on the effects of temperature and substrate structure on the templated two-phase film growth via a hybrid model

Templated growth of two-phase thin films can achieve desirably ordered microstructures. In such cases, the microstructure of the growing films follows the topography of the template. By combining the Potts model Monte Carlo simulation and the “level set” method, an attempt was previously made to understand the physical mechanism behind the templated growth process. In the current work, this model is further used to study the effect of two parameters within the templated growth scenario, namely, the temperature and the geometric features of the template. The microstructure of the thin film grown with different lattice temperatures and domes is analyzed. It is found that within a moderate temperature range, the effect of geometric features took control of the ordering of the microstructure by its influence on the surface energy gradient. Interestingly, within this temperature range, as the temperature is increased, an ordered microstructure forms on a template without the optimal geometric features, which seems to be a result of competition between the kinetics and the thermodynamics during deposition. However, when the temperature was either above or below this temperature range, the template provided no guide to the whole deposition so that no ordered microstructure formed.

Influence of the geometry on the riser gas holdup in an external-loop airlift reactor: empirical and neural network modelling

Experimental studies on the effect of geometrical characteristics (restriction orifice free area and sparger configuration) on the riser gas holdup of an external-loop airlift reactor have been conducted in this paper. The impact of the addition of non-coalescing media, such as n-butanol, was also investigated. In general, the decrease in the restriction orifice free area led to a substantial increase (up to 90%) in the riser gas holdup. The addition of n-butanol effected gas holdup to a lesser extent, as it increased the gas holdup in the range of 4-15%, depending on the restriction orifice free area. On the other hand, the impact of the sparger type was observed only at lower gas velocities, for which the sinter plate increased the gas holdup up to 20% in comparison to the single orifice. The paper also presents an empirical correlation for the estimation of the riser gas holdup with an average relative error of 7%. Finally, a neural network model with an average relative error of 2.4% was proposed.

Effects of Cell Microtopology on the In-plane Dynamic Crushing Analysis of Re-entrant Square Cellular Material

With the development of three-dimensional printing technologies, so-called cellular materials have achieved increasing attention due to outstanding properties. Unlike pure solid structures, properties of cellular materials are influenced by both utilized material and cell microtopology. The present paper proposes a novel type of re-entrant square cellular material. To explore the relationship between microtopology and macrodynamic responses systematically, an explicit dynamic finite element simulation method is used. This work starts by constructing theoretical models of relative density employing a two-dimensional unit cell. Then, the effects of geometric features and configurations on dynamic properties are explored, and simulations indicate that variations of geometric parameters strongly affect properties and that the staggered re-entrant squares are more stable than the regular re-entrant squares. Subsequently, the effects of the impact velocity on dynamic crushing behaviors are elaborated. On this basis, the relationship of unit mass energy absorption and geometric features is obtained by employing the response surface method. Furthermore, with targets of maximum unit mass energy absorption and minimum relative density, the optimal structural parameters are achieved by using non-dominated sorting genetic algorithm. The study provides a detailed introduction to dynamic behaviors of cellular materials and guidance to design new structures with superior characteristics of energy absorption.

Effects of millimetric geometric features on dropwise condensation under different vapor conditions

In this work, we investigated the effects of millimetric surface structures on dropwise condensation heat transfer under two different environments: pure vapor and an air-vapor mixture. Our experimental results show that, although convex structures enable faster droplet growth in an air-vapor mixture, the same structures impose the opposite effect during pure vapor condensation, hindering droplet growth. We developed a model for each case to predict the heat flux distribution along the structured surface, and the model shows reasonable agreement with experimental results. This work demonstrates that the effects of geometric features on dropwise condensation are not invariable but rather dependent on the scenario of resistances to heat and mass transfer in the system. The fundamental understanding developed in this study provides useful guidelines for condensation applications including power generation, desalination, dew harvesting, and thermal management.

Aerodynamic performance improvement of a canard control missile

PurposeThis paper aims to analyze the influence of the changings in geometrical parameters on the aerodynamic performance of the control canard projectiles.Design/methodology/approachBecause of the mentioned point, the range of projectiles increment has a considerable importance, and the design algorithm of a control canard projectile was first written. Then, were studied the effects of canard geometric parameters such as aspect ratio, taper ratio and deflectable nose on lift to drag coefficient ratio, static margin based on the slender body theory and cross section flow.FindingsThe code results show that aspect ratio increment, results in an increase in lift-to-drag ratio of the missile, but increase in canard taper ratio results in increasing of lift-to-drag ratio at 1° angle of attack, while during increasing the canard taper ratio up to 0.67 at 4° angle of attack, lift to drag first reaches to maximum and then decreases. Also, static margin decreases with canard taper ratio and aspect ratio increment. The developed results for this type of missile were compared with same experimental and computational fluid dynamic (CFD) results and appreciated agreement with other results at angles of attack between 0° and 6°.Practical implicationsTo design a control canard missile, the effect of each geometric parameter of canard needs to be estimated. For this purpose, the suitable algorithm is used. In this paper, the effects of canard geometric parameters, such as aspect ratio, taper ratio and deflectable nose on lift-to-drag coefficient ratio and static margin, were studied with help of the slender body theory and cross-section flow.Originality/valueThe contribution of this paper is to predict the aerodynamic characteristics for the control canard missile. In this study, the effect of the design parameter on aerodynamic characteristics can be estimated, and the effect of geometrical characteristics has been analyzed with a suitable algorithm. Also, the best lift-to-drag coefficient for the NASA Tandem Control Missile at Mach 1.75 was selected at various angles of attack. The developed results for this type of missile were compared with same experimental and CFD results.

Design and analysis of a sliding vane pump for waste heat to power conversion systems using organic fluids

The current research work assesses the relevance of pumping work in energy recovery systems based on bottoming Organic Rankine Cycles (ORC) and presents the development of a sliding vane pump prototype for small scale units. The novel device was installed on an ORC-based power unit for waste heat to power conversion in compressed air applications in which the heat source was a compressor lubricant while the heat sink was tap water. Tests were performed with R236fa as working fluid at different pressure rises (3.9–9.7) and revolution speeds (500–1300RPM). The experimental dataset was used to validate a numerical one-dimensional CFD model of the sliding vane pump developed in the GT-SUITE™ environment. The model takes into account the fluid dynamics and friction phenomena that are involved in the pump operation such as vane filling and emptying, leakages as well as dry and viscous friction between components in relative motion. The modeling platform was further exploited to retrieve performance maps of the pump, angular vane pressure evolution as well as to break down leakage and friction losses. The effects of geometrical features on the pump performance were eventually investigated through variations of the aspect ratio. With reference to the best experimental operating point (pressure rise 9.7, revolution speed 1250RPM), simulations showed that, with a stator 5% bigger than the nominal one and an axial length almost halved, overall pump efficiency could be increased from the experimental 36.9% to a value of 48.0%

Effects of Geometrical Features on the Seismic Response of Historical Masonry Towers

ABSTRACTHistorical masonry structures are often located in earthquake-prone regions and the majority of them are considered to be seismically vulnerable and unsafe. Historical masonry towers are slender structures that exhibit unique architectural features and may present many inadequacies in terms of seismic performance. The seismic protection of such typologies of structures and the design of effective retrofitting interventions require a deep understanding of their behavior under horizontal loads. This paper presents the results of the seismic performance evaluation of historical masonry towers located in Northern Italy. A large set of case studies is considered, comprising a significant number of towers with high slenderness and marked inclination. First, a preliminary assessment of the dynamic behavior of the different towers is carried out through eigenfrequency analyses. Then, non-linear dynamic simulations are performed using a real accelerogram with different peak ground accelerations. A damage plasticity material model, exhibiting softening in both tension and compression, is adopted for masonry. The huge amount of results obtained from the non-linear dynamic simulations allows a comparative analysis of the towers to be performed in order to assess their seismic vulnerability and to show the dependence of their structural behavior on some geometrical characteristics, such as slenderness, inclination, and presence of openings and belfry. The evaluation of different response parameters and the examination of tensile damage distributions show the high vulnerability of historical masonry towers under horizontal loads, mainly in the presence of marked inclination and high slenderness. Some general trends of the seismic behavior of the towers are deduced as a function of the main typological features.

MECHANICAL CHARACTERIZATION OF NOTCHED HOT ROLLED MULTI-PHASE STEEL

This paper presents a series of experimental and numerical studies on Hot Rolled Stretch Flanging steels. This study focuses on four prototyped Hot-Rolled Stretch Flanging steels (HR780SF). Circular- notched sheet steel samples are used to induce different stress triaxiality levels in the rolling direction of sheet materials. Digital image correlation technique measures the local true strain during the deformation process of the notched samples in uniaxial tensile test. The microstructure of the notched samples is examined to evaluate the effect of geometrical features of circular notches on the microstructural evolution during the plastic deformation. Finally, the numerical results obtained via a finite element simulation are validated by the collected experimental data. Our experimental studies reveal the possibility of crack formation along the width of HR780SF steels during the mechanical load. The crack formation, which deteriorates the structural performance of hot rolled steels, can be avoided by the heat treatment of samples prior to the mechanical tests. In addition, it is found that the effect of notch geometry on the stress state is much more considerable at the notch edge than the notch center.

Aerodynamic performance improvement of WIG aircraft

PurposeThis paper aims to investigate the aerodynamic characteristics as well as static stability of wing-in-ground effect aircraft. The effect of geometrical characteristics, namely, twist angle, dihedral angle, sweep angle and taper ratio are examined.Design/methodology/approachA three-dimensional computational fluid dynamic code is developed to investigate the aerodynamic characteristics of the effect. The turbulent model is utilized for characterization of flow over wing surface.FindingsThe numerical results show that the maximum change of the drag coefficient depends on the angle of attack, twist angle and ground clearance, in a decreasing order. Also, it is found that the lift coefficient increases as the ground clearance, twist angle and dihedral angle decrease. On the other hand, the sweep angle does not have a significant effect on the lift coefficient for the considered wing section and Reynolds number. Also, as the aerodynamic characteristics increase, the taper ratio befits in trailing state.Practical implicationsTo design an aircraft, the effect of each design parameter needs to be estimated. For this purpose, the sensitivity analysis is used. In this paper, the influence of all parameter against each other including ground clearance, angle of attack, twist angle, dihedral angle and sweep angle for the NACA 6409 are investigated.Originality/valueAs a summary, the contribution of this paper is to predict the aerodynamic performance for the cruise condition. In this study, the sensitivity of the design parameter on aerodynamic performance can be estimated and the effect of geometrical characteristics has been investigated in detail. Also, the best lift to drag coefficient for the NACA 6409 wing section specifies and two types of taper ratios in ground effect are compared.

Effect of geometric properties on dynamic behavior of historic masonry minaret

Historical minarets are quite sensitive structures against horizontal loads as they are tall, slender and masonry constructions. Due to their special characters, significant damages are occurred in critical part by devastating earthquakes. These damages lead to more comprehensive studying about minarets. In this study; the effect of geometrical features was investigated for dynamic behavior of seven historical masonry minarets in Bursa. However, dynamic character identification of historical masonry minarets are so difficult. Therefore, ambient vibration test were performed with aim of defining modal parameters of the minarets. Since the structural behavior of historical minarets were also represented with mathematical models, three dimensional (solid) models were implemented by using the finite element software Abaqus Cae. Model updating was performed in order to match the natural frequencies arising from the experimental investigation with those from numerical results. According to the results obtained from both forms, effect of geometric features on the dynamic behavior of minarets was evaluated. The relationships are between the first mode period of the minarets and the structural properties such as height, cross section, boundary condition. Then, the analytical formula was derived from the relationships for rapid estimation of the fundamental period of the typical Ottoman minarets. Finally, it was found that the period of the minarets from the formula close enough to modal test and modal analysis results.

Studies on geometrical metallic frusta for inward inversion by finite element simulation

The shell structures are good energy absorber while undergoing large deformations. An inward inversion of shell structure is an important large deformation phenomenon which is better controlled for axial load. In the past, the inversion phenomenon has been studied on simple shell geometries like circular tubes and frusta, which were easy for manufacturing. Hence, a theoretical inward inversion study was planned on complex geometrically featured capped end shells, whose manufacturing is difficult, in practical. Their force displacement behaviour is discussed in details taking into account of effect of geometrical features and support conditions. The energy absorbed in the inversion process has taken into account the material deformation and self-contact. The energy absorbed by each sample, prior to touching disjointed part is calculated and compared. The parameters like weight, material and thickness were varied for samples to see their effect on large deformation behaviour. This paper also gives an idea on frusta geometry which can give good energy absorbing capacity.

Safety Analysis of Freeway Segments with Random Parameters

The purpose of this study was to analyze the effect of geometric features on freeway crashes while accounting for the effect of unobserved factors likely to influence crash occurrence. The investigation was also motivated by the reality of the distribution of crashes in space not being limited to only the influence areas of the divergence and convergence segments and the weaving segments. Areas beyond the influence areas were observed to have crashes, and those areas included, data in the weaving and nonweaving segments can be clustered to quantify the variability of unobserved factors through the variance of random parameters using multilevel count models. The model results indicated that 13.9% of the variation in crash frequency was unaccounted for; this finding indicated the existence of unobserved factors influencing the occurrence of crashes. It was also revealed that weaving segments had the highest between-segment variance compared with nonweaving segments. In addition, it was revealed that more vehicles and short segments increased crash frequency while a wider right shoulder decreased crash frequency. It was also found that weaving segments decreased crash frequency compared with nonweaving segments. These results indicate that by allowing parameters to vary across segments, it is possible to capture and quantify unobserved factors. Ignoring these factors results in biased coefficients in a multilevel setting because the estimate of the standard errors will be incorrect.

The development of fatigue design formulas for the outer brace SCFs in offshore three-planar tubular KT-joints

A set of parametric stress concentration factor (SCF) analyses is carried out in the present research for right-angle three-planar tubular KT-joints under three different axial loading conditions. Three-planar KT-joints are one of the most important joint types in the six-legged offshore jacket-type structures since they connect the bracing members to the main legs of the jacket template. The analysis results are used to present general remarks on the effect of geometrical characteristics and loading conditions on the SCFs at different saddle positions on the main (outer) braces. Based on the results of FE analyses which are verified against the experimental data, a complete set of SCF databases is developed. Afterwards, through nonlinear regression analysis, a new set of SCF design equations is established for the fatigue design of three-planar KT-joints under three different axial load cases. An assessment study of these equations is conducted against the experimental data and the acceptance criteria proposed by the UK Department of Energy (DoE).

Geometrically parametric study of central brace SCFs in offshore three-planar tubular KT-joints

In the present paper, a set of geometrically parametric FE stress analyses is carried out for right-angle three-planar tubular KT-joints under three different axial loading conditions. Three-planar KT-joints are one of the most important joint types in the six-legged offshore jacket-type structures since they connect the bracing members to the main legs of the jacket template. The analysis results are used to present general remarks on the effect of geometrical characteristics on the stress concentration factors (SCFs) at different saddle positions on the central braces. Based on the results of FE analyses which are verified against the experimental data, a complete set of SCF databases is developed. Afterwards, through nonlinear regression analysis, a new set of SCF design equations is established for the fatigue design of three-planar KT-joints under three different axial load cases. An assessment study of these equations is conducted against the experimental data and the acceptance criteria proposed by the UK Department of Energy (DoE).