Changes In Cross-sectional Shape Research Articles

Parametric modeling and multiobjective crashworthiness design optimization of a new front longitudinal beam

The front longitudinal beam (FLB) is the most important energy-absorbing and crashing force–transmitting structure of a vehicle under front-impact collision. For better weight reduction and crashworthiness of the FLB, a new structure, variable rolled blank–variable cross-sectional shape FLB (VRB-VCS FLB), is proposed. It has both the continuous variation of thickness and variable cross-sectional shape in space. As the thickness distribution and cross-sectional shape change continuously, the proposed structure evolves into three distinct forms, i.e., the uniform-thickness FLB, variable rolled blank FLB, and variable cross-sectional shape FLB. However, literature on parametric modeling and crashworthiness design optimization of the VRB-VCS FLB is very limited. This paper proposes a parametric modeling method of VRB-VCS FLB with manufacturing constraints. Multiobjective crashworthiness design optimization is performed to explore the lightweightness and crashworthiness performance of the VRB-VCS FLB. Firstly, thickness distribution and cross-sectional shape parameters are defined. Secondly, local parametric subsystem front-impact model is established to balance accuracy and efficiency. Thirdly, a multiobjective optimization model of VRB-VCS FLB is constructed. Finally, a fully automated design of experiment platform is established to improve the data collection efficiency, and epsilon-support vector regression technique and non-dominated sorting genetic algorithm II are utilized to search the Pareto optimal frontier. The numerical results show that the lightweightness and crashworthiness of the VRB-VCS FLB are significantly improved when compared with the uniform-thickness FLB.

Axial buckling behavior of single-walled carbon nanotubes: Atomistic structural instability analysis

To reveal the atomistic scale mechanism of buckling of single-walled carbon nanotubes (SWCNTs) under axial compression, we carried out molecular dynamics (MD) simulation and atomistic structural instability (ASI) analysis. The ASI analysis enables us to reveal the development of ‘latent’ instability modes until buckling of structure, which cannot be clarified with MD alone. Euler-type buckling was found in relatively thin and long nanotube models, while buckling triggered by change of cross-sectional shape (i.e., radial buckling) was found in thick and short models. With growing radius, a crossover between the Euler-type and radial buckling modes was clearly found in the ASI analysis. Even when the deformation behavior was apparently the same, the buckling can be triggered by different instability modes. We also analyzed the structural instability using the Flügge theory based on linear continuum mechanics (LCM) to compare the results with the ASI analysis. Initial eigenvalues and development of instability modes were different between the ASI and LCM results, leading to a significant deviation of buckling strain and instability crossover points. We investigated the effect of chirality of CNT which is difficult to explain by LCM.

Performance characterization of multifunctional different cross-sectional-shaped coaxial composite filaments for SMART textile applications

The aim of this study is to investigate the effect of spinneret design parameters on cross-sectional shape and mechanical performance characteristics of coaxial composite filaments. A number of different cross-sectional-shaped metal/polymer core/sheath coaxial composite filaments were developed by changing spinneret design parameters. The cross-sectional shapes obtained were circular, rectangular, triangular and elliptical shapes. The mechanical performance of filaments was evaluated for application in sensors and actuators. The change of cross-sectional shape significantly influences mechanical properties of developed filaments which express their vulnerability during applied stresses in their life cycle.

Computational and experimental study on dynamic instability of extended bistable carbon/epoxy booms subjected to bending

Bistable reeled composite booms (BRCs) constructed from braided carbon/epoxy plies are suitable candidates for use as extendible booms or as elements of large deployable space structures. However, without modification, BRCs have an open section which limits their torsional stiffness, and makes them prone to collapse under low bending moments. In this study a “roll-up” deployable photovoltaic (PV) solar array with two side-by-side extendible BRCs is used as a case study to analyse the dynamic behaviour of BRCs on spacecraft undergoing rotational manoeuvres numerically. The BRCs have rotational accelerations applied to their roots to simulate the effect of being attached to a manoeuvring spacecraft. Budiansky-Hutchinson criterion is used to define an instability failure point based on a change in cross-sectional shape. This was used to estimate the maximum angular acceleration. While it is extremely difficult to replicate the behaviour of a large flexible lightweight structure in microgravity on the ground, an experiment to determine the point of collapse of BRCs under gravity were used to verify the simulation results.

Atomistic Model Analysis of Deformation of Carbon Nanotubes under Axial Compression

We carried out molecular dynamics (MD) simulation and atomistic instability (ASI) analysis with carbon nanotubes (CNTs) under axial compression to reveal the mechanism of buckling. We investigated the development of instability mode until buckling of structure. For single-walled carbon nanotubes (SWCNTs), Euler-type buckling was found in relatively thin and long nanotubes, while buckling with deformation change of cross-sectional shape (radial buckling) was found in thick and short carbon nanotubes. The crossover between the Euler-type buckling modes and radial buckling modes was clearly seen in the ASI analysis.

Impact of the Three Gorges Dam on sediment deposition and erosion in the middle Yangtze River: a case study of the Shashi Reach

Channel morphology in an alluvial river usually varies due to the altered flow and sediment regime from upstream damming. This paper reports an evaluation of the dynamical changes of sedimentation and erosion in the middle and lower reaches of the Yangtze River after operation of the Three Gorges Dam (TGD). Here, we present the results from a case study of the Shashi Reach in the middle Yangtze River, which is the first sandy-bed and meandering reach downstream of TGD. Databases were constructed using a digital elevation model of channel topography based on the 1:10,000 topographic maps from the 1980s to 2012 and hydrological records from 1956 to 2013. Results indicate that the erosion in the Shashi Reach was mainly confined to the deeper channel and that it has increased since the construction of the TGD. No significant changes were observed above the bank-full level, resulting in the decrease of the width-to-depth ratio. These changes may be principally caused by variations of the seasonal distribution of flow and sediment due to the operation of the dam. In addition, results show that the cross-sectional shape change of the channel is related to the relative erodibility of the channel bed and bank material.

Visualization of chicken embryo heart motion

We present a geometric surface parameterisation algorithm and multiple visualisation techniques (cross-sectional area and shape change, peristaltic motion, stress/strain, volume change, surface curvature change several visualisation techniques) adapted to the problem of understanding the 4D peristaltic-like motion of the outflow tract (OFT) in an embryonic chick heart. We illustrated the techniques using data from hearts under normal conditions (four embryos), and hearts in which blood flow conditions are altered through OFT banding (four embryos). The overall goal is to create quantitative measures of the temporal heart shape change both within a single subject and between multiple subjects. These measures will help elucidate how altering hemodynamic conditions changes the shape and motion of the OFT walls, which in turn influence the stresses and strains on the developing heart, causing it to develop differently. We take advantage of the tubular shape and periodic motion of the OFT to produce successively lower dimensional visualisations of the cardiac motion (e.g. curvature, volume and cross section) over time, and quantifications of such visualisations. These visualisations enable a more fine-grained understanding of how the contraction wave moves through the OFT and the cross-sectional shape change that accompanies it.

Perbandingan Hasil Pemodelan Aliran Satu Dimensi Unsteady Flow dan Steady Flow pada Banjir Kota

One dimensional flow is often used as a flood simulation for the planning capacity of the river. Flood is a type of unsteady non-uniform flow, that can be simulated using HEC-RAS. HEC-RAS software is often used for flood modeling with a one-dimensional flow method. Unsteady flow modeling results in HEC-RAS sometimes refer to error and warning due to unstable analysis program. The stability program among others influenced bend in the river flow, the steep slope of the river bottom, and changes in cross-section shape. Because the flood handling required maximum discharge and maximum flood water level, then a steady flow is often used as an alternative to simulate the flood flow. This study aimed to determine the advantages and disadvantages of modeling unsteady non-uniform and steady non-uniform flow. The research location in the Kanal Banjir Barat, in the Semarang City. Hydraulics modeling uses HEC-RAS 4.1 and for discharge the plan is obtained from the HEC-HMS 3.5. Results of the comparison modeling hydraulics the modeling of steady non-uniform flow has a tendency water level is higher and modeling of unsteady non-uniform flow takes longer to analyze. Results of the comparison the average flood water level maximun is less than 15% (± 0,3 meters), that is 0.27 meters (13.16%) for Q50, 0.25 meters (11.56%) for Q100, dan 0.16 meters (4.73%) for Q200. So the modeling steady non-uniform flow can still be used as a companion version the modeling unsteady non-uniform flow.

Numerical simulation on geometrical parameters for closed sump

The closed sump is a typical inlet passage of middle and small pumping station. It has the characteristics of low channel height, small foundation excavation depth, simple structure, a single cross sectional shape changes, ease of construction and other features, so more and more attention and application has been paying on this closed sump in pumping station project. However the flowing pattern within the closed sump is complex, the design is not perfect in some respects, the structure size does not be optimized. Based on the background for renewal and transformation of a pumping station, according to the three-dimensional incompressible fluid Reynolds-averaged N-S equations, the RNG k-e model, the CFD technology. The study on the draught in closed sump might reduce the length of pump shaft to enhance the stability of the pump unit operation. The results reveal the effect of the change of the height of plate. The turbulence in back wall might cause vortex when the height is high. The height of plate had be recommended control in 0.65D-0.85D.The better parameter combination of geometry of closed sump had be given through comparing the results of the orthogonal test and the comprehensive test. The floor clearance should be control in 1.0D. (D is the diameter of flared pipe)

Change in Cross Sectional Shape for Hollow Filament During Winding

Methods for obtaining hollow-fiber membranes are limited (due to the small diameter) compared with methods for obtaining other membranes. An important problem in obtaining hollow filaments by any method is development of devices for take-up of the semi-permeable hollow fibers. This is due to the specific characteristics of hollow filaments (the presence of an internal cavity). During winding of hollow filaments, loss of stability can occur under the action of radial pressure arising in the take-up from winding tension. We will consider the critical pressure to be the lowest external pressure at which the initial shape of the hollow filament cannot be recovered when the external pressure is relieved. In this work, we have analyzed the conditions for loss of stability in hollow filaments when they are obtained on equipment for building packages.

Secular Change in the Femur Diaphyseal Biomechanical Properties of American Whites

Over the past two centuries there have been documented secular changes in stature, weight, body proportions, and skeletal maturation rates in the United States. These changes along with a more sedentary lifestyle are likely reflected in femur morphology. Here we examine secular changes in diaphyseal cross-sectional size, shape, area, robusticity, and rigidity at midshaft and subtrochanteric of the femur using 395 adult white females and males from the United States born between the 1850s and the 1970s. The effect of secular change was controlled for an age effect. We also examine the relationship between femur length (proxy for stature) and femur head diameter (proxy for body weight) on measurements of diaphyseal size and biomechanical properties. The femur morphology of Americans born in the twentieth century reflects the combination of changes in stature, body build, and activity levels. Both sexes show significant changes in femur midshaft shape due primarily to a decrease in the mediolateral diameter. There are no significant changes at subtrochanteric in size or biomechanical properties in either sex after controlling for age variation. The results suggest that the changes in femur midshaft shape are primarily associated with a decrease in activity. The stability of the subtrochanteric dimensions and femur anteroposterior diameter may reflect a combination of decreased activity with a corresponding increase in femur length (moment arm) and a decrease in body breadth.

Improvement of the Method using the Coefficient of Variation for Automatic Multi-segmentation Method of a Rating Curve

In general, the water stage-discharge relationship curve is established based on the assumptions of linearity and homoscedasticity. However, the relationship between the water stage and discharge is affected from geomorphological factors, which violates the basic assumptions of the water stage-discharge relationship curve. In order to reduce the error due to the violations, the curve is divided into several sections based on the manager's judgement considering change of cross-sectional shape. In this research, the objective-splitting criteria of the curve is proposed based on the measured data without the subjective decision. First, it is assumed that the coefficient of variation follows the normal distribution. Then, if the newly calculated coefficient of variation is outside of the 95% confidential interval, the curve is divided. Namely, the groups is divided by the characteristics of the coefficient of variation and the reasonable criteria is provided for establishing a multi-segmented rating curve. To validate the proposed method, it was applied to the data generated by three artificial power functions. In addition, to confirm the applicability of the proposed method, it is applied to the water stage and discharge data of the Muju water stage gauging station and Sangegyo water stage gauging station. As a result, it is found that the automatically divided rating curve improves the accuracy and extrapolation accuracy of the rating curve. Finally, through the residual analysis using Shapiro-Wilk normality test, it is confirmed that the residual of water stage-discharge relationship curve tends to follow the normal distribution.

Thermochromic Phantom and Measurement Protocol for Qualitative Analysis of Ultrasound Physiotherapy Systems

Thermochromic test bodies are promising tools for qualitatively evaluating the acoustic output of ultrasound physiotherapy systems. Here, a novel phantom, made of silicone mixed with thermochromic powder material, was developed. Additionally, a procedure was developed to evaluate the stability and homogeneity of the phantom in a metrologic and statistical base. Twelve phantoms were divided into three groups. Each group was insonated by a different transducer. An effective intensity of 1.0 W/cm2 was applied to each phantom; two operators performed the procedure three times in all phantoms. The heated area was measured after image processing. No statistical difference was observed in the heated areas for different samples or in the results for different operators. The heated areas obtained using each transducer were statistically different, indicating that the thermochromic phantom samples had sufficient sensitivity to represent the heated areas of different ultrasonic transducers. Combined with the evaluation procedure, the phantom provides an approach not previously described in the literature. The proposed approach can be used to quickly assess changes in ultrasonic beam cross-sectional shape during the lifetime of ultrasound physiotherapy systems.

Photoresist cross-sectional shape change caused by scanning electron microscope-induced shrinkage

Change in the cross-sectional profile of a photoresist (PR) pattern due to shrinkage was evaluated to investigate the mechanism of electron beam-induced shrinkage. A scanning transmission electron microscope (STEM) was used to observe the cross-sectional profiles of PR lines after atomic-layer deposition of metal oxide and carbon deposition on the sample surface. A HfO2 thin layer enhanced the profile contrast in the STEM measurements without blurring the edge, which enabled the precise cross-sectional measurement of the PR patterns. We found interesting features associated with shrinkage from the detailed profile change obtained using this method, such as a rounding of the pattern top, a necking of the sidewall profile, a rounding of the foot in the pattern on the organic underlying layer, and voltage-independent sidewall shrinkage under a large electron beam dose. These behaviors along with the results from a Monte Carlo simulation are discussed. Consequently, these observations experimentally clarified that the elastic deformation effect and the impact of the secondary electrons emitted from the spaces around the pattern into the sidewall are important to interpret the change in the shape of the pattern induced by shrinkage.

About the Influence of Butt Weld Joints Geometry on the Damage Detection Process

The number and diversity of global nondestructive testing methods applicable to welded structures have rapidly increased in last decades. Vibration-based damage detection methods make possible the evaluation of structures at once; the damage location can be found without having direct access to the structure’s damaged region. Butt welded components often bring complexity in the structures, since the weld introduces cross-section shape changes and alteration of the material’s physical and mechanical characteristics. Moreover, the structure continuity can be interrupted by cracks or cavities. All changes occurring due to the weld induce mutations in the structures dynamical behavior. This paper presents a method to identify structural changes by using information from the modal analysis, actually analyzing the natural frequency shifts. Mathematical relations describing the individual or coupled effect of mass change and geometrical discontinuities are derived and used in the identification process; in fact, finding the mass changes or cracks becomes an inverse problem. The mathematical models are successfully tested on virtual and real structures.

3차원 가상바디 변형을 위한 체형연구 - 40대 여성을 대상으로 -

The aim of this study was to successfully reflect human body changes on the transformation of the virtual body within 3D virtual fitting spaces. For this purpose, existing problems of shape transformation of the virtual body were analyzed and regression equations which provides useful basic data for transformation of the virtual body that can be applied usefully to the 3D virtual fitting system was developed. Necessary data for the analyses were body measurement and 3D scan data of women with average physical form between the ages of 40 through 49. The reason that we used human body changes of the female subjects in their forties was based on the recognition that fundamental female body changes start to occur from age of forty. Body shapes were largely divided into 3 groups according to obesity which was found to be the biggest factor of shape change. Seven factors were extracted based on factor analysis of 47 body measurement categories and regression equations were created to extract specific measurements for each BMI group based on these seven factors. The major contribution of this paper can be summarized as follows. First, the regression equations to extract specific measurements based on the 7 representative variables remediated existing problem of virtual bodies as it increased the number of body shape transformation areas. Second, the regression equations helped to overcome the problem of current failing to reflecting changes in body cross-section shape based on simple girth measurements based on analysis of cross-section distances.

The Precise Calculation about the Inertia Moment of Rectangular Section Beam

This paper involves in the bending deformation, the rectangular section beam precise calculation about the actual moment of inertia of neutral axis. Mainly through the analysis of correlation, deduced because of the influence of deformation of beam cross section from the original rectangle into trapezoidal, actually the section about what would happen to the actual moment of inertia of neutral axis changes, and related to accurate calculation results are obtained. At the same time regardless of the cross section shape change under the ideal state of comparing with the results of approximation, aiming to study the difference between the calculations of normal stress on the beam cross section. The results can be used to supplement the material mechanics related theoretical formula.

Study on parameters influencing shape change of melt spun cross-shaped polypropylene and poly (lactic acid) fibers

Melt spinning of cross-shaped polypropylene (PP) and poly (lactic acid) (PLA) fibers was conducted to investigate influences of polymer properties and processing conditions on cross-sectional shape change in fibers. PP fibers possessed cross-shaped profile, resembling that of the original spinneret orifice, with dull edges due to die swell. Their shape factor (SF) values (1.4–1.6) were close to that of the spinneret orifice (1.7), indicating that the complex shape of the orifice could be maintained. High melt viscosity of PP, as well as its rapid crystallization, helped preventing shape change induced by surface tension. PLA fibers, on the other hand, exhibited shape change from cross to square and to round shape when spinning temperature was increased from 200 to 220 and 240 °C, respectively. Their SF values (1.1–1.2) were close to unity, indicating shape change towards circular shape. Shape deviation towards circular shape in PLA fibers was mainly driven by surface tension. Slow crystallization in PLA allowed great influence of surface tension in determining shape change of the extrudate. Increasing fiber take up speed tended to decrease SF value. Such effect was small compared to that of spinning temperature.

Slot jet impingement heat transfer in the presence of jet-axis switching

Jet-axis switching is an established phenomenon whereby a non-circular, three-dimensional free jet undergoes a major change in cross-sectional shape with increasing downstream distance from the jet origin. This phenomenon has been demonstrated here to also occur for impinging jets. The focus of the present work is to investigate the heat transfer and fluid flow characteristics of rectangular slot jets which experience jet-axis switching. The jets in question have initial cross-sectional aspect ratios of 5:1 and 10:1. The jet cross sections, although highly skewed at first, evolve through near circularity and subsequently become skewed in the direction perpendicular to that of the initial skewness. In addition to the two initial aspect ratios, parametric variations were made of the Reynolds number, the distance of the impingement plate from the jet origin, and the contraction experienced by the flow passing through the aperture of the jet-forming orifice (i.e., the blockage ratio). The investigation was implemented by means of numerical simulation from which local and average Nusselt numbers were determined as functions of the foregoing parameters. Higher Reynolds numbers, greater downstream distances of the impingement plate, and greater blockages served to enhance the Nusselt number values. It remains to be seen whether there is an initial jet aspect ratio that is large enough to preclude axis switching and thereby allow two-dimensional modeling.

Effect of Material Properties on Cross-Section Deformation during Bending an Aluminum Extruded Section

The cross-section shape change was investigated to determine the effects of proof stress, r value, wall thickness, and cross section in push-through bending of a square extruded pipe. Extruded A6063 aluminium alloy (40×40×2.0 mm) was used in the experiment. The push-through bending machine used has a six-axis NC controller. In this study, a two-dimensional single curvature shape was adopted in order to investigate the fundamental bending properties. A high-proof-stress material with severe bending workability was examined in this experiment to clarify the effect of bending workability on the material properties. Workability was evaluated by examining wrinkles and shape change of the cross section; the change in thickness was also evaluated, as were n and r values. The results are as follows. The high-proof-stress material was bent, resulting in significant cross-section deformation. The size of wrinkles caused by bending increased due to the large bending radius, and the wrinkles produced were deep. The effect of the r value on the cross-section deformation after bending could not be determined. In the present experiment range, the bending limit was determined by the size of wrinkles in internal bending. In A6063-T1, the wall thickness had a significant effect, and the forming limit of the thin-walled material was low. The bending limit was low for A6063-T5, and the effect of the wall thickness was slight. The bending limit of a 60×60mm cross-section piece was considerably lower than that of a 40×40 mm cross-section piece, for the same wall thickness; it was particularly significant in A6063-T5.