Stress Plots Research Articles

Computer vision for enhanced quantification of FEA of ballistic impact

In finite element (FE) modelling, the visual assessment of images of contour plots is widely used for qualitative comparison and analysis. However, this approach has limitations in conducting in-depth and comprehensive analysis, which is rigorously made based on objective, massive, and quantitative data. To tackle the problems, we propose a methodology based on computer vision with k-means clustering algorithms, providing an effective quantitative strategy to improve the efficiency and accuracy of the analysis. To demonstrate the application of this methodology, three levels of FE models on impact, viz. macro (homogenous UD laminate model), meso (yarn-level fabric model), and micro (fibre-level yarn model), are developed, where the images with both simple and complex morphologies and backgrounds are all be considered. The contour plots of stress and transverse deformation are clustered into k categories based on the RGB values of the pixels in the images. Notably, the quantification of one image using the proposed methodology is completed in seconds, and the efficiency is enhanced by approximately 40 times compared with that using the manual method, without the accuracy sacrificed. This methodology enables the researchers to efficiently and precisely understand the ballistic behaviours of the textile materials from the perspectives of fibres, yarn, fabrics, etc., and has great potential to apply in other research fields, where computational simulation is widely used.

SYNTHESIS OF RATIONAL CONSTRUCTIVE SOLUTION OF STEEL ROOF TRUSSES

The article examines the issue of the occurrence and influence of bending moments on the bearing capacity of a combined steel truss made of rectangular bent-welded profiles. A comparative analysis of technical and economic indicators in terms of material intensity, labor intensity, and cost of traditional-typical and lightweight combined steel trusses was carried out. The paper examines steel trusses of long-span buildings with a span of 30 m. The force graphs (bending moments and axial forces) for various calculation schemes of the combined steel truss are shown. An analysis of the forces in the combined truss for different ways of connecting the lattice to the chords was carried out. The plot of normal stresses along the middle line of the stiffening girder of the combined truss for various calculation schemes is presented. The load-bearing capacity of compressed rods with different connection methods was calculated. According to the research results, an engineering method of taking into account the influence of bending moments is proposed.

Effect of Elevated Acetabular Cup on Contact and Failure Analysis in Hip Implants for Different Microseparations and Cup Inclinations Under Routine Gait Activities Using In Silico Approach.

The acetabular cup design plays a critical role in reducing contact stress between femur head acetabular cup. Many studies used ellipsoidal and spheroidal geometry in acetabular cup design to effectively reduce contact stress. The present study focuses on elevated acetabular cup rim with round corner design to reduce contact stress with round corner geometry. The cobalt chromium femur head and cup are considered for finite element (FE) model of hip resurfacing. The gait loads of routine activities of humans like normal walking, stair ascending and descending and sitting down and getting up gait activities are applied to the developed 3D FE model. Five microseparations of 0.5, 1, 1.5, 2 and 2.5mm are considered in the present study. The acetabular cup inclination angle considered for this study are 35°, 45°, 55°, 65° and 75°. The contact stress and von Mises stress plot for each gait activities under these microseparations are analyzed for betterment of longevity of implants. Overall elevated cup rim design helped in reducing contact stress to a greater extent than conventional cup with different geometries. Also, the predicted von Mises stress for all the parameters considered in the current study are well within the yield strength of CoCr material. Therefore, elevated cup rim could be used as a better alternative to spline and, ellipsoidal and circular geometries of cup.

Liberating Thai History: The Thai Past in an Asian Century

Abstract The nationalist plot of modern Thai history stresses the kingdom’s exceptionalism as the only un-colonized state in Southeast Asia and highlights the steadiness of unbroken monarchy. Critics of the established narrative by contrast argue that Siam/Thailand bore many similarities to neighboring satellites of the Western powers that subordinated traditional authority and hence was a “semi-colony” of the West rather than a truly independent state. This paper argues that the semi-colonial view remains a better frame to study modern Thai history and that semi-coloniality produced a hybrid political culture among an educated new generation born around 1900. The young generation forged the popular struggles that after the 1932 end of the absolute monarchy sought to build a more fair and equitable society. These aspirations and the hybrid political culture of the time are a crucial but often overlooked part of modern Thai history.

Metamaterials with modulated coefficient of thermal expansion and ultra-low thermal stress

Mechanical Metamaterials, which integrate multi-material systems, possess the exclusive capability to modulate the coefficient of thermal expansion (CTE). However, the thermal stress induced by the uncoordinated deformation of multi-material seriously restricts their engineering applications under cyclic and extreme temperature variations. Here, an innovative Zigzag Connection (ZC) metamaterial is originally developed to integrate the modulated CTE and ultra-low thermal stress, in contrast to the End-to-end Connection (EC) and Side-to-side Connection (SC) metamaterials reported in the literature. The mechanism and theoretical analysis of the CTE and thermal stress are established and validated through numerical simulations. It is revealed that the EC and SC metamaterials consistently generate the high thermal stress far beyond the yield strength, while the newly designed ZC metamaterial simultaneously exhibits the modulated CTE and ultra-low thermal stress. Moreover, an Ashby plot of CTE versus thermal stress is illustrated, and the concept of temperature variation tolerance is defined to guide the comprehensive design of these metamaterials. The ZC metamaterial shows a higher temperature variation tolerance within compared with the EC and SC metamaterials. Overall, the ZC metamaterial emerges as a solution for the inherent conflict between the modulate CTE and thermal stress, highlighting its obvious superiority of applications under high-temperature environments.

Experimental study of coherent structures and bed shear stress on a smooth bed under a solitary wave

The coherent structures induced by a solitary wave on a smooth bed were studied in a wave flume. The solitary wave was near the point of incipient breaking and the wave Reynolds number was in the intermittent turbulent regime. The velocity field inside the bottom boundary layer was measured using a Particle Image Velocimetry (PIV) system. The bed shear stress was obtained from the measured velocities in the viscous sublayer by employing the Newton's law of viscosity. It was found that the generation and maintenance of turbulent coherent structures in a solitary wave boundary layer was like that observed in oscillatory flow boundary layers at similar wave Reynolds numbers, a process that was first described as the bursting phenomenon in the wall boundary layer of steady flows. The effect of coherent structures on the instantaneous velocity profile and bed shear stress was examined. Ejections and sweeps were found to play a crucial role in producing large bed shear stress fluctuations. Quadrant analysis and probability distribution plots of the bed shear stress showed that sweep (Q4) events were responsible for producing instantaneous bed shear stress values as high as four to five times the standard deviation above the mean, while ejection (Q2) events produced bed shear stress values mostly below the mean. Both types of events were more numerous than outward interaction (Q1) and inward interaction (Q3). It was also found that a high proportion of the measured velocity profiles that did not follow the law of the wall were associated with large vortices in the boundary layer. It was shown that the instantaneous velocities did not conform to a law-of-the-wall velocity profile unless the measured velocity field was averaged over an area large compared to the vortices.

Predictions of the behavior of a single droplet and blends composed of Newtonian/viscoelastic minor phase and viscous major phase subjected to oscillatory shear flow

The oscillatory behavior of Newtonian and viscoelastic droplets in a Newtonian phase and blends composed of viscoelastic minor phase in a Newtonian major phase are theoretically investigated in this work. The non-Newtonian constrained volume model predictions are compared to experimental oscillatory shearing flow data of droplet and blends that are available in the literature. For a Newtonian droplet in a Newtonian phase, the model describes experimental droplet behavior well at high viscosity ratio and high strain amplitude. For viscoelastic droplet in a Newtonian phase, the model predicts less deformation for viscoelastic droplet than a comparable Newtonian droplet. For large amplitude oscillatory shear rheological data of blends composed of Boger fluid minor phase in a Newtonian major phase, the model shows improvement in prediction of the elastic modulus at high viscosity ratio, compared to the Newtonian model. The model also shows good agreement with large and minimum strain elastic moduli and large and minimum rate dynamic viscosities for small and large viscosity ratio viscoelastic polymer blends. For the blend of Boger fluid minor phase in a Newtonian major phase at viscosity ratio larger than one, we find that elasticity contributes to total stress from small to large strain amplitude values. For the blend of Boger fluid minor phase in a Newtonian major phase at viscosity ratio smaller than one, we find that elasticity is important only at large values of strain amplitude. Moreover, for the aforementioned blend at viscosity ratio larger than one, the predicted Lissajous Bowditch plots of excess stress do not reflect droplet shape/droplet orientation, and the opposite is true for the small viscosity ratio blend. Investigation of droplet long semi axis for the large viscosity ratio blend at LAOS conditions reveals oscillations at two to three times the imposed frequency.

DYNAMIC LOADING EFFECTS ON CAR SUSPENSION COMPONENTS DURING ROAD DRIVING

Suspension system plays a vital role in providing a pleasure and safe driving experience. Because of that, studying the behaviour of suspension system during road driving is crucial. This paper describes the work carried out to investigate the dynamic loading effects on suspension components during rough road driving and analyse based on safety factor and fatigue life. A multibody simulation using SolidWorks software is conducted. Von Mises stress, strain, and displacement distribution plots are generated to visualize stress and deformation patterns. Fatigue life distribution plots indicate infinite fatigue life strength for the majority of components. Kinematic and compliance test examines roll centre, vertical movement of the wheel centre, toe angle and camber angle. This comprehensive analysis contributes to suspension system design and optimization, improving vehicle safety and durability.

Impact of RF stress on different topologies of 100 nm X-band robust GaN LNA

In this article, we study the robustness of 3 versions of a single stage LNA configured according to different modes of detectivity or robustness against electromagnetic jamming signals. Four successive sequences of RF step stress at 10 GHz are applied to each of the 3 LNAs under study. These robust MMIC LNAs have been designed using the D01GH GaN process from OMMIC technology, to switch from a nominal low noise mode to a high linearity mode. This DC-bias switch allows increasing the power input 1 dB compression point by 8 dB. This study focuses on the robustness of these LNAs (LNA#A for agile) when they operate under nominal low-noise mode (featuring lower IP1dB) or under nominal high-linearity mode (at the price of a degraded noise figure NF50). This original LNA#A is compared to a robust conventional design using a larger sized device (LNA#R for robust). The step-stresses are operated at 10 GHz, which is the center frequency band of these LNAs. All modes of operation are shown to exhibit fairly reproducible step stress plots, although thermal or nonlinear effects can be differentiated between low-noise and high-linearity operating conditions, and compared with the robust design LNA#R. We demonstrate the relevance of an alternative approach to conventional LNA circuit design strategies in order to achieve natural electronic protection, without a limiter placed before the LNA#A or LNA#R or without turning-off the DC-biasing: this protection option benefits from maintaining the LNA in an operational detection situation for longer when the incident input signal increases, without any degradation in electrical performance (DC and RF) or noise (NF50), even after many sequences of RF step stress.

Efficiency improvement of dual active bridge converter using simple graphical optimization method

SummaryAiming to the problems of high circulating current and low efficiency caused by the traditional strategy of dual active bridge (DAB) converter under light load, in this paper, simple graphical optimization method (GSO) is proposed to improve the efficiency of dual active bridge converter. Through the contour plot of transmission power and current stress, optimal efficiency point can be obtained by tangent of contour map under condition of constant power, and heavily calculation or complex iterations of existing conventional control strategies are avoided. Moreover, analysis of proposed graphical current stress optimization is addressed, and controller design of proposed method is given and described. Efficiency comparison between traditional modulation strategy and GSO is given to show the advantage of proposed mothed. An experimental prototype is built to verify the analysis.

Influence of Deformation of Metal Matrix on the Mechanical Properties of Poly(Ethylene Terephthalate) Inside It

The influence of different types of deformation of the metal matrix on mechanical behavior of the amorphous PET film upon its transverse compression in the ductile metal matrix has been investigated. Three deformation modes have been probed. In the first case, a disc-shaped polymer specimen has been put between two 5 mm thick discs of the lead–tin alloy and squeezed in the press. In the second and the third cases, planar elongation has been performed in the so called “dead channel”, i.e., the channel with fixed side walls, the film being elongated due to decrease in the width or thickness, respectively. The plots of true yield stress at different draw ratios have formed a common master curve. At high total draw ratio Λ, the true yield stresses have been close for the considered three types of drawing in the metal. At the draw ratio Λ 2.6, the neck has not appeared, and the specimen has been deformed uniformly. When the film in the channel is elongated due to the decrease in thickness at constant width, the specimen width has been mainly decreased during subsequent elongation in the testing machine. When the film in the channel is elongated due to the decrease in width at constant thickness, further elongation has mainly led to the decrease in the specimen thickness. The true stress Σ has been expressed as Σ = Σ0 + KΛ3, with K being a constant. Deformation of the polymer in the channel occurred with the formation of shear bands. At the preliminary draw ratio Λ = 1.82, the bands have been oriented at the angle 21.5° with respect to the stretching axis. The planar elongation has led to abnormally strong deformation softening of the polymer. The drawing has been accompanied by an increase in the elasticity modulus of the polymer. The obtained results have suggested that the macromolecules orientation is the main reason for strain hardening of the polymer.

Multimodal remote sensing application for weed competition time series analysis in maize farmland ecosystems

Although weeds cause serious harm to crops through competition for resources, they also have ecological functions. We need to study the change law of competition between crops and weeds, and achieve scientific farmland weed management under the premise of protecting weed biodiversity. In the research, we perform a competitive experiment in Harbin, China, in 2021, with five periods of maize as the study subjects. Comprehensive competition indices (CCI-A) based on maize phenotypes were used to describe the dynamic processes and results of weeds competition. The relation between in structural and biochemical information of maize and weed competitive intensity (Levels 1–5) at different periods and the effects on yield parameters were analyzed. The results showed that the differences of maize plant height, stalk thickness, and N and P elements among different competition levels (Levels 1–5) changed significantly with increasing competition time. This directly resulted in 10%, 31%, 35% and 53% decrease in maize yield; and 3%, 7%, 9% and 15% decrease in hundred grain weight. Compared to the conventional competition indices, CCI-A had better dispersion in the last four periods and was more suitable for quantifying the time-series response of competition. Then, multi-source remote sensing technologies are applied to reveal the temporal response of spectral and lidar information to community competition. The first-order derivatives of the spectra indicate that the red edge (RE) of competition stressed plots biased in short-wave direction in each period. With increasing competition time, RE of Levels 1–5 shifted towards the long wave direction as a whole. The coefficients of variation of canopy height model (CHM) indicate that weed competition had a significant effect on CHM. Finally, the deep learning model with multimodal data (Mul-3DCNN) is created to achieve a large range of CCI-A predictions for different periods, and achieves a prediction accuracy of R2 = 0.85 and RMSE = 0.095. Overall, this study use of CCI-A indices combined with multimodal temporal remote sensing imagery and DL to achieve large scale prediction of weed competitiveness in different periods of maize.

Semi-analytical method for solving stresses in slope under general loading conditions

Abstract Assessing the stress distribution within the slope in geotechnical engineering is critical. Despite the widely available numerical methods, no analytical solutions are available for determining the stress distribution within a slope under general loading conditions. This study presents a method of analytically approximating elastic stresses within a slope of arbitrary inclination subject to general surcharges and supporting forces. The prototype model of this problem is equivalent to a superposition of two sub-models: a half-plane body subjected to an initial earth stress field as well as surcharges on the crest (Model I) and a slope loaded by the release stresses caused by excavation, together with supporting forces on its inclined surface and bottom (Model II). The former stresses can be calculated analytically using Flamant’s solution, and the latter stresses can be further thought of as being composed of two additional components: one in an infinite plane with a half-infinite hole loaded by virtual tractions upon hole’s boundary (Model II1), which can be analytically approximated, and the other in a half-plane subjected to virtual tractions along the ground surface (Model II2), which can be calculated analytically as well. The two sets of virtual tractions that lead to stresses in Model II are calculated using an iterative process. The current approach provides analytical approximations of elastic stress solutions for slopes that are sufficiently close to the exact ones as accurate as much. A case study demonstrates that such solutions are in good agreement with those of the finite-element method’s over the entire region, the stresses within the region up to 10−11 times the slope’s height away from the slope toe can also be accurately determined using the current method. With this method, contour plots of stresses within a slope inclined at various angles are presented, which can be applied directly in practical engineering.

Analysis of stress development during kiln drying of beech timber

Before use, timber must have reduced moisture content. Kiln drying causes cracking risk. This study aims to evaluate the risk of cracking during the drying of beech wood samples using the response surface methodology. Additionally, we aim to develop an empirical model that describes critical tensile stress during the early drying stages and the air parameters commonly used in kiln-drying schedules for beech timber, specifically, the effects of dry-bulb temperature (DBT) and wet-bulb depression (WBD). Nine options of drying conditions were analyzed in the study according to the Central Composite Design assumptions; they were combinations of three options of DBT (30, 40, and 50 °C) and three options of WBD (4, 5, and 6 °C). During the experiments, tangential shrinkage of the wood samples was completely restrained with a load cell that measured generated tensile drying stresses. The results of the ANOVA analysis confirmed that the DBT is the only factor significantly influencing the tensile stress at failure (σf). The second-order effect between DBT and WBD has also been confirmed. The drying condition causing the highest risk of cracking was shown using the multiple contour plots of tensile stresses and the moisture content at failure (MCf). Reliability theory was used to predict the cracking risk of wood tissue. The analysis confirmed the dependence of the cracking risk of wood tissue on drying conditions. When DBT is equal to 30 °C, the cracking risk increases as the air relative humidity (RH) decreases. However, during the drying of beech wood samples at a temperature of 50 °C, decreasing the RH in a range corresponding to the increase of WBD from 4 to 6 °C reduces the cracking risk, which is indicated by the lower moisture content at failure (MCf) of the wood samples.Graphical

Experimental and finite element investigations on formability of friction stir welded tailor welded blanks of AA6061 and AA2017

Basically, the use of forming limit diagrams has been increased and dertermined as a recognizing technique for obtaining tailor welded blank's formability. In this present investigation, an effort was made to calculate the formability of friction stir welded (FSW) dissimilar alloys by varying the three main process parameters such as tool rotational speed (TRS), weld speed (WS), and tool tilt angle (TTA). All possible combinations of dissimilar sheets were used for experimental and simulation studies to test the limiting dome height. Material characteristics such as densities, young's modulus, as well as all behaviors of blanks were manually allocated for simulation, using true stress vs true strain plots. The simulation process is performed by considering the whole blanck as three zones with heights of limiting dome seem to be nearer with simulation studies and experimental results. With consideration of Forming limit diagram along with assistance of profiles of strain distribution the formability of all dissimilar blanks was evaluated. Blanks that were tailor welded at a TRS of 13,00 rpm, WS of 20 mm/minute, and tool tilt angle considering 10 exhibited higher formability compared to the blanks friction stir welded at various conditions.

Ballistic impact study on fibre reinforced polymer composites using FEA

Numerical modeling is one of the essential tools for predicting the ballistic impact strength of hybrid polymer composites without damaging the sample. The purpose of this work is to analyze the ballistic behavior of carbon/glass fibre reinforced epoxy-based composites. To investigate the effect of stacking order, modeled two different laminates containing carbon fibre and glass fibreto predict the impact behavior. High-velocity impact tests were performed with mild steel projectiles with high impact velocities. Finite element modeling was used to analyze the tensile, flexural and ballistic impact behavior of all laminates. The impact strength of laminates is evaluated using various stress plots. The results showed that the ballistic resistance was mainly affected by the fibre stacking order, fibre type, fibre orientation, and laminate thickness.

Building Resilient Crop Production Systems for Drought-Prone Areas—A Case for Bambara Groundnut (Vigna subterranea L. Verdc) and Groundnut (Arachis hypogaea L.)

Drought is a major crop production constraint worldwide. Some legume crops are known for their ability to resist water deficit stress. This study evaluated the responses of bambara groundnut (Vigna subterranea (L.) Verdc) and groundnut (Arachis hypogaea (L.) to soil water deficit stress. The experiment was set as a split-plot randomized complete block design. Three bambara groundnut landraces: viz DodR, NALBAM 4 and S19-3, and one groundnut variety, MNANJE, were assigned to subplots with three water regimes assigned to main plots (regime one: irrigated throughout the growing period, regime two: water deficit stress was imposed at the start of flowering to the end of first flush flowering, regime three: water was withheld during the pod development). Water deficit stress increased proline content by 123% in stressed plots. The highest (174%) and lowest (89%) proline increases were evident in the genotypes MNANJE and NALBAM 4, respectively. Water deficit decreased stomatal conductance, transpiration rate and photosynthetic rate, with MNANJE and S19-3 showing the smallest percentage decrease in most of the traits. This suggests that the two genotypes are drought resistant. The variations observed among landraces could be exploited to breed resilient varieties for cultivation in drought-prone areas, ultimately improving food security.

Technological and metallophysical researches of surfaces during laser methods

The article considers the aspects of changing the metallophysical parameters of the surface layer (microhardness, stress plot, phase and structural compositions), as well as the roughness and size of the surface layer, which are formed by laser technological methods (cutting, welding) and combined based on laser radiation (laser thermal hardening and ultrasonic smoothing). Laser welding modes are optimized according to the crack resistance criterion; the phase composition in the zone of thermal influence during laser cutting can change not only due to internal structural transformations, but also under the influence of external factors (process gases, nozzle design, etc.). Combined combinations based on laser radiation (laser thermal hardening and ultrasonic smoothing) provide the formation of a plot of compressive stresses with the growth of the latter by 30–45 %; an increase in hardness by 40...50 %; a decrease in roughness by 5...6 %. All these studies have ensured the introduction of the considered laser methods into the production cycle.

Мultiplicative simulators based on laser technological methоds

Сreate multiplicative simulators based on laser technological metоds is a very modern scientific problem. The article considers the aspects of changing the metallophysical parameters of the surface layer (microhardness, stress plot, phase and structural compositions), as well as the roughness and size of the surface layer, which are formed by combine technological methods). Regime of combine methods are optimized according results of metallophysical researches. Combined methods based on energetic external attacks. Provide the formation of a plot of stresses, hardness, roughness ets All these studies have ensured the introduction of the considered combine methods by optimize metallophysical researches.

2D and 3D numerical investigation on contact stress behaviour on different combinations of gear pair

Polyamide (PA6) polymer gear tremendously expanded its usage in power transmission applications. PA6 gear were engaged with different combinations of gear pairs (STEEL – PA6, PA6 – STEEL, and PA6 – PA6) were utilized in those applications. Normally gears are subjected to Hertzian contact stress due to their non-conformal contact and ANSYS is one of the widely used Finite Element Analysis (FEA) tool to determine the contact stress behaviour of those gears. Even though numerous 2D and 3D FEA investigation were performed to determine the gear contact stress behaviour, the occurrence of surface and subsurface stresses for different combination of gear pair was not explored especially for PA6 gears. Thus, the work attempted to study the surface and subsurface contact stress behaviour of three combination of gear pairs (STEEL – PA6, PA6 – STEEL, and PA6 – PA6) using 2D (plane stress with thickness condition) and 3D FE analysis (ANSYS APDL). The optimum mesh sizes were selected from the convergence study and further simulations were performed. From the analysis, the stress was observed maximum at the contact pitch point for 2D analysis, whereas, 3D analysis showed the maximum stress at a depth below the contact surface (subsurface stress) for all the combinations of gear pairs. Different trend pattern was obtained between the stress plot of 2D (surface stress) and 3D (subsurface stress) analysis for all the gear pairs. The variation in depth occurrence of maximum stress was observed for Steel-PA6 (0.16 mm depth), PA6-Steel (0.16 mm depth) and PA6-PA6 (0.25 mm depth) gear pairs. And, the Polymer – Polymer (PA6-PA6) gear pair exhibited higher depth occurrence compared to Steel – PA6 and PA6 – Steel gear pairs.