Normal Pressure Distribution Research Articles

Modulation of the wake of a horizontal cylinder by pycnocline thickness in stratified flow

This study investigates the modulating effect of the pycnocline thickness in two-dimensional stratified flow on a cylinder. It encompasses three typical flow regimes identified by Boyer in experiments conducted within the Reynolds number range of Re = 260–2000. Quantitative control of the modulation effect of internal interface waves on the cylinder wake is achieved by varying the thickness of the pycnocline. Under appropriate thickness of the pycnocline, a multiple-centerline-structure can transition to isolated-mixed-structure flow regimes and Double-Eddy-Wavy-Wake flow regimes. Similar modulation patterns are also observed in isolated-mixed flow regimes. Normalized pressure distribution and velocity fields indicate that in low Reynolds number flow regimes (Re < 600), downstream isolated mixed regions generate dynamic pressure that periodically cascades upstream. This periodic reverse energy transfer provides favorable adverse pressure gradients, cyclically reducing the drag force on the cylinder. The cyclic period is, for the first time, classified into four stages: dynamic pressure storage stage, dynamic pressure transfer stage, dynamic pressure consumption stage, and dynamic pressure exhaustion stage. Despite the highly nonlinear modulation effect of internal interface waves in low Reynolds number conditions, the linear predictive theory of lee waves based on streamline equations remains instructive in predicting the trend of lee waves wavelength variation with pycnocline thickness. Drawing upon the modulation study results concerning the pycnocline thickness on lee waves, a regime map is constructed, illustrating the directional evolution of lee waves flow patterns based on variations in pycnocline thickness.

Modeling the Normal Contact Characteristics between Components Joined in Multi-Bolted Systems

This article is concerned with the modeling and calculation of the contact layer between components joined in a multi-bolted system for assembly conditions. The physical model of the multi-bolted connection is based on a system consisting of an elastic flange component, which is joined to an elastic support using a rigid-body bolt model. The contact layer between the joined components is described by a non-linear Winkler model. A model of the contact joint with consideration of the experimental normal elastic characteristics is presented. Examples of normal contact pressure distributions are included.

Modeling of nanoblood flow in an artery in presence of eco-friendly and biocompatible hybrid nanoparticles

Transferring biological fluid through arteries is a topic that has garnered serious interest in recent times, especially when it pertains to applications such as drug delivery. In our body, arteries serve as the primary conduits for blood flow and this study aims to model the blood flow in this situation. The working fluid is essentially pure blood, which acts as a base fluid, supplemented with nanoparticles of Titanium Dioxide (TiO2) and Gold (Au). Nanoparticles could change the thermal and rheological properties of blood which might be particularly advantageous for ensuring smoother flow or optimal distribution of drug molecules within the bloodstream. In the present work, a porous channel is considered with parallel walls that exhibit varying permeability on boundaries. Such a design enables the nanoblood to enter and exit the channel, mimicking certain natural processes like transvascular fluid exchange. Additionally, the variable height of the channel that expands and squeezes uniformly could be reminiscent of the pulsatile nature of blood flow seen in our arteries due to heartbeats. To understand the dynamics of this hybrid nanoblood flow, the governing equations are converted into a set of nonlinear ordinary differential equations using the similarity transformation approach. For solving these transformed equations, the research harnesses the BVP4C built-in function in MATLAB software. Through this computational approach, the research provides insights into the velocity and temperature profile of the fluid, the distribution of normal pressure, wall shear stress, and the Nusselt number concerning various parameters. The findings of the present study can be significant and useful in biological sciences and technologies and the detailed results are presented completely in the article’s body.

Harmonic expansion and nonsmooth dynamics in a circular contact region with combined slip-spin motion

We analyse a rigid body in planar motion while touching a rough plane at a finite-sized, circular contact area. Assuming Coulomb friction between the tangential and normal pressure distributions, the resultant forces and torques can be expressed formally with a nonsmooth dependence on the kinematic variables. In the literature, the exact form of the tangential forces is available for special pressure distributions expressed by transcendent functions; recently, an approximate linear model was introduced. Now, we present a nonlinear extension of the approximation, which can be used effectively to characterise slipping-sticking transitions between the bodies.

TESTING OF ADEQUACY OF MODELLING OF PROCESSES OF PLASTIC DEFORMATION BY A METHOD OF FINAL ELEMENTS. MODELLING OF THE MAJOR PARAMETERS OF PUNCHING

Results of calculations by a method of final elements of height of the center of plastic deformation, temperature effect of deformation, distribution of normal pressure at an end face of a punch, a corner of an elastic deflection of a matrix, specific forces of expression by conic punches are resulted and drawn the general conclusions on the given cycle of articls.

Contact behaviors involving a nanobeam with surface effect by a rigid indenter

In this study, we present a novel surface model that utilizes surface energy density to predict the surface effect in nanobeam contact problems. To address the issue of a finite-length elastic nanobeam being indented by a rigid cylindrical indenter, we propose an equivalent substitution method. This method allows us to formulate analytical relations between the load and contact half-width for two different boundary cases. The explicit expressions of the contact-zone width, the pressure distribution in the contact zone, the deflection outside the contact zone, and the load–displacement relation are obtained for the nanobeam with surface effect and are compared with classical results in detail. The results show that the influence of the surface effect is very significant for nanobeam contact behavior, especially when the half-width of the contact zone increases and the contact zone becomes two independent symmetric strips. It is also found that the length-height ratio of nanobeam and the end support conditions have a fairly obvious effect on the normalized pressure distribution, which deviates significantly from the one predicted by the classical results due to the surface effect. However, for a given beam length and indenter radius, the ratio of the width of the contact zone to the beam thickness is almost constant, independent of the indenter load and beam boundary conditions. Meanwhile, the model predicts that the contact pressure distribution after the normalization of the average indentation pressure is almost independent of the indentation load and beam boundary conditions, but obviously depends on the surface effect parameters. The present method and result should be helpful not only to the measurement of mechanical properties of the indentation nanobeam but also to the design of the nanobeam-based devices.

Optimization of a punch shape with a doubly connected contact domain

The objective is to optimize the distribution of the normal pressure under a rigid punch (indenter) having a doubly connected contact domain close to a circular ring and interacting with a homogeneous isotropic elastic half-space. In the problem considered here, the required design variable is the punch shape. The functional to be minimized is the root-mean-square deviation of the present pressure distribution from some given distribution. An analytical technique is developed for solving the problem for the punches with doubly connected shape, by reducing to a sequence of similar problems for the circular ring punches using expansions of the simple layer potential. The method of expansion in terms of a small parameter is used. The simple layer potential expansion is proposed when mapping a doubly connected integration domain onto a circular ring by transforming the integration variables and transforming the coordinates of the pole of the kernel. As a result, a set of similar problems was obtained for a circular ring to determine the functions characterizing the normal pressure distribution over a non-circular ring contact domain under the punch, as well as the normal displacements, from where the optimal punch shape is determined.

Effect of Geogrid Reinforcement and Soil Relative Density on Performance and Contact Pressures of Ring Foundations on Sand

Reinforcing soil beneath foundations is one of the standard methods to improve the foundation performance. However, soil relative density may affect the efficiency of reinforcement. This experimental study has been conducted on a model ring foundation resting on medium, dense, and very dense geogrid-reinforced sand. For this purpose, 17 tests were carried out to evaluate the effect of soil density and reinforcement depth and size on bearing capacity and settlement of the ring foundation and its normal contact pressure distribution. The results show that geogrid-reinforced sand with higher relative densities improves bearing capacity and decreases settlements significantly. It can be shown that implementing a geogrid layer that is equal to the dimensions of the footing is cost-effective. The scale effect analysis has been conducted for the model foundation, sand, and geogrid used in this research. Additionally, normal contact pressure distributions for unreinforced and reinforced sand are presented. Decreasing the depth of reinforcement transforms the form of normal contact pressure distribution from saddle to parabolic.

Upregulation of Interleukin-2 Among Hypertensive Subjects in Bayelsa State, Nigeria

Hypertension is a killer disease that increases with age. Several inflammatory biomarkers have been associated with hypertension. However conflicting reports exist on the relationship of interleukin-2 with hypertension. The objective of the present study was to determine the association of hypertension with interleukin-2 (IL-2) as well as the distribution of blood pressure among adults in Bayelsa State, Nigeria. Randomly selected 270 adults were screened for hypertension using Andon blood pressure monitor and real time PCR was used to quantify IL-2 gene expression. A structured questionnaire was used to collect sociodemographic information. A normal systolic and diastolic blood pressure distribution was found. Mean systolic and diastolic blood pressure were 123.69±22.65 and 77.60±13.53 mmHg respectively. The prevalence of hypertension was 47.4% (isolated systolic hypertension, 10.4%; isolated diastolic hypertension, 4.4%; co-occurring systolic and diastolic hypertension, 32.6%). Exactly 71.09% of hypertensive subjects were unaware that they were hypertensive. Age related increase in hypertension was found. Compared with normal control, a significant upregulation in IL-2 gene expression was found among hypertensive subjects (p < 0.05). In conclusion, the present study showed that a high prevalence of hypertension and low hypertensive status awareness exist in rural areas in Bayelsa State, Nigeria. It also showed that hypertension is associated with a significant upregulation in IL-2 gene expression. Hypertension interventions to rural areas and the use of IL-2 as a target biomarker for novel antihypertensive drug design is implicated in the present study. Keywords: [Hypertension, interleukin-2, rural areas, Bayelsa State, Nigeria]

Revealing the mechanism of tool tilting on suppressing the formation of void defects in friction stir welding

Experiments have proven tool tilting in friction stir welding (FSW) can effectively suppress the formation of void defects. However, the mechanism of tool tilting on suppressing the formation of void defects has not been revealed. In this study, a CFD model considering the influence of tool tilting is established. A non-uniform distribution of normal pressure at the tool-workpiece contact interfaces is proposed to relate to the tool tilt angle. The discrete particle tracing method is used to characterize the formation of void defects in FSW. The heat generation, temperature distribution and plastic flow behaviors between the case without (i.e. 0° tool tilt angle) and with (i.e. 2.5° tool tilt angle) tool tilting are quantitatively compared and analyzed. The results show the tool tilting in FSW leads to higher heat flux and temperature near the pin side in the middle and low parts of the workpiece. Moreover, the frictional shear stress at the pin side/workpiece contact interface significantly increases when the tool is tilting, leading to a higher driving force for the plastic material to flow. As a result, the material flows farther to the advancing side of the workpiece after bypassing the tool when the tool is tilting at 2.5°, which helps to heal the voids on the advancing side of the FSW joints. The higher temperature with higher frictional shear stress enhances the plastic material flow in the middle and low part of the joints when the tool is tilting, which is attributed to suppressing the void defects. The model is validated by experimental results.

COMPARISON OF FORGING LOAD, MATERIAL FLOW AND PRESSURE DISTRIBUTION OF THE UNI-DIRECTIONAL, BI- DIRECTIONAL AND TWO-STEP FORGING PROCESSES

Because of high productivity, closer dimensional tolerances, and minimal material waste precision forging (net or near net shape) processes have been used for manufacturing automobile components. The primary disadvantage of precision forging is the encountered higher tool stresses due to applied higher forging loads. Thus, forging load reduction is a higher priority in precision forging in terms of energy consumption and cost because higher loads required higher investment and higher energy consumption. Forging load is affected by several parameters such as temperature, material flow, the geometry of the billet, and punch movement. In this study, forging load, material flow, and normal pressure distribution in the forged part were investigated considering uni-directional, bi-directional, and two-step forging processes. FEM simulations were performed by using a solid cylindrical billet. To perform FEM simulations, the finite element analysis package (DEFORM 2D) was used. Also, experimental studies of the FEM models were performed. For bi-directional and step-forging experimental studies, a double-acting servo press was used because the movement of the top and bottom punch can be controlled accurately. Then the results of FEM and experimental studies were compared with each other. The results of the FEM simulations and experimental studies show two-step forging offers lower forging load and energy consumption whereas the uni-directional closed die forging process needs higher load and energy consumption

Determination of the value of tangential force for the half-track traction vehicle with rubber tracks

Practice shows that with insufficiently high traction qualities of traction vehicles deteriorate its operational properties. At present, extensive research is under way at home and abroad to find inexpensive but highly effective ways and techniques to improve the traction qualities of vehicles. The design of running systems with reduced resistance to movement and slipping will help to significantly increase the productivity of vehicles and reduce fuel consumption. This, in turn, will contribute to greater operational efficiency for traction vehicles. The authors of this study have developed the design of a traction vehicle with a half-tracked propulsor. The objective of the study is to develop a mathematical model for calculating the efficiency of operating a traction vehicle equipped with a half-tracked propulsior with rubber tracks. The proposed mathematical expression takes into account the deformability of the rubber tracks of the propulsor, the uneven distribution of normal pressure along the length of the track, slipping, geometric parameters of the propulsor and the physical and mechanical properties of the soil. Using numerical methods, calculations were carried out to determine the effect of the tangential tractive force on the slipping of a wheeled traction vehicle with a different layout of the running system. The dependences of the amount of slipping on the tangential thrust force are determined. It has been found that with an increase in the traction force, the slipping increases, however, the intensity of growth of a half-tracked propulsor compared to a wheeled propulsor is much lower.

Speed-made-good: Mobility map generation for wheeled vehicles on soft terrain

The Nepean Wheeled Vehicle Performance Model (NWVPM) software has been in use for decades as a tool for engineers in industry and governmental agencies to predict the performance of off-road wheeled vehicles. It is based on the Bekker-Wong wheel-terrain interaction model which takes into account both the normal pressure and shear stress distributions at the wheel-terrain interface and uses the Bekker-Wong terrain parameters to characterize the terrain behavior. Using terrain and vehicle parameters as inputs, NWVPM computes various traction indicators such as drawbar pull, tractive effort, sinkage, and external motion resistance as functions of wheel slip by solving a set of equilibrium equations. This paper describes a novel method for predicting vehicle speed-made-good mobility maps and fuel consumption through an analytical approach using NWVPM. To evaluate the proposed method for predicting speed-made-good, a comparison is made with predictions obtained using Vortex, a commercial multibody dynamic simulation software that performs dynamic simulations of vehicles on soft terrain. In addition, a comparison of the capabilities of NWVPM and Vortex in predicting off-road vehicle performance over a range of terrains is presented and the results of the drawbar pull traction test from both software are compared with experimental data.

Stress distribution of a cylindrical sandwich sector with FG-CNT core and piezoelectric face sheets subjected to low-velocity impact

A new theoretical solution based on Layerwise theory is presented to determine the stress distribution in a simply-supported cylindrical sandwich sector with a functionally graded carbon nanotube core and piezoelectric face sheets subjected to low-velocity impact. The spherical elastic ball hits the top face sheet of the sector at an initial velocity of 50 m/s. The classical non-adhesive elastic contact theory and Hunter's relationship were used to determine the normal contact pressure distribution in terms of time and distance of the contact location. Moreover, Hamilton's principle and Maxwell's static equation were used to obtain the nineteen equations of motion. The numerical code was written to solve these nonlinear equations and the stress components in each layer were calculated in terms of time. In addition, it was assumed that the out-of-shell displacement of the sector at each layer is a quadratic polynomial function of the radial component in addition to a function of the coordinate components within the shell. Due to this assumption, the normal out-of-shell strain is not only zero, or not even a constant, but it changes in the form of a linear function along with the thickness of each layer.

Study of yarn properties and displacement deviation of acceleration points based on the novel drafting system

Drafting process plays an important role in spinning systems as it is closely linked with yarn qualities. Therefore, a novel drafting system (NDS) is applied in short staple spinning, which shows innovations in the friction field and the floating zone. This article compared the traditional drafting system (TDS) and novel drafting device by spinning four kinds of yarns (in partI). The experimental results demonstrate that NDS produces yarns with better properties with regard to the yarn evenness, imperfections and strength compared to TDS, indicating the varietal adaptability of the novel drafting device. Besides, a comparative analysis of the displacement deviations of acceleration points produced by NDS was performed in terms of the different fibers and varied tracing fiber lengths (in partII). The differences in displacement distributions between polyester and cotton fibers were investigated, showing that even under the same normal pressure distribution, different internal friction fields of fibers lead to different displacement distributions for acceleration points. The displacement distributions of different tracing fiber lengths embedded in the roving reveal that the longer the fibers, the more concentrated the acceleration points.

Using Homemade Pressure Device to Improve Plantar Pressure—A Case Study on the Patient with Lower Limb Lymphedema

Feet play a very important and indispensable role in people’s lives. Patients with lymphedema often suffer from collapsed (or even deformed) foot arches as a result of lower extremity edema. This result will change the normal pressure distribution on the soles of their feet, which will affect their mobility and physical health. When the patient does not know that the distribution of pressure on the sole of the foot has changed significantly, the deformation of the sole of the foot will become severe. In response to this problem, this research team hopes to use a set of self-made sensor insoles to help to understand the plantar pressure points in different situations or actions. The subject invited in this study was a patient with lower extremity edema. The entire study was carried out with the consent of the patient, the guidance of the physician and the approval of the Ethics Committee of National Taiwan University Hospital (No: 201805068 RINB, date: 18 June 2018). This study uses this self-made sensor insole to analyze the plantar pressure distribution of the patient before and after the operation of lower extremity edema. The results show that the operation can effectively improve the high foot pressure in the center and rear of the foot area during different sports (standing, walking and biking). This not only increases its stability when standing and walking, but also significantly and effectively improves its walking speed and step distance.

Numerical study on the ratcheting performance of rail flash butt welds in heavy haul operations

The ratcheting performance of a new R400HT rail flash butt weld was numerically evaluated under a typical heavy haul in-service condition. Due to varying mechanical properties across the rail weld, the weld region was divided into 23 zones in the numerical study. A dynamic finite element simulation of wheel–rail weld rolling contact was first carried out to obtain the total vertical contact force and its variation along rolling distance. Multiple quasi-static wheel–rail weld contact simulations were then performed by applying the total vertical contact force to determine the non-Hertzian contact pressure distribution when the wheel was located at different positions across the weld in the rolling direction. Based on each normal contact pressure distribution, the Haines and Ollerton's strip theory and Carter's theory were employed to estimate the corresponding longitudinal surface tangential traction distribution. Finally, a cyclic loading simulation was conducted to evaluate the ratcheting performance of the rail weld in terms of RCF initiation life by repeatedly translating these normal contact pressure and longitudinal tangential traction distributions on the running surface. The results reveal that the subzone with the lowest hardness in the softened zone has the shortest RCF initiation life among the weld region, followed by the region around the bond line. The parent rail provides the longest RCF initiation life and therefore has the best resistance to RCF. Additionally, the existence of the softened zone can shorten the RCF initiation life of the parent rail and the bond line section, particularly the regions located adjacent to the softened zone. The possible location of RCF initiation in the softened zone of the rail head can reach deeper than those in the parent rail and the region around the bond line. The results can help us understand the failure of flash butt rail welds in heavy haul operations and the numerical method can be applied to study different rail welds and rail welds under different conditions such as in a curved track.

Co-simulation of MATLAB and ANSYS for ultrasonic wire bonding process optimization

Ultrasonic wire bonding is a solid-state joining process, used in the electronics industry to form electrical connections, e.g. to connect electrical terminals within semiconductor modules. Many process parameters affect the bond strength, such like the bond normal force, ultrasonic power, wire material and bonding frequency. Today, process design, development, and optimization is most likely based on the knowledge of process engineers and is mainly performed by experimental testing. In this contribution, a newly developed simulation tool is presented, to reduce time and costs and efficiently determine optimized process parameter. Based on a co-simulation of MATLAB and ANSYS, the different physical phenomena of the wire bonding process are considered using finite element simulation for the complex plastic deformation of the wire and reduced order models for the transient dynamics of the transducer, wire, substrate and bond formation. The model parameters such as the coefficients of friction between bond tool and wire and between wire and substrate were determined for aluminium and copper wire in experiments with a test rig specially developed for the requirements of heavy wire bonding. To reduce simulation time, for the finite element simulation a restart analysis and high performance computing is utilized. Detailed analysis of the bond formation showed, that the normal pressure distribution in the contact between wire and substrate has high impact on bond formation and distribution of welded areas in the contact area.

Evolution of abnormal pressure in the Paleogene Es3 formation of the Huimin Depression, Bohai Bay Basin, China

The evolution of abnormal pressure is of importance for the analysis of hydrocarbon migration and accumulation processes. However, paleo-pressure reconstruction is still a challenge with great uncertainty. In this study, the PVT simulation method and homogenization temperature-salinity method were used for abnormal pressure evolution analysis in the Huimin Depression, which is characterized by a complex distribution of abnormal pressure, including overpressure, normal pressure and underpressure. The origins of the abnormal pressure conditions were also analyzed to examine the rationality and reliability of paleo-pressure reconstruction by basin modeling and quantitative calculation. The results revealed different evolutionary processes for the paleo-pressure in the Central Deep-Sag Zone (CDSZ) and the Northern Tectonic Uplift Belt (NTUB). In the CDSZ, the abnormal paleo-pressure exhibited a rising stage during the late Oligocene owing to disequilibrium compaction. From the early to middle Miocene, the paleo-pressure decreased to hydrostatic pressure because of the elastic rebound of rocks and temperature reduction. From the late Miocene to middle Pliocene, the paleo-pressure rose again because of the deposition and hydrocarbon generation. From the late Pliocene to the present, the paleo-pressure decreased again owing to the termination of hydrocarbon generation and secondary migration of hydrocarbons. In the NTUB, the paleo-pressure remained hydrostatic without disequilibrium compaction during the late Oligocene, followed by an intense reduction process due to rock elastic rebound and temperature reduction owing to strong tectonic uplift from the early to middle Miocene. From the late Miocene to middle Pliocene, the paleo-pressure rose because of the deposition and hydrocarbon injection from the CDSZ. From the late Pliocene to the present, the termination of hydrocarbon generation, weakening of hydrocarbon injection from the CDSZ, and the gas diffusion led to the decrease of pressure again in the NTUB. This study reveals that the paleo-pressure experienced two rising and two falling stages in the CDSZ and finally is characterized from normal pressure to overpressure. The paleo-pressure in the NTUB experienced one rising and two falling stages and is currently characterized by underpressure. This study provides a new approach for assessing the paleo-pressure evolution based on multiple analytical methods and further contributes to research on hydrocarbon-accumulating dynamics and hydrocarbon-migrating processes.

SIMULATION OF A SINGLE THIRD-BODY PARTICLE IN FRICTIONAL CONTACT

Contact of a single third-body particle between two plates is simulated using the Boundary Element Method. The particle is considered as deformable, and the Coulomb’s law of friction is assumed at the contact interface. The normal pressure distribution and tangential stress distribution in contact as well as the macroscopic force and force moment are calculated. Several movement modes are shown to be possible: rolling, rotation, or sticking during the loading. It is found that, differing from rigid particles, the state of particle may change during the loading. The particle may stick to the plates initially, but rotation may occur when the load becomes larger. Examples with the same and different coefficients of friction are presented to show kinematics of particle. The method can be further applied to simulation of multiple third-body particles.