Average Shear Stress Values Research Articles

Effect of the sharp profile geometry ong the cutting forces of tire recycling tools

Objective: Study the impact of blade profile geometry on cutting forces during tire recycling, focusing on how variations in the shape and design of tools affect the efficiency and quality of the cut, as well as the tools' lifespan. Methodology: Through the construction and testing of three blade geometries, based on a prior numerical study and made from DF2 and 1.2363 steel, experiments were conducted on a Universal Testing Machine with samples of used tire rubber. Results: It was demonstrated that the hollow profile blade significantly reduces energy consumption and improves cutting performance compared to the 30° straight V profile blade, for both rubber-only samples and those with reinforcing textile fibers. Additionally, the study presented the evaluation of shear stresses using a 90° blade, indicating an average shear stress value of 8.67 MPa. Conclusion: This finding suggests that the appropriate selection of blade geometry can significantly contribute to the efficiency of the tire recycling process, offering important economic and environmental implications.

The Effect of Welding Current on Shear Test and Microstructure TIG Brazing of Cemented Carbide and Steel

The need for good welding results as knowledge in the process of welding different types of materials is needed in the community, and this res- earch is to determine the effect of variations in welding currents of different types of metals on cemented carbide and carbon steel using the TIG brazing method. For the base metal, YG6 cemented carbide and SS400 carbon steel with CuSi filler metal are used. The sample method is made by connecting different types of materials with the welding process using variations in current of 60 ampere; 80 ampere, and 100 ampere. The mechanical properties of this material connection were tested using the Hydraulic Universal Testing Machine, while for the microstructure examination, a microstructure test tool with a magnification of 100 x was used. The results of the tests revealed that the highest average compressive strength was 22.2 kN at a welding current variation of 60 A, and the lowest average value was 10.2 kN at a welding current variation of 100 A. Furthermore, for the average value of shear stress, the highest value at 60 A variation is 148 N/mm2 and the lowes t value is at 100 A welding current, which is 67 N/mm2. The res ults of testing the microstructure of the connection area s how that the higher the current strength, the more enriched the Cu content and will affect the size and spacing of Si grains.

Electric-field frictional effects in confined zwitterionic molecules.

We theoretically explore the effect of a transverse electric field on the frictional response of a bi-layer of packed zwitterionic molecules. The dipole-moment reorientation promoted by the electric field can lead to either stick-slip or smooth sliding dynamics, with average shear stress values varying over a wide range. A structure-property relation is revealed by investigating the array of molecules and their mutual orientation and interlocking. Moreover, the thermal friction enhancement previously observed in these molecules is shown to be suppressed by the electric field, recovering the expected thermolubricity at large-enough fields. The same holds for other basic tribological quantities, such as the external load, which can influence friction in opposite ways depending on the strength of the applied electric field. Our findings open a route for the reversible control of friction forces via electric polarization of the sliding surface.

Pembuatan dan pengujian spot welding menggunakan travo daur ulang

Spot welding is very much needed for the home industry, but the expensive welding price and large welding power make spot welding less efficient for small industries. Therefore, spot welding with small power and easy-to-carry design is needed. Spot welding design process is carried out in stages, namely planning, explaining component functions, and testing variations in the welding time used. The method used is experimental by making and testing. The specimen used is a type 304 stainless steel plate with a thickness of 0.8 mm. selected stainless steel type 304 with a thickness of 0.8 mm using a lap joint, with variations in welding time of 10, 15, and 20 seconds, using a current of 550 Ampere. The test carried out is a shear test with the AWS D8.9-97 test standard, with the aim of this study to determine the optimization of spot welding equipment using a recycled transformer on the test results. From the results of the research that has been carried out, it can be concluded that in variations of electric current and welding time, the highest average shear stress value is found at 550 A electric current by welding for 10 seconds the average shear stress is 1,060,164 (N/mm²) and the lowest average shear stress at an electric current of 550 A welding for 20 seconds the average shear stress is 564.578 (N/mm²).

Testing methods for shear strength of bond line between concrete and different types of engineered wood

This paper identified a reliable testing method for determining the shear strength of bond lines between concrete and engineered wood. The identification was carried out based on analytical derivations and experimental tests on concrete (compressive strength of 24.8 MPa) and engineered wood composite connections glued by two types of epoxy. Forty specimens were tested under two commonly used test setups, i.e. 20 double-shear tests on timber-concrete composite specimens with a bond length of 50 mm and another 20 compression-shear tests on specimens with a bond length of 300 mm. The result analysis showed that there was no significant statistical difference between the shear strength of the bond lines (around 2.3 MPa) as well as between the failure modes obtained (dominated by concrete failure), regardless of the considered bond lengths and adhesive types investigated. The analysis used a quasi-non-linear fracture mechanics model, considering the boundary conditions of the tests. The analytical model revealed that the ultimate shear stress is approximately uniformly distributed both in the double-shear and in the compression-shear tests, so the spatially averaged shear stress value can approximate the critical shear stress of the bond line with sufficient accuracy. However, if the failure occurred in the wood or the strength of the concrete was higher, the shear stress distribution at ultimate load in the compression-shear tests with a bond length of 300 mm would not be uniform. The maximum shear stress value, which is significantly larger than the average one, occurred at the fixed (or supporting) end of the bond line. Even so, in the shear tests with a bond length of 50 mm, the average ultimate shear stress value was still close to the shear strength with a difference smaller than 5%. Hence, a bond length of 50 mm is recommended for determining the shear strength of a bond line between normal strength concrete and engineered wood when using a push-out shear test setup.

Computational modeling for prediction of the shear stress of three-dimensional isotropic and aligned fiber networks

Background and objectiveInterstitial flow (IF) is a creeping flow through the interstitial space of the extracellular matrix (ECM). IF plays a key role in diverse biological functions, such as tissue homeostasis, cell function and behavior. Currently, most studies that have characterized IF have focused on the permeability of ECM or shear stress distribution on the cells, but less is known about the prediction of shear stress on the individual fibers or fiber networks despite its significance in the alignment of matrix fibers and cells observed in fibrotic or wound tissues. In this study, I developed a computational model to predict shear stress for different structured fibrous networks. MethodsTo generate isotropic models, a random growth algorithm and a second-order orientation tensor were employed. Then, a three-dimensional (3D) solid model was created using computer-aided design (CAD) software for the aligned models (i.e., parallel, perpendicular and cubic models). Subsequently, a tetrahedral unstructured mesh was generated and flow solutions were calculated by solving equations for mass and momentum conservation for all models. Through the flow solutions, I estimated permeability using Darcy's law. Average shear stress (ASS) on the fibers was calculated by averaging the wall shear stress of the fibers. By using nonlinear surface fitting of permeability, viscosity, velocity, porosity and ASS, I devised new computational models. ResultsOverall, the developed models showed that higher porosity induced higher permeability, as previous empirical and theoretical models have shown. For comparison of the permeability, the present computational models were matched well with previous models, which justify our computational approach. ASS tended to increase linearly with respect to inlet velocity and dynamic viscosity, whereas permeability was almost the same. Finally, the developed model nicely predicted the ASS values that had been directly estimated from computational fluid dynamics (CFD). ConclusionsThe present computational models will provide new tools for predicting accurate functional properties and designing fibrous porous materials, thereby significantly advancing tissue engineering.

Impact of Feed Spacer Filament Spacing on Mass Transport and Fouling Propensities of RO Membrane Surfaces

Material build-up on membrane surfaces is one of the vital challenges faced by Reverse Osmosis operations, leading to many operational and maintenance issues. To date, several modeling studies are dealt with flow behavior and concentration patterns for cross-flow membrane operations. However, the relative fouling propensities of top and bottom membrane surfaces are never addressed in any study for narrow channels filled with ladder-type spacers. In the present work, fluid flow patterns through different spacer configurations are visualized using ANSYS FLUENT by varying the dimensionless filament spacing, L (ratio of top or bottom filament spacing and channel height). Results clearly indicate that the average shear stress values at the top membrane surface are always higher (3–8 times) than that at the bottom membrane surface, but the mass transfer coefficient for the two walls yielded approximately similar average values having low to moderate filament spacings of L ≤ 3 (SP22 and SP33), indicating similar fouling propensities of membrane surfaces. Further increase in filament spacing with L ≥ 4 (SP44 and SP66), the average mass transfer coefficient for the top membrane indicated a sharp decline, suggesting high fouling propensity compared to bottom membrane which is not a desirable feature. Among the four spacer arrangements studied, SP44 (with L = 4) was found to be the optimal arrangement, yielding moderate pressure drop with nearly equal/higher area weighted values of mass transfer coefficient for the two walls and would lead to lower and equal fouling tendencies for top and bottom membrane surfaces, respectively.

3D reconstruction techniques of human coronary bifurcations for shear stress computations

BackgroundHeterogeneity in plaque composition in human coronary artery bifurcations is associated with blood flow induced shear stress. Shear stress is generally determined by combing 3D lumen data and computational fluid dynamics (CFD). We investigated two new procedures to generate 3D lumen reconstructions of coronary artery bifurcations for shear stress computations. MethodsWe imaged 10 patients with multislice computer tomography (MSCT) and intravascular ultrasound (IVUS). The 3D reconstruction of the main branch was based on the fusion of MSCT and IVUS. The proximal part of side branch was reconstructed using IVUS data or MSCT data, resulting in two different reconstructions of the bifurcation region. The distal part of the side branch was based on MSCT data alone. The reconstructed lumen was combined with CFD to determine the shear stress. Low and high shear stress regions were defined and shear stress patterns in the bifurcation regions were investigated. ResultsThe 3D coronary bifurcations were successfully generated with both reconstruction procedures. The geometrical features of the bifurcation region for the two reconstruction procedures did not reveal appreciable differences. The shear stress maps showed a qualitative agreement, and the low and high shear stress regions were similar in size and average shear stress values were identical. The low and high shear stress regions showed an overlap of approximately 75%. ConclusionReconstruction of the side branch with MSCT data alone is an adequate technique to study shear stress and wall thickness in the bifurcation region. The reconstruction procedure can be applied to further investigate the effect of shear stress on atherosclerosis in coronary bifurcations.

Method of analyzing and quantifying the performance of mixing sections

AbstractIn this article, the performance of three different mixing elements on color dispersion in high‐density polyethylene and linear low‐density polyethylene polymer stream during extrusion is studied. Two similarly designed Maddock mixers and a Stratablend II mixer are used as the last part of a general purpose single screw. Moreover, an inline melt camera is used for the quantification of mixing quality by visualization of grayscale of the color dispersion and thus mixing. The Stratablend II mixer produces the lowest and most uniform standard deviation. Both the Maddock mixers showed the same trend but higher values of standard deviation. All results are then compared with a full 3D finite element method simulation. Simulations clearly indicate that the Stratablend II mixer has the best mixing abilities and that these are mainly given by its unique design with high average value of shear stress. The role of elongational stress does not appear to have a high influence on mixing for these mixers. The results also suggest that the key factor for achieving better mixing is the frequency by which a large fraction of the material passes through the high shear stress regions of the mixer. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers

Wall shear stress as measured in vivo: consequences for the design of the arterial system

Based upon theory, wall shear stress (WSS), an important determinant of endothelial function and gene expression, has been assumed to be constant along the arterial tree and the same in a particular artery across species. In vivo measurements of WSS, however, have shown that these assumptions are far from valid. In this survey we will discuss the assessment of WSS in the arterial system in vivo and present the results obtained in large arteries and arterioles. In vivo WSS can be estimated from wall shear rate, as derived from non-invasively recorded velocity profiles, and whole blood viscosity in large arteries and plasma viscosity in arterioles, avoiding theoretical assumptions. In large arteries velocity profiles can be recorded by means of a specially designed ultrasound system and in arterioles via optical techniques using fluorescent flow velocity tracers. It is shown that in humans mean WSS is substantially higher in the carotid artery (1.1–1.3 Pa) than in the brachial (0.4–0.5 Pa) and femoral (0.3–0.5 Pa) arteries. Also in animals mean WSS varies substantially along the arterial tree. Mean WSS in arterioles varies between about 1.0 and 5.0 Pa in the various studies and is dependent on the site of measurement in these vessels. Across species mean WSS in a particular artery decreases linearly with body mass, e.g., in the infra-renal aorta from 8.8 Pa in mice to 0.5 Pa in humans. The observation that mean WSS is far from constant along the arterial tree implies that Murray’s cube law on flow-diameter relations cannot be applied to the whole arterial system. Because blood flow velocity is not constant along the arterial tree either, a square law also does not hold. The exponent in the power law likely varies along the arterial system, probably from 2 in large arteries near the heart to 3 in arterioles. The in vivo findings also imply that in in vitro studies no average shear stress value can be taken to study effects on endothelial cells derived from different vascular areas or from the same artery in different species. The cells have to be studied under the shear stress conditions they are exposed to in real life.

Study on the effects of spacer geometry in membrane feed channels using three-dimensional computational flow modeling

Three-dimensional computational fluid dynamics (CFD) study is carried out for spacer-obstructed feed channels of membrane elements using Finite Volume package FLUENT. The fluid flow behavior is studied by varying geometric parameters of diamond and parallel type spacers. The velocity profiles and hence the average shear stress values significantly depend on the parameters such as transverse filament spacing and filament thickness whereas the effect of axial filament spacing in altering the velocity profiles and shear rates is not that significant. The effect of spacer filament thickness is more pronounced on pressure drop as compared to the effect of spacing between the filaments. The local and average shear stress values also depend on the flow attack angle. When filament spacings and flow attack angles are small, the average shear stress values are high. The shear stress distribution is more uniform in diamond spacers when the flow attack angle is high and in parallel spacers when transverse filament thickness is small. The spacer dimensions can cause unsteadiness in flow that depends on the channel Reynolds number. The value of critical Reynolds number at which flow becomes unsteady can be as low as 75 when filament spacings and flow attack angles are small and it can be more than 200 for larger flow attack angles.