Shear Parameters Research Articles

Stability analysis of a rotating asymmetric sandwich beam tapered along width and thickness subjected to pulsating axial load

The purpose of this research is to utilize computational method to study the stability of an asymmetric sandwich beam which has tapered-width as well as tapered-depth. The beam is also being subjected to rotary motion and axial load which is pulsating in nature. The governing equations of motionof the system is produced using the expanded Hamilton's notion, and also the boundary conditions are decided. The resultant equation of motion and associated boundary conditions are non-dimensionalized by using the extended Galerkin technique. To arrive at the Hill's equation for the analysis of static instability, the system of non-dimensionalized equations of motion must be solved. The parametric instability is determined by the Saito-Otomi criteria. The effect of various parameters such as taper parameters, shear parameter, rotational speed, hub radius, core-loss factor, and regions of parametric instability. Utilizing the necessary MATLAB algorithms, an investigation is conducted on a static bucking load and shown as a variety of graphs.

Effective selection of shears in variable lateral shearing holography.

The efficiency of reconstruction of complex wavefields in digital holography through shear interferometry has a direct correlation with the shears selected for image acquisition. Although studies to investigate the effect of shears have shown correlations between the selected shear set and the spatial and frequency contents of the reconstructed complex wavefield, to our best knowledge, not much information is available to provide a guide on how to select these shears optimally and what factors to be considered during this selection procedure. In this paper, we study the effect of shear parameters on the phase error through a series of simulations using a synthetic object wavefield and provide a range of shear parameters for optimal reconstruction. Further, we correlated the data by comparing the results with corresponding frequency information density maps.

Rotational shearing interferometer and wavefront angular derivative.

A shearing interferometer finds a derivative of the wavefront along the direction of the shear parameter. While the general belief was held that the sensitivity of the RSI increases with the shear angle, we find that just the opposite is true. We examine the range of validity of the derivative function for the rotationally shearing interferometer (RSI). We find that all terms of the aberration polynomial are multiplied by the sine of the half-shear angle multiplied by the order of polynomial, l. This factor may be expanded in series for small angles, or for angles close to π and π/2. We propose steps to evaluate the errors in the determination of the magnitude of individual aberrations. We apply findings to the planet-detection problem.

Clayey Soil Improvement with Polyethylene Terephthalate (PET) Waste

Population expansion and the development of technology have led to an increase in construction activities. In many cases, foundation grounds do not have a high enough bearing capacity and are not capable of ensuring the safe exploitation of the construction. A soil with poor mechanical characteristics must be improved using various methods, such as adding hydraulic binders (lime and cement), natural fibres, or more recently, plastic waste materials. This work aims to study the behaviour of plastic waste materials made from polyethylene terephthalate (PET) in soil improvement. Thus, the mechanical characteristics of a clay improved with shredded PET were studied. PET was added in relation to the dry mass of the clay, in percentages of 2%, 4% and 6%. The studied clay was collected from a construction site around Cluj-Napoca, Romania, from a depth of 1 ÷ 10 m. PET was provided by a local plastic waste repository. It comes from recycled water, beer and soda bottles and was cleaned using specific methods for cleaning and recycling plastic waste. PET was shredded into irregular shapes with sizes ranging from 3 mm to 12 mm and was randomly distributed in the test specimens. Compression and direct shear tests were carried out to study the compressibility and shear parameters of the improved soil (internal friction angle and cohesion). The experimental results showed an improvement in the mechanical characteristics of the clay even at a low PET addition of 2% and 4%. This method can contribute to solving two current problems of the modern world: reducing pollution by recycling plastic waste materials and using them to improve the mechanical characteristics of soil.

Effect of Slag on Shear Parameters of Collapsible Soils Compacted to Proctor Optimum

Effect of Slag on Shear Parameters of Collapsible Soils Compacted to Proctor Optimum

Clayshale Stabilization Using Liquid Calcium Carbonate to Increase Soil Shear Strength

Clayshale is a material that often causes various stability and bearing capacity problems in geotechnical engineering structures because it tends to weather and slake relatively quickly. This causes clayshale to be often not used during construction. Therefore, it is necessary to stabilize the clayshale. This study aims to determine the effect of adding variations in the levels of liquid calcium carbonate to the clayshale shear parameters. Physical and mechanical properties were tested on the original remoulded clayshale and samples with additional variations of 1M and 2M liquid CaCO3. Based on laboratory testing, the original clayshale samples had LL values of 37.9%, PL 14.6%, IP 23.3%, Gs 2.617, OMC 13.67%, γdry 1.762 gr/cm3. The addition of CaCO3 has been proven to increase the Gs value and reduce the plasticity index of the clayshale. After the Triaxial UU test, the clayshale sample in remoulded condition has a c value of 0.171 kg/cm2 and φ 8.33°. While the clayshale sample with 2M CaCO3 substitution as much as 80% OMC value which has been cured for three days increased the most optimum c and φ values, respectively 0.289 kg/cm2 and 11.13°. This shows that the addition of liquid CaCO3 can be used as a clayshale stabilization agent because it can increase the value of the shear parameter and improve the clayshale properties.

Ageing Effect On Shear Strength Of Mixed Kaolinite-Bentonite And Sand Clay Minerals

Ageing Effect On Shear Strength Of Mixed Kaolinite-Bentonite And Sand Clay Minerals

Characteristics of loess wind sorting and its structural mechanical significance

As loose sediment transported and deposited by wind, changes in the grain size of loess is the main source of changes in its macromechanical properties, mesostructural characteristics and microparticle effects. However, at present, there is almost no relevant research on the relationship between grain size and structural mechanics of wind-sorted loess, which significantly restricts the in-depth understanding of the mechanism and evolution of geological disasters and resulting engineering damage. In this paper, grain size optimization is performed by a wind sorting device developed in this laboratory to reveal the intrinsic mechanism associated with sorting, structural mechanics and particle interactions. The results show that the average grain size is positively correlated with the wind speed and negatively correlated with the transport distance. Further study finds that the grain size of aeolian loess consists of superimposed medium and fine particle fractions with good distribution sorting and coarse particle fractions with poor distribution sorting. Under the same conditions of water content and dry density, cohesion increases with increasing transport distance and wind speed. However, the internal friction angle first decreases and then slowly increases during the whole wind transport process. Fine particle content is the decisive factor for the change in shear parameters. Microscopic analysis shows that the contact mode, pore characteristics, azimuth of particles and variations in coarse, medium and fine ternary particle accumulations are closely related to the grain size distribution caused by wind sorting. The negative (loosening, wall, wedge) and positive (filling, adsorption) effects in these microstructures correspond to the structural characteristics of soil at different transport distances, and different structural characteristics correspond to different mechanical properties. This correspondence fully reveals the close relationship between the grain size characteristics produced by wind sorting and structural mechanics. This study helps to elucidate the relationship between grain size variation and mechanical characteristics of aeolian loess and provides theoretical references for relevant applications in the fields of geological and geotechnical engineering.

SANACIJA NESTABILNE KOSINE TOKOM IZGRADNJE VIJADUKTA UVAČ 4 NA DIONICI AUTOPUTU SMOKOVAC – MATEŠEVO U CRNOJ GORI

The rock slide that occurred in Montenegro in May 2019, damaged the support of the Uvač 4 highway viaduct under construction. The rock sliding happened in the mountain section, where the terrain is composed of tectonically crushed flysch sediments represented by sandstones, marlstones, and siltstones. Initially, deformations appeared on the ground with the formation of a 90m long scar, that after four weeks the movement of the L2O1 support of the Uvac 4 viaduct by more than 40 cm was registered. Additional geological investigation works were carried out and the sliding plane was registered with inclinometer measurements at a depth of 18m. Rehabilitation works included the formation of the new deep foundation supporting structures and securing the slope with cable anchors. The paper analyzed the values of flysch sediment shear parameters given in the rehabilitation project, as well as the adopted rock mass disturbance factor. The assessment is that the main reason for sliding terrain is caused by stress relief.

Species transport in a variable-density turbulent mixing layer considering stratified instability

Mixing of miscible fluids with differing densities in turbulent mixing layers is of great importance in chemical engineering. In addition to the effect of density ratio R between two fluids, stratified instability will introduce additional complexity to turbulent mixing of species. We investigate this issue by performing direct numerical simulations of a stratified mixing layer involving two miscible fluids with R = 1, 3, and 6. We find the stronger decay of turbulence in the high-density stream in comparison with the low-density counterpart, which is attributed to the decrease in the shear rate and the increase in stratified instability. Moreover, it shows the dynamical connections between stably stratified mixing layers and wall-bounded turbulent flows, which can be supported by the hairpin vortical structures, the vertical profile of integral shear parameter S* in the low-density side (S* ≈ 10–30), and an inverse wave-number scaling for streamwise energy spectrum of velocity fluctuation. The statistical analysis of the budget of the mixture fraction variance shows that the turbulent mixing of species is significantly suppressed in the high-density side while enhanced in the low-density one, as a result of the larger reduction of turbulent production, turbulent flux, and a smaller reduction of dissipation in the high-density side. Finally, we find that the dissipation rate of the structure function of the mixture fraction variance is about four times larger than that of mixture fraction variance. These results can provide support for large eddy simulation of stratified turbulent mixing of miscible fluids with differing densities.

Geoacoustic inversion of wide-angle reflection-coefficient data to estimate sediment shear properties

This paper considers Bayesian geoacoustic inversion of broadband, wide-angle reflection-coefficient data including shear parameters in the seabed model to investigate the ability to estimate these parameters as well as effects on the estimation of other geoacoustic parameters, particularly compressional-wave attenuation. The seabed parameterization is based on the viscous grain-shearing (VGS) sediment-acoustic model, including the grain-to-grain shear modulus as an unknown parameter. VGS sediment parameters are transformed to density and frequency-dependent compressional- and shear-wave speeds and attenuations. Data prediction involves spherical-wave reflection-coefficient calculations. Trans-dimensional inversion, which samples probabilistically over the number of layers in the seabed model, is applied to combine quantitative model selection with parameter/uncertainty estimation. The inversion is applied to reflection-coefficient data sets collected on the New England Mud Patch, and inversion results are compared to those obtained under the common assumption of negligible shear effects (i.e., inverting for a fluid sediment model).

Quantification of variability of shear and interface shear parameters of soils and its application to stability of veneer cover slopes

Quantification of variability of shear and interface shear parameters of soils and its application to stability of veneer cover slopes

Experimental characterization of AAC masonry in shear: Effect of block density, mortar, and test setup

AbstractThe paper discusses the results of an experimental program devoted to the characterization of AAC masonry in shear, by studying the effect of different key parameters: test setup, block density, and mortar type. As for ordinary masonry assemblages, shear parameters of AAC masonry can be determined from either shear tests on triplets or diagonal compression tests. However, the extension of these methodologies to AAC blocks with low densities is not so straightforward and highlights some critical issues. To evaluate the influence of block density (and block strength) on the shear parameters and on the observed modes of failure, masonry triplet and diagonal compression tests were performed for AAC blocks characterized by two different densities (300 and 480 kg/m3). Moreover, for the higher density class, tests were repeated by also varying the mortar type. Although most of Standard codes mainly relates the shear resistance of thin‐layer masonry to the block material, the obtained results highlight that also the mortar type and the surface treatment before mortar application may have a not negligible influence on the final behavior.

Nonlinear frequency analysis of porous Bi directional functionally graded beams utilizing reddy shear deformation theory

The nonlinear frequency response of bi-directional functionally graded porous beams experienced range of various end conditions is investigated in this work. The end conditions which are simply supported, clamped-simply supported, clamped-clamped, and clamped-free are taken by using the Von Karman geometric nonlinearity, Green's tensor and Reddy third-order shear deformation theory. A generalized differential quadrature technique (GDQM) accompanied by direct numerical iterance approach is proposed to solve equations. The findings are presented to aid in future research into the effects of various gradient indices, vibration amplitude ratios, porosity coefficients, shear and elastic substrate parameters, boundary conditions, and vibration frequencies on the bi-directional functionally graded beams. The outcomes of this research have practical applications and can be utilized to enhance the design of bi-directional beams. The results are also highly useful in anticipating and identifying potential causes of failure in these beams.

Aerodynamic characteristics of a streamlined box girder under shear flow considering oncoming turbulence

Non-synoptic winds, such as typhoons and downbursts, are frequently characterized by shear flow associated with turbulence, which affects the aerodynamic performance of long-span bridges. To reveal the aerodynamic characteristics of streamlined box girders under non-synoptic winds, multi-fan wind tunnel (MFWT) tests were used to investigate the aerodynamic effect around a streamlined box girder considering the action of shear flow with different velocity gradients, turbulence intensities, and integral scales. In the MFWT tests, the high shear rate and large turbulence intensity were observed to magnify the mean wind pressure coefficient, whereas the variation in the turbulence integral scale had a slight effect on the mean wind pressure coefficient distribution. An increase in the shear rate was observed to be beneficial in reducing the drag and moment coefficients, as well as in increasing the lift coefficient. The empirical aerodynamic prediction relationships revealed that the influence of turbulence intensity on the aerodynamic coefficient is non-linear, whereas that of the turbulence integral scale and shear rate on the aerodynamic coefficient is linear. Additionally, the large eddy simulation (LES) method was used to study the vortex-shedding behaviors and aerodynamic spectrum characteristics of the streamlined box girder under shear flow. The LES results showed that larger shear parameters amplify the amplitudes of high-frequency aerodynamic forces. The vortex frequently begins from the low-velocity side of the streamlined box girder, which induces a suction effect on the low-velocity side that is greater than that on the high-velocity side.

Variation Coefficient of Metal Yield Strength in New and Long-Used Building Structures

Introduction. Non-destructive methods are most often used to assess the condition of the metal structure. Dangerous stress is determined by the value of the yield strength. This approach has weaknesses. This is, firstly, the probabilistic nature of the methodology (the minimum value of the indicator obtained during laboratory tests is entered into the regulatory and technical documentation). Secondly, the limitations on the number of samples should be overcome. Thirdly, the different duration of operation causes a significant difference in the mechanical characteristics of the metal, which to a certain extent complicates the long-term prediction of the condition of the structure. The presented work is designed to solve these problems within the framework of the study of new and long-operated facilities in the Rostov region. The scientific research objective is to analyze fatigue changes and determine possible degradation of the metal.Materials and Methods. The mechanical characteristics of the material under study were reliably described by the Weibull distribution law through the shear parameter (the minimum possible value of the characteristic) and the shape parameter (magnitude dispersion). For scientific research, the indentation method based on a modified Rockwell hardness estimation method was used as part of the work. A conical indenter was embedded in the surface, then the reaction of the metal was analyzed. To implement the method, an analog-to-digital converter and a laptop were used. For correlation analysis, intermediate characteristics were taken: depth, maximum and minimum velocities, maximum and minimum acceleration of cone insertion. A correlation was established with the mechanical characteristics determined by standard tensile and hardness tests of the metal.Results. Objects with zero and long-term operation were studied. The measurements were carried out in a warehouse, production site, stadium, bridge, Palace of Sports and on a power line support. From the group of new and used structures, one was selected for a detailed fixation of the values of yield strength. So, before the start of operation, the condition of three metal trusses of the warehouse was analyzed. It was established that the lowest value of the yield strength here was 240 MPa, the maximum was 345 MPa. On the power transmission line poles, which have been in operation for 43 years, the lowest recorded value of the yield strength was 235 MPa, the highest was 384 MPa. For each of the six structures, the minimum and average distribution of the metal yield strength values was given, and the coefficients of variation of this indicator were given. The recorded values were summarized in the form of a table. The average values for all new and used designs were calculated. Graphically presented data illustrate the growth of the coefficients of variation of the yield strength with increasing service life.Discussion and Conclusion. A comparative analysis of the obtained values of the yield strength of building structures of approximately the same strength class suggests that the influence of operating time can both increase and decrease the studied indicator. At the same time, long-term operation is a factor that increases the average value of the coefficient of variation. To monitor the strength capabilities of the structure, it is advisable to use a non-destructive method, selectively monitoring the mechanical characteristics of the elements before and during operation.

Is Accurate Lumen Segmentation More Important than Outlet Boundary Condition in Image-Based Blood Flow Simulations for Intracranial Aneurysms?

PurposeImage-based blood flow simulations are increasingly used to investigate the hemodynamics in intracranial aneurysms (IAs). However, a strong variability in segmentation approaches as well as the absence of individualized boundary conditions (BCs) influence the quality of these simulation results leading to imprecision and decreased reliability. This study aims to analyze these influences on relevant hemodynamic parameters within IAs.MethodsAs a follow-up study of an international multiple aneurysms challenge, the segmentation results of five IAs differing in size and location were investigated. Specifically, five possible outlet BCs were considered in each of the IAs. These are comprised of the zero-pressure condition (BC1), a flow distribution based on Murray’s law with the exponents n = 2 (BC2) and n = 3 (BC3) as well as two advanced flow-splitting models considering the real vessels by including circular cross sections (BC4) or anatomical cross sections (BC5), respectively. In total, 120 time-dependent blood flow simulations were analyzed qualitatively and quantitatively, focusing on five representative intra-aneurysmal flow and five shear parameters such as vorticity and wall shear stress.ResultsThe outlet BC variation revealed substantial differences. Higher shear stresses (up to Δ9.69 Pa), intrasaccular velocities (up to Δ0.15 m/s) and vorticities (up to Δ629.22 1/s) were detected when advanced flow-splitting was applied compared to the widely used zero-pressure BC. The tendency of outlets BCs to over- or underestimate hemodynamic parameters is consistent across different segmentations of a single aneurysm model. Segmentation-induced variability reaches Δ19.58 Pa, Δ0.42 m/s and Δ957.27 1/s, respectively. Excluding low fidelity segmentations, however, (a) reduces the deviation drastically (>43%) and (b) leads to a lower impact of the outlet BC on hemodynamic predictions.ConclusionWith a more realistic lumen segmentation, the influence of the BC on the resulting hemodynamics is decreased. A realistic lumen segmentation can be ensured, e.g., by using high-resolved 2D images. Furthermore, the selection of an advanced outflow-splitting model is advised and the use of a zero-pressure BC and BC based on Murray’s law with exponent n = 3 should be avoided.

The role of suspended extracellular polymeric substance (EPS) on equilibrium flocculation of clay minerals in high salinity water

Biophysical cohesive mud, consisting of clay minerals and extracellular polymeric substance (EPS), plays significant role in determining sediments, nutrients and pollutants transport in estuarine and coastal systems. Series of laboratory jar experiments have been conducted aiming at filling the gap of knowledge regarding how biological cohesive EPS affects equilibrium flocculation of EPS-mineral mixtures. Four types of common clay (chlorite, kaolinite, illite and montmorillonite) were chosen due to their abundance in estuarine mud and distinct crystal chemistry and structures. Turbulent shear throughout all the experimental runs were constantly provided at a mean shear parameter of G ≈ 15 s−1 being equivalent to high tidal influenced estuarine turbulent environment. The results reveal that adding EPS increases the equilibrium floc size evidently. The pure mineral flocs show unimodal equilibrium floc size distribution (eFSD) with single peak located at microfloc range (<200 μm) while the EPS-mineral flocs show bimodal eFSD with a secondary peak located in macroflocs range (>200 μm) mostly. Moreover, EPS largely reduces the effective density in EPS-mineral flocs by 1∼2 magnitude. Most importantly, the terminal settling velocity of flocs shows size-dominated in uniform mineral floc cases but density-dominated in EPS-mineral mixture floc cases especially in macroflocs. To model a full floc size or settling velocity distributions in natural environments, furtherly quantification of EPS functions within the large-sized non-fractal mixture floc individually becomes a necessity.

Geophysical surveys in the Kashmir valley (J&K Himalayas) part I: Estimation of dynamic parameters for soils and investigation of the deep basin structure

A combined set of multichannel analysis of surface waves (MASW) and single-station microtremor horizontal-to-vertical spectral ratio (MHVSR) testing was performed at over 190 sites within the complete Kashmir Basin, mainly concentrated within the Greater Srinagar region. The aim was to establish the dynamic parameters of the main geomorphological units, especially the sedimentary deposits (Alluvial and Karewa) in the valley through widespread geophysical testing. Shear wave velocity (VS) and frequency parameters were estimated for each of the sites. Multiple impedance contrasts in the HVSR curves were found within the sedimentary deposits indicating a number of stratigraphic layers which were then correlated with the geology of the region. Further, forward modelling routine was utilised to extend the VS profile to deeper depths, to determine the first-order estimate bedrock depth and establish the basin structure which remains largely unexplored till now. Lastly, geological cross-sections were constructed using these results from the geophysical tests.

Cumulative effect of Shearing parameters and Ramp angle on Hole surface quality in Ti6Al4V by Helical milling strategy

Hole creation is a common contour in drilling and milling. However, drilling big holes in Ti6Al4V is difficult. It is due to the thermally increased metallurgical behavior of Ti6Al4V, which mortifies drill bits and degrades hole quality. To solve this issue, the current research investigates Helical milling through Computer Aided Tool Path as a viable option for Hole production by functionally managing shearing parameters. This approach drives the process parameters helically at a certain Ramp angle to achieve improved surface quality in the Hole. The analysis of variance reveals that the Cutting Speed and Feed/tooth affect the Circularity of the Hole. Furthermore, Axial DOC and Ramp angle significantly impactHole surface texture. The cumulative impact of Cutting Speed at 60 m/min, Feed/tooth at 0.06 mm, and Axial Depth of Cut at 0.6 mm applied at a Ramp angle of 1.50 through theHelical milling tool path under Hybrid nano Flood lubrication catch the outstanding Hole Quality.