Serrated Surfaces Research Articles

Determination of Slip Factor between CNC-Cut Serrated Surfaces of S355J2 Grade Steel Plates

Structural joint configurations realized with serrated steel surfaces have started to be used in the construction fields to assemble the primary and the secondary structural members of civil engineering structures. The main advantages of these joint configurations rely on their flexibility to accommodate construction tolerances and their slip-resistant load-bearing mechanism against dynamic loading conditions. Therefore, it is important to reliably establish the characteristic value of the friction coefficient or in other words the slip factor between the serrated steel surfaces to design reliable slip-resistant connections. In this study, the characteristic slip factor between the CNC-cut serrated surfaces prepared from S355J2 grade steel plates is determined to investigate the impact of the CNC-cutting procedure on the slip-resistant load-bearing behaviour of steel-to-steel interfaces. Five experimental tests were performed according to EN1090-2, Annex G. The results are presented as the load-slip curves, variation of the bolt pre-tension load level, nominal and actual slip factors for the tested configuration of the CNC-cut serrated steel-to-steel interface.

Growth of the Serrated GaN Nanowire and its Photoelectrochemical Application

Introducing polyhedral facets into a high surface-to-volume nanowire structure (i.e., serrate-shaped or screw thread-like nanowire) is an effective way for boosting the photoelectrochemical (PEC) activity. However, fabricating such nanowires with serrated surfaces remains a challenge because it usually involves many complex processes, thus limiting mass activity. Here, we demonstrate a strategy for natural growth of the serrated GaN nanowires on a LiGaO2 substrate by using an Au catalyst-assisted vapor-liquid-solid (VLS) method. The specific GaN nanowire grew through an atypical growth mechanism due to the partial deformation of the Au catalyst. The serrated GaN nanowire exhibited a higher photocurrent density of 0.391 mA cm−2 at 1.23 V versus RHE, which was approximately 2.3 times that of the GaN film (0.157 mA cm−2). The high stability of the photoresponse and photocurrent of the serrated nanowire was verified in a wide angle-dependent illumination. This work opens a new way for strengthening the PEC performance of the GaN-based photoanodes by introducing serrate-shaped surfaces on the GaN nanowires.

Non-equilibrium evolution and characteristics of the serrated microchannel hydrogen knudsen compressor

The hydrogen Knudsen compressor has great potential to transport hydrogen and provide the required pressure in MEMS and microfluidic systems. The microchannel composed of cold and hot serrated surfaces is beneficial to the temperature control of the multistage Knudsen compressor. In the present study, a serrated hydrogen Knudsen compressor model is established initially, and the non-equilibrium evolution is numerically studied by using the method of N–S equations with the slip boundary. The key factors affecting the non-equilibrium evolution are comprehensively analyzed. The flow behaviors and performance of the serrated hydrogen Knudsen compressor in different times are studied. It is found that the main factors affecting the non-equilibrium evolution are the thermal expansion flow, thermal transpiration flow, and Poiseuille flow. Meanwhile, the serrated structure affects the local flow in the serrated microchannel at different times. Under the interaction of the thermal transpiration flow and the Poiseuille flow, the pressure difference between the two containers first increases rapidly and then decreases slowly, and finally approaches 1886 Pa. The research reveals the flow mechanisms of the hydrogen Knudsen compressor in the non-equilibrium evolution, which provides theoretical support for the safety and reliability of the hydrogen Knudsen compressor.

Experimental Investigation on Shear Failure Mechanism of Rock Mass with Intermittent Joints

There are a large number of discontinuous weak planes distributed in the natural rock mass, which makes the sliding failure of rock mass along the intermittent structural plane very complex. To investigate the shear failure mechanism of rock mass with intermittent joints and study the influence of different joint heights on the shear failure mode of the rock mass, direct shear tests were carried out by presetting a series of jointed rock specimens with different undulating heights. During the shear loading, digital image correlation (DIC) technology was employed to monitor the surface strain field of the specimens in real time. The results show that the fluctuation height has a significant effect on the evolution of shear strain. With the increase of shear load, the maximum shear strain of the jointed specimens with different undulating heights first increases slowly and then increases rapidly. When the undulating height is 5 mm, the failure of the specimen is dominated by the rock sliding along prefabricated joints. When the undulating height is larger than 10 mm, the shear fracture of the rock becomes dominant. With the increase of the undulating height, more penetrating cracks perpendicular to the preexisting joints appear between the serrated surfaces, and the shear fracture phenomenon is more obvious.

Development of a lumbosacral intervertebral cage prototype for dogs

ABSTRACT: Several surgical procedures aim to decompress and/or stabilize the lumbosacral (LS) joint of dogs; however, the lumbar interbody fusion technique, by using a cage combined with a bone graft, is the most indicated and used in human medicine. No specific implant is available for application to the canine lumbosacral joint. Thus, this study measured lumbosacral discs in large dogs, determined whether a human cage model could fit the dogs’ L7-S1 intervertebral space, and developed a LS cage prototype for dogs. Ten cadaveric lumbosacral spines from adult dog weighing 20-35kg were used. The dogs had died for reasons unrelated to this study. The vertebral body dimensions and the L7-S1 intervertebral space occupied by the intervertebral disc were measured by lateral and ventrodorsal radiographs and by computed tomography in the dorsal, sagittal, and transverse views. Measurements were also taken of the anatomical specimens in the sagittal and transverse planes. After measuring the intervertebral discs, the following mean measures were obtained for L7-S1 discs: height 12.23mm, dorsal thickness 3.3mm, central thickness 4mm, ventral thickness 5.5mm, and width 24.74mm. The human lumbar cage models from brands LDR, Baumer Orthopedics, Stryker, Synthes, and Vertebral Technologies, Inc. and cervical stabilization cages from the brands B-Braun and Stryker were evaluated and were found to be unsuitable for large dogs. Cervical human cages had measurements similar to those found in this study; however, due to their quadrangular shape, the possibility of being introduced surgically through the surgical accesses available for the articulation between L7-S1 in dogs without injuring the cauda equina or the L7 root is small. A cage model was then developed using 3D modelling software. It was designed for insertion via dorsal laminectomy in the lateral portions of the intervertebral space. To avoid cauda equina lesion, the implant model was developed to be placed laterally to the midline. The cage surface is serrated to prevent using the locking screw to fix it, thus avoiding further injury to nerve structures. The serrated surfaces are also designed to avoid cage migration and promote stability. The prototype allows graft placement in the surrounding intervertebral space, which is fundamental for fusion through integration between the cage and the endplates as well as for bone growth between and around the cage. It was also considered studies on humans showing that the lateral regions of the endplates support a more considerable load. Biomechanical and in vivo studies on the developed model are necessary to evaluate the actual degree of distraction, mobility and the long-term rate of fusion between L7 and S1 and its possible impact on the adjacent motor units, combined or not with dorsal fixation techniques.

Design of a combined cartilage graft crusher, morselizer and holder for use in rhinoplasty.

A combined cartilage holder and crusher is described that allows the surgeon to hold, crush, morselize, and suture a single piece or stack of cartilage graft without letting it slip. The customized slit-shaped jaws allow adequate room for the suture needle, while the serrated surfaces hold the cartilage firmly. The use of this instrument is advocated primarily in rhinoplasty for manipulating and suturing a small cartilage graft or a stack of grafts. The use of this instrument may be extended to aesthetic or reconstructive cases where cartilage grafts need to be sutured or shaped, as in eyelid, ear, and nipple reconstruction.

Concentration effect of TEMPO-oxidized nanofibrillated cellulose aqueous suspensions on the flow instabilities and small-angle X-ray scattering structural characterization

The rheological behavior of 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-oxidized nanofibrillated cellulose (NFC) suspensions at different concentrations were examined using Couette with smooth and serrated surfaces and vane-in-cup geometries. A slippage against the walls of rheometer rotor or/and stator (wall-slip) as well as flow localization within a specific volume of the sample (shear banding) took place. These phenomena were visualized using a technique based on introduction of titanium dioxide pigment into the specific volume of NFC suspension and monitoring its deformation. The flow instabilities appeared more pronounced with an increase of the NFC concentration. It was shown that the use of serrated geometry is necessary to compete with the wall-slip but is not sufficient to prevent it completely. Serrated Couette was found to be the most appropriate geometry (among the tested) to measure the rheological properties of NFC suspensions. Small-angle X-ray scattering was used to provide a supplementary information about the structural organization of NFC suspensions. The statistical average diameter of 4.8 nm was determined from the scattering data for the NFC swollen in water.

Stability Of ZnO Nanorods Coated On The Channel Wall Under Continuous Flow Conditions

The damage given to the ZnO nanorod coating immobilized at the bottom of a rectangular channel by water flow is assessed in this work. The experiments were conducted in complete darkness to determine the inherent stability of the nanorod coating without the interfering effect of UV radiation. The quality and morphology of the nanorod arrays before and after use were determined by x-ray diffraction, scanning electron microscopy; rod breakage, by dynamic light scattering; and the extent of erosion, by concentration and weight measurements. The effect of pH of the flowing water in the range 4pH10, and the effect of the volumetric flow rate in the range, 3.333 cm 3 /s are investigated in this work as parameters. ZnO erosion reaches a low- level plateau in the pH range of 6pH10. Within this range, water velocity and alignment of the nanorods control the extent of dissolution. Dissolution of ZnO nanorods essentially takes place on the polar (0001)-Zn plane of ZnO, resulting in the formation of serrated surfaces. Furthermore, inclined rods joining at the top surface is subjected to further dissolution through pit formation originating at the junction interface, and extending outwards. ZnO nanorod arrays could be used as a photocatalyst in the photocatalytic water treatment processes, where the dissolution from nanorods is in the range of 2.0−2.5 wt% after 24 h of operation under a flow rate of 3.30 cm 3 /s (≈12 L/h), well under the requirements of World Health Organization. Copyright © 2014 VBRI press.

Sodium Tripolyphosphate and Polyphosphate as Dispersing Agents for Alumina Suspensions: Rheological Characterization

In the present work, the influence of addition of some dispersing agents employed for maximizing the solid loading of alumina concentrated suspensions has been investigated. Two commercially available deflocculants were used: a sodium tripolyphosphate and a sodium polyphosphate. Rheological tests were carried out at 25°C under continuous flow conditions by using the rate-controlled coaxial cylinder viscometer Rotovisko-Haake 20, system M5-osc., measuring device SV2P with serrated surfaces. The application of rheological techniques permitted the evaluation of the efficiency and the optimum dosage of the dispersing agents employed upon the alumina slips examined, that is, the critical concentration at which the maximum reduction in viscosity is detected.

Flow Behavior of Fresh Very High Strength Portland Cement Pastes

Flow behavior of fresh very high strength portland cement pastes prepared at various water/cement ratios was studied by using a rate-controlled coaxial cylinder viscometer (Rotovisko-Haake 20, system M5-osc., measuring device MV2P with serrated surfaces). The tests were performed under continuous flow conditions. Experimental shear stress and shear rate data were fitted very satisfactorily with various models, one of which has already been proposed by the authors. Excellent results were achieved also by applying the Quemada equation. In addition, the influence of two different commercial superplasticizing agents (Concretan RX and Ergomix 1000, the former based on polycyclic copolymers with modified structures, carrying hydroxylated side chains, and the latter on a modified polyacrylic resin) was studied with the aim of determining their optimum dosage and verifying the effectiveness by comparing rheological results with those obtained in a previous work on an ordinary portland cement. The use of superplasticizers modified rheological behavior of the pastes; however, no value of optimum dosage was found for any additive, but only a superplasticizer concentration range within which pastes presented very low values of viscosity. Moreover, both superplasticizers showed a greater effectiveness when added to HSPC pastes rather then the OPC ones formulated with the same water/cement ratio.

Rheological Properties of Very High-Strength Portland Cement Pastes: Influence of Very Effective Superplasticizers

The influence of the addition of very effective superplasticizers, that are commercially available, employed for maximising the solid loading of very high-strength Portland cement pastes, has been investigated. Cement pastes were prepared from deionized water and a commercially manufactured Portland cement (Ultracem 52.5 R). Cement and water were mixed with a vane stirrer according to ASTM Standard C305. The 0.38 to 0.44 water/cement ratio range was investigated. Three commercial superplasticizing agents produced by Ruredil S.p.a. were used. They are based on a melamine resin (Fluiment 33 M), on a modified lignosulphonate (Concretan 200 L), and on a modified polyacrylate (Ergomix 1000). Rheological tests were performed at 25°C by using the rate controlled coaxial cylinder viscometer Rotovisko-Haake 20, system M5-osc., measuring device MV2P with serrated surfaces. The tests were carried out under continuous flow conditions. The results of this study were compared with those obtained in a previous article for an ordinary Portland cement paste.

Wall-slip effects in SnAgCu solder pastes used in electronics assembly applications

Solder paste is the most important strategic bonding material used in the assembly of surface mount components in electronics manufacturing. As the trend towards miniaturisation of electronic products continues, there is an increasing demand for better understanding of the flow and deformation that is, the rheological behaviour of solder paste formulations. Wall slip plays an important role in characterising the flow behaviour of solder paste materials. The problem of wall slip arises due to the various attractive and repulsive forces acting between the solder particles and the walls of the measuring geometry. These interactions could lead to the presence of a thin solvent layer adjacent to the wall, which gives rise to slippage. In rheological measurements, slip effects can generally be avoided by using roughened surfaces for measuring geometries. In this paper, a novel technique is developed to study the effect of wall slip in the rheological measurements of lead-free solder paste. The viscosity and oscillatory data obtained for three different solder paste samples (from measuring geometries of different surface roughness) have been analysed and compared. In viscosity measurements, slip effects were dominant at low shear rates and the use of serrated surfaces was found to be quite effective in minimizing slip effects. Oscillatory measurements were also affected by roughening the surfaces of measuring geometries.

Effects of Surface Roughening on Asperity Flattening

A series of experiments have been conducted using aluminum strips, which manifest a strong tendency toward roughening in forming processes, to investigate the evolvement of surface roughness and its resistance to flattening. The strips are stretched to specific bulk strains and are then compressed by a smooth glass at various pressures. It is found that except for very high bulk strain, the free surface on the transverse specimen roughens more seriously and irregularly than the longitudinal one due to the fierce rotations of grains, which make the grains parallel to the straining direction and eventually mutate the topography into an isotropic one. As the roughened surface is compressed, the transverse specimen may roughen further in the case of large bulk strain. According to the finite element method (FEM) analysis using serrated surfaces, the sharper asperity undergoes more serious straining on its peak and basically such a strain increment is not affected by the degree of flattening. The ability to resist flattening, defined as the “asperity hardness,” varies with asperity angle as well as the enhanced shear strength on the asperity tip, rather than the substrate. A new quantitative description of the asperity hardness is suggested, and the new calculated contact area ratios are in good agreement with the experiments except for very high pressure where additional mechanics such as adiabatic recrystallization might happen. The concept of the additional hardening on asperity peaks can be employed to refine the prediction of asperity contact in the analysis of metal forming.

Study of fatigue crack incubation and propagation mechanisms in a HPDC AM60B magnesium alloy

Abstract The micro-mechanisms of fatigue crack nucleation and subsequent propagation in a commercial high-pressure die-cast (HPDC) AM60B alloy were studied. It was found that the majority of fatigue cracks were initiated due to the compressive residual stresses at the locations of large casting pores underneath the machined surfaces, not close to the cast skins, as expected. The propagation of the fatigue cracks depends on the alloy's microstructure, as well as the casting initiated defects during the manufacturing process. Close to the initiation sites, in a location of high local porosity, the cracks grow along the interdendritic regions. On the other hand, in the absence of the weak microstructual paths, the cracks propagate directly through the dendrite cells. Numerous randomly oriented serrated surfaces near the regions farther away from the initiation sites indicate a mixed interdendritic–transdendritic propagation mode. The final fracture zone is characterized by a high level of porosity and dimples surrounding the second phase particles. The resulting conclusions provide a summary of the parameters influencing crack propagation in the alloy.

Rheological Properties of Alumina Slurries: Effect of Deflocculant Addition

In the present work the influence of the addition of some dispersing agents employed for maximizing the solid loading of alumina concentrated suspensions has been investigated. Three commercial deflocculants were used: a sodium salt of a benzenedisulfonic acid (Tiron), a sodium polyphosphate, and an aurintricarboxylic acid, triammonium salt (Aluminon). Rheological tests were carried out at 25°C under continuous flow conditions by using the rate-controlled coaxial cylinder viscometer Rotovisko-Haake 20, system M5-osc., measuring device SV2P with serrated surfaces. The application of rheological techniques permitted evaluating the efficiency and optimum dosage of the dispersing agents employed on the alumina slips examined, i.e., the critical concentration at which the maximum reduction in viscosity is detected.

Structural Study of In<sub>2</sub>O<sub>3</sub> Structures Grown by the Metalorganic Chemical Vapor Deposition

We have synthesized the film-like and rod-like structures of indium oxide (In2O3) by metalorganic chemical vapor deposition (MOCVD) method. The structural morphology of the deposits changed from the film to the arrays of 1-dimensional (1-D) materials with increasing the deposition temperature. The 1-D materials with the serrated surfaces prepared at 350°C possessed a crystalline cubic structure and had preferentially grown along the [111] direction.

Unusual occipital condyles of the skull: an osteological study with clinical implications

The occipital condyles of the skull articulate with the superior articular facets of the atlas vertebra and form an important junction between the cranium and the vertebral column. The morphological features of occipital condyles are relevant in biomechanical, anatomical and clinical studies. To describe the anatomical profile of unusual occipital condyles detected in a bone specimen. The present osteological study provides a detailed morphological description of unusual occipital condyles showing uneven and serrated surfaces and also displaying longitudinal and transverse grooves on the left and right sides respectively. The case study also discusses the clinical importance of such anomalies. Precise anatomical knowledge of the occipital condyles is important for any craniovertebral operative procedures such as resection of the occipital condyles.

Estimating depletion layer thickness in colloidal systems: Correlation with oil-in-water emulsion composition

In emulsions, slippage due to wall depletion effects is well known in rheological investigations. This effect can be overcome by using geometries with serrated surfaces. However, we present here an easily practicable calculation that allows the slip data to be manipulated in order to determine the depletion layer thickness when data from both smooth and serrated surfaces is obtained. When studies are performed over a range of concentrations we show that there is a strong correlation between depletion layer thickness and emulsion composition. The experimental system used as the test case for the method was the ternary system triton X-100/water/tetradecane. Calculations were performed using data obtained for oil-in-water emulsions with the parallel plate geometry for a range of different gap sizes. The depletion layer thickness (≤1 μm) decreased on increasing the amount of dispersed phase, until at a sufficiently high concentration of dispersed phase ( φ max = 0.73) slippage was no longer observed. The maximum depletion layer thickness was found to be a quadratic function of the relative volume fraction of the dispersed phase. The data coincide with those reported in the literature for a latex particle suspension if plotted using the same representation. Moreover, the proportionality constant was found to be of the order of the radius of the largest droplets in the dispersion. It is these droplets, which are chiefly responsible for the three-dimensional arrangement of the dispersed phase. This leads to the conclusion that the thickness of the depletion layer is controlled by the volume fraction and the size of the dispersed droplets.

An MOCVD route to In2O3 one-dimensional materials with novel morphologies

We have successfully synthesized one-dimensional (1-D ) indium oxide (In2O3) arrays by the metalorganic chemical vapor deposition (MOCVD) method. We have characterized the products by means of X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), and transmission electron microscopy (TEM). The SEM images showed that the 1-D materials with serrated surfaces had cross-sections in the shape of an acute triangle. The XRD and TEM studies revealed that the 1-D materials possessed a single-crystalline cubic structure and that the growth occurred preferentially along the [111] direction.

Rheological Behavior of Calcite Slurries: Effect of Deflocculant Addition

ABSTRACT In the present work, the influence of the addition of some dispersing agents employed for maximizing the solid loading of calcium carbonate concentrated suspensions was investigated. Three commercial deflocculants were used:a sodium salt of a benzenedisulfonic acid (Tiron), a sodium polyphosphate, and an aurintricarboxylic acid, triammonium salt (Aluminon). Calcium carbonate aqueous suspensions were prepared at various solid volume fractions (0.270 to 0.382). Rheological tests were carried out at 25°C by using the rate-controlled coaxial cylinder viscometer Rotovisko-Haake 20, system M5-oscillatory, measuring device SV2P with serrated surfaces. The tests were performed under both continuous and oscillatory flow conditions. The application of rheological techniques permitted highly accurate evaluation of the optimum dosage of the deflocculants, i.e., the critical concentration at which the maximum reduction in viscosity is detected. Generally, Aluminon and sodium polyphosphate behaved as the best dispersing agents for the calcite suspensions studied, i.e., they showed their optimum dosage at a concentration lower than that of Tiron and provided low viscosity values for the entire concentration range explored.