Surface Breaking Research Articles

Comparative Evaluation of Mechanical Properties and Wear Ability of Five CAD/CAM Dental Blocks.

This study compares the mechanical properties and wear ability of five CAD/CAM (computer-aided design/computer-aided manufacturing) millable dental blocks. All the discs, including Amber Mill Hybrid, Vita Enamic, Katana Avencia, Lava Ultimate, and Amber Mill, were cut in dimensions of 1.2 mm in thickness and 12 mm in diameter, polished to a machined surface, and immersed in distilled water for seven days. Vickers hardness was measured and the indentations were observed using microscope. The discs were brushed under a 150 g load. Mean surface roughness (Ra) and topography were determined after 100,000 cycles. Finally the biaxial flexure strength of the discs was measured and the broken surfaces were observed using scanning electron microscopy (SEM). The data was subjected to Weibull analysis. All data were analyzed by one-way analysis (ANOVA). The results of Vickers hardness are shown as: Amber Mill > Vita Enamic > Amber Mill Hybrid > Lava Ultimate > Katana Avencia. Katana Avencia showed the highest volume percentage reduction and the roughest surface after toothbrushing. The biaxial flexural strength is shown as: Amber Mill > Katana Avencia > Lava Ultimate > Amber Mill Hybrid > Vita Enamic. All the tested materials exhibited varying degrees of mass loss and surface roughness. The properties of the composite materials are related to the filler content, filler volume, and polymerization methods.

Characterisation of small defects using miniaturised EMAT system

Many surface breaking defects, such as those caused by thermal fatigue or stress corrosion, have finite lateral dimensions. However, much of the research considers significantly larger simulated defects. This paper considers defects with mm-dimensions, and presents a method for characterisation of their length and depth. This is done using non-contact ultrasonic techniques, including a pair of electromagnetic acoustic transducers (EMATs) with significantly reduced size compared to standard industrial EMATs. Defects with dimensions of 1–11 mm length and 0.5–2 mm depth are measured. All information is obtained from a single raster scan of a sample, considering transmission and enhancement of Rayleigh waves, and introducing the defect cross-section. The lateral size resolution for the scan steps chosen is ± 1 mm, and depth resolution is ± 0.5 mm. The method, being non-contact, is also demonstrated on a sample with a 110 μm thick coating.

An SDE model for deterioration of rock surfaces

A stochastic differential equation (SDE) is derived and examined for approximately modeling the breaking down of rock surfaces through random processes. The rock surfaces include, for example, surfaces of historical monuments, gravestones, or natural rock formations. Rock surfaces break down through wear, weathering, and erosion. During weathering, rocks are worn away and fractured into smaller pieces while in erosion, the rock pieces are transported through actions, for example, of air, water, and gravity. In the mathematical model developed in the present investigation, it is assumed that environmental actions cause particles or pieces of a rock to gradually break off with erosion occurring simultaneously, that is, the rock pieces are transported away immediately after separation.

Properties of Unsaturated Polyester Composite Filled Activated Zeolite: The Effect of Filler Addition and Compression

The mechanical and physical properties of polyester composites filled with activated zeolites as fillers were investigated. Zeolite is an alumina silicate mineral that has cavity structures. The ability of the cavity structure can be maximized by activation using hydrochloric acid (HCl) 2 M. To achieve this goal, the zeolite was activated and proved it by performing morphological analysis using Scanning Electron Microscope (SEM) to see the surface structure. The aim of this study is to determine the effect of the activated zeolites content and hot press compression on the tensile and water absorption properties of polyester composites. The best tensile properties were found in ratio of unsaturated polyester with zeolite 70:30 (w:w) at a pressure of 125 Psi with a tensile strength of 38.51 MPa. SEM characterization showed a more rough breaking surface, that is in the ratio of polyester with zeolite 60:40 (w:w) at 75 Psi pressure because of the lack wetting between the matrix and activated zeolite. The water absorption of composite has increased as the addition of activated zeolite.

Imaging and Sizing of Surface Defects Using Synthetic Aperture Focusing of Laser-generated Surface Waves

The synthetic aperture focusing technique (SAFT) can be easily adapted to laser ultrasonic testing and can improve the signal-to-noise ratio (SNR) of laser ultrasonic images, to enhance defect detectability. In this study, the imaging and sizing of surface defects were carried out when SAFT was adopted for laser-generated surface waves. Six different surface breaking notches were made on an aluminum plate and were visualized using a laser ultrasonic scanning system consisting of a pulsed laser for ultrasonic generation and a laser interferometer for ultrasonic reception. B-scan images and SAFT-processed images for the six different notches were compared, which highlighted the advantages of the SAFT post-processing compared to B-scan imaging. A methodology to size the defects in SAFT-processed images was also proposed. The methodology utilizes the linear relationship between the suitable threshold decibel value, which determines the exact defect length with the use of an amplitude-drop method, along with the SNR of the defect echo in the SAFT-processed images. The experimental results demonstrate that the estimated defect lengths are similar to actual defect lengths, which showing that the proposed methodology can be effectively used for sizing of surface defects in SAFT-processed images.

Synthesis of zinc oxide-alumina nanocables for detection of 3-hydroxy-2-butanone biomarker

We report zinc oxide (core) coated with alumina (shell) single-shelled nanocables (ZnO@Al2O3 NCBs) for detection of 3-hydroxy-2-butanone (3H-2B) biomarker, which was prepared via aluminum-anodic-oxide (AAO) template confined electrodeposition, chemical etching and leaving thin AAO-channel wall with broken surface. In the core/shell nanostructure, the outer Al2O3 layer protects ZnO from interference gases, while the pores allow the target gas to react with the oxygen specie on the surface of ZnO. For as-built ZnO@Al2O3 NCBs sensors, the detection limit is as low as 1 ppm, and the response value to 50 ppm 3H-2B is 37.2 at 300 °C. Moreover, the ZnO@Al2O3 NCBs show excellent selectivity and cyclic stability. Our ZnO@Al2O3 NCBs sensors in future monitoring Listeria monocytogenes.

Degradation Behavior In Vitro of Carbon Nanotubes (CNTs)/Poly(lactic acid) (PLA) Composite Suture.

Poly(lactic acid) (PLA) suture can be absorbed by the human body, and so have wide applications in modern surgery operations. The degradation period of PLA suture is expected to meet with the healing time of different types of wounds. In order to control the degradation period of the PLA suture, the carbon nanotubes (CNTs) were composited with PLA suture, and the degradation experiment in vitro was performed on sutures. The structure and properties of sutures during degradation, such as surface morphology, breaking strength, elongation, mass and chemical structure, were tracked and analyzed. The results indicated that the degradation brought about surface defects and resulted in 13.5 weeks for the strength valid time of the original PLA suture. By contrast, the strength valid time of the CNTs/PLA suture was increased to 26.6 weeks. Whilst the toughness of both the pure PLA and CNTs/PLA sutures decreased rapidly and almost disappeared after 3 to 4 weeks of degradation. The mass loss demonstrated that the time required for complete degradation of the two sutures was obviously different, the pure PLA suture 49 weeks, while CNTs/PLA sutures 63 to 73 weeks. The research proved that CNTs delayed PLA degradation and prolonged its strength valid time in degradation.

Structural Analysis of Thin Ni-P Layers

The deposition mechanism by autocatalytic reduction method is a chemical one, which does not lead to structures as shown in the Ni-P balance diagram. In the experiments of the present work, Ni-P layers were made deposited on thin steel strip with low carbon content. By optical microscopy and scanning electron microscopy by (SEM) it was analyzed the appearance and surface morphology of the deposited layers depending on the content of phosphorus and working parameters (temperature, pH, stirring speed). The layer structure was analyzed in the cross section and on the break surface. The analysis results show that thin coatings of Ni-P have a surface topography that follows faithfully the steel support. Depending on the content of phosphorus, on the layer surface of low phosphorus content, spherical particles of different sizes can be seen while high and average phosphorus content coatings feature a smooth surface with nanometer-sized grains. Analysis of the cut-off /break section of the Ni-P layer structure, show a more or less porous structure depending on the stirring speed and pH level.

Failure analysis of the fracture surface of the crankshaft of a vehicle

The purpose of this study was to determine the cause of a fracture in the crankshaft of a 1000 cc gasoline engine. On the broken surface, it could be seen that the cracks started from the direction of the oil hole. A visual examination revealed that there were beach marks on the surface of the fracture, which is usually common in fatigue failure due to a dynamic load. From the test for the chemical composition, it was found that the material was classified as alloy steel. The Rockwell-based material hardness values were different. The highest hardness value of 102.2 HRB was on the outer shell portion of the crankshaft on the x and y axes at points 1 and 14. Finally, it was concluded that the reason for the fracture in the crankshaft was fatigue failure, the material hardness that did not match that of the standard, as well as the initial crack contained within the radius of crank pin number 1.

Oxygen (3P) atom recombination on a Pyrex surface in an O2 plasma

The recombination of O (3P) atoms on the surface of a Pyrex tube containing a DC glow discharge in pure O2 was studied over a wide range of pressure (0.2–10 Torr) and discharge current (10–40 mA) for two fixed surface temperatures (+50 °C and +5 °C). The recombination probability, γ, was deduced from the observed atom loss rate (dominated by surface recombination) determined by time-resolved optical emission actinometry in partially-modulated (amplitude ∼15%–17%) discharges. The value of γ increased with discharge current at all pressures studied. As a function of pressure it passes through a minimum at ∼0.75 Torr. At pressures above this minimum γ is well-correlated with the gas temperature, Tg, (determined from the rotational structure of the O2 (b1Σg+, v = 0) → O2(X3Σg−, v = 0) emission spectrum) which increases with pressure and current. The temperature of the atoms incident at the surface was deduced from a model, calibrated by measurements of the spatially-averaged gas temperature and validated by radial temperature profile measurements. The value of γ follows an Arrhenius law depending on the incident atom temperature, with an activation energy in the range 0.13–0.16 eV. At the higher surface temperature the activation energy is the same, but the pre-exponential factor is smaller. Under conditions where the O flux to the surface is low γ falls below this Arrhenius law. These results are well explained by an Eley–Rideal (ER) mechanism with incident O atoms recombining with both chemisorbed and more weakly bonded physisorbed atoms on the surface, with the kinetic energy of the incident atoms providing the energy to overcome the activation energy barrier. A phenomenological ER model is proposed that explains both the decrease in recombination probability with surface temperature as well as the deviations from the Arrhenius law when the O flux is low. At pressures below 0.75 Torr γ increases significantly, and also increases strongly with the discharge current. We attribute this effect to incident ions and fast neutrals arriving with sufficient energy to clean or chemically modify the surface, generating new adsorption sites. Discharge modeling confirms that at pressures below ∼0.3 Torr a noticeable fraction of the ions arriving at the surface have adequate kinetic energy to break surface chemical bonds (>3–5 eV).

A mathematical model for analyzing the ground deformation due to a creeping movement across a strike slip fault

A long, surface breaking, strike slip fault inclined to the vertical is taken to be situated in a linearly viscoelastic half space of Maxwell type representing the lithosphere–asthenosphere system. Tectonic forces due to mantle convection and other related phenomena are supposed to be acting on the system. Under the action of these forces stresses accumulate in the region and fault undergoes a creeping movement when the accumulated stress exceeds the frictional and cohesive forces across the fault. In this paper the creep velocity is supposed to be decelerating in nature. A numerical technique based on finite difference scheme with discontinuity has been developed to solve the related boundary value problem numerically. The resulting scheme is solved with the help of suitable MATLAB code and the nature of stress, strain in the region is shown graphically.

Evaluation of short active faults reflected from distributed minor surface breaks found at recent inland large earthquakes including the 2016 Kumamoto earthquake

Evaluation of short active faults reflected from distributed minor surface breaks found at recent inland large earthquakes including the 2016 Kumamoto earthquake

Scaling of Drag Coefficients Under Five Tropical Cyclones

AbstractThe drag coefficient, often used to parameterize the surface wind stress τ, beneath tropical cyclones (TCs) is a critical but poorly known factor controlling TC intensity. Here, τ is estimated using current measurements taken by 12 Electromagnetic Autonomous Profiling Explorer floats beneath the forward half of five TCs. Combining estimates of τ and aircraft measurements of winds U10, the downwind drag coefficient and the angle ϕ clockwise orientation from U10 to τ are computed. At |U10| = 25–40 m/s, and ϕ vary over (0.8–3.1) × 10−3 and −15–40°, respectively. A new nondimensional parameter “effective wind duration,” a function of |U10|, storm translation speed, and positions in TCs, predicts to within 25%. The largest and smallest ϕ occur at high winds, in the forward right quadrant of fast‐moving storms. These dependences are explained by variations in surface wave age and breaking under different wave forcing regimes.

Adsorption and dissociation of H2O molecule on the doped monolayer MoS2 with B/Si

Adsorption and dissociation of H2O on monolayer MoS2 surface doped with B/Si explored by first principle calculations coupled with climb image nudged elastic band method. The impurity B/Si atoms are more likely to occupy sulfur atom lattice positions with lower formation energies, which results in the breaking of surface chemically inertness of the MoS2 (001) plane. Free H2O molecules can be adsorbed on doped surfaces with lower adsorption energies, and form chemical bonds between oxygen and impurity atoms. Adsorbed H2O can be separated into OH radical and hydrogen adatom with a lower dissociation energy barrier on these doped systems (including impurity B/Si single doped, B and Si co-doped). Furthermore, the adsorbed OH radical can be further dissociated into oxygen and hydrogen adatoms on the surface of B and Si co-doped MoS2. Our theoretical study suggests that substrate of monolayer MoS2 doped with impurity B, Si may be a potential alternative choice for hydrogen evolution reaction.

Small‐scale observation on the effects of burrowing activities of ants on soil hydraulic processes

SummaryAnts alter soil structure when making their nests and the fresh soil aggregates brought to the surface become available for erosion. However, the effects of burrowing activities of ants on soil hydrological processes are unclear. In this study, the effects of Tetramorium caespitum, Messor aciculatus and Camponotus japonicus nests on the preferential flow and soil surface hydrologic processes at a small scale were assessed on the Loess Plateau. Soil dyeing and rainfall simulation experiments were conducted to quantify the effects of ants' nests on runoff and water infiltration on slopes. The diameters of nest entrances for T. caespitum, M. aciculatus and C. japonicus were 0.19, 0.33 and 0.56 cm, respectively. The nests of M. aciculatus and C. japonicus promoted water infiltration, resulted in large soil water contents and decreased surface runoff. The turret‐like mounds around the nest entrances made by T. caespitum prevented the formation of soil preferential flow. The depths of dyeing in the soil with M. aciculatus and C. japonicus nests were 32.6 and 49.2 cm, respectively, which were significantly (P < 0.05) deeper than those in the soil with T. caespitum nests (10.0 cm) and no nest (10.3 cm). The unstable soil aggregates made by ants on the soil surface break down easily and encourage the loss of soil sediment. The results show that increasing the ant colonies, especially those with larger bodies, could be considered a strategy to increase water infiltration and soil water content in semiarid areas. In the meantime, the sediment loss cannot be neglected.Highlights This study evaluated the effects of hypogeal ants on soil erosion. The turret‐like mounds of T. caespitum prevent the formation of preferential flow. Ants with larger bodies made bigger nest entrances and resulted in more infiltration. The burrowing activities of ants exacerbate soil erosion.

Defect-Controlled Nucleation and Orientation of WSe2 on hBN: A Route to Single-Crystal Epitaxial Monolayers.

A defect-controlled approach for the nucleation and epitaxial growth of WSe2 on hBN is demonstrated. The WSe2 domains exhibit a preferred orientation of over 95%, leading to a reduced density of inversion domain boundaries (IDBs) upon coalescence. First-principles calculations and experimental studies as a function of growth conditions and substrate pretreatment confirm that WSe2 nucleation density and orientation are controlled by the hBN surface defect density rather than thermodynamic factors. Detailed transmission electron microscopy analysis provides support for the role of single-atom vacancies on the hBN surface that trap W atoms and break surface symmetry leading to a reduced formation energy for one orientation of WSe2 domains. Through careful control of nucleation and extended lateral growth time, fully coalesced WSe2 monolayer films on hBN were achieved. Low-temperature photoluminescence (PL) measurements and transport measurements of back-gated field-effect transistor devices fabricated on WSe2/hBN films show improved optical and electrical properties compared to films grown on sapphire under similar conditions. Our results reveal an important nucleation mechanism for the epitaxial growth of van der Waals heterostructures and demonstrate hBN as a superior substrate for single-crystal transition-metal dichalcogenide (TMD) films, resulting in a reduced density of IDBs and improved properties. The results motivate further efforts focused on the development of single crystal hBN substrates and epilayers for synthesis of wafer-scale single crystal TMD films.

Effects of Different Mechanized Organic Fertilization Methods on the Soil Physicochemical Properties of Corn Field

In this study, corn continuous cropping soil was sampled and five mechanical tillage and fertilization methods were compared, so as to explore the influences of different organic fertilization methods on soil physicochemical properties, and to provide reference for finding the best continuous soil fertilization methods and solving soil fertility decline in the future. The soil and corn samples were collected and measured to analyze soil physical and chemical properties and corn yield. The results showed that the mechanical spreading of decayed cow dung improved soil structure enhanced soil water retention and increased soil organic matter content. Straw mulching and breaking surface application can increase effective soil porosity, improve soil surface characteristics, improve soil ventilation and water permeability, which is expected to play an important role in improving soil surface compaction. The deep application of straw into the field can improve the soil viscosity and high fertility, and can be used in good sandy soil. Particle organic fertilization can effectively improve soil water permeability without causing loose soil texture, improve soil water permeability and water retention, and increase pH value of acidic soil.

Book review: Gail Jefferson, with Paul Drew and Jörg R. Bergmann (eds), Repairing the Broken Surface of Talk: Managing Problems in Speaking, Hearing, and Understanding in Conversation

Book review: Gail Jefferson, with Paul Drew and Jörg R. Bergmann (eds), <i>Repairing the Broken Surface of Talk: Managing Problems in Speaking, Hearing, and Understanding in Conversation</i>

Numerical analysis of water exit for a sphere with constant velocity using the lattice Boltzmann method

In this paper, the three-dimensional water exit of a sphere with different vertical velocities is investigated numerically using the lattice Boltzmann method (LBM). In this method, the liquid-gas two-phase flow is simplified as a single-phase free surface flow. To capture the free surface, a mass tracking algorithm is incorporated into the LBM. The gravity as a body force is introduced in the form of calculating the equilibrium distribution with an altered velocity, while the surface tension is neglected. Besides, the employed bounce-back boundary conditions are used for a moving sphere. What’s more, the Wall-Adapting Local Eddy (WALE) viscosity model is employed to capture the turbulent structures of the flow and stabilize the simulation. The accuracy of the numerical results is demonstrated through comparisons with the previous numerical and experimental results in the literature. The results show that the spike height is significantly influenced under the Froude number (Fr) below 4.12 and slightly affected under the Fr varying from 4.12 to 8.24. After the sphere exits water totally, the evolution of the free surface waterfall can be described as two phases and becomes more intense with the Froude number increasing. The non-uniform distribution of velocity results in the breaking of the free surface after the sphere completely exits the water. Moreover, the Reynolds number greatly affects the wake dynamics and hydrodynamics acting on the sphere when it moves beneath the water surface.

Comparative evaluation of the mechanical properties of CAD/CAM dental blocks.

This study compares the mechanical properties of commercially available CAD/CAM (Computer-Aided Design/Computer-Aided Manufacturing) millable dental blocks including Vita Enamic, Lava Ultimate, and MAZIC Duro. All the discs were cut in dimension of 1.2mm in thickness and 12mm in diameter, ground up to #1200 Sic papers and polished. The biaxial flexure strength of the ceramic discs was measured after thermocycling treatment and the broken surfaces were observed using scanning electron microscopy (SEM). The discs were brushed using a toothbrush testing machine under a 150g load. Surface roughness and morphology were determined after toothbrushing cycles. Finally, the friction and wear behavior of the materials against an opposing tooth were studied using a reciprocating pin-on-plate test configuration. The vertical loss of dental cusp was measured, and the surface image was examined using field emission scanning electron microscopy (FE-SEM). The biaxial flexural strength data were subjected to Weibull analysis. To compare the significance between the groups, all data were analyzed by one-way analysis (ANOVA). The biaxial flexural strength of the Lava Ultimate and MAZIC Duro materials is significantly higher than that of Vita Enamic. In addition, Lava Ultimate and MAZIC Duro exhibited significantly smoother surfaces than that of Vita Enamic after toothbrushing. Lava Ultimate and MAZIC Duro also showed less wear to the opposing tooth than that of Vita Enamic. In addition, Lava Ultimate possesses more suitable mechanical properties than the Vita Enamic and Mazic Duro for use in oral clinical prosthesis.