Crater Width Research Articles

Control of ablation morphology on Cu film with tailored femtosecond pulse trains

The ablation morphology of Cu film is investigated using tailored femtosecond pulse trains. The width, depth, and structure of ablation craters are systematically analyzed as the function of sub-pulse interval. Two distinct ablation sub-structures are observed. The gentle slope irradiated by low fluence emerges from the peripheral region of the ablation crater, and the steep slope formed in the central region is irradiated by high fluence. The ablation morphology can be controlled by manipulating the shaped pulse trains. We demonstrate that the ablation depth modulation is significant with the ablation width almost unchanged. By fitting the depth curves, we define a coefficient K to characterize the plasma shielding effect between sub-pulses with the increase in sub-pulse interval. For three fluences, the coefficient K using two kinds of pulse trains are extracted experimentally. The results reveal that the plasma shielding effect can be modulated by changing sub-pulse interval, and the corresponding physical interpretation is proposed.

Impact modeling for the Double Asteroid Redirection Test (DART) mission

We present results from numerical simulations of the DART impact using the CTH shock physics code with 2D homogenous asteroid models. A design of experiments approach was used to create a run matrix of 28 simulations varying 17 different material model inputs for the impactor and target. The resulting values of the momentum transfer efficiency factor β and the crater width and depth were analyzed to determine the relative sensitivity of each parameter for predicting the DART impact outcome. We found that β and crater width/depth ratio are primarily influenced by a small number of material model input parameters, a result which greatly reduces the parameter space required for more expensive 3D simulations.

Effects of diode laser setting for laryngeal surgery in a rabbit model.

To study the damaging effect of different diode laser settings on vocal folds 7 days after injury in a rabbit model. Twenty-one male New Zealand white rabbits were randomized into three groups with seven animals per group. A 980-nm diode laser was used to create a single spot injury in each vocal fold. Different modulation frequencies (10Hz versus 1000Hz) in pulsed mode, different powers (3W versus 5W), and distinct wave modes of radiation (pulsed versus continuous) were compared. The extent of the inflammatory infiltrate and ablation crater were greater when using 5-W optical power compared with 3W. The extent and depth of the inflammatory infiltrate, and the width and depth of the ablation crater were greater with continuous wave mode compared with pulsed mode. The density of collagen fibers only increased when using the laser in continuous wave mode. The use of the 980-nm diode laser with an output power of 5W produced an increased extent of thermal injury compared to an output power of 3W and, more importantly, using continuous rather than pulsed wave mode significantly increased the extent and depth of thermal injury in rabbit vocal folds.

Comparison of single droplet impact behaviors on the burning shallow/deep pool

Abstract Dynamics of single water droplet impinging on burning heptane surface were investigated experimentally in shallow/deep pool. The pool regimes were newly defined and a translation region was found in burning pools. At low Weber numbers, the crater-jet only occurs for shallow pools while the crater-secondary jet does for deep pools. The bubble was observed at high Weber numbers for both pools. Compared to Weber number, liquid depth has a significant effect on the number of jet (jet and secondary jet). Some characteristic parameters, such as maximum crater depth, width and jet height were analyzed as a function of impacted dimensionless depth (1.9–11.1) and Weber numbers (246–638). Maximum crater depth and width are mainly determined by liquid depth in shallow pools, while they significantly depend on Weber number and impact behavior in deep pools. Maximum jet height is highly related to liquid depth and temperature. Additionally, the damping effect of fire plume on droplet impact velocity was explored and theoretical correlation between droplet impact velocity and impact height was proposed.

Dynamic behavior of single droplet impacting on heptane pool with different depths

The paper presents dynamic behavior of single droplet impinging on the heptane pool with various impact Weber number and liquid depths. Liquid depth and Weber number have significant effects on the droplet impact behaviors. Three typical impact regimes, including penetration-secondary penetration/floating, crater-jet/crater-jet-secondary jet and bubble, can be observed in the impact process. The penetration occurs only for low Weber number. Especially, penetration-second penetration appears in a shallow pool for the dimensionless heptane depth of no more than 3.6, while penetration-floating does for the dimensionless heptane depth of no less than 5.4. With an increase in Weber number from 175 to 440, crater-jet appears in shallow pool while crater-jet-secondary jet appears in deep pool, and bubble begins to form as Weber number exceeds 564. Moreover, in order to quantitatively analyze the kinetic behavior, some key parameters were discussed in detail, such as maximum crater depth and width, jet height, bubble life time, loss rate of impact velocity, etc.

Effect of electrode polarity on fatigue life in EDM

In this study, high manganese steel specimens were machined with graphite electrode and various processing parameters by electro erosion method. It is a known fact that the craters generated by the EDM have a notch effect on the fatigue life. Therefore, Rz and Sm roughness parameters are calculated as the roughness maximum crater depth and width, respectively, and the theoretical fatigue life calculations are performed on the treated surfaces. In the processes, the tool polarization was also changed and the measured roughness values were higher in the positive polarity, so that the fatigue limit life was reduced in the calculations made with the area1/2 model. In EDM, when using a graphite electrode, in the case of reverse polarity machining, the surface roughness has an effect on increasing the fatigue life.

Water droplet impacting on burning or unburned liquid pool

A series of experiments was conducted on single water droplet impacting onto pool liquid with or without burning surface. Three typical liquid fuels were used: heptane, butanol and ethanol, which were separately burned in a square glass pool with various side lengths (50mm, 75mm, 100mm, 125mm and 150mm), respectively. The water droplet diameter was around 2.2mm and the falling height was fixed at 80cm. The impact processes were recorded using a high-speed digital camera at 2000 frames per second. The results show that the impact behaviors are obviously different between the cases of unburned and burning liquid pools. Although pool size has no evident effect on impacting behaviors compared to liquid fuel type both for unburned and burning pools, it influences the crater evolution for burning pool. In addition, the maximum crater width and depth are independent of pool size for unburned pool, while it decreases with the increase of pool size for burning pool. The impacted liquid properties including density, surface tension and viscosity have a significant effect on crater evolution. The crater evolution time is longer in unburned pool than that in burning pool, and the crater evolution time in ethanol pool is larger than those in the other two pools.

Underground parallel pipelines domino effect: An analysis based on pipeline crater models and historical accidents

This paper focuses on the analysis of the possibility of domino effect in underground parallel pipelines relying on historical accident data and pipeline crater models. An underground pipeline can be considered as safe following an accident with an adjacent gas or liquefied pipeline when it remains outside the ground crater generated. In order to prevent the domino effect in these cases, the design of parallel pipelines has to consider adequate pipeline separations based on the crater width, which is one of the widely used methods in engineering applications. The objective of this work is the analysis of underground petroleum product pipelines ruptures with the formation of a ground crater as well as the evaluation of possible domino effects in these cases. A detailed literature survey has been carried out to review existing crater models along with a historical analysis of past accidents. A FORTRAN code has been implemented to assess the performance of the Gasunie, the Batelle and the Advantica crater models. In addition to this, a novel Accident-Based crater model has been presented, which allows the prediction of the crater width as a function of the relevant design pipeline parameters as well as the soil density. Modifications have also been made to the Batelle and Accident-Based models in order to overcome the underestimation of the crater width. The calculated crater widths have been compared with real accident data and the performance evaluation showed that the proposed Accident-Based model has a better performance compared to other models studied in this work. The analysis of forty-eight past accidents indicated a major potential of underground parallel pipelines domino effect which is proven by two real cases taken from the literature. Relying on the investigated accidents, the crater width was smaller than or equal to 20 m in most cases indicating that the definition of underground pipeline separations at around 10 m would be sufficient to ensure a small probability of the domino effect.

Crater geometry and morphological changes on gold sheet during laser microdrilling

Fine polished and 4 N (99.99 %) pure gold is irradiated using Nd:YAG laser (1064 nm, 50 mJ, 10 Hz). Drilling is performed in air by increasing number of laser shots on the target surface. After each set of shots, the surface morphology and crater dimensions have been taken into account. SEM JEOL (JSM-7500F) and optical microscope (STM6-LM OLYMPUS Corporation) are used as characterization tools. It is revealed from SEM micrographs that heat conduction is non-uniform and more in the upward direction. Ripples, cones, and cone-like topography are observed. Droplets of micron size and nanoparticles have also been formed at 3000 number of laser shots where perforation occurs. Combining the investigations of SEM and optical microscope, it is observed that with the increase in laser shots, the crater width along horizontal increases and then decreases. It follows the Gaussian trend of variation. Crater width along vertical also increases and then decreases showing Gaussian trend of variation. Crater depth increases by increasing number of laser shots till perforation occur, chasing a linear growth. Heat-affected zone (HAZ) expands, exhibiting the Gaussian way of expansion with increase in laser shots.

Cratering of a particle bed by a subsonic turbulent jet: Effect of particle shape, size and density

The effect of particle properties on scour hole or crater formation, which occurs when a localized jet impinges on a bed of particles, is explored. Individual particle properties, such as particle density, size, and shape, are isolated and a parametric study is performed demonstrating the transient and steady crater growth for several particles. By keeping the particle diameter constant and changing the particle shape, this work shows that the effects of shape are significant. Uniform non-spherical (e.g. cylinders) and irregular frit shaped (e.g. crushed glass) particles are investigated. Non-spherical particles generally have higher friction, and the resulting decrease in recirculation rate of particles along the crater walls generally produces a narrower but deeper crater relative to spheres of the same size. A modification to the densimetric Froude number, which scales the steady crater depth to jet and particle properties is developed that accounts for particle shape. A new description of particle size called the erosion diameter is introduced, which is the average of the longest dimension a particle will align in a shear flow with its orthogonal, and results in the best scaling. The short-term crater depth grows faster for larger particles, which is counter to the long-term growth, and is explained by the early behavior being dominated by the number of particles that can be eroded. The transient crater depth growth is fit by an arctangent fitting function, which predicts the steady crater depth, and is compared to the logarithmic growth function that is generally used for early crater growth. For very large spherical particles, a high velocity is necessary for cratering and a newly identified particle–particle based cratering mechanism dominates. Additionally, cohesion reduces the crater depth and width and the steady crater depth does not scale with non-cohesive particles, but a further modification to the densimetric Froude number to account for cohesion is proposed.

Ablation experiment and threshold calculation of titanium alloy irradiated by ultra-fast pulse laser

The interaction between an ultra-fast pulse laser and a material's surface has become a research hotspot in recent years. Micromachining of titanium alloy with an ultra-fast pulse laser is a very important research direction, and it has very important theoretical significance and application value in investigating the ablation threshold of titanium alloy irradiated by ultra-fast pulse lasers. Irradiated by a picosecond pulse laser with wavelengths of 1064 nm and 532 nm, the surface morphology and feature sizes, including ablation crater width (i.e. diameter), ablation depth, ablation area, ablation volume, single pulse ablation rate, and so forth, of the titanium alloy were studied, and their ablation distributions were obtained. The experimental results show that titanium alloy irradiated by a picosecond pulse infrared laser with a 1064 nm wavelength has better ablation morphology than that of the green picosecond pulse laser with a 532 nm wavelength. The feature sizes are approximately linearly dependent on the laser pulse energy density at low energy density and the monotonic increase in laser pulse energy density. With the increase in energy density, the ablation feature sizes are increased. The rate of increase in the feature sizes slows down gradually once the energy density reaches a certain value, and gradually saturated trends occur at a relatively high energy density. Based on the linear relation between the laser pulse energy density and the crater area of the titanium alloy surface, and the Gaussian distribution of the laser intensity on the cross section, the ablation threshold of titanium alloy irradiated by an ultra-fast pulse laser was calculated to be about 0.109 J/cm2.

One-electron quantum ring of non-uniform thickness in magnetic field

We consider a model of a quantum ring in the form of a thin layer, whose thickness increases linearly between inner and outer radii. We show that in the structural adiabatic limit, when the quantum ring thickness is much smaller than its lateral dimension, the wave equation for the electron confined in such structure can be completely separated. We use analytical solutions found for this model as the base functions for analyzing the effect of the structural non-homogeneity on the electronic spectrum and the Aharonov–Bohm oscillations of the energy levels, in the framework of the exact diagonalization method we found that the pattern of the electron's possible pathways in its displacements generated by the external magnetic field, forms a quasi-one-dimensional region along a guideline marked by a set of highest points of the crater. Therefore, the Aharonov–Bohm oscillations of the energy levels in a crater-shaped quantum dot without non-uniformities are similar to those in 1D quantum ring independently on the crater width. We show that a slight non-uniformity produced by a single valley and single mountain supresses the oscillations of several lower levels due to the localization of the corresponding rotational states close to the mountain. Nevertheless, when the non-uniformity becomes substantial due to the presence of multiple valleys and mountains, the rotational electron motion and the Aharonov–Bohm oscillations generated by the external magnetic field are restored, owing to the electron tunneling through mountains. We consider that our model of crater-shaped structure would be applicable in the analysis of a variety of more complicated problems related to systems of few carriers confined in nanostructures with ring-like geometry, as a starting point in the framework of the diagonalization method.

Simulation on Material Removal during Reciprocating Traveling WEDM of Insulating Ceramics

With the double layer structure model, the material removal of insulating ceramics ZrO2 during the machining process by reciprocating traveling wire electrical discharge machining (WEDM) was simulated and analyzed. The influence of conductive layer (C and ZrC) to material removal volume and crater dimension was compared. And the effect of peak current, pulse duration and the movement speed of wire electrode on discharge craters were researched. The simulation shows that the conductive layer exist has much influence to the material removal volume and crater length and width, but has less influence to crater depth during electrical discharge. The simulation for the effect of discharge parameter tells that, with the boiling removal form hypothesis, the material removal volume during single discharge is increasing with the increment of peak current and pulse duration but decreasing with the raising of wire electrode movement speed. For the variation of peak current, the removal volume of ZrO2 is exceeding the removal volume of conductive layer when Ip is bigger than 24A. Meanwhile, for the variation of movement speed of wire electrode, the removal volume of conductive layer is more than that of ZrO2 when v is over 5m/s.

Discrete particle simulation of jet-induced cratering of a granular bed

Abstract Jet-induced catering in a granular bed is an interesting phenomenon observed in nature and in many industries. This paper presents a numerical study of this process by the combined approach of computational fluid dynamics (CFD) for gas phase and discrete element method (DEM) for solid phase. The applicability of the model is verified by comparing the numerical results with experimental measurements of crater depth and crater shape in the cratering regime of Diffusion Driven Flow. The sensitivity of numerical results to model parameters such as restitution coefficient, sliding friction coefficient and Young's modulus is also examined. Then, the effect of jet velocity is quantified, followed by a detailed analysis of flow characteristics and forces between particles, as well as between particles and fluid, to understand the underlying mechanisms. Based on the simulated results, two equations are respectively formulated to estimate the asymptotic crater depth and crater width.

Research on the Wear Characteristics and Wear Mechanisms of CrAlTiN Coated HSS Tools under Dry Cutting Conditions

High-speed steel (HSS) turning tools was designed and sharpened according to the angles of the complex shape cutting tools. CrAlTiN coating was deposited using unbalance magnetron sputtering plating technique. By dry turning tests, the wear characteristics and wear mechanisms of the face were investigated. The results show that the face wear of the coated HSS tools is obviously different from that of the uncoated tools, the crater width is smaller, the boundary is jagged and the lowest position is away from the major cutting edge. Adhesive wear and local adhesive wear are the main wear mechanisms.

Ablation efficiency and relative thermal confinement measurements using wavelengths 1,064, 1,320, and 1,444 nm for laser-assisted lipolysis

Laser-assisted lipolysis is routinely used for contouring the body and the neck while modifications of the technique have recently been advocated for facial contouring. In this study, wavelength-dependence measurements of laser lipolysis effect were performed using different lasers at 1,064, 1,320, and 1,444 nm wavelengths that are currently used clinically. Fresh porcine skin with fatty tissue was used for the experiments with radiant exposure of 5–8 W with the same parameters (beam diameter = 600 μm, peak power = 200 mJ, and pulse rate = 40 Hz) for 1,064, 1,320 and 1,444 nm laser wavelengths. After laser irradiation, ablation crater depth and width and tissue mass loss were measured using spectral optical coherence tomography and a micro-analytical balance, respectively. In addition, thermal temporal monitoring was performed with a thermal imaging camera placed over ex vivo porcine fat tissue; temperature changes were recorded for each wavelength. This study demonstrated greatest ablation crater depth and width and mass removal in fatty tissue at the 1,444 nm wavelength followed by, in order, 1,320 and 1,064 nm. In the evaluation of heat distribution at different wavelengths, reduced heat diffusion was observed at 1,444 nm. The ablation efficiency was found to be dependent upon wavelength, and the 1,444 nm wavelength was found to provide both the highest efficiency for fatty tissue ablation and the greatest thermal confinement.

Cutting Performance of WC-Co Alloys Modified by Nano-Additives

In this paper, the microstructure of WC-Co alloys with and without nano-additives was characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The hardness and fracture toughness was tested by using a Vickers hardness tester and a universal testing machine. The cutting test was carried out at different feed velocities (250 r/min and 320 r/min), and the contact pairs are cutting tools and 45# steel bars. Results showed that the hardness and fracture toughness of WC-Co cemented carbides with nano-additives are higher than that of WC-Co cemented carbides without nano-additives, and they are increased 10.21% and 19.69%, respectively. The flank worn width and crater width of cutting tools decrease greatly with the addition of nano-additives. For the nano-modified specimen with WC grain size of 7 μ m , both the flank worn width and crater width are the minimum after the cutting process. And there are little built-up layers and some pile-up regions on the flank face leading to high cutting performance for the nano-modified cemented carbides. There are some melted regions on the flank face of cutting tools without nano-additives, and the WC grains on the cross section of alloys without nano-additives show severe fragmentation. The wear type of WC-Co is flank wear, and the wear mechanism is abrasive, adhesion and oxidation wear.

A unique volcanic field in Tharsis, Mars: Pyroclastic cones as evidence for explosive eruptions

Based on theoretical grounds, explosive basaltic volcanism should be common on Mars, yet the available morphological evidence is sparse. We test this hypothesis by investigating a unique unnamed volcanic field north of the shield volcanoes Biblis Patera and Ulysses Patera on Mars, where we observe several small conical edifices and associated lava flows. Twenty-nine volcanic cones are identified and the morphometry of many of these edifices is determined using established morphometric parameters such as basal width, crater width, height, slope, and their respective ratios. Their morphology, morphometry, and a comparison to terrestrial analogues suggest that they are martian equivalents of terrestrial pyroclastic cones, the most common volcanoes on Earth. The cones are tentatively interpreted as monogenetic volcanoes. According to absolute model age determinations, they formed in the Amazonian period. Our results indicate that these pyroclastic cones were formed by explosive activity. The cone field is superposed on an old, elevated window of fractured crust which survived flooding by younger lava flows. It seems possible that a more explosive eruption style was common in the past, and that wide-spread effusive plain-style volcanism in the Late Amazonian has buried much of its morphological evidence in Tharsis.

Structural and morphometric irregularities of eroded Pliocene scoria cones at the Bakony–Balaton Highland Volcanic Field, Hungary

Scoria cones of the Mio-Pliocene Bakony–Balaton Highland Volcanic Field (BBHVF) are built up by wide range of volcanic rocks, including intercalated lava flows/dykes, pyroclastic breccias and scoriaceous lapilli with various degrees of welding or agglutination. According to K–Ar and Ar–Ar dating, ages of the fourteen scoria cones within the field span between 5.2 and 2.5 Ma. From these fourteen, seven cones were selected which are suitable for morphometric analysis, i.e. visible in the field and have identifiable boundaries. The morphometric data were either derived by manual measurement on topographic maps and by Digital Elevation Model-based calculations. Using the same input contour line data from 1:10,000 maps, basic cone parameters such as cone height, basal and crater width have been measured in order to calculate parameters like H co/W co ratio and average slope angle. The results of these ‘three-parameter’-based manual calculations have been compared to the DEM-based results in order to highlight the controls of degradation, pitfalls in morphometric parameterization and the differences between these two calculation methods. Based on the results, three main controlling conditions have been identified that are together responsible for the preservation and erosion of the scoria cones located in the BBHVF: (1) age of the cone, (2) climate during the degradation and the (3) inner architecture of the edifice. In terms of morphometric dating, the traditional, ‘three-parameter’-based method tends to give inaccurate results on (1) scattered and/or truncated cones and (2) on the edifices characterised by highly effusive behaviour during the emplacement.

Numerical Simulation of Temperature Field and Experimental Verification during Micro-Detonation of Arc Strike Machining

A theoretical model of heat transfer for Si3N4 ceramics during micro-detonation of arc strike machining was established. Based on finite element theory, the temperature of Si3N4 ceramics during micro-detonation of arc strike machining was simulated with the aid of COMSOL Multiphysics software, combined with the actual processing, the width and depth of crater impacted by micro-detonation were calculated. The simulation results show that the highest temperature of Si3N4 ceramics is over 12100 °C in a given processing parameters, while the high-temperature zone is quite small; the material removal rate with the increase of pulse width and electricity increases, with the increase of the nozzle radius first increases and then decreases; the diameter to depth ratio with the increase of pulse width and electricity decreases, with the increase of nozzle radius increases. The data gained from the simulation is proved to be accordant with the data gained from experiments.