Debris Shape Research Articles

Influence of blunt-nose and conical fragment on domino accident probability in spherical-tank area

Considering wind-speed influence, a new acceleration model is established, and a trajectory equation is obtained. The impact-depth models of a cone and end-cover debris are also established based on the cavity expansion theory. Combined with the residual strength theory, a new spherical-tank failure-probability model is established, and the probability model of a domino accident caused by the debris is obtained. Additionally, the influence of different fragment shapes on the domino accident probability in spherical tanks is analysed, and minimum penetration rate of the spherical-tank failure caused by different fragment masses is calculated. Subsequently, using statistics, the correlation between failure-probability and distance between spherical tanks and shape parameters was determined. The results indicate that the debris shape significantly influences the impact-depth of the spherical-tank wall, and impact-depth of the conical-nose geometry is significantly greater than that of the blunt-nose geometry. Moreover, the minimum velocity of the conical-nose geometry penetrating the target is significantly less than that of the blunt-nose geometry. The shape change of the conical-nose geometry has almost no influence on the probability of the domino accident, whereas, that of the blunt-nose geometry significantly influences the domino accident probability.

The paleoreconstruction of sedimentation conditions at Beshpagirskoe deposit of the Stavropol Krai based on the results of pebble morphology investigation

The morphology of pebbles provides important information for lithological-facial and paleogeographic constructions. The shape of the pebbles carries quite a variety of information about the geological processes of the distant past. Today, there is a large number of foreign and domestic studies devoted to the material and granulometric composition of psephites, while much less attention is paid to the morphological characteristics. Although very often it is the shape of the pebbles that can unambiguously resolve the issues of determining their genesis. Debris shape analysis includes the degree of contour rounding or roundness and the ratio of the three axial dimensions of the pebble: length, width and thickness. Based on the ratio of linear dimensions, judgments were made about the genesis of deposits, the direction of flow, the possibility of redeposition. The most popular are two factors: the shape factor of the fragment and the isometric factor. Conclusions: the end result of the genesis of the pebble material of the Beshpagirskiy quarry is the river alluvium of the ancient river network, subsequently rounded and polished in the coastal delta zone of the Sarmatian Sea. The flat-topped uplift of the Stavropol arch in the middle–upper Sarmatian can be considered the source of the supply of coarse-grained material. The research is of great interest for the search for mineral deposits.

Occurrence, Composition, and Relationships in Marine Plastic Debris on the First Long Beach Adjacent to the Land-Based Source, South China Sea

Land-based sources are the key sources of plastic debris, and mismanaged plastic debris can eventually enter the ocean via marine beaches. In this study, the spatial distribution and amount of plastic debris in the land-based source input zone of First Long Beach (FLB), China, which is a major tourist attraction, were first investigated. By using field investigation, sand samples were collected from two sections on FLB adjacent to land-based sources in December 2019, and the plastic debris in the sand samples was quantified and characterized in the laboratory. The amount of plastic debris ranged from 2 to 82 particles/m2 on this marine sand beach. There was a significant difference in plastic debris amount between the transects along the land-based source input zone (p < 0.05) due to the impacts of wind, ocean currents, and waves. The most abundant size of plastics was 0.5–2.5 cm (44.4%). Moreover, the most common color was white (60.9%). The most abundant shape of plastic debris fell into the fragment category (76.2%). The plastic debris amounts were significantly correlated with multiple sizes. Our results show that land-based wastewater discharge is a large plastic debris source on FLB under coastal water tide variation. Reduction strategies should be carried out by tracing the various land-based sources of plastic debris.

파편의 모양과 공기 항력 계수를 고려한 도비된 파편의 이동 거리 연구

When a building is detonated, the debris generated collides with the ground with very high energy and bounces back. This phenomenon is called ricochet. Ricochet increases risk by increasing the moving distance of the debris. The ricochet of debris is affected by the shape of the debris. In this paper, the behavior and moving distance of debris along the shape of debris were studied. For various initial conditions, the ricochet of debris was studied through the FEM, and the results were fitted to a 3D curved surface to predict the speed and angle after the ricochet. The moving distance of the debris was calculated using the trajectory formula considering the drag coefficient using the MATLAB. The ricochet of debris is affected by the contact area with the medium. As the contact area increases, the reflection angle increases because of the increase of the repulsive force. As the size of the debris increases, the energy loss also increases because of the increasing of the contact area. Thus, the moving distance of the cylinder debris is shorter than that of the sphere debris.

Scour at side by side pier and abutment with debris accumulation

This is the first attempt to study the effect of debris on the scour at side by side pier and abutment. A large set of experimental tests was carried out at the hydraulic laboratory of Shahid Bahonar University of Kerman, in a tilting flume with 10 m length, 0.8 m width and 0.5 m depth. Effect of debris shape, thickness, position, length, and the distance between abutment and pier was investigated. Results revealed that the main factor in deepening and developing of scour hole is the distance between pier and abutment, lp, by increasing the distance, the scour depth primarily increases and then decreases to eventually reach the scour depth at single pier. The observations indicated the significant effect of debris on dimensions of scour hole, for example, increasing the debris thickness and length increased the maximum scour depth up to 30 and 8%, respectively. Based on the measured data, some improvements were made on the existing equations and a set of new relations was presented to estimate the side by side pier and abutment scour depth.HighlightsFlow and scour pattern at side by side pier and abutment were investigated.Effect of debris accumulation on the scour processes was studied.Based on the measured data, improvements were made on the previous equations.New relations were proposed to predict side by side pier-abutment scour depth.

Polishing surface integrity of TC17 aeroengine blades

Aeroengine blades have high requirements for surface integrity. Through the flexible polishing of TC17 engine blades, the surface integrity of polished blades is improved. First, the influence of process parameters on polishing force and polishing temperature is analyzed through experiments. The influence of parameters on surface roughness is analyzed, and the relationship between wear debris shape and surface morphology under different process parameters are analyzed from the microscopic level. Second, the influence of process parameters on the residual stress of the polished surface is analyzed in accordance with the polishing force and polishing temperature. Then, the variation of the residual stress of the blade after milling and polishing is analyzed. In addition, the microstructure of the metamorphic layer after milling and polishing is analyzed. Experimental results show that reasonable polishing parameters can effectively improve the surface integrity of the blade.

Microplastics in the diet of nestling double-crested cormorants (Phalacrocorax auritus), an obligate piscivore in a freshwater ecosystem

Anthropogenic debris, namely plastic, is a concern across aquatic ecosystems worldwide, with freshwater systems being understudied relative to marine systems. In this study, we quantified and characterized debris in the diet of double-crested cormorant chicks (Phalacrocorax auritus) from three sites in two of the Laurentian Great Lakes to (i) determine whether or not the diet of double-crested cormorants in the Laurentian Great Lakes includes anthropogenic debris, (ii) characterize the size, shape, and type of debris incorporated, and (iii) examine relationships between the amount of debris ingested and their proximity to industrial–urban centres. Overall, >86% of cormorants in our study had anthropogenic debris (mostly fibers) in their digestive tracts with no correlation between site and the amount of debris ingested. The ingested debris includes microplastics, natural fibres from textiles, and other anthropogenic materials (e.g., glass). To the best of our knowledge, this is one of the first studies to examine anthropogenic debris in a diving bird in the Laurentian Great Lakes and one of few studies investigating this in freshwater birds.

Analysis and reduction of process energy consumption and thermal deformation in a micro-structure wire electrode electric discharge machining thin-wall component

Abstract In order to reduce process energy consumption and geometric error induced by thermal deformation simultaneously in sustainable wire electrode discharge machining(WEDM) process, this work applies a new micro crack wire electrode to enhance machine characteristic, and describes the reduction mechanism of above two critical factors compared with brass wire when machining thin-wall components. Firstly, a number of experiments are conducted to explore the effects trend of machining parameters on thermal deformation and material removal rate(MRR) by above two wire tools. The results indicate that micro crack wire can achieve a significant decrease by an average of 32.60% in MRR and 42.69% in thermal deformation compared with brass wire. And the best parameters combination for micro crack wire is pulse on time:13 μs、pulse off time:8 μs、wire speed:0.09 m/s、water pressure:1.1 MPa. The analysis of residual stress and discharge points distribution explains the improvement mechanism of micro crack wire by decreasing the magnitude of residual stress (33.14% on average) and non-uniformity of discharge points distribution (36.32% on average). Besides, the results of energy consumption and environmental effect demonstrate that micro crack wire can obviously reduce energy consumption by an average of 22.68% and debris pollution. Eventually, the analysis of surface topography, debris shape, micro structures, recast layer thickness and surface element composition are also performed. It can be concluded that the micro crack wire shows prominent superiority and potential for applications in the sustainable manufacturing field.

Plastic debris in marine birds from an island located in the South China Sea.

Plastic debris has become one of the most serious issues in the marine environment, but little information is available on the occurrence of plastic debris in marine birds from China. In this study, one seabird species and two shorebird species were collected from Yongxing Island of South China Sea to investigate the accumulation of plastic debris. A total of 56 items of plastic debris were observed in 4 of 9 birds, with size ranging from 0.67 to 8.64 mm. Microplastics (<5 mm, 52 items) accounted for 92.9% of the total items. The main color of plastic debris in marine birds was blue (91.1%), followed by dark (5.4%) and white (3.6%). The primary shape of plastic debris was thread (89.2%), followed by sheet (8.9%) and foam (1.8%). Plastic fragments were predominated by polypropylene-polyethylene copolymer (83.9%). This study highlighted that marine birds can mistake plastic debris as food items.

Effect of air supply speed on point contact sliding wear characteristics under oil‐air lubrication conditions

AbstractAn oil‐air lubrication system is driven by high‐speed air. Oil is transported to the contact portion in the form of fine oil droplets to form a lubrication film, thereby improving lubrication performance among matching pairs. A test for point contact sliding friction and wear was conducted under oil‐air lubrication conditions. Oil‐phase and pressure distributions near the contact zone were investigated through numerical simulation. This study aims to explore the effect of air velocity on sliding wear characteristics of a point contact. Results show that point contact sliding wear is considerably affected by air supply speed. The lubrication performance between friction pairs is optimal under appropriate air supply speed, which can enable the oil‐air pressure and oil‐phase volume fraction near the point contact area to obtain appropriate values that are useful to the spread of fine oil droplets. This process ensures that the sliding friction coefficient and specific wear rate can be reduced. The friction coefficient decreases to approximately 0.027, and the specific wear rate is 1.06 × 10−5 mm3/N·m. Under oil‐air lubrication, microfurrows appear on the worn surfaces of materials with the change in air supply speed. The shape of debris is mainly a flake or block with a few long strip abrasives. The wear mechanism is abrasive.

Investigation on the spatial distribution characteristics of behind-armor debris formed by the perforation of EFP through steel target

Abstract The behind-armor debris (BAD) formed by the perforation of an EFP is the main damage factor for the secondary destruction to the behind-armor components. Aiming at investigating the BAD caused by EFP, flash X-ray radiography combined with an experimental witness plate test method was used, and the FEM-SPH adaptive conversion algorithm in LS-DYNA software was employed to model the perforation process. The simulation results of the debris cloud shape and number of debris were in good agreement with the flash X-ray radiographs and perforated holes on the witness plate, respectively. Three-dimensional numerical simulations of EFP's penetration under various impact conditions were conducted. The results show that, an ellipsoidal debris cloud, with the major-to-minor axis radio (a/b) smaller than that caused by shaped charge jets, was formed behind the target. With the increase of target thickness (h) and decrease of impact velocity (v0) and obliquity (θ), the value of a/b decreases. The number of debris ejected from target is significantly higher than that from EFP. Based on the statistical analysis of the spatial distribution of the BAD, An engineering calculation model was established considering the influence of h, v0 and θ. The model can with reasonable accuracy predict the quantity and velocity distribution characteristics of BAD formed by EFP.

Restoration of defocused ferrograph images using a large kernel convolutional neural network

Wear debris analysis is used for machine condition monitoring because it is capable of identifying wear related faults in machinery components. In particular, wear mechanisms can be explored based on debris shape and texture features. As current wear monitoring practices prefer rapid data interpretation, on-line ferrograph is favored where debris images are collected and processed on-site with an imaging apparatus. However, such images are often blurred due to lubricant contamination and limited optical field depth. This drawback makes the subsequent investigation of wear debris features a challenging task. To address this issue, a restoration method is developed to reduce the influence of out-of-focus blurring in on-line ferrograph images. Firstly, in order to model the out-of-focus blurring process, a degradation model is constructed with a convolutional neural network. Different from general deep learning structures, larger convolutional kernels are embedded in the network to more comprehensively characterize the blurring process. Next, training samples of different types of debris are collected in the laboratory. The neural network structure then is optimized to minimize the difference between restored images and their corresponding ground truths. The final restoration is conducted based on the trained network via a pixel-wise regression process. To evaluate the performance of the developed method, experiments are carried out with debris images collected from a gear-box test rig. Results have demonstrated that: (1) the proposed restoration strategy allows robust extractions of debris features in greater detail; (2) the developed method is more computationally efficient than traditional deblurring techniques, which enables it to be applicable in on-line machine health monitoring.

Nonlinear finite element and fiber element analysis of concrete filled square steel tubular (cfst) under static loading

The combination of thin-walled steel structure with concrete infill can be used as the alternative material properties in the building in Indonesia. This composite material is suitable for seismic-resistant building because it has more ductility than conventional material. In the tsunami event, some tsunami debris strikes the building and induced partial or full collapse of the building. The loading tip shape of tsunami debris which contacts to a tubular surface affects the local deformation or buckling mode of the thin-walled structures. In order to investigate the effects, we conducted three-dimensional nonlinear finite element analyses of concrete filled square steel tubular members subjected to concentrated lateral loads by using the finite element analysis (FEM) program MSC Marc/Mentat. The fiber element analysis is also performed to reduce the analysis time of FEM and simplify the analysis. The accuracy of the FEM and fiber element analysis is verified by the experiment. Being based on the parametric numerical study, it discusses the effect of axial load on the load-deflection relations. It shows that the higher the axial load, the more degradation the ductility of the structure.

Restoration of low-informative image for robust debris shape measurement in on-line wear debris monitoring

Abstract As a significant technique in machine condition monitoring, wear debris analysis enables investigation of machine running condition with respect to debris features including size, quantity and morphology. In particular, being capable of providing more comprehensive morphological information, three-dimensional debris features are regarded essential and often acquired through a video-based debris imaging process. However, debris images captured often suffer degradation due to debris motion blur and lubrication contamination, that hinder reliable debris features extraction. To address the image degradation issue, a new method of wear debris image restoration is developed to reduce the effect of blur. In order to avoid the expensive computation involved in blind deconvolution methods, the debris image was restored using localized boundary features. Based on the fact that debris area and background area indicate distinctive brightness, a step edge model is applied to describe the original debris boundary. Localized kernels on each side of debris are then determined. Next, restorations are conducted with the estimated kernels to produce sharper debris profiles with respect to different motion features. Final restoration is conducted by fusing the restored profiles according to the maximum local sharpness. Experimental results have demonstrated that this method allows reliable features extraction from blurred image, improving the robustness of video based wear debris analysis.

One-dimensional coolability and concrete ablation analysis of volumetrically heat-generating debris bed

We present a preliminary study on the feasibility of the pre-flooded cavity strategy for ex-vessel cooling of APR1400 NPPs. Fragmented particles form a porous debris bed, so understanding the heat transfer mechanism in a porous medium and its critical heat flux is essential to assess the coolability of the debris bed. An one-dimensional dryout heat flux model of porous medium is derived from a water and vapor momentum equation for porous medium, two-phase permeability modifications and the correlation between capillary pressure and liquid saturation. The developed model is validated by comparing dryout heat flux data of DEBRIS, STXY, POMECO and COOLOCE tests. STXY BED, POMECO BED-5 and COOLOCE-8 BED are made to reflect the particle size distribution results of the melt fragmentation tests such as FARO, CCM, MIRA and DEFOR. We analyze the ex-vessel coolability by assuming that these three beds represent debris beds in actual accidents. In addition, one-dimensional coolability analysis is conducted for three cases of cylinder shape debris bed at containment pressures of 1–5bar. Based on these, one-dimensional ablation concrete depth analysis for the three cases of debris shape and the three kinds of the debris beds of APR1400 NPPs is conducted. As a result, if fragmented particles are distributed evenly and the POMECO BED-5 or STXY BED like debris bed is formed in the cavity, the debris bed coolability is so good that ablation depth is negligible or less than the thickness of sacrificial concrete. Even if the COOLOCE-8 BED like debris bed is formed, the integrity of the containment is kept during ex-vessel cooling if the containment pressure is maintained 3bar or more. However, if the solidified particles spread only in a particular area, the leak tightness of containment building could not be maintained in the ex-vessel cooling process. Because solidified particles lose their fluidity, so it is questionable that all of them are distributed uniformly in the cavity. Therefore, a further research is required on how fragmented particles are distributed in pre-flooded cavities to validate the pre-flooding strategy of APR1400 NPPs.

Automatic detection of snow avalanche debris in central Svalbard using C-band SAR data

Snow avalanches pose a threat to people and infrastructure in and around Svalbard’s main settlement Longyearbyen. Since January 2016, publically available regional avalanche warnings are issued daily for Nordenskiöld Land, the area around Longyearbyen. Avalanche warning services rely on information of when and where avalanches occur. Systematic field observations of avalanche activity are not feasible across all of the vast area (ca. 7200 km2) of Nordenskiöld Land. Svalbard also experiences over four months of polar night per year. However, using synthetic aperture radar (SAR), a weather- and light-independent technique, large areas can be monitored at once. We have developed a SAR-based automatic avalanche debris detection algorithm and tested it on satellite image pairs from Sentinel-1A at medium resolution and from Radarsat-2 at very high resolution. The detection algorithm uses a threshold value that distinguishes avalanche debris with increased backscatter from undisturbed snow with lower backscatter. Depending on the spatial resolution of the SAR image, different post-processing filters are applied. There is a promising level of agreement between automatic detection results and manual identification of avalanche debris, but the algorithm’s drawback is marked overdetection. We envision that further improvements in the form of avalanche debris shape recognition could ultimately lead to the development of operational avalanche activity maps. These frequently updated maps could then assist in regional avalanche forecasting, notably in and around Longyearbyen, Svalbard. The detection algorithm we have developed could eventually have applications in other avalanche-prone regions in the world.

Influence оf gravity and thermodynamics on the sliding electrical соntасt

The motivation behind this work is to develop a dynamical systems understanding of the wear processes. We present a model for wear particle detachment from a surface of electric brushes and slip ring (collector) in the commutator-and-brush assembly. The geometry of the contact area is analysed and debris shape modification is estimated. The investigation accounts for the dependence of the properties of the sliding contact layer on the deviation of this layer from land contour under Earth’s gravity and on the Joule–Thomson effect. With stochastic simulations we demonstrate that analytical model of the third body may explain the different lifetime of the electrical brush depending on it position relative to the slip ring axis, and we predict their durabilities.

Experimental investigation of tsunami-borne debris impact force on structures: Factors affecting impulse-momentum formula

This study investigates factors affecting tsunami-borne debris impact force on structures. Debris collision accelerations were measured at the contact point on the structure's seaward wall using disc- and box-shaped smart debris devices; the equation of motion was used to estimate the debris impact forces from the measured accelerations. Also, the impact force was measured at the base of the structure using a multi-axis load cell, and compared with the forces determined using the smart debris devices. The basic impulse-momentum formula was modified by the addition of coefficients, taking into account the added mass and the debris velocity. Debris shape also influenced the impact force. Deformability of the debris and flexibility of the structure both reduced the debris impact force.

Morphology and Dissolution Rate of Wear Debris from Silicon Nitride Coatings.

Silicon nitride (SiNx) coatings have recently been introduced as a potential material for joint implant bearing surfaces, but there is no data on wear debris morphology nor their dissolution rate, something that could play a central role to implant longevity. In this study, wear debris was generated in a ball-on-disc setup in simulated body fluid. After serum digestion the debris was analyzed with scanning electron microscopy and energy-dispersive X-ray spectroscopy. The particle dissolution rate was evaluated using inductively coupled plasma techniques, on model SiNx particles. The wear debris from SiNx coatings was found to be round, in the nm range and formed agglomerates in the submicrometer to micrometer range. Model particles dissolved in simulated body fluid at a rate of: c(t) = 39.45[1 - exp(-1.11 × 10-6t)], where [c(t)] = mg/L and [t] = s. This study can be used as a preliminary prediction of size, shape, and dissolution rate of wear debris from SiNx coatings.

소교량 유송잡물 저감시설의 비교 분석 연구

Damage to structures, such as bridge piers, are increasing rapidly due to the debris moving along rivers at the time of flooding. Therefore, the debris fin, debris deflector and debris sweeper, which are debris reduction systems, were produced in this study and an accumulation experiment was carried out on the experimental channel according to the existence of the reduction system. The debris fin is the reduction system that creates parallel flow on debris accumulated on the bridge to pass through the bridge, which was produced using wood. In addition, the debris deflector was produced using steel pipes and it has the type of detouring the direction of debris. The debris sweeper passes the debris using the magnetic force rotation of a screw-shaped cylindrical structure by water flow and it was produced using acrylic material. The experiment was carried out by analyzing the level of accumulation according to the hardness and dropping method of the debris and comparing the accumulation rate of reduction systems, and the experiment was carried out 5 times. According to the experimental results, there was a difference in the accumulation rate according to the type of reduction system and the shape of debris, and it often depended significantly on the initial shape of debris accumulation. The direct debris reduction effect on the bridge was higher in the order of the debris deflector, debris sweeper and debris fin, but in case of the debris deflector, damage, such as stream turbulence, changes in water level and river bed, and the loss of deflector can occur due to debris accumulated directly on the debris deflector. Therefore, it is necessary to design the debris deflector considering these issues.