Debris Size Research Articles

Procedure of the preparatory works execution during the remediation of high-rise buildings debris due to the disaster

The article covers one of the preparatory works types, in particular – the debris clearance. The types of machines and machinery, the purposes of the debris clearance, as well as the tasks for decrease of debris mass and scope are specified herein. The purpose of the article is to show the current level of the domestic machinery, as well as to share the experience of preparatory works. The article describes one of the preparatory works types, in particular – the debris clearance during the high-rise buildings demolition. Given are the equipment and machinery types, covered are the purposes and procedure of debris clearance defined are the tasks on reduction of debris mass and sizes. Specified are the types and methods of the preparatory works execution. The purpose of this article is to demonstrate the domestic equipment current state, and to share the experience in preparatory works execution.

Effect of spark gap voltage and wire electrode feed rate on machined surface morphology during Wire EDM process

Nature of machined surface morphology during wire electro discharge machining (Wire EDM) process depends on input process parameters like pulse on duration (Ton), pulse off duration (Toff), spark gap voltage (SV) and wire electrode feed rate (WF). After initial experimentation, duty factor (Ton/Ton+Toff = 120/150) was decided to be 0.8 based on suitable material removal rate. Afterwards effect of spark gap voltage and wire electrode feed rate on machined surface morphology was investigated. It was found that at lower spark gap voltage re-solidification and accumulation of debris on machined surface is more which reduces with increasing spark gap voltage. Debris size increases with increasing spark gap voltage and higher wire electrode feed rate leads to sparse accumulation of debris on machined surface.

Differential impact of marine debris ingestion during ontogenetic dietary shift of green turtles in Uruguayan waters

Anthropogenic debris ingestion has been reported for green turtles in all their life stages worldwide. The aim of the present study is to evaluate the marine debris ingestion by green turtles stranded in Uruguayan coast between 2005 and 2013. Debris items were categorized and quantified by frequency of occurrence, relative weight, volume and number of items. A total of 96 dead stranded turtles were analyzed and 70% presented debris in their guts. The majority of debris found were plastic, being hard plastics the most abundant in weight. We found no differences in debris ingestion in stranded turtles a long the Uruguayan coast. However we detected a negative correlation between the presence of debris and turtle's size. Smaller turtles are new recruits to neritic grounds indicating that the early juvenile stage of this species is the most vulnerable to this threat in the Southwestern Atlantic.

Experimental assessment and validation of an oil ferrous wear debris sensors family for wind turbine gearboxes

PurposeThe purpose of this study was to perform a complete experimental assessment of a family of oil ferrous wear debris sensor is performed. The family comprised the original sensor and its re-engineered evolution, which is capable of detecting both amount and size of wear debris particles trapped by the sensor and some predefined oil condition properties.Design/methodology/approachIn this work, the first step was to perform a design of experiments for the sensor validation. A specially defined test rig was implemented, and different ferrous wear debris was collected. For each sensor, two different tests were performed. The first test was called a “void test”, where quantified amounts of debris were collided with the sensor without oil. The second one was a dynamic test, where the sensor was installed in the test rig and different amounts of wear debris were added at a constant rate. In addition, specific tests related with oil properties detection were studied.FindingsThe results show excellent correlation of the sensor output signal with the amount of wear debris and a satisfactory detection of debris size in all ranges. Also, the dynamic test presented adequate representativeness, and sensors performed well in this scenario.Practical implicationsThis paper shows the practical implementation of this type of sensor and the usual detection range and rate of detection for different debris size and quantities.Originality/valueThis work has a great utility for maintenance managers and equipment designers to fully understand the potential of this type of sensor and its suitability for the application required.

Nanoplastic in the North Atlantic Subtropical Gyre.

Plastics can be found in all ecosystems across the globe. This type of environmental pollution is important, even if its impact is not fully understood. The presence of small plastic particles at the micro- and nanoscales is of growing concern, but nanoplastic has not yet been observed in natural samples. In this study, we examined four size fractions (meso-, large micro-, small micro-, and nanoplastics) of debris collected in the North Atlantic subtropical gyre. To obtain the nanoplastic portion, we isolated the colloidal fraction of seawater. After ultrafiltration, the occurrence of nanoscale particles was demonstrated using dynamic light scattering experiments. The chemical fingerprint of the colloids was obtained by pyrolysis coupled with gas chromatography-mass spectrometry. We demonstrated that the signal was anthropogenic and attributed to a combination of plastics. The polymer composition varied among the size classes. At the micro- and nanoscales, polyvinyl chloride, polyethylene terephthalate, polystyrene and polyethylene were observed. We also observed changes in the pyrolytic signals of polyethylene with decreasing debris size, which could be related to the structural modification of this plastic as a consequence of weathering.

Surface temperature and wear particle analysis of vertical motion double-nut ball screws

PurposeThis paper aims to investigate the temperature and wear properties of vertical ball screws and to discuss the surface design of ball screws in industrial applications.Design/methodology/approachThe energy equation of the screw surface considering the frictional heat was established to verify the surface temperature of the ball screw. X-ray diffraction was used to examine the micro-contact temperature between the ball and screw. Debris size and density were examined to investigate wear properties of ball screws and to study the relationship of wear debris and temperature.FindingsFirst, the main energy source for the surface temperature of high speed vertical ball screws is derived from friction force between ball and screw. Second, the temperature rise between the ball and screw has great relevance with wear debris concentration. Third, the surface temperature of the screw is higher than between the nut and ball for high speed vertical ball screws due to high convection heat transfer. The contact temperature of the nut near the flange is smaller than that of the nut away from the flange end due to the high contact load and thermal conduction. Finally, correlation of particle size and surface roughness value for vertical ball screws was established, and its effects on contact temperature were studied. The theoretical analysis and experiments will help to characterize the design and manufacture of vertical ball screws.Originality/valueThe surface temperature and micro-contact temperature analytical model were established to study the ball screw design. Based on the surface-particle micro-contact temperature balance, the optimal range of surface roughness was designed for vertical ball screws, considering the wear debris and micro-contact temperature.

Export of Plastic Debris by Rivers into the Sea.

A substantial fraction of marine plastic debris originates from land-based sources and rivers potentially act as a major transport pathway for all sizes of plastic debris. We analyzed a global compilation of data on plastic debris in the water column across a wide range of river sizes. Plastic debris loads, both microplastic (particles <5 mm) and macroplastic (particles >5 mm) are positively related to the mismanaged plastic waste (MMPW) generated in the river catchments. This relationship is nonlinear where large rivers with population-rich catchments delivering a disproportionately higher fraction of MMPW into the sea. The 10 top-ranked rivers transport 88-95% of the global load into the sea. Using MMPW as a predictor we calculate the global plastic debris inputs form rivers into the sea to range between 0.41 and 4 × 106 t/y. Due to the limited amount of data high uncertainties were expected and ultimately confirmed. The empirical analysis to quantify plastic loads in rivers can be extended easily by additional potential predictors other than MMPW, for example, hydrological conditions.

Reduced clot debris size using standing waves formed via high intensity focused ultrasound

The feasibility of utilizing high intensity focused ultrasound (HIFU) to induce thrombolysis has been demonstrated previously. However, clinical concerns still remain related to the clot debris produced via fragmentation of the original clot potentially being too large and hence occluding downstream vessels, causing hazardous emboli. This study investigates the use of standing wave fields formed via HIFU to disintegrate the thrombus while achieving a reduced clot debris size in vitro. The results showed that the average diameter of the clot debris calculated by volume percentage was smaller in the standing wave mode than in the travelling wave mode at identical ultrasound thrombolysis settings. Furthermore, the inertial cavitation dose was shown to be lower in the standing wave mode, while the estimated cavitation bubble size distribution was similar in both modes. These results show that a reduction of the clot debris size with standing waves may be attributed to the particle trapping of the acoustic potential well which contributed to particle fragmentation.

Determining the Particle Size of Debris from a Tunnel Boring Machine Through Photographic Analysis and Comparison Between Excavation Performance and Rock Mass Properties

This paper presents the results of a study carried out on a 6.3-m-diameter exploratory tunnel excavated in hard rock by an open tunnel boring machine (TBM). The study provides a methodology, based on photographic analysis, for the evaluation of the particle size distribution of debris produced by the TBM. A number of tests were carried out on the debris collected during the TBM advancement. In order to produce a parameter indicative of the particle size of the debris, the coarseness index (CI) was defined and compared with some parameters representative of the TBM performance [i.e. the excavation specific energy (SE) and field penetration index (FPI)] and rock mass features, such as RMR, GSI, uniaxial compression strength and joint spacing. The results obtained showed a clear trend between the CI and some TBM performance parameters, such as SE and FPI. On the contrary, due to the rock mass fracturing, a clear relationship between the CI and rock mass characteristics was not found.

Acoustic Emission Characteristics of Sedimentary Rocks Under High-Velocity Waterjet Impingement

The success of waterjet drilling technology requires further insight into the rock failure mechanisms under waterjet impingement. By combining acoustic emission (AE) sensing and underwater sound recording techniques, an online system for monitoring submerged waterjet drilling has been developed. For four types of sedimentary rocks, their AE characteristics and correlations to the drilling performance have been obtained through time–frequency spectrum analysis. The area under the power spectrum density curve has been used as the indicator of AE energy. The results show that AE signals from the fluid dynamics and the rock failure are in different ranges of signal frequency. The main frequencies of the rock failure are within the higher range of 100–200 kHz, while the frequencies of the fluid dynamics are below 50 kHz. Further, there is a linear relationship between the AE energy and the drilling depth irrespective of rock type. The slope of the linear relationship is proportional to the rock strength and debris size. Furthermore, the AE-specific energy is a good indicator of the critical depth drilled by the waterjet. In conclusion, the AE characteristics on the power density and dominant frequency are capable of identifying the waterjet drilling performance on the rock materials and are correlated with the rock properties, i.e., rock strength and cutting size.

Experimental Investigation of Melt Coolability Under Bottom Injection: Effects of Melt Volume, Melt Composition, Nozzle Diameter, and Inlet Pressure

Melt pool coolability is one of the concerns when addressing severe accident scenarios. Long-term cooling and stabilizing of highly radioactive and reactive molten corium are still issues to be addressed and understood in order to devise a successful handling strategy. Core catchers have been envisaged in present and future advanced reactors to manage this concern. In the ex-vessel core catcher scenario, corium relocates to form a molten pool. Injecting water from the bottom of this melt pool to achieve coolability is found to be an efficient technique so far. However, the numbers of tests with prototypic materials and conditions are very limited and difficult to perform. In view of this, most of the earlier studies have been conducted with simulated melts. There are concerns with regard to scalability of experiments, effects of melt composition, and geometric parameters on melt coolability. To address these issues, series of experiments have been conducted and are presented in this paper. The experiments are performed with borosilicate glass, with two melt volumes, i.e., 3 and 20 L, and are compared. They show that the melt quenching time was more or less the same and suggest that the results can be extrapolated to higher scales. Two different simulants were used in the experiments, i.e., sodium borosilicate glass and CaO-B2O3, to study the effect of melt composition, and it was observed that the coolability behavior remains the same but the melt quenching time varies. The effect of nozzle diameters was studied by conducting experiments with three different nozzle diameters of 8, 12, and 18 mm keeping the same inlet pressure. It was found that the quenching time was higher for the 8-mm-diameter nozzle experiment due to smaller flow rates compared to the others. The experiments were repeated at two inlet water pressures of 0.35 and 0.75 bar(g) for the same nozzle diameter to study their effects on melt coolability. As expected, the quenching time was found to be less for the case of higher inlet pressure. The experimental measurements suggest that the overall average melt pool coolability behavior under bottom flooding was almost the same in all cases. However, each physical parameter affects the melt quenching time required to cool the melt. This average melt quenching time can be optimized using suitable combinations of geometric and physical parameters. The debris sizes and porosities formed during the melt eruption were also measured. The measured porosities ranged between 50% and 60% in all experiments.

Plastics in the North Atlantic garbage patch: A boat-microbe for hitchhikers and plastic degraders

Plastic is a broad name given to different polymers with high molecular weight that impact wildlife. Their fragmentation leads to a continuum of debris sizes (meso to microplastics) entrapped in gyres and colonized by microorganisms. In the present work, the structure of eukaryotes, bacteria and Archaea was studied by a metabarcoding approach, and statistical analysis associated with network building was used to define a core microbiome at the plastic surface. Most of the bacteria significantly associated with the plastic waste originated from non-marine ecosystems, and numerous species can be considered as hitchhikers, whereas others act as keystone species (e.g., Rhodobacterales, Rhizobiales, Streptomycetales and Cyanobacteria) in the biofilm. The chemical analysis provides evidence for a specific colonization of the polymers. Alphaproteobacteria and Gammaproteobacteria significantly dominated mesoplastics consisting of poly(ethylene terephthalate) and polystyrene. Polyethylene was also dominated by these bacterial classes and Actinobacteria. Microplastics were made of polyethylene but differed in their crystallinity, and the majorities were colonized by Betaproteobacteria. Our study indicated that the bacteria inhabiting plastics harboured distinct metabolisms from those present in the surrounding water. For instance, the metabolic pathway involved in xenobiotic degradation was overrepresented on the plastic surface.

INVESTIGATING THE RELATIONSHIP BETWEEN RAINFALL INTENSITY, CATCHMENT VEGETATION AND DEBRIS MOBILITY

Urbanisation creates the need for engineered hydraulic structures in catchments, floodplains and watercourses. These include piped and open-channel drainage networks, flood control systems and waterway crossings such as culverts and bridges. During larger storm events, debris and other material located higher in the catchment can be mobilised and transported towards these hydraulic structures creating the potential for blockages. This debris is often trapped by the hydraulic structures, causing partial or full blockage which can reduce the flow capacity of the structure. This may cause upstream flooding during high intensity rainfall events. This study investigated the debris transport behaviour in a natural channel. A model of an existing catchment and culvert system in Australia was build based on Froude similitude scaling. Different sized twigs were used to replicate natural debris of various sizes. The experimental results demonstrated that the mobility of debris during rainfall events was dependent on a range of factors including stream depth and width, the size and availability of debris, and on the condition of the riparian vegetation within the catchment. This could have significant implications for culvert design and maintenance procedures.

Experimental study on thermal-hydraulic behaviour of LBE and water interface

For the design and safety studies of steam generator in the China LEAd-based Reactor (CLEAR) project, it is necessary to investigate the consequences of a Steam Generator Tube Rupture (SGTR) accident which could result in a reaction between Lead-Bismuth Eutectic (LBE) and highly pressurised water. Some experiments have been conducted to investigate the thermal-hydraulic behaviour of the molten LBE/water interface; the whole fragmentation processes of these experiments were visually observed with a high-speed video camera, and the transient pressure histories were measured by high-frequency piezoelectric pressure sensors. The effects of LBE temperature, water temperature, nozzle diameter and injection velocity were investigated. Visualisation films indicated that the explosion phenomenon happened readily at lower water temperature. The peak pressure decreased with increasing water temperature, nozzle diameter and injection velocity. However, the peak pressure first increased and then decreased as the LBE temperature increased. The shape of the debris became round at higher water temperature, and a needle-like shape was observed at lower temperatures. Debris analysis results showed that the debris sizes of 2.8–6.7 mm had the largest mass fraction. By comparison with the theoretical calculation, it was found that the fragment diameters measured in the present study agreed well with Weber number theory. Thus, it was demonstrated that the fragmentation mechanism was controlled by shearing stress under the present experimental conditions.

Effect of debris size on the reciprocating sliding wear of aluminium

The literature is controversial in relation to the influence of wear debris on tribological behaviour. Some works have shown that the presence of debris is fundamental to the formation of a protective tribolayer, thus reducing friction, whereas others showed that the presence of wear debris could contribute to increase friction coefficient due to the energy spent dragging them into the contact. This work aims to study the influence of the presence of wear debris, simulated by Al2O3 particles, on the tribological behaviour of an aluminium-steel pair under reciprocating sliding contact. Special emphasis is given to the particle size (0.05 µm, 0.1 µm, 1 µm and 10 µm). The particles were dispersed in distilled water (2 wt.%) as the source of debris. Reference tests were carried out solely in the presence of distilled water. The addition of alumina particles contributed to a significant reduction in friction coefficient, in particular for the largest particles (diameter ϕ=10 µm). When the larger particles were added, it was possible to observe the formation of a tribolayer on the sample surface leading to a gain of mass. In opposition, the wear rate of the counter body increased when large particles were added and the wear tracks showed strong evidence of abrasive wear. This suggests that hard and large wear debris, incorporated in the tribolayer formed on the samples, can act as hard protuberances, leading to abrasive wear of the counterbodies. When small particles were added, friction was still reduced when compared with the reference test, but the reduction of the friction coefficient was less significant. Small particles reduced the steel counter body wear rate and did not affect significantly the wear rate of the aluminium samples. It is proposed that small debris can get entrapped in the surface irregularities of the specimens and therefore participate less in the formation of the tribolayers.

Assessing quantitative metrics of transfer film quality as indicators of polymer wear performance

Reduced wear rates of filled polymeric tribomaterials consistently accompany improvements in the appearance of the transfer film, a protective layer of debris that adheres to the counterface. As a result, wear reductions are often attributed to the favorable effects of the filler on transfer film quality. However, the cause-effect relationship between fillers, transfer film quality, and polymer wear performance remains uncertain due, in part, to a lack of standard metrics for assessing transfer film quality. Methods for quantifying transfer film thickness and area fraction have been proposed previously; although some studies show strong correlations between these parameters and wear rate, others have demonstrated a lack of general applicability. In a more recent study, it was proposed that the characteristic size of the gaps in the transfer film (free-space length) may better reflect visual differences in transfer film quality and more directly relate to debris size and wear rate. In this paper, a representative collection of common tribological polymers and composites were subjected to wear testing and transfer film topology characterization to better generalize the link between polymer wear performance and transfer film topology (thickness, coverage, and domain size-scales). The free-space length provided the best correlation with steady state wear rates of the tribopolymers in this study and prediction of wear rates from previous studies. The results suggest that, among the metrics considered, the free-space length provides the best independent measure of transfer film quality in the context of polymer wear.

Experiment and smooth particle hydrodynamics simulation of debris size in grinding of calcified plaque in atherectomy

This research studies the debris size in grinding of hardened calcified plaque inside the artery. Experiments for grinding of bone surrogate for calcified plaque at 135,000, 155,000 and 175,000rpm using a 2.5mm diameter diamond wheel were conducted and the debris size was measured by laser scattering. The smooth particle hydrodynamics (SPH) simulation was developed to predict the debris size in grinding. Experimental results showed that debris size matched well by the SPH grinding simulation with a 0.91 Pearson correlation coefficient. The debris size was generally smaller than 40μm and decreased with higher wheel speeds.

Oil metal particles Detection Algorithm Based on Wavelet Transform

In order to observe the real-time abrasion status of the aero-engine, we need to monitor the lubrication system online. As the aero-engine operating time and running state changes, the concentration, composition, size and other parameters of the metal debris can show different changes. They can be used as an important indicator to reflect the state of the aero-engine fault. However, due to the influence of electromagnetic, vibration disturbance and random noise signal introduced by the processing unit itself, the metal particles signal tend to comprise noise. Oil metal particles detection algorithm based on wavelet transform, utilizes the optimized localized nature in time domain and frequency domain of wavelet transform and the characteristics of multi-resolution analysis, combined with the signal characteristics in actual aero-engine condition to realize noise reduction and detection, while validating the algorithm using real experimental data. The result shows that noise can be effectively decreased and signal characteristics can be detected correctly.

Study the Space Debris Impact in the Early Stages of the Nano-Satellite Design

Abstract The probability of KufaSat collisions with different sizes of orbital debris and with other satellites which operating in the same orbit during orbital lifetime was determined. Apogee/Perigee Altitude History was used to graph apogee and perigee altitudes over KufaSat lifetime. The required change in velocity for maneuvers necessary to reentry atmospheric within 25 years was calculated. The prediction of orbital lifetime of KufaSat using orbital parameters and engineering specifications as inputs to the Debris Assessment Software (DAS) was done, it has been verified that the orbital lifetime will not be more than 25 years after end of mission which is compatible with recommendation of Inter-Agency Space Debris Coordination Committee (IADC).

Ejection of Micron-Scale Fragments from Triangular Grooves in Laser Shock-Loaded Copper Samples

When a material is submitted to a dynamic compression, a shock wave propagates through the bulk and potentially interacts with a free surface. If this surface has geometrical defects such as grooves, some material ejection can occur. The energy of the high velocity ejecta is an area of concern for many applications, such as industrial safety, pyrotechnics or inertial confinement fusion. We have studied this phenomenon of microjetting from calibrated grooves in laser shock-loaded Cu samples, combining complementary experimental, numerical and analytical approaches, in order to investigate the formation and the fragmentation of the jets over ranges of small spatial (~µm) and temporal (~ns) scales and extremely high strain rates (~107 s−1). Various grooves were used with different depths and aperture half-angles (20°, 30°, 45°). The velocities measured by fast shadowgraphy and heterodyne velocimetry were compared to numerical predictions using the finite element or the smoothed particles hydrodynamics formulations with the Radioss code. Size distribution of the ejecta was inferred from rough measurements of the debris sizes and compared to analytical predictions from a probability law.