Characteristics Of Debris Research Articles

On the mechanical and tribological behavior of Al3Mg2 complex metallic alloys as bulk material and as coating

New materials with tunable physical, mechanical, chemical, and thermal properties are attractive for many applications and stand as prospective substitutes for the existing engineering materials. In that respect, complex metallic alloys (CMA) have recently demonstrated promising traits where a myriad of physical, mechanical, chemical properties can be obtained by altering the structure. CMA’s have a large crystal size with thousands of atoms per unit cell. In this work, some mechanical properties and tribological behavior of Al3Mg2 based CMA are discussed. The surface characterization, deformation mode, mechanical and tribological properties of bulk and thin film Al3Mg2 materials are investigated, and compared with existing engineering materials. The results revealed a contrasting tribological behavior of Al3Mg2 when used as either bulk material or as coating. Al3Mg2 coatings act as a low friction solid lubricant under certain conditions, with a coefficient of friction comparable to that of diamond-like carbon coatings. It is suggested that the quasi-crystalline nature of Al3Mg2-coatings renders the surface stiff and that the characteristics of the wear debris generated are responsible for the low friction behavior.

Practical engineering approaches and infrastructure to address the problem of marine debris in Korea

As a solution to the problem of persistent solid marine debris, a nationwide project began in Korea in 1999 to develop and popularize fundamental changes to the infrastructure. The ten year project, called “A Practical Integrated System for Marine Debris,” consists of four linked types of technology: prevention, deep-water survey, removal and treatment (recycling). These reflect the characteristics of marine debris, which though widespread, vary by location and time of generation. Each technical component has each representative outcome that has been outreached the local governments and marine debris-related associations. The in situ infrastructures lead to enhance the retrieval of the marine debris and create direct and indirect benefits to industry. Both end-of-pipe technology improvement and the introduction of front-of-pipe technology should be considered as we strive to reduce the generation of marine debris in Korean coastal areas.

The Relationship between the Presence of Metallosis and Massive Infection in Metal-on-Metal Hip Replacements

With the increased use of metal-on-metal as a bearing surface, complications and side effects are being recognised more frequently. We present a small series of a previously unreported complication, which appears specific to metal-on-metal bearing surface arthroplasties: three cases of infection in the presence of local metal debris and histological features of aseptic lymphocytic vasculitis associated lesions (ALVAL). Each case is associated with significant soft tissue loss and bone destruction to such an extent that pelvic discontinuity has occurred. We postulate that the combination of metal debris, ALVAL and tissue necrosis provides a unique environment for peri-prosthetic bacterial growth and rapid spread of infection.

Relationship between the geometric features of carbon steel cavitation erosion debris and the cavitation erosion stages

The debris produced in vibration cavitation tests of three kinds of carbon steel were collected. Their geometric features were analyzed quantitatively and observed respectively by a profilometer and a scanning electronic microscope (SEM) with reference to the investigation of the cavitation damaged surface by SEM and X-ray diffraction (XRD). It was found that among the debris produced in all cavitation erosion stages, more than 45% were platelets because of the occurrence of dislocation and cleavage fracture, and only less than 25% were strands. The number of granule was small in the first cavitation erosion stage and increased rapidly to the number comparable with that of platelets in the next stage, and then reduced in the third stage. The sphericity values of the debris varied in accordance with the stages of cavitation damage, which were 0.3–0.4 in the incubation stage, 0.5–0.7 in the acceleration stage and not less than 0.5 in the maximum rate stage, although a slight decrease occurred in the third stage.

Laser-plasma debris from a rotating cryogenic–solid-Xe target

We investigate the characteristics of laser plasma debris that is responsible for damaging optics. The debris is composed of fast ions, neutral particles, and fragments, and originates from a solid Xe target on a rotating drum that we developed as an extreme ultraviolet (EUV) source. The ice fragments appear to be a problem most notably with solid Xe targets; however, we find that the damage induced by Xe ice fragments can be avoided by simply reducing the laser pulse energy. We find the number of fast neutral particles to be an order of magnitude less than the number of ions, and we clarify that the plasma debris is primarily composed of fast ions. In addition, we find that the number of fast ions having a few dozen keV of energy decreases when using the rotating target compared with the rest target. We attribute this to a gas curtain effect from the Xe gas localized at the rotating target surface. We estimate the sputtering rate of the Mo/Si mirror, which is caused primarily by the fast ions, to be 104 nm/1x10(6) shots at 190 mm from the source plasma and at an 11.25 degree angle from the incident laser beam. Up to the 1x10(6) shots exposure, remarkable degradation of the mirror reflectivity is not observed though the sputtering damages the mirror. Mitigation of the ions by using gas and/or magnetic fields will further improve the mirror lifetime. By comparing with a liquid jet Xe target, we conclude that the sputtering rate per conversion efficiency when using the solid Xe targets on the rotating drum is the same as that when using the liquid Xe targets. The high conversion efficiency of 0.9% in the rotating drum solid Xe target makes this technique useful for developing laser plasma EUV sources.

Characteristics of coarse woody debris in successional stages of natural beech (Fagus orientalis) forests of Northern Iran

Coarse woody debris (CWD) is an important structural and functional component in forests in Northern Iran. In this study we determine the temporal patterns of CWD in Kheyroud Forests by examining the CWD volume in different decay classes and size classes along a chronosequence of secondary forest succession. The volume of CWD followed the general “U-shaped” temporal trend: the highest in the late successional forest (51.25 m<sup>3</sup>.ha<sup>–1</sup>), lowest in the middle successional forest (25.95 m<sup>3</sup>.ha<sup>–1</sup>) and intermediate in the early successional forest (37.05 m<sup>3</sup>.ha<sup>–1</sup>). The late successional forest had a larger amount of logs, snags and stumps than the other two forests. In contrast, the snag volume did not differ between the late and middle successional forest. CWD in decay classes III and V was greater in the late successional forest than that in the other two forests, while CWD in decay classes II and I did not differ among the three successional forests. CWD in class II and I was significantly higher in the early successional forest than that in the middle successional forest. In the early and middle successional forests, CWD in early decay class was dominated by <I>Carpinus betulus</I> L. followed by <I>Fagus orientalis</I> Lipsky. In the late successional forest, CWD in early decay class was dominated by <I>Fagus orientalis</I> while CWD in the late decay class was dominated by <I>Carpinus betulus</I>. While forest succession had a large influence on the amount of CWD in different decay classes, it had no effect on CWD distribution among the different size classes. Our results suggest that both anthropogenic and natural disturbances have had a long-term effect on the distribution of CWD among three forests.

On the ferro-graphic characterisation of wear debris in tribological system by grey fixed weight clustering

Both characterisation of wear debris and identification of wear debris from lubricating oils and greases in the tribological systems were investigated in the present paper. The characterisation system to describe wear debris morphology was erected based on the identification parameters of wear debris in the ferro-graphic system. Four characterisation parameters were analysed, including colour, surface texture, shape and size of wear debris. By using grey fixed weight clustering method, six kinds of wear debris were recognised, i.e., normal wear debris, ball particles, cutting debris, sever sliding debris, debris of Fe2O3 and Fe3O4, which is helpful to pre-diagnose the fault type of machinery.

A new delamination pattern in elevated-temperature oxidative wear

The sliding wear tests were performed under the atmospheric conditions at 400 °C for H13 steel. The effects of load on the wear mechanisms and delamination patterns were studied. A new delamination pattern was found to appear in the mild-severe transition region of the elevated-temperature wear. The delamination pattern could be proved by the belt-like debris and the corresponding wide ditches on worn surfaces. Under the loads of 50–100 N, mild oxidative wear prevailed with the characteristics of the plate-like oxide debris and low wear loss and its delamination was from inside oxides or the interface between the oxides and bulk metal. The wear rate increased with increasing load; the mild–severe wear transitions occurred under the loads of 100–200 N concomitant with more and more belt-like debris and wide ditches on worn surfaces. In this case, the wear loss would be mainly attributed to a special delamination from inside the bulk metal underneath the tribo-oxides with the formation of belt-like debris containing oxide and bulk metal. The delamination pattern was realized by the way that the ploughed furrows were first formed by the micro-cutting of oxide particles in the delaminated zone, whereby cracks initiate from the furrow wall and propagate parallel to worn surface to cause the delamination.

Numerical surface characterization of wear debris from artificial joints using atomic force microscopy

Study on surface features of wear particles generated in wear process provides an insight into the progress of material failure of artificial joints. It is very important to quantify the surface features of wear particles in three dimensions. In this study, a new approach using atomic force microscopy was proposed to carry out 3D numerical surface characterization of wear debris generated from artificial joints. Atomic force microscopy combined with image processing techniques was used to acquire appropriate 3D images of wear debris. Computerized image analysis techniques were then used to quantify surface texture features of wear debris such as surface roughness parameters and surface texture index. The method developed from the present study was found to be feasible to quantity the surface characterization of nano- and micro-sized wear debris generated from artificial joints.

Metal wear particles: What we know, what we do not know, and why

The importance of wear particle characterization for orthopaedic implants has long been established in the hip and knee arthroplasty literature. With the increasing use of motion preservation implants in the spine, the characterization of wear debris, particularly metallic nature, is gaining importance. An accurate morphological analysis of wear particles provides for both a complete characterization of the biocompatibility of the implant material and its wear products, and an in-depth understanding of the wear mechanisms, ion release, and associated corrosive activity related to the wear particles. In this paper, we present an overview of the most commonly-used published protocols for the isolation and characterization of metal wear particles, and highlight the limitations and uncertainties inherent to metal particle analysis.

Forest characteristics and their variation along the lakeshore–upland ecotone

In forestry operations riparian buffer zones have been retained mainly to protect water quality. Because riparian forests are also important for maintaining terrestrial biodiversity, the associated ecotones need to be characterized and defined. Forest characteristics were studied along 50 m lakeshore–upland gradients in semi-natural forests in boreonemoral Sweden. Significant changes in the density of living and dead trees, as well as in their diameters, were recorded. The edge influence was generally discernible 10–30 m from the shoreline and was manifested in the very high density of understorey and midcanopy trees. The species-specific responses reflected the known shade and flooding tolerances of tree species. Most dead trees were standing, or broken from the roots or tree base; relatively few uprooted trees were recorded, suggesting that wind is only a moderate mortality factor. In comparison with the literature, the studied lakeshore forests are distinct from managed and set-aside upland forests in terms of tree species composition and woody debris characteristics; they thus contribute to landscape heterogeneity. If buffer zones along lakes were designed so that they captured the entire riparian ecotone, this would increase their contribution to the conservation of terrestrial biodiversity.

Coolability of particulate beds in severe accidents: Status and remaining uncertainties

Particulate debris beds may form during different stages of a severe core melt accident; e.g. in the degrading hot core, due to thermal stresses during reflooding, in the lower plenum, by melt flow from the core into water in the lower head, and in the cavity by melt flow out of a failing RPV into a wet cavity. Deep water pools in the cavity are used in Nordic BWRs as an accident management measure aiming at particulate debris formation and coolability. It has been elaborated in the joint work of the European Severe Accident Research Network (SARNET) in Work Package (WP) 11.1 that coolability of particulate debris, reflooding of hot debris as well as boil-off under decay heat (long-term coolability), is strongly favoured by 2D/3D effects in beds with non-homogeneous structure and shape. Especially, water inflow from the sides and via bottom regions strongly improves coolability as compared to 1D situations with top flooding, the latter being in the past the basis of analyses on coolability. Data from experiments included in the SARNET network (DEBRIS at IKE and STYX at VTT) and earlier ones (e.g. POMECO at KTH) have been used to validate key constitutive laws in 2D codes as WABE (IKE) and ICARE/CATHARE (IRSN), especially concerning flow friction and heat transfer. Major questions concern the need of the explicit use of interfacial friction to adequately treat the various flow situations in a unified approach, as well as the adequate characterization of realistic debris composed of irregularly shaped particles of different sizes. Joint work has been supported by transfer of the WABE code to KTH and VTT. Concerning realistic debris, the formation from breakup of melt jets in water is investigated in the DEFOR experiments at KTH. Present results indicate that porosities in the debris might be much higher than previously assumed, which would strongly support attainment of coolability. Calculations have been performed with IKEJET/IKEMIX describing jet breakup, mixing and settling of resulting particles. Models about debris bed formation and porosity are developed at KTH. The codes have been applied to reactor conditions for analysing the potential for coolability in the different phases of a severe accident. Calculations have been performed with WABE (MEWA) implemented in ATHLET-CD and with ICARE/ICATHARE for degraded cores and debris beds in the lower plenum, under reflooding and boil-off. Ex-vessel situations have also been analysed. Strong effects of lateral water inflow and cooling by steam in hot areas have been demonstrated. In support, some typical basic configurations have been analysed, e.g. configurations with downcomers considered as possible AM measures. Melt pool formation or coolability of particulate debris is a major issue concerning melt retention in the core and the lower head. Present conclusions from those analyses for adequate modelling in ASTEC are outlined as well as remaining uncertainties. Experimental and analysis efforts and respective continued joint actions are discussed, which are needed to reach resolution of the coolability issue.

THE SPLASH SURVEY: A SPECTROSCOPIC PORTRAIT OF ANDROMEDA’S GIANT SOUTHERN STREAM

The giant southern stream (GSS) is the most prominent tidal debris feature in M31's stellar halo. The GSS is composed of a relatively metal-rich, high surface-brightness "core" and a lower metallicity, lower surface brightness "envelope." We present Keck/DEIMOS spectroscopy of red giant stars in six fields in the vicinity of M31's GSS and one field on Stream C, an arc-like feature on M31's SE minor axis at R=60 kpc. Several GSS-related findings and measurements are presented here. We present the innermost kinematical detection of the GSS core to date (R=17 kpc). This field also contains the continuation of a second kinematically cold component originally seen in a GSS core field at R=21 kpc. The velocity gradients of the GSS and the second component in the combined data set are parallel over a radial range of 7 kpc, suggesting a possible bifurcation in the line-of-sight velocities of GSS stars. We also present the first kinematical detection of substructure in the GSS envelope. Using kinematically identified samples, we show that the envelope debris has a ~0.7 dex lower mean photometric metallicity and possibly higher intrinsic velocity dispersion than the GSS core. The GSS is also identified in the field of the M31 dSph satellite And I; the GSS in this field has a metallicity distribution identical to that of the GSS core. We confirm the presence of two kinematically cold components in Stream C, and measure intrinsic velocity dispersions of ~10 and ~4 km/s. This compilation of the kinematical (mean velocity, intrinsic velocity dispersion) and chemical properties of stars in the GSS core and envelope, coupled with published surface brightness measurements and wide-area star-count maps, will improve constraints on the orbit and internal structure of the dwarf satellite progenitor.

Macrolichen and bryophyte responses to coarse woody debris characteristics in sub-boreal spruce forest

Coarse woody debris (CWD) forms an important and specific habitat for many species of lichens, liverworts and mosses. We studied the relationships of 88 macrolichen and bryophyte species to CWD characteristics in mature mesic sub-boreal spruce forests in north central British Columbia. CWD characteristics and macrolichen and bryophyte species richness and abundance data were collected. Ordination, regression tree analysis and indicator species analysis were used to establish relationships between selected CWD variables and macrolichen and bryophyte species assemblages, overall species richness and individual species presence and abundance. Decay class and height from ground were the two CWD characteristics that most influenced macrolichen and bryophyte communities. Species composition varied along a continuum of assemblages from a dominance of arboreal lichens on decay class 1 (less decayed) CWD, to Cladonia, Dicranum and Brachythecium species and a diversity of liverworts on decay class 3, to feathermosses and Plagiomnium and Peltigera species on decay class 4 (more decayed) CWD. The height from ground of a log influenced the growth of liverwort and moss species with restricted growth on logs over about 10 cm above the ground. Log species, bark cover and diameter showed more limited influence on community composition in this study. Species were not greatly influenced by aspect (northern versus southern log aspect); however, macrolichen and moss species were more common on the upper sides of logs and several liverwort species were restricted to the lower sides of CWD (upper versus lower sides of logs). These results provide insight into the relationships between CWD characteristics and macrolichen and bryophyte communities, provide a basis for examining forest management impacts on lichen and bryophyte composition and highlight the importance of maintaining a diversity of CWD on the landscape.

The lentic–lotic character of Mediterranean rivers and its importance to aquatic invertebrate communities

Hydromorphological features are crucial in structuring habitats for freshwater organisms. The quantification of these variables is often performed through accurate measuring or detailed estimation, but their assessment is not always feasible for river management purposes. Economic and time constraints often lead to difficulty in creating simple summaries of collected data for practical use. The Lentic–lotic River Descriptor (LRD) was developed to identify the character of a river site in terms of local hydraulic conditions. Information about the presence of flow types, channel substrates, in-stream vegetation, organic debris and artificial features is included in its calculation. The main aim of this paper is to investigate whether the lentic–lotic character of a river site, as summarized with the LRD descriptor, is relevant to aquatic invertebrate communities in nearly natural river sites. Invertebrate data were collected with multi-habitat, proportional sampling and hydromorphological information was gained by applying the CARAVAGGIO method (river habitat survey technique) in the field. The dataset was generated from High or Good ecological status river sites located in Mediterranean areas of Italy. Correspondence Analysis was performed to relate the invertebrate community structure to a set of catchment-scale, reach-scale and chemical environmental variables. The results of the multivariate analysis indicate that LRD provides a persuasive explanation of the most important axis of variation in benthic data. This paper also presents the optimal LRD range for a set of invertebrate taxa, accompanied by a short discussion of their potential use in conservation issues.

THE DOMINANCE OF METAL-RICH STREAMS IN STELLAR HALOS: A COMPARISON BETWEEN SUBSTRUCTURE IN M31 AND ΛCDM MODELS

Extensive photometric and spectroscopic surveys of the Andromeda galaxy (M31) have discovered tidal debris features throughout M31's stellar halo. We present stellar kinematics and metallicities in fields with identified substructure from our on-going SPLASH survey of M31 red giant branch stars with the DEIMOS spectrograph on the Keck II 10-m telescope. Radial velocity criteria are used to isolate members of the kinematically-cold substructures. The substructures are shown to be metal-rich relative to the rest of the dynamically hot stellar population in the fields in which they are found. We calculate the mean metallicity and average surface brightness of the various kinematical components in each field, and show that, on average, higher surface brightness features tend to be more metal-rich than lower surface brightness features. Simulations of stellar halo formation via accretion in a cosmological context are used to illustrate that the observed trend can be explained as a natural consequence of the observed dwarf galaxy mass-metallicity relation. A significant spread in metallicity at a given surface brightness is seen in the data; we show that this is due to time effects, namely the variation in the time since accretion of the tidal streams' progenitor onto the host halo. We show that in this theoretical framework a relationship between the alpha-enhancement and surface brightness of tidal streams is expected, which arises from the varying times of accretion of the progenitor satellites onto the host halo. Thus, measurements of the alpha-enrichment, metallicity, and surface brightness of tidal debris can be used to reconstruct the luminosity and time of accretion onto the host halo of the progenitors of tidal streams.

Comparison of periprosthetic tissue digestion methods for ultra‐high molecular weight polyethylene wear debris extraction

There is considerable interest in characterization of wear debris from polyethylene (UHMWPE) bearing components used in total joint replacement. To isolate UHMWPE wear debris, tissue samples must be excised from regions adjacent to revised UHMWPE implant components, followed by exposure to one of many available tissue digestion methods. Numerous studies demonstrate successful digestion, but the relative efficiency of each method is not clear. The purpose of this study was to evaluate a variety of conditions for tissue digestion to provide a quantitative comparison of methods. Porcine and human hip tissues were exposed for 24 h to basic, acidic or enzymatic agents, filtered and digestion efficiency calculated based on the percentage of initial to final tissue weight. Of the conditions tested, 5 M NaOH, 5 M KOH, 15 M KOH or 15.8 M HNO(3) yielded the most complete porcine hip tissue digestion (<1% residual tissue weight; p < 0.05). Proteinase K and Liberase Blendzyme 3 did not effectively digest tissue in a 24 h period. Similar to results from the porcine dataset, human tissues digestion was most efficient using 5 M NaOH, 5 M KOH or 15.8 M HNO(3) (<1% residual tissue weight; p < 0.05). To verify that particle surface modifications did not occur after prolonged reagent exposure, GUR415 and Ceridust 3715 particles were immersed in each solution for 24 h. Overall, this study provides a framework for thorough and efficient digestive methods for UHMWPE wear debris extraction.

An initial evaluation of stable isotopic characterisation of post-blast plastic debris from improvised explosive devices

A number of two-way radios, similar to those which have been employed to initiate Improvised Explosive Devices (IEDs), were acquired from a commercial supplier and grouped into four pairs. Samples of plastic material were collected from five distinct regions of each radio and analysed by Infrared and Raman spectroscopy to identify the nature of the material. One radio of each pair was then subjected to detonation with a commercially available plastic explosive. The combination of radio and explosive was considered to be representative of the components of an IED. Following detonation, fragments were recovered and, where possible, identified as specific sampling points of the radio. A combination of delta2H and delta13C stable isotopic analysis of material from each of the five sampling points was found to provide a pattern which was characteristic of a given radio and provided a means to associate pairs of radios. When few fragments were recovered, no positive association could be made between the fragments and the paired, undamaged radio. This was attributed, in part, to manufacturing variation in the radios. However, when three or more post-blast fragments were recovered it was possible to associate these with the paired, undamaged radio with a high degree of certainty.

Characterisation of fretting-induced wear debris for Ti-6Al-4 V

The present work is related to the development of predictive methods for fretting wear which incorporate the effects of fretting wear debris. During the fretting process, debris is produced and accumulated within the contact region, reducing metallic contact between the contacting bodies. This paper describes the successful application of a nano-indentation technique to measure the mechanical characteristics of the debris layer and the alloy immediately below the debris layer, as produced from cylinder-on-flat fretting wear tests on Ti-6Al-4V. The test programme involved testing at different normal loads, strokes and numbers of cycles, to capture the evolution of the debris layer geometry, as well as the mechanical characteristics. Post-test examination of the fretting scars through the cross-section using optical and scanning electron microscopy suggests that the debris exists as an oxidised compacted layer structure. A scanning electron microscopy technique was developed to characterise the evolution of debris layer thickness distribution with numbers of cycles.

Tribological oxidation behaviour of PVD hard coatings

CrN, AlCrN and AlTiN coatings were prepared by the multi-arc ion plating technique. Ball-on-disc wear tests of the coatings were performed on a CETR UMT-2 tribometer, using 4 mm diameter Si 3N 4 ball as counterpart. The wear scars of the coatings were evaluated by surface profilometer, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDX), micro-area X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The tribological oxidation behaviour of the coatings was discussed in detail by combining the friction and wear properties. The results showed that the AlCrN coating exhibited higher hardness, but lower wear resistance as compared to the CrN coating. The AlCrN coating formed by CrN alloying with aluminum would show significantly improvement in high temperature oxidation resistance but not necessarily in wear resistance under the condition of ambient temperature. The difference between the wear morphologies of the AlCrN and AlTiN coatings mainly resulted from their different debris removal behaviour, which can be fundamentally attributed to the different characteristics of the wear debris. The tribochemically formed Cr 2O 3 exhibited better tribological properties than the TiO 2, and thus the AlCrN coating exhibited higher debris removal efficiency and better wear resistance than the AlTiN coating. The relative hardness of the three coatings did not predict their relative wear resistance in this study. The wear resistance of these three coatings was significantly dependent on their tribological oxidation behaviour and chemical composition. The tribological oxidation behaviours had great influence on the wear mechanism and the debris removal behaviour of the coatings, which would finally significantly affect the tribological properties of the coatings.