Debris Impact Research Articles

Debris impact forces on flexible structures in extreme hydrodynamic conditions

Field surveys of recent major flood events have emphasized the need for an in-depth examination of debris loading. Debris loading occurs when solid objects entrained within the flow interact with a structure in its movement path, exerting loads through direct impacts or damming. Until now, the focus of research into debris impacts has concentrated on single debris impacting a rigid structure. This study extends to examining the influence of debris impacting a flexible structure. A two degree-of-freedom (2DOF) system was used to model the debris–structure interaction. The model is compared with two experimental data sets using a rigid body and the effective stiffness model. The proposed 2DOF model was shown to be more accurate in estimating the impact force than those to which it was compared to. However, due to difficulties in estimating the stiffness and inertia of the structure and the debris, the proposed model under predicted the maximum measured impact loads. The effective stiffness model was shown to represent the maximum measured impact loads, and should therefore be implemented in the design process when considering debris impacts on flexible structures.

Kebijakan Strategis Mitigasi Ancaman Peredaran Orbit Satelit terhadap Keamanan Nasional: Pendekatan Analytical Hierarchy Process

The threat of circulating space orbit is considered by some to be a threat to the national security of one country, because the potential dangers such as space junk produce significant damage to affected areas. But until now Indonesia, despite ratifying the UN convention on space, does not yet have a comprehensive mitigation strategy. This study aims to create policy scenarios in mitigating the threat of satellite orbit circulation so that it can be used as an alternative policy formulation for relevant institutions. The research method is carried out with a mix method approach that is adjusted to each research objective such as using literature study and AHP analysis. AHP analysis shows that respondents want international cooperation to be built, both bilateral and multilateral cooperation must prioritize national security while upholding the values of friendship and mutual respect. Comprehensive space debris mitigation policies need to be formulated and defined as the basis for action. Considering that the impact of space debris is very dangerous and massive, the use of space technology is a necessity to be used to anticipate, deal quickly and minimize the impact of the disaster.

Behavior of dragon skin flexible metal bumper under hypervelocity impact

The need for large space structures has been of significant interest in recent years, owing to the expansion of potential space applications. The use of flexible and inflatable shield designs is a very promising method for constructing spacious structures in space. Dragon skin or so-called fish-scale armor may provide an effective flexible bumper structure for space. This is the first study to evaluate dragon skin as a bumper against hypervelocity impact of micro-meteoroid and orbital debris in space. In this research, hypervelocity impact experiments and various numerical simulations were conducted. It was found that the deflection effect and critical impact location factor prevailed in the dragon skin bumper; hence, fragmentation can be seriously affected by the dragon skin shape. However, a simulation work of the research showed that the shape effect can be alleviated by using a thin and dense metal material instead of aluminum. In conclusion, the dragon skin structure can be utilized as a bumper in space with consideration of several design factors that are reported in this study.

Are our beaches safe? Quantifying the human health impact of anthropogenic beach litter on people in New Zealand

The environmental, social and cultural importance of beaches permeates human society, yet the risk of human injury associated with increasing exposure to anthropogenic beach litter remains an unknown. While the impact of marine debris and beach litter on marine and coastal fauna and flora is a widely reported global issue, we investigate the impact on human health in New Zealand. Anthropogenic beach litter is ubiquitous, few beaches remain pristine, which consequently influences tourist choices and potentially negatively interacts with humans. Human impacts are not well-investigated, with no quantitative studies of impact but many studies qualitatively inferring impact. New Zealand has a socialised medical system allowing a quantitative, decadal assessment of medical insurance claims to determine patterns and trends across ecosystems and causes. We demonstrate for the first time that anthropogenic beach litter poses a common and pervasive exposure hazard to all ages, with specific risk posed to young children. The New Zealand system allows these hazards to be investigated to determine the true effects and costs across a nation, providing an evidence base for decision-makers to address this ubiquitous environmental issue.

Investigation of concrete-filled steel tube beams strengthened with CFRP against impact loads

As a promising strengthening solution, carbon fiber reinforced polymer (CFRP) sheets have been used to improve the structural response of concrete-filled steel tubes (CFSTs) in service loads, owing to the durability and high strength-to-weight ratio provided by CFRP. Despite the wealth of knowledge available in the literature on how CFRP sheets contribute to strengthening CFSTs under static loads, there is a research gap regarding how the strengthened structural components respond to lateral impact loads, due to vehicle and vessel collision, as well as wind and water-borne debris impact. This was the motivation of the current study to establish a computational framework supported by experimental tests to evaluate the performance of CFST beams with and without CFRP under a set of impact scenarios. For this purpose, a range of influential aspects related to CFRP, concrete, and steel, as well as impact energy, are investigated. Such a holistic assessment provides unique information to answer fundamental and practical questions regarding the use of CFRP for strengthening of CFST beams against impact loads. To further assist with the proper configuration of CFRP-strengthened CFST beams, a section analysis method is developed and validated as the outcome of this study.

Debris impact under extreme hydrodynamic conditions part 2: Impact force responses for non-rigid debris collisions

Historical tsunami events have resulted in extreme damage to coastal regions worldwide. Among the various loads associated with tsunami waves, debris impact has been shown to cause major damage to nearshore infrastructure. As a result, debris impact loads have been included prominently in existing design guidelines and standards, such as the FEMA P-646 [11] and ASCE7 Chapter 6 [6]. In the present study, single debris impacts on structures was experimentally investigated under tsunami-like wave conditions. Eccentric and oblique impacts of a model shipping container (length scale 1:40) on a non-rigid structure were examined. The experimental results of the non-rigid impacts are discussed in the context of the existing force equations which were derived under the assumption of rigid-body impact theory. As expected, the elasticity of the structure was determined to influence and, specifically, reduce the magnitude of the debris impact forces. Existing impact force equations are herein critically discussed through comparison with the experimental results and, finally, modifications to existing force equations to account for non-rigid collisions are proposed.

Debris impact under extreme hydrodynamic conditions part 1: Hydrodynamics and impact geometry

In field investigations of major flooding events, debris impact has been identified as a critical load and has thus been included in various building codes, such as FEMA P-646 and ASCE7. However, the evaluation of debris loading solely based on field data is challenging. Therefore, to address the uncertainties related to debris loading, an experimental program investigating debris impacts on structures was performed using a dam-break wave. The debris were down-scaled 6.1 m (20 ft) shipping containers (1:40 geometric scale) which were entrained and displaced by the transient wave conditions. The study presented here examines the influence of the transient flow conditions and the flow features around the structure due to the impinging wave on the debris impact conditions. The influence of the impact geometry (obliqueness, eccentricity) on the impact force is also discussed and possible parameters to describe the impact geometry are introduced.

Research on the Repair Performance of Self-Healing Aluminum Material Based on the Low Melting Point Slicker Solder Alloy

It is great significance to study self-healing aluminum alloy materials for spacecraft the structure protection from high energy space weapon attack and debris impact in future. In this paper, Using aluminum alloy (6063) as matrix material with low melting point alloy (Sn60Pb40, the melting point of 183°C) as repairing materials, the self-healing Aluminum Alloy material was designed and manufactured by the smelting and casting method. The crack damage repair performance of the self-healing Al alloy was researched through the experiment. The results show that the self-healing aluminum alloy has certain self-healing ability without help, when the temperature reaches the melting point temperature of Sn60Pb40. The repair time is about 20min, the crack filling rate can reach 84%. The research conclusion can provide a reference for the development of metal self-healing material technology.

Design-to-safety: Analysis of the explosion and fragmentation influence on inert debris impact footprints and mitigation solutions for innovative launcher concepts

The ever increasing price pressure on the worldwide launch market has shaped the strategy for the next generation of European launchers preparation. In addition to the development of low-cost propulsion technologies based on LOX/CH4, CNES Launchers Directorate, investigate the introduction of reuse of the main stage with a return phase performed by a Toss-Back maneuver, reducing overall costs.These launcher concepts, which have never been operated from French Guiana, give rise to new safety concerns different from those already handled for the launches operated from GSC, challenging the flight safety principles.This article provides an overview of the most critical scenarios, following an accidental explosion, in a Toss-Back maneuver, with an analysis of the effects of the resulting explosion (in terms of energy and fragmentation), and its impact on ground. The main goal is to identify the most critical parameters driving the scenarios’ criticality and to determine the possible risk mitigation measures such as “design-to-safety” solutions.

Cumulative distribution of ballistic impact failures of common twisted-pair data cables at orbital speeds

Data wire cable runs are a significant presence on the exterior of the International Space Station (ISS), and continued ISS mission support requires detailed assessment of cables due to micrometeoroid and orbit debris (MMOD) impact. These data wire cables are twisted-pair cables consisting of two 22AWG stranded conductors and fillers inside a tight fitting braided copper shield. The copper shield and its contents are covered with a jacket that has a nominal outer diameter of 3.76 mm and beta-cloth tape. The ISS engineering community has identified two loss-of-function mechanisms for these cables: open circuits due to severed conductors within the cable, and short circuits due to contact between conductors or grounded components. As these data cables are low power systems, short circuits are not expected to burn away the contact, so both open and short circuits are considered permanent loss-of-function for the cable. A total of ninety-seven impact experiments have been performed into these cables to develop a statistical model for the failure of these cables to be used in reliability studies. The experimental work has yielded cumulative distribution functions for these cables for steel and aluminum components of the orbital debris environment at representative speeds and impact obliquities.

Theoretical study of the performance of refractory materials for extreme conditions applications

Refractory metals are widely used in nuclear engineering and aerospace industry, due to their high resistance to extreme conditions, such as high temperatures, and wear. When used in this context, these materials are subjected to a flux of high-energy radiations that change their microscopic structure by means of the generation of a high number of defects. The production of defects can reach a dramatic amount, thus affecting the macroscopic properties of the material. It is crucial to understand the microscopic changes that occur in these materials, in order to enhance their performances and endurance. Damage production and displacement cascade take place in a very short time scale and are impossible to be studied directly with experimental techniques. Molecular Dynamics, operating in the nanometre scale and covering a time-scale that spans from tenths of femtoseconds up to nanoseconds, can provide a deep insight into the micro-structure of the materials in the first moments after the impact. Our study focuses on the analysis, at the atomic level, of the response of niobium as a reference refractory metal against the impact of a high-energy debris. The goal of this work is to prepare a computational set-up to give a preliminary insight on the behaviour of refractory metals and state their efficiency as shielding components in aerospace and nuclear industry. In the present work, we report preliminary results of damage response in niobium as shielding material, showing low energy dependence on dislocation density for debries energies over the 10 keV. Moreover, we present basis of our methodology and the interest of extending this study to further comparison with other refractory metals, like tungsten, tantalum, of industrial interest.

First data on plastic ingestion by blue sharks (Prionace glauca) from the Ligurian Sea (North-Western Mediterranean Sea)

Few studies have focused so far on plastic ingestion by sharks in the Mediterranean Sea. The aim of this paper was to determine, for the first time, the plastic litter ingested by blue sharks (Prionace glauca), categorized as “Critically Endangered” in the Mediterranean Sea by IUCN, caught in the Pelagos Sanctuary SPAMI (North-Western Mediterranean Sea). The analysis of the stomach contents was performed following the MSFD Descriptor 10 standard protocol implemented with FT-IR spectroscopy technique. The results showed that 25.26% of sharks ingested plastic debris of wide scale of sizes from microplastics (<5 mm) to macroplastics (>25 mm). The polyethylene sheetlike user plastics, widely used as packaging material, are the most ingested debris. This research raises a warning alarm on the impact of plastic debris on a threatened species, with a key role in the food web, and adds important information for futures mitigation actions.

Impacts of small woody debris on slurrying, persistence, and propagation in a low-gradient channel of the Dongyuege debris flow in Nu River, Southwest China

Debris flows occurring in well-vegetated alpine areas usually contain a range of sizes of woody debris. Large woody debris (LWD), which has a retaining effect on further transportation of debris downstream, is mainly distributed in upstream reaches, and the amount of small woody debris (SWD) deriving from LWD increases dramatically midstream and downstream. The Dongyuege (DYG) bouldery debris flow with a sandy-matrix took place in a wildwood area, causing 96 deaths and its clay-sized fraction does not contain typical clay minerals. However, its total travel distance and runout distance in a low-gradient reach (between 2° and 5°) upstream of the depositional fan apex reached 11 km and 3.3 km, respectively. The abundant SWD in the DYG debris flow might have played a crucial role in slurrying, persistence, and the long runout over the low gradient. To understand why this debris flow extended so far, slurrying experiments, pore water escape experiments, and excess pore pressure experiments were performed. Crude debris (CD) collected from the DYG debris flow deposit was used throughout the experiments, the tested materials of which are separated into CD-containing SWD with a maximum grain size (MGS = 2 mm), purified debris (PD) without SWD with a MGS of 2 mm, and SWD < 2 mm in diameter. In the five slurrying experiments with PD-SWD-water mixtures, as the SWD content was elevated from 0.0 to 2.0 wt%, the current velocity of escaping pore water decreased uniformly from 17.2 to 0.9 mm/s. When the SWD content was 1.0 wt% or greater, the mixtures can be considered as one-phase flows of viscous fluids. The six pairs of pore water escape experiments based on the slurries remolded with CD and PD, respectively showed that the time needed for pore water to escape from the CD slurries was much greater than those from their PD counterparts. Also, measured was the dissipation rate of the relative excess pore pressure of CD and PD slurries of various densities and volumes, which showed that most of the rates of the PD-slurries were always greater than CD-slurries. Overall, the results show that SWD has a strong influence on the slurrying of the DYG debris without typical clay minerals found in other debris flows, and SWD helps to sustain the high excess pore pressure in the interior of the debris flow mass which resulted in the extended travel distance over such a low gradient. SWD favors the formation and stability of one-phase water-debris mixtures because of its large specific surface area and low density, which makes it able to absorb fine particles and able to be suspended in slurry flows over long timescales. In well-vegetated mountainous areas, SWD should be taken into account in the assessment of debris-flow hazards.

Assessment of dynamic impact force of debris flow in mountain torrent based on characteristics of debris flow

Landslides and debris flows that occur around residential areas are considered, globally, as significant disasters that cause damage to human life and property. With terrain slope defining the flow characteristics of debris flows, flow depth, flow velocity, and impact force vary by time and distance. In particular, when a structure is located in the flow path of debris flows, the flow characteristics of debris flows vary by terrain slope and direction angle. To simulate the flow characteristics of these debris flows, the simulation results obtained by FLO-2D were analyzed with six-stage conditions for the research area. In the analysis, the flow depth, flow velocity, and impact force were estimated on the basis of the outlet of the research area in the presence and absence of structure(s) at certain distances. With this, the variation of the impact force in accordance with the variation of the flow depth of the debris flows was highly similar to the simulation results obtained by FLO-2D, when the correction index (α) of the suggested dynamic impact force equation was 0.3–0.4. There were sections where the estimated value of the impact force was overestimated near the outlet, and it was judged that the fixed values of the terrain factors (width, roughness coefficient, slope, etc.) caused the impact force to be overestimated. However, the correlation analysis showed that the correlation index was above the normal ranges in the suggested dynamic impact force equation for debris flows with the application of the terrain factors.

Study on the Technology of Laser-Driven Flyer Hypervelocity Launch

The outer surfaces functional materials of spacecraft are exposed to hypervelocity impacting of micro meteoroids and orbital debris in space. The laser-driven flyer (LDF) system can launch a speed of 3∼10km/s, a thickness of about 5um aluminum flyer under the experimental conditions. It can well simulate the effects of micrometer space debris impact on the outer surfaces functional materials of spacecraft. In this paper, the laser-driven flyer technique and flyer velocity measurement technique are introduced. The quantitative relationships between the flyer velocity and the laser energy, laser pulse width, and the flyer thickness were analyzed. The damage morphology and performance degradation of outer surfaces functional materials (such as K9 glass and OSR) of spacecraft were experimentally studied under the hypervelocity aluminium flyer impacting.

Debris impact analysis and mapping results for the rocket vehicle ALV

Debris impact analysis and mapping results for the rocket vehicle ALV

Toxicities of polystyrene nano- and microplastics toward marine bacterium Halomonas alkaliphila

Nano- and microplastics have been shown to cause negative effects on marine organisms. However, the toxicities of nano- and microplastics toward marine bacteria are poorly understood. In this study, we investigated the toxic effects of polystyrene nano- and microplastics on the marine bacterium Halomonas alkaliphila by determining growth inhibition, chemical composition, inorganic nitrogen conversion efficiencies and reactive oxygen species (ROS) generation. The results showed that both nano- and microplastics inhibited the growth of H. alkaliphila in high concentrations, while nanoplastics rather than microplastics influenced the growth inhibition, chemical composition and ammonia conversion efficiencies of H. alkaliphila at concentration of 80 mg/L. The ROS generation indicated oxidative stress induced by nano- but not microplastics, and the oxidative stress induced by nanoplastics may provide a significant effect on bacteria. Furthermore, the positively charged nanoplastics (amine-modified 50 nm) induced higher oxidative stress toward bacteria than that induced by negatively charged nanoplastics (non-modified 55 nm). The increased extracellular polymeric substances as evidenced by transmission electron microscope (TEM) observation suggested the possible bacterial protective mechanisms. The present study illustrates for the first time the impact of plastics debris on the inorganic nitrogen conversion efficiencies of marine bacteria. Our findings highlight the effects of microplastics on the ecological function of marine organisms.

A new test method to simulate low-severity wear conditions experienced by rubber tire materials

An innovative rotary tribometer was developed in order to reproduce the abrasive wear of reinforced rubber materials for tire. The device allows performing accelerated, quantitative friction and wear tests which mimic real usage conditions in terms of kinematics and dynamics of the contact, temperature and open cycle conditions, specifically in low severity conditions, which often represent a challenge to mimic and study. The specific point emphasized here is the strong impact of wear debris accumulated in the contact zone on the measured wear rate. To quantify this phenomenon, the amount of wear debris in the contact was varied by changing the frequency at which debris are eliminated. It was found that the presence of more debris in the contact zone generally decreases the wear rate. Two distinct types of wear debris were identified, which are likely to correspond to two distinct mechanisms of wear. Within a transitory period at the beginning of the tests, wear debris essentially consist in a sticky layer of soluble (thus de-crosslinked elastomer material). Further on, a steady regime (representative of wear in real low severity conditions) occurs, with a well established ridge pattern, in which the predominant wear mechanism consists in tearing away material fragments of micrometric sizes. The proposed test method allows discriminating quantitatively these mechanisms.

Biological Impact of Silicon Nitride for Orthopaedic Applications: Role of Particle Size, Surface Composition and Donor Variation

The adverse biological impact of orthopaedic wear debris currently limits the long-term safety of human joint replacement devices. We investigated the role of particle size, surface composition and donor variation in influencing the biological impact of silicon nitride as a bioceramic for orthopaedic applications. Silicon nitride particles were compared to the other commonly used orthopaedic biomaterials (e.g. cobalt-chromium and Ti-6Al-4V alloys). A novel biological evaluation platform was developed to simultaneously evaluate cytotoxicity, inflammatory cytokine release, oxidative stress, and genotoxicity potential of particles using peripheral blood mononuclear cells (PBMNCs) from individual human donors. Irrespective of the particle size, silicon nitride did not cause any adverse responses whereas cobalt-chromium wear particles caused donor-dependent cytotoxicity, TNF-α cytokine release, oxidative stress, and DNA damage in PBMNCs after 24 h. Despite being similar in size and morphology, silicon dioxide nanoparticles caused the release of significantly higher levels of TNF-α compared to silicon nitride nanoparticles, suggesting that surface composition influences the inflammatory response in PBMNCs. Ti-6Al-4V wear particles also released significantly elevated levels of TNF-α cytokine in one of the donors. This study demonstrated that silicon nitride is an attractive orthopaedic biomaterial due to its minimal biological impact on human PBMNCs.

Numerical and laboratory methods of tsunami waves modeling

Tsunami waves are one of the most destructive natural phenomena. The study and modeling of tsunami waves can allow us to reduce the number of human casualties and to minimize material damage in case of disaster. Tsunami waves modeling in laboratory conditions, in contrast to numerical simulation, allows us to obtain more reliable data. In numerical modeling it is impossible to take a large number of random parameters into account (the impact of large-sized debris on buildings and structures during the second and subsequent waves, for example). There are several methods to generate tsunami waves. In our studies, emphasis will be placed on the moving block method and the pneumatic wave generator method. In the moving block method, wave is generated after a solid or loose material collides with a water surface (the tsunami model, whose source is landslide). When using the pneumatic wave generator, a wave or series of waves are formed using a special laboratory installation. The laboratory installation consists of a wave tray or basin in which a tank is installed an open part to the surface of the water. Air from the tank is pumped out by the pump, and the water level in the tank gradually rises. Then with the help of air valves, the water is released and generates a wave. The shape and periodicity of the generated waves can be varied by means of the computer that controls the air valves. The data obtained during the research is necessary both for making corrections in the numerical tsunami models and for designing buildings and structures in tsunami-prone areas.