Incident Energy Levels Research Articles

Compression behavior of the CFRP square tubes after low‐velocity impact

AbstractThis work investigates the impact resistance and compression after impact (CAI) strength of carbon fiber‐reinforced polymer (CFRP) square tubes with varying wall thicknesses and diameters. Low‐velocity impact (LVI) tests are conducted on CFRP square tubes with three wall thicknesses and diameters at four incident energy levels, followed by compression tests on the impacted specimens. The results, including impact response history and failure morphology captured by the digital image correlation (DIC) technology, reveal that augmenting the wall thickness of CFRP square tubes substantially boosts their impact resistance and load‐bearing capabilities, evidenced by a remarkable 176.17% enhancement in CAI strength when the wall thickness is increased from 1.5 to 2.5 mm under a 20 J impact energy. Conversely, enlarging the diameter tends to diminish rigidity and impact resistance; however, it marginally augments CAI strength and residual strength.Highlights CAI strength of CFRP square tubes with varying geometries was investigated. DIC graph providing a comprehensive understanding of failure mechanisms. Failure mode was distinguished based on the low‐velocity characterization.

Metode Kurva Batasan Energi Untuk Evaluasi Resiko Arc-flash Pada Sistem PLTU

In an effort to determine the Personal Protective Equipment (PPE) required to protect against arc-flash hazards based on IEEE Std. 1584-2002, a simplified analysis technique was used with the energy limit curve method. The problem addressed was the potential inaccuracies in determining the required PPE level and maximum flash-protection distance when the traditional method does not precisely calculate the incident energy level and flash-protection limit. The purpose of this study was to evaluate a method that could be applied to various types of overcurrent protective devices in electrical systems, thus simplifying the arc-flash analysis. The method involved using the energy limit curve, which allows for quicker determination of the necessary PPE by plotting relay/fuse curves into the energy limit curve. This approach was implemented and tested at PLTU Paiton Unit 7 (PT. POMI). Important findings indicated that the energy limit curve method significantly reduced the time required to determine the appropriate PPE category compared to the IEEE 1584-2002 standard. The results showed that the process of determining the PPE category was more efficient, with fewer data requirements and shorter calculation times. The implications of this research suggest that the energy limit curve method can simplify arc-flash calculations for large industries with numerous buses, enhancing the overall safety protocols by providing a faster and potentially more accurate means of assessing arc-flash hazards and PPE requirements.

PREVENTING AND MINIMIZING ARC FLASH RISK IN POWER SYSTEM NETWORK

Arc flash events have resulted in several accidents due to faults in electrical equipment that lead to a significant release of energy. This event is a hazard and threat to the Power System Security and due to the large energy release, plasma is generated, as pressure increases since it causes physical damage to equipment while life of system operators within the vicinity of its occurrence are at risk. Although arc flash is one of the electrical safety programs that have been in existence, arc flash hazard was not adequately addressed until recently. However, the Electric Arc phenomenon is relatively new in the Nigerian power industry, there are certain aspect that are yet to be treated by the available literature, hence it is the duty of this work to establish model for addressing the observed lapses. The design is adequately prepared for the power system security analysis using typical scenarios in industrial facilities that are prone to yield high incident energy levels. In line with the foregoing, the developed methodology is validated using a segment of the Nigerias power industry as case study.

Reprocessed Materials Used in Rotationally Moulded Sandwich Structures for Enhancing Environmental Sustainability: Low-Velocity Impact and Flexure-after-Impact Responses.

In the rotational moulding industry, non-used, scrap, and waste purge materials have tremendous potential to be reprocessed and applied in skin-foam-skin sandwich structures to replace and reduce the use of virgin polymers. This approach not only encourages the re-use of these waste materials but also significantly contributes to reduce environmental impacts associated with the use of virgin polymers in this sector. The demand of rotationally moulded sandwich structures is rapidly increasing in automotive, marine, and storage tanks, where investigating their impact and after-impact responses are crucial. Hence, this study investigated the low-velocity impact (LVI) and flexure-after-impact (FAI) responses of rotationally moulded sandwich structures manufactured using reprocessed materials. Results obtained from LVI induced damage at two different incident energy levels (15 J, 30 J), and the residual flexural strength of impacted structures evaluated by three-points bending tests were compared with non-reprocessed sandwich structures (virgin materials). The impact damage progression mechanism was characterized using the X-ray micro-computer-tomography technique. Reprocessed sandwiches demonstrated 91% and 66% post-impact residual strength at 15 J and 30 J respectively, while for non-reprocessed sandwiches, these values were calculated as 93% and 88%. Although reprocessed sandwich structures showed a lower performance over non-reprocessed sandwiches, they have a strong potential to be used in sandwich structures for various applications.

Impact damage to fibre metal laminates under compression loading

The effect of in-plane compression loading on the low energy impact response of fibre metal laminates (FML) is investigated. A GLARE®-like FML consisting of bonded layers of aluminium alloy and glass-epoxy composite was impacted at different incident energy levels (up to ∼20 J) while under different axial compression strain levels (up to 8000 μe). Experimental testing and finite element (FE) analysis reveal that compression preloading increases (up to 50%) the maximum impact force experienced by the FML due to shortening of the impact contact time. The out-of-plane deformation of the FML, the amount of plasticity damage to the aluminium layers, and the shape and size of delamination damage to the glass-epoxy layer are dependent on the compression strain level. The FE model predicted the impact response and impact damage to the FML. The FE model is a validated numerical tool to analyse the low energy impact response of FMLs used in compression load-bearing structures.

Effect of Fibre Orientation on Impact Damage Resistance of S2/FM94 Glass Fibre Composites for Aerospace Applications: An Experimental Evaluation and Numerical Validation.

This study aims to investigate the influence of fibre orientation and varied incident energy levels on the impact-induced damage of S2/FM94, a kind of aerospace glass fibre epoxy/composite regularly used in aircraft components and often subjected to low-velocity impact loadings. Effects of varying parameters on the impact resistance behaviour and damage modes are evaluated experimentally and numerically. Laminates fabricated with four different fibre orientations , , and were impacted using three energy levels. Experimental results showed that plates with unidirectional fibre orientation failed due to shear stresses, while no penetration occurred for the and plates due to the energy transfer back to the plate at the point of maximum displacement. The impact energy and resulting damage were modelled using Abaqus/Explicit. The Finite Element (FE) results could accurately predict the maximum impact load on the plates with an accuracy of 0.52% to 13%. The FE model was also able to predict the onset of damage initiation, evolution, and the subsequent reduction of the strength of the impacted laminates. The results obtained on the relationship of fibre geometry and varying incident impact energy on the impact damage modes can provide design guidance of S2/FM94 glass composites for aerospace applications where impact toughness is critical.

Laser Surface Modification of Powder Metallurgy-Processed Ti-Graphite Composite Which Can Enhance Cells' Osteo-Differentiation.

The paper examines the surface functionalization of a new type of Ti-graphite composite, a dental biomaterial prepared by vacuum low-temperature extrusion of hydrogenated-dehydrogenated titanium powder mixed with graphite flakes. Two experimental surfaces were prepared by laser micromachining applying different levels of incident energy of the fiber nanosecond laser working at 1064 nm wavelength. The surface integrity of the machined surfaces was evaluated, including surface roughness parameters measurement by contact profilometry and confocal laser scanning microscopy. The chemical and phase composition were comprehensively evaluated by scanning electron microscopy, energy-dispersive X-ray spectroscopy and X-ray diffraction analyses. Finally, the in vitro tests using human mesenchymal stem cells were conducted to compare the influence of the laser processing parameters used on the cell’s cultivation and osteo-differentiation. The bioactivity results confirmed that the surface profile with positive kurtosis, platykurtic distribution curve and higher value of peaks spacing exhibited better bioactivity compared to the surface profile with negative kurtosis coefficient, leptokurtic distribution curve and lower peaks spacing.

Synchrotron diffraction characterization of dislocation density in additively manufactured IN 718 superalloy

In the present study, 3-dimensional (3D) parts of Inconel 718 (IN 718) have been fabricated using laser powder bed fusion (L-PBF) processing. Synchrotron diffraction experiments have been carried out on 0.5 mm thick specimens extracted from the as-built 3D parts at an incident energy level and wavelength of 30.05 keV and 0.41377 Å, respectively. The dislocation density ( ρ ) of additively manufactured IN 718 superalloy (AM IN 718) has been characterized using modified Warren-Averbach methodology. Fourier transformation of the synchrotron diffraction data corresponding to the first six reflections i.e., 111, 200, 220, 311, 222 and 400 and using its Fourier coefficients considering modified Warren-Averbach methodology enabled the evaluation of ρ . The ρ in conventionally processed wrought IN 718 (W IN 718) has also been characterized to compliment the results of AM IN 718. The synchrotron diffraction data was also studied considering classical Williamson-Hall and modified Williamson-Hall methodology to understand the influence of strain anisotropy on the peak broadening. The ρ was found to be very high (1.85 ± 0.24 × 10 15 m −2 ) in AM IN 718 which corroborated well with the dislocation substructure observed using transmission electron microscope (TEM). The average dislocation contrast factor ( C ¯ ), as a part of modified Williamson-Hall methodology, was found to account for the strain anisotropy in both AM and W IN 718. • 3D parts of IN 718 have been fabricated using laser powder bed fusion processing. • Dislocation density was characterized using modified Warren-Averbach methodology. • Dislocation character was identified using modified Williamson-Hall methodology. • Additively manufactured IN 718 contains high dislocation density (1.85 × 10 15 m −2 ). • Additively manufactured IN 718 contains high fraction of edge dislocations.

Influence of Incident Energy on Sisal/Epoxy Composite Subjected to Low Velocity Impact and Damage Characterization Using Ultrasonic C-Scan

Impact resistance is an inevitable characteristic of the composites employed in the high performance structural applications. Due to the growing interest in the use of sisal fibre as reinforcement in the polymer composites, it is required to determine the response of sisal/epoxy composites to low velocity impact at high incident energies where perforation can occur and assess the damage characteristics using a non-destructive technique. In this work, sisal/epoxy composites were subjected to drop weight impact in the velocity range of 3 m/s to 5 m/s at different energy levels between 20 J to 50 J according to the ASTM D7136. Based on the results observed, it is concluded that both the peak load and absorbed energy increased with the increasing incident energy level up to 40 J. At 50 J, perforation occurred and the maximum deformation was approximately 22 mm for the sisal/ epoxy composite. Damage characteristics and failure behaviour of the composite at different incident energies was examined from the visual images of the front and back face of the composite. The quantitative assessment of crack propagation in the sisal/epoxy composite and the damage area were determined from the ultrasonic C-scan images of the sample post impact at various energy levels.

異なる土壌水分および日射条件に対する葉のクロロフィル含量，クロロフィルa/b比および葉面積の変化

異なる土壌水分および日射条件に対する葉のクロロフィル含量，クロロフィルa/b比および葉面積の変化

Impact damage tolerance of energy storage composite structures containing lithium-ion polymer batteries

Multifunctional composite structures that combine high load-bearing properties with electrical energy storage capacity have potential application in electric and hybrid powered cars, and therefore must be impact resistant in the event of collision. This paper examines the effect of low velocity impact on the damage, compression properties and energy storage capacity of composite laminates and sandwich composites containing an embedded lithium-ion polymer (LiPo) battery. The impact responses of a carbon fibre-reinforced epoxy (CFRP) laminate and a polymer foam core sandwich composite are investigated. The materials were impacted at different incident energy levels at the location immediately above the embedded battery. The battery at the impact location increased the impact energy absorption of both the laminate and sandwich composite due to its capacity to yield and plastically deform. Impact-induced damage reduced the compressive properties of the composite laminate and sandwich composite in part due to deformation, cracking and debonding of the battery. Low impact energy events (≤4 J) had negligible effect on the residual energy storage capacity of the LiPo battery, although higher energies (≥6 J) caused an internal short circuit due to excessive plastic deformation and crushing.

Investigation of Arc Flash in Single-Phase Vertical Conductors in a Box

NFPA 70E and IEEE 1584 are defining standards for arc flash hazard analysis. Both assume three-phase faults for calculations since three-phase power distribution is predominant in utility and industrial applications; however, arc flash in single-phase systems is excluded. Single-phase faults to neutral or ground or single phase-to-phase faults can occur in a variety of circumstances. Such events may have the potential to produce arc flash and blast that would pose a significant safety concern. This paper describes a recent doctoral research investigation of arc flash in one single-phase configuration. Experiments were sponsored by UL and performed at the Schneider Electric High-Power Laboratory in Cedar Rapids, Iowa. This facility provided a test article; a full suite of voltage, current, and temperature instrumentation; and high-speed video recording. Experimental work revealed incident energy values less than 0.2 cal/cm2 for 240-volt single-phase arc fault events though there was still significant flash and splatter of molten wire residue. 480 V single-phase events produced an order of magnitude greater heat energy, and at 22 kA sustained arcing until interrupted by the test cell controller. Results suggest that 240 V single-phase panels and equipment common in residential and light commercial applications may be at very low risk of yielding arc flash burn-related injuries. However, 480 V single-phase faults can produce levels of incident heat energy known to cause burns, flash, and blast pressure at available fault currents between 10 and 22 kA.

Application of Incident Energy Reference Boundary Area Plots in TCCs Considering IEEE 1584-2018 Input Parameter Variability

A simplified arc-flash analysis technique that allows for the determination of the settings of overcurrent protective devices and selection of arc-rated personal protective equipment (PPE) based on a reference constant incident energy boundary area is presented in this article. The reference areas are created based on the equations of IEEE Standard 1584-2018 [1], taking into consideration potential variation in the input parameters described in the standard. The method presented in this article provides an efficient and straightforward means to simultaneously consider the effects of varying input parameters on arc-flash calculation results by plotting areas of constant incident energy on a time–current plot. Actual power distribution equipment may have multiple electrode configurations, gaps between conductors, operating voltages, as well as a range of available bolted short-circuit currents and variation in the size of equipment enclosures. The multiple combinations require dozens of simulations to determine the worst-case incident energy levels. Unlike previous implementations of incident energy curves, which were typically single line representations of the incident energy, the plotting of bounded areas (C-area plots) allows for multiple parameter sweeps to determine a band of variation within a defined set of parameter combinations.

A three-dimensional laboratory investigation of beach morphology change during a storm event

This study provides laboratory observations of the nearshore hydrodynamics and detailed topographic surveys associated with the morphological response of a beach-dune system to oblique waves during a storm event. A physical model consisting of a 20 m long sandy steep beach constructed in a wave basin, and a wave paddle oriented obliquely to the beach shoreline is used to generate irregular waves at the offshore boundary. In the experiment, the wave height is varied over time in five segments to simulate the change in the energy from a passing storm and is varied alongshore to initiate an alongshore gradient in waves and wave-driven currents. To simulate a constant storm surge, a high mean water level relative to the dune is used, enabling waves to reach the dune toe. The results indicate the formation and evolution of a beach scarp. The retreat of the scarp initially corresponds to time-varying wave energy, but becomes controlled by the changing nearshore beach slope over time. The alongshore current magnitude is governed by the spatio-temporal variability in wave energy and is the main driver of sediment flux. The sand that is eroded from the dune initially deposits at the dune toe when nearshore circulation is weak. However, as the wave energy increases sediment is transported along the beach and is deposited, increasing the surf zone width. The experimental results indicate that small waves at high water levels relative to the dune can drive the formation of a beach scarp. In addition, different levels of incident wave energy drive different rates of sediment transport and morphological evolution with high alongshore variability throughout a storm event.

Enhancing Worker and Equipment Protection Through Passive Arc-Fault Mitigation

Existing arc flash standards like IEEE 1584 and 1584.1 present models that can be used to estimate incident energy levels in power distribution equipment but provide limited direction regarding how equipment construction should be considered in the calculations. Users performing arc flash risk assessments are left to apply engineering judgment when considering how barriers or isolation of components should be considered. This can lead to risk assessments that are inconsistent or incorrect. Current practices regarding arc flash evaluation in barriered and nonbarriered equipment are reviewed based on current standards. Gaps and potential concerns are discussed, including the lack of defined criteria to use in calculations, along with lack of criteria for determining when barrier systems are considered effective at preventing, mitigating, controlling, or containing arcing faults. A description of a new system that provides passive protection in low-voltage distribution equipment is presented. By providing improved protection for the incoming conductors and main circuit breaker itself, this line-side protection system reduces or eliminates the uncertainties, which allows for more consistent and accurate application of risk assessments. The new protection system enables arc flash protection to be provided by a passive, enclosed system that has been tested to verify performance. As such, the calculations and risk assessment are less reliant on assumptions regarding the performance of the equipment. Practical aspects of arc flash analysis and labeling and operation and maintenance of such equipment are also discussed.

Influence of Water Absorption on the Low Velocity Falling Weight Impact Damage Behaviour of Flax/Glass Reinforced Vinyl Ester Hybrid Composites.

Due to rigorous new environmental legislations, automotive, marine, aerospace, and construction sectors have redirected their focus into using more recyclable, sustainable, and environmentally friendly lightweight materials driven by strengthening resource efficiency drive. In this study, the influence of moisture absorption on flax and flax/glass hybrid laminates is presented with the aim to investigating their low velocity impact behaviour. Three different types of composite laminates namely, flax fibre reinforced vinyl ester, flax fibre hybridised glass fibre and glass fibre reinforced vinyl ester composites were fabricated using resin infusion technique. The moisture immersion tests were undertaken by immersing the different specimens in sea water bath at room temperature and 70 °C at different time durations. The low velocity falling weight impact testing was performed at 25 Joules of incident energy level and impact damage behaviour was evaluated at both ageing conditions using scanning electron microscopy (SEM) and X-ray microcomputed tomography (micro CT). The percentage of moisture uptake was decreased for flax vinyl ester specimens with glass fibre hybridisation. The maximum percentage of weight gain for flax fibre, flax/glass hybrid and glass fibre reinforced composites immersed at room temperature for 696 h is recorded at 3.97%, 1.93%, and 0.431%, respectively. The hybrid composite exhibited higher load and energy when compared flax/vinyl ester composite without hybridisation, indicating the hybrid system as a valid strategy towards achieving improved structural performance of natural fibre composites. The moisture absorption behaviour of these composites at room was observed to follow Fickian behaviour.

A practical solution of the Bethe equation in the energy range applicable to radiotherapy and radionuclide production

While the dose deposition of charged hadrons has received much attention over the last decades starting in 1930 with the publication of the Bethe equation, there are still practical obstacles in implementing it in fields like radiotherapy and isotope production on cyclotrons. This is especially true if the target material consists of non-homogeneous materials, either consisting of a mixture of different elements or experiencing phase changes during irradiation. While Monte-Carlo methods have had great success in describing these more difficult target materials, they come at a computational cost, especially if the problem is time-dependent. This can greatly hinder optimal advancement in therapy and isotope targetry. Here, a regular perturbation method is used to solve the Bethe equation in the limit of small relativistic effects. Particular focus is given to incident energy level relevant to radionuclide production and radiotherapy applications, i.e. 10–200 MeV. We present a series solution for the range and dose distribution in terms of elementary functions, as opposed to special functions which will aid in uptake by practitioners.

The effects of water content and external incident energy on coal dynamic behaviour

Water content and incident energy are important factors in influencing the mechanical properties and stress field of coal seam, which are closely related to the dynamic disaster intensity. In this study, after doing some static compression tests in different water content, comprehension dynamic compressive tests on pre-stressed coal specimens under different water contents and incident energy levels were conducted using a modified Split Hopkinson Pressure Bar test system. The effects of water contents and incident energy levels on dynamic behavior of the studied coal were evaluated by analysis of dynamic stress-strain curves, inspection of the occurred damage and in-situ test on the mine site. For detail analysis, some indices including peak strength, elastic modulus, dissipation energy, impact energy index, and failure characteristics were employed. The results indicated that dynamic strength and elastic modulus are negatively correlated with the water content and positively correlated with the incident energy. Two types of the dynamic failure behavior including incident energy-dominated failure and incident energy-induced failure were analyzed based on dissipation energy and stress-strain curve types. The coal burst occurrence possibility was proposed according to the dissipation energy density. Finally, based on laboratory test results and field engineering practices, the dynamic disaster mechanisms and their respective prevention concepts were further discussed.

Damage investigation and assessment due to low-velocity impact on flax/glass hybrid composite plates

There is limited information available in the body of knowledge regarding to the low velocity impact damage characteristics of sustainable bio-based such as flax fibre reinforced composites. This paper presents the results of full investigation of impact damage mechanisms on flax/vinyl ester laminated composite and flax-glass/vinyl ester hybrid composite laminates caused by low-velocity impact using a drop weight impact machine. The specimens were subjected to incident energy levels of 25 J and 50 J, in order to achieve a damage up to perforation and complete penetration. A 3D Finite Element Analysis (FEA) model was also developed using Hashin failure criteria. The damage and the predicted delaminations were compared using a high-resolution micro-Computed Tomography (μ-CT) technique. The results of the numerical analysis correlated well with the experiments and the imaging, which provided a full verification of the exact position of delaminations due to impact within the composite laminates.

Influence of patch lay-up configuration and hybridization on low velocity impact and post-impact tensile response of repaired glass fiber reinforced plastic composites

This paper aims to investigate the effect of homogenous and hybrid external patches based on plain weave woven glass and Kevlar fabric on low velocity impact and quasi-static tensile after impact response of adhesively bonded external patch repairs in damaged glass/epoxy composite laminates. In all hybrid patches, the proportion of Kevlar and glass fibers were equal (i.e. 50% of Kevlar and 50% of glass by volume fraction), while lay-up configuration was different. This further enables to study the associated effect of hybridization and lay-up configuration on impact response of the repaired laminates. The intent of using hybrid external patches is to combine the excellent high displacement-to-failure property of Kevlar fiber as a ductile reinforcement with the superior mechanical property of glass fiber as a brittle reinforcement. The effect of glass/Kevlar content on impact response and tensile after impact response was investigated for various incident impact energy levels, such as 2, 4, 6, and 8 J. Results showed that hybridization and lay-up configurations of the external patches played a significant role on low velocity impact and quasi-static tensile after impact response of the repaired glass/epoxy specimens. Specimens repaired using intra-ply hybrid patches showed better impact properties and damage tolerance capability than that of the virgin and other repaired specimens. In specific, the use of intra-ply hybrid patches reduced the impact energy absorption by 10.17% in comparison to the virgin specimens at impact energy of 8 J.