Specific Absorption Research Articles

Experimental and numerical study and multi-objective optimisation of quasi-static compressive test on three-dimensional printed lattice-core sandwich structures

This paper focuses on the energy absorption of additively-manufactured or 3D-printed lattice-core sandwich structures of different configurations. The rhombic dodecahedron lattice unit cell, which has been extensively investigated for energy absorption, is the starting point for this research. The compressive behaviour of 3D lattice structures with rhombic dodecahedron unit cells was examined at quasi-static loading along with the influence of the angle between struts, struts diameter, and the number of layers in the core. The angle between struts had the highest degree of influence on the specific energy absorption. The results showed that the diameter of struts has been the most influential parameter to increase mean and peak forces. The results of using the design expert software showed the optimal specific energy absorption and peak force to be 3.8779 J/gr and 3458.25 N, respectively.

Experimental researches on failure and energy absorption of composite laminated thin-walled structures

To research the failure of carbon fiber-reinforced composite laminated specimens, the tensile tests and compressive tests were conducted for [90]16 and [0]16 specimens, and the shear tests were conducted for [±45]4s specimens, and the microscopic failure mechanisms were observed by scanning electron microscopy. To research the failure and energy absorption of different thin-walled structures with different layups, the quasi-static axial crushing tests were conducted for [±45/0/0/90/0]s and [0/90]3s circular tubes, [0/90]3s and [±45]3s square tubes, [0/90]4s and [±45]4s sinusoidal specimens, and the internal failure were further investigated by 3D X-ray scan. Based on the load-displacement curves, the energy absorptions were evaluated and compared according to specific energy absorption and peak crushing force, and the relationships between failure modes and specific energy absorption, peak crushing force were further researched. The results show that the macroscopic failure modes are the collective results of varieties of microscopic failure mechanisms, such as fiber fracture, matrix deformation and cracking, interlamination and intralamination cracks, cracks propagation, etc. The [±45/0/0/90/0]s circular tube shows the transverse shearing failure mode with high specific energy absorption. The [±45]3s square tube and [±45]3s sinusoidal specimen show the local buckling failure mode with low specific energy absorption. The [0/90]4s sinusoidal specimen, [0/90]3s circular tube, and [0/90]3s square tube show the lamina bending failure mode with medium specific energy absorption. The failure mode of thin-walled structure can be changed by reasonable layups design, and the energy absorption can further be improved.

Preparation of Chitosan Hydrogel with Malonic Acid Crosslinker as Soil Conditioner for Soybean Plant (Glycine max L. merril)

AbstractThis research is on the manufacture of chitosan hydrogel crosslinked with malonic acid to be used as a soil conditioner for soybean plant (glycine max L. merrill). The aim of the study is to determine the effect of chitosan composition on malonic acid and the characteristics of hydrogel, and the effect of hydrogel as soil conditioner—its physical and chemical properties and role in soybean plant growth. Hydrogel of chitosan crosslinked malonic acid is carried out through a crosslinking chemical method. The increase in chitosan and malonic acid concentration can increase the swelling degree of hydrogel by 285.32%. Characterization is done using Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM). FTIR analysis shows changes in the specific absorption between chitosan and chitosan crosslinked malonic acid that occurs in the area of wave number 1080 cm−1 (C─O). SEM analysis shows that the increase in chitosan composition and malonic acid concentration causes the surface structure to be rough, hollow, and irregular. The use of hydrogel on soil conditions of soybean plants at 75th day measurements which give the most significant positive response is chitosan: malonic acid (2.5 g: 2.5%). Moisture value, soil temperature, C‐organic content, absorbed potassium level, and cation exchange capacity (CEC) content are 50%, 27–30 °C, 2%, 20.54 ppm, and 17.74 meq/100 g, respectively. In addition, the effect of hydrogel use on soybean plants result in the plant reaching a maximum height of 93 cm on the 75th day. The chitosan–malonic acid hydrogel has potential as soil conditioner.

Deposition of brown carbon onto snow: changes in snow optical and radiative properties

Abstract. Light-absorbing organic carbon aerosol – colloquially known as brown carbon (BrC) – is emitted from combustion processes and has a brownish or yellowish visual appearance, caused by enhanced light absorption at shorter visible and ultraviolet wavelengths (0.3 µm≲λ≲0.5 µm). Recently, optical properties of atmospheric BrC aerosols have become the topic of intense research, but little is known about how BrC deposition onto snow surfaces affects the spectral snow albedo, which can alter the resulting radiative forcing and in-snow photochemistry. Wildland fires in close proximity to the cryosphere, such as peatland fires that emit large quantities of BrC, are becoming more common at high latitudes, potentially affecting nearby snow and ice surfaces. In this study, we describe the artificial deposition of BrC aerosol with known optical, chemical, and physical properties onto the snow surface, and we monitor its spectral radiative impact and compare it directly to modeled values. First, using small-scale combustion of Alaskan peat, BrC aerosols were artificially deposited onto the snow surface. UV–Vis absorbance and total organic carbon (TOC) concentration of snow samples were measured for samples with and without artificial BrC deposition. These measurements were used to first derive a BrC (mass) specific absorption (m2 g−1) across the UV–Vis spectral range. We then estimate the imaginary part of the refractive index of deposited BrC aerosol using a volume mixing rule. Single-particle optical properties were calculated using Mie theory, and these values were used to show that the measured spectral snow albedo of snow with deposited BrC was in general agreement with modeled spectral snow albedo using calculated BrC optical properties. The instantaneous radiative forcing per unit mass of total organic carbon deposited to the ambient snowpack was found to be 1.23 (+0.14/-0.11) W m−2 per part per million (ppm). We estimate the same deposition onto a pure snowpack without light-absorbing impurities would have resulted in an instantaneous radiative forcing per unit mass of 2.68 (+0.27/-0.22) W m−2 per ppm of BrC deposited.

The reinforcement optimization of thin-walled square tubes for bending crashworthiness

Thin-walled structures have an inherent shortcoming that their cross sections are likely to flatten when subjected to transverse loading. In the paper, four simple novel reinforcement configurations into the thin-walled square tubes are put forward, and their bending resistance under three-point bending is investigated using the ABAQUS/Explicit code. The numerical results indicate that the reinforcements considerably enhance the structural bending resistance by effectively restricting the flattening of the upper compressive region of the cross sections. The variational characteristic of the maximum loads and the mean loads with the variables for the four reinforcing configurations is analyzed. The two key indicators SEA (specific energy absorption) and CLE (crash load efficiency) are introduced to further evaluate their energy absorbing and safeguard performance. It is found that one of the suggested reinforcement configurations significantly improve the values of SEA and CLE by 93.5%, 68.1% respectively, compared with the conventional empty tube.

Effect of initiator geometry on energy absorption of CFRP tubes under dynamic crushing

This study investigates the effect of initiator geometry, i.e. an inward-triggering cap (ITC), an outward-triggering plug (OTP) and a flat-surface plate (FSP), on the failure mechanisms and energy absorption of two carbon fibre reinforced polymer (CFRP) tubes, [03/45/−45/90/−45/45/03] (type U) and [03/902/03/(0/90)] (type W), under dynamic and quasi-static crushing in the axial direction. Under both dynamic and quasi-static crushing, the ITC induced massive transversely fractured fronds with enormous fragments, leading to high specific energy absorption, whereas the OTP produced the lowest specific energy absorption. The specific energy absorption of CFRP tubes under dynamic crushing were 32–40% and 12–69% lower than those under quasi-static crushing for the U-type tube and W-type tube, respectively. With the FSP, as compared to the U-type tube, the W-type tube had a higher specific energy absorption, though the wall thickness of the W-type tube was about 0.15 mm less than that of the U-type tube. Comparative analysis of the specific energy absorption indicated that the CFRP tubes were advantageous with the FSP when subjected to dynamic crushing, but they performed better with the ITC under quasi-static crushing.

Crashworthiness of polystyrene foam and cardboard panels reinforced with carbon fiber reinforced polymer and glass fiber reinforced polymer composite rods

This article presents an experimental study on the quasi-static crushing performance of carbon fiber reinforced polymer (CFRP) rods consisting of unidirectional carbon fibers wrapped by braided glass fibers. Rods with and without a taper are tested and then inserted in extruded and expanded polystyrene foam and cardboard panels. Hybrid columnar aluminum tube–CFRP rod structures are also tested in all panel materials. These results are compared to those based on glass fiber reinforced polymer (GFRP) rods, GFRP rods in polystyrene foams, and to GFRP rods in cardboard from a previous study. Tapered CFRP rods exhibit progressive crushing behavior with specific energy absorption superior to GFRP rods, with values of 82 kJ/kg and 65 kJ/kg, respectively. Moreover, the highest specific energy absorption (111 kJ/kg) is obtained in hybrid columnar aluminum tube–CFRP tapered rods, exceeding values of aluminum tubes (89 kJ/kg) and equivalent structures containing GFRP rods (102 kJ/kg). Within panels, cardboard produces the largest increase in mean load of CFRP and GFRP rods due to most constraining fiber splaying during crushing, followed by extruded foam, and lastly expanded foam. However, crushing displacement is most restricted in cardboard due to earlier final compaction. The smallest variations in crushing load occur in extruded polystyrene due to greater homogeneity throughout the foam structure.

Step-wise immobilization of multi-enzymes by zirconium-based coordination polymer in situ self-assembly and specific absorption

The simple and quick method for co-immobilization of multiple enzymes with clear spatial distribution has presented great challenges for decades. Herein, Zr4+ and 2-methylimidazole (2MIm) coordination polymers (CPs) were used to synthetize co-immobilized nanoreactor by a simple two-step procedure in aqueous environment. The CPs was first self-assembled in situ encapsulating glucose-6-phosphate dehydrogenase (G6PD) and then utilized coordination unsaturated metal sites on the surface of CPs to selectively adsorb hexahistidine-tagged α, β-unsaturated ketoreductase (his-tagged KRED). The obtained multi-enzymes system (G6PD@Zr-2MIm/KRED) was employed as an enzymatic reactor involving coenzymes regeneration. G6PD@Zr-2MIm/KRED still exhibited good repeatability and storage stability. The bi-enzymatic reactor could achieve more than 95% chalcone conversion ratio after 15 min and good tolerance at high temperature and different pH, retained about 70% and 80% of its initial activity after storage for 4 days and after 4 cycles, respectively. This step-wise enzyme immobilization method is easy to operate and can be used to prepare multi-enzyme systems with clear spatial distribution of the biocatalysts and allowing the coenzymes regeneration.

Effect of the Fine Recycled Aggregates on the Dynamic Compressive Behavior of Recycled Mortar

This study aims to investigate the dynamic behavior of recycled mortar under impact loading using a split Hopkinson pressure bar (SHPB). Several mortar mixtures were produced by adding various fine recycled aggregates (FRA) to the mixture in replacement percentages of 0%, 25%, 50%, 75%, and 100% of the natural fine aggregate (NFA). The effects of strain rate on compressive strength and specific energy absorption were obtained. Results show that the dynamic compressive strength and specific energy absorption of recycled mortar are highly strain rate dependent; specifically, they increase nearly linearly with the increase in peak strain rate. However, the compressive strength and specific energy absorption of recycled mortar are generally lower than those of NFA mortar (reference samples) under similar high strain rates. The findings of this research can help researchers and construction practitioners to ascertain the appropriate mix design procedure to optimize the impact strength properties of recycled mortar for protective structural application.

Characteristics of deformation pattern and energy absorption in honeycomb filler crash box due to frontal load and oblique load test

A crash box design is developed to enhance the crash box’s abilities to absorb crash energy. Previous research has developed the crash box by adding filler material. Adding the filling material to the crash box will increase energy absorption. Aluminum honeycomb has a combination of lightweight mass and an ability to absorb crash energy. The addition of filler material to the crash box will also reduce the possibility of global bending in the crash box. The method of study is a computer simulation using ANSYS Academic software ver 18.1. This research used circular, square and hexagonal cross-section variations, which reached the same cross-sectional area design. Geometry model for the crash box and honeycomb filler is defined as crash box thickness (tc) 1.6 mm, honeycomb filler thickness (t) 0.5 mm for single layer and 1 mm for double layer and crash box length (l) 120 mm. The materials used were AA6063-T6 for crash boxes and AA3003 for honeycomb fillers. The test model consisted of two types, namely frontal load and oblique load test. The impactor velocity (v) is set to 15 m/s. The impactor and the fixed support are modeled as a rigid body, while the crash box is assumed as an elastic body. Observations were done by using the characteristics of deformation pattern and the absorption amount of produced energy due to the given loading model. Based on the deformation pattern results, it can be found that in the crash box model with square and hexagon honeycomb filler, the occurred deformation pattern was concertina, while the crash box with circular honeycomb filler was the mixed mode in the frontal load test. Regarding the oblique loads, the crash box remains to collapse the global bending on all models. Simulation results with the frontal load test model found that the crash box with circle-shaped honeycomb has the highest energy absorption while the crash box with hexagonal honeycomb filler has the highest Specific Energy Absorption (SEA). In the oblique load test, it was found that the crash box with hexagonal honeycomb filler has the highest energy absorption and SEA. By comparing the hexagonal crash box model with and without honeycomb filler, it is noted that the hexagonal crash box with honeycomb filler has higher Crash Force Efficiency

Oblique crushing of truncated conical sandwich shell with corrugated core

All-metallic truncated conical sandwich shells with corrugated cores (TCSS) were investigated for crashworthiness under quasi-static oblique compression using a combined experimental and numerical approach. Subsequently, multi-objective optimization design of the TCSS was also performed by adopting the algorithm of NSGA-II to achieve maximum specific energy absorption (SEA) and minimum peak force (). Compared with a monolithic shell, the TCSS exhibits much higher SEA and lower under oblique loading, especially with its semi-apical angle set around 10° to 15°. The results provide valuable guidance for the application of truncated conical sandwich tubes in protective engineering, such as vehicle crashworthiness.

Performance of Asphalt Mixture using Waste Materials

A large number of solid wastes are being produced each day. This wastes, especially plastic and rubber effects the environment. So, nowadays these kinds of wastes are used in flexible pavements. In this project, the performance of the asphalt mixture using waste plastic and crumb rubber was determined. The aggregate were partially replaced by waste plastic (0.5%,1%,1.5%,2%,2.5%) and crumb rubber (0.5%,1%,1.5%,2%,2.5%). Also, 10% of fly ash is used in addition to filler material. Various tests like specific gravity, Water absorption, Impact test and Crushing strength for aggregate and softening point, Penetration test, Viscosity test, Specific gravity test and Binder content test for bitumen were conducted in obtained asphalt mixture. A Marshal stability test is also conducted to find the performance of the asphalt mixture. All the test results are compared with the results of the conventional mixture. The result obtained shows the plastic waste incorporated asphalt mixture does not affect the performance of the pavement also reduces the rutting and fatigue of the flexible pavement.

Crashworthiness of Thermoplastic Woven Glass Fabric Reinforced Composite Tubes Manufactured by Pultrusion

In this paper, crashworthiness of thermoplastic woven fabric reinforced composite tubes were investigated. Thermoplastic composite tubes with various length (40 mm and 80 mm) and fiber yarn orientation with respective to lengthwise (0 °/90 °, 15 °/75 °, 30 °/60 ° and 45 °/45 °) were manufactured by pultrusion and welding from home-made woven glass fabric/PP prepreg sheets. Quasi-static axial compressive tests of the composite tubes were performed under various temperatures (298 K, 358 K, 398 K and 453 K). Three crushing modes were observed: progressive folding, splaying and weld seam cracking. The influence of fiber orientation, tube length-diameter ratio and testing temperature on the peak load, mean load, specific energy absorption and crush efficiency were investigated. The results show that the peak load is controlled by fiber orientation and testing temperature. The mean force, specific energy absorption and crush efficiency are related to the three mentioned factors. Both fiber orientation and testing temperature have obviously influence on crushing modes of thermoplastic composite tubes. Length-to-diameter ratio also plays a role in crushing modes when the testing temperature is higher than the melting point of the resin.

Numerical Study on Axial Crushing of Auxetic Foam-Filled Square Tube

Filling the thin-walled tubes with a foam core is a typical method to enhance the energy absorption performance and stabilize their crushing responses under impact loading. Recently, auxetic foam material with negative Poisson’s ratio has gained remarkable popularity as an effective candidate to enhance the energy absorption capability of structures. In this paper, polyurethane auxetic foam is suggested as a foam core with the negative Poisson’s ratio of-0.31. Numerical simulation was performed to quantify the crush characteristics of auxetic foam-filled square aluminum tubes for variations in initial width of tube under quasi-static axial loading using the nonlinear finite element (FE) code LS-Dyna. Based on the numerical results, the influence of tube width was quantified in terms of energy absorption (EA), specific energy absorption (SEA), initial peak force (Pmax) and crush force efficiency (CFE). It is found that the progressive collapse and deformation modes of auxetic foam-filled tube (AFFT) is pronouncedly affected by varying the tube width. Furthermore, the SEA of AFFT is remarkably sensitive to the tube width variations, yet show low sensitivity to the EA of AFFT. The present study provides new design information on the crush response and energy absorption performance of auxetic foam-filled square tube with varying tube width.

Energy Absorption Analysis and Optimization Design of Local Surface Nanocrystallization Rectangular Tubes

A novel rectangular tube with circumferential anti-symmetric local self-surface nanocrystallization (CALSSN) layouts is designed for energy absorption. The effects of stripe numbers on the energy absorption performance is investigated. Results reveal that the 8-stripe CALSSN model exhibits the best buckling modes, which is more regular and stable than the untreated ones. It is also found that the stripe numbers highly depend on the structural sizes, unsuitable stripes number may reduce the buckling stability and periodicity. Besides, five CALSSN models with stripe numbers from 6 to 10 are selected to find the optimized size which has the highest specific energy absorption (SEA). A new 7-stripe CALSSN model which has optimal buckling modes and energy absorption performance is achieved.

Compressive testing of reinforced Nomex honeycomb at elevated temperatures

The effect of varying temperature on the compressive properties of a Nomex honeycomb core reinforced with small diameter composite tubes and rods has been investigated experimentally. Compression tests have been undertaken on a commercially-available Nomex core reinforced with tubes or rods at temperatures between 20 and 140 °C. Tests were also undertaken on unreinforced Nomex cores in order to assess the benefits associated with localized reinforcement of the core. Compression tests on the unreinforced cores have shown that the strength decreased steadily with increasing temperature, passing from 4.8 MPa at room temperature to 3.8 MPa at 140 °C. Similarly, the specific energy absorption (SEA) of the plain core samples decreased slightly from 22.3 to 18.9 kJ/kg over this range of temperatures. Reinforcing the cores with either rods or tubes had a positive effect on the compressive properties of the cores over the range of temperatures considered. For example, the room temperature compression strengths of the rod reinforced cores were 70% higher those of the plain core. Similarly, at 140°C, the rod-reinforced systems were 20% stronger than the plain core. Finally, the energy-absorbing capacity of the tube reinforced cores was higher than that of the rod-reinforced cores.

Specific absorption in Y3Al5O12:Eu ceramics and the role of stable Eu2+ in energy transfer processes

Several sets of Eu-doped Y3Al5O12 (YAG) ceramic samples were synthesized by the vacuum sintering technique. Absorption bands at 250, 370 and 550 nm in samples were attributed to the charge transfer transition in the EuY2+ + F+ pair center.

The Structure of the Sedimentary Cover in Freshwater Lakes of the Kindo Peninsula near the White Sea Biological Station of Moscow State University according to Data of Ground Penetration Radar and Boring

The geological structures of two freshwater lakes (the Verkhnee and Vodoprovodnoe lakes) located near the White Sea Biological Station of Moscow State University (in the Kandalaksha Bay in the White Sea) are analyzed for the first time on the basis of ground penetration radar (GPR) data. The morphology of the top of the Archean basement, the structure of the Quaternary sedimentary cover, and the topography of the bottom were studied. Shallow marine sediments that overlie the Archean rocks and a complex of lacustrine-marsh sediments were identified, using the drilling data on the Quaternary deposits. We constructed structural schemes of the main reflecting horizons and schemes with isopachs for the main complexes. The specific electrical resistivity and absorption coefficient were calculated by GPR data, and the possibilities of the use of these parameters for the delineation of GPR facies were considered.

Simplified Measurement on the Impact of Radiation by Mobiles

in fast growing world Mobile phone has become part of the human life. Specific Absorption is a measurement for the amount of Electromagnetic energy that has been absorbed by human tissue ,. Electromagnetic Radiation associated with Mobile Phones is always as an issue that has to be addressed for human safety, Particularly for children. More focus has been paid to induced SAR in the human head when exposed to EM Waves emitted from mobile Phone Antenna, but while using mobile phone the user gets exposed to a dangerous electromagnetic Radiations. ICNIRP Prescribed some guidelines for EM Exposure Level for Public. The Present paper is discuss the SAR Values of different Mobile Phones, Measured How much People are Aware of SAR Values are given as a survey. The study is compromised individuals that visited in the survey site .The awareness is assessed using structured questions and it was recorded to measure the awareness.

A numerical study on energy absorption capability of lateral corrugated composite tube under axial crushing

In this study, a comprehensive numerical investigation is carried out to evaluate the crashworthy behavior and the energy absorbing capacity of lateral corrugated composite tubes under axial loading. In this regard, a new lateral corrugated circle tube with a sinusoidal cross-section is proposed. To investigate the process of energy absorption, material model 54 in non-linear FE software LS-DYNA is applied for modelling axial crushing behavior. In order to validate the numerical simulations, the crushing results of hollow circular tube with uniform diameter are compared with available experimental data and a good agreement is observed. Afterward, crashworthiness analysis of lateral corrugated composite tubes is conducted by controlling the shape of the cross-section through the amplitude and the number of corrugations. The energy-absorbed performances such as specific energy absorption, initial peak crashing force, and mean crashing force of tubes are analyzed and discussed. Numerical analysis reveals that the lateral corrugated composite tubes have significantly obvious effects on the structural crashworthiness compared with ordinary circular tube under axial loading. Also, the results indicate that the geometrical shape of corrugation plays an important role in increasing the efficiency, controllability and failure patterns of corrugated tubes.