Specific Absorption Research Articles

A mesh morphing computational method for geometry optimization of assembled mechanical systems with flexible components

In this paper an interactive computational methodology was developed assuming that shape and size optimization of flexible components can significantly improve energy absorption or storage ability in assembled systems with flexible components (AS-FC). A radial basis functions mesh morphing formulation in non-linear numerical finite element analysis, including contact problems and flow interaction, was adopted as optimal design method to optimize shape and size design parameters in AS-FC. Flexible components were assembled in finite element environment according to functional ISO-ASME tolerances specification; non-linear structural analysis with flow interaction analysis was performed. The results of the study showed that the proposed method allows to optimize the shape and size of the flexible components in AS-FC maximizing the system's ability to absorb or store energy. The potentiality of the method and its forecasting capability were discussed for the case study of an automotive crash shock in which the specific energy absorption was increased by over 40%. The case studied refers to a simple flexible component geometry, but the method could be extended to systems with more complex geometries.

Crashworthiness Analysis and Multi-Objective Optimisation of Multi-Cell Windowed Structures under Dynamic Impact Loading

Applying a windowed design in a thin-walled structure is a method to further enhance the crashworthiness of the structure. In this study, two kinds of windowed designs were introduced into different regions of a multi-cell energy absorption structure to form a multi-cell windowed structure, and its crashworthiness under dynamic impact was studied. Dynamic impact testing and LS-DYNA finite element modelling were combined to calculate the crashworthiness response of the structure. The simulation results show that the use of the windowed multi-cell structure can improve the crashworthiness response of the multi-cell structure. The influence of the windowed design on the structural deformation mode was analysed in detail. In addition, the multi-objective optimization design of different windowed structures was carried out to obtain a comprehensive crashworthiness evaluation, and the results show that the windowed design at the front end of the structure yields good results regarding the initial peak force (PCF), while the windowed design in the middle of the structure can effectively improve the specific energy absorption (SEA) and energy absorption (EA).

Optimasi Jumlah Etil Selulosa dan Kecepatan Pengadukan dalam Preparasi Hollow Microspheres Kaptopril

Captopril is an Angiotensin-Converting Enzyme inhibitor (ACE Inhibitor) used for the treatment of hypertension. It has been reported that the duration of antihypertensive action after a single oral dose of captopril is only 6–8 h, specific absorption in the stomach, stable at acidic pH and degraded at high pH. These indicate a promising potential of the captopril hollow microspheres system as an alternative to the conventional dosage form. The preparation method used in this study is non-aqueous solvent evaporation. This study aims to determine the amount of ethyl cellulose (EC) and stirring speed to produce hollow microspheres having entrapment efficiency (EE), buoyancy and particle size maximum. Determination of the optimum hollow formula microspheres captopril uses a design factorial of two factors at two levels. The factors used in this study were the amount of EC and stirring speed, while the observed response was EE, buoyancy and particle size. The chosen optimum formula will be verified and characterized (yield, SEM, FT-IR). Formula AB was the optimum formula with EE 90.68%, buoyancy 81.52% and particle size 267.10µm. The verification obtained results in accordance with the prediction of the Design-Expert software. The characterization results obtained a yield value of 98.33%, with a spherical shape, uneven surface morphology, and hollow core. The results of FT-IR analysis showed that there was no interaction between the drug and polymer used in the formulation.

Analysis of Dynamic Damage Fractal and Energy Consumption Characteristics of Dolomite Marble

To investigate the damage fractal and energy dissipation of dolomite marble under blasting load, Dahongshan Copper Mine was selected as the test object and one-dimensional SHPB impact tests with different strain rates were carried out. The dynamic compressive strength, damage morphology, fractal fragmentation, and energy dissipation of the rock were analyzed. The results showed that the absorbed energy per unit volume and the crushing energy per unit mass of dolomite marble are closely related to the dynamic compressive strength. The fractal dimension D of dolomite marble increases with increasing strain rate, and the smaller the average block size of the rock, the degree of crushing deepens. In addition, as the incident energy increases, the crushing energy of the rock also increases, and the energy dissipation intensifies. Finally, after comparative analysis, the reasonable strain rate range is 68.14–77.61 s−1, and the reasonable specific energy absorption value range is 0.65–0.98 J/cm3. The fractal pattern of rock deformation and damage can be reasonably explained from the perspective of energy dissipation.

A new polyurethane-steel honeycomb composite pier anti-collision device: Concept and compressive behavior

A new type of pier anti-collision composite structure composed of honeycomb steel and polyurethane (PU) elastomer was proposed in this study. The impacts of the shape and filling materials of inner core cells on the failure mode, load–displacement cure, bearing capacity, structural stability, and energy absorption were studied by conducting uniaxial compression tests on device segments. Test results showed that the bearing capacity, structural stability, and energy absorption of honeycomb steel structure were significantly improved by PU elastomer filling. Besides, when compared with the square honeycomb structure and the regular hexagon honeycomb structure, the maximum values of average load, total energy absorption (TEA), and specific energy absorption (SEA), which were 69.6 kN, 1986.1 J, and 1300 J/kg, respectively, for the regular triangle honeycomb structure without PU filling, increased to 459.3%, 376.38%, and 212.5%, respectively, for the regular hexagonal core cell structure with PU filling, which was proved to be the most suitable core structure for pier anti-collision device.

Large Torsion Deformation: Centrosymmetric Reentrant Honeycomb

There exist some problems in the crash box and anti-collision beam sandwich structure, such as monotone deformation pattern and uneconomical energy absorption performance. In order to raise the deformation capacity and energy absorption performance of sandwich structure, centrosymmetric reentrant honeycomb (CRH) and hexagonal centrosymmetric reentrant honeycomb (HCRH) are proposed based on auxetic reentrant honeycomb (ARH) in this work. Based on HCRH, four kinds of transverse combination structures and two kinds of longitudinal combination structures are obtained. The results of specific energy absorption show that the energy absorption capacity of the angular contact homodromous combination structure (ACOC) is about 3 times that of the other three transverse combination structures. Compared with longitudinal heterodromous combination structure (LHEC), the energy absorption capacity of longitudinal homodromous combination structure (LHOC) is improved by 72.7%.

Experimental research on the compressive properties of a new type three-dimensional angle-interlock woven composite

The new three-dimensional angle-interlock woven UHMWPEF/epoxy composite was prepared by the VARIM method, and its mechanical properties were studied. Specifically, quasi-static and dynamic compression tests were carried out by universal testing machine and split Hopkinson pressure bar (SHPB) apparatus. Stress-strain curves under the quasi-static and high strain rates (800, 1000, 1400, and 1600 s−1) reveal the destructive characteristics of the composite material. The results indicate that the UHWMPEF/epoxy composite is a strain rate sensitive material and shows different levels of sensitivity at various strain rates. In the quasi-static compression test, when the strain rate was increased from 4.2 × 10−4 to 1.4 × 10−3 s−1, the failure load and ultimate strength increased by about 19.1% and 20.1%, respectively, and the failure strain and specific energy absorption decreased by about 1.53% and 6.1%, respectively. In the dynamic compression test, when the strain rate increased from 800 to 1600 s−1, the failure load and ultimate strength increased by about 16% and 15.9%, respectively, and the failure strain and specific energy absorption decreased by about 64.7% and 60.3%, respectively. The failure fracture surface of the specimen under quasi-static compression was at an angle of 40°–45° with the load direction. The matrix fragmentation at the fracture was obvious, and the warp fiber bundle was broken and peeled off from the matrix. The damage of specimen under dynamic compression develops quickly and the deformation process is short, which shows a relatively symmetrical shear fracture failure morphology.

Contribution of Surface Treatment on Physical and Mechanical Properties of Recycled Concrete Aggregates

The demand for virgin aggregates for concrete production worldwide has been increasing. At the same time, there is an increase in the production of rubbles from construction‐related activities. The residues are produced either due to leftovers or from the demolished structures. However, worldwide, the utilization of recycled concrete aggregate (RCA) material for structural concrete has been limited, often considered inferior due to distorted surfaces. The problems with RCA arise because it is a composite aggregate made of natural aggregate and cement, and adhered surface mortar is the discontinuities on the surface that arise from the production technique or the strength of the original concrete. The development of hydrated calcium silicate binder in the concrete matrix has been the critical desire of researchers to make better concrete material. This research focuses on the treatment of RCA from locally available rice husk ash with minimum pozzolanic cement. The objective was achieved by conducting tests on the properties of aggregates that include specific gravity and water absorption, aggregate crushing value (ACV), and aggregate impact value (AIV). The effectiveness of the treatment technique is assessed by the analysis of SEM imagery and XRD analysis of the microstructure cement paste around the RCA. At 20% pozzolan concentration, RCA treatment yields comparable specific gravities, water absorption, ACV, and AIV. Furthermore, the replacement of 5% rice husk ash (in 20% concentration) provided the optimal proportion of treatment for RCA, resulting in a reduction of ACV by 31.4%, AIV by 30.0%, and water absorption by 12.7% compared to the untreated RCA. XRD showed that calcite (CaCO₃), quartz, and portlandite phases were the majority in the untreated RCA. The study indicates that pozzolanic cement with 15% can be used with 5% RHA to produce RCA with characteristics almost similar to virgin aggregates. This research presents a consistent methodology to achieve modified RCA for application in construction.

Dynamic Crushing Behaviors of Multi-Layered Gradient Honeycombs with Different Poisson’s Ratios: A Finite Element Simulation

In this work, a new multi-layered gradient honeycomb (MGH) design was proposed by filling structure layer with different Poisson’s ratio configurations (e.g., positive, zero and negative Poisson’s ratio) from the perspective of coupling the deformation characteristics with each other to improve in-plane dynamic properties and control energy absorption capacities. The dynamic behaviors and energy-absorbing characteristics of the MGHs under in-plane impact loadings were investigated by using explicit dynamic finite element (FE) simulation. This paper mainly focused on the effects of multi-layered gradient arrangements and impact velocities on the dynamic Poisson’s ratios, dynamic plateau stresses, crushing load uniformities and specific energy absorption of the MGHs. A semi-empirical formula for the plateau stresses of the MGHs was presented. It was shown that through the proper choice of multi-layered arrangements, the MGHs can effectively improve the dynamic crushing behaviors and control energy absorption capacities. In addition, the dynamic shock enhancement of the MGHs was also investigated by introducing the uniformity index.

Eco-efficient steel slag concretes: an alternative to achieve circular economy

Abstract Annually billions of tonnes of aggregates are extracted to apply in civil construction generating environmental impacts and energy consumption. So, based on circular economy principles applying residues as aggregates is a good solution to reduce the mining activity and to generate a more efficient destination for the residues. Thus, this research aims to evaluate the technical, economic, and environmental performance of concretes produced entirely with steel slag aggregates. The concretes were characterized through physical properties, as specific gravity, water absorption, compressive and tensile strength. Durability tests (expansibility) were also conducted. The authors analyzed the cost assessment and environmental impact of steel slag concrete production as well. The incorporation of steel slag increases the compressive and tensile strength of concrete, analyzed in different ages. Additionally, the steel slag does not present expansibility when confined in the concrete matrix. The entire replacement of natural aggregates for steel slag allowed to reduce in 31% the cement consumption, a decrease of 140 kg/m3, for the same strength class. The environmental analysis showed that the incorporation of steel slag aggregates reduced the cement intensity of concrete and its impact. Regarding the cost assessment, the mixtures with steel slag presented a lower cost compared to the conventional one. These results indicate that steel slag aggregates could be used in a cleaner production of concrete, replacing natural aggregates with no injury. This research provides the feasibility of using steel slag aggregates in a cleaner and cheaper concrete production and contribute to the promotion of sustainable solutions for the construction sector through the circular economy principles.

Lasers in periodontal therapy

The unique nature of laser light and its specific absorption, led to an expansion of its use in medicine. Several medical specialties use lasers in their daily practice, and it has become the standard of care for surgical therapy. The recent rapid development of lasers, with different wavelengths and onboard parameters may continue to have major impact on the scope and practice of dentistry. The use of lasers in dentistry has increased over the past few years. Currently, lasers are generally accepted in periodontal therapy and widely used as a tool for soft tissue management. Application comfort, the silence, anesthesia reduction and other such advantages make lasers attractive for society and professionals. More long term systematic studies are necessary to evaluate the clinical and biological effects of each type of laser, the time and application mode, unique/multiple doses and application frequency.

A Dynamic Model and Parameter Identification of High Viscosity Magnetorheological Fluid-Based Energy Absorber with Radial Flow Mode.

The excellent suspension stability of the high-viscosity linear polysiloxane magnetorheological fluid (HVLP MRF) makes it a great controlled medium for magnetorheological energy absorbers (MREAs). In our previous work, the Herschel–Bulkley flow model (HB model) was used to describe the shear-thinning rheological behavior and establish the dynamic model of an HVLP MRF-based MREA with radial flow mode. However, as the established model was implicit, the MREA response time increased and the buffer effect was degraded. To improve the time response characteristics, an explicit dynamic model based on the HB model incorporating minor losses (called the E-HBM model) is proposed in this study. The model parameters were identified based on the HBM model. To verify the E-HBM model, five evaluation parameters for the energy absorption performance of the MREA, that is, peak force, mean force, crush force efficiency, specific energy absorption, and stroke efficiency, were introduced to compare the theoretical results with the experimental results obtained using a high-speed drop tower facility with a mass of 600 kg. Then, the relative error of the crush force efficiency, specific energy absorption, and stroke efficiency was quantitatively and comprehensively analyzed considering the E-HBM model and experimental results. The results indicate that the proposed E-HBM model agrees with the impact behavior of the radial flow mode MREA.

Zirconium (IV)-3-hydroxy-2-tolyl-4H-chromen-4-one complex-the analytical and DFT studies.

Trace determination of Zr(IV) was carried out by its complexation with a newly synthesized chromone derivative, 3-hydroxy-2-tolyl-4H-chromen-4-one (HToC) for the formation of a 1:4 (M:L) yellow-colored complex from the bicarbonate medium maintained at pH 7.90-8.13. The complex was extractable into the non-aqueous organic solvents showing maximum and stable color intensity in dichloromethane in the wavelength range 414-430nm. The complex obeyed Beer's law showing linearity of calibration curve in the range 0.0-1.1µg Zr(IV) ml-1 with an optimum range of determination as 0.44-1.0ppm Zr(IV) detected from the Ringbom plot. Molar absorptivity, specific absorptivity, and Sandell's sensitivity of thus prepared complex were ascertained, respectively as 4.1971 × 104lmol-1cm-1, 0.4601mlg-1cm-1, and 0.0022µg Zr(IV) cm-2 at 420nm. The linear regression equation being [Formula: see text] (Y = absorbance, X = µg Zr(IV) ml-1) with the correlation coefficient of 0.9977 and detection limit of the procedure as 0.0729µgml-1. Theoretical calculations were used to determine and compare structural and bonding properties of the Zr(IV)-HToC complex along with justification of the donor sites provided by ligand for complexation with respect to the metal. The consequences obtained were highly cogent with standard deviation of ± 0.0021 absorbance unit. The procedure was applied to various synthetic (some analogous to cooperate and nickel zirconium) and technical (reverberatory flue dust and water) samples with satisfactory results.

Effect of the incorporation of sugarcane bagasse fibers in asphalt mixture dosed by the Superpave method

Sugar industry waste bagasse contains many natural fiber materials, and the application of natural fibers in asphalt mixes such as SMA (Stone Matrix Asphalt) has become an attractive alternative for the construction of flexible pavements. This study aims to evaluate the mechanical performance of an asphalt mixture modified by incorporating 0.3% sugarcane bagasse fiber and with a size of 20 mm. The asphalt binder was submitted to penetration, softening point, and rotational viscosity tests to carry out this research, and the aggregates were characterized by specific mass, particle size, and absorption tests. Furthermore, the Superpave dosage was performed to produce the specimens to be evaluated in the splitting tensile strength test, resilient modulus, Marshall stability, and draindown sensitivity. As a result, the modified asphalt mixture presented a better performance in all evaluated strength tests and the leakage content within the standard specifications. Therefore, according to this, re-search, sugarcane bagasse fibers proved to be a viable alternative for SMA-type mixtures. Thus, the application of this material in asphalt paving and improving some essential characteristics can significantly reduce the environmental impacts generated by the inadequate disposal of these residues by sugar mills.

Metabolomic investigation of differences in components and taste between hon-mirin and mirin-like-seasoning

Hon-mirin (HM) is a traditional Japanese brewed seasoning used to confer sweetness and koku. Mirin-like-seasoning (MLS) is a less-expensive alternative to HM because it is not subjected to liquor tax in Japan. In this study, components and taste qualities of HM and MLS were compared by gas chromatography/mass spectrometry (GC/MS)-based metabolomics and a sensory evaluation. GC/MS analyses of foods with high sugar content are limited by contamination of the ion source and difficulty in detecting other compounds. To resolve this issue, solid-phase analytical derivatization (SPAD), in which the extraction and derivatization of analytes can be conducted in a single step, was applied as a novel sample preparation method in this study. The effect of sugar was removed by the specific absorption, derivatization, and elution of ionic compounds, such as amino acids and organic acids, with ion-exchange solid-phases. The SPAD method application enabled the detection of 15 amino acids and 14 organic acids using ion-exchange solid-phases by performing GC/MS analysis twice. These ionic compounds were not detected in mirin using conventional sample preparation. HM samples had a higher amino acid content and a lower sugar content than those of MLS samples. Furthermore, differences in sweetness and koku between HM and MLS were observed in a sensory evaluation. This is the first GC/MS-based metabolomics analysis of mirin using the SPAD method; our results provide insight into the differences between HM and MLS.

Design and optimisation of vehicle frontal bumper beam with alternative carbon fibre-reinforced plastics in corrugated sandwich structure

Bumper beam is the key structure to protect the vehicle from impact collision. The aim of this paper is to propose a novel bumper beam consisting of continuous carbon fibre-reinforced plastic (CFRP) bumper beam, which is assembled by carbon fibre-reinforced epoxy (EP/CF) skin panels and carbon fibre-reinforced polycarbonate (PC/CF) corrugated sandwich cores. First, the proposed bumper structure is compression molded and then the crashworthiness performance is evaluated via impact experimental test and numerical analysis. It is demonstrated that the numerical results are in good agreement with the experimental data. Then, the effect of the thickness of panel and core on the intrusion, impact force and specific absorption on the impact performance is investigated by using the sensitivity analysis. Based on this, the Kriging proxy model is adopted for design of experiment (DOE), and a multi-objective optimisation with NSGA-II genetic algorithm is used to optimise the thickness (layers) of the skin panels and sandwich core. Results show that the impact performance meet the requirement of crashworthiness with a mass reduce of 35.57%. Accordingly, the proposed bumper beam exhibit superior impact performance, reduced weight to the traditional integrated counterpart. Furthermore, the structure-material-performance integration is an effective method to design CFRP as structural parts.

Compressive Behavior of Al-TiB2 Composite Foams Fabricated under Increased Pressure.

The application of increased pressure was used as a strategy to investigate the effect of different cell structures on the mechanical properties of Al-TiB2 composite foams. In situ Al-xTiB2 (x = 5, 10 wt.%) composites were foamed under three different pressures (0.1 MPa, 0.24 MPa, 0.4 MPa) through the liquid melt route. The macro-structure of the composite foams was analyzed in terms of cell size distribution measured by X-ray microcomputed tomography (micro-CT). It was found that the mean cell size decreases, and the cell size distribution range narrows with increasing pressure. Uniaxial compression tests revealed that the stress fluctuation (Rsd) of 10TiB2 foams is larger than that of 5TiB2 foams under the same pressure. Moreover, cell size refinement causes the simultaneous deformation of multi-layer cells, which leads to an enhancement in the energy absorption efficiency and specific energy absorption. The comparison of experimental data with theoretical predictions (G&A model) is discussed.

Water Absorption Kinetics in Composites Degraded by the Radiation Technique.

Rubber-based wastes represent challenges facing the global community. Human health protection and preservation of environmental quality are strong reasons to find more efficient methods to induce degradation of latex/rubber products in order to replace devulcanization, incineration, or simply storage, and electron beam irradiation is a promising method that can be can be taken into account. Polymeric composites based on natural rubber and plasticized starch in amounts of 10 to 50 phr, obtained by benzoyl peroxide cross-linking, were subjected to 5.5 MeV electron beam irradiation in order to induce degradation, in the dose range of 150 to 450 kGy. A qualitative study was conducted on the kinetics of water absorption in these composites in order to appreciate their degradation degree. The percentages of equilibrium sorption and mass loss after equilibrium sorption were found to be dependent on irradiation dose and amount of plasticized starch. The mechanism of water transport in composites was studied not only through the specific absorption and diffusion parameters but also by the evaluation of the diffusion, intrinsic diffusion, permeation, and absorption coefficients.

Manufacture of Spongy Gravel from Obsidian to Produce Lightweight and Thermal-Insulating Concrete

The present study aims to convert obsidian rocks into spongy gravel for the use in the production of lightweight and heat insulating concrete. The rocks were burned at 960°C to achieve maximum swelling of the samples, then broken into gravel and sand sizes. For comparison purposes, two other types of aggregates were used, namely pumice and basalt. The main physical tests, such as specific gravity, bulk density, porosity, and water absorption were performed. For testing the resistance of samples to alkalinity, KOH and Na OH solutions were used. The results showed that the obsidian sample gave the best specifications, where its specific gravity was 0.33, while the values were 1.1 for pumice and 2.7 for basalt, with the same results being applied to the other physical tests. After forming the concrete cubes of the three types of aggregates with three mixing proportions (1, 1.5, and 3 of cement, sand, gravel, respectively), the most important physical, mechanical, and chemical tests were performed along with their specific ages. The results were distinct, specifically the specific gravity values of the aggregate concrete samples A and B (1.3 and 1.5, respectively, as compared to the basalt sample, which recorded a value of 2.5. As for the thermal conductivity, a distinct value was recorded for the obsidian sample (0.16 W/m.k) as compared to the pumice and basalt samples (2.1 and 1.32 W/m.k, respectively). Perhaps the reason behind this variation is the pores type of the aggregate produced for the obsidian sample, which were of the closed system. This prevents the seeping of water and cement materials into the body of gravel, keeping it at light weight and providing it with high thermal insulation. As for the alkalinity test, there was no evidence of a reaction with the alkali cement in the obsidian and pumice samples, except for a slight reaction that appeared in the basalt sample.

Ballistic Performance Evaluation of Kevlar-Glass Fibre Hybrid Composite Laminate against Medium Velocity Impact

In this paper, the post ballistic impact behaviour of kevlar-glass fibre hybrid composite laminates was investigated against 9×19 mm projectile. Eight different types of composite laminates with different ratios of kevlar woven fibre to glass fibre were fabricated using hand lay-up with epoxy matrix. Ballistic behaviour like ballistic Limit (V50), energy absorption, specific energy absorption and Back Face Signature (BFS) were studied after bullet impact. The results indicated that as the Percentage of glass fibre is increased there was a linear increment in the ballistic behaviour. Addition of 16% kevlar fabric, composite sample meets the performance requirement of NIJ0101.06 Level III-A. Since the maximum specific energy absorption was observed in Pure Kevlar samples and the adding of glass fibre increases the weight and Areal Density of the sample, further investigations need to be carried out to utilize the potential of glass fibre for ballistic applications.