Energy Absorption Ratio Research Articles

Energy absorption of reinforced concrete deep beams strengthened with CFRP sheet

The function of carbon fibre reinforced polymer (CFRP) reinforcement in increasing the ductility of reinforced concrete (RC) deep beam is important in such shear-sensitive RC member. This paper aims to investigate the effect of CFRP-strengthening on the energy absorption of RC deep beams. Six ordinary RC deep beams and six CFRP-strengthened RC deep beams with shear span to the effective depth ratio of 0.75, 1.00, 1.25, 1.50, 1.75, and 2.00 were tested till failure in this research. An empirical relationship was established to obtain the energy absorption of CFRP-strengthened RC deep beams. The shear span to the effective depth ratio and growth of energy absorption of CFRP-strengthened deep beam were the significant factors to establish this relationship.

Thermal-dynamical analysis of blister formation in chirped mirror irradiated by single femtosecond lasers.

The laser-induced damage behaviors of chirped mirrors (CMs) are studied by single 800 nm, 38 fs lasers. The CMs provide group delay dispersion of around -60 fs² and average reflectivity of about 99.4% with bandwidth range of 200-300 nm at a central wavelength of 800 nm. Interestingly, a circular blister feature appears in the CMs at a wide range of laser fluence. An optical microscope, atomic force microscope, scanning electron microscope, and surface profiler are applied to describe the blister characteristics. An adiabatic expansion model of ideal gas is adopted to illustrate the formation dynamics of blisters. The evolution of blisters can be explained by partial evaporation of the film and a subsequent gas expansion, driving the bulging of the film stack up to the stress limit, where the blister fractures. According to this model, the energy absorption ratio of blisters increases monotonously with increasing laser fluence before the occurrence of the focal spot confinement effect.

Experimental and Numerical Crashworthiness Investigation of the Empty and Foam‐Filled Conical Tube with Shallow Spherical Caps

ABSTRACTThis paper experimentally investigates the crash responses of the empty and polyurethane foam‐filled conical tubes with shallow spherical caps under quasi‐static axial loading. To find more details about the energy absorption mechanism, finite element methods is used to simulate the crush process. In terms of finding more efficient and lighter crash absorbers particularly, the energy absorption and specific energy absorption and load ratio have been considered. The influences of the tube geometrical and material parameters such as radius of spherical region, wall thickness, length, semi‐apical angle and foam density on the energy absorption mechanism have been investigated. This study provides practical information for the use of thin‐walled tubes with shallow spherical caps as energy absorbers in aerospace applications to design reentry of sounding rocket based on foam‐filled conical tube with shallow spherical caps.

Experimental Research on Energy Absorption Characteristic of PVB Laminated Windshield Subjected to Headform Low-speed Impact

Parametric dynamic experiments on various impact velocities(6.6-11.2 m/s), angles(60°-90°), directions are performed to obtain the energy characteristics of windshield under headform impact. Dynamic response of headform is systematically analyzed via the acceleration-time curve obtained by acceleration sensor. High-speed camera is employed to capture and analyze the crack propagation process. Macro damage morphology of windshield is discussed, and compared with it in real accident. With the definition of maximum contact force, maximum plastic hollow, head injury criteria, loss of headform kinetic energy and kinetic absorption ratio, the energy absorption characteristics of windshield under above mentioned parametric experiments are investigated. Experiment results may provide fundamental data and theoretical base for future research.

養殖生簀における動揺養成装置の開発と実用化に関する研究

In the case of rearing fish juveniles that have hiding behavior in the floating aquaculture preserves, the number of fish juveniles decreases due to the stress from movement of preserves caused by the ocean waves. We need the device that can reduce structural movement by absorbing the wave energy and we invented the wave energy absorption gadget operates on the principle that the natural frequency of the oscillating wave column is determined not by its volume but by its length. We conducted some field experiments in different wave conditions and acquired high wave energy absorption ratio besides better survival rate of fish juveniles in the rearing facilities.

Effects of stacking thickness on the damage behavior in CFRP composite cylinders subjected to out-of-plane loading

The purpose of this study is to evaluate effects of stacking thickness on the microscopic damage behavior in a filament wound carbon fiber reinforced plastics (FW-CFRPs) composite cylinder subjected to impact or quasi-static out-of-plane loading. From both tests, thicker CFRP improved the stiffness of the cylinder and decreased the resultant plastic deformation due to indentation. From the cross-sectional observation, it is clarified that fiber breakages were localized for the specimens with impact tests more than 10-layers and specimens with quasi-static tests more than 15-layers. In order to discuss the relation between the damage and the absorbed energy, damage depth ratio was defined as fiber damage depth per unit CFRP thickness. To normalize the effect of thickness, absorbed energy ratio was also defined as absorbed energy per unit CFRP thickness. Absorbed energy ratio as a function of absorbed energy ratio was expressed as one master curve regardless of loading conditions.

Automotive windshield — pedestrian head impact: Energy absorption capability of interlayer material

During accident, the interlayer of windshield plays an important role in the crash safety of automotive and protection of pedestrian or passenger. The understanding of its energy absorption capability is of fundamental importance. Conventional interlayer material of automotive windshield is made by Polyvinyl butyral (PVB). Recently, a new candidate of high-performance nanoporous energy absorption system (NEAS) has been suggested as a candidate for crashworthiness. For the model problem of pedestrian head impact with windshield, we compare the energy absorption capabilities of PVB and NEAS interlayers, in terms of the contact force, acceleration, velocity, head injury criteria, and energy absorption ratio, among which results obtained from PVB interlayers are validated by literature references. The impact speed is obtained from virtual test field in PC-CRASH, and the impact simulations are carried out using explicit finite element simulations. Both the accident speed and interlayer thickness are varied to explore their effects. The explicit relationships established among the energy absorption capabilities, impact speed, and interlayer material/thickness, are useful for safety evaluation as well as automotive design. It is shown that the NEAS interlayer may absorb more energy than PVB interlayer and it may be a competitive candidate for windshield interlayer.

Bending behaviors of metallic sandwich plates with a sheared dimple core under simply supported loading

In this study, the bending responses of metallic sandwich plates with a sheared dimple core were investigated through the 3-point bending tests and dynamic plane bending tests. It was experimentally shown from the uniaxial tensile tests that the yield and tensile strengths of the brazed face sheet were weaker than those of the welded face sheet. A mild steel sheared dimple core was fabricated by the sectional forming process and then bonded with DP590 face sheets by multi-point resistance welding. Analysis for large deformation of a sandwich plate subject to 3-point bending was carried out, where frictional work was considered and a face sheet was treated as a rigid-plastic material based on Hollomon’s flow rule. Load—deflection curves and the deformed shapes of the finite element method computations and the experiments were efficiently predicted by the proposed analysis. The effect of frictional work on the peak load and energy absorption increases as the bending angle increases. The dynamic bending responses of the sandwich plates, such as the effect of a deformed shape, failure mode, energy absorption and absorption ratio were compared with those of a high-strength steel sheet. It was demonstrated that a bendable sandwich plate was stronger construction than a high-strength steel sheet under the tested conditions, despite the weight reduction and weaker properties.

The influence of sex and maturation on landing biomechanics: implications for anterior cruciate ligament injury

During landing and cutting, females exhibit greater frontal plane moments at the knee (internal knee adductor moments or external knee abduction moments) and favor the use of the knee extensors over the hip extensors to attenuate impact forces when compared with males. However, it is not known when this biomechanical profile emerges. The purpose of this study was to compare landing biomechanics between sexes across maturation levels. One hundred and nineteen male and female soccer players (9-22 years) participated. Subjects were grouped based on maturational development. Lower extremity kinematics and kinetics were obtained during a drop-land task. Dependent variables included the average internal knee adductor moment and sagittal plane knee/hip moment and energy absorption ratios during the deceleration phase of landing. When averaged across maturation levels, females demonstrated greater internal knee adductor moments (0.06±0.03 vs 0.01±0.02 N m/kg m; P<0.005), knee/hip extensor moment ratios (2.0±0.1 vs 1.4±0.1 N m/kg m; P<0.001) and knee/hip energy absorption ratios (2.9±0.1 vs 1.96±0.1 N m/kg m; P<0.001) compared with males. Higher knee adductor moments combined with disproportionate use of knee extensors relative to hip extensors observed in females reflect a biomechanical pattern that increases anterior cruciate ligament loading. This biomechanical strategy already was established in pre-pubertal female athletes.

Dynamic process of ring systems as energy absorber subjected to lateral impact loading

This paper presents both experimental and numerical investigations on the dynamic behaviour of one-dimensional ring systems subjected to lateral impact loading. This work investigates the energy absorbing and stress-wave propagation characteristics of such ring systems for engineering design. The experiments on energy absorption were performed by making use of a modified split Hopkinson pressure bar test system together with a high-speed digital camera device. Three-dimensional numerical simulations were performed correspondingly to simulate the dynamic process. The numerical results are shown in a reasonable agreement with the experimental results. The features including energy absorption, wave elimination and stress-wave variations after collapse were investigated in detail. The energy absorption ratio is primarily affected by the thickness and the number of rings, while the impact velocity and the inner radius play a minor role. After the stress wave propagates through one-dimensional ring systems, the amplitude of the stress wave may be greatly eliminated. However, once the densification happens, it is observed that the amplitude of the transmitted stress wave may increase greatly, which should be noticed in safety considerations.

Monotonic shear tests of cold-formed steel wall frames with sheathing

This research is focused on the experimental study of the structural strength of cold-formed steel wall frames with sheathing under monotonic shear loading. Two aspect ratios, 1.0 and 2.0 were utilized in the design of wall specimens. Three different kinds of sheathing material, gypsum board, calcium silicate board, and oriented-strand board, with two different thicknesses (9 and 12mm) were adopted in the test specimens. The ultimate strength, stiffness, energy absorption, and ductility ratio were studied for each test specimen. In final, the ductility ratios of the cold-formed steel wall frames similar to the wall configuration conducted in this study are proposed.

Behaviour of Slurry Infiltrated Fibre Concrete (SIFCON) under triaxial compression

Slurry infiltrated fibre concrete (SIFCON) is one of the recently developed construction material that can be considered as a special type of high performance fibre reinforced concrete (HPFRC) with higher fibre content. In the current research, triaxial compressive behaviours of high strength concrete (HSC), HPFRC and SIFCON were investigated. Purposefully, laboratory tests employed on four types of 75 × 150 mm cylindrical specimens with different steel fibres volumes (0, 2, 5 and 10%). All tests were conducted under four different confining pressure levels (0, 5, 15 and 21.5 MPa) according to triaxial conditions. Consequently, stress-strain curves were obtained and governing failure patterns and failure criterions of HSC, HPFRC and SIFCON samples were discussed. According to the results increasing of fibre volumes increases peak stress, energy absorption, toughness and Poisson's ratio while increasing confining pressures increases peak stress, energy absorption and toughness. Also, this may cause concrete to behave as a plastic material.

Modeling and optimization of foam-filled thin-walled columns for crashworthiness designs

Thin-walled columns play an important role on passenger safety in vehicular collisions for their progressive deformation patterns and large energy absorptions. A thin-walled column with a large specific energy, i.e., the ratio of energy absorption to its mass, is often desirable to the automotive industry, because such designs could enhance safety and reduce manufacturing cost. Due to the complexity of crash mechanism, obtaining such designs has been a challenge to the trial-and-error approach using physical prototype testing. To this end, combining finite element simulations with optimization methodologies has become the viable means to meet the challenge. In this paper, single- and triple-cell hexagonal columns filled with aluminum foams were optimized for maximum specific energy with simultaneous consideration of section geometry, tube thickness, and foam density. The effects of crushing forces on column designs were analyzed by comparing optimum solutions with and without constraints on the mean crushing forces. The interaction effects between the tube and foam of composite columns and the relative advantages of single- and triple-cell structures were investigated and discussed.

面外負荷を受けるＦＷ‐ＣＦＲＰ複合パイプの損傷挙動に及ぼす積層厚さの影響

In order to investigate effects of lamination thickness on the damage progress due to out-of-plane loading in FW-CFRP composite pipes, impact and quasi-static indentation tests were conducted. Absorbed energy decreased with number of plies and saturated. Damages, such as indentations, splittings and fiber breakages, occurred around a loading point. Propagation of fiber breakages and splittings is larger in specimen after quasi-static indentation tests than those of impact. These damages were localized with number of plies. Residual deflections of aluminum liners were also suppressed with number of plies. Residual burst strength ratio increased more than 70% for the absorbed energy ratio of less than 10 J/m.

Mechanical properties of rock under coupled static-dynamic loads

Rock drilling machine, INSTRON testing system, and SHPB device are updated to investigate the characteristics of rocks at great depth, with high loads from overburden, tectonic stresses and dynamic impacts due to blasting and boring. It is verified that these testing systems can be used to study the mechanical properties of rock material under coupled static and dynamic loading condition and give useful guidance for the deep mining and underground cavern excavation. Various tests to determine the rock strength, fragmentation behavior, and energy absorption were conducted using the updated testing systems. It is shown that under coupled static-dynamic loads, if the axial prestress is lower than its elastic limit, the rock strength is higher than the individual static or dynamic strength. At the same axial prestress, rock strength under coupled loads rises with the increasing strain rates. Under coupled static and dynamic loads, rock is observed to fail with tensile mode. While shear failure may exist if axial prestress is high enough. In addition, it is shown that the percentage of small particles increases with the increasing axial prestress and impact load based on the analysis of the particle-size distribution of fragments. It is also suggested that the energy absorption ratio of a specimen varies with coupled loads, and the maximum energy absorption ratio for a rock can be obtained with an appropriate combination of static and dynamic loads.

Fast MRI coil analysis based on 3-D electromagnetic and RF circuit co-simulation

To accelerate the analysis of a multi-element MRI coil, a two-way link is used between radiofrequency (RF) circuit and 3-D electromagnetic (EM) simulation tools. In this configuration, only one 3-D EM simulation is required to investigate the coil performance over a range of different tunings, saving considerable computation time. For the purpose of 3-D EM simulation, the coil feed networks and trim capacitors are substituted by 50Ω ports. The entire coil was tuned in the RF circuit domain, and the near-field profiles of the electric and magnetic field components were then calculated, together with the specific energy absorption ratio (SAR) maps in the 3-D EM domain

Comparisons between Measured and Calculated Properties in the Microwave Heating of Na-A, K-A, and Na,Ca-A Zeolites

For three dehydrated zeolite A samples, heated behaviors in microwave (f = 2.45 GHz) irradiation were measured. In addition, the relative energy absorption ratios for microwaves among the three zeolites were theoretically calculated as a function of temperature, and properties obtained by the calculations and measurements were compared with each other. During the irradiation under every condition, the heated temperatures were in the order of Na12-A > K12-A > Na4Ca4-A. The magnitude of the energy absorption ratio was the same as the order of the heated temperature. It was found that the absorption ratio calculated by the present method can correctly reflect the heated behaviors of zeolites in microwave irradiation. The dielectric relaxation loss (relax II) that appeared in the higher frequency side had a decisively important influence on the absorption of microwaves. A zeolite with a lower activation energy of cation movement (or more mobile cations) was more easily heated by microwaves.

Mechanical properties of injection molded long fiber polypropylene composites, Part 2: Impact and fracture toughness

AbstractThis study describes the effect of fiber length and compatibilizer content on notched izod impact and fracture toughness properties. Long fiber polypropylene (LFPP) pellets of different sizes were prepared by extrusion process using a new radial impregnation die, and subsequently, pellets were injection molded as described in previous publication 1. The content of glass fiber reinforcement was maintained same for all compositions. Maleic‐anhydride grafted polypropylene (MA‐g‐PP) was chosen as a compatibilizer to increase the adhesion between glass fiber and PP matrix and its content was maintained at 2 wt%. Notched izod impact property was studied for LFPP composites prepared with and without compatibilizer for different pellet sizes. Failure mechanism due to sudden impact was analyzed with scanning electron micrographs and was correlated with impact property of LFPP composites. Fracture and failure behavior of injection molded LFPP composite were studied and relationship between fracture toughness and microstructure of LFPP composite was analyzed. The microstructure of the composites was characterized by the dimensionless reinforcing effectiveness parameter, which accounts for the influence of fiber layer structure, fiber alignment, fiber volume fraction, fiber length distribution, and aspect ratio. Matrix stress condition factor and energy absorption ratio were determined for LFPP composites prepared with and without compatibilizer. Failure mechanism of both the matrix and fiber, revealed with SEM images, were discussed. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers

Topology optimization of energy-absorbing structures

This paper presents a method for and examples of topology optimization of energy absorption structures. The topology optimization problem is solved by using the elements as design variables. The sensitivity number of an element is derived from using an adjoint method to address two principal design parameters, namely absorbed energy per unit volume, e 1, and absorbed energy ratio, e 2. Filter techniques are employed to smooth sensitivities in the design space and to eliminate unnecessary structural details below a certain length-scale. The bi-directional evolutionary optimization (BESO) technique is used to search for the optimal design in the whole design domain by gradually removing and adding material. Several examples are presented to demonstrate the capability and effectiveness of the proposed method.

Radiological properties of normoxic polymer gel dosimeters

The radiological properties of the normoxic polymer gel dosimeters MAGIC, MAGAS, and MAGAT [methacrylic and ascorbic acid in gelatin initiated by copper; methacrylic acid gelatine gel with ascorbic acid; and methacrylic acid gelatine and tetrakis (hydroxymethyl) phosphonium chloride, respectively] have been investigated. The radiological water equivalence was determined by comparing the polymer gel macroscopic photon and electron interaction cross sections over the energy range from 10 keV to 20 MeV and by Monte Carlo modeling of depth doses. Normoxic polymer gel dosimeters have a high gelatine and monomer concentration and therefore mass density (kg m(-3)) up to 3.8% higher than water. This results in differences between the cross-section ratios of the normoxic polymer gels and water of up to 3% for the attenuation, energy absorption, and collision stopping power coefficient ratios through the Compton dominant energy range. The mass cross-section ratios were within 2% of water except for the mass attenuation and energy absorption coefficients ratios, which showed differences with water of up to 6% for energies less than 100 keV. Monte Carlo modeling was undertaken for the polymer gel dosimeters to model the electron and photon transport resulting from a 6 MV photon beam. The absolute percentage differences between gel and water were within 1% and the relative percentage differences were within 3.5%. The results show that the MAGAT gel formulation is the most radiological water equivalent of the normoxic polymer gel dosimeters investigated due to its lower mass density measurement compared with MAGAS and MAGIC gels.