Energy Absorption Ratio Research Articles

Improved heterogeneity handling in the collapsed cone dose engine for brachytherapy.

Model-based dose calculation algorithms (MBDCA), such as the Advanced Collapsed cone Engine (ACE) in Oncentra Brachy® can be used to overcome the limitations of the TG-43 formalism. ACE is a point kernel superposition algorithm that calculates the total dose separated into primary, first-scatter, and multiple-scatter dose. Albeit ACE yields accurate results under most circumstances, several studies have reported underestimations of the dose to cortical bone. These underestimations are likely caused by approximations in the handling of multiple-scatter dose for non-water media. Such would result in noticeable deviations where the multiple-scatter is a considerable fraction of the total dose, that is, at greater distances from the source. To improve and test the accuracy of the multiple-scatter dose component in the ACE algorithm to remedy its inaccuracy for non-water geometries. A careful analysis of the transport and absorption of the multiple-scatter energy fluence revealed an inconsistency in the scaling of energy absorption ratios for non-water media of the multiple-scatter kernel. We implemented an updated algorithm version, ACEcorr, and tested it for three different geometries. All had a single 192Ir-source at the center of a cubic water phantom with a box-shaped heterogeneity of either cortical bone or air, positioned at different distances from the source. Dose distributions for the three cases were calculated with ACE and ACEcorr and compared to Monte Carlo simulations, using the percentage dose difference ratio as figure-of-merit. All dose calculation methods scored separately the dose deposited by primary, first-scattered, and multiple-scattered photons. The accuracy of the updated algorithm ACEcorr was superior to ACE. In the cortical bone heterogeneity, the mean percentage dose difference ratio for the total dose improved from to (in the worst case) by our update. Less impact was seen in the air heterogeneity, where both ACE and ACEcorr deviated less than 2% from the Monte Carlo results. The algorithm update mainly concerns the multiple-scattered dose component, but an accompanying data processing update also had a small effect ( 0.5% difference) on the primary and first-scattered dose. The calculation times were not affected. The updates to ACE improved the accuracy of multiple-scatter dose calculation for non-water media, without increasing calculation times.

Multi-mode hybridization in the MXene tetramer metasurface for ultra-broadband solar energy utilization

MXene is promising in photothermal or photovoltaic conversion, while high-performance MXene metasurface solar absorbers based on simple and feasible structures are still lacking. This study aims to design a solar absorber with ultra-broadband absorption capability in the visible and near-infrared wavelength ranges based on the MXene nanoblock tetramer/silica film/MXene substrate structure. The average absorptivity of this proposed metasurface absorber is 96.9% in the wavelength range of 300–2500 nm covering the whole solar spectrum. The physics behind the high absorption results from multiple-mode hybridization in different resonant bands, including the coupling between the surface plasmons, cavity resonances, and guided-mode resonances. The broadband and high-absorption performance remains stable under large-angle incidence and structural parameter variations with the average absorption above 90% in the whole wavelength region of interest. The calculated energy absorption ratio of the AM1.5 solar radiation spectrum can reach up to 96.3%, indicating low solar energy loss and efficient solar energy capture. In summary, these results provide great application prospects in the fields of photothermal and photovoltaic conversion.

Experimental Research on Dynamic Mechanical Properties of High-Density Foamed Concrete.

Foamed concrete is increasingly utilized in protection engineering because it offers a high energy absorption ratio and a relatively low construction cost. To investigate the dynamic properties of foamed concrete, a series of dynamic compression tests are carried out on high-density foamed concrete with densities of 800 kg/m3, 1000 kg/m3, and 1100 kg/m3 under a strain rate range of 59.05 s-1~302.17 s-1 by using a Φ-100 mm split Hopkinson pressure bar (SHPB) device. The effects of strain rate on the stress-strain relationship, dynamic compressive strength, and dynamic increase factor of foamed concrete are discussed in detail. The results show that the dynamic mechanical characteristics of foamed concrete with different densities exhibit a significant strain rate enhancement effect. Additionally, the energy absorption characteristics of foamed concrete are investigated, demonstrating that it can effectively prevent the transmission of incident energy and that its energy absorption efficiency declines as the strain rate increases. A high-speed camera was also employed to capture the failure process of foamed concrete. The results exhibit that fracture production and development induce the failure of foamed concrete, the failure process of foamed concrete advances as the strain rate increases, and the failure mode becomes increasingly severe.

Application of a novel machine learning model for the prediction and optimization of anti-blast performance of sandwich honeycomb blast walls

Sandwich honeycomb blast wall with the superior energy absorption characteristics could be applied to anti-blast protection of offshore oil and gas platform. Recently, machine learning technique, as an alternative to traditional Finite Element Analysis (FEA), is becoming a powerful tool in understanding structural performance. The aim of this study is to propose a novel data-driven model for fast predictions of structure response of sandwich blast wall under explosion, including the maximum deformation δmax, the maximum internal energy Emax and the energy absorption ratio RE. FEA was firstly conducted to generate sample data for the proposed model by using LS-DYNA software. An improved artificial electric field algorithm (IAEFA) was combined with artificial neural network (ANN) to develop an IAEFA-ANN model. In case studies, the prediction results of IAEFA-ANN approximate the results of FEA well, and comparison results of 9 different ANN models demonstrate that IAEFA-ANN model has the best performance. Then, the effects of explosion parameters (including explosive charge mass Me, stand-off distance d and concave angles θ) on structural response prediction results were investigated by using the proposed model. Moreover, the IAEFA-ANN model was applied to conducting optimal design of the blast wall to obtain optimum anti-blast performance.

Mechanical Properties of Re-Entrant Hybrid Honeycomb Structures for Morphing Wings.

The exceptional energy absorption, deformability, and tuneable Poisson's ratio properties of negative Poisson's ratio (NPR) honeycomb biomimetic structures make them highly suitable for applications in aerospace, medical, and acoustic stealth industries. The present study proposes a re-entrant hybrid honeycomb (REHH) structure comprising a re-entrant octagonal unit cell and a re-entrant hexagonal unit cell. Theoretical models of the in-plane elastic modulus and Poisson's ratio are established based on beam theory, and these models are validated through finite element (FE) simulations and tensile experiments conducted on the REHH samples. The influence of the cell geometry parameters on the in-plane elastic behaviours is investigated. The results indicate that the NPR performance of the REHH structure exhibits superior deformation capability compared with the four-point star hybrid honeycomb (FSHH) structure. The experimental REHH structure samples exhibit significant tensile displacement capabilities in the x-direction.

Cushioning property and structure optimization of double-arrow sandwich composite based on modified genetic algorithm

Owing to the ability of negative Poisson’s ratio (NPR) structures in enhancing the stiffening effectof shear stiffening gels (SSG), combining the two in cushioning applications has attracted much attention. This paper presents the design of NPR flexible cushioning sandwich composites featuring a double-arrow structure (DAS). The DAS is optimized using a modified genetic algorithm, and the cohesive property is leveraged to reinforce the stiffening effect of SSG, thereby improving the material’s cushioning efficiency. The synergistic effect of the DAS and SSG and the law of SSG arrangement on the energy absorption efficiency of cushioning were revealed using the finite element method and experiment. It can be found that the size effect of the DAS significantly contributed to the enhancement of the energy-absorption efficiency of the SSG stiffening. In double-arrow sandwich composite (DASC), the larger reversed-triangle deformation and the increased number of reversed-triangle configurations, amplified the shear stiffening of the SSG, improving the impact load dissipation and energy absorption efficiency of sandwich composite. The energy absorption efficiency of the DASC was improved owing to the synergistic effect of the DAS cohesive effect and the SSG stiffening properties, with the energy absorption ratio and mass specific energy absorption increased by 83.02% and 136% compared to neat polyurethane. The DASC optimized in this study has good flexibility and energy absorption capacity and is promising for application in the field of flexible protection.

Experimental investigation on the horizontal impact response of precast RC bridge piers with grouted sleeve connections considering defects

To investigate the behaviour of precast bridge piers with grouted sleeve connections under horizontal low-velocity impact loads, twelve precast reinforced concrete (RC) bridge pier specimens and two cast-in-place reference specimens were tested to study the effect of grouting defect degree, impact velocity and fabricated method (precast vs. cast-in-place) on the impact response of RC piers. The failure modes, rebar strains, impact forces, displacement, and energy dissipation capacity of both cast-in-place and precast specimens were compared and analyzed. The results indicate that due to inertial effects induced by impact loading, the peak impact forces were three to seven times greater than the peak static loads. Transverse cracks were more likely to initiate in the grout layer for precast specimens, with diagonal cracks extending from the loading position to the pier bottom after impact. As horizontal impact velocity increased, the impact force, maximum displacement, and energy absorption ratio also significantly increased. The impact force-time curves of the pier specimens with grouting fullness ranging from 30 % to 100 % showed minimal differences compared to the cast-in-place specimen. A decrease in grouting fullness led to an increase in the maximum displacement of the pier specimens and reduced the transmission of impact waves between the reinforcement bars.

The impact of the coupling relationship between projectile size and yarn dimension on the ballistic performance of plain weave fabric

Aramid fibers, due to their relatively high inter-yarn friction, high strength, high modulus, and other characteristics, have become a typical representative of flexible anti-ballistic materials in modern warfare. Current research on the anti-penetration of aramid fabrics mostly focuses unilaterally on the structure and performance of aramid fabrics or the shape and size of projectiles, with fewer studies on the coupled effect of both on ballistic performance. This study analyzes how the coupling relationship (or size effect) between the projectile and fiber bundle dimensions affects the fabric ballistic performance from a mesoscopic scale perspective. Taking plain weave aramid fabric as the research object, considering different diameter projectiles, through a large number of ballistic impact tests and numerical simulations, parameters such as ballistic limit velocity, average energy absorption of fabric, and specific energy absorption ratio (average energy absorption of fabric divided by projectile cross-sectional area) are obtained for ballistic performance analysis. The influence law of projectile size on the ballistic performance of high-performance fabrics is as follows: The relative range of fitted ballistic limit velocity at different target positions gradually decreases and then stabilizes as the projectile diameter increases, indicating that the fabric structure effect gradually disappears at a projectile diameter of 12 mm; The average ballistic limit velocity at three impact positions, P1, P2, and P3, provides the corresponding ballistic limit velocity for 1000D aramid fabric, which increases with projectile diameter but the rate of increase slows down at an inflection point, which in this study occurs where the fabric structure effect nearly disappears at a projectile diameter of 12 mm; The energy absorption ratio increases and then decreases as the projectile diameter increases from 4 mm to 20 mm, reaching a peak at the diameter of 12 mm due to the gradual disappearance of the fabric structural effect. The projectile diameter of 12 mm corresponds to the coupling size of 11.159, which provides a size design reference for the macroscopic-based continuum models of aramid plain weave fabrics.

A novel method for optimizing energy absorption of tensegrities with multi- self-stress modes

To explore the factors that affect the energy absorption performance of tensegrities with multi-self-stress modes, the Beetle Antennae Genetic Algorithm (BAGA) is carried out in developing reasonable energy absorption optimization strategies. In the first stage, based on the form-finding theory, the initial self-stress (including prestress level and distribution) that meets unilateral property of components was found. Then, the maximum energy that the structure can absorb under vertical loads is taken as the objective function, and constraint conditions regarding cable relaxation, elastic failure, global volume, strut buckling and component collision are considered in obtaining the satisfactory optimal initial self-stress. Finally, three tensegrities with multi-self-stress modes are taken as illustrative examples, the impact of optimal prestress level and the corresponding distribution on the structural energy absorption performance are explored. The results indicate that, for a 18-rod tensegrity and two types of assembled complicated tensegrity, the energy absorption can be respectively increased by about 156.88 %, 50.75 % and 131.09 % with simultaneously optimizing the pre-stress level and its distribution, verifying the effectiveness of the proposed algorithm. Additionally, for the assembled complicated tensegrity constructed using two different assembling ways (corresponding to different assembled prestress distributions), the optimal structural energy absorption ratio can be as high as 1.88 times.

A comprehensive review of experimental studies on shear behavior of bolted rock joints with varying rock joint and bolt parameters and normal stress

AbstractThe shear characteristics of bolted rock joints are crucial for the stability of tunneling and mining, particularly in deep underground engineering, where rock bolt materials are exposed to high stress, water pressure, and engineering disturbance. However, due to the complex interaction between bolted rock joints and various geological contexts, many challenges and unsolved problems arise. Therefore, more investigation is needed to understand the shear performance of bolted joints in the field of deep underground engineering. This study presents a comprehensive review of research findings on the responses of bolted joints subjected to shearing under different conditions. As is revealed, the average shear strength of bolted rock joints increases linearly with the normal stress and increases with the compressive strength of rock until it reaches a stable value. The joint roughness coefficient (JRC) affects the contact area, friction force, shear strength, bending angle, and axial force of bolted rock joints. A mathematical function is proposed to model the relationship between JRC, normal load, and shear strength. The normal stress level also influences the deformation model, load‐carrying capacity, and energy absorption ratio of bolts within bolted rock joints, and can be effectively characterized by a two‐phase exponential equation. Additionally, the angle of the bolts affects the ratio of tensile and shear strength of the bolts, as well as the mechanical behavior of both bolted rock joints and surrounding rock, which favors smaller angles. This comprehensive review of experimental data on the shear behavior of bolted rock joints offers valuable theoretical insights for the development of advanced shear devices and further pertinent investigations.

Impact resistance performance and simplified calculation method of web-opened steel beams under impact loads

To investigate the impact resistance performance of web-opened steel beams (WOSBs) under impact loads, 26 specimens of WOSBs were designed and performed the falling-hammer impact tests, focusing on the impact energy, inter-opening space, opening height, and steel strength. The test results showed that the local deformations of WOSBs exhibited Vierendeel shear deformation and out-of-plane lateral buckling of the web under impact loads. At the initial impact stage, the time delay effect between the peak impact force and the peak reaction force accounts for approximately 9.77% of the total impact duration. The increase in impact energy and opening height had an adverse effect on the impact resistance performance of WOSBs. That is, as the impact energy (or opening height) increases, the average residual displacements for H1, H2, and H3 (H1, H2, and H3 represent WOSBs corresponding to three different steel materials: Q235, Q550, and Q690, respectively) increase by approximately 23.85% (18.07%), 34.05% (24.00%), and 33.20% (37.20%), respectively. The average impact efficiencies for H1, H2, and H3 are 77.38%, 72.90%, and 72.74%, respectively. This indicates that the unique geometric characteristics of WOSBs can be effectively utilized in the design of energy-absorbing structures. In conjunction with current steel structure design standards, a calculation method for the impact resistance performance of WOSBs was proposed by introducing the dynamic amplification factor and energy absorption ratio.

Role of fibre weight fraction on low-velocity impact characteristics of abaca fibre reinforced bio-composites

This work involved an experimental study on Abaca fibre bio-composites subjected to a low-velocity impact test at 2.42 m/s to study the effect of fibre weight fraction on the impact performance. The abaca fibre reinforced composite (AFRC) specimens were fabricated with a 10% increment of fibre, varying from Wf = 20% to 50%, and their impact properties compared with each other. The impact properties such as force-time history, energy-time history, Coefficient of Restitution (CoR), Energy Loss Percentage (ELP) and Energy Absorption Ratio (EAR) were studied. A significant change in impact force and energy absorption was found as the fibre content increased in the composite. The findings show a good relationship between fibre weight fractions, composite laminate stiffness, impact load and total absorbed energy. The experimental results of the impact test show that the composite specimen with Wf = 40% has high impact energy absorption capacity with 4. 09 J 92.94 N and 4.09 J, EAR of 39.94%, CoR of 0.77 and ELP of 40.04%. Low fibre weight fraction composite has shown brittle failure, and high fibre weight fraction has shown ductile behaviour. Scanning electron microscopy (SEM) based study was used for post-impact damage analysis.

A new three-dimensional re-entrant negative Poisson's ratio metamaterial with tunable stiffness

Re-entrant structure, as a branch of mechanical metamaterial, has attracted attention due to its excellent mechanical properties. However, this structure suffers from the defect that the initial stiffness and load capacity are not customizable, which limits its practical application in engineering. Therefore, it is important to study a new type of three-dimensional re-entrant negative Poisson's ratio (NPR) structure that can tailor mechanical features like stiffness, load capacity, and energy absorption, and is suitable for practical engineering applications. In this work, a re-entrant unit with different sizes of γ (re-entrant column clearance) was designed, manufactured, and tested to achieve the adjustability a function of original stiffness and capacity for load by adjusting the size of γ. The accuracy between the finite element results and the actual results was verified through experiments and numerical analysis. In addition, the mechanical properties of the new re-entrant structure were compared with those of the conventional re-entrant structure. Using the verified finite element model, the influence of different structural parameter ratios on the initial stiffness, load capacity, energy absorption, and Poisson's ratio of the new re-entrant structure was analyzed. The results show that different sizes of γ can change the structure's mechanical attributes, realizing the adjustability of mechanical properties and providing a new method for the study of mechanical properties of NPR metamaterial.

Penetration resistance of corrugated hybrid structures with ceramic insertions against steel projectile impact

Ceramic-metal corrugated structures have attracted extensive attention because of their strong penetration resistance. In this study, the effects of geometric features and boundary constraints on corrugated structures consisting of a TC4 frame and five SiC ceramic prisms were explored by performing a series of ballistic tests. Deformation results were obtained using a three-dimensional scanner, and the dynamic response was observed using a high-speed imaging system. Numerical models of these tests were established and validated using experimental results. The results suggest that increasing the support and confining strength of ceramics delay their failure and increase their degree of breakage, thereby increasing the internal energy conversion ratio of the projectile and the energy absorption ratio of ceramics by 14% and 10%, respectively. Notably, a reasonable reduction in the strength of the frame partition expands the plastic deformation range of the frame and increases its energy absorption ratio by 10%. The conclusions of this study provide a reference for designing corrugated composite structures.

Mechanical properties of thermally damaged mortar under coupled static-dynamic loading

In buildings that experience fires, cement mortar is subjected to high-temperature environments and not only the weight of the structure above but also blast loads, leading to structural damage and loss of load-bearing capacity. To investigate the static and dynamic mechanical properties of thermally damaged mortar, a series of tests utilizing modified split Hopkinson pressure bar were conducted. These tests included quasi-static, conventional dynamic and coupled static-dynamic loading tests on mortar specimens that were subjected to seven temperature levels: 20°C, 100°C, 200°C, 300°C, 400°C, 500°C, and 600°C. The test results revealed that both the thermal damage and loading method had an impact on the mechanical properties and damage characteristics of the mortar specimens. The compressive strength, elastic modulus and absorbed energy ratio of mortar decreased as temperature increased. Notably, the quasi-static strength loss rate was 60% when the temperature reached 600°C. Under coupled static-dynamic loading, the specimens exhibited higher strength, elastic modulus, reflected energy ratio, and transmitted energy ratio. Conversely, they had lower average strain rates and absorbed energy ratios. Intriguingly, the dynamic growth factor had a relative increase of 0.7–2.0 compared with other loading methods. Furthermore, the higher temperature, the higher fragmentation of the specimens in the fragmentation pattern. Conventional dynamic loading resulted in the greatest degree of fragmentation. The findings provide a scientific basis for the design and evaluation of concrete shockproof and explosion-resistant structures.

Impact response of lightweight steel foam concrete composite slabs: Experimental, numerical and analytical studies.

This paper presents a study on the low-velocity impact response of lightweight steel foam concrete (LSFC) composite slabs. The LSFC composite slab consisted of a W-shaped steel plate, foam concrete and oriented strand board (OSB). Low-velocity impact tests on the LSFC composite slabs were conducted by employing an ultra-high heavy-duty drop hammer testing machine. The tests revealed the failure mode, impact force and displacement response of LSFC composite slabs. The effects of density and thickness of foam concrete and drop height on the peak impact force and energy absorption ratio were investigated. A finite element (FE) model was set up to predict the impact resistance of the LSFC composite slabs, and a good agreement between simulation and test results was achieved. In addition, an equivalent-single-degree-of-freedom (ESDOF) model was set up to predict the displacement response of the LSFC composite slabs under impact loading.

Experimental study on the mechanical behavior and energy absorption capacity of coral sand at high strain rates

This study investigated and compared the compression responses and energy absorption capacities of coral sand and silica sand at a strain rate of approximately 1000 s−1. To this end, the effects of the relative density and particle size distribution on the abovementioned properties were analyzed, and the stress–strain curves, yield stresses, compressibilities, energy absorption curves, and energy absorption ratios were obtained. The experimental results showed that coral sand had a significantly higher energy absorption capacity than silica sand owing to its higher compressibility. The energy absorption curve for sand was primarily influenced by the yield stress and energy absorption ratio. The lower relative density of coral sand contributed to its higher compressibility and energy absorption capacity compared to silica sand. For coral and silica sands with different particle sizes, the intersection of the stress–strain and energy absorption curves was observed and analyzed. Formulas for predicting the yield stress, compressibility, and energy absorption curve of coral sand were derived, considering the variations in the relative density and particle size. The study findings reveal that using poorly graded coral sand with large particle sizes can improve the energy absorption capacity of coral sand.

Dynamic behaviour of multi-layer composite against single and multiple projectile impact loading

In this work, a novel multi-layer composite structure has been proposed for its application in the design of protective shelters. The proposed work investigates the dynamic behaviour of a multi-layer composite under the action of single and multiple projectile impact loading. The target consists of soil, reinforced concrete, steel plate, high-density polyethylene and boulder-mixed cement mortar. It has been subjected to the projectile impact (single and multiple) of a 2.3 kg ogive-nose hard cylindrical projectile having a 50.80 mm diameter. The mechanical performance in terms of the velocity profile of the projectile, residual velocity, penetration depth, ballistic limit velocity, energy absorption and damage of the target has been quantified through a numerical framework. Further, equations have been formulated to determine the fracture material parameters associated with the Riedel–Hiermaier–Thoma (RHT) model to cater for varying strengths of concrete or similar materials. The proposed composite target has demonstrated enhanced penetration resistance and lesser damage compared to its reinforced concrete monolayer counterpart. The interaction between shock waves and the target’s material characteristics lead to projectile ricocheting in multiple projectile impacts. Further, an analytical model has been developed to predict the forces transmitted to the lowest layer, which are essential for design purposes. The model has been proposed from the fundamentals using the concepts of impedance. The result derived from the theoretical formulation is in good agreement with the numerical results. Finally, the damage has been quantified to assess the extent of structural deterioration in multi-layer targets, emphasizing the relationship between energy absorption ratio and damage.

Ultra-broadband and wide-angle solar absorber with hierarchical nanohole design based on MXene

MXene has received a lot of attention from researchers in the fields of photothermal and photovoltaic due to its excellent optical properties. However, research on MXene-based solar absorbers has rarely been carried out. In this work, we proposed a MXene-based solar absorber with absorption broadband, wide-angle, and polarization insensitive. The absorber has excellent light capture capability, with its average absorption in the solar band as high as 97.8 % and an energy absorption ratio of 98.9 % in the AM1.5 solar radiation spectrum. The electric and magnetic field distributions indicate that the unique hierarchical nanohole design can effectively excite multiple resonance couplings of surface plasmon resonance, cavity resonance, and guided mode resonance. The proposed absorber can still maintain the broadband absorption characteristics within a certain manufacturing tolerances. Moreover, the absorber is insensitive to polarization and has a high light absorption under a large incident angle. We believe that this work holds great promise for solar thermal conversion and heat utilization.

In-plane dynamics crushing of a reinforced honeycomb with enhanced energy absorption

Recently, an increasing interest in reinforced honeycomb structures (RHC) due to their exceptional mechanical properties and potential applications in energy absorption. This paper focuses on the theoretical and numerical study of the in-plane dynamic crushing response of RHC and the reinforced honeycomb structure with one layer of reinforcement and one layer of non-reinforcement(1 + 1RHC). The 1 + 1RHC was fabricated with a welding method. A displacement-controlled in-plane compressive load was applied to the 1 + 1RHC specimens. Three different deformation modes were monitored at varying impact velocities: low-speed, medium-speed, and high-speed modes. The deformation modes maps were developed to reveal the extent of effects by impact velocity and relative density. For 1 + 1RHC, two distinct plateau stress regions were identified at low-velocity impact loading. Additionally, the first plateau stress value of the 1 + 1RHC structure is 180.4% higher than that of structures with two platform stresses, and the second platform stress value is 71.0% higher than that of structures with two platform stresses. The 1 + 1RHC structure exhibits superior energy absorption and negative Poisson's ratio performance. The paper also discusses the impact of cell wall thickness, angle, and velocity on the crushing strength of both RHC and 1 + 1RHC. The results obtained by theoretical methods align well with that obtained from finite element simulations.