Plastic Energy Absorption Research Articles

Performance of crumb rubber concrete composite-deck slabs in 4-point-bending

A composite slab reinforced by profiled steel deck is a structural system where the longitudinal shear resistance between the steel deck and the concrete is the critical factor that governs the member capacity of the slabs under shear and/or flexural loads. Partially replacing concrete sand by crumbed rubber particles derived from used tyres to form crumb rubber concrete (CRC) can adversely affect the concrete mechanical characteristics; however, the plastic energy absorption and ductility of CRC have been shown to be improved. This paper presents an experimental study of large-scale composite slabs made of CRC or conventional concrete (CC) at similar compressive strength of 25 MPa that were tested under 4-point bending. Different shear spans and loading schemes were applied and tested in this study. The slabs were all 130 mm thick and had 3400 mm full span (800 mm shear span) for long slabs and 1800 mm full span (400 mm shear span) for short slabs. The overall performances, load carrying capacity, end-slippage, and interaction with steel of the tested CRC slabs were comparable or even better than those of the corresponding CC slabs, which indicated the viable substitution of CRC in composite slabs.

Influences of relative density and strain rate on the mechanical properties of Al-cenosphere-SWNTs hybrid foams

In the present study, single-walled carbon nanotubes (SWNTs) and cenosphere reinforced closed cell hybrid aluminium foams (HAFs) of varying relative densities were produced, and their compressive deformation behaviour at different strain rates have been examined. The addition of SWNTs leads to a significant increase in plateau stress, plastic collapse stress, and energy absorption. This may be due to higher dislocation density and finer inter-SWNT spacing. The Raman spectra of HAFs showed the uniform distribution of SWNTs in the cell wall region. However, the effect of quasi-static strain rates (10−3 to 10 s−1) on the compressive deformation response is marginal. While the influences of higher strain rate ranges (10−3 to 1500 s−1) are considerably higher than the quasi-static strain rate range. The strain rate sensitivity of these foams is much less than unity (~0.0088-0.0314), indicating the brittle nature of foam deformation. The plastic collapse, plateau stress, and energy absorption of HAFs increase significantly with an increase in relative density. Interestingly, it is observed that both plateau stress and energy absorption follow power-law relation with relative density, and densification strain follows a linear relation with relative density irrespective of strain rate and foam material. It is further noted that the strain rate sensitivity of HAFs increases marginally with relative density. The deformation mechanism of HAFs has been examined using the digital photographs captured during the uniaxial compression test and the SEM, TEM images of deformed specimens.

Plastic deformation and energy absorption of polycrystalline-like lattice structures

Polycrystalline-like (PL) lattices are potential energy-absorbing structures composed of basic periodic mono-crystals arranged in different orientations. A series of numerical simulations were conducted to investigate the in-plane crushing resistance and energy absorption of different polycrystalline-like lattice structures. The finite element modelling (FEM) results clearly reveal that the PL lattice structures provide more excellent impact resistance and energy absorbing efficiency compared with conventional monocrystalline (MC) lattices. Compared with the four-cell ML lattice structure, the nine-cell PL lattice structures improve the mean crushing force (MCF) and specific energy absorption (SEA) by 1.5 times, and can effectively suppress the growth rate of the initial peak force (PF). The improvements in the MCF and the SEA originate from the grain boundaries of the PL lattice structures which restrain the evolution of the shear bands and change the shear failure mode of the MC lattice structures into a layer-by-layer progressive crushing mode.

Experimental and numerical analyses of elastic-plastic responses of ship plates under ice floe impacts

Due to ice floe impacts or iceberg collisions, the side structures of ships and offshore platforms operating in Arctic region may experience permanent deformations, which may have significant influences on their structural safety and working performance. To provide insight into the plastic deformations of plates, this paper investigates the nonlinear elastic-plastic responses of plates impacted by an ice wedge striker and an idealized rigid striker by both experimental and numerical methods. The ice material model based on a soil and concrete material model is used in ANSYS/LS-DYNA program to simulate the ice mechanical behaviour in an ice-plate impact scenario. Good correlation is obtained between the experimental, numerical and analytical results for plastic deformations of plate and collision forces. The comparisons of elastic-plastic responses of plate under these two strikers are conducted by both model tests and numerical simulations. Besides, a series of numerical calculations are carried out to study the differences of ice-plate impact and rigid striker-plate impact. The plastic deformations and energy absorption of plate, energy dissipation of ice damage are investigated. Moreover, for these specific cases studied, an energy absorption reduction factor (EARF) of plate under ice impact compared to rigid striker impact is proposed to estimate the structural damage, which provide some useful information for the design of ship plate against ice impact.

A Multi-Cell Hybrid Approach to Elevate the Energy Absorption of Micro-Lattice Materials.

Multi-cell hybrid micro-lattice materials, in which the stretching dominated octet cells were adopted as the strengthen phase while the bending dominated body centered cubic (BCC) lattice was chosen as the soft matrix, were proposed to achieve superior mechanical properties and energy absorption performance. Both stochastic and symmetric distribution of octet cells in the BCC lattice were considered. The cell assembly micromechanics finite element model (FEM) was built and validated by the experimental results. Accordingly, virtual tests were conducted to reveal the stress–strain relationship and deformation patterns of the hybrid lattice specimens. Meanwhile, the influence of reinforcement volume fraction and strut material on the energy absorption ability of the specimens was analyzed. It was concluded that the reinforced octet cells could be adopted to elevate the elastic modulus and collapse strength of the pure BCC micro-lattice material. The multi-cell design could lead to strain hardening in the plateau stress region which resulted in higher plateau stresses and energy absorption capacities. Besides, the symmetric distribution of reinforcements would cause significant stress fluctuations in the plateau region. The obtained results demonstrated that the multi-cell hybrid lattice architectures could be applied to tailor the mechanical behavior and plastic energy absorption performance of micro-lattice materials.

Compressive deformation and corrosion behaviour of moderate to highly porous Ti4Al4Co (wt%) alloy foam

Porous Ti4Al4Co (wt%) alloy of different porosities were prepared through space holder technique. Effect of porosity on pore morphology, compressive deformation and corrosion behaviour of the foams were investigated. The prepared foams were characterized by XRD, FESEM and EDS to investigate the phase formation, pore morphology and elemental distribution. Compression test was performed to study the compressive deformation behaviour of the foams. Electrochemical and weight loss methods were used to investigate the corrosion behavior. From compression test, it was analyzed that plastic collapse stress, elastic modulus and energy absorption capacity reduce with the increment of porosity and follow the power law relationship. While, the densification strain increases linearly with porosity. On the other hand, increase in porosity imparts an adverse effect on the corrosion resistance of the material. The corrosion rate was found to be more susceptible to the foam samples having higher porosity. Microstructure of the corroded surface was in well accordance with the corrosion behaviour observed from the electrochemical method.

Design and modelling of auxetic double arrowhead honeycomb core sandwich panels for performance improvement under air blast loading

In the present study, a 2D-based large-scale metallic auxetic double arrowhead honeycomb core sandwich panel (DAHSP) was proposed and its deformation response, energy dissipation characteristics and associated mechanisms under air blasts were investigated using a validated numerical model. It aims at the performance improvement of DAHSPs through the design of core relative density with respect to different strategies. The DAHSPs considered mainly experienced a local dome superimposed upon global deformation of front face and global deformation of back face, while the core webs were heavily buckled and progressively collapsed. The results confirmed the material concentration effect of DAH cores induced by the negative Poisson’s ratio (NPR). It was found that the panel deformation response was highly related to their deformation/failure mechanisms. Relative to core web thickness, the increase of number of core layers led to a more remarkable decrease in permanent deflections. However, the decline of inclined angles not always reduced the back face deflection due to the competition between enhanced bending stiffness and deteriorated local contact force. An ideal means to decrease the panel deformation is to enlarge the inclined angles at low relative density but to decrease the horizontal distance when the relative density increases to a high level. The panel with thinner core webs at low relative density and the panel with narrowed inclined angles at high relative density is more beneficial to plastic energy absorption. In addition, a core configuration with a thinner tendon but a thicker stuffer promoted the exploitation of NPR and further improved the panel energy absorption.

Multi-morphology lattices lead to improved plastic energy absorption

While lattice metamaterials can achieve exceptional energy absorption by tailoring periodically distributed heterogeneous unit cells, relatively little focus has been placed on engineering heterogeneity above the unit-cell level. In this work, the energy-absorption performance of lattice metamaterials with a heterogeneous spatial layout of different unit cell architectures was studied. Such multi-morphology lattices can harness the distinct mechanical properties of different unit cells while being composed out of a single base material. A rational design approach was developed to explore the design space of these lattices, inspiring a non-intuitive design which was evaluated alongside designs based on mixture rules. Fabrication was carried out using two different base materials: 316L stainless steel and Vero White photopolymer. Results show that multi-morphology lattices can be used to achieve higher specific energy absorption than homogeneous lattice metamaterials. Additionally, it is shown that a rational design approach can inspire multi-morphology lattices which exceed rule-of-mixtures expectations.

Mechanical response of textile reinforced cementitious composite tubes under monotonic and cyclic loadings

This paper presents an experimental and numerical assessment of cylindrical tube-shaped textile reinforced cementitious composites (TRCCs). The TRCC is formed as tube-shaped members. The analyses of TRCC tubes involve the effects of layer numbers and types of textile fibers as the reinforcement. Monotonic and cyclic tests are conducted laterally in the vertical direction. Monotonic compression tests are simulated with using the finite element code and the Microplane Model (M7), as the constitutive damage law for the mortar. The experimental and numerical results show that the number of layers and mortar thickness play significant roles in plastic behaviors, energy absorption, and strength of the tube-shaped forms of textile composites. The critical points and cracking patterns of the TRCC tubes are analyzed in detail. The obtained results of this study can be used to assess the mechanical performance of TRCC tubes. The main conclusion drawn from this study is that utilizing the TRCC tubes in some particular applications might be useful compared to the other conventional composites.

Plastic and energy absorption behavior of compressed circular rings with locally nanocrystallized segments

By utilizing the technology of surface nanocrystallization, the distribution of mechanical properties on metal structures can be changed. In this paper, a theoretical study is presented to investigate the large plastic deformation and energy absorption behavior of circular rings with locally nanocrystallized segments crushed between two rigid, flat plates. The theoretical results are compared with the finite element analysis and a good agreement is obtained when the structural plastic deformation is not too large. The results show that the deformation modes of locally nanocrystallized circular rings are quite different from those of circular rings made of conventional coarse-grained poly-crystalline materials. The dependence of load-deflection relationship and typical energy absorption metrics of circular rings on several key material parameters and distribution strategy of locally nanocrystallized segments is discussed. Through properly designing the distribution of locally nanocrystallized segments, the crushing behaviors of circular rings can be optimized and the comprehensive energy absorption performance can be significantly improved. The present theoretical study can serve as guidance for developing superior energy absorbers utilizing modern advanced material processing techniques.

Assessment of performance criteria of reinforced concrete beams retrofitted with FRP fabrics subjected to extreme impulsive loading

The study performed in this paper is limited to the reinforced concrete structures, in which the behavior of reinforced concrete beams retrofitted with FRP fabrics subjected to extreme loading is investigated. In this regard, numerical modeling using finite element software LS-DYNA is carried out. Numerical results are validated against the results of laboratory experiments. Strengthening of beams with an external composite layer of carbon, glass and Kevlar fibers are considered. Common performance criteria of concrete members such as deflection ratio, support rotation, and ductility ratio as well as crack pattern and energy absorption are investigated. Results show full wrapping mode with carbon fibers leads to the most reductions in the growth of flexural cracks as well as flexural-shear cracks along the free span of the beam. The ductility of the beam is reduced in different states of retrofitting, which the greatest amount of ductility reduction is obtained when reinforced with carbon fibers. Elastic and plastic energies absorbed by the retrofitted beam are, respectively, increased and decreased in all of the investigated cases. Retrofitting with carbon fibers in different states shows the largest increase in the absorption of elastic energy and also the greatest reduction in the plastic energy absorption.

On the out-of-plane ballistic performances of hexagonal, reentrant, square, triangular and circular honeycomb panels

Ballistic penetration is a serious threat to military vehicles. Honeycomb structure is one of the most focused solution to improve the ballistic performance due to its great lightweight design and high resistant against impact. There are lots of honeycomb structure topologies. However, no comprehensive comparison on out-of-plane ballistic performance between common honeycomb types had been conducted to our knowledge. Therefore, hexagonal, reentrant, square, triangle and two circular (CS and CH types) honeycomb structures with identical mass and thickness are developed and modelled in this paper. Their relative densities are firstly calculated. Their numerical models and the Lambert-Jonas ballistic model are established. The ballistic performances of these six cases impacted by a blunt nose cylinder projectile from out-of-plane direction are detailed compared through numerical method. Their dynamic response, elastic and plastic deformation, failure mechanism and energy absorption capability are researched. Relations between initial velocity and residual velocity of projectile and the ballistic limit velocities of all cases are also compared. The results indicated that reentrant, square and triangular cases perform worse than hexagonal honeycomb. The fascinating deformation mechanism of CS and CH cases results in a long elastic deformation time and high strength after elastic deformation, which leads to a large decrease in residual velocity. Compared with hexagonal honeycomb, ballistic limit velocities of CS and CH type are improved by 15.2% and 25.0%, respectively. This comparison research provides a useful reference for sandwich honeycomb core design.

Corrosion Susceptibility and Functionally Graded Properties of Ti-35Nb-4Sn Alloy Processed by Laser Remelting

The effect of laser remelting on the corrosion susceptibility and mechanical properties of Ti-35Nb-4Sn (mass%) alloy is investigated across the remelted track profile. In comparison to the cold-rolled microstructure of base metal, recrystallization of heat affected zone (HAZ) improved plastic energy absorption and pitting corrosion resistance, by the reduction of active sites for pit nucleation. In fusion zone, however, passivation was compromised by the formation of dendritic microstructure with Sn enriched interdendritic region, where preferential pitting corrosion occurred. Fusion zone was the most anodic region and presented a corrosion potential difference of 35 mV, in comparison to the adjacent and most cathodic HAZ. Electrochemical impedance analysis showed that spontaneous passivation was most effective in base metal, that developed a thicker and more compact passive film. Local increase in elastic modulus and microhardness of fusion zone shows that laser remelting is a viable processing route for the manufacturing of biomaterials with functionally graded properties.

Characteristics of expanded polystyrene (EPS) and its impact on mechanical and thermal performance of insulated concrete form (ICF) system

Fast track construction with enhanced quality, sustainable and environment-friendly methods and materials are much sought after in the construction industry. Insulated concrete form (ICF) is an evolving technique that could satisfy the present demand of the construction industry. ICF is a composite of concrete and expanded polystyrene (EPS), which enhances the insulation and other mechanical properties to the building. The objective of this study is to explore the compressive and flexural characteristics of EPS and ICF blocks under standard loading condition and evaluate the thermal performance of ICF panels using R-value. Plastic deformation, failure and energy absorption behavior of EPS and ICF blocks are assessed using compressive stress-strain profiles. The experimental results show that the plastic deformation of the ICF block is 78 times higher than plain concrete block. The presence of EPS in ICF helps to change the failure nature of sandwiched concrete from brittle to ductile, which is quantified in terms of plastic deformation. A simplified experimental approach is proposed to study the thermal performance of ICF panel using R-value. The proposed design is effective to measure the thermal resistance of wall panels and the obtained R-value of the ICF panel is 5.22 m2.K/W which is 7.9 times higher than the plain concrete panel. The higher R-value of ICF provides greater insulation to the building by keeping the controlled temperature for longer periods. This thermal insulation behavior of ICF reduces power demand and makes the building more energy-efficient. Thus the ICF system helps in sustainable building construction by affording high thermal insulation with improved structural strength.

Synergic effect of MWCNTs and SiC addition on microstructure and mechanical properties of closed-cell Al–SiC-MWCNTs HCFs

AlSi12Cu1Mg1–SiC-MWCNTs hybrid composite foam (HCFs) of varying relative densities (R.D.) were made through stir casting technique using CaH2 as a foaming agent. Varying wt.% of SiC and multi-wall carbon nanotubes (MWCNTs) were used as reinforcing as well as thickening agents. Uniform distribution of SiC and MWCNTs in the matrix was confirmed by FESEM images and Raman analysis. It was observed that the elastic modulus (E), plastic collapse stress (σpc), plateau stress (σpl), and energy absorption (Eab) of HCFs increase significantly when both (MWCNTs and SiC) were added together. But, when SiC and MWCNTs added individually, the extent of improvement in these properties is relatively low. However, densification strain varies marginally with the variation in reinforcement. Irrespective of reinforcement, the σpl, the E, and the Eab increased with increment in R.D. The different values also followed the existing relations, when the fraction of cell edge materials varied with R.D., the deformation mechanism was understood from photographs taken during deformation.

Numerical study of low-speed impact response of sandwich panel with tube filled honeycomb core

Sandwich panel with Honeycomb Filled with Circular Tubes (HFCT) as core is numerically investigated by using ABAQUS/Explicit in this study. To calibrate the numerical model, the panels equipped with conventional hexagon honeycomb cores are modeled. Good agreement between numerical and experimental results is achieved. The sandwich panels with HFCT are compared with the sandwich panels with Honeycomb and Multi-tube cores of identical mass subjected to vertical and oblique impacts. The maximum displacement of face-sheets, plastic energy absorption, boundary reaction forces and impact load time history are calculated to assess the impact resistant capacity. The panel with HFCT core has smaller rear face-sheet displacement and higher energy absorption capacity as compared to the panels with the Multi-tube and Honeycomb core. Under oblique impact, both HFCT and Multi-tube panels have superior impact resistant capacity than the Honeycomb panel. In addition, the impact resistances of four types of multi-arc tube filled Honeycomb (HFMT) are also analysed. Their performances under vertical and oblique impacts are compared with those of HFCT.

A comparative study on compressive deformation and corrosion behaviour of heat treated Ti4wt%Al foam of different porosity made of milled and unmilled powders

Ti4wt%Al alloy foams of various porosities were prepared using milled and unmilled powders through space holder technique. Crystallographic and morphological change in milled powder compared to the unmilled one were also examined. Space holder content was varied to get foams of different porosities. After sintering, foams were thermally oxidized through heat treatment and characterised in terms of their pore size, pore morphology, pore interconnectivity, phase formation and compressive deformation behaviour. It was observed that plastic collapse stress, elastic modulus, plateau stress and energy absorption capacity are strong function of porosity and these are higher for the foam made of milled powder (Mf) than those of the foam made of unmilled one (Uf). Corrosion behaviour of these foams were examined. Open circuit potential, Tafel plot and electrochemical impedance spectroscopy confirm that Mf has higher corrosion resistance than Uf for the same porosity level. Also, with increasing porosity, corrosion resistance of the foam samples reduces.

Influence of Cell Anisotropy and Relative Density on Compressive Deformation Responses of LM13-Cenosphere Hybrid Foam

This article deals with closed-cell aluminum alloy LM13-cenosphere hybrid foams (ACHFs) with cell anisotropy prepared through stir casing technique. The compressive deformation behavior of hybrid foams in both transverse and longitudinal directions was measured at a strain rate of 0.01/s. The hybrid foam loaded in longitudinal direction (LD) shows higher plastic collapse stress than that in transverse direction (TD). The stress drop ratio is also observed to be higher in the LD. The plastic collapse stress and energy absorption capacity of ACHFs follow the power law relationship with relative density in both the directions. The plateau stress is higher in case of LD and densification strains are marginally higher in case of LD than that in TD.

Metallic Glass Structures for Mechanical-Energy-Dissipation Purpose: A Review

Metallic glasses (MGs), a new class of advanced structural materials with extraordinary mechanical properties, such as high strength approaching the theoretical value and an elastic limit several times larger than the conventional metals, are being used to develop cellular structures with excellent mechanical-energy-dissipation performance. In this paper, the research progress on the development of MG structures for energy-dissipation applications is reviewed, including MG foams, MG honeycombs, cellular MGs with macroscopic cellular structures, microscopic MG lattice structures and kirigami MG structures. MG structures not only have high plastic energy absorption capacity superior to conventional cellular metals, but also demonstrate great potential for storing the elastic energy during cyclic loading. The deformation behavior as well as the mechanisms for the excellent energy-dissipation performance of varying kinds MG structures is compared and discussed. Suggestions on the future development/optimization of MG structures for enhanced energy-dissipation performance are proposed, which can be helpful for exploring the widespread structural-application of MGs.

Plastic collapse and energy absorption of empty circular aluminum tube under transverse quasi-static loading

This paper presents an experimental investigation on plastic collapse and energy absorption of empty circular aluminum tubes under quasi-static transverse loading. Tubular structures being a critical demand as material saving, high energy absorption and good strength characteristics were of major concerns due to its wall thinness, and so, its various diameter-to-thickness (D/t) ratios and span lengths. Studies found that empty circular Al-tube structure subjected to transverse standard three-point bending loading undergone three plastic deformation phases, starting with crumpling phase, crumpling and buckling phase, and lastly the structural collapse. The results found that energy absorption of empty aluminum tubes for a constant D/t ratio decreases as span length. On the contrary, the energy absorption of empty aluminum tubes for a given constant span length increases with the increase in D/t ratio.