Reinforcing effects of polypropylene on energy absorption and fracturing of cement-based tailings backfill under impact loading

Polypropylene(PP)fiber-reinforced cement-based tailings backfill(FRCTB)is a green compound material with superior crack resistance and has good prospects for application in underground mining.However,FRCTB exhibits susceptibility to dynamic events,such as impact ground pressure and blast vibrations.This paper investigates the energy and crack distribution behavior of FRCTB under dynamic impact,considering the height/diameter(H/D)effect.Split Hopkinson pressure bar,industrial computed tomography scan,and scanning electron microscopy(SEM)experiments were carried out on six types of FRCTB.Laboratory outcomes confirmed fiber aggregation at the bottom of specimens.When H/D was less than 0.8,the proportion of PP fibers distributed along theθangle direction of80°-90°increased.For the total energy,all samples presented similar energy absorption,reflectance,and transmittance.However,a rise in H/D may cause a rise in the energy absorption rate of FRCTB during the peak phase.A positive correlation existed between the average strain rate and absorbed energy per unit volume.The increase in H/D resulted in a decreased crack volume fraction of FRCTB.When the H/D was greater than or equal to 0.7,the maximum crack volume fraction of FRCTB was observed close to the incidence plane.Radial cracks were present only in the FRCTB with an H/D ratio of 0.5.Samples with H/D ratios of 0.5 and 0.6 showed similar distributions of weakly and heavily damaged areas.PP fibers can limit the emergence and expansion of cracks by influencing their path.SEM observations revealed considerable differences in the bonding strengths between fibers and the FRCTB.Fibers that adhered particularly well to the substrate were attracted together with the hydration products adhering to surfaces.These results show that FRCTB is promising as a sustainable and green backfill for determining the design properties of mining with backfill.

Dynamic Resistance and Energy Absorption of Sandwich Beam via a Micro-Topology Optimization

The current research of sandwich structures under dynamic loading mainly focus on the response characteristic of structure.The micro-topology of core layers would sufficiently influence the property of sandwich structure.However,the micro deformation and topology mechanism of structural deformation and energy absorption are unclear.In this paper,based on the bi-directional evolutionary structural optimization method and periodic base cell(PBC)technology,a topology optimization frame work is proposed to optimize the core layer of sandwich beams.The objective of the present optimization problem is to maximize shear stiffness of PBC with a volume constraint.The effects of the volume fraction,filter radius,and initial PBC aspect ratio on the micro-topology of the core were discussed.The dynamic response process,core compression,and energy absorption capacity of the sandwich beams under blast impact loading were analyzed by the finite element method.The results demonstrated that the overpressure action stage was coupled with the core compression stage.Under the same loading and mass per unit area,the sandwich beam with a 20%volume fraction core layer had the best blast resistance.The filter radius has a slight effect on the shear stiffness and blast resistances of the sandwich beams.But increasing the filter radius could slightly improve the bending stiffness.Upon changing the initial PBC aspect ratio,there are three ways for PBC evolution:The first is to change the angle between the adjacent bars,the second is to further form holes in the bars,and the third is to combine the first two ways.However,not all three ways can improve the energy absorption capacity of the structure.Changing the aspect ratio of the PBC arbitrarily may lead to worse results.More studies are necessary for further detailed optimization.This research proposes a new topology sandwich beam structure by micro-topology optimization,which has sufficient shear stiffness.The micro mechanism of structural energy absorption is clarified,it is significant for structural energy absorption design.

Influence of manufacturing process-induced geometrical defects on the energy absorption capacity of polymer lattice structures

Modern additive manufacturing processes enable fabricating architected cellular materials of complex shape,which can be used for different purposes.Among them,lattice structures are increasingly used in applications requiring a compromise among lightness and suited mechanical properties,like improved energy absorption capacity and specific stiffness-to-weight and strength-to-weight ratios.A dedicated modeling strategy to assess the energy absorption capacity of lattice structures under uni-axial compression loading is presented in this work.The numerical model is developed in a non-linear framework accounting for the strain rate effect on the mechanical responses of the lattice structure.Four geometries,i.e.,cubic body centered cell,octet cell,rhombic-dodecahedron and truncated cuboctahedron 2+,are investigated.Specifically,the influence of the relative density of the representative volume element of each geometry,the strain-rate dependency of the bulk material and of the presence of the manufacturing process-induced geometrical imperfections on the energy absorption capacity of the lattice structure is investigated.The main outcome of this study points out the importance of correctly integrating geometrical imperfections into the modeling strategy when shock absorption applications are aimed for.

Impact response and energy absorption of metallic buffer with entangled wire mesh damper

An innovative metallic buffer consisting of series-connected hat-shaped entangled wire mesh damper(EWMD)and parallel springs are proposed in this work to enhance the reliability of engineering equipment.The impact response and the energy dissipation mechanism of hat-shaped EWMD under different quasi-static compression deformations(2-7 mm)and impact heights(100-200 mm)are investigated using experimental and numerical methods.The results demonstrate distinct stages in the quasi-static mechanical characteristics of hat-shaped EWMD,including stiffness softening,negative stiffness,and stiffness hardening.The loss factor gradually increases with increasing compression deformation before entering the stiffness hardening stage.Under impact loads,the hat-shaped EWMD exhibits optimal impact energy absorption when it enters the negative stiffness stage(150 mm),resulting in the best impact isolation effect of metallic buffer.However,the impact energy absorption significantly decreases when hat-shaped EWMD enters the stiffness hardening stage.Interestingly,quasi-static compression analysis after experiencing different impact loads reveals the disappearance of the negative stiffness phenomenon.Moreover,with increasing impact loads,the stiffness hardening point progressively shifts to an earlier stage.

Compressive property and energy absorption characteristic of interconnected porous Mg-Zn-Y alloys with adjusting Y addition

In this study,interconnected porous Mg-2Zn-xY alloys with different phase compositions were prepared by various Y additions(x=0.4,3,and 6 wt.%)to adjust the compressive properties and energy absorption characteristics.Several characterization methods were then applied to identify the microstructure of the porous Mg-Zn-Y and describe the details of the second phase.Compressive tests were performed at room temperature(RT),200℃,and 300℃to study the impact of the Y addition and testing temperature on the compressive properties of the porous Mg-Zn-Y.The experimental results showed that a high Y content promotes a microstructure refinement and increases the volume fraction of the second phase.When the Y content increases,different Mg-Zn-Y ternary phases appear:I-phase(Mg_(3)Zn_(6)Y),W-phase(Mg_(3)Zn_(3)Y_(2)),and LPSO phase(Mg_(12)ZnY).When the Y content ranges between 0.4%and 6%,the compressive strength increases from 6.30MPa to 9.23 MPa,and the energy absorption capacity increases from 7.33 MJ/m^(3)to 10.97 MJ/m^(3)at RT,which is mainly attributed to the phase composition and volume fraction of the second phase.However,the average energy absorption efficiency is independent of the Y content.In addition,the compressive deformation behaviors of the porous Mg-Zn-Y are altered by the testing temperature.The compressive strength and energy absorption capacity of the porous Mg-Zn-Y decrease due to the softening effect of the high temperature on the struts.The deformation behaviors at different temperatures are finally observed to reflect the failure mechanisms of the struts.

Dynamic crushing behaviors and enhanced energy absorption of bio-inspired hierarchical honeycombs with different topologies

In order to pursue good crushing load uniformity and enchance energy absorption efficiency of conventional honeycombs, a kind of bio-inspired hierarchical honeycomb model is proposed by mimicking the arched crab shell structures. Three bio-inspired hierarchical honeycombs(BHHs) with different topologies are designed by replacing each vertex of square honeycombs with smaller arc-shaped structures. The effects of hierarchical topologies and multi-material layout on in-plane dynamic crushings and absorbed-energy capacities of the BHHs are explored based on the explicit finite element(FE) analysis.Different deformation modes can be observed from the BHHs, which mainly depend upon hierarchical topologies and impact velocities. According to energy efficiency method and one-dimensional(1D) shock theory, calculation formulas of densification strains and plateau stresses for the BHHs are derived to characterize the dynamic bearing capacity, which is consistent well with FE results. Compared with conventional honeycombs, the crushing load efficiency and energy absorption capacity of the BHHs can be improved by changing the proper hierarchical topology and multi-material layout. These researches will provide theoretical guidance for innovative design and dynamic response performance controllability of honeycombs.

Energy absorption characteristics of novel high-strength and hightoughness steels used for rock support

Nowadays,the development of novel metallic materials for rock support have attracted research interests since they can significantly improve the deformation and energy absorption capacities of rock bolts.Although previous studies proved the importance and mechanical advantages of utilizing high-strength and high-toughness(HSHT)steels in rock support,there is no systematic analysis to reveal the essential energy absorption parameter and the guidelines for further development of metallic rock support materials.This paper analyzes the energy absorption characteristics of novel HSHT steels(negative Poisson’s ratio(NPR)and twinning-induced plasticity(TWIP)steels)in comparison with conventional rock support materials.A physically based crystal plasticity(CP)model was set up and calibrated to study the effect of strain hardening rate(SHR).Meanwhile,the roles of underlying physical mechanisms,i.e.the dislocation density and twin volume fraction,were studied.The results show that the improvement of energy absorption density(EAD)is essential for further development of rock support materials,besides the increase of energy absorption rate(EAR)for previous development of conventional rock support materials.The increase of EAD requires increases of both strength and deformation capacity of materials.For HSHT steels,the decrease of SHR has a positive effect on the improvement of EAD.In addition,the increase of EAD is followed by the increase of twin volume fraction and the decrease of plastic Poisson’s ratio which can promote deformation plasticity of materials.Meanwhile,the increase of EAR is correlated with the accumulation of dislocation density,which can increase the strength of materials.This paper provides the theoretical basis and guidelines for developing rock support materials in deep underground engineering and other related fields.

Geometric Accuracy and Energy Absorption Characteristics of 3D Printed Continuous Ramie Fiber Reinforced Thin-Walled Composite Structures

The application of continuous natural fibers as reinforcement in composite thin-walled structures offers a feasible approach to achieve light weight and high strength while remaining environmentally friendly.In addition,additive manufacturing technology provides a favorable process foundation for its realization.In this study,the printability and energy absorption properties of 3D printed continuous fiber reinforced thin-walled structures with different configurations were investigated.The results suggested that a low printing speed and a proper layer thickness would mitigate the printing defects within the structures.The printing geometry accuracy of the structures could be further improved by rounding the sharp corners with appropriate radii.This study successfully fabricated structures with vari-ous configurations characterized by high geometric accuracy through printing parameters optimization and path smoothing.Moreover,the compressive property and energy absorption characteristics of the structures under quasi-static axial compression were evaluated and compared.It was found that all studied thin-walled structures exhibited progressive folding deformation patterns during compression.In particular,energy absorption process was achieved through the combined damage modes of plastic deformation,fiber pullout and delamination.Furthermore,the com-parison results showed that the hexagonal structure exhibited the best energy absorption performance.The study revealed the structure-mechanical property relationship of 3D printed continuous fiber reinforced composite thin-walled structures through the analysis of multiscale failure characteristics and load response,which is valuable for broadening their applications.

Mechanical Properties and Energy Absorption of Integrated AlSi10Mg Shell Structures with BCC Lattice Infill

Shell-infill structures comprise an exterior solid shell and an interior lattice infill,whose closed features yield superior comprehensive mechanical performance and light weight.Additive manufacturing(AM)can ensure the fabrica-tion of complex structures.Although the mechanical behaviors of lattice structures have been extensively studied,the corresponding mechanical performances of integrated-manufactured shell structures with lattice infills should be systematically investigated due to the coupling effect of the exterior shell and lattice infill.This study investigated the mechanical properties and energy absorption of AlSi10Mg shell structures with a body-centered cubic lattice infill fabricated by AM.Quasi-static compressive experiments and corresponding finite element analysis were conducted to investigate the mechanical behavior.In addition,two different finite element modeling methods were compared to determine the appropriate modeling strategy in terms of deformation behavior.A study of different parameters,including lattice diameters and shell thicknesses,was conducted to identify their effect on mechanical performance.The results demonstrate the mechanical advantages of shell-infill structures,in which the exterior shell strengthens the lattice infill by up to 2.3 times in terms of the effective Young’s modulus.Increasing the infill strut diameter can improve the specific energy absorption by up to 1.6 times.

A Footpad Structure with Reusable Energy Absorption Capability for Deep Space Exploration Lander:Design and Analysis

The footpad structure of a deep space exploration lander is a critical system that makes the initial contact with the ground,and thereby plays a crucial role in determining the stability and energy absorption characteristics during the impact process.The conventional footpad is typically designed with an aluminum honeycomb structure that dissipates energy through plastic deformation.Nevertheless,its effectiveness in providing cushioning and energy absorption becomes significantly compromised when the structure is crushed,rendering it unusable for reusable landers in the future.This study presents a methodology for designing and evaluating structural energy absorption systems incorporating recoverable strain constraints of shape memory alloys(SMA).The topological configuration of the energy absorbing structure is derived using an equivalent static load method(ESL),and three lightweight footpad designs featuring honeycomb-like Ni-Ti shape memory alloys structures and having variable stiffness skins are proposed.To verify the accuracy of the numerical modelling,a honeycomb-like structure subjected to compression load is modeled and then compared with experimental results.Moreover,the influence of the configurations and thickness distribution of the proposed structures on their energy absorption performance is comprehensively evaluated using finite element simulations.The results demonstrate that the proposed design approach effectively regulates the strain threshold to maintain the SMA within the constraint of maximum recoverable strain,resulting in a structural energy absorption capacity of 362 J/kg with a crushing force efficiency greater than 63%.

Optimization Design of an Embedded Multi-Cell Thin-Walled Energy Absorption Structures with Local Surface Nanocrystallization

Bymeans of the local surface nanocrystallization that enables to change the material on local positions,an innovative embedded multi-cell(EMC)thin-walled energy absorption structures with local surface nanocrystallization is proposed in this paper.The local surface nanacrystallization stripes are regarded as the moving morphable components in the domain for optimal design.Results reveal that after optimizing the local surface nanocrystallization layout,the specific energy absorption(SEA)is increased by 50.78%compared with the untreated counterpart.Besides,in contrast with the optimized 4-cell structure,the SEA of the nanocrystallized embedded 9-cell structure is further enhanced by 27.68%,in contrast with the 9-cell structure,the SEA of the nanocrystallized embedded clapboard type 9-cell structure is enhanced by 3.61%.Thismethod provides a guidance for the design of newenergy absorption devices.

Mechanical properties and energy absorption properties of aluminum foam-filled square tubes

Longitudinal and transverse mechanical properties and energy absorption properties of foam-filled square tubes under quasi-static loading conditions were studied.The foam-filled thin-walled square tube was fabricated with aluminum tube as its shell and closed-cell Al-Mg alloy foam as its core.The results indicated that the plateau region of the load-displacement curve exhibited a marked fluctuant serration which was clearly related to the formation of folds.The longitudinal deforming mode of foam-filled square tube was the same as that of the empty tube,but the fold number of foam-filled square tube was more than that of the empty tube.The longitudinal compression load and energy absorption value of foam-filled square tube were higher than the sum of that of aluminum foam (alone) and empty tube (alone) due to the interaction between tube and filler.In transverse direction,the compression load and energy absorption ability of foam-filled square tubes were significantly lower than those in longitudinal direction.

Lateral compression and energy absorption of foamed concrete-filled polyethylene circular pipe as yielding layer for high geo-stress soft rock tunnels

Foamed concrete as energy absorption material for high geo-stress soft rock tunnels has been proven to be feasible due to its high compressibility and lightweight.However,the lengthy curing and defoaming problems caused by the cast-in-place method of large-volume foamed concrete remain unsolved.In this study,we propose a novel energy absorber composed of foamed concrete-filled polyethylene(FC-PE)pipe and analyze its deformation and energy absorption capacity via quasi-static lateral compression experiments.Results show that FC-PE pipes exhibit typical three-stage deformation characteristics,comprising the elastic stage,the plastic plateau,and the densification stage.Furthermore,the plateau stress,energy absorption,and specific energy absorption of the specimens are 0.81–1.91 MPa,164–533 J,and 1.4–3.6 J/g,respectively.As the density of the foamed concrete increases,the plateau stress and energy absorption increase significantly.Conversely,the length of the plastic plateau and energy absorption efficiency decrease.Moreover,based on the vertical slice method,progressive compression of core material,and the 6 plastic hinges deformation mechanism of the pipe wall,a theoretical calculation method for effective energy absorption is established and achieves good agreement with experimental results,which is beneficial to the optimization of the composite structure.

Energy Absorption Diagrams of Multi-layer Corrugated Boards

Based on the static compression experiments, the compressive stress-strain curve of multi-layer corrugated boards is simplified into three sections of linear elasticity, sub-buckling going with local collapse and densification. By considering the structure factors of multi-layer corrugated boards, the energy absorption model is obtained and characterized by the structure factors of corrugated cell-wall. The model is standardized by the solid modulus and it is universal for corrugated structures of different basis material. In the liner-elastic section, with the increase of the load, the energy absorption per unit volume of multi-layer corrugated boards gradually increases; in the sub-buckling section going with local collapse, the compression resistance of multi-layer corrugated boards goes on under a nearly constant load, but the energy absorption per unit volume rapidly increases with the increase of the compression strain. It is shown as an ascending curve in the energy absorption diagram. In the densification section, the corrugated sandwich core has no energy absorption capability. A good consistency is achieved between theoretical and experimental energy absorption curves. In designing the cushioning package, the cushioning properties can be evaluated by the theoretical model without more experiments. The suggested method to develop the energy absorption diagram for corrugated boards can be used to characterize the cushioning properties and optimize the structures of corrugated sandwich structures.

Experimental and numerical assessment of energy absorption capacity of thin-walled Al 5083 tube produced by PTCAP process

The energy absorption capacity of the Al5083 thin-walled tube produced by parallel tubular angular pressing(PTCAP) process was evaluated. Also, microstructure, mechanical properties, and anisotropy coefficients were studied in the peripheral and axial directions. Results showed that values of energy absorption decreased with processing pass increasing and the values for the unprocessed, first and second passes were obtained to be 167, 161.4 and 160.7 J, respectively. The differences between the simulation results for the energy absorption values and their experimental values for the unprocessed, the first and the second PTCAP passes samples are about 5%, 10%, and 13%, respectively. The energy absorption capacity was related to the anisotropy coefficient and microstructure. The results demonstrated that grain refinement occurred and ultimate tensile strength(UTS) and microhardness after the first and second PTCAP passes were enhanced, while the increase rate in the first pass was much severer. Also, by applying PTCAP, the deformation modes were altered, such that the deformation mode of the annealed tube was quite symmetrical and circular while for the first and second passes there have been triple and double lobes diamond. The results of the numerical simulation for the deformation mode of the annealed and PTCAPed tubes were consistent with the experimental results. The deformation mode of tubes is dependent on their mechanical properties and variation of the mechanical properties during PTCAP process.

Efficient energy absorption of functionally-graded metallic foam-filled tubes under impact loading

The deformation behavior and crashworthiness of functionally-graded foam-filled tubes(FGFTs)under drop-weight impact loading were investigated.Closed cell aluminum,A356 alloy and zinc foams fabricated by the liquid state processing were used as axial grading fillers for the manufacture of single-layer and multilayer structures with different configurations.The results indicate that the deformation of multilayer foam filled tubes initiates from the low-strength components,and then propagates in the high-strength components through the gradual increment of stress.The use of more A356 alloy and aluminum foam layers provides greater specific energy absorption(SEA)for the graded structures,whereas the high-strength zinc foam has no positive effect on the crash performance.The progressive collapse of graded structures consisting of the aluminum and A356 alloy foams occurs in a symmetric mode under quasi-static and drop-weight impact conditions.However,the zinc foam causes a combination of symmetric and extension modes as well as greater localized deformation under dynamic loading and greater local rupture in quasi-static loading condition.The Al−A356 foam-filled tubes with a combination of the highest SEA(10 J/g)and the lowest initial peak stress(σmax of 10.2 MPa)are considered as the best lightweight crashworthy structures.

Compressive and energy absorption properties of closed-cell magnesium foams

The quasi-static compressive mechanical behavior and deformation mechanism of closed-cell magnesium foams were studied, and the ef- fects of the density of magnesium foams on the compressive and energy absorption properties were also discussed. The results show that the compressive process of closed-cell magnesium foams is characterized by three deformation stages： linear elastic stage, collapsing stage and densification stage. At the linear elastic stage, the peak compressive strength （t70） and Young＇s modulus （E0） increase as the density increases Magnesium foams can absorb energy at the collapsing stage. In a certain strain range, the energy absorption capacity also increases as the density of magnesium foams increases.

A new hybrid energy absorption mechanism subjected to axial loading

This study aims to introduce a novel hybrid design with a combination of two more common mechanisms for improving the capacity of systems in absorbing the kinetic energy of moving vehicles or devices. This new model consists of two individual mechanisms, i.e., expansion of a circular tube accompanied by crushing of an inner tube, which dissipate the energy through friction, plastic deformations and failures of inner tube. This study comprises 24 case studies surveyed under two different design controls, constant mass and constant volume, for comparing purposes. Finite element simulations are utilized so as to investigate models’ deformations and to extract some crashworthiness parameters in aid of representing the efficiency of the mechanism as well as conducting a parametric study between three different profiles of inner tube. This study shows that models with inner circular and hexagonal tube profile absorb higher amount of energy due to experiencing three different modes of energy dissipation systems, including folding, shear and ductile damages.

Deformation mode and energy absorption of polycrystal-inspired square-cell lattice structures

Lattice structures are widely used in many engineering fields due to their excellent mechanical properties such as high specific strength and high specific energy absorption(SEA)capacity.In this paper,square-cell lattice structures with different lattice orientations are investigated in terms of the deformation modes and the energy absorption(EA)performance.Finite element(FE)simulations of in-plane compression are carried out,and the theoretical models from the energy balance principle are developed for calculating the EA of these lattice structures.Satisfactory agreement is achieved between the FE simulation results and the theoretical results.It indicates that the 30◦oriented lattice has the largest EA capacity.Furthermore,inspired by the polycrystal microstructure of metals,novel structures of bi-crystal lattices and quad-crystal lattices are developed through combining multiple singly oriented lattices together.The results of FE simulations of compression indicate that the EA performances of symmetric lattice bi-crystals and quad-crystals are better than those of the identical lattice polycrystal counterparts.This work confirms the feasibility of designing superior energy absorbers with architected meso-structures from the inspiration of metallurgical concepts and microstructures.

Influence of Density on Compressive Properties and Energy Absorption of Foamed Aluminum Alloy

The foamed aluminum alloys with different densities were fabricated by melt foaming technique. The compressive properties and energy absorption of the foamed aluminum alloy with different densities were analyzed. The results reveal that the compressive stress-strain curves follow the typical behavior of cellu- lar foams with three deformation stages. Under the same strain, the energy absorption capability decreases with the decrease of density. However, with increasing the strain, the energy absorption efficiency of foamed metal increases initially and then decreases. The lower the density, the longer the plateau region, within the range of high strain, the energy absorption efficiency is always high.