Plastic Energy Absorption Research Articles

Plastic deformation behavior and energy absorption performance of a composite metamaterial based on asymmetric auxetic lattices

This study focuses on the design, behavior and experimental analysis of a novel metamaterial, consisting of an asymmetric auxetic three-dimensional structure (AATS) infused with polyester resin. Utilizing FDM additive printing, samples were created with customizable responses to compressive loads through varied design parameters. The objective is to surpass traditional material blending by enhancing stiffness and energy absorption. Striking a delicate balance, the AATS energy absorption properties are preserved while leveraging the stiffness of the resin. Despite its compact cubic form, not exceeding 27 mm on each side, this metamaterial showcases amplified characteristics, blending the AATS and polyester resin. The results hint at promising applications across military defense, automotive, aerospace sectors, and even potential replacements for articulated human skeletal components.

Influence of Interface Type on Dynamic Deformation Behavior of 3D-Printed Heterogeneous Titanium Alloy Materials.

Using the Split Hopkinson Pressure Bar technique, strain-limited dynamic compressive loading experiments were performed on TA1/TA15 heterostructure (HS) materials. The plastic deformation mechanisms, fracture forms, and energy absorption properties of an HS material with a metallurgical bonding interface (MB) and an HS material without a metallurgical bonding interface (NMB) are compared and analyzed. The results show that there is no significant difference between the two deformation mechanisms. The fracture forms are all "V-shaped" fractures within the TA1 part. The NMB was carried for 57 μs before failure and absorbed 441 J/cm3 of energy. The MB was carried for 72 μs before failure and absorbed 495 J/cm3 of energy. Microstructure observations show that there is a coordinated deformation effect near the MB interface compared to the NMB, with both TA1 and TA15 near the interface carrying stresses. This causes an enhancement of the MB load-bearing time and a 12% increase in energy absorption.

Repeated impact response of honeycomb sandwich panels based on the failure parameters of adhesive layer and material

Honeycomb sandwich structure has been widely used in lightweight and impact protection of rail vehicle structures due to its excellent mechanical properties. In this paper, the plastic deformation, failure response and energy absorption characteristics of honeycomb sandwich panels for rail vehicles under repeated impact loads were studied. The three-point bending tests and low-speed impact tests of honeycomb sandwich panels were carried out, and a three-dimensional numerical model considering the detailed structure of the honeycomb core and the failure of the adhesive layer was established. The model can reasonably simulate honeycomb sandwich panels’ stiffness, strength, and structural failure. The effects of impact times and impact angle on the performance indexes of the honeycomb sandwich panel were studied. The results show that when the impact energy is the same, the impact times will affect the energy absorption distribution of honeycomb sandwich panels. With the increase in impact times, the panel’s absorption energy decreases, the core’s absorption energy increases, and the total absorption energy decreases. For multiple impact conditions, with the increase of impact times, the single energy absorption of the upper panel and core decreases, and the single energy absorption of the lower panel increases. When the impact energy is the same, the rise in impact angle will increase the damage to the honeycomb sandwich panel, and the energy absorption of each part will increase. In addition, the influence of impact times on the energy absorption efficiency of honeycomb sandwich panels is related to the impact angle.

Study on the deformation mode and energy absorption characteristics of a corner-enhanced biomimetic spider web hierarchical structure

To improve the energy absorption properties of honeycomb structures based on the underlying mechanism of uniform stress dispersion and to effectively increase the strength of a spiderweb, a corner-enhanced spiderweb hierarchical honeycomb structure was proposed herein. This study involved a quasistatic compression test and simulation of a corner-enhanced spiderweb hierarchical structure complemented by 3D printing. The deformation pattern of the common spiderweb honeycomb (CSH) was //-shaped. However, the deformation pattern of the honeycomb after corner enhancement tended to be monolithic, forming an X shape. The deformation characteristics of both the CSH and the first-order local cellular elements were analyzed. The corner-enhanced honeycomb cellular elements dispersed the load onto the inner wall to achieve a common load-bearing effect. Further numerical simulation analysis was carried out in conjunction with the experiments, and local destruction analysis was performed for single-cell elements. Corner enhancement could increase the plastic hinge energy absorption of the structure, with a first-order corner-enhanced spiderweb honeycomb (CESH-F) exhibiting a 46.3 % improvement in specific energy absorption compared to that of a conventional CSH. The layers were reinforced to compress the load uniformly, and a third-order corner-enhanced spiderweb honeycomb (CESH-T) had a 25.7 % improvement in specific energy absorption compared to that of the CESH-F. In addition, optimization was performed for corner-enhanced spiderweb honeycomb (CESH) according to different helix radii. The effect of the radial line thickness on honeycomb-specific energy absorption was explored, and the radial line thickness was positively proportional to honeycomb-specific energy absorption. These findings offered valuable insights into the design of lightweight and high-energy-absorbing biomimetic structures.

Numerical Analysis on the Dynamic Response of PVC Foam/Polyurea Composite Sandwich Panels under the Close Air Blast Loading.

This paper explores a novel structure aimed at enhancing its blast resistance performance by adding a layer of polyurea coating to the steel-PVC foam-steel sandwich panel. The response of 13 different arrangements of sandwich panels under explosive loading was studied using numerical simulation. The response process can be divided into three deformation stages: (1) Fluid-structure interaction; (2) Compression of the sandwich panel; (3) Dynamic structural response. The dynamic responses of the various sandwich panels to close-range air blast loading were analyzed based on the deformation characteristics, deflection, effective plastic strain, energy absorption, and pressure of the shock wave. The study draws the following conclusions: Reasonably adding a layer of polyurea to the traditional PVC foam sandwich panel can enhance its resistance to shock wave absorption, with a maximum increase of 29.8%; the optimal arrangement for explosion resistance is steel plate-PVC foam-polyurea-steel plate when the polyurea is coated on the back; and the best quality ratio between polyurea and PVC foam is 1:7 when the polyurea is coated on the front.

Dynamic properties of micro-NPR material and its controlling effect on surrounding rock mass with impact disturbances

A novel meta steel with negative Poisson’s ratio effect (termed as micro-NPR steel) is developed for rock support in deep underground engineering. It possesses high strength, high ductility, and high energy absorption characteristics. In this paper, static tension and modified dynamic drop hammer tests are performed on this novel material to investigate its mechanical properties first. Then based on this material, a new generation of micro-NPR anchor cable is developed and applied in field tests subjected to blasting dynamic loads. The results of laboratory tests reveal that the ultimate elongation of micro-NPR steel under dynamic impacts is more than 30% and it is over 1.5 times that of Q235; the plastic and total energy absorption of micro-NPR are both significantly higher than that of Q235. Field test indicates the fine controlling effect of micro-NPR anchor cable on surrounding rock mass under dynamic loads. Axial force confirms that micro-NPR cables can distribute and absorb the dynamic energy uniformly around the supported rock when subjected to dynamic disturbance, avoiding local failure induced by excessive stress concentration. The excavation compensation principle and energy-absorbing characteristics are used to explain the support mechanisms. Thus, micro-NPR material and anchor cable can control and prevent dynamic disasters in deep underground engineering effectively.

The heterogeneous microstructure of laser welded joint and its effect on mechanical properties for dissimilar 9Cr steel and alloy 617

The Fe-rich heterogeneous microstructures were observed in the weld metal (WM) of laser welding on dissimilar metals between 9Cr steel and alloy 617, manifesting as vortex-like and lamellar-like structures. They displayed a face-centered cubic structure and consisted of cellular and columnar dendrites. The vortex-like structure was distributed on the upper side of the WM and exhibited the solidification grain boundary. Due to the higher liquid temperature and insufficient mixing, the vortex-like structure exhibited preferential nucleation during the solidification process. On the other hand, the lamellar-like structure was situated on the lower side of the WM and had a thickness of 50 μm. The lamellar-like structure and WM solidified simultaneously with the rapid solidification rate, resulting in noticeable intergranular chemical segregation. During the tensile test, deformation twins formed in the heterogeneous microstructure, due to the lower stacking fault energy and fine particles. Numerous deformation twins played a crucial role in inhibiting crack initiation, which performed the same orientation. Furthermore, the heterogeneous microstructure generated 89.8% of twin boundaries during the crack propagation, while the WM had 30.4%. This phenomenon facilitated plastic energy absorption and deflected the crack propagation path. Thus, the heterogeneous microstructures contributed to the enhancement of mechanical toughness at room temperature.

Residual compressive strength of polyamide fiber‐reinforced epoxy composites after low‐velocity impact

AbstractIn this study, polyamide fibers, which stand out with their excellent plastic deformation and energy absorption capacity, were used as reinforcement materials, and in‐house manufactured composite specimens were subjected to low‐velocity impact (LVI), compression after impact (CAI) and tensile tests. Within this scope, one and two repeated drop tests were performed under 3 m/s velocity to determine LVI responses and how impact number affects the dynamic properties. CAI tests were also performed at a 1 mm/min crosshead speed, and mechanical properties for non‐impacted, one‐impacted, and two‐impacted specimens were determined. As a result of the outstanding plastic deformation capacity of thermoplastic fabrics, it is concluded that polyamide composites exhibited quite large strains. Furthermore, it was understood from the tensile responses that tensile stresses were carried by the thermoplastic fibers in two different regimes and significantly high toughness was obtained. Moreover, reductions in the maximum compression loads, critical buckling loads and axial stiffness were observed due to degradation in structural integrity after impact loads. Additionally, the utilization of recyclable thermoplastic polyamide fibers as reinforcement material instead of conventional reinforcement materials such as carbon and glass fibers provide more environmentally friendly products.

Additively-manufactured 3D truss-lattice materials for enhanced mechanical performance and tunable anisotropy: Simulations & experiments

Truss-lattices have wide application prospects in various important fields owing to their superior mechanical properties and energy absorption characteristics. In this paper, two typical truss-lattice materials (i.e. bending-dominated body-centred cubic (BCC) and stretch-dominated Octet architectures) were designed with enhanced mechanical properties and tunable anisotropy. The elastoplastic properties and large strain response were both investigated numerically and experimentally. Numerical results showed that a relative larger stiffness characteristic could be harvested when the shape parameter was chosen between 0.2 and 0.3, and the anisotropy degree could also be controlled through the shape parameter. Large strain multi-cell simulations also demonstrated the enhanced plastic properties and energy absorption characteristics of the designed architectures. The numerical findings were then confirmed through the uniaxial compression experiments on the 316L stainless steel truss-lattices specimens fabricated by the Selective Laser Melting (SLM) process. This study would broaden the design idea for the 3D truss-lattices with enhanced mechanical performance and tunable anisotropy, which may of great potential in engineering applications.

Crashworthiness Analysis of Square Aluminum Tubes Subjected to Oblique Impact: Experimental and Numerical Study on the Initial Contact Effect

This study investigates the crashworthiness behavior of square aluminum thin-walled tubes subjected to both axial and oblique impact loading, emphasizing the effects of crushing angle and initial contact between impactor and tube on the plastic collapse initiation and energy absorption capacity. A parametric study in crushing angle is conducted until 15°, while the two examined types of initial contact between impactor and tube consist of a contact-in-edge case and a contact-in-corner one, aiming to capture the effect of initial contact on both plastic collapse and energy absorption. Both experimental quasi-static tests and numerical simulation via finite element modeling in LS-DYNA software are carried out for the evaluation of the crushing response of the tested tubes. The 5° oblique cornered crushing revealed the greatest energy absorption, reflecting the most efficient loading case as significant tearing failure occurred around the tube corners in axial crushing due to a higher peak crushing force, while the increase in crushing angle caused a drop in energy absorption and peak force regarding the oblique loading. Finally, an initial contact-in-corner case revealed higher energy absorption compared to both axial and edged oblique loading, while peak force showed a slight decrease with crushing angle in that case.

Study on off-center impact behavior and damage characterization of carbon fiber reinforced aluminum laminate

This paper aims to explore the off-center low-velocity impact response and damage characteristics of carbon fiber reinforced aluminum laminate (CARALL). Progressive damage finite element models of CARALL considering the stiffness degradation and damage evolution of carbon fiber reinforced plastic (CFRP) were established using a user subroutine and verified by off-center impact tests with different impact energies. The motion propagation, damage, and spatial distribution of dynamic responses of CARALL impacted in different locations are studied. The results indicate that increase in impact distance from center dissipates more energy due to the more severe damage and failure of CFRP, while the off-center impact have a negative effect on the plastic energy absorption of metal compared with center impact. A quantitative expression is proposed to describe the spatial distribution of the maximum transverse displacement.

Crystal sheet lattices: Novel mechanical metamaterials with smooth profiles, reduced anisotropy, and enhanced mechanical performances

Cellular materials with smooth profiles, improved structural strength, and reduced elastic-anisotropy are eternal pursuit in bone-implant filed. However, it is a huge task to meet so many requirements. In this work, a novel class of mechanical metamaterials, named as crystal sheet lattices, were proposed. The elastic performances were investigated using representative elementary volume model and examined by quasi-static compression tests. The plastic performances and energy absorption behaviors were experimentally calibrated. Meanwhile, elastoplastic simulations were adopted to study the deformation mode on the structural strengthen mechanism. The results demonstrate that the reduced elastic-anisotropy can be achieved without complicated regulation process. Under the same material volume fraction, the stiffness, yield strength, and energy absorption capability were respectively increased about 30%–60%, 30%–150%, and 70%–280%, for most of crystal sheet lattices in comparison with their truss-based counterparts. Being open type cellular materials, the crystal sheet lattices are of high mass-specific mechanical performances. Due to the smooth profiles, large surface volume ratios, and enhanced mechanical performances, CSLs also have potentials to be utilized in lightweight and heat transportation fields.

Numerical Investigation of Different Core Topologies in Sandwich-Structured Composites Subjected to Air-Blast Impact

Air-blast loading is a serious threat to military and civil vehicles, buildings, containers, and cargo. Applications of sandwich-structured composites have attracted increasing interest in modern lightweight design and in the construction of dynamic loading regimes due to their high resistance against blast and ballistic impacts. The functional properties of such composites are determined by the interplay of their face sheet material and the employed core topology. The core topology is the most important parameter affecting the structural behavior of sandwich composites. Therefore, this contribution presents a thorough numerical investigation of different core topologies in sandwich-structured composites subjected to blast loading. Special emphasis is put on prismatic and lattice core topologies displaying auxetic and classical non-auxetic deformation characteristics in order to illustrate the beneficial properties of auxetic core topologies. Their dynamic responses, elastic and plastic deformations, failure mechanisms, and energy absorption capabilities are numerically analyzed and compared. The numerical studies are performed by means of the commercial finite element code ABAQUS/Explicit, including a model for structural failure.

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.

Improved mechanical strength of the C/C-Mo joint by introducing polydopamine modified Ni foam to the interlayer

For the dissimilar C/C-Mo joints, the high residual thermal stress in the joint generally leads to the low shear strength of the joint, especially when the joints are employed under the quick alternating temperature change conditions. To address this issue, three-dimensional polydopamine modified Ni foam was introduced to the C/C-Mo joints. The modification of Ni foam would avoid its complete dissolution and retain its framework after braze welding via a facile polydopamine carbonization strategy. As polydopamine modified Ni foam was introduced to the interlayer, the joint strength increased by 63%, up to 63.77 MPa. The introduction of the modified Ni foam is beneficial to improve the plastic deformation ability of the main phases in the joint, leading to the decrease of the brittleness of the braze seam. Furthermore, the residual Ni frameworks are facilitated to take full advantage of the good plastic deformation capability and energy absorption ability of the foam structure, resulting in the improved joint strength at room temperature and a high strength retention of 92.07% after 10 thermal cycles between room temperature and 1100 °C.

Lateral crushing and energy absorption behavior of hexagonal tubes with non-uniform thickness distributions

To improve the energy absorption performance of hexagonal thin-walled energy absorbers, a space- and weight-efficient design method is proposed by rationally arranging the distribution of the thickness along walls. The plastic deformation characteristics and energy absorption behavior of the designed non-uniform hexagonal tubes subjected to lateral compression by two rigid plates are investigated. By properly adding the thickness at the regions near side corners, the plateau forces of the designed non-uniform hexagonal tubes are higher than that of the uniform hexagonal tube. Increasing the thickness of the horizontal walls can regulate the deformation mechanism of the hexagonal tubes and thus increase the effective stroke, which means that the lateral space is apt to be fully utilized. By simultaneously increasing the thicknesses at these regions, the stroke efficiency is significantly improved and the total energy absorptions of the non-uniform tubes can be 2.0–2.3 times that of the uniform hexagonal tube. In addition, compared with the corresponding uniform hexagonal tubes with the same weight, the rationally designed non-uniform hexagonal tubes can possess dramatic improvement in comprehensive energy absorption performance: the total energy absorption, stroke efficiency, and energy absorption efficiency can be improved by nearly 40%, 22%, and 30%, respectively.

Cyclic behavior of shear-type hysteretic dampers with different cross-sectional shapes

Metallic shear-type dampers are widely used as seismic-energy-absorbing devices because they are easy to produce, install, and maintain. This study investigated a metallic shear-type damper constructed with a circular hollow section; an H-shaped section damper, which is commonly used as a metallic shear damper, was included in the study for comparison. A structural equation for calculating the strength and initial stiffness is provided based on the plastic collapse mechanism of the two types of dampers. For both types, a cyclic loading test was conducted to investigate their mechanical characteristics as hysteretic dampers. Damper specimens with each of the two cross-sectional shapes were fabricated using low-yield-point steel and were designed to have nearly the same full plastic shear strength, initial stiffness, and weight. The experimental results confirm that both types of damper exhibit stable spindle-shaped hysteresis characteristics and have sufficient plastic deformation capacity and energy absorption capacity. Consequently, under identical loading conditions, the two types of damper have nearly the same strength increase ratio and deformation capacity. The local plastic strain was evaluated using a finite element analysis of monotonic loading; the results verify the validity of the proposed plastic collapse mechanism of the circular hollow section damper and H-shaped shear panel damper. The sharing of energy dissipation among the damper components was also analyzed.

Numerical evaluation of the impact performance of precast concrete segmental columns and strengthening techniques

This paper numerically examines the influence of impact locations and the effectiveness of two strengthening techniques, i.e. energy dissipating (ED) bars and carbon fiber reinforced plastic (CFRP) wrapping at joints, on improving the performance of precast concrete segmental columns (PCSC) under lateral impacts. Mild steel and shape memory alloy (SMA) are used as ED bars. The numerical models are validated by test results available in literature. Different impact velocities and impact locations are considered in the parametric analysis. The impact performance of PCSC with different strengthening techniques is evaluated in terms of the effective plastic strain, deformation, and energy absorption. SMA ED bars are found more effective to reduce the residual displacement due to its super-elastic characteristic while the mild steel ED bars have better energy absorption ability. The response of PCSC is impact location dependent. When joint is impacted, segmental rotation is more pronounced, adding ED bars and CFRP wrapping at joints might not be effective to improve the column performance due to severe shear deformation of the segments. When a segment is impacted, the translational slippage of the segment is the primary response mode, the considered strengthening approaches can effectively reduce the slippage between adjacent segments of PCSC. Moreover, it is found that the deformation response of PCSC can be reduced by increasing the prestress force level, especially when CFRP wrapping is applied at segment joints. CFRP wrapping at joints is found outperforming ED bars on improving the impact resistance of PCSC.

Effect of ball powder ratio on microstructure and compressive behaviour of porous Ti-4wt %Al alloy

Ti and Al powders were milled in the weight proportion 24:1 using horizontal planetary ball mill. The ratio of ball to powder amounts (BPR) was varied (10, 15, and 20) in the milling process. Powder mixture milled with different BPRs were characterized by the XRD and FESEM to probe the evolution of phase and particles shape and size. Further, these mixtures were used to make porous cylindrical samples through space holder method. The used space holder amount was 60 v%. Compression test of the samples were performed on Universal Testing Machine. It was analysed that crystallite size, shape and size of the powder particles considerably affected by the used ball to powder ratio.XRD confirms that phase formation is invariant with the BPR. The observed relative density is about 10% higher than the used space holder content. Porous sample synthesized by the powder milled with 15 BPR has higher plastic collapse stress and energy absorption capacity as compared to the samples made of the powder milled with 10 and 20 BPRs.

A study on ballistic performance of origami sandwich panels

Sandwich structures with origami cores have shown great potential for engineering applications. However, few studies have been performed on the ballistic performance of origami sandwich panels, particularly on their plastic deformation and ballistic resistance. In this study, rectangular metallic sandwich panels with aluminium origami cores were manufactured. Quasi-static indentation and ballistic impact tests were conducted to explore their ballistic performance. Three different shapes of indenters were considered: flat-ended, hemispherical-nosed and conical-nosed. Plastic deformation and energy absorption capacities were observed and analysed. Subsequently, finite element (FE) simulations using Ansys/Ls-dyna were executed to compare the ballistic performance of sandwich panels with origami cores and honeycomb cores. Parametric studies were also conducted to examine the effect of wall thickness, cell edge length and cell number of origami cores on the ballistic performance of origami sandwich panels.