Deformation Energy Research Articles

Rotating coupling of chiral identical twins in multimodal Kresling metamaterials for achieving ultra-high energy absorption

Origami structures have been widely applied for various engineering applications due to their extraordinary mechanical properties. However, the relationship between in-plane rotating coupling and energy absorption of these Origami structures is seldom studied previously. The study proposes a design strategy that utilizes identical-twin rotation (i.e. simultaneous rotation with the same chirality) and fraternal-twin rotation (i.e. simultaneous rotation with the opposite chirality) of Kresling metamaterials to achieve multimodal rotation coupling and enhanced energy absorption. Deformation mode and energy absorption properties of 3D-printed Kresling metamaterials have been studied using both quasi-static compression tests and finite element analysis. Furthermore, effects of polygon units and their connections to 2D and 3D arrangements, which generate 4 × 4 arrays and 2 × 2 × 2 arrays, have been investigated to identify the optimized structures for achieving ultra-high energy absorption of chiral Kresling metamaterials. Results showed that rotating coupling of chiral identical twins in multimodal Kresling metamaterials possesses diverse deformation patterns and ultra-high energy absorption. This study provides a novel strategy to optimize structural designs and mechanical properties of the Kresling metamaterials.

Experimental Study on Mechanical Properties and Permeability Characteristics of Calcareous Mudstone under Different Confining Pressures.

Calcareous mudstone, a type of red-bed soft rock, is prevalent in the surrounding rock of the Central Yunnan Water Diversion Project (CYWDP) in Yunnan Province, China, significantly impacting both construction and operation. The mechanical properties of calcareous mudstone vary with depth. This study investigates its mechanical properties, permeability characteristics, energy evolution, and macro- and micro-failure characteristics during deformation using triaxial compression tests under different confining pressures. Results reveal distinct stage characteristics in the stress-strain behavior, permeability, and energy evolution of calcareous mudstone. Crack propagation, permeability evolution, and energy dissipation are closely linked, elucidating the deformation and failure process, with fluid pressure playing a crucial role. The confining pressure σ3 increased from 2 MPa to 4 MPa and 6 MPa, while the peak stress σc (Pw = 1 MPa) of the calcareous mudstone increased by 84.49% and 24.89%, respectively. Conversely, the permeability at σc decreased from 11.25 × 10-17 m2 to 8.99 × 10-17 m2 and 5.72 × 10-17 m2, while the dissipative energy at σc increased from 12.39 kJ/m3 to 21.14 kJ/m3 and 42.51 kJ/m3. In comparison to those without fluid pressure (Pw = 0), the value of σc at Pw = 1 MPa was reduced by 36.61%, 23.23%, and 20.67% when σ3 was 2, 4, and 6 MPa, respectively. Increasing confining pressure augments characteristic stresses, deformation and failure energy, and ductility, while reducing permeability, crack propagation, and width. These findings enhance our understanding of calcareous mudstone properties at varying depths in tunnel construction scenarios.

Understanding the Impact of Group 14 Elements on the Reactivity of [1 + 2] Cycloaddition Reaction between a Cyclic (Alkyl)(amino)carbene Analogue with a Group 14 Element and a Heavy Acetylene Molecule.

Computational exploration using the density functional theory framework (M06-2X-D3/def2-TZVP) was undertaken to investigate the [1 + 2] cycloaddition reaction between a five-membered-ring heterocyclic carbene analogue (G14-Rea; G14 = group 14 element) and a heavy acetylene molecule (G14G14-Rea). It was theoretically observed that exclusively Si-Rea, Ge-Rea, and Sn-Rea demonstrate the capacity to participate in the [1 + 2] cycloaddition reaction with the triply bonded SiSi-Rea. In addition, only three heavy acetylenes (SiSi-Rea, GeGe-Rea, and SnSn-Rea) can catalyze the [1 + 2] cycloaddition reaction with Si-Rea. Our theoretical findings elucidated that the reactivity trend observed in these [1 + 2] cycloaddition reactions primarily arise from the deformation energies of the distorted G14G14-Rea. Also, our study reveals that the bonding characteristics of their respective transition states are controlled by the singlet-singlet interaction (donor-acceptor interaction), rather than the triplet-triplet interaction (electron-sharing interaction). Additionally, our work demonstrates that the bonding behavior between G14-Rea and G14G14-Rea is predominantly determined by the filled p-π orbital of G14G14-Rea (HOMO) → the empty perpendicular p-π orbital of G14-Rea (LUMO), rather than the vacant p-π* orbital of G14G14-Rea (LUMO) ← the filled sp2 orbital of G14-Rea (HOMO).

The response mechanism and testing method of the rock elastic modulus while drilling

The elastic modulus is a basic parameter reflecting the deformation resistance and energy concentration characteristics of rock. The traditional testing method of the rock elastic modulus needs to core the surrounding rock and testing it in the laboratory, which has difficulty reflecting the rock mechanical properties under the engineering site environment, and uncontrolled broken surrounding rock is difficult to core for testing. Digital drilling technology provides a new idea for in situ testing of the rock’s elastic modulus. The key is to establish a quantitative relationship between the elastic modulus and drilling data. In this paper, the relationship between rock cutting energy density and drilling data is established, and a series of rock digital drilling tests are carried out. The response law of the drilling data and cutting energy density to the rock elastic modulus is clarified. The inversion model of the rock elastic modulus while drilling (DP-E model) is established. The verification test results indicate that the average difference rate of the test results based on the DP-E model is 7.06% compared with the compression test method, which verifies the effectiveness of the model. This study provides a theoretical basis for in situ testing of the rock elastic modulus.

Crack propagation characteristics of coal body around the borehole under different loading rates

The loading rate is a crucial factor influencing the deformation and fracture of the coal body around a borehole. The uniaxial compression tests and digital image correlation methods were adopted to scrutinize the mechanical parameters, failure modes, and lateral strains of specimens. A comprehensive analysis of crack propagation characteristics under different loading rates was conducted. Based on the cohesion model, the intrinsic interplay between crack propagation characteristics and loading rates was elucidated. Combined with the actual situation on site, the treatment method of gas anomaly in high recovery rate working face is given. With an increase in loading rate, the peak strength, peak strain, and the initial stress level of cracks gradually increased and tended to stabilize. The elastic modulus exhibited an initial increase followed by a decrease. The failure mode transitioned from shear to tensile, and the fracture process became more intense. Tensile crack propagation was divided into four stages, with the first three stages characterized by “closed-open-closed” patterns. In the fourth stage, lateral strains fluctuated between positive and negative values at high loading rates, exhibiting high-strength nonlinearity, the accumulation of deformation energy density is “rupture → rupture again”. Due to the influence of cohesion, tensile crack propagation at low loading rates was hindered, resulting in K1 = 0 at the tensile crack tip. Under high loading rates, K1 > 0, leading to extensive tensile failure in the internal load-bearing structure. At the same time, combined with the abnormal situation of gas in the working face with high mining rate, specific solutions are put forward.

Impacts and depositional behaviors of debris flows on natural boulder-negative Poisson's ratio anchor cable baffles

The impacts of natural boulders carried by debris flows pose serious risks to the safety and reliability of structures and buildings. Natural boulders can be highly random and unpredictable. Consequently, boulder control during debris flows is crucial but difficult. Herein, an eco-friendly control system featuring anchoring natural boulders (NBs) with (negative Poisson's ratio) NPR anchor cables is proposed to form an NB-NPR baffle. A series of flume experiments are conducted to verify the effect of NB-NPR baffles on controlling debris flow impact. The deployment of NB-NPR baffles substantially influences the kinematic behavior of a debris flow, primarily in the form of changes in the depositional properties and impact intensities. The results show that the NB-NPR baffle matrix successfully controls boulder mobility and exhibits positive feedback on solid particle deposition. The NB-NPR baffle group exhibits a reduction in peak impact force ranging from 29% to 79% compared to that of the control group in the basic experiment. The NPR anchor cables play a significant role in the NB-NPR baffle by demonstrating particular characteristics, including consistent resistance, large deformation, and substantial energy absorption. The NB-NPR baffle innovatively utilizes the natural boulders in a debris flow gully by converting destructive boulders into constructive boulders. Overall, this research serves as a basis for future field experiments and applications.

Energy absorption behaviour and shape change effects of 3D printed polyurethane hexagonal honeycombs

Honeycombs have been used in a wide range of repeatable energy-absorbing elements due to their light weight and high energy absorption capacity. In the engineering environment, honeycombs will produce a shape change effect and rebound under multiple loading and unloading, so it is of great importance to investigate the energy-absorbing properties of honeycombs under the shape change effect for the application of honeycombs. In this study, the deformation process and energy absorption properties of 3D printed honeycombs under multiple loading were obtained through multiple quasi-static compression tests. On this basis, the coupling between shape change effects and honeycomb energy absorption is revealed. It is shown that the number of compressions does not affect the four-stage force-displacement curve characteristics of the honeycombs, but only the energy absorption efficiency of the honeycombs. There is an inverse relationship between the resilience of honeycombs and the energy absorption capacity of honeycombs, and the change of honeycomb stiffness under repeated compression is the direct cause of this relationship. The research results provide a reference for the application of honeycombs in the field of repetitive energy absorption.

Superstrengthening effect of beyond-solid-solution laser powder bed fused WE43 magnesium alloy triggered by direct aging treatment

Laser powder bed fusion (LPBF) technology exhibits the potential to develop magnesium alloys as lightweight, load-bearing components in critical industries such as aerospace and automotive. This study investigated the effects of various direct aging treatments on the microstructural evolution and mechanical properties of the beyond-solid-solution WE43 magnesium alloy fabricated via LPBF. The results show that the limited kinetic conditions provided by aging at 175°C lead to the decomposition of the beyond-solid-solution to form the β' metastable phase. The original β1 phase transformed to β' and β'' along the direction of least resistance. These nanoscale coherent phases increased the stored deformation energy, acting as nucleation sites for dynamic recrystallization and stimulating the formation of low-angle grain boundaries. This contributed to segmenting grains into multiple zones and subcrystals. Therefore, after aging at 175°C for 64 h, the grain size decreased from 3.39 to 1.96 μm. Meanwhile, the ultimate tensile strength (UTS) increased from 313 to 353 MPa, yield strength (YS) from 236 to 297 MPa, and elongation (EL) from 7.6 % to 12.4 %. Additionally, the aging treatment at 175°C for 128 h shifted the dominant strengthening mechanism from grain boundary strengthening to Orowan strengthening. As a result, the strengths of the alloy aged at 175°C/128 h exceeded the as-built alloy by 53 and 80 MPa for UTS and YS, respectively.

Study on dynamics of thin shell elements of composite materials based on absolute nodal coordinate formulation

Most solar panels use composite materials to suit the development objectives of large-scale and lightweight spaceship components, resulting in complex nonlinear dynamic characteristics. When describing the dynamic characteristics of thin shell elements in composite materials, the standard 48-DOF fully parameterized thick plate element based on absolute nodal coordinate formulation cannot accurately account for the coupling between the large range of motion and large deformation of thin shell elements, exposing issues such as shear locking, slow convergence, and low computational efficiency. In this study, the absolute nodal coordinate formulation is used to create the 36-DOF reduced-order composite thin shell element. The strain and strain energy of the thin-shell element are calculated using the Green-Lagrange strain tensor, while the bending deformation energy of the thin shell element is calculated using the exact expression of curvature, based on continuum mechanics theory and the constitutive relation of the composite material. The generalized mass matrix and stiffness matrix are developed, and the nonlinear dynamic model of the thin shell element is established using the virtual work principle, with numerical simulation used to validate the dynamic characteristics. The results reveal that the dynamic characteristics of the 36-DOF reduced-order composite thin shell element are consistent with those of the virtual prototype, confirming the validity of the model. The proposed model not only addresses the element locking issue, but it also creates a more realistic dynamic model and increases simulation accuracy. The findings could serve as a theoretical foundation for satellite solar panel on-orbit operations.

Multifunctional cementitious composite: Conductive and auxetic behavior

This research focused on developing an innovative multifunctional cementitious material with both conductive and auxetic properties simultaneously. This novel cement-based metamaterial has different applications, ranging from piezoresistivity to structural energy dissipation. The cementitious composite (CC) with an auxetic structure were produced using additive manufacturing techniques. The study involved analyzing different cementitious compositions, including Ultra High-Performance Concrete (UHPC) formulation tailored for both high strength and workability, and flexible mortar. Both types of composites were combined with two types of fibers: recycled carbon and Polyvinyl Alcohol (PVA). Uniaxial compression tests, conductivity, piezoresistivity by load cycles, and Digital Image Correlation (DIC) analysis were carried out on the auxetic cementitious composite (ACC). Among these tested cementitious composites (UHPC and flexible mortar) reinforced with PVA and recycled carbon fibers, only the flexible mortar with carbon fibers achieved the desired multifunctional properties. This success with flexible mortar and carbon fibers suggests promise for this combination. Conversely, UHPC composites with PVA fibers, with or without additional carbon fibers, failed to achieve the targeted functionality. As a result, both piezoresistivity and auxetic properties were achieved. From the auxetic behavior results, the Poisson’s ratio reached -67.5%. This implies that if compressed longitudinally, the specimen is shortened transversely (auxetic behavior) by up to 67.5%. This finding stands out compared to traditional construction materials like concrete and steel, which typically exhibit much lower strain recoveries (15–30%). On the other hand, the specific deformation energy absorption of the auxetic specimen reached 0.076 Jcm3. Moreover, the resistivity reached the small magnitude of 0.15 Ωm at 50 Hz, proving to be a conductive composite. The gauge factor of 4.26 indicates that it can be used as a self-sensing concrete. This innovative cementitious composite opens new possibilities for future applications that require materials with conductive and auxetic behaviors.

Lattice Engineering via Transition Metal Ions for Boosting Photoluminescence Quantum Yields of Lead-Free Layered Double Perovskite Nanocrystals.

Lead-free layered double perovskite nanocrystals (NCs), i.e., Cs4M(II)M(III)2Cl12, have recently attracted increasing attention for potential optoelectronic applications due to their low toxicity, direct bandgap nature, and high structural stability. However, the low photoluminescence quantum yield (PLQY, <1%) or even no observed emissions at room temperature have severely blocked the further development of this type of lead-free halide perovskites. Herein, two new layered perovskites, Cs4CoIn2Cl12 (CCoI) and Cs4ZnIn2Cl12 (CZnI), are successfully synthesized at the nanoscale based on previously reported Cs4CuIn2Cl12 (CCuI) NCs, by tuning the M(II) site with different transition metal ions for lattice tailoring. Benefiting from the formation of more self-trapped excitons (STEs) in the distorted lattices, CCoI and CZnI NCs exhibit significantly strengthened STE emissions toward white light compared to the case of almost non-emissive CCuI NCs, by achieving PLQYs of 4.3% and 11.4% respectively. The theoretical and experimental results hint that CCoI and CZnI NCs possess much lower lattice deformation energies than that of reference CCuI NCs, which are favorable for the recombination of as-formed STEs in a radiative way. This work proposes an effective strategy of lattice engineering to boost the photoluminescent properties of lead-free layered double perovskites for their future warm white light-emitting applications.

Performance analysis of bimodulus frame structures based on deformation energy decomposition method

Performance analysis of bimodulus frame structures based on deformation energy decomposition method

Transferability of Buckingham Parameters for Short-Range Repulsion between Topological Atoms.

The repulsive part of the Buckingham potential, with parameters A and B, can be used to model deformation energies and steric energies. Both are calculated using the interacting quantum atom energy decomposition scheme where the latter is obtained from the former by a charge-transfer-based energy correction. These energies relate to short-range interactions, specifically the deformation of electron density and steric hindrance, respectively, when topological atoms approach each other. In this work, we calculate and fit the energies of carbonyl carbon, carbonyl oxygen, and, where possible, amine nitrogen atoms to the repulsive part of the Buckingham potential for 26 molecules. We find that while the steric energies of all atom pairs studied display exponential behavior with respect to distance, some deformation energy data do not. The obtained parameters are shown to be transferable by calculating root-mean-square errors of fitted potentials with respect to energy data of the same atom in, as far as possible, all other molecules from our data set. We observed that 36% and 10% of these errors were smaller than 4 kJ mol-1 for steric and deformation energy, respectively. Thus, we find that steric energy parameters are more transferable than deformation energy parameters. Finally, we speculate about the physical meaning of the A and B parameters and the implications of the strong exponential and exponential-linear piecewise relationships that we observe between them.

Analytic rotation-invariant modelling of anisotropic finite elements

Anisotropic hyperelastic distortion energies are used to solve many problems in fields like computer graphics and engineering with applications in shape analysis, deformation, design, mesh parameterization, biomechanics and more. However, formulating a robust anisotropic energy that is low-order and yet sufficiently non-linear remains a challenging problem for achieving the convergence promised by Newton-type methods in numerical optimization. In this paper, we propose a novel analytic formulation of an anisotropic energy that is smooth everywhere, low-order, rotationally-invariant and at-least twice differentiable. At its core, our approach utilizes implicit rotation factorizations with invariants of the Cauchy-Green tensor that arises from the deformation gradient. The versatility and generality of our analysis is demonstrated through a variety of examples, where we also show that the constitutive law suggested by the anisotropic version of the well-known As-Rigid-As-Possible energy is the foundational parametric description of both passive and active elastic materials. The generality of our approach means that we can systematically derive the force and force-Jacobian expressions for use in implicit and quasistatic numerical optimization schemes, and we can also use our analysis to rewrite, simplify and speedup several existing anisotropic and isotropic distortion energies with guaranteed inversion-safety.

Influence of GGBFS and alkali activators on macro-mechanical performance and micro-fracture mechanisms of geopolymer concrete in split Hopkinson pressure bar tests

With superior low-carbon emission and low-resource consumption, geopolymer concrete (GPC) is receiving increasing attention as an optimal alternative to conventional building materials for cleaner and sustainable construction. However, the practical application of GPC poses great challenges since its dynamic mechanical performance remains far from well understood. In this study, via a split Hopkinson pressure bar (SHPB) system, a series of dynamic compression tests at strain rates of 45 s-1 to 150 s-1are conducted on GPC specimens with different alkaline activators (AAS)-binder mass ratios (i.e., 10%, 15%, 20%, and 25%) and ground granulated blast furnace slag (GGBFS)-binder mass ratios (i.e., 0%, 30%, 50%, 70%, and 100%). Our testing results comprehensively explored the influence of mix proportions and loading rates on the dynamic mechanical performance of GPC, including the dynamic strength and deformation characteristics, energy evolution and utilization, and progressive failure behavior. The permanent strain, energy dissipation density, and dynamic strength of GPC specimens generally increase with increasing strain rate, while the average fragment size decreases. Under higher loading rates, GPC specimens are featured by denser microcracks, shorter propagation paths, and more prominent stepwise fractures. In addition, GGBFS has a greater impact on dynamic strength, strain rate sensitivity, and energy utilization than AAS. Micro-fracture effect of GPC with different mix proportions is investigated. An appropriate content of alkaline activator (i.e., 20%) and higher GGBFS content (i.e., 100%) promotes the binder depolymerization-aggregation reaction, reduces initial defects inside concrete specimens, and facilitates a more compact block structure.

Achieving near-zero particle generation by simplicity of design—A compliant-mechanism-based gripper for clean-room environments

Lab Automation facilitates high-throughput processes and improves reproducibility and efficiency while removing human action, primary source of contaminating particles. Handling poses a risk of contamination due to close contact with the objects. We propose a novel gripper (CrocoGrip) relying on compliant mechanisms to reduce the amount of contaminating particles generated by the gripper rather than preventing their emission, the latter being the common approach in current grippers. Our novel gripper is actuated by linear solenoids and purely relies on deformation for its motion. As a result, abrasive behavior and, therefore, the generation of particles is reduced without the need for additional sealing. We experimentally proved that only particles smaller than 3.0µm are emitted by the gripper, with a large proportion of the particles being generated by the actuation. The CrocoGrip fulfills the demands of ISO14644 class 5. The gripping relies on the deformation energy of the compliant mechanism, making the gripping energy-efficient and safe. The maximum gripping force achieved by the CrocoGrip was 5.5N. Because the force transmitted to the handling object depends on the design of the gripping jaws, which are interchangeable, the force can be reduced for more sensible handling objects. Using three different sets of jaws, CrocoGrip was able to handle a microplate in SBS-standard, a 50mL Falcon tube, and a Ø60mm Petri dish using a robotic arm. Due to the monolithic design of the CrocoGrip and, as a result, the need for few components, we achieve a simplicity of design, making cleaning, sterilization and maintenance easy, even for nonexperts. The CrocoGrip exploits the advantages of compliant mechanisms, especially for applications requiring clean-room environments. This approach of compliant-mechanism-based grippers enables an increase in the cleanliness of handling processes without an increase in system complexity of the gripper to facilitate the lab automation of highly sensible processes, such as in tissue engineering.

Effect of initial grain size on hot deformation behavior and recrystallization mechanism of Al-Zn-Mg-Cu alloy

Grain size is industrially important for improving mechanical properties and formability. In order to investigate the effect of grain size on the hot workability and deformation mechanisms, Al-Zn-Mg-Cu alloys with different initial grain sizes, 241.2, 100.4 and 48.4 μm, were subjected to hot compression tests. Using the established constitutive equation, the rheological behavior is described and the influence of the initial grain on the thermal deformation behavior is analyzed. Electron back-scatter diffraction (EBSD) analysis was used to study the dynamic recrystallization (DRX) mechanisms of Al-Zn-Mg-Cu alloys with different initial grain sizes. The microstructures obtained under various deformation conditions were analyzed. The results show that decreasing the initial grain size enhances both the peak stress and the activation energy for thermal deformation. Meanwhile, the dynamic recrystallization mechanism varies depending on the initial grain size. Continuous dynamic recrystallization (CDRX) is the primary DRX nucleation mode for coarse-grained alloys. Nonetheless, discontinuous dynamic recrystallization (DDRX) is predominant for alloys with fine grains.

Suzuki segregation behavior and mechanism in a Co–Cr–Fe–Ni–Mo high-entropy alloy

The knowledge of the Suzuki effect in compositionally complex CoNiCrMo and CoCrFeNiMo solid-solution alloys is rather limited. In this study, the enrichment of Co and Mo atoms and depletion of Cr, Fe, and Ni atoms were determined within the region of four atomic layers at stacking faults (SFs) in a typical quinary concentrated solid-solution alloy (Co0.95Cr0.8Fe0.25Ni1.8Mo0.475) by using scanning transmission electron microscopy and energy dispersive X-ray spectroscopy. To better understand the Suzuki effect, two-stage first-principles Monte Carlo (MC) simulations each with up to 3000 trial swap steps were performed. First, the simulation results suggested the strong tendency of Mo segregation at the second nearest neighbor (2NN) sites at SFs. Nonetheless, as a further Mo segregation induces the excessively large lattice distortion and intrinsic strain energy, it would be inhibited. It was deemed one potential reason for the finite Mo segregation. Second, the simulations revealed the origin and formation of co-segregation of Co and Mo atoms. The segregated Mo atoms at the 2NN sites attract Co atoms, forming the local D019-type ordering at SFs. As a consequence, the stacking fault energy can reach a strongly negative value below −500 mJ/m2. Meanwhile, the Co/Mo co-segregated SFs have high stability against phase transitions to intermetallics and martensite at 773 K.

A comparative approach for estimating microstructural characteristics of BaTi1−xZrxO3 (0.0 ≤ x ≤ 0.3) nanoparticles via X-ray diffraction patterns

Barium titanate materials are currently a special topic for scientific research due to their effective technological applications. The tetragonal BaTi1-xZrxO3 (0.0 ≤ x ≤ 0.3) nanoparticles (NPs) were synthesized using a modified citrate technique. The current work provides a comparative approach for the calculation of crystallite size, stress, strain, and elastic characteristics based on X-ray diffraction (XRD) patterns. Various models have been developed to analyze XRD data; these models differ in their assumptions, mathematical approaches, and the type of information they provide. The Scherrer model ignores lattice micro-structures that develop in nanostructures, such as intrinsic strain. To overcome such drawbacks, three Williamson-Hall models, (the uniform deformation model (UDM)), the uniform stress deformation model (USDM), and the uniform deformation energy density model (UDEDM) have been discussed. According to the USDM model, with increasing Zr ion concentrations, interplanar space increases, causing a drop in Young’s modulus. All the previous approaches take into account the diffraction angle (2θ)-dependent peak broadening, which is thought to represent a combination of size and strain-driven induced broadening.Graphical

Deformation Characteristics and Energy Evolution Rules of Siltstone under Stepwise Cyclic Loading and Unloading

Deformation Characteristics and Energy Evolution Rules of Siltstone under Stepwise Cyclic Loading and Unloading