Energy Dissipation Properties Research Articles

Precise distinction of mechanical behavior stages of coal under temperature-pressure constraints and its permeability and energy consumption characteristics

The mechanical behavior and permeability (K) of coal reservoirs are important research directions in the development of coalbed methane recovery. In this study, the raw coal was collected from the Baode block, China. The pseudo-triaxial tests examined the coal mechanical behavior and K under high temperature-pressure (T-P) conditions. We proposed a new micro-slope method to accurately distinguish the deformation stages of coal under high T-P conditions. The whole deformation process is divided into five stages, and the dynamic permeability is divided into six stages. The results show that the K is closely related to the deformation stage and exhibits a U-shaped change with the axial strain, and its minimum value occurs at the end of the elastic deformation. The T and P control the evolution of coal mechanical behavior and K. The peak stress (σmax) and peak strain (εmax) decrease with the T but increase with the P. The initial permeability (K0) decreases with the increase in P and T in the 10–30 MPa and 30–80 °C range, respectively. On the other side, the minimum permeability (Kmin) is least affected by the T and P. The kinetic properties of energy dissipation show that, the T and P control the dynamic changes of K by affecting the energy at different stages inside the coal. This study provides a reference for understanding the mechanical behavior of deep coal reservoirs.

Mechanical response of polyprotein revealed by single-molecule optical tweezers

We researched the mechanical unfolding of protein domains in monomeric protein NuG2 and the tandem polyproteins (NuG2)8 and (NuG2)16 using a dual-trap optical tweezers system. By stretching NuG2 and its polyproteins, (NuG2)8 and (NuG2)16 at the constant pulling speed of 500 nm s−1, we achieved the mechanical unfolding force of each domain in these proteins. Besides, we calculated the energy dissipation of NuG2, (NuG2)8 and (NuG2)16 by measuring the area enclosed by stretching and relaxation traces. Our results represent a key step towards engineering artificial polyproteins with controllable mechanical force and energy dissipation properties for force-buffering and energy dissipator applications.

Functional Anatomy, Impact Behavior and Energy Dissipation of the Peel of Citrus × limon: A Comparison of Citrus × limon and Citrus maxima.

This study analyzes the impact behavior of lemon peel (Citrus × limon) and investigates its functional morphology compared with the anatomy of pomelo peel (Citrus maxima). Both fruit peels consist mainly of parenchyma structured by a density gradient. In order to characterize the lemon peel, both energy dissipation and transmitted force are determined by conducting drop weight tests at different impact strengths (0.15–0.74 J). Fresh and freeze-dried samples were used to investigate the influence on the mechanics of peel tissue’s water content. The samples of lemon peel dissipate significantly more kinetic energy in the freeze-dried state than in the fresh state. Fresh lemon samples experience a higher impulse than freeze-dried samples at the same momentum. Drop weight tests results show that fresh lemon samples have a significantly longer impact duration and lower transmitted force than freeze-dried samples. With higher impact energy (0.74 J) the impact behavior becomes more plastic, and a greater fraction of the kinetic energy is dissipated. Lemon peel has pronounced energy dissipation properties, even though the peel is relatively thin and lemon fruits are comparably light. The cell arrangement of citrus peel tissue can serve as a model for bio-inspired, functional graded materials in technical foams with high energy dissipation.

Phase Field Models for Thermal Fracturing and Their Variational Structures.

It is often observed that thermal stress enhances crack propagation in materials, and, conversely, crack propagation can contribute to temperature shifts in materials. In this study, we first consider the thermoelasticity model proposed by M. A. Biot and study its energy dissipation property. The Biot thermoelasticity model takes into account the following effects. Thermal expansion and contraction are caused by temperature changes, and, conversely, temperatures decrease in expanding areas but increase in contracting areas. In addition, we examine its thermomechanical properties through several numerical examples and observe that the stress near a singular point is enhanced by the thermoelastic effect. In the second part, we propose two crack propagation models under thermal stress by coupling a phase field model for crack propagation and the Biot thermoelasticity model and show their variational structures. In our numerical experiments, we investigate how thermal coupling affects the crack speed and shape. In particular, we observe that the lowest temperature appears near the crack tip, and the crack propagation is accelerated by the enhanced thermal stress.

Injectable hydrogel with nucleus pulposus-matched viscoelastic property prevents intervertebral disc degeneration.

Background/ObjectiveIntervertebral disc (IVD) degeneration (IVDD) that greatly affected by regional biomechanical environment is a major cause of low back pain. Injectable hydrogels have been commonly studied for treatment of IVDD due to their capability of mimicking extracellular matrix structure to support cellular behavior and clinical prospects in minimally invasive treatment. However, most hydrogels suffer from complicated chemistry, potential uncertainty and toxicity from in-situ gelation, and mismatch with IVD mechanical environment that limit their therapeutic effects or clinical translation in IVDD or intervertebral disc defect repair. For IVD lesion repair, the study aims to develop a novel hydrogel with shear-thinning enabled injectability, high bio-safety, and mechanical properties adaptable to the IVD environment, using a simple chemistry and method. And therapeutic efficacy of the novel hydrogel in the treatment of IVDD or intervertebral disc defect will be revealed.MethodsA glycerol cross-linked PVA gel (GPG) was synthesized based on multiple H-bonds formation between glycerol molecules and PVA chains. The rheological and mechanical properties were tested. The swelling ratio was measured. The micro-architecture was observed through scanning and transmission electron microscopes. Nucleus pulposus (NP) cells were cultured in GPG-coated plates or silicone chambers treated under hydrostatic or dynamic loading in vitro, and examined for proliferation, vitality, apoptosis, expression of catabolic and anabolic markers. GPG was injected in needle puncture (IDD) or NP discectomy (NPD) models in vivo, and examined through magnetic resonance imaging, micro-computed tomography scanning and histological staining.ResultsGPG had a highly porous structure consisting of interconnected pores. Meanwhile, the GPG had NP-like viscoelastic property, and was able to withstand the cyclic deformation while exhibiting a prominent energy-dissipating capability. In vitro cell tests demonstrated that, the hydrogel significantly down-regulated the expression of catabolic markers, maintained the level of anabolic markers, preserved cell proliferation and vitality, reduced apoptotic rate of NP cells under pathologically hydrostatic and dynamic loading environments compared to cells cultured on untreated plate or silicone chamber. In vivo animal studies revealed that injection of GPG efficiently maintained NP structural integrity, IVD height and relative water content in IDD models, and stimulated the fibrous repair in NPD models.ConclusionThis study showed that GPG, with high injectability, NP-like viscoelastic characteristics, good energy-dissipating properties and swelling capacities, preserved NP cells vitality against pathological loading, and had therapeutic effects on IVD repair in IDD and NPD models.The translational potential of this articleEffective clinical strategy for treatment of intervertebral disc degeneration (IVDD) is still lacking. This study demonstrates that injection of a hydrogel with nucleus pulposus-matched viscoelastic property could remarkably prevent the IVDD progress. Prepared with simple chemistry and procedure, the cell/drug-free GPG with high bio-safety and shear-thinning enabled injectability bears great translational potential for the clinical treatment of IVDD via a minimally invasive approach.

The energy dissipation property of MWCNTs/cement paste composites

The effects of loading frequency, temperature and multi-walled carbon nanotubes (MWCNTs) on the energy dissipation property of cement paste were explored in the paper. Energy dissipation was characterized by loss factor (defined as loss modulus /storage modulus E″/E′), and the roles of MWCNTs were analyzed emphatically by micro tests. The energy dissipation of cement paste originated from the sliding of C-S-H sheets at nanoscale and the friction of C-S-H globules at microscale. The loss factor decreased with the increase of loading frequency and temperature. After analyzing the micro tests results such as nuclear magnetic resonance and atomic force microscope, the mechanism of MWCNTs enhancing the energy dissipation property of cement paste was proposed: (1) at nanoscale, the mean chain length of C-S-H was increased by MWCNTs, leading to the sliding area of C-S-H sheets larger and increasing energy dissipation; (2) at microscale, the morphology of C-S-H gradually changed from globules to foil due to the presence of MWCNTs, which increased the friction area and the energy dissipation was enhanced; (3) MWCNTs were fibrous and bonded with C-S-H, and the friction between the their interfaces dissipated energy under alternating stress; (4) the small pore volume and pore roughness were increased by MWCNTs, which were contributed to increase the energy dissipation.

Nonlinear wave propagation in locally dissipative metamaterials via Hamiltonian perturbation approach

The cellular microstructure of periodic architected materials can be enriched by local intracellular mechanisms providing innovative distributed functionalities. Specifically, high-performing mechanical metamaterials can be realized by coupling the low-dissipative cellular microstructure with a periodic distribution of tunable damped oscillators, or resonators, vibrating at relatively high amplitudes. The benefit is the actual possibility of combining the design of wave-stopping bands with enhanced energy dissipation properties. This paper investigates the nonlinear dispersion properties of an archetypal mechanical metamaterial, represented by a one-dimensional lattice model characterized by a diatomic periodic cell. The intracellular interatomic interactions feature geometric and constitutive nonlinearities, which determine cubic coupling between the lattice and the resonators. The non-dissipative part of the coupling can be designed to exhibit a softening or a hardening behavior, by independently tuning the geometric and elastic stiffnesses. The nonlinear wavefrequencies and waveforms away from internal resonances are analytically determined by adopting a perturbation technique. The employed approach makes use of tools borrowed from Hamiltonian perturbation theory, together with techniques often used in the context of nearly-integrable Hamiltonian systems.The dispersion spectra are determined in closed, asymptotically approximate, form as a nonlinear function of the time-dependent decreasing amplitude decrement. The invariant manifolds defined by the harmonic periodic motions are also analytically determined. The asymptotic results are further validated numerically.

Design, manufacturing, and performance evaluation of a novel smart roller bearing equipped with shape memory alloy wires

In this study, a new type of seismic isolation device, called shape memory alloy (SMA) wire-based roller bearing (SMA-RB) is developed and introduced. The SMA-RB has been designed, manufactured, and experimentally tested. This bearing consists of cylindrical roller bearings and SMA wires with straight or cross configurations, as supplementary damping elements. In such a smart bearing, the superelastic (SE) SMA wires are passed through the hooks/pulleys attached to the supporting plates of the bearings in different configurations. The rollers provide lateral flexibility, and SMA wires supply energy dissipation and self-centering (SC) properties. In the manufacturing stage, a new mechanism for coupling wires (i.e. SMA wire joiner/coupler) is proposed. The results show that SMA wires, made of nickle titanium (NiTi), provide a SC damping mechanism with almost zero residual deformation which can effectively control the device from over-displacement. While using pulleys and newly designed wire joiners in the SMA-RB, the bearing can experience a stable cyclic behavior. Since the rollers generate a negligible amount of frictional force, the SE NiTi wires with a flag-shaped hysteresis mainly contribute to the overall shear hysteretic response of the SMA-RB. A triangular-shaped constitutive model can be used to accurately describe the hysteretic behavior of SMA-RB with different wire configurations.

A positivity-preserving and free energy dissipative hybrid scheme for the Poisson-Nernst-Planck equations on polygonal and polyhedral meshes

This paper develops a positivity-preserving and free energy dissipative hybrid scheme for the multi-dimensional Poisson-Nernst-Planck equations with multiple ions on unstructured polygonal and polyhedral meshes. It is built on the linear virtual element method for the Poisson-type equation for the electrostatic potential and a cell-centered finite volume scheme for the Nernst-Planck equations for the ion concentrations, and preserves the positivity of the ion concentrations, the mass conservation, the free energy dissipation and steady-state properties. The existence of the numerical solutions is also discussed. Numerical results demonstrate the effectiveness of the proposed two- and three-dimensional schemes.

Energy quadratization Runge–Kutta method for the modified phase field crystal equation

In this paper, we propose high order and unconditionally energy stable methods for a modified phase field crystal equation by applying the strategy of the energy quadratization Runge–Kutta methods. We transform the original model into an equivalent system with auxiliary variables and quadratic free energy. The modified system preserves the laws of mass conservation and energy dissipation with the associated energy functional. We present rigorous proofs of the mass conservation and energy dissipation properties of the proposed numerical methods and present numerical experiments conducted to demonstrate their accuracy and energy stability. Finally, we compare long-term simulations using an indicator function to characterize the pattern formation.

Identification of energy dissipative characteristics of unidirectional layers from energy dissipative properties of multilayered composite materials

Identification of energy dissipative characteristics of unidirectional layers from energy dissipative properties of multilayered composite materials

Kobayashi–Warren–Carter type systems with nonhomogeneous Dirichlet boundary data for crystalline orientation

In this paper we study the Dirichlet problem for the Kobayashi–Warren–Carter system. This system of parabolic PDE’s models the grain boundary motion in a polycrystal with a prescribed orientation at the boundary of the domain. We obtain global existence in time of energy-dissipative solutions. The regularity of the solutions as well as the energy-dissipation property permit us to derive the steady-state problem as the asymptotic in time limit of the system. We finally study the ω-limit set of the solutions; we completely characterize it in the one dimensional case, showing, in particular that orientations in the ω-limit set belong to the space of SBV functions. In the two dimensional case, we give sufficient conditions for existence of radial symmetric piecewise constant solutions.

Energy dissipation and effective properties of a nominally elastic composite material

Composites such as architected metamaterials made from elastic materials can display energy absorbing or dissipative behavior associated with snap-through and other instabilities. These instabilities result in conversion of elastic strain energy of the elastic parent material of the composite to kinetic energy which is then dissipated over longer time scales via processes including air drag. Here we propose a new approach at modelling such composites by appealing to ideas from statistical mechanics, viz. we postulate that the state of such a composite comprising a large number of unit cells is given by maximization of entropy. We first develop the theoretical homogenization framework for such a composite and provide expressions of the effective properties. Solution of the governing equations requires sampling over all the states that the composite can attain, and this is efficiently done by employing the Nested Sampling algorithm to construct a sample with the required distribution. Using this numerical scheme, we present predictions of the volumetric compressive response of two model materials, i.e. two-dimensional (2D) architected materials with honeycomb-like microstructures and cell walls made from an elastic material. Unlike traditional homogenization schemes, the volumetric stress versus strain response now depends on an additional internal state variable that characterizes the vibrational modes of the microstructure, i.e., the predictions are akin to what is commonly known as an Equation-of-State (EoS). We finally demonstrate the utility of the method by using the predicted EoS to extract the shock response of the architected material and compute the dissipation within the shock.

Harnessing fractal cuts to design robust lattice metamaterials for energy dissipation

Lattice metamaterials exhibit remarkable mechanical properties and novel functionalities, such as high specific stiffness, fracture toughness, tunable vibroacoustic properties, and energy absorption. This study explores a group of lattice metamaterials with fractal cuts that feature energy dissipation via structural sliding friction mechanisms and intrinsic material damping. Lattice metamaterials with three types of fractal cuts patterns were designed and fabricated using additive manufacturing. Three-point bending tests and numerical analysis have been combined to investigate their bending behavior. Experimental results show that the structural bending compliance of the metamaterials can be sharply enhanced by increasing the fractal orders, while at the same time keeping the shape recoverability during cyclic loading. Loss factors associated with the cyclic bending of these metamaterials are almost independent of the fractal order used, which is attributed to the synergistic effect between friction and viscoelasticity. It is further demonstrated via validated finite element models that the sliding friction plays a critical role by investigating the effects of the bending displacement and sample thickness on the flexural behavior. Results suggest that the magnitude of the maximum bending displacement has a negligible effect on the loss factors, and a power scaling law exists between bending stiffness and sample thickness. This study suggests that fractal lattice metamaterials have unique energy dissipation properties, with potential applications in many industrial sectors such as defense, energy, and transportation.

Research on the Tensile Mechanical Properties of a Braided Corrugated Hose and Its Axial Stiffness Model

Braided corrugated hoses are widely used in displacement compensation and vibration absorption environments due to their excellent flexibility and energy dissipation properties; however, the axial stiffness has rarely been discussed before as an important physical property of braided corrugated hoses. In this paper, the theoretical axial stiffness model for braided corrugated hoses is established based on the energy method and the theory of the curved beam. The influences of the braiding parameters of the metallic braided tube and the structural parameters of the bellows on the axial stiffness are also discussed. Through finite element tensile testing, the axial stiffness curves of the braided corrugated hose under different braiding angles and different wire diameters are obtained. The theoretical axial stiffness model is in good agreement with the simulation experiment, which reflects the nonlinear effects of the braiding angle and wire diameter on the braided corrugated hose. This paper provides an accurate method and basis for the design of braided corrugated hoses in the future.

Energy dissipating poly(hydroxyurethane) elastomers – Synthesis, characterization and comparison with shear thickening fluid materials

In this article we report preparation and characterization of cross-linked non-isocyanate poly(hydroxyurethane) polymeric materials showing energy-dissipating properties. The materials were obtained by the ring-opening polyaddition reaction of hyperbranched multi(cyclic carbonate) (HBPG2) with various diamines. The hyperbranched multi(cyclic carbonate) was obtained in two step procedure including anionic polymerization of glycidol with trimethylolpropane (TMP) as a core yielding polyglycerol (HBPG1) and reaction of terminal vicinal hydroxyl groups of HBPG1 with dimethyl carbonate in the presence of potassium carbonate. HBPG1 and HBPG2 were characterized using various NMR techniques, FTIR and MALDI-ToF mass spectroscopy. Thermal and mechanical properties of elastomers, including dissipated energy capacity have been studied. Analysis of force absorbing efficiency test results showed that synthesized elastomers have the capability to dissipate about 60% of the energy. The energy dissipating properties of obtained poly(hydroxyurethane) elastomers were similar to those of shear thickening fluid materials that are currently used in human body protectors, in vibration damping devices or sound insulations. The article proves that it is possible to obtain advanced engineering materials using environmentally friendly materials.

A Geometric Integration Approach to Nonsmooth, Nonconvex Optimisation

The optimisation of nonsmooth, nonconvex functions without access to gradients is a particularly challenging problem that is frequently encountered, for example in model parameter optimisation problems. Bilevel optimisation of parameters is a standard setting in areas such as variational regularisation problems and supervised machine learning. We present efficient and robust derivative-free methods called randomised Itoh–Abe methods. These are generalisations of the Itoh–Abe discrete gradient method, a well-known scheme from geometric integration, which has previously only been considered in the smooth setting. We demonstrate that the method and its favourable energy dissipation properties are well defined in the nonsmooth setting. Furthermore, we prove that whenever the objective function is locally Lipschitz continuous, the iterates almost surely converge to a connected set of Clarke stationary points. We present an implementation of the methods, and apply it to various test problems. The numerical results indicate that the randomised Itoh–Abe methods can be superior to state-of-the-art derivative-free optimisation methods in solving nonsmooth problems while still remaining competitive in terms of efficiency.

Energy dissipation and rheological property degradation of asphalt binder under repeated shearing with different oscillation amplitudes

Time sweep test with four oscillation amplitudes was conducted to investigate the energy dissipation behavior and rheological property evolution of asphalt binder under repeated shearing. It was found that the energy dissipation behavior and rheological property evolution strongly depend on the oscillation amplitudes of fatigue loads and can both be majorly separated into two types. Variations in dissipated energy (DE) were related to the different damage modes of asphalt binder. In addition, the fatigue failure criteria derived from DE were evaluated. The dissipated energy ratio and cumulative energy ratio are not suitable for identifying fatigue failure point of asphalt binder.

Rigid and flexible polyimide aerogels with less fatigue for use in harsh conditions

Polyimide aerogels possess various applications in harsh environment but are often limited by poor mechanical property. The ice template method to construct a layered aerogel has structural advantages, but there are still problems of insufficient compression recovery and anisotropy. We investigated the method of forming a spring-like bridge in layered structure, and verified the effect of bridges on the compression deformation, compressive strength, energy dissipation, and fatigue properties. Based on structural observations, a corresponding force mechanism was proposed. After 10,000-cyclic compression at 50% strain, PI aerogels had only 5.8% plastic deformation, 82% stress retention and stable energy dissipation coefficient below 0.3. Interestingly, the compressive performance was isotropic in horizontal direction. Combined with low thermal conductivity, PI aerogels had high structural stability when repeatedly used at 300 °C. This research may provide an available method for design of high-strength and high-toughness polymer aerogels suitable for harsh environment.

Experimental and numerical study on thin-walled hollow bridge piers

Research on thin-walled hollow bridge piers is of great importance to the large bridge. To study the nonlinear behavior of the thin-walled hollow bridge piers, two rectangular pier specimens have been tested under quasi-static cyclic lateral displacement and different axial loads. For easier comparison, these two specimens have been tested with constant load and varied load separately. Then an MSC. Marc model is built to compare the skeleton line and energy dissipation properties with experimental results. In consideration of the impact of some important parameters, a parametric numerical model has been built to test its performance with experimental results adopting different axial force and wall height-to-thickness ratio.