Elastic Expansion Research Articles

Theoretical method and experimental verification for solving two/three component phononic crystals based on comsol partial differential equation module

Abstract In order to reduce the low frequency vibration and noise of ships, the phononic crystal structure is used to control the vibration and noise of ships. Based on three-dimensional spatial elastic wave theory and plane wave expansion method, combined with the differential equation module of finite element software, the band structure and transport characteristics of phononic crystal structure can be accurately solved. The correctness and feasibility of this method are verified by comparison with the simulation results of solid mechanics module of finite element software, which provides a new idea for solving phononic crystal structure. It lays a solid foundation for further study of phononic crystal structure. At the same time, this paper studies a new phononic crystal sandwich plate structure, which is applied to the vibration and noise reduction of ships. The theoretical method and experiment are used to study the structure, which proves that the structure has good vibration and noise reduction performance, and further explains the correctness and feasibility of the theoretical method. Based on this calculation method, it can be used to study the effect of the geometrical parameters and material parameters of phononic crystal structure on the band gap. By adjusting these parameters reasonably, the ship can achieve a good effect of vibration and noise reduction.

Mechanical properties and piecewise constitutive model of fine sandstone in mining area of western China

Owing to the differences in sedimentary environments in the mining areas of western China, the mechanical properties of rocks in this region are significantly different from those in the central and eastern regions. Therefore, uniaxial cyclic loading-unloading tests were conducted on fine sandstone found in many roof rocks to study the evolution laws of mechanical properties, deformation characteristics, acoustic emission (AE) parameters, and energy under cyclic loading and unloading conditions. The accumulated residual strain, dissipative energy, acoustic emission cumulative ringing counts, and cumulative energy were introduced to characterize the degree of rock damage. Based on this, a piecewise constitutive model was established for fine sandstone. The results indicate that (1) the cumulative ringing counts and cumulative energy of the AE increase in a stepwise manner with an increase in the cyclic loading and unloading times. Still, there is a sudden increase in the plastic failure and post-peak failure stages. (2) The fine sandstone specimens’ input energy, elastic energy, and dissipative energy density increased nonlinearly during the cyclic loading tests. Owing to the closure of the primary pores in the microfracture compaction stage, dominant matrix deformation in the elastic deformation stage, and development and expansion of cracks in the plastic failure stage, with an increase in the cyclic loading and unloading times, the dissipative energy ratio first decreased and then increased. (3) Based on the tangential modulus, residual strain, and Felicity ratio, fine sandstone’s cyclic loading and unloading stress-strain curves were divided into microfracture compaction, elastic deformation, and plastic failure stages. The piecewise constitutive model of fine sandstone constructed with accumulated AE energy was the closest to the real stress-strain curve of the rock, and the deviations of the peak stress and peak strain from the actual situation were 0.52% and 0.84%, respectively. The research results can provide theoretical support for identifying the degree of rock damage in western mining areas and ensure the safe and efficient development of coal resources.

Development and Performance Evaluation of a Composite Elastic Asphalt Precast Expansion Joint

Development and Performance Evaluation of a Composite Elastic Asphalt Precast Expansion Joint

Elastic mode expansion in smoothed particle hydrodynamics framework for hydroelasticity and validation with 3D hydroelastic wedge impact experiments

To perform an efficient hydroelastic simulation with violent free surface interactions, we extend δ+ SPH to elastic modes of a floating structure through GPU parallelization, which includes the correction of velocity divergence with the deformation and computation of the structure's strain. Free surface interaction is supplemented with a segmented particle shifting and tensile instability correction. We validate the developed hydroelastic simulation for experiments of elastic wedge impacts with aluminum and composite panels. Through comparative analysis with different deadrise angles and impact velocities, we find that the improved free surface interactions reduce early separation from the deforming panels, leading to better prediction of the wedge acceleration and reasonably well-matched profiles of the free surface and panel deformation. The marginal difference is attributable to the water passing through the gaps of the physical test model built in three dimensions, which is absent in the simulation setup. Comparing strain time series, measured at two locations on the elastic panels, through three sets of simulations in different dimensions of the simulation set-up and mode shapes, we see that three-dimensional simulation with correct mode shapes in three dimensions accurately predicts the strain time series at both locations as well as the wedge acceleration. The hydroelastic simulation through the modal expansion in GPU parallelization can be utilized to efficiently predict various hydroelastic phenomena with violent free surface interactions.

Yielding onset in FGM thick-walled spherical shells under thermo-mechanical loading

Based on von Mises yield criterion, a thermoelasto-plastic analysis of a thick-walled spherical shell composed of functionally graded material (FGM) subjected to internal pressure and thermal gradient is conducted in order to accurately predict the onset radius of yielding within the vessel wall. The modulus of elasticity, thermal conductivity and thermal expansion coefficients, and yield stress of FGM are assumed to follow power-law functions in radius according to Erdogan’s model. The equilibrium differential equation of the shell under thermo-mechanical loading in steady-state conduction heat transfer are derived analytically and then solved to determine through-thickness variations of the radial and circumferential stresses and radial displacement in elastic and perfectly plastic zones in the vessel wall. The presented approach leads to the definition of new formulation to predict the onset radius of yielding. Moreover, a neural network (NN) solution to reliable quantify the influence of all uncertain input parameters with respect to uncertain output parameter is utilized. The numerical results showed that for various FGM parameters and specific thermal gradient, the plastic zone can commence from inside radius, outside radius, simultaneously in both radii, or may be launched in the intermediate radius of the spherical shell wall.

Mechanical properties and energy evolution of outburst coal seams under different load regimes

AbstractCoal elasticity and gas expansion are important factors for coal and gas outburst. During the outburst process, the elastic strain energy of coal is mainly released from the stress region, and the gas expansion energy near the working face is larger, and it is not a continuous release process. To reveal the mechanical characteristics and energy evolution of outburst coal seam, uniaxial and triaxial compression tests were carried out on outburst coal seam samples under different loading methods. The experimental results show that the elastic characteristics become more obvious with the increase of loading rate, the peak strain increases, the elastic modulus is linearly related with the loading rate，and the overall degree of fragmentation increases with the increase of loading rate, which is consistent with the severity of macroscopic coal failure. The failure mode of coal under uniaxial compression conditions is often manifest as brittle failure. The strength characteristics of coal under different loading rates comply with the Mohr‐Coulomb criterion, and the peak strength is linearly related to the failure time and loading rate. With the increasing confining pressure causes the failure of coal samples to transition from ductile to brittle, and the failure mode develops from local shear to overall splitting. The elastic energy evolution curve is consistent with its stress‐strain curve. With the increase of confining pressure, the limiting elastic energy and peak total energy increase in a quasi‐linear manner. The accumulated limit elastic energy plays an important role in the failure of coal samples, and the macroscopic manifestation thereof is that the coal samples fail more severely under high confining pressure conditions than under low confining pressure conditions. The research results are of great significance for the comprehensive prevention and control of coal and gas outburst.

Edge computing resource scheduling method based on container elastic scaling.

Edge computing is a crucial technology to solve the problem of computing resources and bandwidth required for extensive edge data processing, as well as for meeting the real-time demands of applications. Container virtualization technology has become the underlying technical basis for edge computing due to its efficient performance. Because the traditional container scaling strategy has issues such as long response times, low resource utilization, and unpredictable container application loads, this article proposes a method for scheduling edge computing resources based on the elastic scaling of containers. Firstly, a container load prediction model (Trend Enhanced-Temporal Convolutional Network, TE-TCN) is designed based on the temporal convolutional neural network, which features an encoder-decoder structure. The encoder extracts potential temporal relationship features from the historical data of the container load, while the decoder identifies the trend item of the container load through the trend enhancement module. Subsequently, the information extracted by the encoder and decoder is fed into the fully connected layer to facilitate container load prediction using the dual-input ResNet method. Secondly, Markov decision process (MDP) is used to model the elastic expansion problem of containers in multi-objective optimization. Utilizing the prediction outcomes of the TE-TCN load prediction model, a time-varying action space is formulated to address the issue of excessive action space in conventional reinforcement learning. Subsequently, a predictive container scaling strategy based on reinforcement learning is devised to align with the application load patterns in the container environment, enabling adaptation to the surge in traffic generated by the container environment. Finally, the experimental results on the WorldCup98 dataset and the real dataset show that the TE-TCN model can accurately predict the container load change. Experiments in the actual environment demonstrate that the proposed strategy reduces the average response time by 16.2% when the burst load arrives, and increases the average CPU utilization by 44.6% when the jitter load occurs.

High-temperature structure, elasticity, and thermal expansion of ε-ZrH1.8

Zirconium hydride is a promising candidate material for nuclear microreactor applications as a solid-state moderator component, owing to its favorable neutronics properties and good thermal stability over other metal hydrides. In the present work, the crystal structure, thermal expansion, and elastic properties of the hydrogen-rich ε phase hydride were measured at elevated temperatures in the range 300–900 K. Samples were prepared by direct hydriding Zircaloy-4 metal – a nuclear-grade zirconium alloy. Room-temperature lattice parameters agree well with those reported from literature for unalloyed zirconium hydride and fall within an observed quadratic H-content dependence. The coefficients of thermal expansion, determined from lattice expansion and dilatometry, agree well within our work but were about 30 % lower than those reported by others for unalloyed hydrides. Density functional theory-based molecular dynamics simulations were used to compare with thermal expansion and elasticity measurements. Results showed lattice parameter temperature dependence and slope of thermal expansion align with those from measurements. Based on diffraction scans at select temperatures, ε phase remained stable in air up to at least 770 K. Likewise, dilatometry showed smooth thermal expansion up to the thermal decomposition temperature around 950 K. The precise decomposition temperature was not determined via diffraction due to sparse scanning. The complete elastic property measurements were gathered for ε-phase Ziracloy-4 hydride for the first time. Young's modulus was lower compared to the metal and δ hydride phases. High-temperature elasticity measurements were limited to <350 K due to acoustic dissipation effects.

Dimensional change and springback of spherical shell in cryogenic forming

Cryogenic forming has been developed to manufacture thin-walled curved aluminum alloy components, whose final dimensions are affected by cryogenic shrinkage and springback. Therefore, dimensional changes of spherical shell in cryogenic forming were studied theoretically and experimentally. The cryogenic forming process was discussed to elucidate the factors affecting the dimensional change. The stress distribution was analyzed to qualitatively reveal the springback behavior. Cryogenic dimensional measurement devices were built to quantitatively evaluate the dimensional changes in the forming processes of punch cooling, springback, and specimen restoration to room temperature. The temperature dependencies of the elastic modulus and expansion coefficient were modeled to quantitatively calculate the effect of thermal expansion and contraction on the dimensions of specimen and punch. The theoretical analysis results indicate that depth reduction and opening expansion are produced by cryogenic springback, determined by the radial stress, hoop stress, and bending moment in different deformation regions. The cryogenic springback in the biaxial tensile stress zone was reduced by 37.8 % owing to the increasing radial deformation and decreasing bending deformation. In contrast, cryogenic springback in the tensile-compressive stress zone increased by 30.8 %. The punch cooling shrinkage and specimen warming expansion in depth direction can reduce for the dimensional deviation caused by springback but cause the opposite effect in hoop direction. Expansion and shrinkage were effectively predicted using the proposed model, with an error of less than 16 %. The deformation region of the biaxial tensile stress can be enlarged by the significantly improved hardening ability at cryogenic temperature, which benefits enhancing deformation uniformity and further reduces springback. Therefore, cryogenic forming offers considerable potential for the precision manufacturing of aluminum alloy deep-cavity thin-walled components.

Effect of repeated temperature cycles on thermal expansion coefficient and elastic moduli of high porosity chalks

This paper describes the impact of repeated temperature cycles on elastic mechanical parameters of chalk. The experiments were performed at both hydrostatic and deviatoric stress geometries at an axial stress 70% of the stress at failure. Thus, shear failure tests are reported. Geomechanical stability during cooling was evaluated at constant axial stress, while the side stress was reduced to counteract thermal contraction, ensuring uniaxial strain conditions. The study was motivated by the fact that chalk reservoirs are exposed to cooling due to intermittent water injection during hydrocarbon extraction and are future prospects for CO2 storage. Detrimental effects on rock-mechanical stiffness and strengths were anticipated because temperature cycles are known to degrade calcite cemented sedimentary rocks and marble. This study documents how temperature cycles influence elasticity and thermal expansion coefficient of two chalks with different degree of calcite cementation. The more indurated and less porous Kansas chalk, and the less indurated and more porous Belgian Mons chalk.Following temperature cycling, elastic bulk modulus measured under hydrostatic conditions decreased for the softer Mons chalk, while no significant effect was found for the stiffer Kansas chalk. For both chalks, Young's modulus measured under deviatoric stress, showed no effect of temperature cycling. At hydrostatic stresses, the thermal expansion coefficient of the Kansas chalk was found to decrease with increasing number of temperature cycles, while a less clear, but similar trend was seen for the Mons chalk samples. The thermal-elastic coupling coefficient, needed to evaluate effective stresses during cooling, was measured before and after the repeated temperature changes.

A novel mixture rule for multi-layer plates with thermal bending and twisting effects applied to FOCoS devices

A novel approach for reducing the simulation time of highly complex fan-out chip on substrate (FOCoS) structures was developed. Based on the Uflyand-Mindlin plate theory and using the multi-layer plate technique, we have successfully obtained the effective elastic and thermal expansion constants incorporating with the effects of bending and twisting for a two-layer plate structure. The newly developed approach was then applied to simulate, by the finite element method, a variety of cases commonly encountered in practice, such as a slightly asymmetric substrate, an extremely asymmetric rigid structure, and an extremely asymmetric soft structure, with a maximum error of only 3 μm. Remarkably, applying the present mixture rule to simulate the complete FOCoS structure has resulted in an error of only 10 μm with up to 75 % of reduction in the number of mesh elements. The present approach, hence, provides an effective and reliable means for simulating the ever increasingly important FOCoS structures in the rapidly evolving information technology applications.

Investigation of the mechanical behavior of rock-like material with two flaws subjected to biaxial compression

The biaxial compression experiments of rock-like materials with two flaws are carried out under different flaw inclination angle, rock bridge ligament angle, lateral stress. The experimental studies show that crack propagation modes of rock-like material are as follows: wing crack through mode (Y mode), shear crack through mode (J mode), mixed crack through mode (wing shear JY mode), longitudinal extension of crack and transverse shear splitting. prefabricated fractured rock specimens have experienced the closing stage of prefabricated fractures, the elastic deformation stage, the generation and expansion of cracks (or plastic strengthening), and the residual loading stage. The peak strength of the specimen is increases with the increase of flaw inclination angle and lateral stress. With the increase of the rock bridge ligament angle, the failure of the rock bridge region changes from the shear crack failure to composite failure of shear crack and the wing type tensile crack failure, and then to the wing crack failure. With the increase of the lateral pressure, the failure of the specimen changes from the wing type tensile crack failure to the wing type and shear crack failure, and then to shear crack failure. The flaw inclination angle mainly changes the form of crack growth but does not effect on the failure modes. The counting number of acoustic emission events at the center of the sample is relative large, indicating that the cacks appear in the part of the rock bridge firstly. With the increasing of loads, the cracks of the rock bridge expanding constantly and connecting finally. The changes of acoustic emission event counts is consistent with the macroscopic damage form obtained from the experiments.

A Novel Method to Calculate Water Influx Parameters and Geologic Reserves for Fractured-Vuggy Reservoirs with Bottom/Edge Water

In practical oilfield production, the phenomenon of water influx typically shortens the water-free recovery period of wells, leading to water flooding and causing a sharp decline in the production well yields, bringing great harm to production. Water invasion usually occurs as a result of the elastic expansion of the water as well as the compaction of the aquifer pore space. However, it can be due to the special characteristics of fractured-vuggy reservoirs such as non-homogeneity and the discrete distribution of the pore spaces. It is challenging to use traditional seepage flow theories to analyze the characteristics of water influx. Also, reservoir numerical simulation methods require numerous parameters which are difficult to obtain, which significantly reduces the accuracy of the results. In this study, considering the driving energy for water influx, a water influx characteristic model was obtained by fitting a graph plate. Subsequently, an iterative calculation method was used to simultaneously obtain water influx volume and OOIP. The aquifer to hydrocarbon ratio was determined by fitting the water influx curve with the graphic plate. Results show that the calculation method is sensitive to the values of reservoir pressure and the crude oil formation volume factor. After applying the method to one field case, it was discovered that water influx performance can be characterized into two types, i.e., linear water influx and logarithmic water influx. In the early stages, the water influx rate of logarithmic water influx is greater compared to linear water influx. However, the volume and energy of waterbody are limited, and the water invasion phenomenon occurs almost exclusively within a short period after the invasion. On the other hand, the volume of waterbody invaded by linear water influx is larger, and it can maintain a stable rate of water influx. The results of the study can provide theoretical support for the waterbody energy evaluation and dynamic analysis of water influx, as well as the control and management of water in these types of reservoirs.

Observation of a Picosecond Light-Induced Spin Transition in Polymeric Nanorods.

Spin transition (ST) materials are attractive for developing photoswitchable devices, but their slow material transformations limit device applications. Size reduction could enable faster switching, but the photoinduced dynamics at the nanoscale remains poorly understood. Here, we report a femtosecond optical pump multimodal X-ray probe study of polymeric nanorods. Simultaneously tracking the ST order parameter with X-ray emission spectroscopy and structure with X-ray diffraction, we observe photodoping of the low-spin-lattice within ∼150 fs. Above a ∼16% photodoping threshold, the transition to the high-spin phase occurs following an incubation period assigned to vibrational energy redistribution within the nanorods activating the molecular spin switching. Above ∼60% photodoping, the incubation period disappears, and the transition completes within ∼50 ps, preceded by the elastic nanorod expansion in response to the photodoping. These results support the feasibility of ST material-based GHz optical switching applications.

Analysis of mechanical stresses in silicone rubber joint tubes using a hyper-elastic model

A 2D model of a silicone rubber joint tube is proposed to calculate mechanical pressure. An analysis of radial and circumferential stresses within a joint tube based on a hyper-elastic model, employing finite element method is presented. This paper shows that assuming a constant elastic modulus for rubber leads to miscalculation of stresses within the joint tube. In addition, restricting the expansion ratio without considering the material’s elasticity could elevate the possibility of introducing high circumferential stress. Depending on the elastic modulus and expansion ratio, these circumferential stresses may approach 50% of the material’s tensile strength however, none of the simulated materials showed any critical values. A rigid semiconducting deflector could potentially generate significant circumferential stress, especially at the deflector-joint insulation interface, posing an increased risk if the material is relatively weak. Achieving the required pressure with stiffer materials necessitates a lower expansion ratio, while softer materials demand higher expansion ratios to accomplish the necessary pressure levels.

Physicochemical characteristics of tannia cocoyam (Xanthosoma sagittifolium) corm flour compared to flours and starches of other grains and tubers

Tannia cocoyam corm is a less popular pantropical carbohydrate source, whereas it has the potential to support food and nutrition security, especially in dry areas. Processing tannia cocoyam corm into flour can increase its use in various food products. This study aimed to determine the yield, nutrition, color, tap bulk density, water absorption capacity (WAC), oil absorption capacity (OAC), swelling capacity, and emulsion activity and stability of tannia cocoyam corm flour compared to sago starch, cassava flour and starch, mung bean starch, corn starch, wheat flour, rice and glutinous rice flours, and potato flour. The significant characteristics of tannia cocoyam corm flour were rather low in calories (dry basis), relatively high in WAC and swelling capacity, low in OAC, and showed emulsion activity and stability. Based on these data, it is suitable for use in mixed and processed food products that require juicy, elastic, and volume expansion characteristics; recommended for food products that are lower in calories and oil content; and can also help to maintain viscosity and form emulsions.

A lift stopping mechanism controlled by a special rope fastening

The lift leveling mechanism provided in this paper is controlled by the special rope fastening. By using the lift leveling mode controlled by the rope fastening, the leveling mode of the lifting system can be changed to the braking stop of the drive system after the platform is lowered and placed on the bracket. The problem of anchorage precision and the vibration caused by elastic expansion of the rope during platform loading and unloading are effectively solved by using the supporting function of the piers. In the process of studying this problem, we simplified a heavy-duty elevator system to form a simplified model that can be used for simulation research. The device provided in this article provides a new solution for the leveling of the heavy-duty lifting system, which not only ensures the leveling accuracy of the lifting platform during loading and unloading, but also effectively reduces the impact during leveling, which has a beneficial guiding effect on this type of equipment.

Characteristic and mechanism of pollution by laser cleaning high-value vehicle parts with a complex structure in remanufacturing industry

Remanufacturing high-value vehicle parts is of substantial significance for the circular economy because it provides a second service life and reduces solid waste generation. Laser cleaning is a promising method in the remanufacturing industry owing to its high energy, precision, and efficiency. However, the pollution caused by laser cleaning remains unknown and has rarely been reported, limiting the application of this method. In this study, pollution removal and conversion using a high-energy laser were explored, and environmental life cycle and health risk assessments were conducted. The results showed that high-energy lasers might induce new organic pollutants, such as olefins, alkynes, and aldehydes. During laser cleaning, thermal elastic expansion and shock wave generation were the main mechanisms of rust removal, and evaporation and small-scope boiling were used for waste oil removal. The mean concentration of PM10 was above 7000 µg/m3 in laser rust removal, and the total concentration of volatile organic compounds (VOCs) was the highest in laser oil removal (∼ 2568 µg/m3). Particulate matter contained high amounts of Fe, Al, and Mn. An environmental life cycle assessment indicated that laser cleaning for stain removal significantly reduced the total environmental impact compared with that of traditional solvent-ultrasonic cleaning (∼ 40.0%) and sandblasting (∼ 83.3%). This study provides an environmental protection basis for increasing the use of laser cleaning in the remanufacturing industry.

Force matching and iterative Boltzmann inversion coarse grained force fields for ZIF-8.

Despite the intense activity at electronic and atomistic resolutions, coarse grained (CG) modeling of metal-organic frameworks remains largely unexplored. One of the main reasons for this is the lack of adequate CG force fields. In this work, we present iterative Boltzmann inversion and force matching (FM) force fields for modeling ZIF-8 at three different coarse grained resolutions. Their ability to reproduce structure, elastic tensor, and thermal expansion is evaluated and compared with that of MARTINI force fields considered in previous work [Alvares et al., J. Chem. Phys. 158, 194107 (2023)]. Moreover, MARTINI and FM are evaluated for their ability to depict the swing effect, a subtle phase transition ZIF-8 undergoes when loaded with guest molecules. Overall, we found that all our force fields reproduce structure reasonably well. Elastic constants and volume expansion results are analyzed, and the technical and conceptual challenges of reproducing them are explained. Force matching exhibits promising results for capturing the swing effect. This is the first time these CG methods, widely applied in polymer and biomolecule communities, are deployed to model porous solids. We highlight the challenges of fitting CG force fields for these materials.

Expansion and creep of concrete with expansive agents at variable temperature

Extensive research has shown that expansive agents can reduce engineering cracks of concrete, while temperature and creep significantly affect the ability of the expansive agent to compensate shrinkage of concrete. In order to study the expansion and creep of concrete mixed with expansive agents under variable temperature, Series of parameters of concrete mixed with MgO expansive agent (MEA) and CaO-calcium sulfoaluminate expansive agent (CEA) were tested by temperature stress testing machine (TSTM), and the elastic modulus, expansion and creep were calculated according to the maturity theory. The results showed that CEA had a larger free expansion but smaller constrained expansion compared to MEA, and the expansion energy of CEA almost completely released within 36 h of the temperature-rise stage. MEA had a smaller compressive stress creep in the temperature-rise stage and larger tensile stress creep in the cooling stage, which was beneficial to resistance to cracking. The proposed expansion kinetics model showed a remarkable level of consistency with the test results and held significant importance in guiding the application of MEA in practical engineering.