Large Deformation Characteristics Research Articles

Analysis of elastic and rheological properties of tunnel anchorage support structure under the action of seepage flow

The large deformation and strong rheological characteristics of the underground rock body under complex geological conditions have led to the failure of the support system and even the instability of tunnels from time to time. Based on the theory of groundwater seepage, the elastic solution of the mechanical model of the tunnel anchorage support system under seepage is solved, which reveals the influence of seepage on the peripheral rock and the support parameters of the anchorage support system; the viscoelastic solution is solved according to the corresponding principle of elasticity—viscoelasticity, which analyses the influence of seepage on the rheological process of the anchorage support system; and the model is simulated with the help of finite element software, which analyses the agreement and discrepancy of the numerical solution and the theoretical solution. The results show that the analytical and numerical solutions are basically consistent. This study can provide important guidance for controlling long-term stability of water-rich tunnel rocks.

Numerical Study on Large Deformation Characteristics of Tunnels Excavated in Strain-Softening Time-Dependent Rock Masses

Numerical Study on Large Deformation Characteristics of Tunnels Excavated in Strain-Softening Time-Dependent Rock Masses

Investigation of Reasonable Reserved Deformation of Deep-Buried Tunnel Excavation Based on Large Deformation Characteristics in Soft Rock

Investigation of Reasonable Reserved Deformation of Deep-Buried Tunnel Excavation Based on Large Deformation Characteristics in Soft Rock

A Numerical Investigation on the Sinkage of the Deep-Sea Mining Vehicle Based on a Modified Constitutive Soil Model

Abstract The seabed soil of the polymetallic nodule mining area is relatively thin, soft, and fluid, which will produce large deformation under external disturbance. Its undrained shear strength is related to strain-rate and strain-softening effect. It is an important engineering safety problem for the deep-sea mining vehicle (DSMV) to travel in the soft seabed, and its sinkage is a vital index affecting the traction performance. It is necessary to study the sinkage performance of the DSMV under the characteristics of large soil deformation, but there are only few existing studies. This study established a numerical model of seabed soft soil with Tresca constitutive considering strain-rate and strain-softening effects. First, a numerical simulation study was carried out on the interaction between the DSMV track plate and the seabed soil, and the influence of track plate structures on the pressure–sinkage characteristic was obtained. Then, a simplified three-dimensional model of the “PIONEER-I” DSMV was established. Under the condition of wet weight and initial vertical velocity, the influence of different initial bottoming velocities, weight, and soil parameters on the sinkage of the DSMV was obtained. An empirical prediction model of the DSMV sinkage was established based on the energy method and numerical calculation results.

Consistent Thermal Conductivities of Spring-Like Structured Polydimethylsiloxane Composites under Large Deformation.

Flexible and highly thermally conductive materials with consistent thermal conductivity (λ) during large deformation are urgently required to address the heat accumulation in flexible electronics. In this study, spring-like thermal conduction pathways of silver nanowire (S-AgNW) fabricated by 3D printing are compounded with polydimethylsiloxane (PDMS) to prepare S-AgNW/PDMS composites with excellent and consistent λ during deformation. The S-AgNW/PDMS composites exhibit a λ of 7.63W m-1 K-1 at an AgNW amount of 20 vol%, which is ≈42 times that of PDMS (0.18W m-1 K-1) and higher than that of AgNW/PDMS composites with the same amount and random dispersion of AgNW (R-AgNW/PDMS) (5.37W m-1 K-1). Variations in the λ of 20 vol% S-AgNW/PDMS composites are less than 2% under a deformation of 200% elongation, 50% compression, or 180° bending, which benefits from the large deformation characteristics of S-AgNW. The heat-transfer coefficient (0.29W cm-2 K-1) of 20 vol% S-AgNW/PDMS composites is ≈1.3 times that of the 20 vol% R-AgNW/PDMS composites, which reduces the temperature of a full-stressed central processing unit by 6.8°C compared to that using the 20 vol% R-AgNW/PDMS composites as a thermally conductive material in the central processing unit.

Liquefaction-induced large deformation method with automatic time-step mapping and interfacial interpolation improvement: Case study of the San Fernando dam

This study constructed the u-p equation for saturated soil in the meshfree global weak form within the arbitrary Lagrangian-Eulerian (ALE) framework to solve the problem of liquefaction-induced large deformation induced by strong seismic loading. The interpolation improvement in the near-interface zone was achieved using domain truncation optimization and the local nodal refinement algorithm, and the relative error of the shape function was proposed as the judgment criterion for radial basis function (RBF) field variable mapping. Finally, a high precision meshfree liquefaction-induced large deformation method (MFLLDM) with automatic time step mapping and interfacial zone interpolation improvement was established. The MFLLDM achieved the efficient dynamic updating of soil stress state and pore pressure information in space during the deformation process and more accurately depicted the localized large shear deformation characteristics of the soil in the near-interface zone. The proposed method was integrated into a custom-built large-scale finite element method (FEM) computing system (GEODYNA), based on object-oriented and super element program design technology. This enabled the efficient coupled analysis of MFLLDM in the liquefied-induced large deformation zone and FEM in the small deformation zone. Numerical consolidation examples were used to validate the accuracy, convergence, and applicability of the soil elasto-plastic model for MFLLDM. The method was then used to simulate the liquefaction damage of the San Fernando dam, which reproduced the development process of large slip deformation and high-water pressure ratio for the upstream dam slope.

Dynamic modeling of a soft robotic fish driven by dielectric elastomer based on the ANCF and IB-LBM

Dielectric elastomer (DE) is an intelligent and pliable material that exhibits significant deformation when subjected to an electric field. It possesses attributes such as remarkable strain, exceptional energy density, rapid responsiveness, and minimal weight, making it uniquely advantageous in the propulsion of bionic fish. Due to the nonlinearity and large deformation characteristics of DEs, it is challenging to accurately describe their complex deformations. The absolute nodal coordinate formulation (ANCF) possesses notable advantages in precisely depicting phenomena entailing substantial deformation and displacement. This paper focuses on the study of a bionic robotic fish driven by dielectric elastomer actuators (DEAs) based on body/caudal fin (BCF) propulsion, wherein the fish body is delineated as a laminated beam structure. By combining the ANCF higher-order beam element with the DE constitutive model and the neo-Hookean hyperelastic constitutive model, the dynamic equations of the laminated beam are derived. The interaction between the bionic fish and the fluid is effectively handled through the implementation of the immersed boundary - lattice Boltzmann method (IB-LBM), and by combining ANCF with IB-LBM, the dynamic responses of the fish under voltage excitation and fluid resistance are simulated and analyzed. This study would contribute to the exploration of the intricate mechanism behind the substantial amplitude motion of bionic robotic fish driven by DEAs, yielding valuable insights for further research endeavors.

Large deformation characteristics and the countermeasures of a deep-buried tunnel in layered shale under groundwater

Deep-buried tunnels constructed through layered soft rocks undergo large deformation, which threatens their safety and leads to construction delay. When a soft rock tunnel is excavated below the water table, the rock mass will deteriorate due to the presence of groundwater, aggravating the large deformation issue. In this work, the Baozhen tunnel excavated in layered carbonaceous shale was taken as a case study to investigate the mechanical behavior and support countermeasures of deep-buried tunnels with a high geostress considering the effect of groundwater. First, laboratory tests were performed to study the groundwater effect on the mechanical properties of the shale. Subsequently, the geological and large deformation characteristics of selected study areas using the original support scheme were analyzed. Using the tested constitutive parameters combined with the field-monitored deformation, a UDEC numerical model was established to investigate the tunnel deformation behavior under different bedding angles, groundwater depths, and shear stresses. Finally, the optimized support scheme was verified through numerical and on-site monitoring results. The tunnel responses at three typical monitoring cross-sections, such as the deformation distribution and normal pressures acting on the primary support and secondary lining, were compared to investigate the effect of groundwater and the optimized support scheme on the tunnel responses. An asymmetric large deformation was induced by the combined action of the soft layered rock and shearing action under the effect of groundwater. The groundwater reduced the rock strength and increased the tunnel deformation, and it also strengthened the unsymmetrical loading effect, which was reflected in the distributions of the tunnel deformation and support pressures. As a countermeasure, asymmetrically arranged rockbolts could help reduce the full-ring tunnel deformation and support pressure by 50.3 % and 22 %, respectively, which could also alleviate the unsymmetrical loading effect, thus enhancing the synergistic performance of the support structures. The insights gained in this study can help improve the effectiveness of countermeasures against layered rock instability while tunneling in the presence of groundwater.

Numerical implementation of the hypoplastic model for SPH analysis of soil structure development in extremely large deformation

The extremely large deformation of soil is a significant challenge due to the dynamic changes in soil structure, but it is poorly understood owing to inadequate effective numerical methods. This paper presents a numerical method for analysing the responses of sand-like granular soil undergoing extremely large deformation. The proposed method utilizes the Smoothed Particle Hydrodynamics (SPH) technique, which is a meshfree particle-based approach capable of circumventing the computational difficulties associated with mesh distortion. The Gudehus-Bauer (G-B) hypoplastic model, which can capture the pressure- and density- dependent mechanical behaviour of granular soil, is implemented into the in-house developed SPH code. Concerning the characteristics of large deformation, the Green-Naghdi rate is applied in this study to achieve objective stress integration. An adaptive explicit stress integration scheme, termed Modified Euler automatic Substepping with Error Control (M-E-SEC) is utilized to handle the time integration of the SPH equation system. Additionally, a stability correction method is introduced to suppress the breakdown problem that occurs at low-stress states. The effectiveness of the proposed method is validated by experimental data. Furthermore, several numerical examples are presented to elucidate the evolution of shear band structures in granular soils subject to extremely large deformation levels.

Modeling of temperature effect on electromechanical properties of dielectric elastomer minimum energy structures

Due to the characteristics of large deformation and fast response to excitation voltage, dielectric elastomer minimum energy structures (DEMES) can actively adjust its shape to adapt to the complex environments, which is a research hotspot in the field of soft robotics. The electromechanical properties of DEMES are sensitive to temperature variation. However, the analysis of the effect of temperature on the viscoelastic dynamic behavior of DEMES is incomplete in existing studies. In this paper, an analytical framework for investigating the electromechanical performances of DEMES actuator is presented. By introducing the effects of temperature on the dielectric constant and elastic modulus of DEMES actuator, the governing equations of motion for the underlying non-conservative system affected by temperature are established by combining the DE viscoelastic rheological model and the Euler-Lagrange equation. The proposed model is used for building insights into the effect of temperature on the stiffness, equilibrium state, actuation range and the evolution law of the dynamic response under the DC and AC excitations of DEMES. The results show that a significant enhancement in the equilibrium angle attained by the structure with the improving of the temperature is observed, indicating a favorable impact of ambient temperature. Phase paths and Poincaré maps are presented for assessing the temperature effect on the stability and periodicity of the nonlinear oscillations. The frequency responses of the actuator for the AC loads indicate that a suitable temperature can significantly improve the dynamic performance and stability of DEMES actuator. The proposed analytical model and results presented in this study can provide guidance for the design and development of DEMES based soft robot subjected to harsh environments.

Study on Large Deformation Characteristics and Secondary Lining Supporting Time of Tunnels in Carbonaceous Schist Stratum under High Geo-Stress

The deformation characteristics and the timing for secondary lining support in high geo-stress soft rock tunnels have drawn significant attention. In carbonaceous shale formations, tunnel construction deformations are very pronounced under construction disturbances due to the development of joints, dense fractures, and poor interlayer bonding. With the Xishuangbanna tunnel as our research backdrop, this study meticulously analyzed the deformation patterns and characteristics inherent to high geo-stress tunnels constructed within carbonaceous schist formations. Employing a comprehensive approach involving full displacement analysis and on-site construction mechanics testing, we utilized the displacement release rate and structural safety factors as key indicators to determine the secondary lining supporting time. Employing this innovative approach, we successfully identified the ideal junctures for implementing secondary lining support in tunnels excavated through high geo-stress carbonaceous schist. The research findings indicate that the primary damage modes in high geo-stress carbonaceous schist tunnels are initial support failure and extensive early support deformation. These vulnerabilities are primarily attributed to weak and fragmented strata, elevated ground stress levels, and inadequate support strength. During the early stages of tunnel construction, substantial deformations are observed, exhibiting high rates of change. Horizontal convergence, notably, significantly surpasses the settlement at the tunnel’s crown. When employing the three-bench method for construction, the deformation occurring before the excavation of the middle bench contributes the most to the total deformation monitored, whereas the deformation generated after the excavation of the inverted arch constitutes a minor proportion. The tunnel’s crown and invert experience tension while the secondary lining undergoes compression. The internal forces are most significant at the tunnel’s hance and knee, with the left tunnel knee being the weakest section of the secondary lining. The findings of our study are poised to guide the design and execution of tunnels constructed within high geo-stress carbonaceous schist formations.

Recent progress on underwater soft robots: adhesion, grabbing, actuating, and sensing.

The research on biomimetic robots, especially soft robots with flexible materials as the main structure, is constantly being explored. It integrates multi-disciplinary content, such as bionics, material science, mechatronics engineering, and control theory, and belongs to the cross-disciplinary field related to mechanical bionics and biological manufacturing. With the continuous development of various related disciplines, this area has become a hot research field. Particularly with the development of practical technologies such as 3D printing technology, shape memory alloy, piezoelectric materials, and hydrogels at the present stage, the functions and forms of soft robots are constantly being further developed, and a variety of new soft robots keep emerging. Soft robots, combined with their own materials or structural characteristics of large deformation, have almost unlimited degrees of freedom (DoF) compared with rigid robots, which also provide a more reliable structural basis for soft robots to adapt to the natural environment. Therefore, soft robots will have extremely strong adaptability in some special conditions. As a type of robot made of flexible materials, the changeable pose structure of soft robots is especially suitable for the large application environment of the ocean. Soft robots working underwater can better mimic the movement characteristics of marine life in the hope of achieving more complex underwater tasks. The main focus of this paper is to classify different types of underwater organisms according to their common motion modes, focusing on the achievements of some bionic mechanisms in different functional fields that have imitated various motion modes underwater in recent years (e.g., the underwater sucking glove, the underwater Gripper, and the self-powered soft robot). The development of various task types (e.g., grasping, adhesive, driving or swimming, and sensing functions) and mechanism realization forms of the underwater soft robot are described based on this article.

Research on Deformation and Loose Zone Characteristics of Large Cross Section Tunnel in High Geo-Stress Soft Rock

In constructing high-geo-stress soft rock tunnels, the major deformation disaster of the surrounding rock has always been the main problem faced during construction. The research on the deformation and loose zone characteristics of large deformation tunnels has positive significance for the safe and rapid construction of tunnels. Therefore, based on the Yuntunpu large deformation tunnel, this article first analyzes the geological and deformation characteristics of the tunnel site area in response to the problem of high-geo-stress soft rock large deformation. Subsequently, on-site testing and analysis were conducted on the loose zone characteristics of four tunnel sections. Finally, based on the comprehensive analysis of tunnel deformation and loose zone characteristics, the causes of large deformation in the tunnel are analyzed. The results indicate that the large deformation characteristics of the Yuntunpu Tunnel are mainly manifested as a large initial deformation rate of the surrounding rock, a short self-stabilization time of the surrounding rock, a large cumulative deformation amount, and a long deformation duration. The Yuntunpu Tunnel is influenced by the grade and structure of the surrounding rock, with a loosening zone ranging from 12 to 14 m, and the wave velocity variation characteristics exhibited by different grades of surrounding rock vary greatly. Adopting collaborative active control of long and short anchor rods is recommended to limit the continued development of loose zones and the deformation of surrounding rocks. The large deformation of tunnels is mainly affected by high geo-stress, formation lithology, geological structure, engineering disturbance, and groundwater. Among them, high geo-stress and formation lithology are the decisive and important factors for the occurrence of major deformation disasters in the tunnel.

A Torsional Negative Poisson’s Ratio Structure: Dynamics and Energy Absorption Performance

The crash box’s internal structure can be designed to absorb more energy in a significant way. Using the finite element method, this paper investigates a structure with a negative Poisson ratio and a self-torsion effect. The arrangement and combination of eight structures have a torsional Poisson ratio that is negative. The optimal energy absorption of LCHC-B structures, as determined by simulation analysis, results in an excellent performance. Due to structural asymmetry, the LCHC-B structure has large deformation characteristics and self-torsion, making the structure’s displacement greater than that of the conventional negative Poisson ratio structure and exhibiting excellent energy absorption properties.

High ductility and corrosion resistance chromium gradient stainless steel for fuel cell bipolar plates fabricated via laser powder bed fusion

Stainless steel sheets with a higher Cr content feature better corrosion resistance but lower ductility and formability, leading to the trade-off of performance and fabrication complexity/cost in many industrial scenarios, such as fuel cell bipolar plates and microreactors. To address that, thin stainless steel (SS) plates with a Cr gradient composition are fabricated with laser powder bed fusion technology in this work. Combining a Cr-rich (30 wt% Cr content) stainless steel composition with SS 316 L along the thickness direction using a gradient transition layer, the prepared gradient sheet achieves an elongation higher than 45%, which far exceeds the 19.9 ± 1.1% of the freestanding Cr-rich composition. Furthermore, detailed mechanical tests and microstructure characterizations are performed to analyze the mechanism for significant ductility improvement. The restraining function of high ductility composition promotes the multi-axial stress state in the low ductility Cr-rich composition and gradient layers, eventually activating more slip systems and dislocation entanglement. The resulting extra-hardening is accompanied by a significant increase in plastic deformation, leading to the fracture morphology with more pronounced large deformation characteristics.

Preface

The 2023 2nd International Conference on Materials Engineering and Applied Mechanics (ICMEAAE 2023), held from March 24th to 26th, 2023 in Kaifeng, China, is a premier academic conference on materials engineering and applied mechanics for research groups working on related fields. It allows researchers to share their experiences with other groups from all over the world by presenting scientific work and potential innovations in this research area and also in the social events promoting informal get togethers.The work covers a broad range, including topics on Materials Science and Engineering Nanomaterials, Electronic and Magnetic Materials, Materials Failure and Protection, Vibration Science, Wave propagation, etc. Also, the Conference is intended to give students and research groups the opportunity to learn more about materials engineering and applied mechanics as an important tool in their applications and development.The Conference is designed to showcase cutting-edge research and accomplishments, and to enrich the educational and industrial experience in this field. It also represents a unique opportunity to meet colleagues and friends, exchanging ideas, and learning about new developments and best practice, while working to advance the understanding of the knowledge base that we will collectively draw upon in the years ahead to meet future challenges. Participants will attend presentations by scholars representing both institutes and academia.The ICMEAAE 2023 Proceedings include about 100 papers selected via a peer review process. The Conference Program features keynote speeches by eight leading scholars and many sessions for regular paper oral presentations, attracting about 150 participants. Associate Professor Zishun Liu from Xi’an Jiaotong University, China gave a speech on the title Advances in Mechanics of Soft materials – New Smart Hydrogels. Hydrogels are widely used in flexible electronics and biomedicine fields because of their excellent large deformation characteristics and very good biocompatibility. In this presentation, he discussed some paradoxes in the description of mechanical properties and fracture toughness of hydrogels, and then the recent advances about hydrogel. It triggered heated discussing atmosphere in the Conference.In making this Conference possible, we want to acknowledge our deep appreciation for all our sponsors and supporters. And we would like to extend an enthusiastic round of thanks to all authors for their excellent contributions; to all the session Chairs for their effort and enthusiasm; and to all the Technical Program Committee members and referees for their time and expertise in the paper review. Special thanks go to the staff of Journal of Physics: Conference Series for their time and outstanding publishing work.The Committee of ICMEAAE 2023List of Committee Member is avilable in this pdf.

Parametric analysis for the large deformation characteristics of unstable slopes with linearly increasing soil strength by the random material point method

Soils often exhibit spatial variability with nonstationarity, which has not yet been studied in the context of postfailure analysis of slopes. In this study, the random material point method is adopted to investigate the influence of nonstationarity on the large deformation characteristics of a slope with spatially variable undrained shear strength (Su). The nonstationarity has significant influences on the mean and standard deviation of the large deformation characteristics, where ignoring the nonstationarity can lead to higher mean and standard deviation values. In addition, when the nonstationarity is insignificant with a small increase in the rate of the soil strength, the model boundary can significantly affect the standard deviation of influence and run-out distances, but the influence is slight on those of the volume of the sliding mass. In addition, the mean and standard deviation of the large deformation characteristics increase with a higher coefficient of variation of Su. This study reveals that the nonstationarity of soil spatial variability can influence the failure mechanism in the failure initiation stage and thus the volume of the sliding mass, which controls the kinetic energy of the sliding mass in the postfailure stage and affects the influence and run-out distances.

Investigation of dynamic response of drilling parameters and deformation characteristics of coal around borehole during multi-stage reaming in tectonic coal

Tectonic coal refers to the coal with varying degrees of brittle fracture or ductile deformation under the action of one or multi-period tectonic stresses, showing the characteristics of low mechanical strength, weak cohesion and large deformation. Therefore, drilling in tectonic coal is easy to cause the aperture shrinkage or closure due to the poor anti-deformation capability. Enlarging the initial borehole can effectively increase the borehole diameter and reduce the risk of pipe jamming and burying without changing the borehole structure. In order to investigate the dynamic evolution characteristics of drilling parameters in the process of drilling and reaming in tectonic coal, a self-designed drilling experimental system that can monitor drilling parameters in real time was used in this study. Additionally, the acoustic emission (AE) response and borehole wall strain were observed to study the coal-breaking and the deformation characteristics of coal around borehole. The results demonstrate that the drilling rate and drilling torque increase sequentially in the initial drilling, primary reaming and secondary reaming stages. The magnitude of drilling rate is affected by both drilling thrust and rotational speed, whereas drilling torque is mainly affected by drilling thrust. The intensity of AE phenomena increases gradually at different stages of the borehole formation, which means that the drilling efficiency is improved and more strain energy is accumulated in the coal around the borehole during reaming. The borehole wall strain effectively reflects the convergence deformation of borehole wall, that is, the larger the borehole diameter, the greater the deformation of the borehole wall. The deformation of borehole is mainly affected by the redistribution of stress in the coal body, rather than the drilling parameters.

Modeling of a Soft Actuator With a Semicircular Cross Section Under Gravity and External Load

Compared to rigid robotic actuators, soft actuators based on fibre-reinforced elastomeric actuators (FREAs) have great potential for use in exploring complex terrain, medical operations, and flexible capture of targets. However, it is still challenging to model the mechanical behaviour of soft actuators because of the large deformation and nonlinear characteristics of elastic materials. This paper proposes an analytical model to predict the shape of a soft actuator to better describe the relationship between its deformation and input pressure, gravity, and other external forces. We first derive the relationship between soft actuator deformation and pressure using volume maximisation and the principle of virtual work. We further use Euler–Bernoulli beam theory to investigate the influence of self-gravity and external forces on the soft actuator configuration. The model is verified by fabricating a soft actuator prototype via mold casting. Finally, we perform a series of experiments to evaluate the accuracy of our proposed model. The longest total time to solve the model is 0.035 s. Experimental results show that the model's maximum error rate is between 2.89% and 9.75%. This indicates that the model can effectively predicts the deformation of soft actuators considering gravity and other external forces.

Study on slope stability analysis and large deformation characteristics of failure based on SPH method

Study on slope stability analysis and large deformation characteristics of failure based on SPH method