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A 5-degree-of-freedom continuum manipulator is designed and implemented to improve the flexible positioning ability of the continuum mechanism in applications such as interactivity operations, light object grabbing, and human-machine collaboration. In the design process, by introducing a two-segment constant curvature model, the distribution of degrees of freedom on the mechanism is explained geometrically by the method of twist. Coupling two stretchable parallel modules in series, a two-segment structure is formed for curving and each segment has two degrees of freedom in bending and one degree of freedom in stretching, thereby giving 5 degrees of freedom to the end-effector. Concentrating on the dynamic performance of the manipulator, an electromechanical system platform is built as a prototype. The experiments show that the structure realizes the control of the end-effector during large deformation of the manipulator, and is able to achieve extreme pose in 2 s with an approximation positioning error of 2% of the nominal arm length.

Rock bolting technique is an important reinforcement measure in the geotechnical engineering practice. New rock bolts have been continuously emerging through the development of rock supporting technology. Complex conditions, such as high crustal stress, extremely soft rock, and strong mining disturbance often occur in the deep mining, resulting in large deformation of the surrounding rock masses. Since the deformation of traditional rock bolts is generally below 200 mm, failure often occurs to the rock bolts because of insufficient deformability. To effectively control the large deformation of surrounding rock masses caused by complex conditions, it is necessary to develop large deformation rock bolts with high constant resistance, also called energy-absorbing bolts. This paper systematically reviews the development of large deformation rock bolts and the structure, energy absorption mechanism, anchorage performance, and mechanical properties of several typical large deformation rock bolts. The advantages and disadvantages of existing large deformation rock bolts are compared and the concept of constant resistance large deformation support is introduced.

The stability of the surrounding rocks of large underground powerhouses is always emphasized during the construction process, especially in large-scale underground projects under construction, such as the Baihetan hydropower station in China. According to field investigations, numerical simulations and monitoring data analysis, we present a comparative analysis of the deformation and failure characteristics of the surrounding rocks of underground powerhouses on the left and right banks of the Baihetan hydropower station. The failure characteristics and deformation magnitude of the underground powerhouses on the left and right banks are quite different. Under the disadvantageous condition where the maximum principal stress intersects the axis of the powerhouse at a large angle, the left bank underground powerhouse shows prominent stress-controlled failure characteristics such as spalling, slack collapse and concrete cracking. Although the maximum principal stress is in the favorable condition which intersects the right bank powerhouse at a small angle, the relatively high intermediate principal stress with an angle subvertical to the right bank powerhouse plays an essential role in its deformation and failure, indicating that the influence of high intermediate principal stress cannot be ignored. In addition, structural plane-controlled failure and large deformation are also more evident on the right bank due to the extensive distribution of weak structural planes and complex surrounding rock properties.

Taking the Jiangluling Carbonaceous Shale Tunnel as an example, this study aims to investigate the mechanism of large deformation and design construction technology of carbonaceous shale tunnels. Using theoretical analysis and comparative analysis of numerical simulation and field measured data, the mechanism, mechanical properties, and causes of large squeezing deformation of the Jiangluling Tunnel were analyzed. The study results are as follows: 1) Six failure modes of the support structure can be generated due to the large deformation of the surrounding rocks during the construction of Jiangluling Carbonaceous Shale Tunnel; 2) The causes of large deformation during the construction can be divided into internal and external causes; 3) The deformation degree of the surrounding rock of Jiangluling Carbonaceous Shale Tunnel increases with the burial depth in an approximately linear manner. Under deep-buried conditions, horizontal convergence is more severe than vault settlement in carbonaceous shale tunnels; 4) The deformation of the construction cavern of the Jiangluling Carbonaceous Shale Tunnel typically includes the displacement before tunnel face excavation, tunnel face deformation, and deformation behind the tunnel face. The advance displacement accounts for 30.73% of the total displacement. The influence range of advance displacement is 1-1.2D in front of the tunnel face. These results can provide a reference for the design and construction of carbonaceous shale tunnels.

In this study, the variational method concerning displacement components is applied to solve the large deformation problem of a thin cylindrical shell with its four sides fully fixed and under uniformly distributed loads, in which the material that constitutes the shell has a bimodular effect, in comparison to traditional materials, that is, the material will present different moduli of elasticity when it is in tension and compression. For the purpose of the use of the displacement variational method, the physical equations on the bimodular material model and the geometrical equation under large deformation are derived first. Thereafter, the total strain potential energy is expressed in terms of the displacement component, thus bringing the possibilities for the classical Ritz method. Finally, the relationship between load and central deflection is obtained, which is validated with the numerical simulation, and the jumping phenomenon of thin cylindrical shell with a bimodular effect is analyzed. The results indicate that the bimodular effect will change the stiffness of the shell, thus resulting in the corresponding change in the deformation magnitude. When the shell is relatively thin, the bimodular effect will influence the occurrence of the jumping phenomenon of the cylindrical shell. [ABSTRACT FROM AUTHOR]

The yielding support has proven to be one of the most effective measures to control the large deformation of the tunnel, as it could well stabilize tunnel support structure by releasing the deformation energy in the surrounding rock and exerting the self-supporting ability of the surrounding rock. To explore the damage mechanical behavior of shotcrete linings with yielding supports in large-deformation tunnels, an elastic–plastic damage model of concrete was developed, and a numerical method for simulating the yielding support based on the double-node beam element and interface element was proposed. Then, the influences of the position and resistance of the yielding element on the behaviors of shotcrete lining were analyzed and discussed. The results indicate that the position and resistance of the yielding element have a significant effect on the distribution of damage, principal stress, axial force, and bending moment of the lining. In the tunnel dominated by horizontal deformation, the yielding structure with constant resistance symmetrically arranged at the waist of the tunnel sidewall has the best yielding effect. The damage and maximum axial force are minimal, and the maximum bending moment is relatively large but lower than the maximum bending moment that the lining structure can bear. Assuming that the yielding element position stays the same, the maximum lining axial force rises with increasing yielding resistance, the maximum bending moment shows an initially upward and subsequently downward trend as the yielding resistance rises, and the maximum damage shows a trend of first declining and then growing as the yielding resistance rises. It is also found that the resistance of the yielding component should be controlled within a reasonable range, neither too small nor too large, for the lining to be in good working condition. Highlights: A new elastoplastic damage model was developed to describe the post-peak strain-softening behavior of concrete. A numerical realization approach for yielding support mechanical behavior was proposed. The mechanical behaviors of shotcrete lining with yielding support were numerically analyzed. [ABSTRACT FROM AUTHOR]

Deformation measurement is crucial for understanding the mechanical responses of rock masses; however, full-scale tests on rock masses are difficult and costly. With the development of 3D printing technology, small-scale tests provide a promising solution. Nevertheless, traditional DIC codes usually fail due to the existence of discontinuities such as cracks and shear bonds, and the correlation also rapidly drops when large deformation occurs, which is an obstacle for further application of the DIC in small-scale tests on rock. In this work, a discrete digital image correlation (DDIC), based on the principle of DIC and the discrete finite element method (DFEM), is introduced to address discontinuities and large deformations. The triangular mesh with shrunken internal nodes was selected to address the discontinuities. A scheme of updating the reference image based on the preset threshold was employed to solve the decorrelation caused by large deformation. The rigid rotation of the strain field was removed by introducing polar decomposition in DDIC. The effectiveness and reliability of the proposed DIC were verified through several small-scale tests including dislocation, separation, and large deformation. The results showed that the updated triangular mesh can adequately trace and adapt to the discontinuous deformation and large deformation of specimen, while correlation coefficients can still fall within a relatively high confidence interval. Overall, DDIC with small-scale tests might provide a promising solution to the difficulty of preparing large specimens in rock mechanics studies and provide measurement data for the verification and calibration of discontinuous numerical methods. Highlights: A novel digital image correlation method is proposed to address the discontinuous deformation. Combined with an automatic updating scheme, the subset distortion caused by large deformation is solved. The objective strain fields can be obtained by introducing polar decomposition. The method provides measurement data for the verification and calibration of numerical tools. [ABSTRACT FROM AUTHOR]

This work proposes a novel model and numerical formulation for lubricated contact problems describing the mutual interaction between two deformable 3D solid bodies and an interposed fluid film. The solid bodies are consistently described based on nonlinear continuum mechanics allowing for finite deformations and arbitrary constitutive laws. The fluid film is modelled as a quasi-2D flow problem governed by the (thickness-)averaged Reynolds equation. In contrast to existing approaches, the proposed model accounts for the co-existence of frictional contact tractions and hydrodynamic fluid tractions at every local point on the contact surface of the interacting bodies and covers the entire range of lubrication in one unified modelling framework with smooth transition between these different regimes. From a physical point of view, this approach can be considered as a model for the elastic deformation of asperities on the lubricated contact surfaces. The finite element method is applied for spatial discretization of the 3D solid-mechanical problems and the 2D interface effects, consisting of the averaged Reynolds equation governing the fluid film and the non-penetration constraint of the mechanical contact problem. A consistent and accurate model behavior is demonstrated by studying several challenging benchmark test cases. [ABSTRACT FROM AUTHOR]

The large‐deformation mechanics and multiphysics of continuous or fracturing partially saturated porous media under static and dynamic loads are significant in engineering and science. This article is devoted to a computational coupled large‐deformation periporomechanics paradigm assuming passive air pressure for modeling dynamic failure and fracturing in variably saturated porous media. The coupled governing equations for bulk and fracture material points are formulated in the current/deformed configuration through the updated Lagrangian–Eulerian framework. It is assumed that the horizon of a mixed material point remains spherical and its neighbor points are determined in the current configuration. As a significant contribution, the mixed interface/phreatic material points near the phreatic line are explicitly considered for modeling the transition from partial to full saturation (vice versa) through the mixed peridynamic state concept. We have formulated the coupled constitutive correspondence principle and stabilization scheme in the updated Lagrangian–Eulerian framework for bulk and interface points. We numerically implement the coupled large deformation periporomechanics through a fully implicit fractional‐step algorithm in time and a hybrid updated Lagrangian–Eulerian meshfree method in space. Numerical examples are presented to validate the implemented stabilized computational coupled large‐deformation periporomechanics and demonstrate its efficacy and robustness in modeling dynamic failure and fracturing in variably saturated porous media. [ABSTRACT FROM AUTHOR]

A theoretical and numerical model is developed to describe the growth of Saccharomyces cerevisiae yeasts. This kind of cells is considered here as an axisymmetrical and deformable structure, the inner surface of which is continuously acted upon by a high turgor pressure. Due to the small ratio between the cellwall thickness and the cell radius, a structural shell approach is used. Moreover, the finite strain range is assumed because of the soft nature of these cells. The adopted kinematics is herein based on the multiplicative decomposition of the deformation gradient into an elastic part Fe and an irreversible part related to the growth Fg, i.e. F = FeFg. The reversible response is described using an hyperelastic model of the Ogden type. In accordance with continuum thermodynamics requirements, a criterion is introduced to control the evolution of the growth phenomenon. In this latter two parameters are involved: a growth stress-like threshold, and a growth characteristic time. Embedded within the finite element framework, an illustrative example shows the growth phenomenon of spherical cells going from yeast bud emergence to the step just before cell division. A parametric study highlights the influence of the above mentioned parameters on the cell responses. [ABSTRACT FROM AUTHOR]

Because of the effect of bedding planes, inaccuracy deformation prediction for thin-layered rock often results in severe damage to the tunnel support in high in situ stress zone. For deformation prediction of layered rock, a series of numerical simulations using a continuum-interface numerical model were conducted to investigate the influences of the bedding planes on tunnel deformation. The feasibility of the numerical model is first verified by the comparisons of deformation and failure behaviors of layered rock between numerical results and field observations. Then, according to the numerical results, a deformation prediction equation considering effect of bedding planes was proposed for layered carbonaceous slates. The application of proposed deformation prediction equation showed that when the bedded thickness exceeds 0.05 m, the relative errors between the prediction deformation and observed deformation are less than 10%, which can satisfy the requirement of engineering applications. While, when the bedded thickness is less than 0.05 m, the proposed prediction equation cannot be used directly due to underestimation of the deformation of layered rock. [ABSTRACT FROM AUTHOR]

• A complex variable EFG method for hyperelastic large deformation under non-conservative loads was proposed. • Deformation and stress of hyperelastic materials under non-conservative loads were analysed. • The approximation function of the displacement field was established by the complex variable moving least-squares method. • The complex variable EFG method has a great advantage in efficiency and accuracy than other methods. The finite element method is extremely popular in almost all fields of engineering and scientific research due to its powerful and accessible industrial software for computational modelling. However, alternatives including the meshless methods, have received increasing attention on the large deformation problems of hyperelastic materials that need to avoid mesh distortion. In this paper, based on the complex variable moving least-squares approximation, the complex variable element-free Galerkin (CVEFG) method for the large deformation problem of hyperelastic materials under non-conservative loads is established. In the present method, the Newton-Raphson method is used for solving the nonlinear equations. The algorithm for hyperelastic large deformation problems under non-conservative loads are established. Three numerical examples are used to verify the effectiveness of the CVEFG method in this paper. Numerical results show that the solution obtained using the CVEFG method is closer to that obtained by ABAQUS and is more efficient than the element-free Galerkin method. [ABSTRACT FROM AUTHOR]

This paper proposes a multisize discrete solid-element method (MDSEM) for continua based on the discrete solid-element method (DSEM). The arrangement of spherical elements and the setting criteria of springs between spherical elements are established in MDSEM. The spring stiffness is deduced based on the principle of energy conservation, and the relationship between spring stiffness and elastic constants is established. The proposed physical model of MDSEM is able to connect spherical elements of two different radiuses, while the radiuses of spherical elements in DSEM are the same. MDSEM is proven to be an effective method for analyzing the mechanical behavior of continuum structures, as it is able to reduce the number of spherical elements and connections and improve calculation efficiency. Examples are presented to discuss the effect of direction of the force transmission path and the location of the transition region on simulation results. The effect of direction of force transmission path is not significant, but the location of the transition region has an effect. The larger the proportion of the region of the small spherical elements in the MDSEM model, the more accurate the calculation. [ABSTRACT FROM AUTHOR]

Municipal sludge is a sedimentation waste produced during the wastewater process in sewage treatment plants. Among recent studies, pilot and field tests showed that chemical conditioning combined with vacuum preloading can effectively treat municipal sludge. To further understand the drainage and consolidation characteristics of the conditioning sludge during vacuum preloading, a large deformation nonlinear numerical simulation model based on the equal strain condition was developed to simulate and analyze the pilot and field tests, whereas the simulation results were not satisfactory. The results of the numerical analysis of the pilot test showed that the predicted consolidation degree was greater than that measured by the field tests, which is attributed to the relatively low permeability layer formed during the preloading process of the prefabricated vertical drain. To better reflect the consolidation process of the conditioned sludge, a simplified analysis method considering the low permeability layer around the prefabricated vertical drain was proposed. The initial permeability coefficient of the low permeability layer is determined via numerical simulations using finite difference method. The predicted settlement curve was in good agreement with the measured results, which indicated that the numerical simulation based on the equal strain condition considering the relatively low permeability layer can better analyze the consolidation process of ferric chloride-conditioning sludge with vacuum preloading. [ABSTRACT FROM AUTHOR]

Copyright of Tunnel Construction / Suidao Jianshe (Zhong-Yingwen Ban) is the property of Tunnel Construction Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this article, a large deformation analysis of a flexible manipulator is examined by using the discrete time transfer matrix method. Since this robotic analysis is very demanding in terms of both computation time and memory usage, the main goal is to reduce the computational complexity compared to the conventional algorithm. In this study, the proposed model is validated with Euler–Bernoulli beam and a corresponding ADAMS model. A planar robotic arm in the presence of links and joints flexibility is studied. It concludes that the theoretical formulation attributes for large flexible multibody systems and practical robotic application. [ABSTRACT FROM AUTHOR]

The effect of particle volume fraction, size, and shape on the indentation behavior of particulate composites is investigated using coupled FE-EFG approach. A systematic approach is presented where the particles are modeled only in a small region under the indenter and the homogenized properties are assigned to the remaining region. Equivalent properties are determined using RVE analysis. Von-Mises criterion along-with updated Lagrangian approach is employed to capture elastoplastic large deformation behavior. Node-to-segment contact algorithm is adopted to model the contact behavior between indenter and matrix. Results in-terms of residual von-Mises stress, equivalent plastic strain, and deformed surface profile are presented. [ABSTRACT FROM AUTHOR]

Because of extensive industrial applications of polymers, several continuum and material science studies have focused on the polymers' viscohyperelasticity characterization. Although finite element methods have powerful ability in simulating complex materials' mechanical behavior, involve high computational costs. Therefore in this article mechanical responses of polymeric viscohyperelastic materials are studied by examining simultaneous extension and torsion of a cylinder thorough proposing new semi-analytical solutions. A comparison between the results of this method and finite element ones reveals the efficiency of proposed solutions in viscohyperelastic materials' parameter calibration and geometrical parameters' change on time-dependent large deformations, under combined loading conditions. [ABSTRACT FROM AUTHOR]

In this paper, an annular/circular plate made of hyperelastic material and considering the viscoelastic property was investigated based on a novel nonlinear elasticity theory. A new approach for hyperelastic materials in conjunction with the Kelvin–Voigt scheme is employed to obtain the structure's large deformation under uniform transverse loading. The constitutive equations were extracted using the energy method. The derived partial differential time-dependent equations have been solved via the semi-analytical polynomial method (SAPM). The obtained results have been validated by ABAQUS software and the available paper. In consequence, a good agreement between the results was observed. Finally, several affecting parameters on the analysis have been attended to and studied, such as the nonlinear elasticity analysis, the boundary conditions, loading, and the material's viscosity. It can be possible to obtain the needed time for achieving the final deformation of the structure based on the applied analysis in this research. [ABSTRACT FROM AUTHOR]

Soil flow is involved in many earth surface processes such as debris flows and landslides. It is a very challenging task to model this large deformational phenomenon because of the extreme change in material configurations and properties when soil flows. Most of the existing models require a two-dimensional (2D) simplification of actual systems, which are however three-dimensional (3D). To overcome this issue, we develop a novel 3D particle finite element method (PFEM) for direct simulation of complex soil flows in 3D space. Our PFEM model implemented in a fully implicit solution framework based on a generalised Hellinger–Reissner variational principle permits the use of a large time step without compromising the numerical stability. A mixed quadratic-linear element is used to avoid volumetric locking issues and ensure computational accuracy. The correctness and robustness of our 3D PFEM formulation for modelling large deformational soil flow problems are demonstrated by a series of benchmarks against analytical or independent numerical solutions. Our model can serve as an effective tool to support the assessment of catastrophic soil slope failures and subsequent runout behaviours. [ABSTRACT FROM AUTHOR]

At present, the influence of excavation on adjacent existing tunnels mainly focuses on the deformation and stress changes of tunnels, and there is still a lack of in-depth understanding of the failure modes and mechanism of excavation under the condition of adjacent tunnels. The failure modes of excavation adjacent to a tunnel at different calculation steps under different tunnel buried depths, different horizontal distances between tunnel and diaphragm wall and different buried depth of diaphragm wall are studied. The failure mechanism and excavation steps that are prone to damage are investigated. Analyses are put on the failure modes, the failure mechanism and the excavation steps that are prone to failure. The research results show that the potential failure surface can be divided into three forms:linear failure surface, arc-shaped failure surface and U-shaped failure surface. With the excavation of basement and the construction of internal supports, the shear zone gradually becomes a deep shear zone connecting the wall toe, and the intersection with the tunnel gradually shifts down from the right shoulder to the right waist or the lower right side near the waist. The damage of the excavation is likely to occur when the internal support is not set after excavation and the internal support is set after excavation to the bottom of the pit. [ABSTRACT FROM AUTHOR]

A finite-strain homogenization creep model for composite fuels under irradiation conditions is developed and verified, with the irradiation creep strains of the fuel particles and matrix correlated to the macroscale creep responses, excluding the contributions of volumetric strain induced by the irradiation swelling deformations of fuel particles. A finite element (FE) modeling method for uniaxial tensile creep tests is established with the irradiation effects of nuclear materials taken into account. The proposed models and simulation strategy are numerically implemented to a kind of composite nuclear fuel, and the predicted mesoscale creep behaviors and the macroscale creep responses are investigated. The research results indicate that: (1) the macroscale creep responses and the mesoscale stress and strain fields are all greatly affected by the irradiation swelling of fuel particles, owing to the strengthened mechanical interactions between the fuel particles and the matrix. (2) The effective creep rates for a certain case are approximately two constants before and after the critical fission density, which results from the accelerated fission gas swelling after fuel grain recrystallization, and the effects of macroscale tensile stress will be more enhanced at higher temperatures. (3) The macroscale creep contributions from the fuel particles and matrix depend mainly on the current volume fractions varying with fission density. (4) As a function of the macroscale stress, temperature, initial particle volume fraction and particle fission rate, a multi-variable mathematical model for effective creep rates is fitted out for the considered composite fuels, which matches well with the FE predictions. This study supplies important theoretical models and research methods for the multi-scale creep behaviors of various composite fuels and provides a basis for simulation of the thermal–mechanical behavior in related composite fuel elements and assemblies. [ABSTRACT FROM AUTHOR]

Flexible electrothermal heaters have a great potential for applications of warm‐keeping and thermotherapy. However, those common electrothermal heaters are so sensitive to strain that they are hard to resistant to deformation while still keeping the stable and outstanding electrothermal performance. Here, a flexible and elastic composite heater with a stable electrothermal property under varied strain with large deformation is developed by mimicking the wrinkle feature of human skin in a carbon nanotube (CNT)/polydimethylsiloxane (PDMS) bilayered structure. The created wrinkle feature of CNT film from the resilience of PDMS makes the electrothermal heater a stable electrothermal performance within 30–40% strain in different directions. The aligned preference of CNTs in the CNT film gives the electrothermal heater an ability that shows different electrothermal performance depending on different angles between the direction of CNT alignment and the long axis of the sample. This composite electrothermal heater also presents a highly efficient electrothermal performance that can reach 200 °C within 30s upon 2 V. [ABSTRACT FROM AUTHOR]

Copyright of Transportation Science & Technolgy is the property of Transportation Science & Technology Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Offshore wind turbine (OWT) upsizing has become an inevitable trend. Compared with small OWTs, large OWT rotors exert greater horizontal loads and bending moments on the tower. These factors make a large OWT tower more prone to geometric nonlinear deformations, which can affect the normal operation of a wind turbine and even lead to damage to the wind turbine tower. Therefore, monitoring the deformation of large OWT towers is necessary. Shape sensing is a technique that uses surface strains to reconstruct deformed shapes. Currently, there is a lack of effective methods for geometric nonlinearity deformation shape sensing. In addition, the tower of OWT is a variable cross-section structure. The influence of varying cross-sections further increases the difficulty of developing a large deformation reconstruction algorithm. To solve this problem, this paper proposes a new method called rotation angle approximation (RAA). This method establishes a least-squares error functional using analytic curvature and section curvature. The rotation angles of the tower axis are obtained via this function. The deformed shape is then predicted via the boundary conditions and the rotation angles along the tower axis. Numerical simulations demonstrated this method can accurately predict the large deformations of a tower under different load conditions. • Proposed a new large deformation shape sensing method for beams with variable cross-section. • The deformed shapes can be predicted only using final measured strain. • Accurate deformation predictions can be achieved with fewer elements. [ABSTRACT FROM AUTHOR]

The prediction of crack propagation in materials is a crucial problem in solid mechanics, with many practical applications ranging from structural integrity assessment to the design of advanced materials. The phase-field method has emerged as a powerful tool for modeling crack propagation in materials, due to its ability to accurately capture the propagation of cracks. However, current phase-field algorithms suffer from the elevated computational cost associated with the so-called staggered solution scheme, which requires extremely small time increments to advance the crack due to its inherent conditional stability. In this paper, we present, for the first time, a quantitative analysis detailing the numerical implementation and comparison of two common solution strategies for the coupled large-deformation solid-mechanics-phase-field problem, namely the quasi-Newton based Broyden–Fletcher–Goldfarb–Shanno algorithm (BFGS) and the full Newton based alternating minimization (or staggered) (AM/staggered) algorithm. We demonstrate that the BFGS algorithm is a more efficient and advantageous alternative to the traditional AM/staggered approach for solving coupled large-deformation solid-mechanics-phase-field problems. Our results highlight the potential of the quasi-Newton BFGS algorithm to significantly reduce the computational cost of predicting crack propagation in hyperelastic materials while maintaining the accuracy and robustness of the phase-field method. • Computational efficiency is compared for three benchmark examples using developed UEL for Abaqus. • BFGS enhances efficiency over AM/Staggered for large-deformation solid mechanics phase-field problems. • Hyperelastic constitutive response of elastomers is considered with tension–compression asymmetry. [ABSTRACT FROM AUTHOR]

The shear strength behavior associated with a large shear deformation of both the fine- and coarse-grained unsaturated soils is important in interpreting and forecasting the initiation and movement of landslides. For this reason, a suction-controlled ring shear apparatus was designed by introducing modifications to the conventional Bromhead ring apparatus extending the axis translation technique. A series of suction-controlled ring shear tests were performed on fine- and coarse-grained unsaturated soil specimens subjecting to large shear deformation. The experimental results are presented and interpreted for highlighting: (i) the shear stress/void ratio-shear displacement relationships; (ii) the envelopes of the residual shear strength; (iii) the void ratio, water ratio and degree of saturation of the fine-grained soil specimens sheared to the residual state under different net normal stresses and matric suctions. These results provide valuable information toward understanding and interpreting the behaviors of landslides in unsaturated soils that experience the first failure and the reactivation along a pre-sheared slip surface. • Results of suction-controlled ring shear tests on unsaturated soils are presented. • Unsaturated clay softening in first and subsequent failures is discussed. • Unsaturated sand softens in first failure and hardens in subsequent failures. • Residual shear strength of unsaturated soils are interpreted. • Residual void ratio and degree of saturation of unsaturated soils are discussed. [ABSTRACT FROM AUTHOR]

Detailed FEM analysis models were created for steel floor structures including uninsulated beams and slabs. The simulated collapse behavior at elevated temperatures under fires involved the rupture of slab reinforcement around the bolted simple connections of the uninsulated secondary beams. Corresponding to the numerical results, full-scale heating and loading experiments were conducted. The vertical and horizontal loads were applied simulating the behavior of the connection of an uninsulated secondary beam at elevated temperatures. The experiment revealed that the critical collapse behavior around the connection is rupture of slab reinforcement followed by shear failure of the bolts. In the case that slab reinforcement is wire-mesh, the reinforcement may rupture under the out-of-plane flexural deformation during the development process of tension mechanisms associated with large deflection. In the case that deformed reinforcement is used for the slab, deformation capacity against out-of-plane deformation of the slab significantly increased. The collapse load under the tension mechanism was approximately 1.5 times the weight of a standard office floor, even with nearly minimum reinforcement for practical slab design. • Steel floor structures may collapse under fires involving the rupture of slab reinforcement around the bolted simple connections of the uninsulated secondary beams. • The rotational angle of the simple connection when the wire-mesh reinforcement ruptured was approximately 10%. • The uninsulated composite beams with deformed reinforcement for the slab can maintain a relatively stable state until the reinforcement fracture and collapse after the tension mechanism is developed. • The collapse load of the in the experiment of the uninsulated secondary beams is approximately 1.5 times the standard floor weight for offices. [ABSTRACT FROM AUTHOR]

• Severe floor heave is the main deformation feature of deep soft rock roadway. • Failure mechanisms of soft rock roadway in deep extra-thick coal seam are fully revealed. • A new collaborative reinforcement support technology is proposed. • The action mechanism of concrete-filled steel tube of bottom angle is studied. • The diffusion radius and diffusion depth of the grouts are determined. The soft rock roadway in deep extra-thick coal seam is prone to large deformation disaster. In order to solve this problem effectively, taking the W 3 101 coalface of Xiao'kang coal mine as the engineering background, the failure mechanisms and the corresponding control technology were investigated by the methods of laboratory test, numerical simulation and field measurement. First, a series of tests were carried out on the basic mechanical properties of rock mass, in-situ stress and loose zone, and it was found that the failure mechanisms of soft rock roadway in deep extra-thick coal seam are poor lithology of surrounding rock, high in-situ stress, large loose circle and unreasonable original support. Then, based on the supporting mechanisms of grouting cable and concrete-filled steel tube (CFST) of bottom angle, a new collaborative reinforcement support (CRS) technology combining the two was proposed. Next, the numerical simulation shows that the CRS technology has good applicability in controlling large deformation of soft rock roadway in deep extra-thick coal seam. Finally, to exhibit the engineering application effect of the proposed CRS scheme, it was also applied in Xiao'kang coal mine. Comparing to the controlling effect of original support scheme, it can be seen that the average deformation of soft rock roadway reduces by 73.2 % under the proposed CRS scheme, and the steel arch frame of bottom angle is slightly deformed. Meanwhile, it is found that the grouts diffusion radius is nearly 1.21 m, and the deepest diffusion depth is 4.25 m, which also indicates again that the feasibility of the proposed CRS scheme in controlling large deformation of soft rock roadway in deep extra-thick coal seam. [ABSTRACT FROM AUTHOR]

• General particle dynamics is proposed to address the large deformation mechanics. • GPD for nonlinear elastic and plastic constitutive model is established. • Relationships between GPD and other mechanical theories are discussed. • Numerical examples verify GPD's ability in large deformation and fracture problems. This paper presents a detailed investigation on the General Particle Dynamics (GPD) method and its implications for addressing challenges in large deformation mechanics and fracture modeling. The GPD method integrates nonlocal interactions and nonlocal differential operators to overcome limitations of classical continuum mechanics in capturing long-range interactions and material behaviors under extreme deformation conditions. Through a systematic examination of the physical and mathematical foundations of GPD, including its governing equations and constitutive relations, we elucidate the robust and applicability of the proposed method in simulating complex deformation phenomena. Furthermore, the relationships among GPD, conventional mechanical theories (Smoothed Particle Hydrodynamics), nonlocal theory (Peridynamics) and Molecular Dynamic theories are discussed. Numerical examples related to large deformation and fracture problems are tested to verify the ability of the proposed method. The numerical results show that GPD inherits the advantages of the classical method and also has its unique properties in solid fracture mechanics and large deformation problems, making it a promising approach in computational mechanics. [ABSTRACT FROM AUTHOR]

In soft rock traffic tunnels with significant deformations, determining the applicable conditions and designing key parameters for active prestressed and prestressed yielding support modes are crucial for ensuring the safety and cost-effectiveness of tunnel construction. Consequently, the fundamental principles and methods for designing active prestressed and prestressed yielding support, encompassing aspects like support mode selection and support parameter determination, are proposed based on analyzing the interaction mechanism between active prestressed support and surrounding rock. First, the geometric parameters of the anchorage system are designed, including length and spacing, by considering stress diffusion effects in the surrounding rock, rock displacement control efficiency, and economic factors. Long lengths result in better control over surrounding rock displacement but reduce the stress diffusion effect in surrounding rock. Appropriate geometric parameters should ensure that stress diffusion from the anchorage system creates a continuous effective stress compression zone in the surrounding rock. If necessary, combinations of short and long anchorage lengths should also be considered for the design. Subsequently, predictions are made for the surrounding rock's deformation and the elongation rate of the anchorage system under the maximum allowable prestress. The prestress can be set as 2/3 of the yielding strength of anchor body material. The predicted elongation rate of the anchorage system is then compared to a control value to determine the appropriate support mode. This safety control elongation rate can be set as 2/3 of the elongation rate under maximum force. If the predicted elongation rate is lower than this safety control value, the active prestressed support mode is selected, requiring only the design of the prestress. The prestress should not exceed the maximum allowable prestress and should be selected in conjunction with the predicted rock deformation. Conversely, if the predicted elongation rate exceeds the safety control value, the active prestressed yielding support mode is selected. This mode requires the design of parameters such as prestress, yielding force, and yielding slip amount. In this case, the prestress can be taken at a relatively high value while considering anchorage safety. The yielding force should be appropriately higher than the pretightening force. In the active prestressed yielding support mode, the elongation rate control value is increased based on the original control value to account for yielding elongation. The yielding slip amount should not be excessively high to ensure that the predicted elongation rate meets the safety control standard. Parameters balancing structural safety and construction economy are recommended. Finally, the selected support mode and support parameters determine the recommended value for reserved deformation of the surrounding rock. These principles and methods of support design guide the selection and parameter design of active prestressed and prestressed yielding support modes in squeezing soft rock traffic tunnels with large deformation. [ABSTRACT FROM AUTHOR]

Soft rock tunnels with high ground pressure will experience significant deformation of the surrounding rock. In order to improve the stability of soft rock tunnel excavation with significant ground stress, it is essential to study new high-performance tunnel lining materials. This research aims to introduce a new method of one single lining with airbag resistance limiter support to solve large deformation. For the first time, we used a novel energy-absorbing inflatable airbag resistance limiter. The composite structure of "rock + airbag resistance limiter + rigid support" is adopted in this study. In the experimental scheme circular tunnel lining model is divided into two cases: Case 1, rigid support, and Case 2, rigid support with a one-layer airbag resistance limiter. The test results indicate the following; (1) the rigid support with airbag limiter support effectively controls the large deformation of surrounding rock, and the deformation control ability of Case 2 is better than that of Case 1. (2) The contact pressure in both cases increases by imposing load, comparing with Case 2, surrounding rock pressure of Case 1 is greater. (3) The longitudinal strain of the three different sections in Case 2 was significantly reduced compared to the ordinary lining of Case 1. Additionally, the maximum lateral compression strain of Case 2 was significantly reduced to 23.3 % of Case 1. The test results indicate that the rigid support with an airbag resistance limiter support is better than the rigid support without an airbag in terms of crack resistance, stability, effectiveness, and deformation control capability. However, the study results indicate that the proposed method using the new support technology of an inflatable airbag resistance limiter is feasible and effective. The integrity and safety of the resistance limiter are guaranteed, the airbag is easy to obtain, the processing is convenient, and its structure is simple and user-friendly. The airbag resistance limiter is an economical, efficient, and safe supporting structure. [ABSTRACT FROM AUTHOR]

Glass laminates consist of stiff glass plies permanently shear-coupled by polymeric interposed layers. When an external temperature rise occurs, the interlayers undergo a dramatic stiffness decay. As a consequence, not only the sectional warping typical of alternating stiff/soft composites is intensified, but also the overall behavior may evolve counter-intuitively. When slender elements prone to geometric nonlinearities are involved, even small thermal variations in intensity or distribution may act as uncertainty factors, strongly affecting the outcome. This paper proposes an efficient, robust, and accurate numerical framework to perform the sensitivity analysis to thermo-mechanical actions in glass plates. A large deformation isogeometric Kirchhoff-Love shell model enriched with through-the-thickness warping is employed, together with a generalized arc-length method involving a suitable temperature parameter as an additional unknown, namely the thermal amplifier or a spatial distribution coefficient. Numerical experiments are presented to highlight the effects that even small temperature variations produce on the equilibrium paths and the influence of the stiffness loss in the interlayer on the structural behavior and the accuracy of the models. • Sensitivity analysis to thermo-mechanical actions in glass plates. • Uncertainty in intensity and spatial distribution of the temperature. • Temperature dependent material properties. • Generalized arc-length method involving a temperature parameter. • An isogeometric hierarchic approach is used for large deformations, including transverse shear strains and zigzag effects. [ABSTRACT FROM AUTHOR]

Earthquake-induced liquefaction and consequent failure of geomaterials have been recognised as a geohazard that causes significant damage to geotechnical infrastructures. Predicting such large deformation events has proven to be a challenging topic, which requires the development of powerful numerical tools and advanced soil models. The Smoothed Particle Hydrodynamics (SPH) method has been successfully applied to simulate large deformations and post-failure processes of geotechnical problems, including seismic large deformation analyses. However, the SPH simulation of earthquake-induced liquefaction and large deformation of geotechnical problems remains challenging, primarily due to the lack of a stabilised computational framework capable of capturing the complex responses of soil liquefaction. This study addresses this research question with the developments and applications of a fully coupled flow-deformation SPH framework incorporating the SANISAND model for solving earthquake-induced liquefaction problems. Several stabilisation techniques, including Rayleigh damping, stress diffusion and pore-pressure diffusion, are introduced to improve the stability and accuracy of SPH simulations. Additionally, a robust stress update method, combining the sub-stepping technique and cutting-plane algorithm, is proposed to effectively integrate the constitutive laws of the SANISAND model during large deformation SPH simulations. Verification of the proposed SPH framework against theoretical solutions shows its effectiveness before being applied to simulate several shaking table tests reported in the literature. The proposed SPH framework and model are able to reproduce experimental results in several simulations, demonstrating their potential and capability for the future prediction of earthquake-induced liquefaction and failure of geo-infrastructures. [ABSTRACT FROM AUTHOR]

• A theoretical model is proposed to analyze the effect of the strength-stress ratio and support pressure. • The distributions of strength-stress ratio, relative deformation and support pressure were statistically analyzed. • A novel large deformation classification method based on relative support pressure index is proposed. Accurately assessing the level of large deformation in squeezing tunnels is of great importance for the design of support structures. The current large deformations classification methods fail to account for the effect of support pressure on the relative deformation of surrounding rock. In this study, a theoretical model for the stress–strain state zoning of the surrounding rock in squeezing tunnels is established. A sensitivity analysis of the model parameters is conducted. The distribution law of the strength-stress ratio, relative deformation, and relative support pressure indices in 43 field monitoring squeezing tunnels are statistically analyzed. A novel large-deformation classification method based on the relative support pressure index is proposed and applied in case studies. The parameter sensitivity analysis shows that mechanical parameters of the surrounding rock significantly affect the deformation and the stress–strain state zoning of the surrounding rock. The stress–strain state zoning and deformation of the surrounding rock are also primarily dependent on the matching relationship between strength-stress ratio and support pressure. Statistical analyses indicate that there is a nonlinear negative correlation between the relative deformation of the surrounding rock and the strength-stress ratio, as well as the relative support pressure, which includes the steel arch relative support pressure index (SSPI) and the anchor bolt relative support pressure Index (ASPI). The key to controlling surrounding rock deformation lies in the rational matching of support pressure to the strength-stress ratio. In the novel large deformation classification method, three key indexes of strong stress ratio, relative deformation and relative support pressure are quantitatively included, and squeezing large deformation is divided into three levels. Moreover, the case study demonstrated that the novel large deformation classification method has significant guiding importance in verifying feasibility and optimizing support design schemes during both the design and construction phases. [ABSTRACT FROM AUTHOR]

Roadside safety structures (i.e., barrier systems) with thin-walled, soil-embedded support piles are critical in reducing the consequences of run-off-road (ROR) crashes, contributing to numerous deaths and injuries, and significant societal costs. Enhanced knowledge and understanding of soil-embedded barrier systems, especially the dynamic pile-soil interaction under vehicular impact, can help to lessen the severity of such crashes and preserve human life. Although the design and analysis of soil-embedded barrier systems have advanced significantly, existing modeling techniques cannot accurately capture large soil deformations under impact loading. In order to bridge this gap, this study proposes a novel computational methodology by coupling the Finite Element Method (FEM) and Arbitrary Lagrangian-Eulerian (ALE) method. Validated against extensive physical impact test data covering a variety of pile shapes, embedment depths, material properties, and impact conditions, this methodology effectively captures the dynamic responses of steel tube pile-soil systems involving large soil deformations and fluid-like soil flow. The coupled FEM-ALE-based methodology provides a more realistic simulation of laterally impacted pile-soil systems, potentially reducing the number of, and even the need for, full-scale crash tests. This study also provided mechanistic insights into the dynamic pile-soil systems' response to impact loading. A comparison with the pure Lagrangian approach showed the coupled FEM-ALE model's robustness, adaptability, and accuracy, advancing the understanding of dynamic soil-structure interactions under impact loading. • A novel simulation tool–the coupled FEM-ALE method–has been developed to capture dynamic pile-soil interactions under vehicular impacts. • The new method addresses limitations in current simulation techniques that often fail to accurately capture large soil deformations. • The methodology is validated using impact tests featuring a variety of pile shapes, embedment depths, and impact conditions. • Dynamic responses predicted by models were within 5 % to 12 % of the impact test data, implying high fidelity in simulating real-world phenomena. • A direct comparison with the traditional pure Lagrangian approach highlights the method's improved adaptability, robustness, and accuracy. [ABSTRACT FROM AUTHOR]

• The mesoscale residual stress due to manufacturing process is identified as a class of defects for photo-cured materials. • The defects are reduced as uncured inclusions embedded within a fully cured, infinite matrix which are then additionally cured. • A large deformation theoretical model is developed for determining the nonlinear elastic field of the inclusions. • Theoretical results are in reasonable agreement with finite element analysis in terms of different Poisson's ratio and inclusion geometry. A wide variety of photo-cured materials have recently been developed with the rapid advancement of three-dimensional (3D) printing technology. However, most of these materials are designed as soft functional materials, and their failure mechanisms have received little attention. This work studies the mesoscale residual stress defects of photo-cured materials that are generated due to non-uniform curing and volume shrinkage during the manufacturing process. The defects are simplified as uncured inclusions embedded within a fully cured, infinite matrix which are then additionally cured. A large deformation model, validated against finite element analysis, is established to determine the nonlinear elastic field induced by the curing of inclusions with different Poisson's ratio and shape (i.e., sphere and prolate spheroid), and is shown to outperform the infinitesimal strain model. This large deformation model, which includes a phase evolution constitutive model to describe the inclusion's behavior and a compressible neo-Hookean model to describe the matrix's behavior, is derived based on the same elastic field distribution as that in the infinitesimal strain solution and an ellipsoid-ellipsoid transformation kinematics assumption. The final solution is expressed in a discrete formulation and is exact for the spherical inclusion and approximate for the prolate spheroid inclusion. The prediction results of the theoretical model are compared with the finite element analysis, and reasonable agreement is obtained. This study may lay a foundation for investigating the effects of mesoscale residual stress defects on the mechanical behavior of 3D printing materials. [ABSTRACT FROM AUTHOR]

• Algorithms for surface reconstruction based on surface strain measured by adhesive sensors. • Graphene/AgNWs strain gauge with optimized shape to minimize installation errors. • Reconstruction system capable of real-time reconstruction of wing surface deformations. Surface-sensing technology with high precision is a pivotal technological support for the real-time monitoring of aircraft wing structures. To address the limitations of existing testing methods for online detecting of flexible wing surface deformation, this study proposes a graphene-based flexible electronic skin which can be directly attached to the surface of aircraft wings to obtain real-time strain information at critical nodes. Subsequently, an optimized reconstruction method is proposed on the basis of the Ko displacement theory is used to achieve reconstructed wing surface deformation. The reconstruction results based on the optimized method exhibit an error rate below 5%. The research results provide an effective technical means for the online health monitoring of aircraft wing structure. [ABSTRACT FROM AUTHOR]

The paper presents a refined implicit two-phase coupled Material Point Method (MPM) designed to model poromechanics problems under static and dynamic conditions with stability and robustness. The key variables considered are the displacement and pore water pressure. To improve computational efficiency, we incorporate the Finite Difference Method (FDM) to solve pore pressure, stored at the center of the background grid where the material points reside. The proposed hydromechanical MPM cannot only effectively addresses pore pressure oscillation, particularly evident in nearly incompressible fluids-a common challenge with Galerkin interpolation, but also decreases the degrees of freedom of the system equations during the iteration process. Validation against analytical solutions and various numerical methods, encompassing 1D and 2D plane-strain poromechanical problems involving elastic and elastoplastic mechanical behavior, underscores the method's resilience and precision. The proposed MPM approach proves adept at simulating both quasi-static and dynamic saturated porous media with significant deformation. [ABSTRACT FROM AUTHOR]

Computational modelling of complex timber-metal connections undergoing large deformations is crucial for the design of safe and robust multi-storey timber structures. Accurate simulation through large deformations requires constitutive models that suitably capture the full post-elastic behaviour of materials. Post-elastic behaviour of timber is particularly challenging to model due to strong anisotropy and material non-linearity in the post-elastic regime. Efficient simulation of complex connections requires advanced numerical modelling techniques to expedite explicit solution in the finite element domain. In this study, a suitable constitutive model for ductile metal components through large deformations, including consideration of stress localisation and triaxiality post-necking, is described. Some existing constitutive models for timber are discussed, and new constitutive models capturing both ductile and brittle failure modes are presented. A new formulation of the Hoffmann yield criterion with isotropic hardening for explicit solution is presented, and new VUMAT user subroutines for explicit solution in ABAQUS for Hoffmann, Sandhaas, Gharib, Hill-Gharib and Hoffmann-Gharib models are developed and made available for the benefit of other researchers. A benchmarked numerical model incorporating advanced modelling techniques to improve computational efficiency without compromising accuracy is presented for a complex timber, aluminium and steel dowelled beam-column connection tested shear and moment dominated testing. The simulation results compare favourably with experimental results in the literature, demonstrating that the proposed constitutive models and numerical modelling techniques provide realistic predictions of behaviour, including failure mode, and thus have the potential to support the design of complex timber-metal connections through large deformations under quasi-static and dynamic loading. • Behavior of complex timber-metal connections under large deformations is modelled using explicit FEA. • Composite Hill-Gharib and Hoffmann-Gharib constitutive models for timber are proposed. • Subroutines for explicit FEA are developed for Hoffman, Sandhaas, Gharib, Hill-Gharib and Hoffmann-Gharib timber models. • The VUMAT user subroutines developed in this study are made available for the benefit of other researchers. • Load-rate and mass-scaling techniques allow computationally efficient explicit FEA under quasi-static test conditions. • A composite Hill-Gharib constitutive model is shown to best simulate behavior in a benchmarked FEA example. [ABSTRACT FROM AUTHOR]

An essential technique for spine surgery guidance is the registration of intraoperative 2D X-ray with preoperative 3D CT, which enables the correlation of real-time imaging with surgical planning. Previous deep-learning-based methods generally need to convert 3D CT into a 2D projection for further registration, resulting in the loss of spatial information and failing to satisfy the clinical requirements of a large adaptation range and high precision. In this paper, a novel transformer-based two-step registration network is proposed to directly regress the transformation parameters without dimension reduction of the 3D CT. The spine information is extracted by reconstruction and segmentation modules and is further used in the registration network that utilizes both the original images and the spine features. Meanwhile, an adaptive multi-dimensional loss function containing both parameter-domain loss and graph-domain loss is designed to be more consistent with the registration mechanism. Both improvements expand the range of acceptable deformations and increase registration accuracy. We demonstrate the validity and generalizability of the proposed method by achieving state-of-the-art performance on both synthesized and clinical data with an average mTRE of 0.96 mm and 2.32 mm. Further, the high registration performance over a large deformation reflects the robustness of the methods in complex scenarios. The proposed methods enhance the tremendous potential of deep learning in spinal surgery navigation. • A novel two-step semantic-attention-based registration network (TS-SAR-NET) is designed to solve the registration problem in spine surgery guidance. The designed module converts 2D X-ray and 3D CT into 3D features to avoid spatial information loss. In addition, the module exploits features at different scales to meet the requirements of a large adaptation range and high precision. • Semantic information (spine features) is introduced into the registration network to utilize the semantically meaningful regions to achieve higher precision. Meanwhile, an adaptive loss function that contains both parameter-domain loss and graph-domain loss is designed to meet the requirement of both large-adaptive range and high precision. • The designed method was validated with both synthesized and clinical data. The results show better performance and demonstrate higher robustness, especially on data with a large initial deformation. [ABSTRACT FROM AUTHOR]

Landslides caused by the progressive failure of sensitive clay slopes may cause substantial economic losses and environmental pollution to pipelines. This study utilizes the Karhunen-Loève (K-L) expansion method, the coupled Eulerian-Lagrangian (CEL) method, and the Monte Carlo method to model the large deformation behaviour of slopes with spatial variability. The proposed RCEL-MC framework for joint analysis of extensive deformation-probability statistics of landslide impact on pipelines confirms that the spatial variability clay slope instability failure mechanism, considering the soil softening effect under earthquake action, aligns more closely with real-world scenarios. Furthermore, based on the statistical failure probability of pipelines impacted by landslides, a sensitive clay slope pipeline safety design method is suggested. The research highlights that the random field parameters significantly influence the load-bearing characteristics of pipelines affected by spatially variable slope progressive failure landslides. The uncertainty surrounding the maximum impact force on pipelines notably increases with the rise of the horizontal correlation length and variability coefficient. When accounting for spatial variability, the maximum impact force on landslide pipelines surpasses the deterministic model analysis results by 28-69 %. It is emphasized that the deterministic model analysis, which neglects the spatial variability of soil and the soil softening effect, may seriously underestimate landslide risk. Based on the criteria for pipeline buckling failure and yield failure, it is advised that the safe design parameters for pipelines in practical projects should fall within the intersection of the secure regions defined by the two failure criteria. [ABSTRACT FROM AUTHOR]

Stimuli-responsive shape memory polymer (SMP) nanocomposites, characterized by their shape memory capability and customizable properties, have significantly expanded their range of applications when compared to pristine SMPs. This pioneering paper is centered on describing an efficient numerical approach for evaluating the thermomechanical behavior of ternary acrylate-based SMP nanocomposites containing carbon nanotube (CNT) and graphene nanoplatelet (GNP) hybrids. To this aim, a micromechanical procedure based on thermo-visco-hyperelastic constitutive model, which aids in avoiding employing intricate user-defined material subroutines, is developed through the finite element method (FEM). The parameters required for satisfying the governing equations of the rheological model, including thermal expansion and Prony series coefficients, plus Williams-Landel-Ferry equation and Neo-Hookean strain energy function parameters, are derived from accessible experiments to assign SMP properties. A Python-based script is implemented in a stochastic-iterative process to generate appropriate periodic representative volume elements (RVEs) with various microstructures. Thereupon, thermomechanical shape memory cycles in uniaxial tension are simulated by creating loading, cooling, unloading, and heating steps in the Abaqus solver. Following achieving satisfactory agreement between the presented scheme and experimental measurements, case studies are performed to reflect the influences of dispersion type, volume fraction, and geometry of carbonaceous nanofillers, as well as the contribution of nanofiller/matrix interphase region, upon stress-free/shape-recovery and fixed-strain/stress-recovery thermomechanical cycles. • 3D micromechanics-FEM modeling of thermomechanical behavior of SMP nanocomposites. • Assigning SMP properties based on thermo-visco-hyperelastic rheological model. • Generating CNT- and GNP-embedded periodic RVEs in a stochastic-iterative process. • Simulating reversible transformations in a multistep framework. • Validating the developed scheme plus microstructure-level parametric studies. [ABSTRACT FROM AUTHOR]

During the excavation of a water-conveyance tunnel in Tertiary soft rocks in China, significant deformation of the surrounding rocks and damage to the support were observed. Substantial horizontal deformation, reaching magnitudes of meters, was observed in the right side wall after a certain period of tunnel excavation. Extensive investigations, including field surveys, monitoring data analysis, laboratory tests, and numerical simulations, were conducted to understand the underlying mechanisms of this large deformation. The section of the tunnel with large deformation consisted of Tertiary sandy mudstone, mudstone interbedded with marl, and glutenite. Laboratory tests and mineral composition analysis revealed that the sandy mudstone and mudstone interbedded with marl exhibited low strength, which was closely related to the water content of the rock specimens. The compressive strength gradually decreased with increasing water content, and when the water content of mudstone interbedded with marl reached 26.96%, the uniaxial compressive strength decreased to only 0.24 MPa. Additionally, sandy mudstone and mudstone interbedded with marl contained a significant amount of hydrophilic minerals, with montmorillonite constituting 30% and 34% of the two rock samples, respectively. The tunnel passed beneath a perennially flowing gully, and a highly permeable glutenite layer was present in the middle of the tunnel. This resulted in groundwater seepage from the inverted arch during excavation, leading to the softening effect on the mudstone interbedded with marl in the lower part of the tunnel. Through numerical simulation and back-analysis techniques, the varying degrees of softening induced by groundwater were quantitatively analyzed in the surrounding rocks on the left and right sides. The study revealed that the large deformation of the tunnel was triggered by two factors: the plastic flow caused by tunnel excavation under the low strength of the surrounding rocks and the softening effect of groundwater. The damage to the support system was primarily attributed to the squeezing and swelling deformation of the surrounding rocks and the non-uniform deformation between different rock layers.