Large Deformation Research Articles

FEM modelling of hydrogen embrittlement in API 5L X65 steel for safe hydrogen transportation

Abstract Hydrogen is crucial for decarbonization efforts due to its abundance, environmental friendliness, and versatility. To maximize its potential, an efficient transportation infrastructure is essential. While utilizing the natural gas pipeline network for transporting hydrogen is cost-effective, hydrogen embrittlement (HE) poses a significant challenge. When hydrogen enters the metal, it significantly compromises its fracture toughness. This study investigates the impact of high-pressure hydrogen on the mechanical properties of API 5L X65 carbon steel through a combined experimental and computational approach. To quantify the extent of HE, tensile tests were performed on identical specimens, one set pre-exposed to high-pressure hydrogen and another set kept in an inert environment for comparison. Finite element modelling, employing the Bai-Wierzbicki material model (BWMM), was used to simulate the material behaviour under large plastic deformations and correlate with experimental results. This synergistic approach integrates experimental data with simulations, creating a framework for predicting and preventing catastrophic failures.

The THE EFFECT OF ZIRCONIUM ADDITIVES ON PROPERTIES OF (Cu22%Zn4%Al) SHAPE MEMORY ALLOY

Shape memory alloys (SMAs) are one of the most important types of smart materials. It define as the materials that can undergo large pseudo elastic deformations while having the ability to recover to their original shape once subjected to a memory stimuli such as a specific temperature ,stress ,or strain. This study examines the effects of varying Zirconium (Zr) additive amounts on the microstructure, mechanical, and shape memory effect for all specimens of Cu-Zn-Al SMAs. Powder metallurgy was used to create Cu–22%Zn–4%Al SMAs, both base and with the inclusion of 0.2 and 0.4 weight percent Zr. 650MPa compact pressure was used to create the alloys after the particles had been mixed for five hours. The alloys underwent a three-step sintering procedure in a vacuum tube furnace for one hour at 350 ˚C, then for one hour at 550 ˚C, and for two hours at 850 ˚C. To characterise the microstructural and phase characteristics of alloys, both with and without Zr additions, XRD diffraction analyses, optical microscopy (OM), and scanning electron microscopy (SEM) were performed. With differential scanning calorimetry, the transition temperatures of all alloys were determined (DSC).As well as the shape memory effect test (SME) was measured. Results confirmed that all alloys compositions were found to include the predominant (Cu5Zn8) phase, as proven by XRD and microstructural investigation. The Zr addition dramatically lowered the transition temperatures, according to the transformation temperature data. Hardness experiments reveal that alloys' hardness and volume losses were enhanced by adding up to 0.4% weight percent of Zr reached to (64.8%) and (0.3909)mm3 respectively compared to base alloy.

A Simple, Scalable Large Deformation Solid Mechanics Implementation in the MOOSE Framework

This paper describes a large deformation solid mechanics solver implemented as part of the freely-available and open-source MOOSE finite element simulation framework. The paper documents the choices made in developing the solid mechanics framework and describes novel formulations for the gradient operator and constitutive modeling framework made to simplify implementations of different coordinate systems, stabilized gradient operators, and different constitutive model inputs and outputs. In the process, the paper describes a new formulation that casts objective integration of the Cauchy stress as a linear transformation of the small stress rate. Finally, the paper presents key implementation details and examines the parallel efficiency of the solid mechanics solver implemented in MOOSE. The implementation retains good weak scaling efficiency beyond 1,000 parallel processes. The papers includes a discussion of the factors limiting the parallel efficiency of implicit, large deformation solid mechanics codes on current high-performance computers, with the main current limitation being the scalability of the algebraic multigrid methods used to solve the linearized equilibrium equations.

Multifunctional Strain/Pressure Sensor Based on Ag@Polydopamine Nanohybrid Methacrylamide Chitosan/Polyacrylamide Hydrogel for Healthcare Monitoring.

Hydrogels have emerged as promising candidates for flexible sensors due to their softness, biocompatibility, and tunable physicochemical properties. However, achieving synchronous satisfaction of conformality, conductivity, and diverse biological functions in hydrogel sensors remains a challenge. Here, we proposed a multifunctional hydrogel sensor by incorporating silver-loaded polydopamine nanoparticles (Ag@PDA) into a thermally cross-linked methacrylamide chitosan (CSMA) and acrylamide network, namely, Ag@PDA/(CSMA-PAM). The Ag@PDA/(CSMA-PAM) hydrogel showed the capability to respond effectively to both strain and pressure, enabling its independent application as either a strain sensor or a pressure sensor. The sensitivity of the hydrogel can reach 2.13 within the strain range of 65 to 150%, exhibiting a response and recovery time of 550 ms when utilized as a strain sensor. In contrast, its sensitivity was 0.07 kPa-1 during pressures ranging from 0 to 2.15 kPa, with a response and recovery time of 136 ms when employed as a pressure sensor. Additionally, the hydrogel sensor demonstrated high linearity (0.998 for strain and 0.98 for pressure), stable cycling ability (500 cycles), and low detection limit (0.5% for strain and 150 Pa for pressure). Moreover, the Ag@PDA/(CSMA-PAM) hydrogel exhibited good stability and reliability for a variety of practical applications, including the detection of subtle and large deformations, as well as real-time physiological activity monitoring. Further, owing to the bioactive components of chitosan and Ag@PDA present in the hydrogel, the Ag@PDA/(CSMA-PAM) sensor exhibited satisfactory biocompatibility along with excellent antioxidant and antibacterial activities, making it highly promising for applications as wearable sensors in personalized healthcare.

Effect of non-starch components in liangpi slurry on thermal and rheological properties of concentrated wheat starch gels.

Liangpi, a traditional Chinese cold skin noodle, primarily consists of wheat starch in a concentrated gel system. However, high-quality liangpi cannot be solely produced with pure wheat starch. The effects of endogenous non-starch components in liangpi slurry (LPS) on wheat starch properties were investigated by mixing LPS with wheat starch slurry (WSS) in various LPS/WSS ratios. Results showed that increasing LPS/WSS ratios significantly enhanced the swelling power and water-holding capacity at 70°C and 90°C. The gelatinization onset temperature of LPS/WSS samples rose from 80.5°C for pure WSS to 83.3°C for LPS. The peak viscosity of LPS was more than three times higher than that of WSS, and the breakdown viscosity also increased with the incorporation of non-starch components. In concentrated systems, the storage modulus (G') and loss modulus (G") of the resultant gels gradually increased with higher LPS/WSS ratios. However, gel fluidity, frequency dependence of G', and gel hardness do not exhibit a linear relationship with LPS/WSS ratios, reaching their maximum values at LPS/WSS ratios of 6:4 or 4:6. Their trends were also similar to gel cohesiveness and the critical strain under large amplitude oscillatory shear. This suggested that non-starch components improved small deformation properties but compromised gel stability under large deformations. This was further evidenced by Lissajous curves evolution of LPS gels, with LPS gels showing higher strain hardening coefficient, shear thinning coefficient, and harmonic ratio compared to WSS gels. This study points the way for future research to identify the specific non-starch component that matters.

Fluid–structure coupled simulation framework for lightweight explosion containment structures under large deformations

Fluid–structure coupled simulation framework for lightweight explosion containment structures under large deformations

Viscoelastic, Shape Memory, and Fracture Characteristics of 3D-Printed Photosensitive Epoxy-Based Resin Under the Effect of Hydrothermal Ageing

Using 3D-printed (3DPd) polymers and their composites as shape memory materials in various smart engineering applications has raised the demand for such functionally graded sustainable materials. This study aims to investigate the viscoelastic, shape memory, and fracture toughness properties of the epoxy-based ultraviolet (UV)-curable resin. A UV-based DLP (Digital Light Processing) printer was employed for the 3D printing (3DPg) epoxy-based structures. The effect of the hydrothermal accelerated ageing on the various properties of the 3DPd components was examined. The viscoelastic performance in terms of glass transition temperature (Tg), storage modulus, and loss modulus was evaluated. The shape memory polymer (SMP) performance with respect to shape recovery and shape fixity (programming the shape) were calculated through dynamic mechanical thermal analysis (DMTA). DMTA is used to reveal the molecular mobility performance through three different regions, i.e., glass region, glass transition region, and rubbery region. The shape-changing region (within the glass transition region) between the Tg value from the loss modulus and the Tg value from the tan(δ) was analysed. The temperature memory behaviour was investigated for flat and circular 3DPd structures to achieve sequential deployment. The critical stress intensity factor values of the single-edge notch bending (SENB) specimens have been explored for different crack inclination angles to investigate mode I (opening) and mixed-mode I/III (opening and tearing) fracture toughness. This study can contribute to the development of highly complex shape memory 3DPd structures that can be reshaped several times with large deformation.

Integrated adaptive particle filtering-based color digital image correlation for large deformation measurement

In large deformation measurement, digital image correlation (DIC1Digital image correlation (DIC).1) using functional forms can no longer describe the complex changes in grayscale information and morphology of sub-regions. To address this issue, particle filtering (PF) can be combined with color DIC (PFDIC2Color digital image correlation method integrated with particle filtering. (PFDIC).2) to establish a color distribution model to describe sub-regions, but PFDIC has poor performance. Therefore, this paper proposes an integrated adaptive particle filtering-based color digital image correlation (APF-DIC3Integrated adaptive particle filtering-based color digital image correlation (APF-DIC).3). This method first constructs a dynamic color distribution model based on ACFEF4Adaptive color feature extraction function (ACFEF).4 to describe the sub-region. It then introduces the SSKL5Smoothed symmetric Kullback Leibler (SSKL).5 correlation coefficient to measure the similarity between sub-regions, and establishes TAR6Hyperbolic tangent adaptive resampling (tanh-adaptive resampling, TAR).6 to adaptively adjust the number of particles, ultimately achieving adaptive matching of sub-regions under complex deformations. Performance evaluation and simulation results show that APF-DIC significantly improves the accuracy, robustness, and computational efficiency of the algorithm. Real experimental results further verify the effectiveness of APF-DIC, demonstrating its excellent illumination invariance.

Experiment research on the control method of automatically retained entry by roof cutting pressure relief within thick hard main roof longwall top coal caving panel

To address the large deformation of goaf-side entries resulting from intense dynamic pressure, a method involving automatically retained entry by roof cutting pressure relief (ARERC) technology is proposed for use in thick and hard main roof longwall top coal caving (THLTCC) panel. Both physical and numerical model experiments have been conducted to verify the effectiveness of ARERC technology in controlling deformation. The evolution laws of stress and deformation in the surrounding rocks of the retained entry and the mechanism of pressure relief by roof cutting are analyzed. Results indicate that this technique optimizes the roof structure of the roadway and interrupts roof stress transfer between the retained entry and goaf. Consequently, the maximum vertical stress on the roof-cutting side of the retained entry roof is generally lower than on the uncut side. The retained entry deformation undergoes four distinct stages behind the panel: the pressure relief stage, deformation stage, compaction stable stage and stabilization stage. Notably, the deformation stage exhibits the highest deformation rate for the roadway. Therefore, it is recommended to utilize single hydraulic props for temporary support during the deformation stage to prevent damage to the retained entry caused by dynamic pressure disturbance. Based on the above analysis, several recommendations are provided for the field application of ARERC technology. Finally, the results from engineering application show the effectiveness of ARERC technology in controlling the deformation of the goaf-side entry. This ARERC technology can be extended to other coal mines with similar geological conditions.

Meshfree method for large deformation analysis without domain re-mesh: A nonlinear scheme based on stabilized collocation method

Meshfree method for large deformation analysis without domain re-mesh: A nonlinear scheme based on stabilized collocation method

PDE-LDDMM meets NODEs: Introducing neural ordinary differential equation solvers in PDE-constrained Large Deformation Diffeomorphic Metric Mapping

PDE-LDDMM meets NODEs: Introducing neural ordinary differential equation solvers in PDE-constrained Large Deformation Diffeomorphic Metric Mapping

Development and investigation of novel negative stiffness metamaterial based on ring shaped elastic deformation element

Abstract In the last few years, the concept of mechanical type negative stiffness metamaterial (NSM) has gained greater attention and developed into an emergent field of research, partly because of advancements in additive manufacturing (AM) technologies that enable rapid fabrication of materials. In this work, a versatile bistable unit cell design is proposed which exhibits large deformation. A theoretical model is developed and verified with experimental testing to accurately estimate snap-through behaviour of unit cell. The bulk of theoretical model findings fall within a 10% range of the experimental results. This study demonstrates that the theoretical model that was proposed is accurate in its ability to predict the snap-through transition. Further, a methodical parametric investigation is conducted into how geometric factors affect the snap-through characteristics. By adjusting the geometrical parameters of a unit cell, the needed mechanical behavior of NSM may be tailored for a specific application. Finally, 2D NSM lattice structure is developed which exhibits multistability, tunable deformation, and deterministic deformation sequence. These tunable behaviours can be controlled by setting proper values for geometrical parameters across the lattice. This study contributes to the design, development and manufacture of tunable NSM and multistable structures.

A renormalized slip-tube anisotropy model for sliding cross-links in soft gel towards ultrahigh toughness

Abstract Adaptive cross-links in polymer networks enable slide-ring and highly entangled gels with excellent mechanical toughness including high extensibility and strong fracture resistance. However, few studies have been conducted to explore the connection between adaptive cross-linking networks and topological structures, and also their deformation mechanism in network structures has not been fully understood. In this study, a renormalized slip-tube anisotropy model is developed to describe the topological polymer networks and understand working principles of adaptive cross-links in topological networks in the sliding gels. Initially, Langevin chain statistics is employed to characterize the stored segment redistribution and large deformation behavior of polymer chains with using an adaptive factor. Moreover, a renormalized slip-tube free energy equation has been formulated by introducing the tube constraint free energy to describing the topological mechanics and thermodynamics for the adaptive cross-linking networks. Furthermore, an anisotropic model is extended to describe the topological networks and mechanical toughening behaviors in sliding gels. Finally, the proposed model has been verified using the experimental results reported in literature, providing a fundamental approach to formulate the topological toughening principle in sliding gels undergoing mechanically adaptive cross-linking.

Highly deformable flapping membrane wings suppress the leading edge vortex in hover to perform better

Airborne insects generate a leading edge vortex when they flap their wings. This coherent vortex is a low-pressure region that enhances the lift of flapping wings compared to fixed wings. Insect wings are thin membranes strengthened by a system of veins that does not allow large wing deformations. Bat wings are thin compliant skin membranes stretched between their limbs, hand, and body that show larger deformations during flapping wing flight. This study examines the role of the leading edge vortex on highly deformable membrane wings that passively change shape under fluid dynamic loading maintaining a positive camber throughout the hover cycle. Our experiments reveal that unsteady wing deformations suppress the formation of a coherent leading edge vortex as flexibility increases. At lift and energy optimal aeroelastic conditions, there is no more leading edge vortex. Instead, vorticity accumulates in a bound shear layer covering the wing's upper surface from the leading to the trailing edge. Despite the absence of a leading edge vortex, the optimal deformable membrane wings demonstrate enhanced lift and energy efficiency compared to their rigid counterparts. It is possible that small bats rely on this mechanism for efficient hovering. We relate the force production on the wings with their deformation through scaling analyses. Additionally, we identify the geometric angles at the leading and trailing edges as observable indicators of the flow state and use them to map out the transitions of the flow topology and their aerodynamic performance for a wide range of aeroelastic conditions.

A Nodal-Lie-Group Beam Element for Absolute Nodal Coordinate Formulations

Abstract A new 12DOF beam element is proposed to simulate large deformation and large rotation based on the 24DOF absolute nodal coordinate formulation (ANCF) beam element proposed before. The centerline of the beam is interpolated by Hermite shape functions, and the frame of the beam is interpolated by linear shape functions. To reduce DOFs, the Lie-group method is used to normalize and orthogonalize the frame on each node of the beam. This way of using the Lie-group method keeps a linear relationship between the nodal vectors and shape functions and leads to the constant mass matrix and elastic tensors. Therefore, the generalized elastic and inertial forces do not require Gaussian integration at each time-step. To avoid singularity of the rotation, a relative rotation vector is adopted; correspondingly, the generalized-α integrator based on the Lie group is used to solve the dynamic equations. To improve the convergency speed and alleviate the shear locking and Poisson locking problems of this element, the assumed natural strain (ANS) method is adopted. To improve the calculational accuracy of axis stretching and torsion effects, the enhanced assumed strain (EAS) method is adopted. The formulas presented in this paper have been successfully tested in several static and dynamic examples of other ANCF beam elements and analytic solutions.

Study on Evaluation and Control Measures of Large Deformation of Soft Rock Tunnels Considering Unloading Physical Expansion

Study on Evaluation and Control Measures of Large Deformation of Soft Rock Tunnels Considering Unloading Physical Expansion

A Review of the Applications and Challenges of Dielectric Elastomer Actuators in Soft Robotics

As an electrically driven artificial muscle, dielectric elastomer actuators (DEAs) are notable for their large deformation, fast response speed, and high energy density, showing significant potential in soft robots. The paper discusses the working principles of DEAs, focusing on their reversible deformation under electric fields and performance optimization through material and structural innovations. Key applications include soft grippers, locomotion robots (e.g., multilegged, crawling, swimming, and jumping/flying), humanoid robots, and wearable devices. The challenges associated with DEAs are also examined, including the actuation properties of DE material, material fatigue, viscoelastic effects, and environmental adaptability. Finally, modeling and control strategies to enhance DEA performance are introduced, with a perspective on future technological advancements in the field.

Wireless Flexible Actuator Photoelectric Synergistically Driven for Environment Adaptability Crawling Robots.

Wirelessly driven flexible actuators are crucial to the development of flexible robotic crawling. However, great challenges still remain for the crawling of flexible actuators in complex environments. Herein, we reported a wireless flexible actuator synergistically driven by wireless power transmission (WPT) technology and near-infrared (NIR) light, which consists of a poly(dimethylsiloxane)-graphene oxide (PDMS-GO) composite layer, eutectic gallium-indium alloy (EGaIn), a PDMS layer, and a polyimide (PI) layer. By optimizing the parameters of EGaIn and the concentration of the PDMS-GO composite film, the actuator has excellent bending ability and blocking force under different conditions driven by photoelectronic synergy. In addition, we fabricated a flexible crawling robot with high environmental adaptability by adding crawling structures at both ends of the actuator, which causes a discrepancy in friction between the front and rear feet. The flexible crawling robot has high stability, large deformation, and excellent crawling ability for wirelessly crawling on a plane, slope, and plane with different roughnesses. This work provides an idea for the application of wireless robots in complex environments.

Zonal Characteristics of Collagen Ultrastructure and Responses to Mechanical Loading in Articular Cartilage.

The biomechanical properties of articular cartilage arise from a complex bioenvironment comprising hierarchically organised collagen networks within the extracellular matrix (ECM) that interact with the proteoglycan-rich interstitial fluid. This network features a depth-dependent fibril organisation across different zones. Understanding how collagen fibrils respond to external loading is key to elucidating the mechanisms behind lesion and managing degenerative conditions like osteoarthritis. This study employs polarisation-resolved second harmonic generation (pSHG) microscopy to quantify the ultrastructural organisation of collagen fibrils and their spatial gradient along the depth of bone-cartilage explants at a close-to-in vivo condition. By combining with in-situ loading, we examined the responses of collagen fibrils by quantifying changes in their principal orientation and degree of alignment. The spatial gradient and heterogeneity of collagen organisation were captured at high resolution (1 µm) along the longitudinal plane of explants (0.5 by 2 mm). Zone-specific ultrastructural characteristics were quantified to aid in defining zonal borders, revealing consistent zonal proportions with varying overall thicknesses. Under compression, the transitional zone exhibited the most significant re-organisation of collagen fibrils. It initially allowed large deformation through re-orientation of fibrils, which then tightened fibril alignment to prevent excessive deformation, indicating a dynamic adaptation mechanism in response to increasing strain levels. Our results provide comprehensive, zone-specific baselines of cartilage ultrastructure and micromechanics, crucial for investigating the onset and progression of degenerative conditions, setting therapeutic intervention targets, and guiding cartilage repair and regeneration efforts. STATEMENT OF SIGNIFICANCE: Achieved unprecedented quantification of the spatial gradient and heterogeneity of collagen ultrastructural organisation at a high resolution (1 µm) along the full depth of the longitudinal plane of osteochondral explants (500 by 2000 µm) in close-to-in vivo condition. Suggested new anatomical landmarks based on ultrastructural features for determining zonal borders and found consistent zonal proportions in explants with different overall thicknesses. Demonstrated that collagen fibrils initially respond by re-orientating themselves at low strain levels, playing a significant role in cartilage deformation, particularly within the transitional zone. At higher strain levels, more collagen fibrils changed their alignment, indicating a dynamic shift in the response mechanism at varying strain levels.

Large Deformation Behavior of Plane Periodic Truss Networks. Part 1. Closed-Form Solution for Single Node Cells

This article focuses on the derivation of explicit descriptions of networks in large deformation through the homogenization method of discrete media. Analytical models are established for the in-plane behavior of a planar periodic truss, whose cell contains a single node, as frequently encountered in practice. The cell is composed of bars that support only axial forces and are connected by perfect hinges. For the considered type of trusses, (given that the equilibrium conditions of the node and of the cell coincide) closed-form expressions for the local behaviour in the case of large deformations can be derived. This case makes it possible to combine the non-linearities arising from large deformations on the one hand and rheological characteristics on the other, and to compare their respective effects as a function of cell morphology. The results are illustrated by the shear and extension responses of specific trusses. The analysis is carried out for bars with stiffening, linear or softening behavior. The combination of the effects of geometrical non-linearities, rheological non-linearities and anisotropy results in particularly rich behaviors of the network.