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An algorithm of axisymmetric unbranched soft shells nonlinear dynamic behaviour problems solution is suggested in the work. The algorithm does not impose any restrictions on deformations or displacements range, material properties, conditions of fixing or meridian form of the structure. Mathematical statement of the problem is given in vector-matrix form and includes system of partial differential equations, system of additional algebraic equations, structure segments coupling conditions, initial and boundary conditions. Partial differential equations of motion are reduced to nonlinear ordinary differential equations using method of lines. Obtained equation system is differentiated by calendar parameter. As a result problem solution is reduced to solving two interconnected problems: quasilinear multipoint boundary problem and nonlinear Cauchy problem with right-hand side of a special form. Features of represented algorithm using in application to the problems of soft shells dynamics are revealed at its program realization and are described in the work. Three- and four-point finite difference schemes are used for acceleration approximation. Algorithm testing is carried out for the example of hinged hemisphere of neo-hookean material dynamic inflation. Influence of time step and acceleration approximation scheme choice on solution results is investigated.

The present study is focused on the constitutive modeling for the mechanical behavior of rubber reinforced with filler particles. A filler-dependent energy density function is proposed with all the continuum mechanics-based necessities of an effective hyperelastic material model. The proposed invariant-based energy function comprises a single set of material parameters for a material subjected to several modes of loading conditions. The model solution agrees well with existing experimental results. Later, the effect of varying concentrations of filler particles in the rubber matrix is also studied.

Elastomers are widely used in various engineering applications due to their huge elasticity and good dynamic behavior. One of the elastomeric elements is rubber blocks, which are used in many applications, such as vibration isolators, bumpers, shock absorbers, dampers, etc. In this research, the impact on the ride index due to the deflated state of the air spring with various kinds of hyperelastic materials is analyzed by the finite element method. The stress–energy function of rubber materials is first diagnosed, and Poisson's ratio defined the volumetric terms. The rubber isolator's stress is studied based on the finite element model, and the structure is improved. It is observed that for the deflated state of the air spring, laminated rubber isolation diminishes the muscular amount of structural responses compared to the conventional rubber base structures, and improves the ride comfort. This study would assist in doing finite element analysis of the secondary suspension system and other vibration-damping components. [ABSTRACT FROM AUTHOR]

This is the first part of a two-part article on a hyperelastic extended Kirchhoff–Love shell model with out-of-plane normal stress. We present the derivation of the new model, with focus on the mechanics of the out-of-plane deformation. Accounting for the out-of-plane normal stress distribution in the out-of-plane direction affects the accuracy in calculating the deformed-configuration out-of-plane position, and consequently the nonlinear response of the shell. The improvement is beyond what we get from accounting for the out-of-plane deformation mapping. By accounting for the out-of-plane normal stress, the traction acting on the shell can be specified on the upper and lower surfaces separately. With that, the new model is free from the "midsurface" location in terms of specifying the traction. We also present derivations related to the variation of the kinetic energy and the form of specifying the traction and moment acting on the upper and lower surfaces and along the edges. We present test computations for unidirectional plate bending, plate saddle deformation, and pressurized cylindrical and spherical shells. We use the neo-Hookean and Fung's material models, for the compressible- and incompressible-material cases, and with the out-of-plane normal stress and without, which is the plane-stress case. [ABSTRACT FROM AUTHOR]

Porous infill, rather than the solids, can provide high stiffness-to-weight ratio, energy absorption, thermal insulation, and many other outstanding properties. However, porous structure design to date have been majorly performed with topology optimization under small deformation assumption. The effect of porosity control under large deformation is not explored yet. Hence, this paper exploits the topological design method of porous infill structures under large deformational configuration. Specifically, the neo-Hookean hyperelasticity model is adopted to simulate the large structural deformation, and the adjoint sensitivity analysis is performed accordingly with the governing equation and constraint. The maximum local volume fractions before and after deformation are concurrently constrained and especially for the latter, the representative volume points (RVPs) are modeled and tracked for evaluating the local volume fractions subject to the distorted mesh configuration. The local volume constraints are then aggregated with the P-norm method for a global expression. Iterative corrections are made to the P-norm function to rigorously restrict the upper bound of the maximum local volume. Finally, several benchmark cases are investigated, which validate the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

• A total Lagrangian Galerkin free element method is proposed for finite deformation. • Hyperelastic materials are considered calculated by the Galerkin free element method. • 2D and 3D nonlinear problems are solved to verify the accuracy. • Favorable results can be obtained using the proposed method for the nearly incompressible materials. In this research, a total Lagrangian Galerkin free element method (GFrEM) is proposed for the analysis of finite deformation in hyperelastic materials. This method derives the total Lagrangian formulation using the initial configuration as the reference. The mechanical behavior of hyperelastic materials is modeled by the non-Hookean strain energy function. Since Lagrangian isoparametric elements are freely formed in GFrEM by collocation nodes with their surrounding nodes, intrinsic boundary conditions can be imposed simply as in the finite elements method. In addition, the Galerkin method was used to ensure the stability of the results when constructing the equations for each collocation node. The validity and convergence of the proposed method are verified by several two- and three-dimensional numerical examples that include bending, compression, and torsion of hyperelastic materials. The example of nearly incompressible material shows that GFrEM remains highly accurate even with large deformations where the FEM cannot converge. [ABSTRACT FROM AUTHOR]

• A robust beam element is developed based on the 3D exact deformation field. • The generalized hyperelastic Rivlin model is integrated into the FE model. • A general unit cell (UC) is designed to simulate all hexagonal lattice structures. • The geometrical parameters effect of UC on the mechanical properties are studied. • UC with a broad range of large and negative Poisson's ratios are studied. • The lattices under large deformation are analyzed using experiment and FE model. This paper addresses the intricate analysis of lattice structures, pivotal components in engineering applications, confronted by challenges arising from their diverse unit cells (UCs) and complex behavior across micromechanical and macro-scale dimensions. The present study deals with a comprehensive analysis of lattice structure with honeycomb and re-entrant auxetic unit cells under large deformation via both a robust finite element analysis (FEA) and experimental tests. The proposed FEA is developed based on the hyperelastic Mooney–Rivlin strain energy function and the novel exact motion field that can fully describe the projection of cross-section. The results demonstrate that mechanical parameters such as Young's modulus, Poisson's ratio, and shear modulus have significant nonlinear behaviors with respect to UC geometrical parameters that are crucial for optimization across varied operational conditions. Additionally, the lattices made of TPU material and fabricated by Fused Deposition Modeling are tested under three-point bending and compression considering contact interaction. The results reveal highly nonlinear responses due to instabilities in some links and material nonlinearity. Furthermore, the behavior of lattice structures is exceedingly dependent on the orientations and types of UCs. It also can be found that both of the proposed FEA and constitutive model are in good agreement with experimental data. [Display omitted] [ABSTRACT FROM AUTHOR]

Hold‐downs for mass timber construction Tall mass timber construction is gaining popularity in residential and non‐residential applications. The prospect of building larger timber structures creates structural challenges, amongst them being that lateral forces created by high winds and strong earthquakes are higher and create higher demands of "hold‐downs". These demands are multiple: high strength to resist loads, high stiffness to minimize deflections during wind events, as well as deformation compatibility to facilitate the desired rocking‐motion of the shear walls during an earthquake. Herein, the state of the art on hold‐down design for mass‐timber shear walls is summarizes and recent research on three innovative hold‐down solutions is provided: i) internal‐perforated‐steel‐plates fastened with self‐drilling dowels, ii) hyperelastic rubber pads with steel rods, and iii) solutions with self‐tapping screws. [ABSTRACT FROM AUTHOR]

This study analyses the energy absorption and stiffness behaviour of 3D-printed supportless, closed-cell lattice structures. The unit cell design is bioinspired by the sea urchin morphology having organism-level biomimicry. This gives rise to an open-cell lattice structure that can be used to produce two different closed-cell structures by closing the openings with thin or thick walls, respectively. In the design phase, the focus is placed on obtaining the same relative density with all structures. The present study demonstrates that closure of the open-cell lattice structure enhances the mechanical properties without affecting the functional requirements. Thermoplastic polyurethane (TPU) is used to produce the structures via additive manufacturing (AM) using fused filament fabrication (FFF). Uniaxial compression tests are performed to understand the mechanical and functional properties of the structures. Numerical models are developed adopting an advanced material model aimed at studying the hysteretic behaviour of the hyperelastic polymer. The study strengthens design principles for closed-cell lattice structures, highlighting the fact that a thin membrane is the best morphology to enhance structural properties. The results of this study can be generalised and easily applied to applications where functional requirements are of key importance, such as in the production of lightweight midsole shoes. [ABSTRACT FROM AUTHOR]

Presented herein is a numerical variational approach to the two-dimensional (2D) incompressible nonlinear elasticity. The governing equations are derived based upon the minimum total energy principle by considering the displacement and a pressure-like field as the two independent unknowns. The tensor equations are replaced by equations in a novel matrix-vector form. The proposed solution method is based upon the variational differential quadrature (VDQ) method and a transformation procedure. Using the introduced VDQ-based approach, the energy functional is precisely discretized in a direct way. Being locking-free, simple implementation and computational efficiency are the main features of this method. Also, it is free from numerical artifacts and instabilities. Some important problems of 2D incompressible elasticity are addressed to test the method. It is revealed that it can be efficiently utilized to capture the large strains of incompressible solids. [ABSTRACT FROM AUTHOR]

The present article investigates an elastic instability phenomenon for internally pressurized spherical thin balloons and thin cylindrical tubes composed of incompressible hyperelastic material. A mathematical model is formulated by proposing a new strain energy density function. In the family of limited elastic materials, many material models exhibit strain-stiffening. However, they fail to predict severe strain-stiffening in a moderate range of deformations in the stress-strain relations. The proposed energy function contains three material parameters and shows substantially improved stain stiffening properties than the limited elastic material models. The model is further applied to explore the elastic instability phenomenon in spherical and cylindrical shells. The findings are compared with other existing models and validated with experimental results. The model shows better agreement with experimental results and exhibits a substantial strain-stiffening effect than the current models.

Uncertainty in the microstructures has a significant influence on the material properties. The microstructural uncertainty arises from the fluctuations that occur during thermomechanical processing and can alter the expected material properties and performance by propagating over multiple length scales. It can even lead to the material failure if the deviations in the critical properties exceed a certain limit. We introduce a linear programming (LP) based method to quantify the effects of the microstructure uncertainty on the desired material properties of the titanium-7 wt % aluminum alloy, which is a candidate material for aerospace applications. The microstructure is represented using the orientation distribution function (ODF) approach. The LP problem solves for the mean values and covariance of the ODFs that maximize a volume-averaged linear material property. However, the analytical procedure is not applicable for maximizing nonlinear material properties where microstructural uncertainties are present. Therefore, an artificial neural network based sampling method is developed to estimate the mean values and covariance of the ODFs that satisfy design constraints and maximize the volume-averaged nonlinear material properties. A couple of other design problems are also illustrated to clarify the applications of the proposed models for both linear and nonlinear properties. [ABSTRACT FROM AUTHOR]

This work consists of a review of a triangular Finite Element based on a six-parameter shell. constructed with initially flat elements and only the addition of sti ffness associated to the drilling D.O.F. as an artificial numerical factor. and verification of the necessary amount of integration points along the thickness and the surface to perform numerical integration and achieve equilibrium. With methodology based on integration points sets combinations. with 11 surface and 10 thickness gauss points sets. this paper determines if the surface integration points set proposed by the original authors is the minimum necessary to have a good accuracy of numerical results. The present work analyses the minimum number of integration points along the thickness. not mentioned by the original authors. The results are verified based in the displacement field. A Ciarlet-Simo neo-Hookean hyperelastic material is considered iii the constitutive equations. Rotations are treated by Euler-Rodrigues formula in a pure lagrangian way. The results show that the surface set of integration points suggested by the original authors is adequate and that integration along the thickness requires only 2 points to correctly represent the displacement field. [ABSTRACT FROM AUTHOR]

The article deals with the mechanical tensile tests of the hyperelastic materials and its mechanical properties estimation using embedded magnetic microwires. Hyperelastic materials are specific because of the elasticity, which means that they return to their original shape after the forces have been removed. The article processes the issue of the structural analysis of the hyperelastic materials, where the methodology for hyperelastic materials laws together with its implementation in the Creo-Simulate software is described. After the comparison of the simulation results with the experimental results a very good compliance was achieved. The created methodology together with the application of the tensile stress sensors based on the magnetic microwires embedded directly in the conveyor belts mean a significant improvement of the manufacturing and operation of the conveyor belts.

This study describes the basic design, material selection, fabrication, and evaluation of soft pneumatic actuators (SPA) for lower-limb rehabilitation compression therapy. SPAs can be a promising technology in proactive pressure delivery, with a wide range of dosages for treating venous-related diseases. However, the most effective design and material selection of SPAs for dynamic pressure delivery have not been fully explored. Therefore, a SPA chamber with two elastomeric layers was developed for this study, with single-side inflation. The 3D deformation profiles of the SPA chamber using three different elastomeric rubbers were analyzed using the finite element method (FEM). The best SPA-compliant behavior was displayed by food-grade silicone A10 Shore with a maximum deformation value of 25.34 mm. Next, the SPA chamber was fabricated using A10 Shore silicone and experimentally validated. During the simulation in FEM, the air pressure was applied on the inner wall of the chamber (i.e., the affected area). This is to ensure the applied pressure was evenly distributed in the inner wall while the outer wall of the chamber remained undeformed for all compression levels. During the inflation process, pressure will be applied to the SPA chamber, causing exerted pressure on the skin which is then measured for comparison. The simulation and experimental results show an excellent agreement of pressure transmission on the skin for the pressure range of 0–120 mmHg, as depicted in the Bland–Altman plots. The findings exhibited promising results in the development of the SPA chamber using low-cost and biocompatible food-grade silicone.

Introduction: In an effort of gaining a better understanding of the lens mechanics, ex vivo lenses samples are often used. Yet, ex vivo tissue might undergo important postmortem changes depending on the unavoidable preservation method employed. The purpose of this study was to assess how various storage conditions and the removal of the lens capsule affect the mechanical properties of ex vivo porcine lens samples., Methods: A total of 81 freshly enucleated porcine eyes were obtained and divided into six groups and preserved differently. In the first three groups, the lens within the intact eye was preserved for 24 h by: (i) freezing at -80°C (n = 12), (ii) freezing at -20°C (n = 12), and (iii) refrigeration at +8°C (n = 12). In the remaining groups, the lenses were immediately extracted and treated as follows: (iv) kept intact, no storage (n = 12), (v) decapsulated, no storage (n = 21), and (vi) immersed in Minimum Essential Medium (MEM) at +8°C (n = 12) for 24 h. Frozen lenses were thawed at room temperature. Each lens was compressed between two glass lamella and subjected, first to a period of relaxation during which the compression force was recorded and second to an oscillating micro-compression while the deformation was recorded with a total of 256 subsequent B-scans via optical coherence tomography. The corresponding axial strain was retrieved via phase-sensitive image processing and subsequently used as input for an inverse finite element analysis (iFEA) to retrieve the visco-hyperelastic material properties of the lenses., Results: After freezing at temperatures of -80°C and -20°C, the cortical strains increased by 14% ( p = 0.01) and 34% ( p < 0.001), and the nuclear strains decreased by 17% ( p = 0.014) and 36% ( p < 0.001), compared to the lenses tested immediately after postmortem, respectively. According to iFEA, this resulted from an increased ratio of the nuclear: cortical E-modulus (4.06 and 7.06) in -80°C and -20°C frozen lenses compared to fresh lenses (3.3). Decapsulation had the largest effect on the material constant C 10 , showing an increase both in the nucleus and cortex. Preservation of the intact eye in the refrigerator induced the least mechanical alterations in the lens, compared to the intact fresh condition., Discussion: Combining iFEA with optical coherence elastography allowed us to identify important changes in the lens mechanics induced after different preserving ex vivo methods., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Tahsini, Gil and Kling.)

No unified stress-based criterion exists, in the literature, for predicting the rupture of hyperelastic materials subjected to mutiaxial loading paths. This paper aims to establish a generalized rupture criterion under plane stress loading for elastomers. First, the experimental set up, at breaking, including various loading modes, is briefly described and commented. It consists of uniaxial tests, biaxial tests and pure shear tests, performed on different rubbers. The used vulcanizate and thermoplastic rubber materials are a Natural Rubber (NR), a Styrene Butadiene Rubber (SBR), a Polyurethane (PU) and a Thermoplastic elastomer (TPE). Then, we have investigated a new theoretical approach, based upon the principal stresses, to establish a failure criterion under quasi-static loadings. Thus, we have proposed a new analytical model expressed as a function of octahedral stresses. Quite good agreement is highlighted when comparing the ultimate stresses, at break, between the experimental data and the prediction of the proposed criteria using our rubber-like materials. [ABSTRACT FROM AUTHOR]

In this article, a new solution approach is developed to numerically compute large deformations of 3D hyperelastic solids based on the compressible nonlinear elasticity. The governing equations are derived by the minimum total potential energy principle, and the Neo-Hookean model is used for the hyperelastic character of material. One of the key novelties of the work is its formulation in which the tensor form of equations is replaced by an efficient matrix–vector form that can be readily utilized in the coding process. Moreover, the variational differential quadrature technique is adopted to arrive at the discretized governing equations in a direct way. Simple implementation, fast convergence rate, and computational efficiency are the main advantages of present approach. Through some examples, the accuracy and effectiveness of the proposed numerical approach are revealed. [ABSTRACT FROM AUTHOR]

In this paper, we present a computationally efficient cellular mathematical model that accounts for the boundary collective behavior of a cell group by hepatocyte growth factor. The large cell group is modeled using continuum-based finite elements with incompressible hyperelastic materials for the nonlinear elastic behaviors. The total Lagrangian formulation is used enabling for large deformations, and the explicit time integration scheme without the Newton-Raphson iterative solution required for a time step is adopted to model the dynamics of the collective cell migration. With the explicit time integration and low order finite elements under the total Lagrangian framework, the proposed model is much computationally efficient for modeling the dynamic mechanical behavior of a cell colony. Detailed comparison to the experimental data shows that the proposed mathematical model provides a quantitatively accurate description of the collective cell motion in three different concentrations of hepatocyte growth factor. [ABSTRACT FROM AUTHOR]

This paper presents a method for determining material constants of hyperelastic material used for building the soft robotic actuators. Sixty testpieces were made of silicone rubber with a shore A hardness from 20 A to 45 A. Each of them was then subjected to the uniaxial tensile test to obtain the stress–strain relationship, which is a key factor to evaluate the compatibility of the common six forms of strain energy density function for hyperelastic material. The sum of square error was used to determine the most relevant constitutive models, which are Ogden third order, Polynomial second order, and Yeoh, as well as parameter values of the corresponding materials. To analyze the appropriateness of these models for computation, six pneumatic soft actuators were built from materials with different hardness and tested for various pressures. From the simulation and experimental results, the model Yeoh has yielded the highest accuracy. This outcome forms a firm basis for the determination of suitable material in the computation and simulation of the pneumatic soft actuator. Besides, the obtained experimental results in this paper could be included in the database of hyperelastic material with different hardness for further simulation in the related field. [ABSTRACT FROM AUTHOR]

Hyperelastic constitutive laws in biomechanics are used to model soft tissues, and material model parameters are often determined by performing curve fitting on data from uniaxial or biaxial tensile tests. The strain energy function of the applied constitutive law must to be energetically stable; however, this condition is not inherently provided by most currently available models. This study provides a procedure to determine stable strain energy functions in a biaxial strain space based on either uniaxial or biaxial tensile tests. Instead of conservative, strain-independent conditions, a stability region is defined in the strain space based on the sample's tensile tests, thus allowing optimisation within a wider parameter space, resulting in better approximations. An extension of the Levenberg–Marquardt algorithm incorporating user-defined stability constraints is proposed, and the constrained optimisation algorithm is applied to isotropic and anisotropic models. The uniqueness of solutions of the Fung model is also discussed. The material model parameters of stable solutions for soft tissue measurements from various literature sources are determined to demonstrate the proposed procedure. Applying appropriate constraints in the optimisation algorithm resulted in stable and physically permissible constrained solutions for the strain energy function, in contrast to the results of most unconstrained optimisation cases. [ABSTRACT FROM AUTHOR]

Chemo-mechanical transduction is one of the key mechanisms that has formed the basis for designing bio-inspired self-driven synthetic systems from soft materials. Polymer hydrogels that use Belousov–Zhabotinsky (BZ) reaction are a unique class of dynamical reaction–diffusion (RD) systems that can continuously transduce internal chemical energy, from the reaction, to produce sustained mechanical work. In particular, BZ gels represent a complex nonlinear chemo-mechanical system, wherein, the autocatalytic oscillatory BZ reaction drives the rhythmic mechanical deformations through polymer-solvent inter–diffusion. The objective of our work is to develop a standardized finite element (FE) framework for chemically driven active hydrogels that captures nonlinear elastic deformations with limited chain extensibility. The distinguishing feature of our approach is that, unlike other approaches, it combines reaction kinetics, solvent transport, elastodynamics of the polymeric network, and polymer-solvent friction under a unified FE framework. Moreover, we adapt our approach to a specific case of BZ gels and capture their swelling-deswelling characteristics. We first implement our FE framework in MATLAB that subsequently, forms the basis for constructing a three-dimensional user element subroutine (3D-UEL) in ABAQUS. Ultimately, through our simulations, we are able to capture all the essential features of BZ gels that includes chemically driven mechanical deformations. In addition, we also demonstrate that our 3D-UEL efficiently captures the chemo-mechanical response of "stent-shaped" BZ gels–a non-standard 3D geometry. In essence, our FE approach not only allows us to simulate BZ gels but also provides a template for other active, dynamical, RD-based systems, driven by chemo-mechanical transduction, irrespective of internal or external mechanisms. • Finite-element scheme for active/inactive gels driven by chemo-mechanical transduction • 3D scheme integrates two-fluid model with reaction kinetics to capture interdiffusion • Describes dynamics of Belousov-Zhabotinsky (BZ) gels, and hydrogels in limiting case • 3D-UEL framework for self-oscillating BZ gels adaptable to active/inactive hydrogels • Demonstrates swelling-deswelling response of a non-standard stent-like BZ gel domain [ABSTRACT FROM AUTHOR]

A novel method is considered to evaluate the tensile deformation and stress of hyperelastic material by indentation method, the feasibility of which is on the basis of nonlinearity of hyperelastic materials. Under a tensile deformation, the instantaneous mechanical property shows an anisotropic character such that the contact region is elliptic rather than round. In order to capture the contact image, the traditional indentation device is upgraded with a special optical system. Besides, the spherical indentation experiment is conducted on the uniaxially stretched silica gel sample. The theoretical predictions and the experimental results show a good agreement with the difference from each other by less than 14%, that further validates the reliability of the transparent indentation method in spite of its insensitivity to the initial deformation. The aim of this paper is not only to evaluate the tensile deformation and stress of hyperelastic material but also to explore a new application domain of indentation method.

Recently, the application of non-steel materials in ships and offshore plants is increasing because of the development of various nonlinear materials and the improvement of performance. Especially, hyper-elastic materials, which have a nonlinear stress-strain relationship, are used mainly in marine plant structures or ships where impact relaxation, vibration suppression, and elasticity are required, while elasticity must be maintained, even under high strain conditions. In order to simulate and evaluate the behavior of the hyperelastic material, it is very important to select an appropriate material model according to the strain of the material. This study focused on the selection of material models for hyperelastic materials, such as rubber used in the marine and offshore fields. Tension and compression tests and finite element simulations were conducted to compare the accuracy of the nonlinear material models due to variations in the stretch ratio of hyper-elastic material. Material coefficients of nonlinear material models are determined based on the curve fitting of experimental data. The results of this study can be used to improve the reliability of nonlinear material models according to stretch ratio variation.

Rubber is one of the most important materials of modern industry and have a wide range of usage owing to a number of superior properties. In this study, the mechanical behaviour of the metal-rubber combination pulley part transferring motion in the engine through the timing belt was examined by the finite element method, confirmed experimentally, and optimized. Uniaxial tension and pure shear tests were carried out physically to develop a hyperelastic material model. 3 parameter Mooney-Rivlin hyperelastic material constants were calculated by using force-elongation values obtained from uniaxial tension and, pure shear tests. Afterwards, pulley geometry was modelled, and displacements, stresses, reaction moments were examined under various torsional loadings. To confirm the accuracy of the pulley analysis, a servomotor driven pulley torsion testing machine was designed and manufactured. Then, torque and angle values were measured by testing the pulley parts at the same torsional angles. By this study, it was proven that mechanical behaviour of pulley can be expressed numerically. After validation of the material model and the results obtained using analysis method, the pulley geometry was further improved the stress levels on the rubber material were reduced 28% under the same loading conditions by using optimization tools. [ABSTRACT FROM AUTHOR]

The article deals with the mechanical tensile tests of the hyperelastic materials and its mechanical properties estimation using embedded magnetic microwires. Hyperelastic materials are specific because of the elasticity, which means that they return to their original shape after the forces have been removed. The article processes the issue of the structural analysis of the hyperelastic materials, where the methodology for hyperelastic materials laws together with its implementation in the Creo-Simulate software is described. After the comparison of the simulation results with the experimental results a very good compliance was achieved. The created methodology together with the application of the tensile stress sensors based on the magnetic microwires embedded directly in the conveyor belts mean a significant improvement of the manufacturing and operation of the conveyor belts. [ABSTRACT FROM AUTHOR]

The expensive nature of currently used materials in the soft robotic industry demands the consideration of alternative materials for fabrication. This work investigates the performance of RTV-2 grade silicone rubber for fabrication of a soft actuator. Initially, a cylindrical actuator is fabricated using this material and its performance is experimentally assessed for different pressures. Further, parametric variations of the effect of wall thickness and inflation pressure are studied by numerical methods. Results show that, both wall thickness and inflation pressure are influential parameters which affect the elongation behaviour of the actuator. Thin (1.5 mm) sectioned actuators produced 76.97% more elongation compared to thick sectioned, but the stress induced is 89.61 % higher. Whereas, the thick sectioned actuator (6 mm) showed a higher load transmitting capability. With change in wall thickness from 1.5 mm to 6 mm, the elongation is reduced by 76.97 %, 38.35 %, 21.05 % and 11.43 % at pressure 100 kPa, 75 kPa, 50 kPa and 25 kPa respectively. The induced stress is also found reduced by 89.61 %, 86.66 %, 84.46 % and 68.68 % at these pressures. The average load carrying capacity of the actuator is found to be directly proportional to its wall thickness and inflation pressure. [ABSTRACT FROM AUTHOR]

In this paper, a novel higher stabilization-free virtual element method is proposed for compressible hyper-elastic materials in 2D. Different from the most traditional virtual element formulation, the method does not need any stabilization. The main idea is to modify the virtual element space to allow the computation of a higher-order polynomial L 2 projection of the gradient. Based on that the stiffness matrix can be obtained directly which greatly simplifies the analysis process, especially for nonlinear problems. Hyper-elastic materials are considered and some benchmark nonlinear problems are solved to verify the capability and accuracy of the stabilization-free virtual element method. [ABSTRACT FROM AUTHOR]

This paper presents a fully coupled fluid-structure interaction (FSI) simulation model of a soft pneumatic actuator (SPA). Previous research on modelling and simulation of SPAs mostly involves finite element modelling (FEM), in which the fluid pressure is considered as pressure load uniformly acting on the internal walls of the actuator. However, FEM modelling does not capture the physics of the fluid flow inside an SPA. An accurate modelling of the physical behaviour of an SPA requires a two-way FSI analysis that captures and transfers information from fluid to solid and vice versa. Furthermore, the investigation of the fluid flow inside the flow channels and chambers of the actuator are vital for an understanding of the fluid energy distribution and the prediction of the actuator performance. The FSI modelling is implemented on a typical SPA and the flow behaviour inside the actuator is presented. Moreover, the bending behaviour of the SPA from the FSI simulation results is compared with a corresponding FEM simulation.

The prevention, control and treatment of cerebral aneurysm (CA) has become a common concern of human society, and by simulating the biomechanical environment of CA using finite element analysis (FEA), the risk of aneurysm rupture can be predicted and evaluated. The target models of the current study are mainly idealized single-layer linear elastic cerebral aneurysm models, which do not take into account the effects of the vessel wall structure, material constitution, and structure of the real CA model on the mechanical parameters. This study proposes a reconstruction method for patient-specific trilaminar CA structural modeling. Using two-way fluid-structure interaction (FSI), we comparatively analyzed the effects of the differences between linear and hyperelastic materials and three-layer and single-layer membrane structures on various hemodynamic parameters of the CA model. It was found that the numerical effects of the different CA membrane structures and material constitution on the stresses and wall deformations were obvious, but does not affect the change in its distribution pattern and had little effect on the blood flow patterns. For the same material constitution, the stress of the three-layer membrane structure were more than 10.1% larger than that of the single-layer membrane structure. For the same membrane structure, the stress of the hyperelastic material were more than 5.4% larger than that of the linear elastic material, and the displacement of the hyperelastic material is smaller than that of the linear elastic material by about 20%. And the maximum value of stress occurred in the media, and the maximum displacement occurred in the intima. In addition, the upper region of the tumor is the maximum rupture risk region for CA, and the neck of the tumor and the bifurcation of the artery are also the sub-rupture risk regions to focus on. This study can provide data support for the selection of model materials for CA simulation and analysis, as well as a theoretical basis for clinical studies and subsequent research methods., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Fan, Zhang, Zheng, Li, Wang, He, Xue, Chen, Wu, Zhao and Wang.)

Volume change and large deformation occur in different solid and semi-solid foods during processing, e.g., shrinkage of fruits and vegetables during drying and of meat during cooking, swelling of grains during hydration, and expansion of dough during baking and of snacks during extrusion and puffing. In addition, food is broken down during oral processing. Such phenomena are the result of complex and dynamic relationships between composition and structure of foods, and driving forces established by processes and operating conditions. In particular, water plays a key role as plasticizer, strongly influencing the state of amorphous materials via the glass transition and, thus, their mechanical properties. Therefore, it is important to improve the understanding about these complex phenomena and to develop useful prediction tools. For this aim, different modelling approaches have been applied in the food engineering field. The objective of this article is to provide a general (non-systematic) review of recent (2005–2021) and relevant works regarding the modelling and simulation of volume change and large deformation in various food products/processes. Empirical- and physics-based models are considered, as well as different driving forces for deformation, in order to identify common bottlenecks and challenges in food engineering applications.