Simulation Of Deformation Research Articles

The Practicality of Quality Assessment Metrics for Millimetre‐Scale Digital Image Correlation Speckle Patterns

ABSTRACTDigital image correlation (DIC), often used in multidisciplinary applications by nonexperts, relies heavily on the quality of a speckle pattern for accurate deformation tracking. Numerous metrics have been developed to assess speckle pattern quality and guide decision‐making in DIC postprocessing. This investigation considered the applicability of these metrics in the selection of an optimal speckling method for two‐dimensional DIC strain measurements, using the standard Brazilian tensile strength rock mechanics laboratory test as a case study. Four speckle patterning methods—spray paint, airbrush, stamp and laser engraving—were optimized to produce patterns of good visual quality for this specific DIC setup. Twenty specimens, five for each method, were prepared, and their speckle patterns were analysed using 10 published metrics. Each pattern was also deformed numerically to quantify the associated systematic and random errors. Overall, none of the 10 metrics demonstrated substantial agreement with the numerical experiment errors due to their failure to account for the confounding influence of pattern characteristics. Consequently, these tools are limited in their usefulness to evaluate the accuracy and reproducibility of speckle patterns with similar characteristics. Numerical simulation of pattern deformation is recommended as the most accurate resource for nonexpert DIC users to assess reproducibility and select optimal patterning methods in practical applications.

Investigation of Acid-Etching Evolution in Natural Fractures of Carbonate Reservoirs Under High Closure Stress

Summary The acid-etching evolution of local natural fractures in high-stress carbonate rocks is a complex, multifield coupled phenomenon, governed primarily by closure stress loading, acid flow, and mass transfer reaction. To unravel the characteristics of this evolution and the impact of closure stress and acid injection rate on acid-etching effectiveness, a set of numerical models that integrate fluid flow, chemical reaction, and mechanical deformation within local natural fractures is established, and numerical simulations of fracture deformation and fracture acid-etching are conducted. The results show that continuous closure stress loading fosters the emergence of dominant flow channels by means of acid flow and acid-rock reaction. These channels guide most of the acid flow, continuously dissolving and etching the fracture walls, ultimately forming channelized acid-etching fractures. When closure stress ranges between 10 MPa and 15 MPa, a coupling balance between high closure stress and flow reaction enables the acid-etching fractures to attain greater widths and flow channels, significantly enhancing their long-term conductivity and deformation resistance. As the acid injection rate increases, the dominant flow channels merge into a single channelized acid-etching fracture due to competitive propagation and preferential dissolution. The dominant flow channel expands both vertically and horizontally under the scouring effect of high injection rates, leading to an increase in both the width of the channelized acid-etching fracture channel and the overall acid-etching fracture width.

Intraoperative interaction modeling between surgical instruments and soft tissues in neurosurgery based on energy functions

A physical model of soft tissue that provides realistic and real-time haptic and visual feedback is crucial for neurosurgical procedures. This paper investigates the interaction between surgical instruments and soft brain tissue, proposing a soft tissue deformation simulation method based on the principle of energy minimization and constrained energy function. The model includes a permanent deformation energy function induced by friction and a volume preservation energy function to more accurately depict tissue response during procedures such as resection of convex meningiomas and evacuation of intracerebral hematomas. Experimental results show that the proposed method meets the requirements of neurosurgical simulation.

Accelerate Neural Subspace-Based Reduced-Order Solver of Deformable Simulation by Lipschitz Optimization

Reduced-order simulation is an emerging method for accelerating physical simulations with high DOFs, and recently developed neural-network-based methods with nonlinear subspaces have been proven effective in diverse applications as more concise subspaces can be detected. However, the complexity and landscape of simulation objectives within the subspace have not been optimized, which leaves room for enhancement of the convergence speed. This work focuses on this point by proposing a general method for finding optimized subspace mappings, enabling further acceleration of neural reduced-order simulations while capturing comprehensive representations of the configuration manifolds. We achieve this by optimizing the Lipschitz energy of the elasticity term in the simulation objective, and incorporating the cubature approximation into the training process to manage the high memory and time demands associated with optimizing the newly introduced energy. Our method is versatile and applicable to both supervised and unsupervised settings for optimizing the parameterizations of the configuration manifolds. We demonstrate the effectiveness of our approach through general cases in both quasi-static and dynamics simulations. Our method achieves acceleration factors of up to 6.83 while consistently preserving comparable simulation accuracy in various cases, including large twisting, bending, and rotational deformations with collision handling. This novel approach offers significant potential for accelerating physical simulations, and can be a good add-on to existing neural-network-based solutions in modeling complex deformable objects.

Simulation of deformation and flow of pulmonary acinus using morphing compared with self-similar deformation

AbstractIn previous studies of the flow inside the pulmonary acinus, the deformation of acinus was limited because a relatively simple deformation methods, such as self-similar deformation, is used. However, acinus deformation may be complex and heterogeneous. The purpose of this study is to evaluate the influence of the difference in wall deformation between the morphed model and the self-similar deformation model on flow field. The heterogeneous deformation achieved in this study is more actual by using the morphing technology that continuously changes from one shape to another. STAR-CCM + Ver. 13.06 (Siemens PLM Software) was used for numerical calculation, and the governing equations of working fluid are continuous equations and Navier–Stokes equations (NS equations). As a result, the differences in deformation influenced the formation of streamlines at the distal end of the alveolar regions. In the self-similar deformation model, the flow does not change throughout a cycle, whereas in the morphed model, the flow changes during a cycle. Graphic abstract

Large deformation simulation of uprooting of trees with complex root system architectures using material point method with embedded truss elements

Abstract Background and aims Urban trees in coastal cities like Hong Kong may suffer from an uprooting failure when subjected to extreme winds. A proper numerical model for tree uprooting simulation can help to select tree species or soil types that better resist uprooting failure. However, modeling tree uprooting is challenging as it is a cross-disciplinary problem involving complex root system architectures (RSAs) and large deformation of both roots and soils. This study aims to develop a hybrid numerical model that combines truss elements and material point method (MPM) to simulate the entire large-deformation uprooting process of trees with complex RSAs. Methods The tree uprooting model is developed by coupling truss elements in finite element method (FEM) with MPM. Laboratory pull-out tests using artificial roots and real root cuttings are adopted to validate the developed model. A comparative study is performed to investigate the difference between using complex and simplified RSAs in tree uprooting simulations. Results The developed model provides consistent predictions of peak load, critical displacement and failure mode when compared with results from laboratory tests. Moreover, the comparative study shows that the uprooting resistance obtained with a complex RSA is higher than that with a simplified RSA. The difference varies with the soil and root mechanical properties. Conclusion The developed hybrid model offers a novel way for simulating an entire tree uprooting process involving large deformations and complex RSAs. The study shows that using a simplified RSA to approximate the complex RSA might result in misleading failure modes.

Modification of the Johnson-Cook relationship for AZ31 magnesium alloy at high strain rates

The establishment of Johnson-Cook (J-C) constitutive model is essential for the numerical analysis of high-speed impact. In this work, Dynamic compression experiments of extruded AZ31 magnesium alloy at various temperatures (298 K, 373 K, 473 K, and 573 K) and strain rates (700 s−1, 1000 s−1, and 1300 s−1) were studied using split Hopkinson pressure bar (SHPB). Based on the true stress-strain curves of the alloy collected by the experimental process, the strain term and temperature term of the Johnson-Cook model were modified, and the modified J-C model parameters with the temperature of 573 K and strain rate of 1300 s−1 were applied for the finite element simulation of the high strain rate deformation of AZ31 magnesium alloy. The results show that the modified J-C model is much better in agreement with the experimental results than that of the original one, and further the modified J-C model can accurately predict the compressive deformation behavior of AZ31 magnesium alloy during dynamic loading.

Theoretical model construction and static performance analysis of multi-leaf journal foil bearings

Abstract Multi-leaf journal foil bearing (MLJFB) structures are complex, making performance prediction challenging, and the accurate prediction of gas film thickness and pressure distributions is crucial. In this study, COMSOL finite-element software was used to establish an initial foil assembly and structural deformation simulation model for an MLJFB with bump foils. Using MATLAB, a compressible gas lubrication model was established and solved using the finite volume method (FVM). Real-time data transfer between COMSOL and MATLAB enabled a fully coupled fluid-structure interaction simulation. This model meticulously accounts for the pre-tension force in the multi-leaf bearing assembly, contact friction between adjacent foils, and the interaction between the top foil and gas film pressure. The effects of journal movement distance, direction, and top foil overlapping ratio on the bearing capacity as well as the effects of different external load directions on the journal equilibrium position were analyzed based on this model. The results indicate that increasing the top foil overlapping ratio enhances the bearing capacity of the MLJFB. Furthermore, compared to the direction of the top foil overlap position, external loads applied in the direction of the top foil midpoint are more beneficial for bearing operational stability.

Design and construction of a custom implant of the temporomandibular joint produced by additive manufacturing in titanium alloy from computed tomography

Biomodels are physical reproductions of anatomical structures of regions or organs of the human body used for diagnosis and surgical planning. The use of tomographic images for generating 3D models and manufacturing of biomodels has been awakening a great interest in the medical area. It is possible, with the use of medical images, to generate representative computer models, thus enabling several simulations and biomechanical analysis of the region or organ of interest, aiming at the manufacture of customized prosthesis or orthesis. In this work we present the project of a customized implant of the TMJ, mechanically ordered and manufactured in titanium alloy by the additive manufacturing process of DMLS. Through the model created for the TMJ region, computer simulations of stresses and deformations were performed on the mandible virtually implanted in the patient, considering severe stresses of human chewing applied to the frontal teeth. With the data from the computer simulations the prosthesis was analyzed through a conventional analytical design process to verify the fatigue failure resistance. The implant was fabricated in titanium alloy by additive manufacturing and was realized physical simulations of the coupling of the prosthesis in the biomodel of the mandible fabricated by three-dimensional printing.

Molecular dynamics simulation of shock-induced plastic deformation and spallation behavior of Cu/Cu64Zr36 crystalline/amorphous composites

Molecular dynamics (MD) simulations were performed to study the shock-induced plastic deformation and spallation failure of Cu/Cu64Zr36 crystalline/amorphous composites with a pre-existing void. The results show that the pre-existing void collapses always perpendicular to the direction of the shock loading, regardless of whether the shock direction starts from the crystalline phase or the amorphous phase. The Cu/Cu64Zr36 composites are more prone to spallation failure when the shock starts from the Cu crystalline phase. The changes of dislocation density and shear transformation zone (STZ) activation are closely related to the magnitude and direction of shock velocity. When the shock velocity reaches 2.0 km/s, dislocations in the crystalline phase disappear, dislocation density is close to zero and STZs activate throughout the entire amorphous phase. In addition, regardless of the shock velocity and direction, no shear bands are generated in the Cu/Cu64Zr36 composites under shock loading, which is significantly different from the case of tensile loading.

Multi-phase-field lattice Boltzmann modeling and simulations of semi-solid simple shear deformation

Semi-solid deformation is a versatile phenomenon that occurs during the solidification of alloys. Semi-solid simple shear deformation is simulated using the multi-phase-field lattice Boltzmann (MPF-LB) method, which has been originally devised to capture polycrystalline solidification accompanied with melt flow and solid motion. MPF-LB simulations of semi-solid simple shear deformation, with variations in solid fractions, reveal the transition from a liquid-like behavior to a solid-like one. Especially, the shear band formed via dilatancy effects is thoroughly examined in the high solid fraction region. The relationship between grain rearrangement and mechanical behaviors during the formation process of the shear band is investigated in detail. In addition, the effect of domain size and initial grain arrangement on shear band formation is evaluated. Finally, the mechanism of shear band formation is clarified. The developed MPF-LB simulation method is promising for comprehensive evaluations of semi-solid deformation.

A foundational framework for the mesoscale modeling of dynamic elastomers and gels

Discrete mesoscale network models, in which explicitly modeled polymer chains are replaced by implicit pairwise potentials, are capable of predicting the macroscale mechanical response of polymeric materials such as elastomers and gels, while offering greater insight into microstructural phenomena than constitutive theory or macroscale experiments alone. However, whether such mesoscale models accurately represent the molecular structures of polymer networks requires investigation during their development, particularly in the case of dynamic polymers that restructure in time. We here introduce and compare the topological and mechanical predictions of an idealized, reduced-order mesoscale approach in which only tethered dynamic bonding sites and crosslinks in a polymer’s backbone are explicitly modeled, to those of molecular theory and a Kremer–Grest, coarse-grained molecular dynamics approach. We find that for short chain networks (∼12 Kuhn lengths per chain segment) at intermediate polymer packing fractions, undergoing relatively slow loading rates (compared to the monomer diffusion rate), the mesoscale approach reasonably reproduces the chain conformations, bond kinetic rates, and ensemble stress responses predicted by molecular theory and the bead–spring model. Further, it does so with a 90% reduction in computational cost. These savings grant the mesoscale model access to larger spatiotemporal domains than conventional molecular dynamics, enabling simulation of large deformations as well as durations approaching experimental timescales (e.g., those utilized in dynamic mechanical analysis). While the model investigated is for monodisperse polymer networks in theta-solvent, without entanglement, charge interactions, long-range dynamic bond interactions, or other confounding physical effects, this work highlights the utility of these models and lays a foundational groundwork for the incorporation of such phenomena moving forward.

Elastic properties and thermodynamic anomalies of supersolids

We study a supersolid in the context of a Gross-Pitaevskii theory with a nonlocal effective potential. We employ a homogenization technique which allows us to calculate the elastic moduli, supersolid fraction, and other state variables of the system. Our methodology is verified against numerical simulations of elastic deformations. We can also verify that the long-wavelength Goldstone modes that emerge from this technique agree with Bogoliubov theory. We find a thermodynamic anomaly that the supersolid does not obey the thermodynamic relation ∂P/∂V|N=−n(∂P/∂N|V), which we claim is a feature unique to supersolids. Published by the American Physical Society 2024

Fast and Compact Partial Differential Equation (PDE)-Based Dynamic Reconstruction of Extended Position-Based Dynamics (XPBD) Deformation Simulation

Dynamic simulation is widely applied in the real-time and realistic physical simulation field. How to achieve natural dynamic simulation results in real-time with small data sizes is an important and long-standing topic. In this paper, we propose a dynamic reconstruction and interpolation method grounded in physical principles for simulating dynamic deformations. This method replaces the deformation forces of the widely used eXtended Position-Based Dynamics (XPBD), which are traditionally derived from the gradient of the energy potential defined by the constraint function, with the elastic beam bending forces to more accurately represent the underlying deformation physics. By doing so, it establishes a mathematical model based on dynamic partial differential equations (PDE) for reconstruction, which are the differential equations involving both the parametric variable u and the time variable t. This model also considers the inertia forces caused by acceleration. The analytical solution to this model is then integrated with the XPBD framework, built upon Newton’s equations of motion. This integration reduces the number of design variables and data sizes, enhances simulation efficiency, achieves good reconstruction accuracy, and makes deformation simulation more capable. The experiment carried out in this paper demonstrates that deformed shapes at about half of the keyframes simulated by XPBD can be reconstructed by the proposed PDE-based dynamic reconstruction algorithm quickly and accurately with a compact and analytical representation, which outperforms static B-spline-based representation and interpolation, greatly shortens the XPBD simulation time, and represents deformed shapes with much smaller data sizes while maintaining good accuracy. Furthermore, the proposed PDE-based dynamic reconstruction algorithm can generate continuous deformation shapes, which cannot be generated by XPBD, to raise the capacity of deformation simulation.

Numerical simulation of thermal deformation of oil distribution sleeve based on heat transfer theory

Numerical simulation of thermal deformation of oil distribution sleeve based on heat transfer theory

Modeling wheeled locomotion in granular media using 3D-RFT and sand deformation

Modeling the wheel-soil interaction of small-wheeled robots in granular media is important for robot design and control. A wide range of applications, from earthmoving for construction and farming vehicles to navigating rough terrain for Mars rovers, motivate the need for a model that can predict the force response of a wheel and the terrain shape afterward. More importantly, the speed, accuracy, and generality of the model should be considered for real-world applications. In this paper, we offer a straightforward sand deformation simulator to simulate the soil surface and integrate it with 3D-RFT in order to capture the soil motion caused by the wheel. The proposed method is able to: (1) estimate three-dimensional interaction forces of arbitrarily shaped wheels traveling in granular media; (2) simulate the soil displacement from the trajectory; and (3) perform the force calculation in real-time at 60 Hz.

A physics-informed neural network for simulation of finite deformation in hyperelastic-magnetic coupling problems

A physics-informed neural network for simulation of finite deformation in hyperelastic-magnetic coupling problems

Meso-structure-Based Numerical Simulations of Deformation and Damage of Ti3AIC2/Al Composites by 3D Cylinder Model under Axial Compression

Meso-structure-Based Numerical Simulations of Deformation and Damage of Ti3AIC2/Al Composites by 3D Cylinder Model under Axial Compression

Effects of graphene reinforcement on morphology, thermophysical, and mechanical properties of polyvinyl alcohol and polyacrylamide in condensed phases

The subtle interplay of noncovalent interaction in enhancing the compatibility between the graphene-based material and the oligomers of polyvinyl alcohol (PVA) and polyacrylamide (PAM) in the solvent phase is unraveled within the framework of all-atom classical force field-based molecular dynamics (MD) simulations. The decomposition of binding free energy analysis demonstrates that the interaction between polymer segments and graphene (G)-surface crucially emanates from the van der Waals (vdW) interactions, while the adsorption of polymer chains on the graphene oxide (GO)-surface is influenced by vdW and electrostatic interactions. The influence of diverse factors including the strain rate, the size of the nanofiller, the number of oligomers, and the thermal quenching rate on controlling the morphology, mechanical, and thermophysical properties of the graphene-reinforced polymer nanocomposites are further explored. The uniaxial deformation simulations of the graphene-reinforced PVA and PAM matrices show that the interfacial mechanical strength is escalated for the G-PVA nanocomposite. The inclusion of graphene nanofiller reduces the polymer chain mobility and increases the intermolecular interaction, which in turn enhances the toughness of the graphene-polymer composites. Increasing the strain rate raises the yield strength and modulus, making the composites appear stronger and stiffer. As evidenced by the predicted glass transition temperature, the thermal stability of the PVA and PAM matrices is significantly improved by the graphene reinforcement.

Computer Simulation of Microstructure Development and Shape Deformation in Powder Metallurgy Process

Computer Simulation of Microstructure Development and Shape Deformation in Powder Metallurgy Process