Deformation Transfer Research Articles

A novel hybrid PD-FEM-FVM approach for simulating hydraulic fracture propagation in saturated porous media

To enhance the computational efficiency of fluid–solid coupling in peridynamics (PD), a hybrid modeling approach based on the classical Biot theory is proposed for simulating hydraulic crack propagation in saturated porous media. The deformation and damage of solids are described by the coupling of the finite element method (FEM) and PD. Based on Darcy’s law, the finite volume method (FVM) is used to describe fluid seepage and calculate pore water pressure. The mutual transfer of fluid pressure and solid deformation is realized through the transition layer between the solid layer and the fluid layer. Firstly, the effectiveness of the proposed method is verified by a porous media seepage simulation example. Secondly, the ability and efficiency of this method to simulate crack propagation in saturated porous media are verified by several examples of hydraulic fracturing of rock with a single pre-existing crack. Finally, the synchronous hydraulic fracturing process of rock with double cracks is simulated. The ability of this method to simulate the simultaneous propagation of multiple fractures in the rock under fluid–solid coupling is further illustrated. The aforementioned studies demonstrate that the novel hybrid PD-FEM-FVM approach not only ensures computational accuracy and effectiveness but also significantly enhances computational efficiency.

Research on damage characteristics and contact interface evolution behavior of double-block ballastless track considering tunnel floor heave

Excessive railway tunnel floor heave (TFH) will reduce the durability of the track structure and jeopardize train operation safety. The TFH characteristics were fitted into cosine and bilinear curves according to the monitoring data. A nonlinear failure analysis model of double-block ballastless track under TFH was established. The deformation transfer law, structural damage mechanism and the interlayer bonding interface failure evolution of the track structure under different TFH characteristics were explored. The results show that the deformation of TFH can be well mapped to the track. The amplitude transfer ratio is less than 100 %. The maximum wavelength transfer ratio under the cosine and bilinear TFH is 129.3 % and 127.5 %, respectively. To avoid the damage of track structure, when the wavelength is 10 m, the amplitude of cosine and bilinear TFH should be controlled at 2.5 mm and 0.5 mm respectively. When the wavelength is greater than 10 m, the amplitude can be appropriately increased. To avoid interlayer bonding cracking, the cosine and bilinear amplitudes with a wavelength of 10 m should be controlled at 5 mm and 1.5 mm, respectively. The track-tunnel interlayer debonding failure under the cosine curve occurs at the edge of the TFH, while the bilinear curve occurs at the center and edge of the TFH. The gaps under the cosine and bilinear TFH exhibit double-peak and multi-peak shapes, respectively. This study can provide theoretical guidance for controlling the performance degradation of track structure caused by TFH.

Hierarchical Spherical Cross‐Parameterization for Deforming Characters

AbstractThe demand for immersive technology and realistic virtual environments has created a need for automated solutions to generate characters with morphological variations. However, existing approaches either rely on manual labour or oversimplify the problem by limiting it to static meshes or deformation transfers without shape morphing. In this paper, we propose a new cross‐parameterization approach that semi‐automates the generation of morphologically diverse characters with synthesized articulations and animations. The main contribution of this work is that our approach parameterizes deforming characters into a novel hierarchical multi‐sphere domain, while considering the attributes of mesh topology, deformation and animation. With such a multi‐sphere domain, our approach minimizes parametric distortion rates, enhances the bijectivity of parameterization and aligns deforming feature correspondences. The alignment process we propose allows users to focus only on major joint pairs, which is much simpler and more intuitive than the existing alignment solutions that involve a manual process of identifying feature points on mesh surfaces. Compared to recent works, our approach achieves high‐quality results in the applications of 3D morphing, texture transfer, character synthesis and deformation transfer.

Optimization of the deformation transfer mechanism: analysis of spring hanging point and structural parameters

Abstract This paper thoroughly investigates the impact of the spring hanging point’s positioning and structural parameters on the multi-mode robot’s performance within the deformable transfer domain mechanism. The spring hanging point is a pivotal design element, significantly influencing the robot’s extensive deformation, efficiency, and adaptability. Operating as a cross-domain entity between land and air, the robot effectuates the transition between ground and aerial domains via the deformation trans-domain mechanism, executing a spectrum of intricate tasks. The precise placement of the spring hanging point and variations in structural parameters directly shape the robot’s performance metrics, encompassing deformation speed, stability, and energy utilization. Through elucidating fundamental principles, deliberating spring hanging point location choices, suggesting optimization methodologies, scrutinizing structural parameter impact on performance, and validating via dynamic modeling, this paper offers theoretical underpinnings for deforming domain mechanism design and enhancement, thereby elevating the robot’s overall efficacy.

TailorMe: Self‐Supervised Learning of an Anatomically Constrained Volumetric Human Shape Model

AbstractHuman shape spaces have been extensively studied, as they are a core element of human shape and pose inference tasks. Classic methods for creating a human shape model register a surface template mesh to a database of 3D scans and use dimensionality reduction techniques, such as Principal Component Analysis, to learn a compact representation. While these shape models enable global shape modifications by correlating anthropometric measurements with the learned subspace, they only provide limited localized shape control. We instead register a volumetric anatomical template, consisting of skeleton bones and soft tissue, to the surface scans of the CAESAR database. We further enlarge our training data to the full Cartesian product of all skeletons and all soft tissues using physically plausible volumetric deformation transfer. This data is then used to learn an anatomically constrained volumetric human shape model in a self‐supervised fashion. The resulting TailorMe model enables shape sampling, localized shape manipulation, and fast inference from given surface scans.

A multi-responsive actuator with sensing capability based on poly (N-isopropyl acrylamide)/poly (sodium acrylate) Janus hydrogels

A Janus hydrogel composed of temperature-responsive poly (N-isopropyl acrylamide) (PNIPAM) and pH-responsive poly (sodium acrylate) (PSA) was fabricated from inexpensive monomers using a facile synthesis route. The asymmetric swelling between PNIPAM and PSA in different media and at different temperatures makes the Janus hydrogels have a multi-stimuli response, meanwhile, the interpenetrating layer between PNIPAM and PSA indicated a good interfacial adhesion for easy transfer of internal stress and deformation. Thus, the Janus hydrogels exhibited excellent advantages in actuator/sensor engineering, demonstrating the potential to grip and release objects in toxic media, encrypt, monitor and control safety in chemical production, and alert temperature of flammable and explosive solvents. In addition, the features of the Janus hydrogels incorporated with carbon nanotubes, such as the high sensitivity, large stretchability, and rapid and linear response, enabled their application as strain sensors for wearable technologies in the recognition of body movement and health detection.

Preliminary study on the water film at the soil–structure interface under cyclic loading

Offshore foundations usually experience long-term cyclic loading, where the weakly bound water at the soil-structure interface can be transformed into free water. The free water enriched at the soil–structure interface would influence the mechanical characteristics of the soil near the interface, weakening the interface strength and posing a significant threat to the safety and stability of offshore foundations. This study proposed a novel concept, i.e. the characteristic water film thickness, to quantify the enrichment degree of water film at the soil–structure interface under cyclic loading. A series of cyclic shearing tests were carried out by using self-developed cyclic loading equipment combined with a small constant temperature centrifuge. The influence of different clay and salt contents on the characteristic water film thickness was investigated and analyzed. It was found that both the kaolin and salt contents significantly impacted the characteristic water film thickness, where it was positively correlated with the kaolin content while negatively correlated with the salt content. The research outcome enriched the understanding of the weakening mechanism underlying the load and deformation transfer between soil–structure interface.

Study on structural damage mechanisms and defence of rectangular closed-section simplified hull girders with thinner plates under near-field underwater explosions

Understanding the damage mechanisms of typical ship structures under fatal underwater explosion loads is crucial for developing effective defensive measures. To provide references for enhancing the survivability of ships, this paper conducts analyses of the damage mechanisms of simplified hull girders (SHGs) using a combination of experimental and simulation methods, and proposes targeted structural improvements. Initially, two types of thin-walled rectangular closed-section SHGs are subjected to near-field underwater explosion experiments. Corresponding simulation models are established, and the validity of the computational results is verified. The progressive damage processes of SHGs in hogging and sagging are examined from a structural perspective. Furthermore, the thin-walled plate deformation transfer processes are analyzed. Finally, based on the analyzed damage mechanisms, targeted defensive structures for overall damage are designed. The study results show that enhancing the anti-deformation capability of the upper and lower edges of the side plates can effectively improve the overall bending resistance of the SHG.

Co-strengthening and deformation behaviors of hybrid additive manufactured U75V/15-5PH bimetal via optimized heat treatment

Bimetals composed of U75V pearlitic steel and 15–5 precipitation hardening (PH) steel were successfully processed by a hybrid additive manufacturing method. However, the U75V/15-5PH bimetal in the as-deposited condition showed inferior mechanical properties owing to the inhomogeneous microstructures. Herein, optimized heat treatment for the co-strengthening of U75V/15-5PH bimetal was designed by investigating the microstructural evolution and mechanical properties thoroughly. Results showed that the mechanical properties of the U75V steel region were recovered after solution treatment, reflected in the formation of lamellar pearlite. For the additive 15-5PH steel region, the formation of martensitic phase and NbC carbides contributed to the strengthening in the solution condition. Furthermore, this region was further hardened by the massive precipitation of Cu-riched precipitates induced by aging treatment. Due to the difference in yield strength of U75V/15-5PH bimetals with various locations, the deformation transfer phenomenon from U75V steel to 15-5PH stainless steel was detected during the uniaxial tensile tests. After heat-treated through the solution and aging treatment, the optimized yield strength, ultimate tensile strength, and elongation of the U75V/15-5PH bimetal achieved 878 MPa, 1201 MPa, and 11.2%, respectively. This study demonstrated experimentally that the mechanical performance of the U75V/15-5PH bimetal with various microstructures could be improved by designing a suitable solution and aging heat treatment.

An analytical solution for the load-settlement relation of hollow composite piles with ultra-large diameters

The load transfer mechanism is significantly more complex due to its heterogeneous radial distribution properties. To solve this problem, smart sensors and actuators are the good candidates for the improvement of structural reliability and robustness. This study investigates the load transfer characteristics of hollow composite piles with ultra-large diameters, and finds out the load transfer path. Based on the shear deformation transfer method and the assumptions of no relative slide between hollow pile, grouting body and cement mixing pile interface, a mechanical analysis model of hollow piles with ultra-large diameters-grouting body-cement mixing pile, is then developed. The basic equations of load-settlement relation of piles are deduced from the mechanical equilibrium conditions. Based on the hyperbolic model, the equivalent elastic modulus is introduced to improve the transfer function method. Afterwards, analytical solutions for the load-settlement relation of hollow composite piles with ultra-large diameters are presented. Finally, the analytical solution based on the two methods is compared with the finite element solution in order to verify their rationality and feasibility. The results indicate that under vertical load, the load transfer path to pile side (radial) is as follows: hollow pile → grouting body → cement mixing pile → foundation soil. Moreover, the transfer path of load to pile tip (vertical) is directly transferred to foundation soil, which is consistent with the traditional large-diameter solid pile. Compared with the shear deformation transfer method, the transfer function method can better simulate the nonlinear soil, which is more consistent with the finite element results.

Automatic design-preserving virtual garment transfer

Design-preserving garment transfer which can transfer a garment from one body to another is a powerful technique in computer graphics. In this paper, we propose a novel method for automatic design-preserving garment transfer. Firstly, the correspondence between the source garment and the source body is automatically calculated by finding the nearest face’s barycenter from the garment to the body. Secondly, the mesh deformation transfer algorithm is utilized to obtain the target garment. After aligning the target garment and body with the ICP algorithm, the virtual fitting result can finally be obtained by fitting the target garment onto the target body. For a new garment worn on the source body, our approach can quickly and effectively transfer the garment to the target body while preserving the designed details. Two experiments were carried out to validate the applicability and effectiveness of our method. The results showed that our method could be applied to different garments for human bodies with different shapes and poses. Additionally, we introduced a new method for evaluating our transferred garments based on similarity and fit. Moreover, our approach can be applied to garments with different particle distances and performs better than the ‘Auto grading’ technique of CLO 3D. Our proposed method is simple, effective, automated and fast. Therefore, it has a significant potential for improving personalized garment development efficiency.

A coupled peridynamics–smoothed particle hydrodynamics model for fracture analysis of fluid–structure interactions

In this paper, a numerical model that couples peridynamics (PD) with smoothed particle hydrodynamics (SPH) is presented for fracture modeling in fluid–structure interaction (FSI) problems. PD was employed to simulate the solid structure fracture because of its ability to deal with discontinuity problems. SPH was applied to simulate the fluid behavior because of its advantages in modeling free-surface flows. A virtual particle layer was established in the fluid–structure interfacial region to ensure the force and deformation transfer between the fluid and solid phases. Validation was performed qualitatively and quantitatively through simulations of classical benchmark tests. The SPH model of the free-surface flow, the PD model of the solid structure, and the coupled PD-SPH model of the FSI were carefully verified. It was demonstrated that the results matched the experimental observations well, with a maximum error of less than 10%. The hydraulic fracture of a gravity dam and the impact of dam-break flow on a baffle were simulated as applications of the coupled PD-SPH model. The predicted crack path in the gravity dam agreed closely with the experimental observations, with a Pearson correlation coefficient of 0.9983. A preliminary extension of the proposed PD-SPH model to three dimensions is also presented, and its performance was evaluated. The results indicate that the coupled model is accurate in modeling the solid fracture process in FSI problems.

Research on Posture Sensing and Error Elimination for Soft Manipulator Using FBG Sensors

Fiber-optic sensors are highly promising within soft robot sensing applications, but sensing methods based on geometry-based reconstruction limit the sensing capability and range. In this study, a fiber-optic sensor with a different deployment strategy for indirect sensing to monitor the outside posture of a soft manipulator is presented. The internal support structure’s curvature was measured using the FBG sensor, and its mapping to the external pose was then modelled using a modified LSTM network. The error was assumed to follow the Gaussian distribution in the LSTM neural network and was rectified by maximum likelihood estimation to address the issue of noise generated during the deformation transfer and curvature sensing of the soft structure. For the soft manipulator, the network model’s sensing performance was demonstrated. The proposed method’s average absolute error for posture sensing was 63.3% lower than the error before optimization, and the root mean square error was 56.9% lower than the error before optimization. The comparison results between the experiment and the simulation demonstrate the viability of the indirect measurement of the soft structure posture using FBG sensors based on the data-driven method, as well as the significant impact of the error optimization method based on the Gaussian distribution assumption.

Analog Models of Lithospheric‐Scale Rifting Monitored in an X‐Ray CT Scanner

AbstractRifting and continental break‐up are fundamental tectonic processes, the understanding of which is of prime importance. However, the vast temporal and spatial scales involved pose major limitations to researchers. Analog tectonic modeling represents a great means to mitigate these limitations, but studying the complex internal deformation of lithospheric‐scale models remains a challenge. We therefore present a novel method for lithospheric‐scale rifting models that are uniquely monitored in an X‐ray CT scanner, which combined with digital image correlation (DIC) techniques, provides unparalleled insights into model deformation. Our first models illustrate how the degree of coupling between competent lithospheric layers, which are separated by a weak lower crustal layer, strongly impacts rift system development. Low coupling isolates the upper crust from the upper lithospheric mantle layer below, preventing an efficient transfer of deformation between both layers. By contrast, fast rifting increases coupling, so that deformation in the mantle is efficiently transferred to the upper crust, inducing either a symmetric or asymmetric (double) rift system. Furthermore, oblique divergence may lead to en echelon graben arrangements and delayed exhumation of the lower crustal layer. The successful application of our novel modeling approach, yielding these first‐order insights, provides a clear incentive to continue running lithospheric‐scale rifting models, and to apply advanced monitoring techniques to extract as much information from models as possible. There is indeed a broad range of opportunities for follow‐up studies within (and beyond) the field of rift tectonics.

Escape Mechanism with Shallow Ramp and Décollements in Southwest Taiwan

The escape structure in southwest Taiwan has long been discussed. The counterclockwise rotation in GPS ground motion is argued to be evidence of tectonic escape. However, tectonic escape events worldwide are always bounded by lithosphere-cutting strike-slip faults at the boundary of the lithospheric-scale rotating block, and these have not observed in Taiwan. In this study, we propose that the escape structure in southwest Taiwan is a thin-skinned deformation due to the open boundary in the continental slope, the ramp, and the shallow décollements. We tested this shallow escape hypothesis using a 3D numerical simulation with elastoplastic rheology. We found that a conjugate pair of forethrust and backthrust developed above the ramp. The strike and location of the forethrust mainly follow the ramp. However, the strike of the forethrust rotates perpendicular to the open boundary when in proximity. From north to south, the strike of the forethrust transfers from NNE to NE, and the deformation transfers from thrust to dextral thrust. This leads to a counterclockwise rotation in ground motion, which matches the GPS observation. This research provides a different explanation of the mechanism for the escape structure in southwest Taiwan.

Study on surface roughness effect on shear behavior of concrete-soil interface

Concrete piles have been widely used in practice due to their large bearing capacity and small settlement. The roughness of concrete-soil interface has a significant influence on load transfer of piles and deformation between piles and soil. To investigate the surface roughness effect on shear behavior of concrete-soil interface, a series of laboratory shear tests, e.g., monotonic and cyclic shear tests, were carried out by using a self-developed large-scale constant normal stiffness (CNS) cyclic shear apparatus. In the laboratory shear tests, the simulation method on the surface roughness of pile body was proposed according to the measured hole diameter along the depth of in-situ bored piles, and concrete samples with different surface roughness values were formed by using carving machine. Based on the results of shear tests on the interface between concrete and standard sand under monotonic and cyclic shear, the relationship between the shear stress and the corresponding displacement was obtained, and the fitting relationship between the shear strength and roughness of concrete-sand interface was established. The shear displacement field of sand was analyzed by using a digital photogrammetric measurement software. The results show that the maximum thickness of the intense shear zone is observed to be 6.25 times the median particle diameters.

Research on plastic deformation transfer and distribution of large-diameter thin-walled metal ring parts in double-roll pendulum hot rotary forging process

Many key structural components in large equipment such as launch vehicles, nuclear submarines, and nuclear power equipment are composed of large thin-walled metal rings with high diameter-thickness. With the development of science and technology, the traditional manufacturing method of melon-shaped tailor welding has gradually been unable to meet the equipment requirements. Due to the advantages of a small required forming force, stable process and good forming quality, the double-roll pendulum hot rotary forging (DRPHRF) technology has great potential in the overall manufacture of large-diameter thin-walled metal ring parts. However, many issues in the DRPHRF process are still unclear, and its application has been severely hindered. Therefore, this paper firstly determines the selection range of key forming parameters for large-diameter thin-walled metal rings in the DRPHRF process. Then, a reliable 3D rigid-plastic thermo-mechanical coupled finite element model for DRPHRF machining of large-diameter thin-walled metal rings was established in the 3D dynamic finite element software 3D-DEFORM. The reliability of the model is verified by experiments. Based on a reliable finite element model, the plastic transfer and distribution in the DRPHRF process of large diameter thin-walled metal rings are studied. On this basis, by setting the process conditions and the characterization factor Q, the influence of key process factors on the plastic distribution of the ring is studied. The research results of this study provide an important basis for the selection of key parameters of the DRPHRF process and the improvement of the forming quality of the DRPHRF process.

FaceTuneGAN: Face autoencoder for convolutional expression transfer using neural generative adversarial networks

In this paper, we present FaceTuneGAN, a new 3D face model representation decomposing and encoding separately facial identity and facial expression. We propose a first adaptation of image-to-image translation networks, that have successfully been used in the 2D domain, to 3D face geometry. Leveraging recently released large face scan databases (FaceScape and CoMA), a neural network has been trained to decouple factors of variations with a better knowledge of the face, enabling facial expressions transfer and neutralization of expressive faces. Specifically, we design an adversarial architecture adapting the base architecture of FUNIT and using SpiralNet++ for our convolutional and sampling operations. Applied on these two datasets, FaceTuneGAN has a better identity decomposition and face neutralization than state-of-the-art techniques. It also outperforms classical deformation transfer approach by predicting blendshapes closer to ground-truth data and with less of undesired artifacts due to too different facial morphologies between source and target.

Deformation behavior of cell walls in an additively manufactured hybrid metallic foam

A hybrid Al-Al3Ni metallic foam was synthesized in-situ via directed energy deposition (DED) of Ni-coated Al 6061 powder, without the need for a foaming agent. Three-dimensional characterization via X-ray computed tomography shows that the foam contains approximately 61.5 % porosity and a high volume fraction of the Al3Ni phase (∼60 vol. %) within the cell walls. This microstructure is notably distinct from the eutectic structure that is typically observed in conventionally processed Al-Ni alloys. To investigate the mechanical properties and deformation mechanisms of the Al-Al3Ni cell walls, in-situ micro-pillar compression was performed, and the results reveal a notable yield strength of 560 MPa and a compressive strain that exceeds 30 %. These properties are attributable to the presence of a high volume fraction of Al3Ni particles, in combination with the characteristics of the Al/Al3Ni interfaces. To provide insight into the deformation mechanisms in the cell walls we used in-situ mechanical testing, transmission electron microscopy and precession electron diffraction characterization, together with molecular dynamics simulations. Our results reveal two distinct mechanisms: uniform dislocation-based deformation of the Al alloy phase and localized deformation within the slip bands in the Al3Ni phase. The results further highlight the importance of the Al/Al3Ni interfaces in mechanical strengthening and the transfer of plastic deformation from the Al phase to the Al3Ni phase. At high mechanical loads, cracks form due to the large stress concentration at the slip bands and slip band intersections in the Al3Ni, giving rise to intragranular fracture of Al3Ni and finally interfacial debonding and cracking.

Microstructures and mechanical properties of a precipitation hardened refractory multi-principal element alloy

Precipitation hardening is used as a powerful strengthening pathway to tailor the mechanical properties of traditional alloys. However, in refractory multi-principal element alloys (RMPEAs), the precipitates with remarkable strengthening effect are relatively less explored. Here, we report novel precipitation hardened body-centered-cubic (BCC) TiVNb RMPEAs through doping surplus boron. 2000 ppm (0.2 wt%) boron doping leads to TiB precipitates, which can enhance the yield strength of TiVNb by ∼350 MPa. Orowan strengthening caused by TiB precipitates serves as the primary strengthening mechanism compared to non-boron alloys. Due to boron doping, the dislocation-mediated deformation transfers from planar-slip to cross-slip and thus avoids stress concentration caused by high-density geometrically necessary dislocation. The excellent strengthening effect and tuned deformation mechanisms led to an optimal RMPEA with a yield tensile strength of ∼972 MPa and an elongation of ∼12%. This work demonstrates that TiB is an efficient precipitate in BCC RMPEAs, which is constructive for the development of precipitation hardened RMPEAs.