Deformation Transfer Research Articles

Efficient 4D shape completion from sparse samples via cubic spline fitting in linear rotation-invariant space

Computer animation is frequently produced via interpolating a few sparse samples created by artists or reverse-engineered from physical prototypes, however, existing interpolation techniques fall short in efficiently generating a smooth 4D shape sequence from sparse samples. In this paper, we extend traditional curve fitting technique to 4D shape completion in shape space with novel technical components. In particular, we seek a smooth 4D shape sequence by minimizing the total shape distortion along the sequence trajectory. After embedding the shapes into a linear rotation-invariant feature space, the complex global minimization of shape distortion in shape space can be converted into simple cubic spline fitting problems in feature domains, which can be solved analytically. With cubic splines, we can not only handle in-between shapes interpolation, but also perform extrapolation towards more exciting results. To further improve the computational efficiency, we devise a hierarchical framework, in which the shape space is decomposed into high-frequency and low-frequency domains, the interpolation is only operated on the low-frequency domain, while the high-frequency details are enabled via deformation transfer techniques. We have conducted extensive experiments and comprehensive evaluations that showcase many attractive advantages of our novel method, including smooth interpolation between shapes, plausible extrapolation outside conventional shape domain, robustness under large deformations, and interactive performance for complicated shapes with high-quality details.

Numerical Analysis of the Effect of Microscale Components Interaction on Measurements of Fiber Optic Strain Sensors Used in Composite Structures

The paper investigates the influence of structural components of a composite material on the strain values measured by using an embedded optical fiber with Bragg gratings. The effect of composite plies and intermediate epoxy layers on the transfer of deformations from the measured object to the optical fiber was studied taking into account various methods of the fiber attachment and surrounding media configurations. A numerical estimation of the effect of the longitudinal and transverse components of the strain tensor on the wavelength of the reflected spectrum is performed.

Residual deformation and stiffness changes of frozen soils subjected to high- and low-amplitude cyclic loading

The present paper reports the results of a laboratory experiment that aimed to investigate the residual deformation and stiffness changes of frozen silty clays under cyclic triaxial loading. Two sets of cyclic stress magnitude — namely, low and high level — were applied to the reconstituted artificial frozen soil specimens with identical properties, and the effect of six levels of confining pressure was examined. The results indicate that two distinct development categories of residual axial strain with number of loading cycles are induced by the low- and high-level cyclic stress. The dynamic Young’s modulus derived from each test experiences a significant increase with the number of loading cycles, which is partly attributed to the cyclic densification. A special observation from the tests under high-level cyclic stress along with a confining pressure of 0.3 MPa also indicates that the dynamic Young’s modulus keeps as a relatively constant value when the change of residual volumetric deformation transfers from compression to dilation. The empirical relationships were proposed to properly reflect the development of the residual axial strain and dynamic Young’s modulus with the number of loading cycles.

Late Cenozoic structural deformation and evolution of the central-southern Longmen Shan fold-and-thrust belt, China: Insights from numerical simulations

Since the Late Cenozoic, the central-southern Longmen Shan (LMS) region is characterized by a two-décollement thrust-fold system with a localized upper evaporite weaker layer just beneath the Sichuan Basin and the lower stronger décollement beneath the LMS. To date, the role of upper décollement and erosion in shaping the structural deformation of the LMS remains unknown. The investigation of this question may shed lights on the assessment of the structural evolution and the further discrimination of mountain building mechanism. In this work, a 2D finite difference method is applied with regards to the variations of viscosity/friction angle, and lengths of upper décollement under different erosion rates. Two types of numerical models are setup, with purely lower-upper frictional (FF) décollements and lower-frictional upper-viscous (FV) décollements. Tectonic evolution with FF models exhibits large similarity with that of FV models. Meanwhile, our results underline the presence of in-sequence fault propagation procedures during most of the stages. The development of the boundary ramp, the Range Frontal Blind fault, is strongly induced by a prerequisite with upper décollement of necessary length. The activation of Beichuan/Pengguan faults or blind ramp piercing to the surface is extremely mechanically sensitive to the viscosity of the salt décollement, erosion rate, and the length of the upper décollement. Out-of-sequence thrusting, shallow and possible basal accretion processes beneath the Sichuan Basin are found when deformation transfers from the thick-skinned LMS to the thin-skinned Sichuan Basin at the very late stage, supporting upper crustal shortening dominates the mountain building mechanism.

Functional Characterization of Deformation Fields

In this article, we present a novel representation for deformation fields of 3D shapes, by considering the induced changes in the underlying metric. In particular, our approach allows one to represent a deformation field in a coordinate-free way as a linear operator acting on real-valued functions defined on the shape. Such a representation provides both a way to relate deformation fields to other classical functional operators and enables analysis and processing of deformation fields using standard linear-algebraic tools. This opens the door to a wide variety of applications such as explicitly adding extrinsic information into the computation of functional maps, intrinsic shape symmetrization, joint deformation design through precise control of metric distortion, and coordinate-free deformation transfer without requiring pointwise correspondences. Our method is applicable to both surface and volumetric shape representations and we guarantee the equivalence between the operator-based and standard deformation field representation under mild genericity conditions in the discrete setting. We demonstrate the utility of our approach by comparing it with existing techniques and show how our representation provides a powerful toolbox for a wide variety of challenging problems.

Cartoonish sketch-based face editing in videos using identity deformation transfer

We address the problem of using hand-drawn sketches to create exaggerated deformations to faces in videos, such as enlarging the shape or modifying the position of eyes or mouth. This task is formulated as a 3D face model reconstruction and deformation problem. We first recover the facial identity and expressions from the video by fitting a face morphable model for each frame. At the same time, user’s editing intention is recognized from input sketches as a set of facial modifications. Then a novel identity deformation algorithm is proposed to transfer these facial deformations from 2D space to the 3D facial identity directly while preserving the facial expressions. After an optional stage for further refining the 3D face model, these changes are propagated to the whole video with the modified identity. Both the user study and experimental results demonstrate that our sketching framework can help users effectively edit facial identities in videos, while high consistency and fidelity are ensured at the same time.

Механизм передачи нагрузки и деформации между волокнами в композиционных материалах

Механизм передачи нагрузки и деформации между волокнами в композиционных материалах

Reduction of stress concentration by polymer flexible joints in seismic protection of masonry infill walls in RC frames

In the paper, the phenomenon of stress concentration occurring in brittle structural materials of infill structures is discussed. Four innovative repair methods based on flexible joints made of polyurethane PM are presented. They provide a reduction of the stress concentration and improvethe structural ductility. The effectiveness of newly proposed timber-polyurethane dissipative struts is proved by laboratory shear tests, which results are discussed in detail. The calculated dissipation energy and stiffness of the proposed system ensures a simultaneous transfer of loads and large deformations occurring during an earthquake to the introduced dissipative struts and improves the system safety. The recommended repair methods can be used efficiently by emergency teams in seismic areas.

Research and Application of Example‐Driven Surface Deformation Method

Despite the large work made in interactive mesh deformation, manipulating a geometrically complex mesh and producing realistic deformation result is still a challenging work. Example-driven deformation methods distinctly simplify the modeling process and produce realistic deformation result by incorporating knowledge learned from shape space. We introduce a rotation invariant feature representation and a reconstruction framework to accurately reconstruct the vertex positions. Our feature representation allows both interpolation as well as extrapolation and can effectively blend multiple shapes. Based on this, we achieve an example-driven approach to mesh deformations. By using a collection of models as examples, our method produces natural deformation results guided by them even with large movement of handles. We will apply our representation and reconstruction method to semantic deformation transfer. The experimental results have demonstrated the effectiveness of the proposed methods.

Face2Face

Face2Face is an approach for real-time facial reenactment of a monocular target video sequence (e.g., Youtube video). The source sequence is also a monocular video stream, captured live with a commodity webcam. Our goal is to animate the facial expressions of the target video by a source actor and re-render the manipulated output video in a photo-realistic fashion. To this end, we first address the under-constrained problem of facial identity recovery from monocular video by non-rigid model-based bundling. At run time, we track facial expressions of both source and target video using a dense photometric consistency measure. Reenactment is then achieved by fast and efficient deformation transfer between source and target. The mouth interior that best matches the re-targeted expression is retrieved from the target sequence and warped to produce an accurate fit. Finally, we convincingly re-render the synthesized target face on top of the corresponding video stream such that it seamlessly blends with the real-world illumination. We demonstrate our method in a live setup, where Youtube videos are reenacted in real time. This live setup has also been shown at SIGGRAPH Emerging Technologies 2016, by Thies et al. where it won the Best in Show Award.

Automatic unpaired shape deformation transfer

Transferring deformation from a source shape to a target shape is a very useful technique in computer graphics. State-of-the-art deformation transfer methods require either point-wise correspondences between source and target shapes, or pairs of deformed source and target shapes with corresponding deformations. However, in most cases, such correspondences are not available and cannot be reliably established using an automatic algorithm. Therefore, substantial user effort is needed to label the correspondences or to obtain and specify such shape sets. In this work, we propose a novel approach to automatic deformation transfer between two unpaired shape sets without correspondences. 3D deformation is represented in a high-dimensional space. To obtain a more compact and effective representation, two convolutional variational autoencoders are learned to encode source and target shapes to their latent spaces. We exploit a Generative Adversarial Network (GAN) to map deformed source shapes to deformed target shapes, both in the latent spaces, which ensures the obtained shapes from the mapping are indistinguishable from the target shapes. This is still an under-constrained problem, so we further utilize a reverse mapping from target shapes to source shapes and incorporate cycle consistency loss, i.e. applying both mappings should reverse to the input shape. This VAE-Cycle GAN (VC-GAN) architecture is used to build a reliable mapping between shape spaces. Finally, a similarity constraint is employed to ensure the mapping is consistent with visual similarity, achieved by learning a similarity neural network that takes the embedding vectors from the source and target latent spaces and predicts the light field distance between the corresponding shapes. Experimental results show that our fully automatic method is able to obtain high-quality deformation transfer results with unpaired data sets, comparable or better than existing methods where strict correspondences are required.

Energy Storage and Dissipation of Human Periodontal Ligament during Mastication Movement.

As a layer of soft fibrous tissue, the periodontal ligament (PDL) protects against mechanical shock when transmitting mastication force from tooth to its surrounding alveolar bone. Currently, no quantitative method is available to estimate the shock resistance ability of the PDL. To solve this problem, in the present study we developed a finite element (FE) model of the tooth-PDL-bone complex and analyzed the energy storage and dissipation during the mastication movements. Displacement and Mises stress of tooth-PDL-bone complex show that the PDL is able to protect the alveolar bone from mechanical shock by shielding the transfer of deformation and stress. During mastication, the energy of the PDL is stored up to ∼161.5 J/mm3 at the period of loading and dissipated about one-tenth of the stored energy when unloading. The energy storage is displacement-dependent but time-independent because of the hyperelasticity of PDL. However, the energy dissipation is time- and displacement-dependent because of the viscoelasticity of PDL. The present study helps to understand the periodontal potential and the origin of dental diseases such as tooth concussion and occlusal trauma from the view of energy conversion.

Effects of the initial adhesive disbonding on patch repaired composites

The adhesive layer plays an important role on the stress and deformation transfer between composite patch and parent plate in a repaired structure. In this paper, based on the nonlinear material properties and continuum damage mechanics, the three-dimensional progressive damage model of the repaired specimen has been built to investigate the effect of initial adhesive disbonding on the ultimate strength and the damage state. The results indicate that the initial adhesive disbonding does not change the final failure mode, but results in the decrease of the final failure load. The decreasing amount of final failure load for the repaired specimen with four-layer patch is larger than that for the repaired specimen with two-layer patch.

Microscopic mechanisms of deformation transfer in high dynamic range branched nanoparticle deformation sensors

Nanoscale stress sensing is of crucial importance to biomechanics and other fields. An ideal stress sensor would have a large dynamic range to function in a variety of materials spanning orders of magnitude of local stresses. Here we show that tetrapod quantum dots (tQDs) exhibit excellent sensing versatility with stress-correlated signatures in a multitude of polymers. We further show that tQDs exhibit pressure coefficients, which increase with decreasing polymer stiffness, and vary >3 orders of magnitude. This high dynamic range allows tQDs to sense in matrices spanning >4 orders of magnitude in Young’s modulus, ranging from compliant biological levels (~100 kPa) to stiffer structural polymers (~5 GPa). We use ligand exchange to tune filler-matrix interfaces, revealing that inverse sensor response scaling is maintained upon significant changes to polymer-tQD interface chemistry. We quantify and explore mechanisms of polymer-tQD strain transfer. An analytical model based on Mori-Tanaka theory presents agreement with observed trends.

Особливості деформації, зміцнення та масоперенесення внаслідок УЗУО поверхні стопу Д16 різними бойками

Особливості деформації, зміцнення та масоперенесення внаслідок УЗУО поверхні стопу Д16 різними бойками

Luders deformation of low-carbon steel

The development of Chernov–Luders bands on elastoplastic transition in low-carbon steel is investigated. The main factors responsible for the creation and development of the bands are identified. The kinetics of the mobile band boundaries (fronts) is of particular interest. The characteristic speeds are determined. The nucleation rate of Chernov–Luders bands exceeds their expansion rate by more than an order of magnitude. The simultaneous development of more than one band, with the appearance of several moving fronts, is considered. In all cases, the fronts of the Chernov–Luders bands move at matched speeds, so that, at any time, the generalized expansion rate of the deformation zone is constant. The influence of the strain rate on the kinetics of the band fronts is analyzed. Both the generalized expansion rate of the deformed zone and the speeds of individual fronts increase with increase in the loading rate. This is a nonlinear dependence (a power law). The fronts of the Chernov–Luders bands are complex in structure. Different sections of the front may move at nonuniform speeds, so that the front is locally distorted and split. Ahead of the front, in the undeformed sample, precursors whose configuration resembles that of the incipient Chernov–Luders bands may be observed. When they meet, the fronts of adjacent bands cancel out. Annihilation of the band fronts is a complex process, characterized by the formation of precursors and secondary diffuse Chernov–Luders bands. These findings indicate that the simplified concept of the Chernov–Luders bands as a deformed region in a loaded sample, as the front of a band, or as the boundary between deformed and undeformed zones must be revised. A microscopic theory of Luders deformation is based on the cascade growth in density of mobile dislocations on account of their breakaway from the points of attachment and their subsequent multiplication, which occurs instantaneously at the upper yield point within the crystallite (grain). At the same time, the formation of a mobile macroscopic strain front calls for the transfer of plastic deformation by adjacent grains, without strengthening. In other words, grain-boundary accommodation is required. The results obtained suggest that the Chernov–Luders band is such an accommodation zone, and so it has a complex structure.

Mass Transfer, Micromixing and Chemical Reactions Carried out in the Rotor-Stator Mixer

Two pairs of fast competitive complex test reactions: neutralization competing with ethyl chloroacetate hydrolysis in the first case, and neutralization competing with 2,2-dimetoxypropane (DMP) hydrolysis in the second case, have been applied do study drop breakup, mass transfer and micromixing in two types of the rotor-stator mixers: Silverson 088/150 MS and T 50 Ultra-Turrax® - IKA. In experiments effects of process conditions on the product distribution of chemical test reactions and the drop size distribution were determined. The product distribution of complex test reactions was evaluated based on results of high- performance liquid and gas chromatography measurements. The drop size distribution was measured with the Malvern MasterSizer just after the process. The multifractal model of intermittent turbulence as well as mass transfer and micromixing models were applied to interpret and predict the course of the processes of drop breakage, mass transfer, mixing and complex chemical reactions. The population balance modeling was applied to integrate effects of different mixing and chemical reaction effects. Based on experimental data and model predictions the energetic efficiencies of drop breakage and mass transfer in the rotor-stator mixers were identified and discussed. The models of mass transfer in liquid-liquid systems are discussed in detail. The first models based on physics of mass transfer phenomena were proposed by Levich and Batchelor in sixties and seventies years of the 20th century, and were further developed by other researchers. Here we apply two models, the first one was proposed by Polyanin and the second one by Favelukis and Lavrenteva. Both models are based on the original concept of Levich, the second one includes effects on mass transfer of drop deformation to the shape of prolate ellipsoid. Limitations of both models are presented and possibilities of improvement of their performance are discussed.

The mechanism for the high dependence of the Hall-Petch slope for twinning/slip on texture in Mg alloys

A Hall-Petch slope (k) that is highly changeable with texture, as extensively reported in Mg alloys, is ultimately related to the variation of deformation modes. In this paper, the influence of different (0002) distributions on k for twinning and slip was systematically studied using an AZ31 rolled plate ([0002]//ND) and extruded rod ([0002]⊥ED together with a random distribution around the ED). The ND and ED refer to the normal direction of the plate and extrusion direction of the rod, respectively. A high dependency of k on the (0002) distribution is found, namely, a much lower k for {101¯2} twinning in the plate (219 MPa μm1/2) than that in the rod (435 MPa μm1/2), but a much higher k for slip in the plate (437 MPa μm1/2) than that in the rod (235 MPa μm1/2). Compound use of the difference in Schmid factor (ΔSF) and geometric compatibility factor (m′) quantitatively explains this orientation effect on k. ΔSF relates to the extra stress needed for the activation of slip/twinning in a neighboring grain, and m′ reflects the efficiency of the stress concentration at the onset of slip/twinning in an adjacent grain. The lower m′ for twinning in the rod versus the plate primarily accounts for the higher k for twinning in the rod. A much larger inclination of basal poles away from the ideal texture exists in the plate than in the rod, which induces a higher activity of basal slip during tension. The resultant high fraction of slip transfer from basal slip in one grain to prismatic slip in the neighboring grain largely amplifies ΔSF and reduces m′, both of which yield a higher k for slip in the plate than in the rod. The relationship between the crystallographic orientation and m′ was also calculated for different types of deformation transfer, and the main factor that determines m′ was revealed.

Current deformation in Central Afar and triple junction kinematics deduced from GPS and InSAR measurements

Kinematics of divergent boundaries and Rift-Rift-Rift junctions are classically studied using long-term geodetic observations. Since significant magma-related displacements are expected, short-term deformation provides important constraints on the crustal mechanisms involved both in active rifting and in transfer of extensional deformation between spreading axes. Using InSAR and GPS data, we analyse the surface deformation in the whole Central Afar region in detail, focusing on both the extensional deformation across the Quaternary magmato-tectonic rift segments, and on the zones of deformation transfer between active segments and spreading axes. The largest deformation occurs across the two recently activated Asal-Ghoubbet (AG) and Manda Hararo-Dabbahu (MH-D) magmato-tectonic segments with very high strain rates, whereas the other Quaternary active segments do not concentrate any large strain, suggesting that these rifts are either sealed during interdyking periods or not mature enough to remain a plate boundary. Outside of these segments, the GPS horizontal velocity field shows a regular gradient following a clockwise rotation of the displacements from the Southeast to the East of Afar, with respect to Nubia. Very few shallow creeping structures can be identified as well in the InSAR data. However, using these data together with the strain rate tensor and the rotations rates deduced from GPS baselines, the present-day strain field over Central Afar is consistent with the main tectonic structures, and therefore with the long-term deformation. We investigate the current kinematics of the triple junction included in our GPS data set by building simple block models. The deformation in Central Afar can be described by adding a central microblock evolving separately from the three surrounding plates. In this model, the northern block boundary corresponds to a deep EW-trending trans-tensional dislocation, locked from the surface to 10–13 km and joining at depth the active spreading axes of the Red Sea and the Aden Ridge, from AG to MH-D rift segments. Over the long-term, this plate configuration could explain the presence of the en-´ echelon magmatic basins and subrifts. However, the transient behaviour of the spreading axes implies that the deformation in Central Afar evolves depending on the availability of magma supply within the well-established segments.

Concurrent editing of automotive styling and structure with wireframe-pair

A constant demand in engineering design is to couple aesthetics and functionality of design. In this paper, a method is proposed to rapidly update the structural analysis models given the modifications made in the styling/packaging designs, forming a concurrent mechanism for developing the automotive styling and body structure. The seemingly disparate domains are represented by and thus coupled through a pair of wireframes. A joint mapping based on the hard points in packaging and a part mapping encoding local influences between wireframes are established. The deformation transfer from one of the wireframes to the other is solved as an optimization with constraints obtained from the two mappings. Finally, the finite element mesh model is adapted in accordance with the deformed structural wireframe, using a mesh morphing method based on the free-form deformation technique. Numerical results validate the proposed method and demonstrate its effectiveness.