Complicated Deformation Research Articles

Numerical study of thermal nonequilibrium effects on Richtmyer-Meshkov flow driven by a heavy forward-triangular bubble.

This paper investigates the thermal nonequilibrium effects on Richtmyer-Meshkov (RM) flow driven by a heavy forward-triangular bubble. Numerical laminar simulations are performed by utilizing the compressible dimensionless Navier-Fourier equationsobtained from the Boltzmann-Curtiss transport equationof nonmonatomic gases that consider translational energy-rotational energy transfer. Three distinct gases, including monatomic argon, diatomic nitrogen, and polyatomic methane, envelop a forward-triangular bubble that is filled with sulfur hexafluoride. Simulations are performed with a shock Mach number of 1.2. The simulations demonstrate that the thermal nonequilibrium and flow characteristics of nonmonatomic gases cause significant changes in the flow fields, which lead to complicated wave patterns, bubble deformation, and vortex dynamics. Using contours and spatially integrated fields of vorticity generation, degree of nonequilibrium, enstrophy, dissipation rate, and kinetic energy, a thorough analysis of nonmonatomic gases is conducted. The nonmonatomic gases produce larger rolled-up vortex chains, longer outward jet forms, and enormous mixing zones with strong, large-scale expansion in contrast to monatomic gases. Furthermore, a quantitative analysis of the time variations of interface features reveals that nonmonatomic gases have enhanced interface features. Lastly, a quantitative investigation is conducted into the consequences of thermal nonequilibrium characteristics. Two patterns are seen in spatially integrated fields: a rising trend in response to an increase in the bulk viscosity ratio and a falling trend in response to an increase in the inverse power-law index.

Kirigami-Inspired Three-Dimensional Metamaterials with Programmable Isotropic and Orthotropic Thermal Expansion.

Mechanical metamaterials with specifically designed cells can provide unusual thermal expansion properties for diverse applications. Limited by very few available cell topologies and complicated non-linear structural deformation, most existing thermal expansion metamaterials can only achieve orthogonally isotropic negative/zero/positive thermal expansion (NTE/ZTE/PTE) within a mild range, especially the 3D ones. Here, based on one-degree-of-freedom kirigami polyhedrons proposed with a kinematic design strategy, a family of 3D isotropic and orthotropic metamaterials capable of programmable NTE, PTE, and even ZTE over ultra-wide range is developed. Incorporating bi-material strips as creases for isotropic polyhedrons, NTE and PTE metamaterials with coefficients of thermal expansion (CTEs) ranging from -2354.3 to 3006.7ppm/°C are designed and programmed by the theoretical model. Meanwhile, isotropic ZTE metamaterials are constructed by either homogeneous tessellation of ZTE cells or hybrid tessellation of NTE and PTE cells. Furthermore, by allowing distinct geometric parameters in the three orthogonal directions of the kirigami polyhedrons while preserving the kinematic motion, orthotropic metamaterials, in which each of the three directions can be assigned with an independently programmed NTE, ZTE, or PTE, are also achieved. This study paves a novel pathway for the development of thermal expansion metamaterials with potential applications for space optical systems, MEMS, and so on.

Automated detection of deformation mechanisms in re-entrant honeycomb auxetics using machine learning

The intricate geometrical configuration of an auxetic structure enables high energy dissipation capacity at the expense of a highly nonlinear mechanical response. Under external stimuli, complicated deformation mechanisms emerge which dictate the extent of energy dissipation. Recently, the new ‘plastic hinge tracing’ method (Dhari et al., 2021) was introduced to detect such deformation mechanisms for elastoplastic porous materials. This approach is however subjective and cumbersome since it requires monitoring several plastic regions in consecutive deformed configurations. The present study innovatively extends this method by implementing machine learning (ML) techniques for objective detection of deformation modes in auxetics. To this end, a logistic regression ML model was developed to classify the deformation modes of a re-entrant honeycomb structure. The proposed procedure could successfully detect four out of the six deformation modes (‘X’, distorted ‘X’, ‘V’, and ‘V + Z + V’) using the training datasets generated by the finite element analysis and image labels created by K-means clustering algorithm. The success of the proposed automated approach lays the foundation for identifying the deformation mechanisms of other auxetics and porous materials with plastic deformations.

High-Precision Vertical Deformation of the Chinese Mainland Constrained by Leveling and GNSS data

Summary A high-precision and high-resolution vertical velocity for the Chinese mainland is obtained by integrating precise leveling and GNSS data, using a Helmert joint adjustment method. The results show that the surface vertical rates range between -3.0 and 3.9 mm/yr with continuous deformation in most areas, except the obvious subsidence at the rates of -15.0 to -94.2 mm/yr induced by groundwater exploitation in the North China Plain. Particularly, the central and southern Tibet, Tien Shan, Alashan, Ordos, eastern Cathaysia, and Northeast China uplift at the rates of 0.5 – 3.9 mm/yr; the southeastern Tibetan Plateau, Sichuan basin, and Yangtze block are dominated by surface subsidence at the rates of -3.3 to -0.5 mm/yr. Furthermore, the vertical rates vary little between the eastern and western regions of the Chinese mainland despite their pronounced differences in horizontal deformations. The effects of gravity isostasy and non-tectonic factors, including the environmental mass loads, Glacier Isostatic Adjustment (GIA), poroelastic expansion/compression, and mining operations have partially contributed to the vertical deformation of the Chinese mainland. Overall, this velocity reflects the complicated deformation features induced by the multiple geodynamic processes of the Chinese mainland. These geodynamic processes include isostasy, orogenic processes, and geothermal anomalies associated with slab subduction/plate collision.

Trimodal Grain Structured Aluminum Matrix Composites Regulated by Transitional Hetero-Domains

Aluminum matrix composites (AMCs) with hetero-grains exhibit high strength with good ductility. A trimodal grain structure composed of ultrafine grains (UFGs), fine grains (FGs) and coarse grains (CGs) prevents the pre-mature cracking of hetero-zone boundaries in conventional bimodal grain structures; thus, it is favored by AMCs. However, the design of the size and distribution of hetero-domains in trimodal AMCs is tough, with complicated multi-scale deformation mechanisms. This study tunes the distribution of FG domains elaborately via altering the volume fraction of FG from 10 vol.% to 60 vol.% and investigates the distribution effect of FG domains on strength–ductility synergy. The optimized 2024 Al matrix composites with 30 vol.% FG exhibited a tensile strength of over 700 MPa and an elongation of 7.5%, respectively, realizing a good combination of high strength and ductility. This work enlightens the heterostructure design with a balance between heterogeneous deformation induced (HDI) strain hardening and high-content soft phase induced strain homogenization.

Transpression in the Eastern Jiangnan Orogen and its implications for ductile deformation process and regional Tectonics of the South China block

The transpressive deformation in the eastern Jiangnan Orogen during the Early Paleozoic is the structural response to the oblique convergence of the Yangtze-Cathaysia blocks, and this relationship is critical for understanding the tectonics of South China. The Jiangwan–Huangshan shear zone (JHSZ) and Baiji–Sanyang shear zone (BSSZ) exhibit NEE–SSW-trending oblique dextral and sinistral shearing, respectively, and their evolution resulted in local E–W dextral strike-slip shearing. Most kinematic vorticity values range from 0.4 to 0.81, which implies that the JHSZ and BSSZ deformed under the contribution of both pure-shear and simple-shear components, suggesting complicated deformation histories for those orogenic shear zones. The quartz and feldspar deformation mechanisms, opening angles and lattice preferred orientation (LPO) patterns of the quartz c-axis fabrics suggest shear deformation temperatures between 400 and 550 °C in the eastern Jiangnan Orogen. Locally deformation occurred under high-temperature (>600 °C) conditions. Combined with previous data and regional geology, these findings indicate that the shearing deformation in the eastern Jiangnan Orogen accommodated the oblique convergence between the Yangtze and Cathaysia blocks during the Early Paleozoic, which was possibly caused by the final assembly of Gondwana.

Crustal Structure and Anisotropy Measured by CHINArray and Implications for Complicated Deformation Mechanisms Beneath the Eastern Tibetan Margin

AbstractWe investigated velocity and anisotropic structure of the crust beneath the eastern margin of the Tibetan Plateau to better understand its deformation and evolution mechanism. We performed H‐κ and Pms anisotropy analyses to obtain crustal thickness, Vp/Vs ratio, fast polarization direction, and splitting time from 711 stations, and further conducted quality control using slowness, harmonic and statistical analyses. The Songpan‐Ganzi Block has a large splitting time and a fast polarization direction roughly parallel to the GPS motion and SKS fast direction. It also shows an overall high but complex distribution of Vp/Vs ratio, and large variations in crustal thickness, indicating that crustal deformation is likely caused by crustal shortening and lower crustal flow. The northern Sichuan‐Yunnan Rhombic Block (SYRB) is featured by a thick crust and high Vp/Vs ratio, suggesting that the crust is likely inflated by partial melting lower crustal rocks. The subblock also exhibits a strong azimuthal anisotropy with a splitting time greater than 0.6 s. The fast polarization direction aligns with the nearly N‐S extended direction and rotates clockwise in front of the Emeishan Large Igneous Province (ELIP). The observed anisotropy agrees with aligned amphibole minerals under a simple shear condition, supporting a southward lower crust flow being diverted by the ELIP. Anisotropy measurements on the southern SYRB are less robust and widely scattered, suggesting a deformation mechanism different from the northern SYRB. In addition, the southeastern margin of the Sichuan Basin shows a systematic pattern of crustal anisotropy consistent with a pure shear deformation mechanism.

Recursive Deformable Pyramid Network for Unsupervised Medical Image Registration.

Complicated deformation problems are frequently encountered in medical image registration tasks. Although various advanced registration models have been proposed, accurate and efficient deformable registration remains challenging, especially for handling the large volumetric deformations. To this end, we propose a novel recursive deformable pyramid (RDP) network for unsupervised non-rigid registration. Our network is a pure convolutional pyramid, which fully utilizes the advantages of the pyramid structure itself, but does not rely on any high-weight attentions or transformers. In particular, our network leverages a step-by-step recursion strategy with the integration of high-level semantics to predict the deformation field from coarse to fine, while ensuring the rationality of the deformation field. Meanwhile, due to the recursive pyramid strategy, our network can effectively attain deformable registration without separate affine pre-alignment. We compare the RDP network with several existing registration methods on three public brain magnetic resonance imaging (MRI) datasets, including LPBA, Mindboggle and IXI. Experimental results demonstrate our network consistently outcompetes state of the art with respect to the metrics of Dice score, average symmetric surface distance, Hausdorff distance, and Jacobian. Even for the data without the affine pre-alignment, our network maintains satisfactory performance on compensating for the large deformation. The code is publicly available at https://github.com/ZAX130/RDP.

Hot Deformation Behavior of Inconel 718 Alloy Using Regression-based Dynamic Material Model and Applications in Ring Rolling Manufacturing

Inconel 718 nickel-based alloy is extensively used in the aerospace industry (e.g., gas turbine engine components) because of its excellent corrosion resistance and high mechanical properties at elevated temperatures. However, there is a certain limit to manufacturing the alloy through plastic deformation due to its high deformation resistance and complicated deformation behaviors. In this study, the hot deformation behavior of Inconel 718 alloy was investigated to establish how processing conditions of flow stress-strain, at strain rates from 0.001 to 10 s<sup>-1</sup>, and temperatures from 850 to 1200<sup>o</sup>C, affected dynamic recrystallization. The regression-based material model was utilized to calculate the strain-rate sensitivity, and subsequently depict the efficiency of the power dissipation and instability criterion of hot deformation. The processing map and instability criterion predicted by the developed 3<sup>rd</sup>-order polynomial regression model corresponded with the experimental results and in particular, showed a better prediction for instability regime compared to the existing discrete derivative approach. Predicting the strain-rate sensitivity values on a continuous scale with regression analysis covered the additional instability region of the high strain rate near 10 s<sup>-1</sup>. The dynamic recrystallization deformation was also characterized by microstructural analysis along with the processing map. Consequently, ring-rolled aviation parts were manufactured with the optimum processing parameters, which conform to the AMS 5663 standard (Aerospace material specifications for Inconel 718).

AR-UNet: A Deformable Image Registration Network with Cyclic Training.

Deformable image registration is a process to determine the non-linear spatial correspondence among deformed image pairs. Generative registration network is a novel structure involving a generative registration network and a discriminative network that encourages the former to generate better results. We propose an Attention Residual UNet (AR-UNet) to estimate the complicated deformation field. The model is trained using perceptual cyclic constraints. As an unsupervised method, we require labelling for training and use virtual data augmentation to improve the robustness of the proposed model. We also introduce comprehensive metrics for image registration comparison. Experimental results show quantitative evidence that the method can predict reliable deformation field at a reasonable speed and outperform conventional learning based and non-learning based deformable image registration methods.

Nonlinear mechanical behavior and stress amplification effect correction of thin plate welded structure considering initial deformation

With the continuous development of light weight of ships, thin plate welded structures are widely used in superstructure of large hull structures and high-speed boats. However, the thin-plate welded structure has a special nonlinear mechanical behavior because of its small stiffness, more complicated welding deformation. The nonlinear mechanical behavior of thin plate welded structure is mainly caused by large slenderness ratio and complex initial buckling deformation, which can be characterized and quantified by defining global deformation angle αG and local deformation angle αL. Because of the welding angle deformation and welding dislocation, there is obvious stress amplification effect at the welding corner, but the traditional stress amplification correction formula is only suitable for thick plate welding structure. Aiming at the nonlinear mechanical behavior and secondary bending moment effect of thin plate welded structure, an analytical model of thin plate welded structure with initial deformation is established by combining theoretical derivation and numerical method. The results show that the additional bending moment effect caused by local welding deformation angle cannot be ignored. Finally, combined with a series of fatigue tests, the additional bending moment caused by bending deformation and angular deformation of typical welded joints is analyzed, and the notch stress field and fatigue strength correction of thin plate welded structures with initial defects are realized.

Evolution of the Deformation‐ and Flow‐Induced Crystallization and Characterization of the Microstructure of a Single Spherulite, Lamella, and Chain of Isotactic Polypropylene

AbstractIsotactic polypropylene (iPP) is a frequently used polymer in industrial processing and scientific research, used as a model material. This review highlights some current and forefront issues in polymer science and engineering. This review alludes to classical deformation schemes to interpret the complicated deformation in isotactic polypropylene as a semicrystalline polymer. Also, due to the complex hierarchical structures of crystallized polymers, the progress on the multiscale and multistage microstructural evolution covering each deformation stage from the initiation of plasticity until failure is mainly concerned, particularly in terms of crystalline morphology changes. Specifically, the characterization of the microstructure evolution of a single spherulite, lamella, and chain of isotactic polypropylene will be emphasized and mentioned. Here, the authors are most interested in the results obtained from stretching (strain‐induced) orientation and crystallization studies accompanied by the in situ scattering and spectroscopy techniques offering a detection window from nano to micrometer scale, which should be able to reflect the microstructural changes at different length scales of interest. During polymer processing, the melts are frequently subjected to shear or/and elongation flow fields, producing flow‐induced molecular chain orientation in the melt. The oriented molecular chains crystallize differently than those encountered under quiescent conditions. Thus, orientation‐induced crystallization has long been an object of intense interest. A vast body of research is reported about the effects of preorientation on the crystallization of various polymers. Among them, iPP is most frequently studied since its diversified structure and morphology are very sensitive to changes in processing conditions and molecular parameters.

A Stable, Efficient, and High-Precision Non-Coplanar Calibration Method: Applied for Multi-Camera-Based Stereo Vision Measurements.

Traditional non-coplanar calibration methods, represented by Tsai's method, are difficult to apply in multi-camera-based stereo vision measurements because of insufficient calibration accuracy, inconvenient operation, etc. Based on projective theory and matrix transformation theory, a novel mathematical model is established to characterize the transformation from targets' 3D affine coordinates to cameras' image coordinates. Then, novel non-coplanar calibration methods for both monocular and binocular camera systems are proposed in this paper. To further improve the stability and accuracy of calibration methods, a novel circular feature points extraction method based on region Otsu algorithm and radial section scanning method is proposed to precisely extract the circular feature points. Experiments verify that our novel calibration methods are easy to operate, and have better accuracy than several classical methods, including Tsai's and Zhang's methods. Intrinsic and extrinsic parameters of multi-camera-systems can be calibrated simultaneously by our methods. Our novel circular feature points extraction algorithm is stable, and with high precision can effectively improve calibration accuracy for coplanar and non-coplanar methods. Real stereo measurement experiments demonstrate that the proposed calibration method and feature extraction method have high accuracy and stability, and can further serve for complicated shape and deformation measurements, for instance, stereo-DIC measurements, etc.

Anisotropic constitutive model of frozen silty clay capturing ice cementation degradation under high mean stresses

Research results show that comparing to unfrozen soil, frozen soil has more complicated deformation behavior owing to the presence of ice. On the basis of triaxial tests results of frozen silty clay (FSC) at ˗6 °C, due to the ice cementation, the critical state line (CSL) of FSC does not cross the origin of the deviatoric plane. The critical deviatoric stress of FSC increases nonlinearly as the mean stress growing; however, further increases of the mean stress give rise to the decreases in the critical deviatoric stress. Because under high mean stresses, the ice-melting and-crushing (IMAC) cause ice cementation degradation. To predict the deformation of FSC, a new anisotropic constitutive model that considers the degradation of ice cementation is proposed. In the proposed model, first, the elastic parameters of FSC are obtained by conducting triaxial shear loading-unloading (TSLU) tests and isotropic compression loading-unloading (ICLU) tests. Second, yield and plastic potential functions are proposed, the two involve the modified mean stress and indicate the degradation of ice cementation. Third, a double hardening law pertaining to isotropic hardening and rotational hardening is developed by considering initial anisotropy and stress-induced particle rotation under shear loading. Finally, the comparison results confirm that the developed constitutive model is valid and suitable for describing the stress–strain relations of FSC.

Metallurgical enhancement and mechanical performance of GTAW of AA5083 plates using medium and high-entropy fillers

The contemporary investigation focusses on the development of a welding technique to join AA5083 alloy plates using equimolar medium entropy alloy (4E-MEA - Fe0.25Al0.25Ni0.25Cu0.25) and high entropy alloy (5E-HEA - Fe0.2Al0.2Ni0.2Cu0.2Ti0.2) filler wires. A man-made combined cable wire method, was chosen to prepare the filler wires and the gas tungsten arc welding was used to conjoin the AA5083 plates. This study evaluated the metallurgical characteristics and mechanical performance of welded joints using 4E-MEA and 5E-HEA filler weldments and compared them with the standard ER5356 filler weldment. XRD analysis showed that both 4E-MEA and 5E-HEA weldments had evolved BCC and FCC phases, whereas microstructural analysis revealed a fine grain distribution without intermetallic phases. SEM analysis of the weldments revealed a heterogeneous microstructure (equiaxed and columnar grains) owing to the influence of the constituent elements. Solid solution formation, structural refinement, and high configurational entropy effects promoted grain refinement in the weldments as evidenced by EBSD analyses. The microhardness of 4E-MEA and 5E-HEA weldments increased by 18.3% and19.89%, respectively, compared with the standard filler weldment, while the tensile strength of 4E-MEA and 5E-HEA weldments increased by 24.3% and 27.9%, respectively and also obtained work-hardening rates were higher. It was observed that the heterogeneous microstructure in the weldment led to complicated plastic deformation and improved the mechanical responses. The presence of Fe and Ni increased ductility and inhibited the formation of intermetallic. The fractography results showed that the 4E-MEA and 5E-HEA filler weldments exhibited a combination of ductile and brittle fractures. Overall, the researchers demonstrated that the developed equimolar 4E-MEA and 5E-HEA filler wires could produce weldments with improved mechanical properties and can be utilized in automobile and shipbuilding applications.

Numerical investigation of shock Mach number effects on Richtmyer–Meshkov instability in a heavy square bubble

This study conducts a two-dimensional numerical investigation of incident shock Mach number effects on the Richtmyer–Meshkov (RM) instability after a shock wave impulsively drives a heavy square bubble. The square bubble is composed of SF6 gas, which is surrounded by nitrogen gas. Five different shock Mach numbers are considered: Ms=1.12, 1.22, 1.4, 1.7, and 2.1. Two-dimensional compressible Euler equations for two-component gas flows are simulated with a high-order modal discontinuous Galerkin solver. For validation, the numerical results are compared with the existing experimental results and are found to be in good agreement. The present results reveal that the incident shock Mach number is critical in the growth of RM instability in a heavy square bubble. The shock Mach number affects flow morphology significantly, resulting in complicated wave patterns, shock focusing, jet creation, bubble deformation, and vorticity generation. The convergent shape of the bubble causes shock focusing, which creates a local high-pressure zone and, as a result, an outward jet generation. It is found that the bubble deforms differently with increasing shock Mach number, and the different shock Mach numbers alter the distance between the shock focusing position and the downstream bubble interface. The effects of shock Mach numbers are investigated in depth through physical phenomena such as vorticity production, kinetic energy, and enstrophy. Finally, the shock Mach number impacts on the time-variations of the shock trajectories and interface structure are thoroughly investigated.

Interference of ocean and land mass changes in seasonal crustal deformation of coastal stations: A case study in northern Australia

In tropical regions, alternation of rainy and dry seasons causes significant land hydrological mass changes. It brings “landward” seasonal crustal movements of coastal global navigation satellite system (GNSS) stations in rainy seasons. Here, we report that the coastal region of the Gulf of Carpentaria (GOC), northern Australia, behaves oppositely, i.e., they move “oceanward” during austral summer months despite large precipitations on land. Here we study seasonal gravity changes there with satellite gravimetry and analyze seasonal movements of GNSS stations in that region. During the austral summer, hydrological mass increases in nearby land areas. In addition to that, sea water mass within the gulf also increases due to east-southeastward seasonal winds. It has larger amplitudes than on land, and its peak comes a few months earlier, resulting in seasonal displacements of coastal GNSS stations driven predominantly by ocean mass changes. In this study, we emphasize the importance of seasonal horizontal crustal movements, i.e., the oceanward displacements of coastal stations there in austral summer clearly indicate the dominance of the excessive ocean mass over those on land. Such seasonal mass changes within GOC have been largely overlooked because of insufficient spatial resolution of satellite gravimetry. This study presents a model case for interpreting complicated seasonal surface deformation caused by significant seasonal load changes on land and ocean, often found in coastal areas of half-closed oceans in the world.

Lode-dependent anisotropic-asymmetric yield function for isotropic and anisotropic hardening of pressure-insensitive materials. Part I: Quadratic function under non-associated flow rule

It is challenging to precisely model the complicated plastic deformation of metals, including anisotropy in strength and plastic deformation, strength differential effect, anisotropic hardening, etc. A new approach is proposed to extend anisotropic yield functions into asymmetric ones by introducing a Lode dependent function. The approach is applied to the Hill48 function with a Lode-dependent function in a form of the normalized third stress invariant. The proposed Lode-dependent anisotropic-asymmetric (LAA) is applied to characterize the anisotropic hardening behaviors under both tension and compression of QP1180, DP980, AA2008 T4 and α-Ti to verify its performance. The convexity of yield surface evolution with plastic deformation is investigated by a geometry-inspired numerical convex analysis method. The application shows that the proposed LAA function precisely characterizes the anisotropy in tension and compression and its evolution with plastic deformation. It is therefore suggested to model the anisotropic-asymmetric plastic behavior with its applications to metal forming.

Effect of complicated deformation behaviors during cold stamping on springback prediction of DP980 steel

Effect of complicated deformation behaviors during cold stamping on springback prediction of DP980 steel

A New Method to Estimate Slab Dip Direction Using Receiver Functions and Its Application in Revealing Slab Geometry and a Diffuse Plate Boundary Beneath Sumatra

AbstractWhile dip direction is a fundamental parameter of slab geometry, it is rarely estimated quantitatively. Here, we develop a new method, Dip Direction Searching (DDS), of receiver functions (RFs) that reduces the uncertainty of slab dip direction estimation from tens to several degrees. DDS can also resolve the thickness and depth of a dipping structure. We then apply DDS to the RFs in the Sumatran subduction zone. Travel time differences of the converted phases from the upper and lower (oceanic Moho) boundaries of the dipping low‐velocity layer (LVL) along the plate interface show a thickness of 10–14 km. The results also show increased dip direction of the slab Moho from 47 ± 5.3° in southern Sumatra to 70 ± 10.7° in northern Sumatra, indicating a complicated slab geometry and internal deformation along strike. Similar dip directions are obtained for the upper and lower LVL boundaries beneath Nias and Enggano forearc islands in the north and south, whereas we find a larger discrepancy of ∼14–23° beneath Siberut and Pagai in between. The thicker LVL with a non‐negligible difference in the dip directions of its upper and lower bounds in the center of Sumatra is interpreted as a partially serpentinized mantle layer above the oceanic crust, forming a distinct channel atop the subducting slab. Our results provide basic observational constraints on the structure and geometry of the oceanic slab and associated subduction processes. Both synthetics and data analyses also indicate DDS can be applied in other subduction zones and for other dipping interfaces.