Large Structural Deformations Research Articles

Three-dimensional large deformation reconstruction for slender wing-like structures from strain measurements

Shape-sensing technology has significant applications in real-time monitoring and controlling flexible aerospace structures. Aiming at large deformation of flexible wing-like structures, an algorithm that incorporates geometric nonlinearity is developed for three-dimensional shape reconstruction based on strain measurements. The full-field three-dimensional deformation is described in terms of the deflection of the spatial reference line and the motions of the cross-sectional plane. A certain number of strain measurements distributed on the structural surface are used to estimate the generalized strains and the warping deformation, which can further determine the position of an arbitrary material point in the structure by a series of recursion relations. Instead of the experimental research, the desired strains and the deformation as references are simulated by high-fidelity finite element models. A simple tube model and a more realistic composite wing model are investigated separately to demonstrate the present method in reconstructing deformed shapes under various applied loads. Besides, the modal method was also used to calculate the deformation as a comparison. The result has demonstrated the high accuracy and capability of the present method in three-dimensional shape reconstruction, especially for large deformation problems. The warping effect is demonstrated to have a significant impact on predicting the twist angle. More attention should be paid to accurately describing the warping deformation of complicated wing models, especially when the bending deformation is large.

Cross stage partial connections based weighted Bi-directional feature pyramid and enhanced spatial transformation network for robust object detection

Structural information is an essential component for efficient object detection. In many visual detection tasks, the objects with large structural deformation usually make up a large proportion. The shape, contour, and internal structure of the objects tend toward dramatic change, which easily causes troubles for efficient object detection. Therefore, how to detect these objects robustly and accurately is one of the significant challenges. To address this issue, we introduce a Cross Stage Partial connections-based weighted Bi-directional Feature Pyramid Network (CSP-BiFPN), which allows easy and efficient multi-scale feature fusion by cross-stage partial connections. Second, to enhance the model's spatial transformation capacity, the multi-scale feature maps extracted from the YOLO backbone network are processed by an enhanced spatial transformation network (ESTN) for spatial deformations. Based on these architectural modifications and optimizations, we further develop a novel real-time robust object detection model called Bi-STN-YOLO. We evaluate the performance of the proposed method on four image datasets. The experimental results demonstrate that the proposed approach achieves significant improvements compared with the typical YOLO families and competitive performance compared to the state-of-the-arts in detection tasks.

Prediction of Thermoacoustic Instability and Fluid–Structure Interactions for Gas Turbine Combustor

Abstract This work simulates a laboratory-scale three-dimensional methane/air burner, which features a bluff body stabilized, lean partially premixed flame experiencing strong limit cycle oscillations. A thin steel liner is installed around the combustion chamber, which heavily interacts with the flow field and produces large amplitude structural deformation via fluid–structure interaction (FSI). An unsteady Reynolds averaged Navier–Stokes (URANS) approach uses the shear stress transport (SST) turbulence model and a flamelet generated manifold (FGM) combustion model to predict the thermoacoustic oscillations in the turbulent reacting flow. The solver also has a built-in finite element structure model, which solves the structural governing equations simultaneously with the computational fluid dynamics (CFD)-computed, finite volume flow equations. This way, a fully coupled, two-way FSI simulation can be performed to predict the thermoacoustic instabilities and the associated solid deformations in the burner. Overall, the predicted strongest pressure oscillation and wall displacement modes (frequency and amplitude) are all in good agreement with the experimental data across different operating conditions. The established workflow may support realistic gas turbine combustor design and prognosis.

Layered Oxide Cathodes Promoted by Crystal Regulation Strategies for Potassium-Ion Batteries.

Layered oxide cathodes have demonstrated great potential for potassium-ion batteries (PIBs) on account of high reversible capacity, appropriate diffusion paths, and low cost. However, their electrochemical performance in PIBs is generally worse than that in lithium-ion batteries due to large structural changes and deformations during charging and discharging. To improve their potassium storage performance, a series of strategies have been developed in recent studies. In this review, we summarize the latest advancements in layered oxide cathodes for PIBs through different crystal regulation strategies, including transition metal layer doping, potassium content optimization, oxygen partial substitution, functional morphology construction and air stability improvement. Meanwhile, the relationship between the electrochemical properties and structural evolution of these modified cathodes is also investigated. In addition, the challenges and prospects of these layered oxide cathodes in PIBs are analyzed in detail, providing constructive insights for future applications of PIBs.

On nonlinear free vibration of externally compressible fluid-loaded sandwich cylindrical shells: Curvature nonlinearity in bending and impermeability condition

A nonlinear fluid–structure interaction (FSI) model is presented for nonlinear vibration analysis of sandwich cylindrical shells subjected to an external compressible flow by considering the curvature nonlinearity in impermeability condition and bending. The sandwich shells are made of two face sheets and a central core of advanced materials including functionally graded (FG), metal foam, and anisogrid lattice composite. Based on the Kirchhoff–love hypotheses with the geometric nonlinearities in the normal strain and curvature of mid-surface, one decoupled nonlinear integral–differential equation is obtained for axisymmetric bending vibration of sandwich cylindrical shells. For the first time, the nonlinear impermeability condition is developed in order to take into account the large deformation of thin structures in FSI modeling. In both subsonic and supersonic regimes of steady irrotational compressible flow, a closed-form expression for nonlinear pressure distribution is presented according to the conservation of mass and generalized Bernoulli equation of extended potential theory. Using the Galerkin’s method in conjunction with the multiple-scale perturbation technique, the decoupled equation is solved to obtain nonlinear frequency and time–history response. Finally, parametric studies are carried out to investigate the effects of geometric ratios, boundary conditions, fluid specifications, and material variation on the responses of sandwich shells with different layups such as [Al; FG core; ZrO2], [Al; foam core; ZrO2], [Al; lattice core; Al]. Significant differences in pressure variation due to curvature nonlinearity are observed for short shells with larger vibration amplitude and larger number of half-waves in the axial direction. Therefore, the linear vibration analysis is inadequate for analyzing short sandwich cylindrical shells surrounded by an external fluid flow especially in the case of movable ends.

Large Deformation Shape Sensing Using a Nonlinear Strain to Displacement Method

This paper presents a three-dimensional strain-to-displacement transformation method based on a nonlinear modal formulation, suitable for cases of large structural deformations. The method is first demonstrated numerically on a complex beam-like structure test case. A sensitivity study presents the effects of different solution parameters, such as the number of modes and sensors used and the measurement noise. The method is then applied to an experimental test case of the Pazy wing that undergoes very large deformations of 50% span. The wing is equipped with fiber optic strain sensors and a motion-tracking camera system that provides the reference displacement data. The modal data are extracted experimentally, and the scheme is validated using data from a structural loading test. The method is used in a wind tunnel test to map the wing’s deformations from measured strain data. Results are compared to those of a linear modal strain-to-displacement transformation method and to displacements computed by direct integration of the measured strains. The process is shown to yield superior results in cases of large deformations.

Complicated Fault Characterization and Its Influence on Shale Gas Preservation in the Southern Margin of the Sichuan Basin, China

Abstract The southern margin of the Sichuan Basin is characterized by strong structural deformation, complex fault structure styles and scales, and multistaged geological evolution stages, which together have created various shale gas preservation conditions. Taking Jianwu (JW)–Luochang (LC)–Shuanglong (SL) synclines as an example, the fault development characteristics and structural styles of the Longmaxi Formation were studied based on fine seismic interpretation and microscopic tests (rock acoustic emission experiments and fracture-filling inclusion tests), and the effects of the fault stage, fault class and scale, and fracture development degree on shale gas preservation conditions were analysed. Basement-involved faults, detachment faults, and intraformational microfaults are mainly developed from southeast to northwest. These fault structural types have affected the JW Syncline in the southeastern part, where faults are developed from the bottom of the Cambrian to the Wufeng–Longmaxi Formation and from the Wufeng–Longmaxi Formation to the Permian (Triassic). The SL-LC region in the northwestern part is dominated by the faults from the Wufeng–Longmaxi Formation to the Permian (Triassic). This region is dominated by NE-trending main control faults, supplemented by NW-trending, approximately EW-trending, SN-trending, and other small-scale regulating faults. Fault development can be divided into three stages, corresponding to the early, middle, and late Himalayan tectonic movements. In the early stage, a few small-scale approximately EW-trending faults had little impact on shale gas preservation. In the intermediate stage, the large number of large-scale NE-trending main control faults significantly impacted shale gas preservation. The JW Syncline mainly developed three types of faults with a high-filling degree, weak upwards penetration, and small-scale relevant fractures, which together created favourable conditions for shale gas preservation. The western and northern parts are dominated by I and II faults with large structural deformation, a low-filling degree, a large-scale, and strong penetration of related fractures, which have created unfavourable conditions for shale gas preservation. During the late stage, approximately SN- and NW-trending strike-slip reverse faults developed, and strong shear and fracture zones formed near the faults, producing unfavourable conditions for shale gas preservation. This research has clarified the characterization method of fault characteristics and stages and has established the influence of complex faults on shale gas preservation, which has an important reference value for the exploration and evaluation of shale gas reserves in complex tectonic regions.

Large negative thermal expansion induced by cation dimerization in ilmenite-type vanadate ceramic

A significant negative thermal expansion (NTE) in an ilmenite-type MgVO3 ceramic is reported in this paper. MgVO3 undergoes V–V dimerization at 500–550 K accompanied by a structural phase transition from the triclinic (low-temperature) to rhombohedral (high-temperature) phase. This transition induces a large anisotropic crystal structure deformation and results in a large NTE in the ceramic sample, which is caused by the microstructural effect. The NTE was observed over a temperature range of 450–630 K, and the total volume shrinkage reached approximately −0.7%. This study demonstrates that controlling the chemical bonding is a promising method for the creation of NTE materials.

Doubly doped graphene as gas sensing materials for oxygen-containing gas molecules: A first-principles investigation

Recently, defective graphene (DG) are being highly studied nanosheet as a gas sensor. To investigate the adsorption behavior of oxygen containing gas molecules such as CO, NO, NO2 and SO2 on the pristine graphene (PG) and dual B, N, O and F doped DG (2B-DG, 2N-DG, 2O-DG and 2F-DG) nanosheets, density functional theory (DFT) has been carried out. In this study, the DG shows efficient sensitivity towards the gas molecules at the defected site compared with the PG. The adsorption energy, charge transfer and electronic properties indicate that the chemisorption of NO and NO2 on 2B-DG; NO2, SO2 and CO on 2N-DG; NO2, SO2 and CO on 2O-DG; and CO, NO, NO2 and SO2 on 2F-DG take place at the defected sites. Other gas molecules are adsorbed on the nanosheets in a weak physical adsorption process. Although 2F-DG interacts with the gas molecules in high adsorption energies, it is not suitable for gas adsorption due to high recovery time, high formation energy and large structural deformation. Therefore, 2B-DG, 2N-DG and 2O-DG nanosheets could be more promising candidates than PG and 2F-DG for oxygen containing toxic gas molecules.

A flexible actuator curve model for aeroelastic simulations of wind turbines in atmospheric boundary layers

The current trend of wind turbine upscaling has led to the use of long and slender blades prone to large structural deformations. In the present study, the impact of the aeroelastic effects is assessed for the NREL-5MW wind turbine in a turbulent wind. To this end, an actuator curve method coupled to a one-dimensional finite-element structural solver is implemented in a fourth-order finite difference code that can perform large eddy simulation (LES) of realistic winds. The approach is computationally affordable compared to blade-resolved simulations and hence long time series can be computed. This, combined to the ability of the LES to capture the relevant scales of the unsteadiness wind, leads to a better estimation of the fluctuating loads and power of the turbine. The results are here shown for one and two wind turbines operating in a neutrally stable atmospheric boundary layer. It appears that the blade mostly deforms according to its first bending mode. The rotation of the blade in the sheared atmospheric flow is responsible for large amplitude deformations, but the turbulence also plays a role in causing deformations at higher frequencies with a smaller amplitude. The azimuthal distributions of loads and of power are significantly affected when the aeroelasticity is considered.

Investigation of ultimate bearing capacity of shield tunnel based on concrete damage model

Shield tunnel is usually treated as an underground permanent facility with a design service life of 100 years, its bearing capacity and service performance has attracted extensive attention. Previous studies on the mechanical behavior of shield tunnel are mostly carried out within the framework of elastic or elastoplastic theories. However, when these theories are used to explore the ultimate bearing capacity of shield tunnels, large structural deformation is bound to occur, which leads to crack or damage development and finally structural failure. Therefore, to analyze the damage and failure of shield tunnels, the damage and deterioration characteristics of concrete materials should be considered. Also, the damage mechanics theory is more appropriate to deal with this problem. In this paper, a damage–based analysis method for investigating the ultimate bearing capacity of shield tunnels is proposed. A bi–scalar elastoplastic damage constitutive model based on energy–based stress decomposition is introduced to describe the damage and deterioration behavior of concrete materials. Then, an elaborate numerical model of shield tunnel is developed based on the 3D discontinuous contact model. Moreover, the validity of the proposed method is verified by comparing the simulations with the full–scale experimental results. Then, the ultimate bearing capacity and damage characteristics of shield tunnels in practical underground service conditions are discussed. It is found that the numerical results are generally in good agreement with the experimental data, so that the proposed model can effectively reflect the characteristics of structural deformation, internal force transfer, damage evolution process, failure mode and stress redistribution in the loading process. Also, it is found that the failure process of the tunnel structure can be divided into linear elastic phase, yield–damage phase and failure phase. The range of each phase depends on the loading conditions and surrounding soil constraints. In addition, the integrated stiffness and bearing capacity of the tunnel–soil coupled structure increase with the increase of soil elastic modulus and lateral coefficient of earth pressure. The increase of coupled structural stiffness will also shorten the yield–damage phase and decrease the structural toughness (or ductility). The failure modes of the shield tunnel structure are manifested by the bolt yielding, concrete cracking, and finally, the forming joint plastic hinges on the tunnel crown and waist joints.

Insights from detailed numerical investigation of 15 MW offshore semi-submersible wind turbine using aero-hydro-servo-elastic code

Offshore wind turbines are getting larger in terms of dimensions to maximize power generation. Large wind turbine offshore structures can be installed in deep water locations, where they have the advantage to generate higher power due to high wind speeds. To achieve this, wind turbine manufacturers are introducing larger and scaled-up designs to meet the global energy demands. However, these models suffer from large structural loads and deformations when subjected to varying environmental loadings. Therefore, it is necessary to fully comprehend the multibody coupled dynamics of such large offshore structures before proceeding towards their installation in open oceans. This paper carries out an extensive investigation on the ultimate load analysis and fully coupled dynamic response of the 15 MW reference turbine mounted over a UMaine VolturnUS-S semi-submersible floating platform. We used OpenFAST to carry out the stability and full-system linearization studies followed by a detailed time-domain analysis for the power production, parked and fault conditions. We began with a brief background theory on linearization and eigenanalysis for identifying the natural frequencies followed by discussion of the Campbell diagram showing the full-system natural frequencies. It was observed that the multi-blade coordinate code does not correctly pick the natural frequencies. Additional free decay tests have been carried out to verify the full-system natural frequencies. The variation of mean, minimum and maximum values of various characteristic loads and platform motions with respect to different environmental conditions are also presented. We also discussed the change in dynamic response due to the yaw misalignment, wind–wave misalignment, and second-order wave forces. The parked and fault conditions were found to be the critical design load cases (DLCs) for the design of IEA 15 MW wind turbine mounted on Volturn US-S semi-submersible. Furthermore, this paper gives an insight of the important DLCs to be considered while computing the design loads for similar large wind turbine structures.

Bayesian calibration for large‐scale fluid structure interaction problems under embedded/immersed boundary framework

AbstractBayesian calibration is widely used for inverse analysis and uncertainty analysis for complex systems in the presence of both computer models and observation data. In the present work, we focus on large‐scale fluid‐structure interaction systems characterized by large structural deformations. Numerical methods to solve these problems, including embedded/immersed boundary methods, are typically not differentiable and lack smoothness. We propose a framework that is built on unscented Kalman filter/inversion to efficiently calibrate and provide uncertainty estimations of such complicated models with noisy observation data. The approach is derivative‐free and non‐intrusive, and is of particular value for the forward model that is computationally expensive and provided as a black box which is impractical to differentiate. The framework is demonstrated and validated by successfully calibrating the model parameters of a piston problem and identifying the damage field of an aircraft wing under transonic buffeting.

Coupled thermomechanical modelling of shape memory alloy structures undergoing large deformation

Shape Memory Alloys (SMAs) exhibit strain recovery capabilities even after undergoing large deformation, out of underlying stress and temperature dependent diffusionless martensitic transformation. Modelling its behaviour accurately requires coupled thermomechanical analysis, considering absorption and emission of latent heat during phase transformation, thermoelastic effects, thermomechanical loading and boundary conditions. Moreover, the variation of material properties, e.g., modulus of elasticity and thermal expansion coefficient, during phase transformation, significantly affects the response of the system. In addition, appropriate stress and strain measures are required to model the large deformation of SMA-based components under practical thermomechanical loads. In this study, a nonlinear finite element formulation based on Total Lagrangian (TL) approach has been developed to address geometric as well as material non-linearity arising out of the SMA behaviour. Furthermore, considering all the above-mentioned effects, both the stress and thermal equilibrium equations are solved simultaneously in an incremental–iterative finite element (FE) framework, simulating the coupled SMA response. The SMA constitutive model, using Green–Lagrange strain and Second Piola–Kirchhoff stress measures, proposed by Qidwai and Lagoudas (2000), has been implemented. Using the developed FE model, the thermomechanical responses of SMA wire actuator, beam and biomedical staple are simulated to demonstrate the need for the coupled analysis while considering large deformation of the SMA structures.

Local Approach of Ductile Rupture Under Cyclic Loading Conditions

Abstract Experiments have shown that ductile failure occurs sooner under cyclic loading conditions than under monotone ones. This reduction of ductility probably arises from an effect called “ratcheting of the porosity” that consists of a continued increase of the mean porosity during each cycle with the number of cycles. Improved micromechanical simulations confirmed this interpretation. The same work also contained a proof that Gurson's classical model for porous ductile materials does not predict any ratcheting of the porosity. In a recent work (Morin et al., 2017, “A Gurson-Type Layer Model for Ductile Porous Solids With Isotropic and Kinematic Hardening,” Int. J. Solids Struct., 118–119, pp. 167–178), the authors proposed a Gurson-type “layer model” better fit than Gurson's original one for the description of the ductile behavior under cyclic loading conditions, using the theory of sequential limit analysis. A very good agreement was obtained between the model predictions and the results of the micromechanical simulations for a rigid-hardenable material. However, the ratcheting of the porosity is a consequence of both hardening and elasticity, and sequential limit analysis (Yang, 1993, “Large Deformation of Structures by Sequential Limit Analysis,” Int. J. Solids Struct., 30(7), pp. 1001–1013; Leu, 2007, “Analytical and Numerical Investigation of Strain-Hardening Viscoplastic Thick-Walled Cylinders Under Internal Pressure by Using Sequential Limit Analysis,” Comput. Methods Appl. Mech. Eng., 196(25–28), pp. 2713–2722; Leblond et al., 2018, “Classical and Sequential Limit Analysis Revisited,” C. R. Méc., 346(4), pp. 336–349.) is strictly applicable in the absence of elasticity. In this work, a proposal is made to take into account elasticity in the layer model through the definition of a new objective stress rate leading to an accurate expression of the porosity rate accounting for both elasticity and plasticity. This proposal is assessed through comparison of its predictions with the results of some new micromechanical simulations performed for matrices exhibiting both elasticity and all types of hardening. Finally, a comparison of the predictions regarding finite element modeling of pipes loaded cyclically is proposed.

Mitigation of impact force through optimisation of three-phase locally resonant structures

This study explored a new impact protection method based on three-phase locally resonant structures (LRSs), and this method did not rely on large structural deformation and material destruction. The performances of three LRSs with a steel cylindrical oscillator (LSCYO), aluminium cylindrical oscillator (LACYO), and steel cubic oscillator (LSCUO) were studied. A design with an optimised topology with the goal of maximising the impact attenuation was introduced to further improve the performance. The nonlinearities of the material, geometry, and contact were simultaneously considered in the optimisation of the design. The analysis results indicated that these optimal LRSs were anisotropic and could efficiently attenuate the impact load and absorb the impact energy. The attenuation effects of these optimal LRSs were better than those of the original and LRS models. In addition, the mechanisms of the energy absorption and conversion in the impact attenuation process were analysed. The vibration modes and propagation behaviours of the waves of these optimal LRSs were also studied. The attenuation frequencies of the waves and natural frequencies of these optimal LRSs were in good agreement, and the attenuation frequencies of the waves were all within the spectral range of the impact loads. In addition, multiple optimal LRSs were applied simultaneously to study their impact response, and the attenuation effect of the impact force was demonstrated. In short, this study investigated the attenuation mechanism of LRSs from the perspective of energy conversion, explored the new application scenarios of LRSs, and provided a novel solution for the impact problem, which is of significance in the field of functional structure design and impact protection.

Nonlinear Aeroelastic Analysis of Highly Flexible Wings Using the Modal Rotation Method

This paper presents a nonlinear framework for the static and flutter analysis of highly flexible wings accounting for large deformations, using a linear modal database. A nonlinear static analysis is conducted followed by a flutter analysis of the deformed shape. The wing deformations are computed with the recently presented modal rotation method that computes large structural deformations using spatial derivatives of the mode shapes. The modal rotation method is coupled with an aerodynamic model, based on the rigid configuration, to compute static aeroelastic deformations. The method was extended to compute mode-shapes and frequencies of the deformed structure and to alter the unsteady aerodynamic matrices to obtain a flutter solution of the deformed wing. Results were validated based on two experimental studies from the literature.

Coupling with the Embedded Boundary Method in a Runge-Kutta Discontinuous-Galerkin Direct Ghost-Fluid Method (RKDG-DGFM) Framework for Fluid-Structure Interaction Simulations of Underwater Explosions

Solution of near-field underwater explosion (UNDEX) problems frequently require the modeling of two-way coupled fluid-structure interaction (FSI). This paper describes the addition of an embedded boundary method to an UNDEX modeling framework for multiphase, compressible and inviscid fluid using the combined algorithms of Runge-Kutta, discontinuous-Galerkin, level-set and direct ghost-fluid methods. A computational fluid dynamics (CFD) solver based on these algorithms has been developed as described in previous work. A fluid-structure coupling approach was required to perform FSI simulation interfacing with an external structural mechanics solver. Large structural deformation and possible rupture and cracking characterize the FSI phenomenon in an UNDEX, so the embedded boundary method (EBM) is more appealing for this application in comparison to dynamic mesh methods such as the arbitrary Lagrangian-Eulerian (ALE) method to enable the fluid-structure coupling algorithm in the fluid. Its limitation requiring a closed interface that is fully submerged in the fluid domain is relaxed by an adjustment described in this paper so that its applicability is extended. Two methods of implementing the fluid-structure wall boundary condition are also compared. The first solves a local 1D fluid-structure Riemann problem at each intersecting point between the wetted elements and fluid mesh. In this method, iterations are required when the Tait equation of state is utilized. A second method that does not require the Riemann solution and iterations is also implemented and the results are compared.

Multi-camera stereo-DIC methods and application in full-field deformation analysis of reinforced Coral-SWSSC beams

Multi-camera stereo-digital image correlation (stereo-DIC) methods have gained popularity as non-contact methods for measuring high-spatial-resolution deformation of large engineering structures. Common multi-camera stereo-DIC methods can be classified into two types: target-based and calibration-based methods. Considering the wide application prospects of multi-camera stereo-DIC methods, it is important to study and compare the performances of these two types of multi-camera stereo-DIC methods. A four-point bending test of reinforced seawater sea-sand coral concrete (Coral-SWSSC) beams was conducted in this study to investigate the performance of multi-camera stereo-DIC in deformation measurement of slender components, and the measurement accuracy, robustness, and applicability of the two types of multi-camera stereo-DIC methods were compared and discussed. Furthermore, deformation analysis of reinforced Coral-SWSSC beams based on high-resolution multi-camera stereo-DIC methods was performed. The analysis showed that beams strengthened with basalt fiber-reinforced polymer wrapped steel tube and ultra high performance concrete (UHPC) can fully exploit the properties of Coral-SWSSC; the two strengthening materials demonstrated a higher compatibility, which compensates for the low strength defect of the Coral-SWSSC, making it a viable strengthening method. This study may promote the application of multi-camera stereo-DIC methods to measuring high-resolution deformation of large engineering structures.

Deformations related to atom mixing in Si/SiO2/Si nanopillars under high-fluence broad-beam irradiation

Structures consisting of a single Si nanodot buried within an insulating nanometric ${\mathrm{SiO}}_{2}$ layer stacked between two Si layers show promising properties for room temperature operational single-electron transistors. Moreover, such structures are highly compatible with modern complementary metal-oxide semiconductor technologies. Metastable ${\mathrm{SiO}}_{\mathrm{x}}$ phase separates into a Si nanodot and insulating, homogeneous ${\mathrm{SiO}}_{2}$ during annealing, providing a solid path towards the desired structure. However, achieving the necessary amount of excessive Si, dissolved in the ${\mathrm{SiO}}_{2}$ for correct concentrations of ${\mathrm{SiO}}_{\mathrm{x}}$, remains a technological challenge. In this work, we investigate ion-induced atom mixing in pre-built $\mathrm{Si}/{\mathrm{SiO}}_{2}/\mathrm{Si}$ nanopillars, which is considered to be a technologically promising way to produce the necessary concentrations of spatially confined ${\mathrm{SiO}}_{\mathrm{x}}$ in a controlled manner. During the high-fluence ion irradiation, we notice a significant shortening of the nanopillar and preferential loss of O atoms. Both sputtering and nanoscale ion hammering are found to be the cause of the deformation. The ion-hammering effect on nanoscale is explained by multiple small displacements, strongly enhanced after the nanopillar was rendered completely amorphous. The methods presented here can be used to determine the ion-fluence threshold for sufficient atom mixing in spatially confined regions before the large structural deformations are formed.