Sinusoidal Deformation Research Articles

Ultrasonic fatigue of superelastic Nitinol and in situ synchrotron observation of strain and damage

Superelastic Nitinol was tested at ultrasonic frequency in the high and very high cycle fatigue regime. Thin sheet specimens were initially preloaded to mimic crimping and deployment of Nitinol implants, which lead to a sample in a multi-phase state with martensitic phase in the middle and adjacent zones with austenitic phase. In situ synchrotron X-ray diffraction (XRD) was used to monitor cyclic strains over an entire ultrasonic cycle, and to compare the results with low frequency loading. Both austenitic and martensitic regimes showed similar sinusoidal elastic deformation at cycling frequencies 0.1 Hz and 18.3 kHz, and strains were comparable over the entire gauge section of the specimen. XRD data showed progressive growth of austenitic bands in formerly martensitic areas with increasing numbers of ultrasonic cycles. This increased specimen stiffness and cyclic stresses promoting crack initiation, which nearly exclusively occurred at cracked surface inclusions. The strain versus fatigue lifetime diagram shows a pronounced change in slope below 106 cycles. The overlapping properties measured at low and ultrasonic frequency demonstrate that ultrasonic fatigue testing is in principle appropriate for rapid characterization of the cyclic properties of Nitinol.

Thermal dynamics of nanoparticle aggregation in MHD dissipative nanofluid flow within a wavy channel: Entropy generation minimization

This paper examines how nanoparticle aggregation and a consistent magnetic field influence the peristaltic movement of a dissipative nanofluid, which is caused by the sinusoidal deformation of the boundary. The viscosity of TiO2/H2O nanofluids is accurately determined by the Krieger-Dougherty model with nanoparticle aggregation, while thermal conductivity (TC) is estimated through the Bruggeman model. The set of governing equations are modeled in a fixed frame by utilizing the conservation laws of energy, mass and momentum. Galilean transformation is utilized to transform the system of equations into a wave frame, which is then converted into a dimensionless form. The assumption of a small Reynolds number and long wavelength serve to further simplify the set of equations, which are subsequently addressed through the implementation of the differential quadrature method (DQM), a highly effective numerical technique. Quantities of interest, namely velocity, pressure gradient, temperature, trapping phenomena, heat transfer, and volumetric entropy generation are analyzed across a range of physical parameters, including the solid volume fraction (Φ=0.01−0.04), Eckert number (Ec=0.0−0.1), Hartman number (Mh=0.2−2.2), Grashof number (Gr=1.0−3.0) and temperature ratio parameter (θd=0.5−2.5). A comparative analysis is conducted between the scenario involving aggregation and the one without aggregation. It is observed that nanoparticle aggregation significantly alters these quantities.

Experimental Observation of a New Attenuation Mechanism in hcp‐Metals That May Operate in the Earth's Inner Core

AbstractSeismic observations show the Earth's inner core has significant and unexplained variation in seismic attenuation with position, depth and direction. Interpreting these observations is difficult without knowledge of the visco‐ or anelastic dissipation processes active in iron under inner core conditions. Here, a previously unconsidered attenuation mechanism is observed in zinc, a low pressure analog of hcp‐iron, during small strain sinusoidal deformation experiments. The experiments were performed in a deformation‐DIA combined with X‐radiography, at seismic frequencies (∼0.003–0.1 Hz), high pressure and temperatures up to ∼80% of melting temperature. Significant dissipation (0.077 ≤ Q−1(ω) ≤ 0.488) is observed along with frequency dependent softening of zinc's Young's modulus and an extremely small activation energy for creep (⩽7 kJ mol−1). In addition, during sinusoidal deformation the original microstructure is replaced by one with a reduced dislocation density and small, uniform, grain size. This combination of behavior collectively reflects a mode of deformation called “internal stress superplasticity”; this deformation mechanism is unique to anisotropic materials and activated by cyclic loading generating large internal stresses. Here we observe a new form of internal stress superplasticity, which we name as “elastic strain mismatch superplasticity.” In it the large stresses are caused by the compressional anisotropy. If this mechanism is also active in hcp‐iron and the Earth's inner‐core it will be a contributor to inner‐core observed seismic attenuation and constrain the maximum inner‐core grain‐size to ≲10 km.

Tunable deformation design of porous Al2O3 based on the Direct FE2 method

Abstract The tunable deformation design of porous ceramics has raised many interests in many engineering and manufacturing fields, where its corresponding design methodologies still suffer from the lower efficiency and higher computational cost. To handle this problem, a novel optimization and design methodology based on the Direct FE2 method has been proposed in this study, and several numerical examples of the porous Al2O3 tunable deformation design has been performed by this novel methodology. Compared with the traditional methodologies, the proposed method is more convenient to conduct the tunable deformation design and improves the optimization efficiency. Based on this method, the distribution and assembly of the microscale RVE could be tailored along the space dimension to handle the sinusoidal deformation and variable Poisson’s ratio ceramic design at the macroscale. By comparing the simulation results with the Direct Numerical Simulation (DNS) model, the effectiveness and accuracy of this methodology is well validated. Meanwhile, the simulation results based on the proposed methodology found that the predictability of porous Al2O3 deformation could be enhanced by changing the micro structure parameters such as the elliptical hole angle and aspect ratio. This methodology holds great potential for applications in the design and optimization of porous ceramics with tailored deformation characteristics.

Uncertainty of digital image correlation under video compression and DSP optimization.

The storage and transmission of videos at high spatial resolution remain a great challenge in image-based optical techniques. The uncertainty of digital image correlation (DIC) was assessed following speckle video compression under High Efficiency Video Coding (HEVC/H.265). First, the evaluation criterion for the DIC accuracy affected by compression was provided. The stability of H.265 video compression in DIC was studied considering different compressed frames under different target quantization parameters (QPs) and compression ratios (CRs). The deformation uncertainty of the DIC itself as affected by H.265 video compression was further investigated through uniform translation and non-uniform sinusoidal deformation performance. Moreover, the optimized digital speckle pattern (DSP) was re-evaluated considering video compression-induced uncertainty. DSPs with parameters of different diameters and randomness were compressed using various QPs and CRs. In addition, DSP evaluation was performed under both translation and non-homogeneous deformation conditions. The feasibility of the re-optimized DSP under H.265 video compression was validated using a defective bending beam, and DSP videos with a speckle size of 8 pixels reached a high CR within an acceptable margin of error.

Analysis of sinusoidal post-buckling deformation of horizontal coiled tubing with initial residual bending.

In the process of horizontal well construction, the working environment in the well is very complicated. It is difficult to determine the actual deformation and force of the coiled tubing in the wellbore from the load change at the wellhead along. In addition, the coiled tubing wrapped around the reel and entering the wellbore through the injection head may cause an initial residual bending. In this paper, the mathematical model of the coiled tubing under axial load during buckling deformation is established, and the analytical solution with the time term is derived by reasonable simplification of the model. The effect of residual bending on the post-sinusoidal buckling of the coiled tubing in the horizontal well was investigated using the separation variable method. The effect of residual bending variations on the well wall contact forces is analyzed. The research shows that the initial parameter Г is the main factor influencing the post-sinusoidal buckling of the coiled tubing with residual bending. The larger the parameter value Г, the greater the effect of the residual bending on the post-sinusoidal buckling deformation of the coiled tubing, and the earlier the critical point of the mixed sinusoidal-helical buckling of the coiled tubing appears. The compression velocity of the coiled tubing has a significant effect on the well wall contact force. The faster the compression, the greater the contact force. By introducing the time term and the separation variable, this paper provides a new method and theoretical basis for further study of the process of entering sinusoidal-helical buckling of the coiled tubing with initial residual bending.

FoilTrack: a package to increase strain-resolution by improved X-radiographic image processing

ABSTRACT In high pressure multi-anvil experiments X-radiography is used to ascertain strain in deforming samples because the tooling prevents optical or other direct observations of the sample. The processing of these X-radiographic images to determine bulk sample strain is one of the limiting factors to making measurements closer to the strains and strain-rates that occur during mantle convection or the passage of seismic waves. Typically, sample deformation in these experiments is tracked by the displacement of high-contrast marker foils in X-radiographs. X-radiographs are treated individually or pairwise in a multi-step process that tracks the displacement of marker foils during experiments. Here I develop a new algorithm, FoilTrack, that treats all the X-radiographic observations in a single-step process, resulting in improved accuracy and consistency of length changes determined from X-radiographic images, as well as providing more realistic parameter uncertainty. The improvements are demonstrated using data from small-strain sinusoidal deformation experiments.

Advances in large amplitude oscillatory shear Rheology of food materials

Molecular interactions determine the microstructure of food, as well as its response to deformation and flow. In order to design efficient processing equipment, to produce high-quality, stable end products, to predict textural and sensory properties, and to ensure consumer acceptance, the characterization of food rheology is essential. Deformations are rapid and large during the processing of foods and during consumption. In food studies, large amplitude oscillatory shear (LAOS) has become increasingly popular due to its ability to mimic real-life processes. When food is subjected to dynamic oscillatory shear tests, a sinusoidal deformation is applied, the mechanical stress (or strain) is probed, and the response is recorded. This chapter summarize main methods to extract meaningful rheological parameters from complex LAOS response of selected food materials. A time-resolved nonlinear rheology method, sequence of physical processes (SPP), gave detailed interpretations of transient microstructures, whereas the Fourier Transform coupled with Chebyshev decomposition (FTC) method provide static measurements at specific strains. LAOS behavior and its relationship to food microstructures and texture still needed to be studied in depth. By constructing more accurate mechanical models of complex food systems, the fundamental knowledge can be applied to evaluate the nonlinear rheology of food for consumer acceptance and efficient processing.

Study on Sinusoidal Post-Buckling Deformation of Coiled Tubing in Horizontal Wells Based on the Separation Constant Method

In this paper, a set of partial differential equations considering the dynamic effects of the coiled tubing (CT) is established based on the bending theory of slender beams considering the axial loads. The analytical solution of sinusoidal deformation with the time term is obtained. The critical load of coiled tubing during sinusoidal buckling and the change of half-wave number during sinusoidal post-buckling are studied through the introduction of the necessary conditions, solution and the separation constant. The contact force of coiled tubing with sinusoidal post-buckling on the horizontal well wall is analyzed. The results show that the critical load for sinusoidal buckling of fixed-size CT is related to the section angular acceleration coefficient. The half-wave number produced by the sinusoidal post-buckling bending of the CT gradually decreases during compression. The contact force of the deformed CT to the borehole wall is related to the compression speed of the CT. By introducing the dynamic term and the separation constant, this research model can provide a theoretical basis for studying the transformation of the CT from sinusoidal buckling to helical buckling.

Structural damping renders the hawkmoth exoskeleton mechanically insensitive to non-sinusoidal deformations.

Muscles act through elastic and dissipative elements to mediate movement, which can introduce dissipation and filtering which are important for energetics and control. The high power requirements of flapping flight can be reduced by an insect's exoskeleton, which acts as a spring with frequency-independent material properties under purely sinusoidal deformation. However, this purely sinusoidal dynamic regime does not encompass the asymmetric wing strokes of many insects or non-periodic deformations induced by external perturbations. As such, it remains unknown whether a frequency-independent model applies broadly and what implications it has for control. We used a vibration testing system to measure the mechanical properties of isolated Manduca sexta thoraces under symmetric, asymmetric and band-limited white noise deformations. The asymmetric and white noise conditions represent two types of generalized, multi-frequency deformations that may be encountered during steady-state and perturbed flight. Power savings and dissipation were indistinguishable between symmetric and asymmetric conditions, demonstrating that no additional energy is required to deform the thorax non-sinusoidally. Under white noise conditions, stiffness and damping were invariant with frequency, suggesting that the thorax has no frequency-dependent filtering properties. A simple flat frequency response function fits our measured frequency response. This work demonstrates the potential of materials with frequency-independent damping to simplify motor control by eliminating any velocity-dependent filtering that viscoelastic elements usually impose between muscle and wing.

Minimizing the total strain error in point-wise least squares using rotated gaussian weight strain filter (RGW-SF) in digital image correlation

The point-wise least squares (PLS) has been widely accepted as a simple and trustworthy strain computation method that smooths and differentiates the noisy displacement field calculated directly by digital image correlation (DIC). Smooth window size and kernel function need to be determined before using PLS. The selection of the proper smooth window size has long been a tricky issue for practitioners, which has an obvious impact on the final total strain error of complex deformation. A small smooth window may reduce the system/bias error but increase the random error, and vice versa. In this paper, a rotated Gaussian weight strain filter (RGW-SF) is proposed for heterogeneous strain field measurement. The motivation of RGW-SF is to adapt the weights of each point in tradition PLS smooth window to obtain lower total strain error, which is derived and then minimized to select an optimum strain filter with three weight parameters (i.e., σx,σy, and θ). The effectiveness of the proposed RGW-SF is verified using simulated sinusoidal deformation images and the Star 6 image set from DIC-challenge 2.0. Experiments show that the RGW-SF can find a trade-off between the system error and the random error. The displacement and strain field accuracy, especially for the metrological efficiency indicator, by RGW-SF is much better than that of the PLS and the self-adaptive strain algorithm (SSA). The proposed RGW-SF is strongly suggested for unknown severely heterogeneous strain measurement.

Three-Dimensional Curve Reconstruction Based on Material Frame and Twisted Multicore Fiber

We propose a curve reconstruction model based on material frame and twisted multicore fiber (MCF), which can reconstruct the position and orientation of MCF simultaneously. The twisted MCF is approximated as a ribbon, whose centerline and surface characteristics are used to characterize the position and orientation of MCF. Material frame corresponding to the ribbon is established, and quantitative analysis is realized by the differential equations between frame basis vectors and fiber deformation parameters. Bending, twisting-strain model is established according to the approximate development of the twisted MCF, and the deformation parameters are obtained. Further, position and orientation of MCF can be reconstructed under the interference of twisting deformation. In simulation, the influence of curvature, torsion of target curves and twist bias, twisting deformation of MCF on curve reconstruction is analyzed. The results indicate that the proposed model is applicable to curves with zero curvature and variable curvature. With 10 rad/m sinusoidal twisting deformation, the deterioration of reconstruction accuracy can be effectively suppressed by introducing twist bias into MCF. For S-shaped curve with curvature and torsion within 1–50 m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup> and −10-10 rad/m, the tip position error and tip orientation error are less than 5 mm and 5 mrad over the length of 1 m.

Designing 1D correlated-electron states by non-Euclidean topography of 2D monolayers

Two-dimensional (2D) bilayers, twisted to particular angles to display electronic flat bands, are being extensively explored for physics of strongly correlated 2D systems. However, the similar rich physics of one-dimensional (1D) strongly correlated systems remains elusive as it is largely inaccessible by twists. Here, a distinctive way to create 1D flat bands is proposed, by either stamping or growing a 2D monolayer on a non-Euclidean topography-patterned surface. Using boron nitride (hBN) as an example, our analysis employing elastic plate theory, density-functional and coarse-grained tight-binding method reveals that hBN’s bi-periodic sinusoidal deformation creates pseudo- electric and magnetic fields with unexpected spatial dependence. A combination of these fields leads to anisotropic confinement and 1D flat bands. Moreover, changing the periodic undulations can tune the bandwidth, to drive the system to different strongly correlated regimes such as density waves, Luttinger liquid, and Mott insulator. The 1D nature of these states differs from those obtained in twisted materials and can be exploited to study the exciting physics of 1D quantum systems.

More Powerful Twistron Carbon Nanotube Yarn Mechanical Energy Harvesters.

Stretching a coiled carbon nanotube (CNT) yarn can provide large, reversible electrochemical capacitance changes, which convert mechanical energy to electricity. Here, it is shown that the performance of these "twistron" harvesters can be increased by optimizing the alignment of precursor CNT forests, plastically stretching the precursor twisted yarn, applying much higher tensile loads during precoiling twist than for coiling, using electrothermal pulse annealing under tension, and incorporating reduced graphene oxide nanoplates. The peak output power for a 1 and a 30Hz sinusoidal deformation are 0.73 and 3.19kWkg-1 , respectively, which are 24- and 13-fold that of previous twistron harvesters at these respective frequencies. This performance at 30Hz is over 12-fold that of other prior-art mechanical energy harvesters for frequencies between 0.1 and 600Hz. The maximum energy conversion efficiency is 7.2-fold that for previous twistrons. Twistron anode and cathode yarn arrays are stretched 180° out-of-phase by locating them in the negative and positive compressibility directions of hinged wine-rack frames, thereby doubling the output voltage and reducing the input mechanical energy.

Vibration Suppression of the Viscoelastic Sandwich Doubly-Curved Shells Using Magnetostrictive Layers Subjected to Kerr’s Foundation

This research presents a novel model to examine the vibration and deflection analysis of the visco-magnetostrictive doubly-curved sandwich shell subjected to Kerr’s foundation. The shell has a homogenous core with two magnetostrictive layers and two viscoelastic faces. A velocity feedback control process is applied to reduce the vibration of the system using an active strategy. In the present model, active (magnetostrictive materials) and passive (viscoelastic materials) strategies are applied together to suppress the vibration of the sandwich shell. Simple sinusoidal deformation theory (SSDT) is dedicated to inspecting the shear impacts along with the thickness of the sandwich shell. Hamilton’s axiom and Kelvin–Voigt relation are dedicated to achieving the governing equations of motion. Then, the Navier solution technique is dedicated to deriving the eigenfrequency of the sandwich shell with simply-supported (S-S) boundary conditions. The results indicate that the present model can improve the vibration reduction of the curved structures by using the amalgamation of the passive and active strategies. Also, the application of Kerr’s foundation has a major impact on the vibration reduction of the system.

Pimples reduce and dimples enhance flat dielectric surface image repulsion.

In solid-liquid, or liquid-liquid, interfaces with dielectric contrast, charged particles interact with the induced polarization charge of the interface. These interactions contribute to an effective self-energy of the bulk ions and mediate ion-ion interactions. For flat interfaces, the self-energy and the mediated interactions are neatly constructed by the image charge method. For other geometries, explicit results are scarce and the problem must be treated via approximations or direct computation. The case of interfaces with roughness is of great practical importance. This article provides analytical results, valid to first-order in perturbation theory, for the self-energy of particles near rough substrates. Explicit formulas are provided for the case of a sinusoidal deformation of a flat surface. Generic deformations can be treated by superposition. In addition to results for the self-energy, the surface polarization charge is presented as a quadrature. The interaction between an ion and the deformed surface is modified by the change in relative distance as well as by the local curvature of the surface. Solid walls, with a lower dielectric constant than the liquid, repel all ions. We show that the repulsion is reduced by local convexity and enhanced by concavity; dimples are more repulsive than pimples.

Glare: A free and open-source software for generation and assessment of digital speckle pattern

Generating digital speckle image and its corresponding deformed image is the basis of digital image correlation research. At present, however, it still lacks a powerful, easy-to-use, and user-friendly professional software concerning generation and assessment of digital speckle pattern. Researchers have to reimplement the generation algorithms in literature by themselves, which is time-consuming and error-prone. This paper reports a free and open-source software, Glare, for generation and assessment of digital speckle pattern. Glare has functions including generating speckle patterns, rendering deformed images, assessing pattern quality, and presenting pattern recommendations: Glare can generate ellipse, polygon, and Gaussian speckle patterns; can render deformed images with underlying deformation fields of translation, stretch/compression, rotation, sinusoidal deformation, Gaussian deformation, and Portevin-Le Chatelier band deformation; can calculate key pattern quality assessment parameters such as speckle coverage, speckle size, systematic error, and random error; can produce optimized speckle pattern in form of vector image. The software realizes real-time deformed image rendering with the aid of fast initial value estimation algorithm for backward mapping and pattern pre-rendering technique, and improves the computational efficiency of sum of square of subset intensity gradients by integral image method. In general, the software can be used not only for scientific research and engineering applications in digital image correlation community but also for education of experimental mechanics, and therefore has broad prospects.

Analysis on the influence of sinusoidal wind on the structure of pumping unit based on dynamics of solid-fluid interaction

China National Petroleum Corporation Dingbian oilfield is located in the wind field area of the beam pumping unit affected by the wind load, occurred several pumping unit bracket bending, beam fracturing, horsehead off and horsehead drop and other serious accidents, endanger the equipment and personnel safety. However, there is little research on the influence of beam pumping unit under wind load. Based on the dynamics of solid-fluid interaction theory and the standard k- turbulence model, this paper calculated the polished rod load range of the pumping unit according to the actual working condition of Dingbian oilfield, and established the CYJ10-4.2-53 numerical model of wind field. Under the sinusoidal variable wind speed conditions, the stress and deformation of the beam loader with different sizes of wind load on the beam loader were compared to those of the different sorts. The stress and deformation of the two different types of pumping unit were compared under the wind load. The results show that under the influence of wind load, the rig of the pumping unit bracket has a serious bending deformation, and the safety risk of the front end of the horsehead along the wind load is deformed. When the wind speed reaches 24.48m/s, the horsehead and barcket’s offset is the largest to the top dead point by the wind load, The minimum impact is affected by the wind load at the bottom dead center, The maximum offset of the horsehead and the bracket reached 8.5 mm and 2.16 mm. The research work of this paper provides a scientific basis for the improvement of safety structure for pumping unit in the wind field area.

Modelling and analysis of the effect of nonlinear time-varying contact deformation on flexible precision grinding process

Belt grinding is gradually considered to be an effective method for precision machining those aeronautical parts with weak rigidity and complex surface. However, the characteristic of flexible grinding makes it difficult to precisely control the machining process and hinders its further development. In this paper, a series of detailed numerical studies are conducted to study the effect of complex contact deformation on the flexible precision grinding operation of titanium alloy. The flexible process of belt grinding was simulated numerically, and the spatial trajectory equation of abrasive grains in nonlinear time-varying contact state was obtained. Subsequently, the finite element simulation modelling and analysis of a single abrasive grain cutting titanium alloy workpiece under three different boundary conditions (no contact deformation, sinusoidal transformation contact deformation, nonlinear time-varying contact deformation) were performed. The characteristics of grinding morphology and the variation trends of grinding force obtained by simulation were almost consistent with the results of scratch experiments. On this basis, a series of orthogonal simulation studies were conducted to obtain the optimal processing parameters of belt grinding, in consideration of the changes in the spatial positions of abrasive grains caused by the time-varying contact deformation. The above research provides a theoretical framework for investigating the effect of nonlinear time-varying contact deformation, which is of great significance to reveal the mechanism of belt flexible grinding and expand its application in precision machining of aviation parts.

Fourier Transform (FT) Analysis of the Stress as a Tool to Follow the Fatigue Behavior of Metals

This work investigates the possibility of applying Fourier Transform (FT) analysis of the force signal to follow fatigue behavior of metals under oscillatory displacement-controlled tests in uniaxial tension/tension. As a first step, three different materials were selected (cold rolled steel, aluminium and brass). The FT analysis revealed a low level of nonlinearities in the force response, which was possible to measure and quantify as higher harmonics of the imposed sinusoidal deformation. Due to geometric reasons, the odd higher harmonics represent the symmetric nonlinearity while even ones are related to asymmetry, so both odd and even harmonics need to be analyzed separately. The time evolution of the higher harmonics showed that the odd higher harmonics continuously increase during the test. Criteria to better predict the mechanical fatigue and failure (life time) are then proposed based on the integral and derivative based on the time evolution the odd higher harmonics. In contrast, for tests in the high cycle fatigue regime, the even higher harmonics are mainly noise at the beginning of the test (undamaged state), but start to rise after the occurrence of a crack due to internal crack friction. Based on the analysis performed, FT analysis of the force during mechanical fatigue testing of metals is a sensitive tool used to predict failure and to improve our understanding of the dynamics involved in mechanical fatigue.