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The well completion and fracturing towards deep unconventional high-temperature (HT) petroleum or natural gas reservoirs is considerably strict to the packer especially packing elements. However, existing packing elements including swellable packers usually are made from Hydrogenated Nitrile (HNBR) or Fluorine rubber (FKM) with drawbacks of great expense and difficult tripping into the horizontal wellbore. This paper proposes a compact isolating solution using swellable Thermo-plastic Vulcanizates (TPVs), which is prepared by blending HNBR, low-cost Polyamide66 (PA66) and Porous Super Absorbent Resin (PSAR) with enhanced nanoparticles. The TPVs were characterized by experiments and the system with Plastic/Elastomer Ratio (PER) of 45:55, tensile strength of 18.6 MPa and elongation at break of 635% upon aging (150 °C) was qualified for the packing element material. A novel enhanced packing element is put forward with corrugated-profile structure to address large-size and over-extrusion issues. The numerical study on packer components was conducted based on TPV constitutive model. The prototype with element length of 2.5–2.6 m was validated in the lab and rated as the sealing of more than 70 MPa. An optional disintegrating casing is adopted to avoid the premature damage risk of packers. For the field trial, the multistage fracturing tubular with improved packers was deployed into the horizontal open hole without severe pipe stuck. The fracturing operation was successfully performed and all packers functioned normally with the maximum pressure differential of 73 MPa. It concludes that the new solution exhibited high strength, heat resistance and structure integrity with low cost over the traditional packers towards HT environment.

This study proposes an active-controlled hydraulic low-frequency vibration isolator. The vibration isolator can achieve large equivalent mass and quasi-zero dynamic stiffness by combining the fluid inerter with the hydraulic active compensation. Thus, good vibration isolation performance at ultra-low frequency can be realised. The model for the dynamics of the device is set up. The principle of low-frequency vibration isolation is explicated. The natural frequency and its influencing factors are analysed. Finally, preliminary experimental research works are carried out. The results indicate that low-frequency vibration can be effectively isolated by the device proposed in this study.

Recently, a novel method for mechanical energy harvesting has been proposed, which is based on stress-induced polarization switching in ferroelectric materials. Compared with the traditional piezoelectric energy harvesters, a huge improvement in the output energy has already been theoretically demonstrated. In this article, the influence of different materials on the energy-harvesting performance associated with this new strategy is further studied. The state-of-the-art phase-field model is adopted to investigate the nonlinear hysteretic energy-harvesting process in two nanoscale ferroelectric energy harvesters, which are respectively based on two typical ferroelectric materials—single-crystal BaTiO3 and PbTiO3. In both cases, the effects of the bias voltage and bias resistance are carefully investigated and the optimum values are obtained. Later, the energy-harvesting process and energy flow details in both harvesters working at the optimum conditions are presented and carefully compared in the context of real applications. Furthermore, the energy-harvesting performance of a BaTiO3-based nanoscale piezoelectric energy harvester with equivalent material size is additionally simulated with the finite element method and compared with the corresponding results of the ferroelectric energy harvesters, where obvious advantages associated with the new strategy are demonstrated.

Many studies have used numerical models, analytical models and laboratory models to investigate the factors influencing the shear strength of bolted rock joints. This study presents the preparation of a reinforced standard cylindrical specimen containing a joint; the jointed specimen was reinforced with a 3D printed (3DP) rock bolt and planting-bar anchorage glue. The surface profile of the 3DP rock bolt was identical to that of an actual rock bolt, and the strength of the 3DP bolt was satisfactory. Afterwards, the digital image correlation (DIC) method was applied to capture the changes in the strain/displacement fields on the surfaces of the specimens during testing. In addition, two pressure sensors (PSs) were attached to the external threaded sections of each 3DP bolt; these PSs recorded the changes in the load at the bolt ends positioned in the upper section above the joint plane and in the lower section below the joint plane. The influences of the joint plane and joint angle on the cracking process, DIC changing pattern, and stress-strain evolution were comprehensively discussed. The research approaches proposed in this study provide new methods with which to investigate the reinforcement effect of bolts on jointed rock masses, the results of this study can be used as a reference in engineering areas where jointed rock masses must be reinforced by rock bolts.

In this paper, a quick response artificial finger actuated by SMA springs was designed. The SMA springs were heated and cooled by water instead of electricity. A mechanical model, temperature model and SMA phase transformation model were used to predict the movement. The phalanx’s response under different situation was simulated in MATLAB to verify our design and test the feasibility of the quick response of our finger.

This paper is an extended study on the model of the hysteretic dynamics of magnetorheological dampers based on a phenomenological phase transition theory (Wang and Kamath in Smart Mater. Struct. 15(6):1725–1733, 2006). It is demonstrated that, by appropriately choosing model parameters, the frequency dependence of the hysteretic dynamics can be captured very well by the model based on phase transition theory. Whilst by introducing an appropriate rescaling coefficient to account for the strength of the magnetized particle chains with various magnetic field strengths, the field strength dependence of the hysteretic dynamics can also be captured very well by the same differential equation with the same set of model parameters. There are in total eight model parameters introduced for capturing the hysteretic dynamics, including its dependence on the loading rate and field strength.

In the most of its engineering applications, ferroelectric materials are often subjected to combined loadings in the electric and mechanical fields. To simulate the influence of the biased stresses on the hysteretic dynamics of the materials, a macroscopic differential model is proposed to model the hysteresis loops and butterfly-shaped behaviors caused by the polarization orientation switching with biased stresses. A group of numerical simulations are presented, and the comparison of theoretical results with its experimental counterparts is also presented.

The concept of energy harvesting works towards developing self-powered devices that do not require replaceable power supplies. Energy scavenging devices are designed to capture the ambient energy surrounding the electronics and convert it into usable electrical energy. A number of sources of harvestable ambient energy exist, including waste heat, vibration, electromagnetic waves, wind, flowing water, and solar energy. While each of these sources of energy can be effectively used to power remote sensors, the structural and biological communities have placed an emphasis on scavenging vibrational energy with ferroelectric materials. Ferroelectric materials have a crystalline structure that provide a unique ability to convert an applied electrical potential into a mechanical strain or vice versa. Based on the properties of the material, this paper investigates the technique of power harvesting and storage.

In the current paper, three different constitutive models are employed for the analysis of laminar MRF (MagnetoRheological Fluid) flows between two parallel plates. The capability of a recently constructed non-convex constitutive model is compared with those of widely used Bingham model and Herschel-Bulkley model. The comparison among simulated flow velocity distributions and shear stress - shear strain rate characteristics based on different models is presented. It is shown that the non-convex consitutive model outperformance the other two models.

The loading rate dependency of the hysteretic dynamics of Magnetorheological (MR) dampers is investigated in the current paper. The model is constructed on the basis of a phenomenological phase-transition theory. The hysteretic dynamics is treated as the responses of a nonlinear system upon external loadings. With appropriately chosen coefficients, the proposed model is able to capture the loading-rate dependency feature of the hysteretic dynamics. Comparisons between the numerical and experimental results are presented, and perfect agreements are obtained.

Polycrystalline LuAG: Ce 3+ (cerium 3+ -doped lutetium aluminum garnet) powders were prepared by mixed solvo-thermal method. Fourier-transform IR spectroscopy (FTIR) and X-ray diffraction (XRD) measurements showed that the precursors were ethanol derivatives AlO(OH) crystal with hydroxyl and carbonate group. XRD results showed that phase of Lu 2 O 3 disappeared with the precursors were annealed at 400 °C, cubic phase LuAG: Ce 3+ appeared but only one diffraction peaks of LuAP (LuAlO 3 ) at calcination temperature to 700 °C, and the purified crystalline phase of LuAG:Ce 3+ was obtained at 1000 °C. The scanning electron microscopy (SEM) analysis revealed that the synthesized LuAG:Ce 3+ powders were uniform and had good dispersivity with an average particle size about 100 nm. Excitation and emission spectra of Ce 3+ doped LuAG phosphors were measured. Many factors of affecting the intensity of emission spectra were discussed.

An optical device is used to scan a cavity. In a single incident the scanner produces what can be considered a blurred image of the intersection curve between a plane and the cavity. Mathematically the image represents an intensity function and that is obtained by integrating a certain kernel along the intersection curve. We suggest methods to determine the kernel and subsequently the intersection curve given the image. The methodology is tested with some success using an artificial, but realistic kernel and some synthetic images produced by this kernel.

Migration of orthopedic fixation wires into the ascending aorta though a rare occurrence can have devastating consequences. Therefore, prompt recognition, with immediate and cautious retrieval of the implant is paramount in averting these complications.We present a case of a 5-year-old boy with the intra-aortic migration of a K-wire used for the treatment of a right clavicle fracture. He was transferred to us with a history of syncope, chest pain, and shortness of breath 7 days after K-wire placement, which was performed at another hospital. On CT scan, the wire was found to be partially inside the ascending aorta, which was associated with massive hemopericardium and cardiac tamponade. The patient was taken up for emergency surgery for the removal K-wire and for the management of cardiac temponade. However, the patient developed cardiac arrest during the induction of intravenous anesthesia and endotracheal intubation. The K-wire was retrieved from the thorax via thoracotomy. However, the patient died 10 days after the surgery.As the migration of wires and pins during orthopedic surgery can cause potentially fatal complications, these should be used very cautiously, especially for percutaneous treatment of shoulder girdle fractures. The patients with such implants should be followed frequently, both clinically and radiographically. If migration occurs, the patient should be closely monitored for emergent complications and the K-wire should be extracted immediately.

Shape memory alloy (SMA) is one of the novel advanced functional materials that has an increasing range of current and potential applications, including smart materials and structures, bio-medical and nanotechnologies. This range includes also applications of SMA for control and vibration tuning of various structures, seismic response mitigation, and others. In vibration tuning in many of these applications, it is often necessary to apply supplementary oscillators to absorb the vibration energy input into the primary system. Moreover, when supplementary oscillators are used in these applications, we often have to deal with a situation where the primary vibration frequency is not known a priori. In such cases, we have to design a robust supplementary oscillator such that it is able to operate in a rather wide range of frequencies. A SMA-based oscillator is an ideal candidate for these purposes. In the present paper, we propose a dynamic nonlinear model and its numerical realization for using SMA oscillators as vibration absorbers. The system under consideration consists of a SMA rod and an end-mass. We demonstrate that due to the thermo-mechanical coupling, the vibration characteristics of the supplementary oscillator can be tuned by changing its temperature. The dynamic nonlinear model of the SMA oscillator is simplified for the vibration analysis and an efficient numerical methodology is proposed to evaluate the performance of the oscillator. It is demonstrated that the vibration of the primary system can be tuned within a rather wide frequency range by using the SMA oscillator. It is also shown that at high temperatures the performance of the oscillator is close to that of a linear oscillator, while at low temperatures, the SMA oscillator behaves as a regular damper by using its dissipation due to mechanically-induced phase transformations.

We discuss a relatively simple and computationally inexpensive model that has recently been developed to study phase transformations and shape memory effects in finite nanostructures. Our major focus is given to nanowires of finite length and other nanostructures where size effects are pronounced. The main tool used here is based on mesoscopic models developed with the phase-field approach which we and other authors have applied before to study ferroelectrics at the nanoscale. We study the cubic-to-tetragonal transformations in which case the 2D analogue of the model describes the square-to-rectangle phase transformations. The actual model is based on a coupled system of partial differential equations and is solved with a combination of the Chebyshev collocation method and the extended proper orthogonal decomposition. The developed model and its numerical implementation allow us to study properties of nanostructures and several representative examples of mechanical behavior of nanostructures are discussed.

In the current paper, a macroscopic differential model is constructed for the modeling of two-way shape memory effects in one-dimensional shape memory alloy (SMA) structures. The model is based on the phenomenological theory of thermoelastic phase transformations in SMAs. Hysteresis loops in both mechanical and thermal fields are treated as macroscopic illustrations of martensite transformations and martensite variant re-orientations. A non-convex free energy function is constructed such that each of its local equilibriums can be used to characterize one of the phases involved in the transformations. System states (strain) can be transformed upon external loadings (mechanical or thermal) from one stable equilibrium to another, thus the dynamics of phase transformations can be modeled by investigating the system state transformations. Governing equations for the transformation dynamics are formulated by employing the Lagrange's equation, and are expressed as nonlinear differential equations. Numerical examples of thermal and mechanical hysteresis loops associated with the transformations caused by thermal and mechanical loadings are presented. Two way shape memory effects and pseudo-elastic effects are successfully modeled.

A one-dimensional model accounting for electrostriction, lattice mismatch, piezoelectricity, and strain is presented with special emphasis on GaN/AlN heterostructures recently examined extensively in the literature. It is shown that electrostriction, being a second-order effect in the strain–electric field relation, plays a significant, sometimes dominant contribution subject to DC voltage conditions and externally imposed hydrostatic pressure. Model results are based on experimentally reported values for electrostriction coefficients in GaN.

In the current paper, the hysteretic dynamics of ferroelectric materials under combined electro-mechanical loadings is investigated using a macroscopic differential model. The model is constructed on the basis of the Landau theory of the first order phase transformations. Hysteresis loops in the electric field and the butterfly-shaped behaviors in the electro-mechanical coupling are modeled as a consequence of polarizations and orientation switchings, together with nonlinear electro-mechanical coupling effects. The effects of bias stress on the orientation switchings are investigated numerically. Comparison of the model results with its experimental counterparts is presented, capability of the model is approved.Copyright © 2008 by ASME