Minimum Displacement Research Articles

A walking type piezoelectric actuator based on the parasitic motion of obliquely assembled PZT stacks

In order to decrease the backward motion and improve the motion efficiency, a walking type piezoelectric actuator has been proposed with two ‘legs’ based on the parasitic motion of obliquely assembled PZT stacks. The structure and motion principle of the proposed walking type piezoelectric actuator are described, and its experiment system is set up. Experimental results indicate the proposed piezoelectric actuator could reduce the backward motion effectively. The minimum backward rate α= 2.26% is achieved under the condition of the phase difference θ= 180°, the input voltage U= 120 V and the input frequency f= 1 Hz; the minimum stepping displacement is 0.24 μm under the condition of U= 5 V, f= 1 Hz and θ= 180°; the maximum speed V max is 2472 μm s−1 under the condition of U =120 V and θ= 180°; the maximum vertical load force F Vmax = 6850 g under the condition of U = 120 V, f = 1 Hz and θ = 180°. Furthermore, a dynamic model of the whole walking type piezoelectric actuator is established, and it has been employed to simulate the motion of the proposed walking type piezoelectric actuator. Simulation results present a great agreement of experimental results. This study shows a novel idea for the design of piezoelectric actuators to eliminate the influence of backward motion and improve the output efficiency of the actuator.

Full energy range primary radiation damage model

A full energy range primary radiation damage model is presented here. It is based on the athermal recombination corrected displacements per atom (arc-dpa) model but includes a proper treatment of the near threshold conditions for metallic materials. Both ab initio (AIMD) and classical molecular dynamics (MD) simulations are used here for various metals with body-centered cubic (bcc), face-centered cubic (fcc), and hexagonal close-packed (hcp) structures to validate the model. For bcc and hcp metals, the simulation results fit very well with the model. For fcc metals, although there are slight deviations between the model and direct simulation results, it is still a clear improvement on the arc-dpa model. The deviations are due to qualitative differences in the threshold energy surfaces of fcc metals with respect to bcc and hcp metals according to our classical MD simulations. We introduce the minimum threshold displacement energy (TDE) as a term in our damage model. We calculated minimum TDEs for various metal materials using AIMD. In general, the calculated minimum TDEs are in very good agreement with experimental results. Moreover, we noticed a discrepancy in the literature for fcc Ni and estimated the average TDE of Ni using both classical MD and AIMD. It was found that the average TDE of Ni should be \ensuremath{\sim}70 eV based on simulation and experimental data, not the commonly used literature value of 40 eV. The most significant implications of introducing this full energy range damage model will be for estimating the effect of weak particle-matter interactions, such as for \ensuremath{\gamma}- and electron-radiation-induced damage.

Simulation Analysis of Additive Manufacturing of Impeller

An Impeller is the rotating component of a pump; it transfers the energy from the motor to the fluid and accelerates the fluid to build up pressure. Impellers are manufactured using Additive Manufacturing (AM) technology. It is a technology that produces three-dimensional parts layer by layer from a variety of materials such as plastics, polymers and metals. The impeller is usually made up of Stainless Steel 316L, Inconel 718. AM technique used to manufacture impeller is Direct Metal Laser Sintering (DMLS). The main objective of this paper is to conduct simulation analysis of additive manufacturing of an impeller by varying process-parameters such as Power, Wall-thickness and Angle and recommend a suitable material with minimum von-misses stress, minimum displacement and minimum of maximum temperature using Amphyon software. Simulation analysis is performed on two different materials i.e., Stainless Steel 316L and Inconel 718 by varying process parameters such as Power at 200 to 400W, Wall thickness at 0.5 to 0.8mm and Angle at 00 to 60. Amphyon is a modular pre-processing and simulation software for Laser Beam Melting (LBM) processes. The simulation results were analyzed and optimization for Stainless-Steel 316L material impeller was done using one of the MADM methods i.e., Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) method. Later, the results of the two different materials (i.e., Stainless Steel 316L and Inconel 718) were compared. Stainless Steel 316L was found to have minimum von-misses stress, minimum displacement and minimum of maximum temperature at 200W power, 0.5mm wall-thickness and 00 angle. Index Terms: Impeller, Additive Manufacturing, Direct Metal Laser Sintering (DMLS), Amphyon, MADM, TOPSIS.

How to choose the suitable FNS specification in young patients with femoral neck fracture: A finite element analysis

BackgroundConsensus regarding the optimal approach for the treatment of femoral neck fractures remains lacking. A new internal fixation femoral neck system (FNS) was developed and used in clinical practice. We aimed to investigate the biomechanical outcomes of different types of FNS in the treatment of unstable femoral neck fractures. MethodIn this study, we constructed three different types of unstable femoral neck fractures of Pauwels classification with angles of 50°, 60°, and 70°. We set up four test groups, namely, the one-hole plated FNS group, two-hole plated FNS group, inverted cannulated screw group and triangle cannulated screw group. Under 2100 N axial loads, displacements and the von Mises stress of the femur and internal fixation components were measured for each fracture group. ResultsWhen the Pauwels angle was 50°or 60°, the one-hole locking plated FNS was as superior as the two-hole plated FNS in terms of femur and internal fixation displacement, and the inverted cannulated screw had slightly better stability than the triangular cannulated screw. However, when the angle increases to 70°, the two-hole locking plate has the minimum displacement, followed by the triangular cannulated screw and inverted cannulated screw, which is the worst displacement for the single-hole locking plate. Regardless of the angle, the two sets of FNS have higher internal fixation stress than the two sets of cannulated screws, which is approximately 1.6-3.0 times that of the cannulated screw group. ConclusionFrom the perspective of biomechanics, we suggest that when the angle of the fracture line is less than 60°, both single-hole locking plated or double-hole locking plated FNS can be used to treat unstable femoral neck fractures. However, when the angle of the fracture line is greater than 70°, we recommend using a double-hole locking plated FNS. This result needs further verification in further clinical studies.

Cause identification of damage in tunnel constructed in soil-rock mixture site and effect of suggested reinforcement measures

A running tunnel in Chongqing, China was constructed in a soil-rock mixture (SRM) by the open-cut method. During the construction period, severe cracks occurred on the tunnel lining floor, which will significantly affect the tunnel’s long-term stability. In this study, the numerical investigation was performed to study the development trend of damage zones in the tunnel lining, identifying the causes of damage and further evaluating the effects of suggested reinforcement measures. Firstly, numerical modeling experiments were conducted to obtain the physical and mechanical parameters of SRM. Then, three 3-dimensional (3D) numerical simulation models were established. The settlement, tensile stress, and distribution of damage zones on the tunnel floor were highlighted. Results indicated that the maximum deformation occurs on the roof of the tunnel lining, and the minimum displacement is in the middle part of the tunnel floor. The maximum compressive stress is within the ultimate compressive strength. However, the tensile strength significantly exceeded the ultimate tensile strength, resulting in cracks in the tunnel lining. If no reinforcement measures are taken, about 66% of the tunnel floor will be tensioned to damage, significantly reducing the bearing capacity and long-term stability of tunnel lining. The stiffness difference between SRM and the bored piles is the reason for damage zones in tunnel lining. It is suggested that grouting reinforcement and steel fiber reinforced concrete should be taken on the tunnel floor to improve damage resistance. Finally, it is verified that the suggested reinforcement measures can effectively control uneven settlement and damage zones in the tunnel floor.

An Investigation into the Correlation of Small Punch and Uniaxial Creep Data for Waspaloy

Within the aerospace sector, the understanding and prediction of creep strains for materials used in high-temperature applications, such as Nickel-based super alloys, is imperative. Small punch testing offers the potential for understanding creep behavior using much less material than conventional uniaxial testing but in contrast to uniaxial creep tests, the stress in small punch creep (SPC) tests is multiaxial. SPC testing can be a valuable tool for validating models of creep deformation, but the key to unlocking its full capability is through the accurate correlation of the creep material properties measured through both techniques. As such, the focus of this paper is to correlate the creep behavior of Waspaloy obtained through conventional uniaxial testing to that obtained via small punch creep testing. Recently, and for low chrome steels, this has been achieved through use of the ksp method, but there are good reasons for believing this technique will not work so well for Nickel-based super alloys. This paper shows this to be the case for Waspaloy and proposes some alternative methods of correlation based on combining the Monkman–Grant relation and the Wilshire equations for both uniaxial and small punch creep. It was found that this latter approach enabled the accurate conversion of SPC minimum displacement rates to equivalent uniaxial minimum creep rates which, when combined with the Wilshire equations, enabled SPC test loads to be converted into equivalent uniaxial stresses (and visa versa) with levels of accuracy that were significantly reduced when compared to using the ksp method. Further, the random error associated with these conversions were dramatically increased.

Investigations on the actuation behaviour of friction stir–welded nickel titanium shape memory alloy using continuous fibre laser

The friction stir welding (FSW) is found to be an effective solid-state process to join Nickel Titanium (NiTi) shape memory alloy. The retention of shape memory effect has enabled the welded NiTi alloy to be exploited in various functional applications. In this article, the NiTi sheets of 1.2 mm thickness are welded using FSW. The tool selection, geometry design and process parameters required to weld NiTi sheets are explored. Interestingly, an attempt is made to actuate the welded NiTi alloy, using laser actuation technique. The laser beam is scanned over the sample at a particular speed, enabling the increase in temperature suitable for physical actuation. A minimum and maximum displacement of 10 mm and 28 mm are recorded for the laser powers of 10 W and 50 W, respectively. Apart from laser actuation, the dynamic mechanical analysis of the welded NiTi alloy is investigated.

Design, sensing principle and testing of a novel fiber optic displacement sensor based on linear macro-bending loss

This paper presents a linear fiber optic displacement sensor for the use over a large range based on the macro-bending loss. The sensor incorporates an extremely simple design, light source and detector. A concentric gear shaft is used to bend the fiber and transfer the displacement. The linear relationship between the measured displacement and the bending loss of optical fiber was proved theoretically and its expression was derived. A series of calibration experiments and performance tests were conducted. The experimental results show that the sensor was characterized by a wide measurement range, a high sensitivity and a minimum displacement resolution of 0–200 mm, 0.1668 dB/mm and 0.06 mm, respectively. The stability and repeatability of the sensor was verified by repetitive testes with a maximum measurement deviation of 0.162 mm. The predicted displacements of the sensor were similar to the actual values, and the difference errors of all samples are basically within 10%. These characteristics demonstrate that the sensor can be used for displacement monitoring for large-scale civil structures and has a promising prospect.

Parametric study of structural parameters affecting seismic stability in slopes reinforced by pile-anchor structures

Parametric study was performed on the seismic stability of pile-anchor slope reinforcement structures for earth retaining wall with different structural parameters. Dynamic finite element analysis and the Newmark permanent displacement method were combined to derive the dynamic time-history response of the pile-anchor structure and evaluate slope seismic stability. The effects of pile embedment, pile thickness, anchor position on the pile, anchor free length, anchor direction and anchor prestress were investigated by batch calculation under different structural conditions, and optimized design suggestions are proposed based on the numerical study. The quantitative analysis indicates that Newmark permanent displacement can effectively evaluate slope stability under seismic loading and provide an accessible approach to improve the performance-based design of pile-anchor structures. For the generalized vertical soil slope prevalent in actual slope engineering, considering the maximum factor of safety and minimum permanent displacement, it was found that the most optimized embedded depth occupies approximately 30% of the whole pile length in the soil slope, and the pile thickness is set as 1.5–2 m for superior shear and bending strength. In addition, there is a critical anchor position 3 m beneath the pile top, a threshold free length of the anchor cable of 9.5 m, as well as an optimal direction within the range of 15°–20°. Furthermore, the pile-anchor structure shows better sliding resistance with rational anchor prestress accounting for 20% of the sliding force. The slope seismic stability evaluation based on dynamic finite element analysis with different pile-anchor structural parameter conditions performed in this paper may lay a foundation for the design optimization of pile-anchor reinforcement structures for better dynamic performance.

Review of Trajectory Planning for Industrial Robots

More and more industrial robots need high-precision trajectory control, but the traditional PID control is difficult to achieve. The simulation diagram and pose of the collision free mechanism are drawn by using rosty software. At the same time, through the experiment of MOTOMAN-HP3 robot, using VC + + application program to call the external interface function of motocom32 software, the application program planning is realized. The linear and circular trajectory planning of industrial robot in Cartesian space is studied. Linear interpolation algorithm based on spatial parabola transformation and circular interpolation algorithm based on local coordinates are proposed. The algorithm is applied to a self-designed 5-DOF spraying robot. An evolutionary algorithm based optimal trajectory planning method for PUMA560 robot is proposed. The method is based on the elite non dominated sorting genetic algorithm (NSGA-II). The results show that the minimum angular displacement, angular velocity and angular acceleration of X3 parallel robot are 56, and the maximum angular displacement, angular velocity and angular acceleration are 89.

Properties of Polyhedral Oligomeric Silsesquioxane-Modified Cellulose Insulation Paper with Different Number of Phenyls

Polyhedral oligomeric silsesquioxane (POSS) has a total of eight substituents. The number of substituents determines the modification effect of POSS. Through simulation of molecular dynamics, this paper explores how the number of substituents affects the POSS-modified cellulose insulation paper. Specifically, the mechanical properties, thermal stability and polarizability were calculated for cellulose models with 1-phenyl POSS, 2-phenyl POSS, 3-phenyl POSS, 4-phenyl POSS, 5-phenyl POSS, 6-phenyl POSS, 7-phenyl POSS, and 8-phenyl POSS, respectively. The results show that the cellulose model modified by 6-phenyl POSS achieved better effect than the other seven models, as evidenced by its distinctively large bulk modulus, shear modulus, and elastic modulus. Besides, the cellulose model modified by 6-phenyl POSS had the most stable and the minimum mean square displacement (MSD). This is because the mechanical properties of the insulation paper are improved, as the motion of cellulose chains is inhibited by the nano-size effect of POSS and the effect of phenyls. Further, the cellulose model modified by 6-phenyl POSS also had the smallest polarizability among the modified models. Therefore, the 6-phenyl POSS-modified cellulose model can effectively reduce the polarizability of cellulose, uniform the electric field distribution in oil-paper insulation system, and thus enhance the insulation property of transformers.

A reaction diffusion-based level set method using body-fitted mesh for structural topology optimization

The level set method can express smooth boundaries in structural topology optimization with the level set function’s zero-level contour. However, most applications still use rectangular/hexahedral mesh in finite element analysis, which results in zig-zag interfaces between the void and solid phases. We propose a reaction diffusion-based level set method using the adaptive triangular/tetrahedral mesh for structural topology optimization in this work. Besides genuinely expressing smooth boundaries, such a body-fitted mesh can increase finite element analysis accuracy. Unlike the traditional upwind algorithm, the proposed method breaks through the constraint of Courant–Friedrichs–Lewy stability condition with an updating scheme based on finite element analysis. Numerical examples for minimum mean compliance and maximum output displacement at specified positions, in both 2D and 3D, converge within dozens of iterations and present elegant structures.

Native signal self-mix interferometer has less than 1 nm noise equivalent displacement.

We demonstrate that the native configuration of a self-mixing interferometer attains a minimum detectable displacement of 0.72 nm or λ/1870 at the laser wavelength of 1310 nm, obtained by the bare laser diode package including a monitor photodiode, observed in the electrical domain by means of an oscilloscope and without any electronic processing of the signal.

Fatigue delamination growth characterization of a directly bonded carbon-fiber-reinforced thermoplastic laminates and aluminum alloys with surface nanostructure using DCB test

With the recent demand for weight reduction, structural materials for transportation equipment are being replaced by carbon-fiber-reinforced thermoplastics (CFRTPs). Therefore, techniques to join CFRTPs to alloys are needed. In this study, the fatigue delamination growth of bonded CFRTP/aluminum alloy joints was characterized. The specimens were bonded in three ways, using adhesive, direct chemical bonding, and direct chemical bonding with a nanostructured surface. The type of the specimen was double cantilever beam (DCB) specimen, which consisted of aluminum alloy (A5052) and plain woven CFRTP. The lay-up of the CFRTP was [(0,90)]9 and the used matrix was PA6. Fatigue loading was applied in displacement control mode. The ratio between the minimum and maximum displacement was 0.1, and the test frequency was 5 Hz. The crack length during the fatigue tests was obtained by compliance calibration. Fatigue was characterized by constructing a Paris diagram for each specimen type. The fracture surface distinctively changed from smooth brittle-like fracture to hair-like ductile fracture post fabricating a nanostructure and chemical bonding. As a result, the fatigue crack growth resistance of the specimen with the nanostructure significantly improved due to the hair-like ductile fracture.

Numerical Analysis and Experimental Investigation on a Novel Piezoelectric-Actuated Rail-Type Mobile Platform

A novel piezoelectric-actuated rail-type mobile platform is proposed in this article, which has potential application in the inspection and maintenance tasks of the Tokamak vacuum vessel as it holds good environmental adaptability to extreme environments, such as strong magnetic fields, high vacuum, and high temperature. The rail-type piezoelectric-actuated mobile platform consists of a rail and a framed piezoelectric actuator operating with two orthogonal bending vibrations. The framed piezoelectric actuator moves on the rail by friction. At first, a semianalytical model is created for the framed piezoelectric actuator utilizing the transfer matrix method in order to reveal its dynamic behavior. Then, the prototype of the proposed framed piezoelectric actuator is manufactured and assembled, and its vibration characteristics are measured to verify the feasibility of the developed transfer matrix model. Additionally, the mechanical output performances of the rail-type mobile platform prototype are investigated experimentally, and it is observed that the maximum speed of the mobile platform prototype reached 384.68 mm/s when the amplitude of the driving voltage is 400 V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">pp</sub> , its maximum load-weight to self-weight ratio reached 7.6 when the excitation voltage is 300 V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">pp</sub> , its maximum output force is about 1.8 N under the excitation voltage of 400 V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">pp</sub> , and the minimum displacement resolution is 4 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">μ</i> m when operated in the stepping mode. Finally, the extreme environment (temperature: 0–120 °C and vacuum: 3×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−3</sup> –10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sup> Pa) tests are carried out to measure the output performances of the mobile platform prototype. The results show that the platform prototype is capable of carrying loads in a high-temperature and high-vacuum environment.

Research on deep foundation pit excavation based on numerical simulation

The safety of deep foundation pit excavation has always been an important topic of urban construction safety. The traditional method is to control the construction safety by monitoring and adjusting the construction process, but the timeliness of monitoring makes it limited in the control of construction safety. In this paper, MIDAS / GTS software is used to simulate the excavation process of a hospital foundation pit in Guiyang. The maximum horizontal displacement in X direction is 4.03mm, and the minimum is -4.78mm. The maximum horizontal displacement in Y direction is 4.41mm, and the minimum horizontal displacement is - 4.9mm. Through the study of the common horizontal X and Y displacement nephogram of crown beam, waist beam and anchor, the synergistic effect can be well expressed. The maximum horizontal displacement in X direction is 5.56mm. The minimum horizontal displacement is - 3.54mm. The maximum horizontal displacement in Y direction is 6.56mm. The minimum horizontal displacement is - 4.45mm. By comparing the numerical simulation results with the field measurement results, the reliability of the numerical simulation in the evaluation of the foundation pit is fully proved.

A hybrid 3D particle matching algorithm based on ant colony optimization

Particle Tracking Velocimetry (PTV) is a popular optical method to measure the velocity field of complex flow at high spatial resolution. One of the practical limitations of this technique is that in general, the accuracy of matching individual particles between a pair of images is limited by the particle image displacement. To deal with this limitation, the present work proposed a hybrid ant colony optimization (ACO) algorithm for particle matching in three-dimensional (3D) scenarios . It can be regarded as an update of the conventional ACO PTV algorithm (Takagi J Vis 27:89–90. https://doi.org/10.3154/jvs.27.Supplement2_89 , 2007, Ohmi et al. Exp Fluids 48(4):589–605. https://doi.org/10.1007/s00348-009-0815-2 , 2010). The key concept is to seek a global solution of the minimization of a displacement-pattern function (DPF) via improved ant colony optimization (ACO). The object function, i.e., DPF, hybrids the measure of particle image displacement and the measure of pattern similarity as the particle matching criterion, the latter of which is constructed as the similarity level of Voronoi polygons (VPs) of paired particles. Performance evaluation was based on both the standard particle image database of Visualization Society of Japan (Okamoto et al. Meas Sci Technol 11(6):685–691. https://doi.org/10.1088/0957-0233/11/6/311 , 2000) and the laboratory-made synthetic flow. It was shown that this hybrid ACO algorithm has higher matching accuracy than those of exiting ACO methods based on either minimum displacement function or relaxation function. Its credibility in dealing with the scenarios of large relative particle displacement, i.e., the cases where particle image displacement is comparable to or even larger than the mean spacing of neighboring particles was also empirically demonstrated. Other features including fast convergence speed and regular pattern of outliers were also seen. All these make this algorithm a suitable candidate for 3D particle matching in PTV.

Optimal Shape Adjustment of Large High-Precision Cable Network Structures

Traditional shape adjustment methods for large high-precision cable network structures usually use many actuators and are only applicable to predictable shape distortions. To this end, a new method, namely, the minimum residual nodal displacement method, for optimal shape adjustment of large high-precision cable network structures is developed. The new shape adjustment method can significantly reduce shape distortion of a cable network structure by automatically placing a small number of actuators at optimal locations. This new method is applicable to cable network structures under both predictable and unpredictable shape distortions, and can determine the minimum number of actuators needed to satisfy prescribed design requirement for surface accuracy. In this method, a simple linear relationship between nodal displacements, external loads, and undeformed member lengths of a cable network structure is established, and residual nodal displacement of the structure is minimized. The effectiveness of this new method is proved in numerical simulation results, where a planar cable network structure and a reconfigurable deployable mesh reflector are investigated.

Development of Complex Ore Zones

The article is aimed at developing a technology for mining valuable ores with maximum preservation of natural contacts of ore zones with empty rocks and reduction of mixing of the rock mass during explosive loosening. A new method for working out local areas of mineralization in strong rocks using explosive loosening of rocks in the conditions of natural "clamping" by a natural array with decelerations between successive bursts of borehole charges above 300 MS is proposed. This allows you to achieve a minimum displacement of the exploded rock mass in both horizontal and vertical directions without any additional costs.

Effects of free heave motion on wave resonance inside a narrow gap between two boxes under wave actions

Fluid resonance inside a narrow gap between two side-by-side boxes is investigated based on an open-source CFD package, OpenFOAM. An upstream box heaves freely under wave actions and a downstream box remains fixed. The focus of this work is to study the influence of the motion of the upstream box on the hydrodynamic behavior of the resonant fluid inside the gap. The hydrodynamic behavior considered in this study includes the wave height inside the gap, heave displacement and their harmonic components, and reflection, transmission and energy loss coefficients. For comparison, the configuration in which the two boxes are fixed is considered. It was found that the heave motion of the upstream box increases the fluid resonant frequency and significantly reduces the resonant wave height in the gap. The frequencies at which the maximum and minimum heave displacements of the upstream box are observed to obviously deviate from the fluid resonant frequency. For the wave height in the gap and heave displacement, the effects of the incident wave height on their harmonic components are different. The heave motion of the upstream box results in a larger reflection coefficient and smaller energy loss coefficient.