Out Of Plane Displacement Research Articles

PopTouch: A Submillimeter Thick Dynamically Reconfigured Haptic Interface with Pressable Buttons.

The interactions with touchscreens rely heavily on vision: The virtual buttons and virtual sliders on a touchscreen provide no mechanical sense of the object they seek to represent. This work presents PopTouch: a 500µm thick flexible haptic display that creates pressable physical buttons on demand. PopTouch can be mounted directly on touchscreens or any other smooth surface, flat, or curved. The buttons of PopTouch are independently controlled hydraulically amplified electrostatic zipping taxels (tactile pixels) that generate 1.5mm of out of plane displacement. When pressed by the user, the buttons provide intuitive mechanical feedback thanks to a snap-through characteristic in their force-displacement profile. The snap-through threshold can be as high as 4 N, and is tuned by design and actuation parameters. This work presents two versions of PopTouch: a transparent PopTouch for integration on Touchscreens with built-in touch sensing, such as smartphones and a sensorized PopTouch, with embedded thin-film piezoelectric sensors on each taxel, for integration on substrates without built-in touch sensing, such as a steering wheel. PopTouch adds static and vibrating button-like haptics to any device thanks to its thin profile, flexibility, low power consumption (6mW per button), rapid refresh rate (2Hz), and freely configured array format.

Ballistic resistance of high-strength armor steel against ogive-nosed projectile impact

The advanced high-strength armor steel with the superior strength-to-weight ratio can extremely improve the ballistic resistance and mobility of military equipment and structures. Aiming to assess the ballistic resistance including the ballistic limit and failure modes of two types of advanced high-strength armor steels, the projectile perforation test and numerical simulations were conducted. Firstly, ten shots of 15 mm-caliber ogive-nosed projectile perforation test were performed under the initial impact velocities of 164–428 m/s. The failure mode and out-of-plane displacement (OPD) response of target plate were recorded by utilizing the high-speed 3D digital image correlation system. Then, the classical finite element (FE) and mesh-free Smoothed Particle Galerkin (SPG) methods were adopted to conduct the numerical simulations, respectively. The predicted residual velocities of projectile were compared with the test data to verify the accuracy of the calibrated constitutive model parameters and numerical analysis approaches. By further comparing the failure modes and OPD–time histories of target, it was drawn that the FE method is preferable to reproduce the failure mode of target, while the SPG method is recommended to quickly predict the residual velocity of projectile. Finally, by adopting the validated numerical analysis approach, the residual velocities for two types of high-strength armor steels under the initial impact velocity range of 150–600 m/s were obtained. The reliabilities of the existing seven analytical models in predicting the ballistic limit and residual velocity for high-strength armor steels were further evaluated.

Experimental study of the influence of thickness and ply sequence on woven composite plates subjected to out of plane impact

In this work the different failure mechanisms have been studied on 5HS woven composite laminates subjected to low velocity impacts. A large range of energies (5-75J) has been used to induce different failures: delamination, fiber failure, out-plane shear and perforation. In addition, different configurations of AGP 280-5HS woven coupons have been manufactured to analyze the influence of thickness ((0/90)4S, (0/90)6S and (0/90)8S) and ply sequence ((0/90)8S, (±45)8S, [(±45)/(0/90)]4S, [(±45)2/(0/90)2]2S, and [(±45)4/(0/90)4]S)). Laminates have been subjected to low velocity impact using an INSTRON-CEAST Fractovis 6875 drop weight tower according to ASTM standards (D7136). Each test has been recorded with two high speed video-cameras (Photron SA-Z 2100K) in order to analyze the plate behavior during the impact. In addition, a three dimensional high velocity digital image correlation (HV-DIC) analysis has been performed to measure the out of plane displacement. Once impacted, the damaged area of the composite laminates was evaluated by ultrasonic inspections. The analysis of the influence of the plate thickness and ply sequence have been made according to the Composite Structure Impact Performance Assessment Program (CSIPAP) proposed by Feraboli and Kedward using the peak force and the absorbed energy.

Vol4 num4-12 Compression after impact test on woven CFRP laminates: the effect of ply clustering

One of the mayor threats for FRP is the out-of-plane loading conditions such as impacts, which produce interlaminar failures, among others, decreasing drastically the material's strengths in plane. Drop weight and compression after impacts tests have been selected as the standard methodology to evaluate laminate performance under impact loadings. The present work aims to reveal the influence of the material structure in woven laminate response under impact. To this end a complete set of experiments was designed using the actual ASTM standards (D7136/D7137), including the actual monitoring capabilities to address this problem. Composite coupons, made of AGP 280-5H carbon/Epoxy satin, were manufactured using three laminate configurations to analyze the effect of ply clustering [(+-45)/(0/90)]4S, [(+-45)2/(0/90)2]2S, and [(+-45)4/(0/90)4]S). Laminates have been subjected to low velocity impact using an INSTRON-CEAST Fractovis 6875 drop weight tower while compression test has been performed using a INSTRON 250 kN. Impact tests have been recorded with two high speed video-cameras (Photron SA-Z 2100K) configured at 20000 fps in order to analyze the plate behavior during the impact. In addition, a three dimensional high velocity digital image correlation (3D-HV-DIC) analysis has been done with the VIC-3D 7 system to measure the out of plane displacement and strains evolution. Also 3D-DIC analysis has been carried out for the CAI test to check the validity of the failure modes. It has been observed that the most clustered laminates increase the perforation threshold, while it decrease the residual strength of the material, due to damage spreading effect.

Analytical Study of Bending Characteristics of an Elastic Rectangular Plate using Direct Variational Energy Approach with Trigonometric Function

In this paper, an analytical three-dimensional (3D) bending characteristic of an isotropic rectangular thick plate with all edges simply supported (SSSS) and carrying uniformly distributed transverse load using the energy technique is presented. The three-dimensional constitutive relations which involves six stress components were used in the established, refined shear deformation theory to obtain a total potential energy functional. This theory obviates application of the shear correction factors for the solution to the problem. The governing equation of a thick plate was obtained by minimizing the total potential energy functional with respect to the out of plane displacement. The deflection functions which are in form of trigonometric were obtained as the solution of the governing equation. These deflection functions which are the product of the coefficient of deflection and shape function of the plate were substituted back into the energy functional, thereafter a realistic formula for calculating the deflection and stresses were obtained through minimizations with respect to the rotations and deflection coefficients. The values of the deflections and stresses obtained herein were tabulated and compared with those of previous 3D plate theory, refined plate theories and, classical plate theory (CPT) accordingly. It was observed that the result obtained herein varied more with those of CPT and RPT by 25.39% and 21.09% for all span-to-thickness ratios respectively. Meanwhile, the recorded percentage differences are as close as 7.17% for all span-to-thickness ratios, when compared with three dimensional plate analysis. This showed that exact 3D plate theory is more reliable than the shear deformation theory which are quite coarse for thick plate analysis. Doi: 10.28991/esj-2021-01320 Full Text: PDF

A detailed solution framework for the out‐of‐plane displacement of circular dielectric elastomer actuators

AbstractThe out‐of‐plane displacement (OPD) of a circular dielectric elastomer actuator (DEA) membrane has been explored in recent years for a variety of important applications. Circular DEAs consist of an elastomer membrane that is prestretched to a rigid frame and coated with compliant electrodes. Such a simple configuration has found many interesting applications such as in pumps, pulse tracking, hopping search and rescue robots, dielectric elastomer generators for renewable energy harvesting, linear actuators, and many others. Here, we present an easy‐to‐implement solution framework of the OPD for circular DEAs via a detailed numerical solution using the shooting method (SM) on a system of differential algebraic equations (DAE). The material model incorporated follows the robust Gent hyperelastic representation, and a comparison (of the OPD of a single‐cone DEA) against a neo‐Hookean based solution is included. The SM‐based numerical solution to the resulting boundary value DAE problem is applied to a practical range of values based on the reported literature. Analysis of the results and comparison against other studies are provided. The current work provides a go‐to framework for implementation in further research and development that can be useful to a broader audience including nonexperts in the field of soft robotics.

Parametric study of thermally induced warpage of FpBGA package using finite element methods

Warpage is considered to be the major concern in ensuring the reliability and manufacturability of electronic package because a flat package is crucial for a successful formation of board level assembly process. Warpage is the out of plane displacement which is a resultant of difference in co-efficient of thermal expansion (CTE) between the adjoining packaging materials. Enormous warpage may lead to occurrence of faulty joints such as open connections, mis-shaped joints, and loss of package board-level reliability under manufacturing, thermal loading process, shock and vibration. In this paper, a Fine pitch ball grid array Package (FpBGA) which is a prominent type of electronic package offering solution for downsizing of electronic components such as mobiles and camcorders has been choose for study. Warpage of FpBGA was simulated from post cure temperature to reflow temperature using Finite Element Methods. A static thermal analysis was carried out using ABAQUS software and a parametric study was done to investigate the effect of material properties and geometric properties in minimizing the warpage. Materials properties such as CTE, Elastic modulus of substrate and die, geometric properties like thickness of die and substrate were chosen for study.

Conventional surface micromachining process for the fabrication of a linear optical phased array based on piston micromirrors

Micro electromechanical system (MEMS) based optical phased array (OPA) technology generally demands narrow and tightly spaced suspended microstructures with high-aspect-ratio in the lateral dimensions. This paper presents an one dimensional OPA system which is fabricated using the standard PolyMUMPs process, leading to a low-cost, simplified and commercially accessible surface micromachining technique for the OPA technology. The proposed OPA device utilizes an array of metal-coated silicon micromirrors with high-aspect-ratio structures which act as optical phase shifters. Each micromirror along the array is individually actuated by an electrostatic parallel plate micro-actuator made of a micro-cantilever beam positioned above a fixed electrode. The field of view obtained by the device is measured as 4.76° which is comparable to those by the previous MEMS based OPA devices fabricated using custom-run and complex surface micromachining processes. The OPA device has a response time of 6.5 µs and an out of plane actuation stroke of 0.16 µm at a bias voltage of 55 V. The magnitude of the out of plane displacement by the phase shifters is equal to one-quarter of the laser wavelength (650 nm) used which leads to the desired optical phase shift of radian.

Stability of full-scale orthotropic steel plates under axial and biased loading: Experimental and numerical studies

In this study, three full-scale orthotropic steel plates set with single U rib, double U ribs and three U ribs were fabricated based on the mechanical characteristics of Changhong bridge in Ningbo. Several displacement and strain measuring points were selected as the analysis indexes, and two loading modes of axial and biased loading were designed. The buckling shape, out of plane displacement and strain variation law of the components under different loading conditions were analyzed. The DIC method was used to analyze the buckling and force transfer mechanism of the component in the loading process. Moreover, the finite element simulation and parameter analysis were carried out under eight component parameters by using ANSYS software. Through the experimental and parameter analysis in this paper, the instability mode, change of out of plane displacement, strain distribution and force transfer mechanism of orthotropic steel plates under different loading modes were obtained, which can provide reference value for the stability study of orthotropic steel plate and orthotropic steel box girder.

Electrothermal micro tweezer for biomedical applications

This paper presents design, simulation and results analysis for a novel micro tweezer. The principal element in the proposed device is a double U-beam electrothermal actuator. Using FEM tool, Poly-Silicon material is applied to the device structure and analysed for both in-plane and out of plane displacement for respective range of actuation potential. The micro tweezer holder mouth provided a maximum in-plane displacement of ∼48µm at 4.5V actuation voltage. Comparatively negligible out of plane displacement exhibited by the device during simulation. The proposed micro tweezer is designed for the micromanipulation of biological cells in a better way.

Design of a resonant Luneburg lens for surface acoustic waves

In this work we employ additive manufacturing to print a circular array of micropillars on an aluminium slab turning its top surface into a graded index metasurface for surface acoustic waves (SAW). The graded metasurface reproduces a Luneburg lens capable of focusing plane SAWs to a point. The graded index profile is obtained by exploiting the dispersion properties of the metasurface arising from the well-known resonant coupling between the micropillars (0.5 mm diameter and variable length ∼3 mm) and the surface waves propagating in the substrate. From the analytical formulation of the metasurface’s dispersion curves, a slow phase velocity mode is shown to arise from the hybridisation of the surface wave with the pillar resonance. This is used to compute the radial height profile corresponding to the refractive index given by Luneburg’s equation. An initial validation of the lens design, achieved through ray theory, shows that ray trajectories have a strong frequency dependence, meaning that the lens will only work on a narrow band. An ultrasonic experiment at 500 kHz where plane SAWs are generated with a piezoelectric transducer and a laser scanner measures the out of plane displacement on the metasurface, validates the actual lens performance and the manufacturing technique. Finally, comparison between the ray analysis and experimental results offers insight into the behaviour of this type of metasurface especially in the proximity of the acoustic bandgaps and highlights the possibility for acoustic shielding.

Quantifying of secondary bending effect in multi-bolt single-lap carbon-epoxy composite joints via 3D-DIC

In this paper, an extensive experimental study was performed to quantify and understand secondary bending (SB) in multi-bolt single-lap joints composed of quasi-isotropic (QI) and cross-ply (CP) carbon/epoxy laminates for two laminate thicknesses. The out-of-plane displacement (OPD), which represents SB, was measured experimentally using a 3D digital image correlation (DIC) system. The SB ratio was quantified as the ratio of out-of-plane displacement (δOPD) to in-plane displacement (dt). It is found that δOPD/dt ratio measured in CP is approximately 30% higher than in QI. It has also been observed that for a given laminate configuration (CP & QI), the δOPD/dt ratio decreases as the tensile load increases. The analytical Neutral Line Model (NLM), which was used in this work, also predicts this trend. Moreover, 3D-DIC measurements show that although δOPD decreases with increasing modulus of elasticity, it increases with increasing thickness of the laminate.

Experimental investigations on flexural behaviour of delaminated carbon/epoxy composite using three dimensional digital image correlation

In semi automated manufacturing processes of multilayered carbon fiber reinforced composites, defects are induced. These defects cause reduction in service life of the products and lead to decrease in structural performance. In the present work, carbon fiber reinforced epoxy composite laminate with a stacking sequence of [0/0//45/−45/90/45/−45/90/90/−45/45/90/−45/45/0/0] was fabricated by hand lay-up method using vacuum bagging technique. An artificial defect to create pre-delamination was located in this composite between 0° and 45° plies at the centre of laminate. Experiments were conducted in four-point bending to determine the stiffness behavior of composite laminate and study other damage patterns occurred due to the existence of pre-delamination. The probable reasons for occurrence of other damage forms are explained in detail. Three-dimensional digital image correlation (DIC) technique was employed to determine displacements and strains of the specimen. The out of plane displacement due to local buckling against the bending load was also quantified.

An innovative infill wall utilizing light expanded clay aggregate: An experimental and numerical study

SummaryPast earthquakes had shown vulnerability of infill walls especially under out of plane (OOP) loading. Although some new infill walls show a good OOP performance, generally, they do not have the right economic justification or have complexity in construction. Therefore, in this paper, an innovative economical infill wall is presented that is not complicated in construction. The proposed wall constructed by light expanded clay aggregate in especial shape that reinforced with side plates, top, and bottom rebars. Experimental and numerical studies were carried out to investigate its seismic performance. Experimental results showed a high continuity between blocks of wall due to its especial shape that is increased ultimate OOP strength and ultimate OOP displacement of the wall. Numerical results indicated, because the infill wall is isolated from boundary frame, no drift is imposed to infill wall from boundary frame. Therefore, the infill wall only suffered OOP seismic acceleration. Due to light weight of the infill wall, low OOP load that corresponds to seismic acceleration is applied to the infill wall. In the infill wall, no separation is made even up to drift frame of 2.5%. The relations to design of the proposed infill wall were also presented.

Noncontact spatiotemporal strain mapping of composite multiferroic cylinders

Recently, the reinvigoration of research interest in in strain-mediated composite multiferroic structures resulted in translational magnetoelectric devices with superior performance than their traditional counterparts. Full-filed measurements and visualization of mechanical strain, with a focus at the interface, offer new possibilities for the advancement of magnetoelectric devices regardless of the material system. Here, we report spatiotemporal strain maps of composite magnetoelectric cylinders using a novel approach combining stable laser ultrasonic vibrometer and 2D motion system measurement technique. The physical measurement technique is augmented with a robust analysis algorithm that capable of effectively and consistently detect the interface. With the spatiotemporal maps, we forecast additional utility through the concurrent extraction of polarization and magnetization maps; hence highlighting the complex interactions between the involved order parameters. Understanding the converse magnetoelectric response in strain-mediated composite multiferroics is essential for the development of devices such and motors, antennas, and wireless power transferors. Given the dependence of the converse magnetoelectric response on the strain generation and transduction, mapping the mechanical response is essential for advancement of efficient devices. This mapping approach is challenging due to the dynamic nature of the response as well as the magneto-electro-mechanical coupling. Spatiotemporal maps of in-plane and out-of plane displacement and strain components were measured concurrently off the surface of a composite structure. To generate spatiotemporal strain maps, a laser-ultrasonic vibrometer mounted on a 2D gantry system was employed to map the in-plane and out-of-plane displacement components of a strain-mediated, concentric multiferroic composite cylinder. The strain maps provided insights on the behavior of the strain mediation mechanisms within the investigated composite structure including amplification of the strain due to the disparity in the mechanical properties of the constituents, which will result in a non-uniform distribution of magnetization and polarization responses. Additionally, the method to calculate the strain maps was shown to be robust for different spatial measurement resolutions.

Moment and Stress Analysis Solutions of Clamped Rectangular Thick Plate

The bending solutions of rectangular thick plate with all four edges clamped (CCCC) were investigated in this study. The basic governing equations used for analysis are based on third-order shear deformation plate theory analysis under uniformly distributed load. Using a formulated total potential energy equation, the three coupled general governing differential equations for the determination of the out of plane displacement and shear deformations rotation along the direction of x and y coordinates were obtained. These equations as obtained are solved simultaneously after minimization to determine the coefficients of displacements of the plate and other the mentioned functions. By solving these equations, the analytic solutions of rectangular thick plate with all four edges clamped were derived. From the formulated expression, the formula for calculation of the maximum deflection, moment, stress and in-plane displacements were deduced. The proposed method obviates the need of shear correction factors, which is associated with Mindlin’s theory (FSDT) for the solution to the problem. Moreover, numerical comparison shows the correctness and accuracy of the results.

Moment and Stress Analysis Solutions of Clamped Rectangular Thick Plate

The bending solutions of rectangular thick plate with all four edges clamped (CCCC) were investigated in this study. The basic governing equations used for analysis are based on third-order shear deformation plate theory analysis under uniformly distributed load. Using a formulated total potential energy equation, the three coupled general governing differential equations for the determination of the out of plane displacement and shear deformations rotation along the direction of x and y coordinates were obtained. These equations as obtained are solved simultaneously after minimization to determine the coefficients of displacements of the plate and other the mentioned functions. By solving these equations, the analytic solutions of rectangular thick plate with all four edges clamped were derived. From the formulated expression, the formula for calculation of the maximum deflection, moment, stress and in-plane displacements were deduced. The proposed method obviates the need of shear correction factors, which is associated with Mindlin’s theory (FSDT) for the solution to the problem. Moreover, numerical comparison shows the correctness and accuracy of the results.

Hydrothermally degraded carbon fiber / epoxy plates subjected to underwater explosive loading in a fully submerged environment

An experimental and computational investigation was conducted to evaluate the underwater blast response of fully submerged carbon fiber composite plates after prolonged exposure to saline water. The material was a biaxial carbon fiber/epoxy composite with a [±45°] fiber orientation layup. The plates were placed in a saline water bath with a temperature of 65 °C for 35 and 70 days, which simulates approximately 10 and 20 years of operating conditions in accordance to Fick's law of diffusion coupled with Arrhenius's Equation and a reference ocean temperature of 17 °C. Underwater blast experiments were performed in a 2.1 m diameter pressure vessel. The composite plates were placed in the center of the vessel while fully submerged in water, and an RP-85 explosive was detonated at a standoff distance of 102 mm from the center of the plate. Two cases of fluid hydrostatic gage pressures were investigated: 0 MPa, and 3.45 MPa. Two high speed cameras were utilized for three-dimensional Digital Image Correlation, which provided full-field displacements and velocities of the composite plates during underwater blast loading. A third high speed camera captured the behavior of the explosive gas bubble. Moreover, the pressure fields generated by the explosive detonation and resulting gas bubble were recorded with tourmaline pressure transducers. A water diffusion study was completed which showed that the diffusion of water into the composites reached a point of complete saturation after 35 days of exposure. Quasi-static material characterization tests were performed before and after prolonged exposure to saline water. The properties obtained from quasi-static testing also served as material inputs for the numerical models. The quasi-static test results showed that the tensile modulus E1,2 does not change with exposure to saline water, whereas the in-plane shear modulus G12 decreases with saline water exposure. During blast loading, for the case of 0 MPa hydrostatic gage pressure, the gas bubble interacts with the composite plate substantially. In such an event, the out of plane displacement increased for saline water exposed plates when compared to virgin structures. For the case of 3.45 MPa hydrostatic gage pressure, the gas bubble does not visibly interact with the composite plate. In this case, the out of plane displacement for specimens exposed to saline water was similar to the virgin specimen. A fully coupled Eulerian–Lagrangian fluid structure interaction simulation was performed by using the DYSMAS code. The numerical simulations showed that the displacement of fully submerged composite plates is driven by the displacement of fluid, as well as the size of the gas bubble formed by the explosive rather than the peak pressure generated by the explosive. The numerical simulations were in agreement with the experimental findings in terms of pressure history and plate deformation.

Mitigation of shock loading on structures using aqueous methylcellulose solution

Shock mitigation performance of aqueous methylcellulose hydrogel and water for structural applications was investigated through two dynamic loading instruments: Instrumented bar and shock tube. While aqueous methylcellulose solutions have previously been found to attenuate impact-induced forces passing through them by a unique liquid-to-solid phase transition, this is the first time studied as shock mitigators to structural elements. The results obtained with aqueous methylcellulose as mitigator were compared with an equivalent experiment conducted with water as damping medium. The liquid was loaded into a specially designed hollow aluminum box, built to allow transmission of dynamic stress waves to a thin back plate. Determination of the liquid's attenuation performance was based on the 3D Digital Image Correlation technique with high-speed photography to obtain the full-field real-time deformation data of the back-face plate throughout the dynamic loading event. It was found that upon high rate loading with the instrumented bar, the aqueous methylcellulose solution decreases the maximum out of plane displacement resulting from the dynamic loading by as much as 40% compared to water, and significantly damps the structural vibrations of the back-face plate. On the other hand, upon relatively low rate loading with shock tubes, water and aqueous methylcellulose solutions provide the same magnitude of out of plane displacement, however, the damping ratio (Logarithmic Decrement) of the structure through aqueous methylcellulose solutions is 45% greater than through water. The findings are analyzed and rationalized in terms of imparted mechanical power.

Bilinear Load–Displacement Curve of Semi-supported Steel Shear Walls

Elastic stiffness and ultimate shear capacity are two main parameters of a structural system to obtain its ideal bilinear load–displacement. In the previous studies, the ultimate shear capacity of semi-supported steel shear walls (SSSW) which are a new lateral resisting system, has been determined. In this system, wall plates do not have any direct connection to the main columns of structure and they are connected to secondary columns which do not carry the gravity loads. The used thin plate in the SSSW elastically buckles at low levels of lateral loads and the wall plate stays on a fairly vast region with elastic post-buckling behavior (elastic stiffness). In this study, the Von-Karman plate equations are solved by the Galerkin method to find displacement field of the wall plate in the elastic post-buckling region as well as the maximum shear load after which the plasticity expand in the wall plate. Thus, the elastic stiffness of system is calculated. As the analytical procedure is complicated, the method is applied on 144 examples with different material and geometrical properties. Using linear regression technique, a concise formula is proposed to predict the elastic stiffness of system. The dimensions of wall plate are only the effective parameters in the suggested formula and the elastic stiffness is independent of the overturning moment, section of secondary columns and yield stress of material. Using the ultimate shear capacity and elastic stiffness, an ideal bilinear curve is obtained for the lateral load versus the horizontal displacement. The shear capacity at the end of elastic post-buckling region and out of plane displacement are acceptably validated with those of FE analysis for some examples.