Pin Matrix Research Articles

Pseudo-ductile behaviour of fibrous composite Z-pins

This paper describes the development and characterisation of a novel type of composite Z-pin able to accommodate large deformation without exhibiting fibre failure. Three types of pseudo-ductile Z-pins are fabricated by means of micro-pultrusion of polybenzoxazole (PBO) fibres. Namely, unidirectional PBO fibre (uPBO) Z-pins in combination with a ductile (uPBO/DCT) and a brittle (uPBO/BT) matrix system are developed, together with a twisted PBO fibre Z-pin in combination with a ductile matrix (tPBO/DCT). Single pin bridging tests are carried out across the full mode mixity range from mode I (Φ = 0) to mode II (Φ = 1). The tests reveal that uPBO-based pins are able to pull out throughout the full mode mixity range, regardless of the ductility of the pin matrix. uPBO/DCT pins exhibit a 20-fold increase in energy dissipation per pin than traditional carbon fibre/bismaleimide (CF/BMI) pins at load mode mixities higher than Φ = 0.9. The mode I behaviour of all pins considered is comparable. All PBO pins exhibit an apparent delamination toughness enhancement superior to CF/BMI at mode mixities above Φ = 0.2, with a ductile matrix increasing the average energy dissipated per pin by a further 2–8 %.

Component specific elastic cushion design to enhance the accuracy with the usage of reconfigurable tools in stretch forming

Multi-point stretch forming (MPSF) is a flexible manufacturing technology that uses reconfigurable tools to produce a variety of three-dimensional sheet metal components. An elastic cushion is placed between the surfaces of reconfigurable tool and the sheet metal to reduce the possibility of dimple formation. It is well known that elastic cushion deformation behavior significantly affects the accuracy and surface quality of components. In the present work, a component-specific elastic cushion is designed to achieve better conformability between the pin heads and cushion (by scooping out the material from the flat cushion selectively). An analytical model is developed to determine the volume of material to be scooped out and its location based on pin head and component geometries. To demonstrate the effectiveness of the developed methodology, finite element analysis (FEA) is performed to form double curvature (spherical) component with a cushion of constant thickness and a component-specific cushion with different pin matrix sizes. Results indicate that the deformation is more uniform with significant improvement in shape accuracy of the component formed with a component-specific cushion.

Multipoint Forming Using Hole-Type Rubber Punch

Reconfigurable multipoint forming is a flexible sheet forming technique aimed at customised sheet metal products. However, one drawback of multipoint forming is the cost and time needed to set up and align the upper and lower pin matrices. This study introduces an optimisation study of a novel hole-type rubber punch replacing the top pin matrix of multipoint incremental forming, aiming to reduce pins setting up and alignment complexity and time. Finite element modelling and design of experiments were used to investigate the effect of hole-type rubber punch configuration such as hole size, hole type, and the compression ratio on the wrinkling, thickness variation, and shape deviation. This research shows that the most significant process parameter in all responses was the hole size. The compression ratio of the material was found to be insignificant in wrinkling and shape deviation. The hole-type rubber punch parameters were found to be a hole size of 9 mm, circular hole type, and a compression ratio of 75%. This experimentally resulted in an improved parts wrinkling of 80%, when compared to using solid rubber punch, with the added benefits of reduction of the cost and time needed to set up and align the pin matrices.

Temporal coherency of mechanical stimuli modulates tactile form perception

The human hand can detect both form and texture information of a contact surface. The detection of skin displacement (sustained stimulus) and changes in skin displacement (transient stimulus) are thought to be mediated in different tactile channels; however, tactile form perception may use both types of information. Here, we studied whether both the temporal frequency and the temporal coherency information of tactile stimuli encoded in sensory neurons could be used to recognize the form of contact surfaces. We used the fishbone tactile illusion (FTI), a known tactile phenomenon, as a probe for tactile form perception in humans. This illusion typically occurs with a surface geometry that has a smooth bar and coarse textures in its adjacent areas. When stroking the central bar back and forth with a fingertip, a human observer perceives a hollow surface geometry even though the bar is physically flat. We used a passive high-density pin matrix to extract only the vertical information of the contact surface, suppressing tangential displacement from surface rubbing. Participants in the psychological experiment reported indented surface geometry by tracing over the FTI textures with pin matrices of the different spatial densities (1.0 and 2.0 mm pin intervals). Human participants reported that the relative magnitude of perceived surface indentation steeply decreased when pins in the adjacent areas vibrated in synchrony. To address possible mechanisms for tactile form perception in the FTI, we developed a computational model of sensory neurons to estimate temporal patterns of action potentials from tactile receptive fields. Our computational data suggest that (1) the temporal asynchrony of sensory neuron responses is correlated with the relative magnitude of perceived surface indentation and (2) the spatiotemporal change of displacements in tactile stimuli are correlated with the asynchrony of simulated sensory neuron responses for the fishbone surface patterns. Based on these results, we propose that both the frequency and the asynchrony of temporal activity in sensory neurons could produce tactile form perception.

Structural characterization and dielectric parameters of polyindole/WO3 nanocomposites

AbstractIn the present study, polyindole/tungsten trioxide (PIn/WO3) nanocomposites have been prepared and characterized in the context of their structural properties as well as frequency‐dependent (ac) electrical features for the first time. While PIn polymer has been synthesized by chemical oxidative polymerization, WO3 nanorods have been obtained by using the hydrothermal method. Several studies, that is, transmission electron microscopy, Fourier transform infrared, energy dispersive X‐ray, X‐ray diffraction analysis, scanning electron microscopy, dielectric properties on these PIn/WO3 nanocomposites have been carried out. These investigations showed the average particle size of WO3 between 15.36 and 44.71 nm. The pure PIn and WO3 were compatible with the surface morphology of the PIn and WO3 reported in the scientific literature. The dielectric analyses have been carried out in the context of both the real and imaginary components of complex permittivity and electrical modulus. The ε′ values of all PIn/WO3 composites have been observed lower than that of pure Pln and ε′ decreased with the increasing amount of WO3 in the PIn matrix for the low‐frequency range. Electric modulus analysis showed that the increase in M′ value with frequency implies a tendency to reach a value which can be interpreted as short‐range mobile charge carriers perform the electrical conductivity.

Very Large Eddy Simulation of turbulent flow and heat transfer for single cylinder and cylindrical pin matrix

The study of turbulent flow and heat transfer around a cylinder and cylindrical pin matrix is important for turbine blade cooling. A newly developed VLES method is applied to investigate the unsteady flow and heat transfer mechanisms. DDES and unsteady RANS methods are also used in the simulations for comparisons. Two typical cases are selected, i.e. the flow around a single cylinder, and cylindrical pin matrix of wall-bounded 8 × 8 round pins, with Re = 10000. The results show that the VLES predictions agree well with the experiments for both the flow velocities and heat transfer Nusselt numbers for the two cases, which are even better than the DDES and RANS results. The VLES method gives satisfactory predictions of mean endwall Nusselt number of the complex pin matrix, which is within 15% difference from the experiments. The unsteady three-dimensional vortex characteristics play an important role for the heat transfer, especially in the pin matrix due to complex pin disturbance and wall confinement. Accurate representation of the vortex structures is the key for good heat transfer prediction. The results demonstrate the reliability and accuracy of the present VLES method for complex turbulent convection heat transfer of industrial relevance.

Development of polyindole/tungsten carbide nanocomposite-modified electrodes for electrochemical quantification of chlorpyrifos

The present investigation deals with the development of a novel polymer nanocomposite (PNCs) electrodes for simple, selective and sensitive detection of chlorpyrifos (CHL). PNCs were developed using surfactant facilitated polymerization of indole using different concentrations (wt%) of WC ranging 5–30. Formation of PNCs was ascertained through diversified analytical methods. Electrodes were derived from PNCs over stainless steel substrate for electrochemical quantification of CHL. With concentration of WC, the DC conductivity (10−2 × S/cm) of electrodes was increased ranging 3.54–0.75 at 313 K. Electrochemical impedance spectroscopy reveals well stability of electrodes in phosphate buffer (PBS, 0.1 M) at pH 7.4. The performance of electrodes towards detection and quantification of CHL was investigated through square wave voltammetry. Study reveals that detection and quantification of CHL were dependent on concentration of WC in nanocomposites. Square wave voltammetry reveals that the electrode derived from PNCs with 5 wt% of WC has rendered highest limits of detection and quantification of CHL (10−8 mol/L) up to 5.94 and 18. This work describes a viable method of preparation of synergistic blend of WC in PIN matrix having high electrical conductivity, rapid electron shift, huge surface area and enhanced stability for fast and précised electrochemical detection of CHL.Graphic abstract

Numerical Simulations of Flow and Heat Transfer in a Wall-Bounded Pin Matrix

A detailed computational study was performed for the case of a wall-bounded pin-fin-array in a staggered arrangement, representative of industrial configurations designed to enhance heat transfer. In order to evaluate the level of turbulence modelling necessary to accurately reproduce the flow physics at three (3) different Reynolds numbers (3,000, 10,000 and 30,000), four models were selected: two eddy-viscosity URANS models (k-ω-SST and ϕ-model), an Elliptic Blending Reynolds-stress model (EB-RSM) and Large Eddy Simulation (LES). Global comparisons for the pressure loss coefficients and average Nusselt numbers were performed with available experimental data which are relevant for industrial applications. Further detailed comparisons of the velocity fields, turbulence quantities and local Nusselt numbers revealed that the correct prediction of the characteristics of the flow is closely related to the ability of the turbulence model to reproduce the large-scale unsteadiness in the wake of the pins, which is at the origin of the intense mixing of momentum and heat. Eddy-viscosity-based turbulence models have difficulties to develop such an unsteadiness, in particular around the first few rows of pins, which leads to a severe underestimation of the Nusselt number. In contrast, LES and EB-RSM are able to predict the unsteady motion of the flow and heat transfer in a satisfactory manner.

Homogenous Dispersion of MoS2 Nanosheets in Polyindole Matrix at Air-Water Interface Assisted by Langmuir Technique.

Two-dimensional (2D) inorganic layered materials when embedded in organic polymer matrix exhibit exotic properties that are grabbing contemporary attention for various applications. Here, nanosheet morphology of molybdenum disufide (MoS2) synthesized via one-pot facile hydrothermal reaction are exfoliated in benign aqueous medium in the presence of indole to obtain a stable dispersion. These exfoliated nanosheets then act as host to template the controlled polymerization of indole. The preassembled MoS2-polyindole (MoS2-PIn) nanostructures are reorganized at the air-water interface using the Langmuir method to facilitate maximum interfacial interaction between nanosheet and polymer. This report emphasizes large area, homogeneous dispersion of uniform-sized MoS2 nanosheets (40-60 nm diameter) in the PIn matrix and the formation of stable and uniform film via the Langmuir-Schaefer (LS) method. These self-assembled, MoS2 decorated PIn LS films are characterized using atomic force microscopy (AFM) and transmission electron microscopy (TEM). The fabricated LS films in sandwiched structure Al/MoS2-PIn/ITO as the Schottky diode portrayed remarkable enhancements in charge transport properties. Our study illustrates the potential of the MoS2-PIn LS film in electronic applications and opens a new dimension for uniform dispersion of 2D materials in other polymers via the Langmuir method for device fabrication and enhancement of electrical properties.

Improved electrochemical performance of polyindole/carbon nanotubes composite as electrode material for supercapacitors

Polyindole/carbon nanotubes (PIN/CNTs) composite was prepared by an in-situ chemical oxidative polymerization of indole monomer with CNTs using ammonium persulfate as oxidant. The obtained composite material was characterized by SEM, TEM, FT-IR, Raman spectroscopy, XPS, XRD and BET surface areas measurements. It was found that the CNTs were incorporated into the PIN matrix and nanoporous structure was formed. Spectroscopy results showed that interfacial interaction bonds might be formed between the polyindole chains and CNTs during the in-situ polymerization. PIN/CNTs composite was evaluated by electrochemical impedance spectroscopy, cyclic voltammetry and charge/discharge tests to determine electrode performances in relation to supercapacitors properties in both aqueous and non-aqueous system. A maximum specific capacitance and specific volumetric capacitance of 555.6 F/g and 222.2 F/cm3 can be achieved at 0.5 A/g in non-aqueous system. It also displayed good rate performance and cycling stability. The specific capacitance retention is over 60% at 10 A/g and 91.3% after 5000 cycles at 2 A/g, respectively. These characteristics point to its promising applications in the electrode material for supercapacitors.

Large Eddy Simulations (LES) on the Flow and Heat Transfer in a Wall-Bounded Pin Matrix

In this article, the three-dimensional turbulent forced convection in a matrix of wall-bounded 8 × 8 cylindrical pins is studied. Large eddy simulations (LES) are performed for Reynolds numbers 3,000, 10,000 and 30,000. Three different subgrid-scale (SGS) models (WALE, QR, and VMS) are compared on a row-by-row study. Local values of velocity and pressure coefficient are depicted. Turbulence characteristics of the flow are well illustrated. The thermal field is analyzed and validated with the time-averaged Nusselt number at the end walls of the pin matrix. The capabilities of the methodology for predicting the turbulent flow features is also shown.

Research on Reconfigurable Pin Fixture Design: A Review

The manufacturing industry is moving toward rapid customization; this has an important effect on the nature of the fixtures that are used to clamp components. The research and application of reconfigurable pin fixture will become a necessity. Development of a reconfigurable pin fixture system is a complex procedure, as it involves many aspects of the system to be integrated: design, process planning, manufacturing, assembly etc. A thorough investigation of previous research into design of reconfigurable pin fixture is made in this paper. The review is comprised of five parts: pin cross-sectional shape, pin tips, pin density, pin actuation method and pin matrix clamping.

Investigation of VHI Affected by the Density of Mechanoreceptive units for Virtual Sensation

Abstract The velvet hand illusion (VHI) is an innovative tactile illusion that enables a human to perceive a velvety sensation by gently rubbing the hands on both sides of wire mesh string through a frame. In order to enhance tactile displays presentation ability, VHI’s mechanism is applied through a series of psychophysical experiments. In this paper, we have investigated the effects of several physical parameters on intensity variation of VHI in subjects’ fingers and fingertips, such as wire distance D and a dimensionless ratio of wire stroke r to wire distance r/D in passive touch based on psychophysical experiment. We obtain D = 45 mm and r/D ≈ 1 as optimum values for VHI intensity for wire distance and the ratio, respectively. Furthermore, as the result of comparison between the present result and the previous result for palm, we conclude that a combination of mechanoreceptive afferent units, SAI, SAII and FAI, are involved in VHI. VHI mechanism is induced when movement of wires is accepted through FAI under constant compressive stimulus for SAI and no shearing force for SAII. This result indicates that VHI can be generated by normal pin matrix type tactile displays because no stimulation of SAII is required.

移動する音源によるアルファベット形状の提示

Visually impaired persons typically visualize graphical information through the tactile sensation of a pin matrix display. Unfortunately, the panel of a pin matrix display has a small gross area, the size of a postcard, so it is hard for several people to touch the panel and share the same information concurrently. Moreover, while the display is suitable for presenting a static figure, it is difficult to visualize a moving image with one's fingers. To solve these problems, we focused on the resolution of time in the sense of hearing, and conducted research on using sound from speakers arranged in a matrix to present both static and moving figures that can be shared by several people simultaneously. This paper describes an experiment we conducted to determine whether people could recognize the stroke order of the uppercase alphabet. Sound was broadcast from the various matrix speakers as if it were moving. Participants had a high average for correctly recognizing the alphabetic characters, demonstrating that people are able to recognize graphical information transmitted as moving sound.

Electro-oxidation of formic acid using polyindole-SnO2 nanocomposite

We report a chemical oxidative method for polyindole-tinoxide (Pin–SnO2) synthesis and its electro-catalytic application. Our method consists of chemical polymerization of an indole monomer in the presence of dispersed nano SnO2 at two different pHs i.e. below and above the isoelectric point of the SnO2. Nano SnO2 with crystallite sizes of nearly 5.0 nm are prepared by precipitation technique. For the sake of comparison, pristine polyindole is also synthesized by the same chemical method. These materials are characterized by XRD, FTIR and TEM. Characterization confirms the presence of nano SnO2 particles in a Pin matrix and the effect of pH on the formation of a uniform nanocomposite and the extent of interaction of fillers and matrix. The electro-catalytic properties of the Pin–SnO2 nanocomposite are investigated for formic acid oxidation using the voltammetric technique. This shows excellent synergic effect for electro-catalytic activity of the low doped Pin–SnO2 nanocomposite (Pin–SnO2 nanocomposite formed at higher pH). This composite is well suited for CO tolerance during the oxidation of formic acid in acidic medium and follows a direct pathway to convert it into CO2.

A method for representation of component geometry using discrete pin for reconfigurable moulds

Moulding plays a paramount role in our daily life. Traditional moulding is often dedicated and expensive. As the current market trend moves from mass production towards small batch and large variation production, the demand for a mould that can reconfigure itself for different components is greater than ever. The reconfiguration of mould is often realized through discrete pins. Previous research in that field had focused on the hardware of pin actuation in order to move pins up or down to represent different components and lock the pins at certain positions. Little research has been conducted into support software development that enables rapid reconfiguration of discrete pins to represent component geometry. This paper addresses a new method of software development for the reconfigurable mould utilising discrete pins. The overall aim of the method is to provide an interface for generic discrete pin tooling in order to enable quick reconfiguration of the mould to represent component geometry. The software is composed of three parts: part discretization, pin matrix construction and adjustment and pin matrix verification.

Vortex structures and heat transfer in a wall-bounded pin matrix: LES with a RANS wall-treatment

A hybrid LES/RANS simulation is applied to study the velocity, vorticity and thermal fields in flow over a staggered matrix of cylindrical pins bounded by a cold and a heated plane endwall approximating the typical configuration of internal cooling of gas-turbine blades. The hybrid approach considered is in fact a coarse-grid conventional LES coupled with the elliptic relaxation ζ– f RANS model that prevails in the wall-adjacent regions. Two Reynolds numbers have been considered, 10.000 and 30.000, based on the pin diameter and mean velocity between the two pins. First the performance of the hybrid approach was evaluated in comparison with the earlier reported URANS using the same RANS model throughout the whole flow, as well as with wall-resolved LES. The results of the hybrid method, found to recover with acceptable accuracy the dominant large-scale vortical patterns and the averaged flow parameters, were then used to analyse the effects of vortex structures on the velocity and thermal fields and their role in wall heat transfer using graphical visualisation. In addition to the temperature contours, the thermal field is also visualized by heat-flux lines, which make it possible to identify heat “corridors” and distinguish regions dominated by stochastic turbulent transport and those of large-scale vortical convection.

VITAL: An electromagnetic integrated tactile display

VITAL is an acronym for VIbro-TActiLe display concepts and devices. The new tactile displays presented are based on an integrated electromagnetic actuator arranged in a (8 × 8) pin matrix. A multilayer approach with a simple assembly procedure enables the development of a new generation of competitively priced tactile matrices with potentially high micro-actuator density. The independent amplitude and frequency control of each pin facilitates displaying various haptic patterns; hence, the displays can be used as haptic communication media. VITAL aims to satisfy both market and haptic research requirements. This paper uses a haptic communication scenario to detail the research and technological development of the first prototype (VITAL1) and its validating experiment results. Extensions of the VITAL display technology through two additional variants and other applications’ perspectives are also discussed.

1A2-B10 高密度ピンマトリクスが有する触覚フィルタ機能の検討(触覚と力覚)

1A2-B10 高密度ピンマトリクスが有する触覚フィルタ機能の検討(触覚と力覚)

Effect of Tactile Display on Detection of Softness of Objects by Finger of Human.

Response pattern of tactile receptors caused by the deformation of finger tissue when human perpendicularly push objects are needed to be clarified in order to understand the mechanism of tactile perception of softness. In the present study, deformation of the finger tissues when a finger is in contact with an object directly, through pin matrix and/or rubber sheet is calculated using finite element (FE) analysis. Tendency of perception of softness when finger touches an object is also examined using a psychophysical test. Relationship between the deformation of finger tissues, elasticity of the object, and the perception of softness is clarified by comparing results of the FE analysis and the psychophysical test. It is also shown that the rubber sheet on the pin matrix is important to present softness of the object.