Self-sensing time-domain reflectometry for detection of the bearing failure of a CFRP laminate fastener hole: effect of peeling of the insulator

Carbon-fiber-reinforced polymer (CFRP) composites are used in aerospace and automobile structures. For many CFRP structures, mechanical metallic fasteners are adopted. In internal structures such as a wing box, damage to CFRP structures around the fastener holes is difficult to see. A simple method of finding damage around fastener holes is thus required for CFRP structures. This study applies self-sensing time-domain reflectometry to detect bearing failure around fastener holes of CFRP structures. In a previous paper, the effect of fasteners was minimized when the micro-strip line (MSL) was placed apart from the fasteners. This study numerically and experimentally investigates the peeling of glass-fiber-reinforced polymer (GFRP) insulator. A bearing failure results in embossing at the edge of a fastener hole. The embossing produces a wedge that causes the peeling of GFRP, generating a gap between the GFRP and CFRP. The gap strongly affects the characteristic impedance of the MSL.     

Analytical solutions to eddy current in carbon fiber-reinforced composites induced by line current

This paper presents analytical solutions to eddy current distribution in carbon fiber-reinforced plastics induced by line current. Derived solutions show that eddy current distribution in unidirectional carbon fiber composite is dependent only on electrical conductivity in the drive current direction when the drive current is directed in the fiber direction or the transverse direction. Moreover, according to the derived analytical solution, skin depth of eddy current depends not only on frequency of drive current but on lift-off and width of the drive current unlike general expression of skin depth. Finally, we discuss improvement of sensitivity of eddy current conductivity sensor using analytical solutions. It is found that analytical solutions can clearly divide effects of magnetic field from drive current and that from eddy current. Sensitivity of eddy current sensor can be improved by 10 times placing pickup coil at region where the effect of magnetic field from eddy current is large.     

A humidity sensor using burned zircon with phosphoric acid: effect of strongly acidic protons on humidity sensitivity

Impedance and water sorption measurements have been made of burned zircon with phosphoric acid. In a humid atmosphere, the resistance which is approximated by the impedance is inversely proportional to the concentration of the strongly acidic PO-H group which results in an increase in the sorbed water. The addition of the strongly acidic PO-H formed on the particle surfaces leads to decreases in the resistance and its activation energy. For the element burned at 350° C in which the H₃PO₄/ZrSiO₄ mole ratio is 0.2 or more, the resistance is 10⁶Ω or below in a dry atmosphere and decreases with an increase in humidity. The humidity dependence of the resistance can be controlled not only by the form of the porous insulating ceramic but also by the addition of the strongly acidic protons. The response times of the resistance for the surface-type element to the humidity changes are 3 min or below for both adsorption and desorption processes.     

Stability of jets in liquid-liquid systems

Experiments were carried out to study the stability of jets in immiscible liquid systems under conditions where the jet velocity relative to continuous phase was zero. The laminar breakup lengths and the diameter of drops formed from laminar jets are in good agreement with the stability analysis for stationary column while breakup data for jets injected into quiescent liquids disagree with it. An approximate solution for theoretical drop size is presented. The experiment also showed that the hydrodynamic resistance of continuous phase increases the growth rate of disturbances but does not affect the wave length.     

Reaction of poly(vinyl chloride) with ethylenediamine hydrotrisulphide and properties of the products

The chemical structure and the properties of the products of the reaction of poly(vinyl chloride) (PVC) with ethylenediamine hydrotrisulphide were investigated. PVC derivatives containing a polysulphide crosslinkage and a hydropolysulphide pendant (PSC-PVC) were obtained by the reaction of PVC with ethylenediamine hydrotrisulphide in ethylenediamine (EN) as well as in EN-diglyme, and EN-benzene at 20–50°C for 0.5–5h. The chemical structure of PSC-PVC was determined from crosslinking density before and after iodine oxidation and elemental analysis. Scission of polysulphide crosslinkage in PSC-PVC by some thiols was carried out in tetrahydrofuran-triethylamine solution at 30°C for 1–4h as well as in a hot roller mill at 125–180°C for 2–8 min. The former product was photocrosslinked under ultra-violet irradiation in air and the latter showed the properties of a plastic, a leather, and a rubber with increasing weight of dioctyl phthalate.     

Multiscale seamless‐domain method for solving nonlinear problems using statistical estimation methodology

This article presents a nonlinear solver combining regression analysis and a multiscale simulation scheme. First, the proposed method repeats microscopic analysis of a local simulation domain, which is extracted from the entire global domain, to statistically estimate the relation(s) between the value of a dependent variable at a point and values at surrounding points. The relation is called regression function. Subsequent global analysis reveals the behavior of the global domain with only coarse‐grained points using the regression function quickly at low computational cost, which can be accomplished using a multiscale numerical solver, called the seamless‐domain method. The objective of the study is to solve a nonlinear problem accurately and at low cost by combining the 2 techniques. We present an example problem of a nonlinear steady‐state heat conduction analysis of a heterogeneous material. The proposed model using fewer than 1000 points generates a solution with precision similar to that of a standard finite‐element solution using hundreds of thousands of nodes. To investigate the relationship between the accuracy and computational time, we apply the seamless‐domain method under varying conditions such as the number of iterations of the prior analysis for statistical data learning.     

Remote Control for Robotic Systems Using CORBA as Communication Architecture

This paper proposes a novel method to implement network connections among a client and remoterobotic systems using CORBA for developing telecare system to aid the aged or disabled. The proposed methodmakes system have low cost and wide availability, high scaling and inter-operating ability to allow the clients andserver objects, written in different languages, run in different operating system, and connected in different net-work to inter-operate. It also makes system easy to be extended and integrated with the other technologies andapplications distributed over the Internet. Using CORBA as a communication architecture, we developed hard-ware base, task-level robot arm control server, live image feedback server and mobile robot control server,which can provide some basic care services to aid the aged and disabled.     

Effects of applied stress on cavitation erosion

Cavitation erosion under static applied stress and/or alternating stress was studied using steel specimens which were set in close proximity to an oscillating horn in ion-exchanged water. For increasing static applied tensile or compressive stress, weight loss and its rate do not vary in a monotonic fashion but first decrease, then increase through a peak, and then decrease again. Tensile stress except for given stress regimes, and compressive stress at all stress levels, decreases erosion damage compared with zero-stress values. Under alternating stress, the weight loss rate varies with trends similar to those under static applied stress. However, the weight loss rate is larger than for the same static stress, so that the erosion damage is more affected by alternating stress than by static stress. The behaviors under applied stress are discussed through the effect of stress on the erosion particles.