Effects of wrap thickness and ply configuration on composite-confined concrete cylinders

The behavior of small-scale fiber reinforced polymer (FRP) wrapped concrete cylinders under uniaxial compressive loading was investigated through nonlinear finite element analysis. Two parameters were considered for this numerical study: the FRP wrap thickness, and the ply configuration. Performances of numerical models with “hoop-angle-hoop” and “angle-hoop-angle” ply configurations were compared, where the terms “hoop” and “angle” indicate that wraps were oriented at an angle of 0° and 45° in reference to circumferential direction, respectively. The finite element analysis results showed substantial increase in the axial compressive strength and ductility of the FRP confined concrete cylinders as compared to the unconfined ones. The cylinders with “hoop-angle-hoop” ply configuration in general exhibited higher axial stress and strain capacities as compared to the cylinders with the “angle-hoop-angle” ply configuration. The increase in wrap thickness also resulted in enhancement of axial strength and ductility of the concrete cylinders.     

A dynamic measure of order in structural glasses

Although some patterns of physical behavior are common in the glass transition and in the properties of supercooled liquids and glasses (characteristic viscoelasticity, temperature dependence of viscosity and relaxation times, property evolution through “physical aging”, difficulties in performing equilibrium measurements or simulations, etc.), it is difficult to arrive at a definition of the glass transition which distinguishes it from other phenomena exhibiting similar features. The present paper addresses this problem by defining a dynamical measure of order involving the average “shape” of particle trajectories in supercooled liquids. This dynamic order parameter should provide a measure of “closeness” to the glass transition and some indirect insights into the physical nature of supercooled liquids and glasses. Arguments are given that the proposed dynamic measure of order [“generalized capacity”, C(T)] is related to the temperature-dependent “effective hydrodynamic radius” R_H(T) measured in supercooled liquids and model numerical calculations are given to support this view. Some consequences of the intermittent particle motion at low temperatures for stress relaxation are also discussed.     

Biomimetic ion-channel sensors based on host-guest molecular recognition in Langmuir-Blodgett membrane assemblies

Biomimetic “ion-channel sensors” based on host-guest molecular recognition were constructed by incorporating several kinds of receptor molecules in Langmuir-Blodgett (LB) molecular assemblies deposited directly on glassy carbon electrodes. The receptors used were valinomycin, bis(crown ether)s, macrocyclic polyamine and cyclodextrin polyamine. The binding of charged stimulants (metal ions, inorganic and organic anions) to these receptors induced a marked increase (or decrease) in the ion permeability of the membranes, as detected by cyclic voltammetry using [Fe(CN)₆]^4- or [Ru(bpy)₃]²⁺ as marker ion. Such a mode of response, corresponding to model “channel opening (or closing)”, can be explained on the basis of the charge-charge interaction involving the stimulant, marker ion and lipid.     

Long distance propagation of a polarized neutron beam in zero magnetic field

A beam of fully polarized cold neutrons was transported through a zero magnetic field region of 70 m length without loss of polarization. The purpose of this exercise was twofold: firstly, to demonstrate that the new zero-field neutron spin-echo method will work also for very long neutron flight paths; secondly, to prove in the most direct way that the neutron free-flight region of the ILL neutron-antineutron oscillation experiment was indeed sufficiently field-free (“quasifree condition”) by using the neutrons themselves as a magnetometer. To this purpose the residual magnetic field integrals in the long “zero-field” region were measured with a conventional neutron spin-echo method. The overall spin precession angle of the neutrons during their flight through the long zero-field region was found to be less than 2°.     

On new types of non-crystalline metallic composite

The structure and mechanical properties of new types of non-crystalline metallic composites, namely “glass-quasi-crystal”, “glass-disclinated nanocrystal” and “quasi-crystal(-glass)-disclinated nanocrystal” composites are theoretically examined. In particular, a theoretical model is proposed which effectively describes the relationship between plastic deformation and the growth of the glassy phase in metallic “glass-quasi-crystal” composite materials. Here also basic features of both the structure and the mechanical properties of the “glass-disclinated nanocrystal” and “quasi-crystal(-glass)-disclinated nanocrystal” composites are theoretically examined. It is shown that such composites are characterized by a very high yield stress.     

Range-to-cone-length relations for light ions in Cr

Curves of “range × cone length” and “diameter × cone length” are calculated for tracks left by low-energy light ions in ³⁹Cr. The calculations cover ions from helium to iron and are performed for 6.25N NaOH at 70°C and a standard etching time but can be easily extended to other etching conditions.     

Guides “bimorphes” d''ondes ultrasoniques “bimorph” ultrasonic wave guides”

An analysis of the dispersion of elastic waves is presented for two types of long ultrasonics wave-guides that we qualify of “bimorph”: (i) a “three-layer” guide made of two different materials and (ii) a “clad core” guide built up of a rectangular core surrounded by a cladding, the materials of the rod and cladding having different properties. An analytical model is proposed to describe the extensional, flexural and torsional motions in “bimorph” wave guides having two geometrical and material symmetry axes. The asymptotic behaviour of the model allows one to select the material properties which lead to modes guided essentially either in the central layer or in the core of the bimorph guide. Moreover, the dispersive properties of a “bimorph” can be controlled through the choice of geometrical and material parameters.     

Edge sensitivity of “edgeless” silicon pad detectors measured in a high-energy beam

We report measurements in a high-energy beam of the sensitivity of the edge region in “edgeless” planar silicon pad diode detectors. The edgeless side of these rectangular diodes is formed by a cut and break through the contact implants. A large surface current on such an edge prevents the normal reverse biasing of this device above the full depletion voltage, but we have shown that the current can be sufficiently reduced by the use of a suitable cutting method, followed by edge treatment, and by operating the detector at a low temperature. A pair of these edgeless silicon diode pad sensors was exposed to the X5 high-energy pion beam at CERN, to determine the edge sensitivity. The signal of the detector pair triggered a reference telescope made of silicon microstrip detector modules. The gap width between the edgeless sensors, determined using the tracks measured by the reference telescope, was then compared with the results of precision metrology. It was concluded that the depth of the dead layer at the diced edge is compatible with zero within the statistical precision of ±8 μm and systematic error of ±6 μm.     

FREE SETTLING OF A NON-SPHERICAL PARTICLE IN A STAGNANT LIQUID

The free settling behavior of the cylindrical particles made of four kinds of materials with horizontal motion in the stagnant water observed with an aid of the image sensor anemometer in the Reynolds number ranged from about 150 to 1000 was investigated in this paper. The four kinds of materials were finished into cylindrical specimens having the diameters “d” of 1.5 to 3.0 mm and the ratios of “d” to the length of specimen “1_s” of d/1_s = 1/2 to 1/3.5.

From the experimental results, the settling behavior of the particles was found to be simply expressed by the equation of a simple harmonic motion. By correcting the drag coefficient of the cylindrical particles with a correction factor which is obtained from the simple harmonic motion, the relationship between the drag coefficient and Reynolds number for the cylindrical particles was found to be parallel to that for the spherical particles.     

Factorial experimental design: Detecting an outlier with the dynamic variable and the Daniel''s diagram

This article describes how to be sure that there is, or not, an outlier in a two-level experimental design (16 runs or more) with no replicates. It also describes how to discover an outlier if there is one, and how to estimate the true value of this outlier. The method is based on the use of a dynamic variable and the “small effects” of the Daniel's diagram. The theoretical relationship between the “small effects” and the dynamic variable is established in the case of a two-level factorial design. The method is applied to two examples to show how the following three problems can be solved: whether there is, or not, an aberrant response, to detect an outlier when there is one and to estimate the value of the outlier as if it had not been aberrant.     

Acceleration discontinuities at an elastic/plastic loading interface

The conditions governing the motion of an elastic/plastic loading interface propagating into the elastic region with an associated acceleration (and strain-rate) discontinuity are set up. It is shown that for the general class of elastic/plastic solids considered, the speed of propagation of the interface must lie in one of three ranges, speeds in the fastest range being associated with the “creation” of a plastic regime. Detailed consideration is given to an interface with its normal along a principal axis of the tensor whose components define the normal to the yield surface in strain-space. The speed of the interface is determined for arbitrary acceleration and strain-rate discontinuities, and the effects of incident acceleration waves are discussed.     

Theoretical considerations on the penetration of powdered metal jets

This paper explores some of the theoretical issues encountered when interpreting the penetration behavior of an oilwell perforating charge, whose jet forms from an unsintered powdered metal (PM) liner. Appropriate treatments of the jet's porous compressible nature fill the gap between classical “continuous” and “fully particulated” jet penetration models. Within certain constraints, increasing a penetrator's length (even if by distension) increases its hydrodynamic penetration depth, while reducing its impact pressure; and a porous penetrator penetrates deeper than a non-porous penetrator of the same density, length, and velocity. Dynamic target pressure considerations lead to the conclusion that highly distended, low-velocity, PM jets should penetrate moderate-strength geologic targets effectively. After demonstrating that initial transient shock pressures may be much higher than steady-state penetration pressures, we suggest that initial penetration rates may be higher than the steady-state rates. This, in conjunction with the well-known “residual penetration” phenomenon, indicates that a non-continuous jet's penetration may be strongly influenced by transient effects.     

Fatigue life enhancement of aluminium joints through mechanical and thermal prestressing

This paper presents some simple and flexible methods to enhance the fatigue life of welded aluminium components. Besides enhancing the fatigue life, the proposed methods can easily be implemented into manufacturing processes. The key element of the methods is to change residual stresses from tension to compression at locations vulnerable to fatigue. This is accomplished by mechanical prestressing using elastic pre-deformation or by thermal prestressing using induction heating. The specimens tested are welded aluminium rectangular hollow section T-joints. Prior to fatigue testing, welding FE-simulations were carried out to verify the magnitude and pattern of the residual stress fields (through process modeling). Fatigue testing was later carried out on four different batches. One batch was produced using elastically pre-deformed chords, two batches were treated by means of thermal prestressing (induction heating), and one batch was “as welded” representing a “reference case”. Based on statistical evaluation of S–N data, the introduction of superimposed compressive stress fields results in a significantly improved fatigue life. Among the different batches, induction heating turned out to be the most promising method with a fatigue strength improvement factor of 1.5 on stress, compared to “as welded” components.     

Comparison of Methods for Evaluation of Flow Properties of Powders and Granulates

Powder mixtures and granulates with bulk densities ranging from 0.35-0.89 g.ml^-1 were tested regarding flow properties using the following methods: the Hausner ratio (packed bulk density/loose bulk density), rate of packing on tamping, flow rate through a 30 mm orifice, orifice diameter allowing free flow, and “drained” angle of repose.

The Hausner ratio and the angle of repose could be measured with a relative standard deviation of about 2 %. The orifice diameter could also be determined accurately and these three methods correlated well with each other.

The flow rate could only be measured on free flowing materials and the packing rate correlated poorly with the other methods.     

The Effect of the Coefficient of Variation of Operation Times on the Allocation of Storage Space in Production Line Systems

This paper studies the effect of the coefficient of variation of operation times on the optimal allocation of storage space in production line systems. The operation times at each station are modelled by a two-stage Coxian distribution. This work extends the results of our previous study of the storage allocation problem with exponentially distributed operation times. Interpreting Stage 1 of the two-stage Coxian distribution as the normal service for an item at a station and Stage 2 as down time at the station, our model can also be used to study the effect of breakdowns on the allocation of storage space in production line systems. The results show that the “bowl effect” whereby the center stations should be given preferential treatment becomes more pronounced with higher variability in the operation times. Another general conclusion is that the overall optimal storage allocation commonly follows a “storage bowl phenomenon” whereby the allocation of buffer storage space fits an inverted bowl pattern when the total storage space is also a decision variable     

Arm Motions in the Horizontal Plane

The principles of motion economy, “Motions of the arms should be made in opposite and symmetrical directions, and should be made simultaneously”, and, “Eye fixations should be as few and as close together as possible”, are evaluated. The two principles are replaced with five principles: 1. For one-hand motions, movements which pivot about the elbow are preferred to movements which pivot about the shoulder. 2. For one-hand motions, movements with the preferred hand are more desirable than movements with the non-preferred hand. 3. Two-hand motions are preferred to one-hand motions. 4. For two-hand motions, simultaneous motions are preferred to alternating motions. 5. For two-hand simultaneous motions, a pattern which minimizes eye fixations is preferred.     

The dynamic elastic buckling of a circular arch with finite displacements and initial imperfections

The equilibrium equations for elastic circular arches are established using the principle of virtual work. The nonlinear partial differential equations of motion are solved using a finite difference method (Park's method for time difference). The dynamic stability of a hinged and a clamped elastic circular arch with a uniform step load is analysed with finite deformations and initial geometric imperfections. Results show that the buckling mode varies with the value of the arch half angle, θ₀. The boundary condition and initial imperfection amplitude also effect the buckling mode. A nearly perfect arch usually buckling with a “direct” buckling form, while an imperfect arch with an “indirect” buckling form. The effect of θ₀ on the ratio p_d/p_s (p_d is the dynamic critical load and p_s the static critical load) is shown for different initial imperfections and different boundary conditions.     

Absolute calibration of accelerator beam energies by the crossover technique

An absolute method for the determination of the energy of a charged particle beam is described. The method is based on 0423 0450 V 2 scattering kinematics and exploits the variation with angle of the energy of particles scattered by elastic and inelastic processes 0423 0450 V 3 from different target nuclei. A determination of the angle at which particles scattered by two different reactions have the same 0423 0450 V 3 energy allows a precise calculation of the energy of the incident ion beam if the relativistic corrections are taken into account. A 0423 0450 V 3 simple system capable of supplying an absolute and accurate information on the beam energy in a short time has been designed and 0423 0450 V 3 tested. The system allows beam energy determinations over a wide energy range, from a few MeV up to several tens MeV and is not limited to some energy values in particular, in contrast with the use of resonance or threshold reactions. The system can in particular be employed for the calibration of accelerator beam energies in the energy interval typical of medium-energy commercial 0423 0450 V 3 cyclotrons, an increasing number of which are in operation in industry and in many fields of applied research. The paper briefly illustrates the theory underlying the “crossover” technique, describes the experimental apparatus and procedure and reports on experimental results for 12–36 MeV protons. The correction factors to be considered to fully exploit the accuracy of the technique 0423 0450 V 3 are discussed. The application of the method to the energy calibration of beams of deuterons and helium ions is described. A secondary and faster calibration procedure is also reported. This is derived from the main technique and can be routinely used once a number of energies have been determined and a sufficient data base of energy values has been built up. It is demonstrated that this secondary method is almost as accurate as the main technique.     

Viewing Strategy and Window Effects on Dynamic Visual-Inspection Accuracy

Equally-spaced product units, moving on a belt at a uniform velocity, were exposed for visual inspection over a fixed viewing window. Viewing windows were equal to the product unit interspacing and twice this distance to give respectively 1 and 2 product units within the window. Three different belt speeds were used. Subjects performed short runs of visual inspection using their self-directed strategies of viewing the sequence of product units and then these subjects repeated all conditions of this task using a “directed viewing strategy.” Improved viewing discipline was expected from this “directed” strategy and eye motion monitoring was employed to verify that the subjects used the “directed” strategy. Inspection errors of each type were observed under twelve experimental conditions. Both types of errors were found to be greater with: 1) the smaller viewing window, 2) self-directed viewing strategies in contrast to the “directed” strategy, and 3) higher belt velocities. Contrasts were also made between error types and between high- and low-performing subject groups. Inferences on the apparent cost of each error type were made from these data and compared with rational objectives. Economic implications are shown for these viewing-strategy and viewing window effects.     

A mechanistic model for the effect of stress ratio on the LEFM fatigue crack growth behavior of metals and alloys—II. Crack-brittle materials

A recently proposed mechanistic model for the effect of stress ratio, R, on the LEFM (long) fatigue crack growth behavior of “crack-ductile” materials is extended here to explain and predict similar behavior under similar conditions of “crack-brittle” materials characterised by the presence of “static” modes of fatigue fracture in stages II and III. It is shown that in these materials the stage I behavior is similar, but the stages II and III behave differently from crack-ductile materials. Mechanism-based existence of two types of stage II curves characterised respectively by “ pure shear mode ” (SM-II) and “mixed-mode” (MM-II), both plotting linear but having different slopes, is introduced. It is shown that while stage SM-II is insensitive, stage MM-II is significantly sensitive to R, in the same material. Similar to stage I, another “ moving pivot-point ” exists at the transition from SM-II to MM-II, which slides down the “ master shear-curve ” with increasing R. Assuming a critical K_max for the initiation of static modes, a critical R for saturation of these modes, and Paris-type growth relations, a quantitative predictive model containing growth equations for stages SM-II and MM-II, has been developed. Stage III is discussed only qualitatively. Reasonably good agreement was found between predicted curves at selected R-values and a relatively large volume of experimental data for steels, Al-alloys and Ti-alloys. This simple, alternative model may be used for obtaining quick, fairly accurate and conservative estimates of R-influenced crack growth rates for design applications in preference to crack-closure which frequently requires elaborate and tedious experimental procedures.