An experimental study on the long-term behavior of CFRP pultruded laminates suitable to concrete structures rehabilitation

The rheological behavior of structural materials has a significant role indeed in Civil Engineering, where concrete and FRP (Fiber Reinforced Polymer) materials undergo creep in normal environmental conditions, while steel exhibits a sizable creep only at high temperature (above 400 °C). With reference to RC structures strengthened by means of FRP laminates, FRP creep generally coexists with concrete cracking. The interaction between these phenomena should be taken into account in order to evaluate the structural durability. Here, the first results of a research program on creep in composite pultruded laminates used in Civil Engineering are presented, under various stress levels and in constant environmental conditions (many theoretical and experimental studies on creep have been performed so far in the aerospace and naval fields, but not as many in Civil Engineering). The specimens tested in this project are made of high modulus carbon fiber reinforced polymer – CFRP, whose mechanical properties are tailored for Civil Engineering applications. The tests are still in progress in the Material and Structures Testing Laboratory of the Civil Engineering Department of the University of Salerno (Italy).     

Studies on identification of an efficient and accurate integration scheme for piecewise linear dynamic problems

Engineering structures often have nonlinear characteristics. Many of these nonlinear systems could be modelled as piecewise linear. The dynamic analysis of such systems can be carried out by the direct integration of the mathematical model of the system. In this article, solution schemes are identified and qualified studying a single degree-of-freedom system and evaluated studying real-life engineering structures. As an alternative, a modified Newmark method with iteration for nonlinear forces and half-step error monitoring is presented. The modified scheme has been found to be efficient and accurate.     

Temperature responsive polymers as multiple function reagents in mineral processing

A processing scheme which uses a single chemical that has multiple functions to achieve both efficient mineral flotation and solids dewatering is presented. Temperature sensitive polymers which display hydrophilic/hydrophobic transitions in response to changes in temperature such as poly (N-isopropyl acrylamide) (PNIPAM) have been found to be useful as such multiple function reagents. This polymer can cause the mineral particles’ surfaces to be hydrophilic at temperature below the critical solution temperature (CST = 32 °C) and hydrophobic at temperature above the CST. Therefore, both particle surface wettability and inter-particle interaction forces are reversibly controllable. When the surface is hydrophilic, particle dispersion is achieved by repulsive inter-particle forces whereas when the surface is hydrophobic, particle aggregation is induced by inter-particle hydrophobic attractive forces. In addition, the hydrophobic surface condition allows for the attachment of particles to bubbles. Flotation and solid settling tests have been conducted with silica and kaolinite suspensions treated with (PNIPAM). Both effective suspension dispersion or hydrophobic aggregation and flotation without any additional collector have been demonstrated. In solid/liquid separation, rapid settling was obtained with hydrophobic aggregation at temperature above the CST and further sediment consolidation (and water release) occurred at temperature below the CST. The approach has the potential to reduce the amount and types of reagents required for mineral processing.     

Stabilized Nonstationary Heat Transfer in a Channel with a Boundary Regime on its Surface,that Varies Cyclically with Time

Journal of Engineering Physics and Thermophysics - Consideration has been given to laminar flow of a liquid with constant properties in a channel on whose surface the temperature or density of the...     

Anelastic relaxation processes due oxygen in Nb–3.1 at.% Ti alloys

In the last 50 years several studies have been made to understand the relaxation mechanisms of the heavy interstitial atoms present in transition metals and their alloys. Internal friction measurements have been carried out in a Nb–Ti alloy containing 3.1 at.% of Ti produced by the Materials Department of Chemical Engineering Faculty of Lorena (Brazil), with several quantities of oxygen in solid solution using a torsion pendulum. These measurements have been performed by a torsion pendulum in the temperature range from 300 to 700 K with an oscillation frequency between 0.5 and 10 Hz. The experimental results show complex internal friction spectra that have been resolved, into a series of Debye peaks corresponding to different interactions. For each relaxation process it was possible to obtain the height and temperature of the peak, the activation energy and the relaxation time of the process.     

Study of cyclic temperature fields in specimens tested for thermal fatigue

The method is suggested for calculating cyclic temperature fields heated by passing an electric current and cooled by compressed air on the basis of solving the problem of nonsteady state thermal conductivity for a rod with internal heat sources, second order asymmetrical boundary conditions, and nonuniform initial conditions. A method and equipment have been developed for contactless measurement of temperature fields for a specimen by means of a scanning photoresistor, a two-coordinate electronic storage oscillograph, and a photographic attachment. Results of calculating cyclic temperature fields by the suggested method are compared with those obtained by experimental data.60th Year of the USSR Institute of Civil Aviation Engineering, Kiev. Translated from Problemy Prochnosti, No. 9, pp. 36–41, September, 1989.     

ABET Accreditation for Engineering Management Programs

ABSTRACT

Accreditation guidelines for all engineering management programs have been proposed by the Accreditation Board for Engineering and Technology (ABET). These guidelines have been published by ABET for the purpose of receiving comments from interested parties. Comments will be addressed by ABET at its November 10, 1989, meeting. Suggestions for changes have been submitted by the American Society for Engineering Management (ASEM) and by the Engineering Management Division of the American Society for Engineering Education (ASEE). These changes have not yet been in corporated into the guidelines. This article describes the process by which ABET develops guidelines. It also contains the proposed guidelines and the suggested changes.     

Comparative investigations of the thermal expansivity of MgO at high temperature

Molecular dynamics simulations have been performed to investigate the thermal expansivity of MgO at high temperature using the very similar Lewis-Catlow and Stoneham-Sangster shell model potentials. In order to take account of non-central forces in crystals, the breathing shell model is also introduced in simulation. The volume thermal-expansion coefficient α_P of MgO dependence of the temperature T at 0 and 135 GPa have been obtained and compared with the available experimental and theoretical results. Compared with shell model potentials, the molecular dynamics results obtained using breathing shell model potentials are more compressible. At an extended pressure and temperature ranges, α_P has also been predicted.     

Effect of hydrogen on the machinability of VT5-1 alloy by cutting

Alloying of VT5-1 alloy with hydrogen decreases cutting forces and increases the service life cutting tools within a certain range of concentrations of hydrogen. The most pronounced favorable effect of hydrogen on the machinability of VT5-1 alloy is observed for its concentration of 0.5wt.% and may be caused by changes in the microstructure, by the effect of hydrogen plasticization, and by the enhanced brittleness of chips. Tsiolkovskii Moscow State University of Aircraft Engineering, Moscow Russia. Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 32, No. 6, pp. 107–112, November–December, 1996.     

Flow transitions in vacuum arc remelting

Abstract

The metallurgical structure of an ingot produced by vacuum arc remelting (VAR) depends critically on the temperature distribution within the liquid portion of the partially solidified ingot. This, in turn, depends on the fluid motion in the pool, since the dominant mechanism for transporting heat is convection. There are three primary sources of motion: buoyancy; Lorentz forces arising from the passage of current through the pool; and Lorentz forces arising from the presence of external inductors. These forces are constantly in competition with each other, and each tends to induce a quite different distribution of velocity and temperature. We examine the transition between these different flow regimes and derive dimensionless criteria which determine which regime is dominant. We show that the structure of an ingot produced by VAR depends critically on the temperature distribution within the liquid portion of the partially solidified ingot. This, in turn, depends on the fluid motion in the pool, since the dominant mechanism for transporting heat is convection. There are three primary sources of motion: buoyancy; Lorentz forces arising from the passage of current through the pool; and Lorentz forces arising from the presence of external inductors. These forces are constantly in competition with each other, and each tends to induce a quite different distribution of velocity and temperature. We examine the transition between these different flow regimes and derive dimensionless criteria which determine which regime is dominant. We show that modest changes in ingot current can produce radical changes in temperature distribution, and that weak, steady magnetic fields, of only ～1 Gs, can induce a powerful swirling motion which suppresses the normal flow.     

Material characteristics of an ER fluid and its influence on damping forces of an ER damper Part II: damping forces

This paper presents damping forces of a cylindrical ER damper for a small-sized passenger car. The arabic gum-based ER fluid filled in the damper is subjected to temperature variation and the variation of the damping forces is evaluated. The measured damping forces are compared with those predicted from Bingham model obtained at various temperatures in Part I. The ER damper is continuously operated up to 500 000 cycles and the variations of the operating temperature and damping forces are tracked. Using the Bingham model obtained from mechanical endurance test of the ER fluid in Part I, the variation of the damping forces is predicted with respect to the number of the operating cycle. The predicted damping forces are then compared with the measured ones to demonstrate the effectiveness of the Bingham models distilled from various environmental conditions in Part I.     

Bringing the Site into the Classroom: A Construction Engineering Laboratory

Recognizing that civil engineering students, as part of their construction training, must have closer contact with the real-world construction arena, a construction engineering laboratory has recently been set up at the Civil Engineering Department, Technion—Israel Institute of Technology. The laboratory is gradually being integrated into the curriculum of the Civil Engineering Department's Construction Engineering and Management Program. This paper describes the laboratory and its operation, and illustrates the laboratory's effectiveness in fulfilling its assigned role.     

Determination of the thermal conductivity of amorphous metallic alloys

Two techniques are suggested for identifying the temperature dependence of the thermal conductivity of a new class of materials. The results have been obtained for the metallic glass Co₇₇Fe₄Cr₇Si₈B₄.Institute for the Problems of Mechanical Engineering, Kharkov. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 63, No. 3, pp. 314–320, September, 1992.     

The IFMIF-EVEDA challenges in beam dynamics and their treatment

One major system of the IFMIF project (International Fusion Materials Irradiation Facility) is its two accelerators producing the neutron flux by accelerating deuteron particles up to 40 MeV against a lithium target. In the first phase called EVEDA (Engineering Validation and Engineering Design Activity), a full scale prototype accelerating particles up to 9 MeV is being studied and constructed in Europe, to be installed in Japan.Two unprecedented performances are required for the IFMIF-EVEDA accelerators: very high power of 5 MW and very high intensity of 125 mA CW. This leads to numerous unprecedented challenges in beam dynamics design and optimisation: harmful losses even for those less than 10⁻⁶ of the beam, non-linear dynamics induced by very strong space charge forces, difficulties for equipment and diagnostic implementations in the high compact structure, need of specific tuning strategies in this context.These issues are highlighted in this article, and the ways in which they are addressed are detailed.     

Elasticity studies of aluminium-substituted highT c superconducting materials

Longitudinal and shear wave velocities of Al-substituted Bi-Sr-Ca-Cu-O superconducting materials prepared by the ceramic technique were measured by the pulse transmission technique. Using the data, several elasticity parameters like Young’s modulus, rigidity modulus, Poisson’s ratio, Debye temperature etc were evaluated. Variation of elasticity parameters with composition has been explained in terms of binding forces between various atoms of the superconducting materials. Temperature variation of longitudinal wave velocity has also been measured and attempts have been made to explain the anomalies at 200 K.     

Temperature Field of a Methane Hydrate in the Process of its Decomposition at a Closed-Room Temperature

Journal of Engineering Physics and Thermophysics - The temperature field of a methane hydrate in the process of its decomposition at a closed-room temperature was investigated with the use of a...     

曲线形水中悬浮隧道的温度内力研究

采用混合法研究张力腿定位的曲线形水中悬浮隧道的温度内力。分析表明,由温度升高导致隧道膨胀(或收缩)所产生的轴向力很小,主要是径向力,同时还会产生扭矩和弯矩。通过数值实验给出张力腿的水平径向力与张力腿弹簧系数、隧道曲率半径、截面抗弯刚度及圆心角之间的变化关系。计算结果表明温度内力变化复杂,两组张力腿温度内力此消彼长。     

Speckle interferometry for analysing anisotropic thermal expansion—application to specimens and components

This paper describes a non-destructive optical technique, digital speckle pattern interferometry (DSPI), that has been developed particularly for strain analysis and has proved well suited for thermal deformation measurement. Fibre-reinforced composites with both metal and polymer matrices have been analysed by DSPI to determine their thermal expansion behaviour as a function of direction and temperature. Complete series of measurements can be performed quickly and without any restriction on the specimen shape. Engineering components including composite structures have been the subject of investigation. Besides quantitative results, real-time observation provides basic information for materials understanding.     

Comment on the minimum temperature hysteresis observed for the HCP-FCC4He transition

It is shown that the minimum temperature hysteresis of 30 mK, observed for the hcp-fcc⁴He transition near the triple point with the fluid, is a consequence of the adiabatic character of this transition.Research supported in part by grants from the Natural Sciences and Engineering Research Council of Canada.     

In-situ observations of the annealing of liquid lead inclusions entrained in an aluminium matrix

The changes in configuration of cylindrical inclusions of molten lead entrained in an aluminium matrix have been observedin-situ using hot-stage high voltage electron microscopy. Three distinct types of events were observed and analysed. The cylindrical inclusions spheroidized over a wide temperature range due to capillary forces; the resultant spherical inclusions migrated in the temperature gradient caused by electron beam heating; and impinging inclusions coalesced due to capillary forces. The kinetics of the spheroidization and sintering events are controlled by the rate of diffusion of Al in liquid Pb and the data yield estimates for this diffusivity at various temperatures. The mechanism operating during thermal migration depends on the radius of the inclusion; volume diffusion kinetics control for the larger inclusions (r>0.8 μm) and interface kinetics dominate the smaller inclusions (r<0.8 μm).