A Novel Investigation Into the Edge Effect Reduction of 4340 Steel Disc Through Induction Hardening Process Using Magnetic Flux Concentrators

Induction hardening serves as one of the best mass production processes used recently due to its ability to quickly generating high-intensity heat in a well-defined location of the part. Numerous advantages of this method make it a reliable technique to produce a thin martensite layer on the part surface that has compressive residual stresses. In this regard, the presented study is devoted to investigating utilizing induction heating for surface hardening of AISI 4340 steel disc. The purpose is to evaluate the performance of magnetic flux concentrators and the effects of the induction process parameter on the case-depth and edge effect in the surface hardening of the disc. Once the proper range of parameters is defined, Taguchi experimentation planning is used to frame comprehensive experimentation with the minimum possible trial. Then, the case-depth of discs is evaluated on their cross-sections (edge and middle plane) through hardness profile measurement of samples using a micro-indentation hardness machine. The results are then statistically analyzed using Analysis of Variance (ANOVA) and Response Surface Methodology (RSM) to determine the best combination of parameters to achieve maximum case-depth yet minimum edge effect. The goodness-of-fit regression models are then developed to predict the case-depth profile as a function of machine parameters based on linear regression utilizing case-depth responses in the edge and middle plane of discs. Results imply that maximum case-depth with minimum edge effect can be produced by using the highest heating time along with the average amplitude of the power, axial gap, and radial gap. This study gives a good exploration of case-depths optimized by setting up process parameters when magnetic flux concentrator is utilized, thus, a guideline to reduce discs edge effect in induction surface hardening application is given.

Cable stayed bridge over the Crati river in Cosenza

<p>The “Bridge over the Crati River” is a cable stayed bridge in a single span of 114.725m, designed by the architect Santiago Calatrava for the city of Cosenza. The main elements are the main tower, the deck, the cables, the reinforced concrete pier and the abutments; one of those is the restraint of the main rear cables. The steel tower has a variable cross section that tapers towards the top where the cables anchoring devices are located. It is inclined of 51° from the vertical and it is anchored by means of 2 anchor stays. The bridge is composed of two parts: a reinforced concrete structure with a span of 30 m that overhangs the railway and the composite cable-stayed bridge with a span of 114.725 m. The cross section of the bridge has a constant width of 24 m all over its length. The deck is sub-divided in four vehicle lanes, two in each direction, divided by a central pedestrian lane slightly raised in comparison with the vehicle lanes. There are 40 stays, placed symmetrically in respect to the middle plane of the structure and arranged according to a mixed geometry between an harp and a fan shape to facilitate the positioning of the anchoring devices at the top of the pylon.</p>

Evaluation of a monochromator with double cylindrical lenses for electron microscopy

In this paper, a monochromator (MC) with double cylindrical lenses (CLs) is evaluated. The MC achieved an energy resolution of 37 meV with high repeatability and stability. The double CLs realized the coincidence of the beam positions at the exit. The beam profiles were evaluated in a relative manner. Comparing two conditions with or without the MC, the beam kept equivalent sizes and showed sufficiently fine profiles. This is because the first-order aberration was a dominant factor under the experimental condition, where the second-order aberration was canceled by the middle plane symmetry of the MC optics and the beam was limited in small angles by the incident aperture. The experimental results mean that the MC with double CLs functioned properly as designed. The MC has the additional advantage of a simple structure. The results confirm that this MC has a high possibility for application to electron microscopy.

BENDING OF A SUBTLE-FINISHED PLATE ON ELASTIC BASE WITH SPECIAL CONDITIONS OF ITS WORK

In this article, an analytical solution is obtained for the problem of bending a semi-infinite plate on an elastic Winkler base, taking into account incomplete contact with the base and the influence of longitudinal forces applied in the middle plane of the plate. The analytical solution is obtained by the method of generalized solutions using integral Fourier transforms. Any analytical solution is the result, approaching the actual working conditions of the designed structures.

Design of a Micromachined Z-axis Tunneling Magnetoresistive Accelerometer with Electrostatic Force Feedback

This paper presents the design, simulation, fabrication and experiments of a micromachined z-axis tunneling magnetoresistive accelerometer with electrostatic force feedback. The tunneling magnetoresistive accelerometer consists of two upper differential tunneling magnetoresistive sensors, a middle plane main structure with permanent magnetic films and lower electrostatic feedback electrodes. A pair of lever-driven differential proof masses in the middle plane main structure is used for sensitiveness to acceleration and closed-loop feedback control. The tunneling magnetoresistive effect with high sensitivity is adopted to measure magnetic field variation caused by input acceleration. The structural mode and mass ratio between inner and outer proof masses are optimized by the Ansys simulation. Simultaneously, the magnetic field characteristic simulation is implemented to analyze the effect of the location of tunneling magnetoresistive sensors, magnetic field intensity, and the dimension of permanent magnetic film on magnetic field sensitivity, which is beneficial for the achievement of maximum sensitivity. The micromachined z-axis tunneling magnetoresistive accelerometer fabricated by the standard deep dry silicon on glass (DDSOG) process has a device dimension of 6400 μm (length) × 6400 μm (width) × 120 μm (height). The experimental results demonstrate the prototype has a maximal sensitivity of 8.85 mV/g along the z-axis sensitive direction under the gap of 1 mm. Simultaneously, Allan variance analysis illustrate that a noise floor of 86.2 μg/Hz0.5 is implemented in the z-axis tunneling magnetoresistive accelerometer.

LOCALIZED BENDING VIBRATIONS OF PIEZOCERAMIC TRANSVERSE POLARIZED PLATE

Problem of the piezoceramic plate polarized along the normal of the middle plane of the plate is solved, based on the assumptions of the hypothesis of Kirchhoff, taking into account the components characterizing the electric field. The equations of planar and bending vibrations are obtained. Localized bending vibrations are considered, and the effect of the electric field on the frequency of localized vibrations is investigated.

State space approach with FEM for the determination of structural behaviour of composite plates

Purpose An analytical investigation has been carried out for a simply supported rectangular plate with two different loading conditions by using 3D state space approach (SSA). Also, the accurate location of the neutral plane (N.P.) through the thickness of the plate can be identified: the N.P. is shifted away from the middle plane according to the loading condition. The paper aims to discuss these issues. Design/methodology/approach SSA and finite element method are used for the determination of structural behaviour of simply supported orthotropic composite plates under different types of loading. The numerical results from a finite element model developed in ABAQUS. Findings The effect of the plate thickness on displacements and stresses is described quantitatively. It is found that the N.P. of the plate, identified according to the values of the in-plane stresses through the thickness direction, is shifted away from the middle plane. Further investigation shows that the position of the N.P. is loading dependant. Originality/value This paper describe the effect of the plate thickness on displacements and stresses quantitatively by using an exact solution called SSA. Also, it is found that the N.P. of the plate, identified according to the values of the in-plane stresses through the thickness direction, is shifted away from the middle plane. Further investigation shows that the position of the N.P. is loading dependant.

Experimental Investigation of Transitional Natural Convection in a Cube Using Particle Image Velocimetry—Part I: Fluid Flow and Thermal Fields

An experimental investigation of transitional natural convection in an air filled cube was conducted in this research. The characteristic dimension of the enclosure is 0.35 m, and data were collected in the middle plane of the cavity. The Rayleigh number range examined is 5.0×107≤Ra≤3.4×108. This was achieved by varying the temperature on the hot and cold walls. The velocity field in the middle plane is measured using particle image velocimetry (PIV). Temperature measurements in the core of the enclosure indicate a linear profile. The average Nu number is also presented and compared against other correlations in the literature. This study attempts to close the gap of available experimental data in literature and provide experimental benchmark data that can be used to validate computational fluid dynamics (CFD) codes since the estimated error from PIV measurements is within 1–2%.