Search results

This paper reports on the development of a repulsive type magnetic bearing system and the importance of permanent magnet (PM) configuration on the attenuation of radial disturbance. A new configuration of the permanent magnet of the bearing system resulting in improved stiffness characteristics in the radial direction has been described. Prototype models have been designed and developed in our laboratory and experiments carried out.

A conveyor device is studied with the aim to reduce the friction between the inner surface of the beam and the chain. The lower is the friction between the chain and the beam, the lower is the surface wear. The magnetic repulsion force among permanent magnets (PMs) placed on the beam and on the chain is utilized to reduce friction. The paper aims to discuss these issues.

The considered magnetic suspension is realized with PMs in repulsive configuration; it is designed by solving a constrained optimization problem, with reference to the geometry of the 90° horizontal bend FlexLink WL322 conveyor. Flux density field and its gradient are evaluated using volume integral equation method, allowing to calculate the forces acting on the chain and the stiffness of the magnetic suspension.

The magnetic suspension prototype was manufactured and tested. The experimental and calculated values of the forces acting on the chain compares well. A stable horizontal equilibrium of the chain was obtained during both static and dynamical tests.

The quasi-static model used neglects the dynamical interactions among the elements of the chain, the PMs and loads weight during motions and the eddy current losses in the aluminium beam. However the dynamical tests on the prototype show that the chain motion is regular up to the nominal velocity all along the conveyor with the exception of the trailing edge of the 90° curve.

The tests on the prototype show the possibility of a removal or at least a reduction of the friction force between the chain and the inner side of the beam by means of a passive magnetic suspension. As a consequence a reduction of noise and vibrations and an increase of the mean-time-to-failure is expected.

Prototype testing shows that the unavoidable vertical instability of the magnetic forces has no practical consequence since, reducing the allowed vertical gap, the chain is stabilized by the gravitational force.

dding dopants to a powder bed could be a cost-effective method for spatially varying the material properties in laser powder bed fusion (LPBF) or for evaluating new materials and processing relationships. However, these additions may impact the selection of processing parameters. Furthermore, these impacts may be different when depositing nanoparticles into the powder bed than when the same composition is incorporated into the powder particles as by ball milling of powders or mixing similarly sized powders. This study aims to measure the changes in the single bead characteristics with laser power, laser scan speed, laser spot size and quantity of zirconia nanoparticle dopant added to SS 316 L powder.

A zirconia slurry was inkjet-printed into a single layer of 316 SS powder and dried. Single bead experiments were conducted on the composite powder. The line type (continuous vs balling) and the melt pool geometry were compared at various levels of zirconia doping.

The balling regime expands dramatically with the zirconia dopant to both higher and lower energy density values indicating the presence of multiple physical mechanisms that influence the resulting melt track morphology. However, the energy density required for continuous tracks was not impacted as significantly by zirconia addition. These results suggest that the addition of dopants may alter the process parameter ranges suitable for the fabrication of high-quality parts.

This work provides new insight into the potential impact of material doping on the ranges of energy density values that form continuous lines in single bead tests. It also illustrates a potential method for spatially varying material composition for process development or even part optimization in powder bed fusion without producing a mixed powder that cannot be recycled.

The stability and input voltage saturation is a common problem associated with an active magnetic bearing (AMB) system. The purpose of this paper is to design a control scheme that stabilizes the single degree of freedom AMB system and also tackle the problem of input voltage saturation in the AMB system.

The proposed control technique is a combination of two separate control schemes. First, the Backstepping control scheme is designed to stabilize and control the AMB system and then Chebyshev neural network (CNN)-based compensator is designed to tackle the input voltage saturation when the system control action is saturated.

The mathematical and simulation results are presented to validate the effectiveness of proposed methodology for single-degree freedom AMB system.

This paper introduces a CNN-based compensator with Backstepping control strategy to stabilize and tackle the problem of input voltage saturation in the 1-DOF AMB systems.

The aims and objectives of this research are to establish whether or not the transition into green building in high-rise construction is practical. This is after considering several perspectives including financial, economic, environmental, and social. This subsequently leads to an evaluation on whether or not the continuation with a standard conventional build of high-rise buildings remains to be the most feasible option. Such objectives, therefore, aim to allow for validation of how and why high-rise construction designs are impacted through green buildings effects.

Through six defined steps, the methodology commences with an introductory section of what it means to build green. This section is further broken down to evaluate what factors are involved in constructing a green building. Furthermore, the life cycle energy (LCE) is used as a framework to evaluate the knock-on effects of green buildings and subsequent high-rise construction design implications.

Through defining the ongoing relationship of green materials and sustainable design, various implications for high-rise constructions were discovered. First and foremost, it was determined that the LCE is the central consideration for any high-rise building design. In evaluating the LCE, and overall operating energy of the 50-year cycle of a building was carried out. As the results showed, the operating energy represents around 85% of the total energy that is consumed at the end of the 50 years cycle of the building. Precise LCE calculation can lead to a more efficient design for high-rise buildings. As a result, an increased understanding of the current status of green buildings within the construction industry is paramount. This understanding leads to a better insight into the contributing factors to green building in high-rise construction and the construction industry in general.

The potential contribution that can be gained from this research is the awareness that is raised in the research and development of green buildings in high-rise construction. This can be achieved by using certain materials such as new energy-efficient building materials, recycled materials and so on. This research will contribute to defining a new way of sustainable buildings, particularly for high-rise construction. The outcome of the research will be beneficial for practitioners such as design engineers and other related professions.

Low cycle fatigue tests on as‐cast Sn–Ag eutectic solder (96.5Sn–3.5Ag) were carried out using a non‐contact strain controlled system at 20°C with different frequencies (10⁻³–1 Hz). Steps at the boundaries of Sn‐dendrites were found to be the initiation sites for microcracks in the case of low frequency fatigue tests, while for high frequency tests, cracks predominantly initiated at the boundaries of subgrains formed within Sn‐dendrites. The link up of these cracks and the propagation of cracks inside the specimen occurred both transgranularly through Sn–Ag eutectic phases, and intergranularly along Sn‐dendrite boundaries and/or subgrain boundaries. Propagation of stage II cracks for various frequencies could be characterized by the C*‐parameter.

Fatigue crack growth (FCG) tests on lead‐containing solders and lead‐free solders have been carried out at frequencies ranging from 0.01 to 10 Hz and stress ratios in the range 0.1–0.7. The FCG resistance of lead‐free solders was found to be superior to that of lead‐containing solders. For both types of solder, cycle dependent behaviour is dominant for the tests at low stress ratios and high frequencies, while time‐dependent effects become important at high stress ratios and low frequencies. For cycle dependent testing conditions, cracks primarily propagated in a transgranular manner, while a mixed trans/intergranular mode of crack propagation was observed for testing conditions where time dependent effects were dominant. The propagation path of intergranular cracks depended on the test materials, and along interfaces. After the FCG tests, the formation of small grains was observed.

A numerical procedure is described for the elastic—plastic finite element analysis of crack propagation with branching. Constraint equations are used to model crack closing and sliding. Constraint conditions are imposed by using a penalty method for the self‐similar crack propagation and an elimination method for the off‐axis propagation. The contact condition is examined during plasticity iterations. The use of multiple constraints at the crack branching point to determine the mode of contact is discussed in detail. The method is then applied to (i) the self‐similar crack growth in a single‐edge notch specimen, (ii) the self‐similar propagation followed by interfacial splitting in a center‐cracked 0° composite plate, and (iii) the bifurcation of a crack in a compact tension specimen.

In practical engineering, oil filters often work under asymmetric cyclic loading. In order to improve the prediction accuracy of fatigue life of the oil filters under asymmetric cyclic loading, the effect of strain ratio and low cycle fatigue plastic deformation on fatigue life need to be considered. This paper aims to discuss the aforementioned objective.

First, strain-controlled fatigue tests with strain ratios of 0, 0.5 and −1 were carried out on the oil filter material 2A70-T6 aluminum alloy, and the test data were used to obtain strain fatigue life curves at three strain ratios. Then, based on the idea of the constant life curve method, the average value of the ratio of the strain amplitude corresponding to different strain ratios under the same partial life was defined as the strain ratio factor. Finally, the elastic-plastic factor was modified by the strain ratio factor, and a new fatigue life prediction model considering the effect of strain ratio was proposed.

The proposed model was validated, respectively, by fatigue test data of 2A70-T6 aluminum alloy, 2124-T851 aluminum alloy and oil filter and the results of the proposed model were compared with the Coffin–Manson equation, Morrow model and Smith–Watson–Topper (SWT) model, showing that the proposed model had higher applicability and accuracy.

In this work, a strain ratio factor is established based on the idea of the constant life curve method, and the strain ratio factor is used to modify the introduced elastic-plastic factor, and then a new fatigue life prediction model considering the influence of strain ratio and low cycle fatigue plastic deformation on material fatigue damage accumulation is proposed. The results show that the prediction results of the proposed model are in good agreement with the experimental data, and the proposed model has good fatigue life prediction ability considering the influence of strain ratio and lays a foundation for the fatigue life prediction of the oil filter.