Search results

To characterise the optimal design parameters which are useful in hydrostatic radial journal bearings design.

A computer program is developed. With this program, designers can determine and select all design parameters of the hydrostatic radial journal bearings. Design parameters are searched with an optimisation algorithm which is used as a multi‐criteria optimisation approach.

With this approach, the designer can use the time effectively. This approach is faster and more precise than other approaches in the literature.

This approach is valid only for a specific type of hydrostatic journal bearings and within limits of shaft velocity. This approach should be improved.

This approach can especially be used for the hydrostatic journal bearings which are used for shafts‐turned middle velocities.

This paper fulfils the requests of the journal bearing designers exactly and quickly. In this research area, there is no another program.

This paper seeks to modify the determinations of flow rate and fluid resistance, which can be realized and confident from the measurements of flow rates in experiments.

According to coupled physics of solid membrane and lubrication fluid, finite element method is used simultaneously to determine membrane deflection and film thickness. Several cases are simulated by traditional method, finite element method and compared with experimental method for the flow rates and fluid resistances to present the modification of determination results.

The FEM results for the fixed eight‐section are approximated to actual flow rate and are consistent with the modified determination of the flow rates, and so the modified determinations of the flow rates are verified. When a computer of P4 with 1.8 GHz CPU and 512 MB RAM is utilized, time needed for traditional method or modified formula is fewer than one second. However, more than 4 h is required for FEM by using the same computer.

This study provides the modified method for the determinations of flow rate and fluid resistance in membrane‐type restrictors by using FEM. The FEM results can increase the determination accuracy of the flow rate and restriction coefficient in the design of membrane‐type restrictors.

Hybrid conical journal bearings have received great attraction by design engineers and researchers due to their incomparable performance. However, performance of these bearings is affected due to wear. This paper aims to present an analytical study concerning the performance of hole entry worn hybrid conical journal bearings.

The Reynolds equation governing the flow of lubricant in the clearance space along with the restrictor flow equations has been solved using finite element method.

The numerically simulated results of worn bearing performance parameters indicate significant change in the performance due to wear. Therefore, for semi cone angle γ = 25^°, the value of C¯₂₂ reduces by 24.6 per cent at the wear value of about 50 per cent of radial clearance for the given configuration of bearing.

The present results are original of its kind and surely useful to bearing designers and researchers in predicting actual performance of worn hole entry hybrid conical journal bearing.

The purpose of this paper is to introduce a new method to carry out the design optimization of the tool head system in the heavy‐duty machine tool where closed hydrostatic guideways with multiple pockets are employed.

A more accurate method of pressure calculation for closed hydrostatic guideways is introduced. Then, a multidisciplinary design optimization (MDO) model is formulated for design of a tool head system, which minimizes the highest pocket pressure under some constraints from machining accuracy and vibration resistance requirements as well as constraints from ballscrew design specifications. Finally, a metamodel‐based design space alternation (DSA) strategy is proposed to solve the optimization problem.

The results show that the maximum pocket pressure in a tool head system can be reduced over 47 percent with a proper design while all the constraints are satisfied. As a consequence, the tool head system can safely work under the maximum output pressure of oil supply system.

This paper introduces a more accurate method of pressure calculation for multi‐pocket closed hydrostatic guideways, develops a metamodel‐based MDO model for the tool head system, and proposes a DSA strategy to solve the MDO problem.

The purpose of this paper is to investigate experimentally slippers, which have an important role on power dissipation in the swash plate axial piston pumps. Since slippers affect the performance of the system considerably, the effects of surface roughness on lubrication have been studied in slippers with varying hydrostatic bearing areas and surface roughness.

An experimental set‐up was designed to determine the performance of slippers, which are capable of increasing the efficiency of axial piston pumps, in different conditions.

The findings suggest that the frictional power loss has been caused by surface roughness, capillary tube diameter, and the size of the hydrostatic bearing area, supply pressure and the relative velocity. In the case of the 0.7 and 9.5 μm surface roughness more power is needed to overcome the friction force between slippers and slipper plates, but less power loss occurs with the slippers with surface roughness of 1.5 μm. The slippers with surface roughness of 1.5 μm are considered, because of the optimum power loss. Moreover, the power loss decreases with increasing capillary tube diameter and supply pressure.

In order to investigate slipper behaviour under different operating conditions, with different capillary tube size and supply pressure an experimental work was carried out for finding exact design parameters of the real time system.

The purpose of this paper is to investigate the static stiffness of hydrostatic bearings with three constant compensations in types of constant‐flow pump, capillary and orifice, and both single‐action and double‐action variable restrictors with cylindrical‐spool, tapered‐spool, and membrane types by film gradient and recess pressure.

This paper utilizes the equations of flow equilibrium to determine the variations of film thickness or displacement of loading table with respect to the varying of recess pressure. For a hydrostatic bearing whose recess pressures are controlled by compensations, the stiffness characteristics can be presented directly by these variations.

The usage range of recess pressure and compensation parameters should be selected to correspond to a variation with smallest gradient.

This paper proposes an extensive database as a critical requirement for the selection of types and parameters of the compensation as to yield the acceptable or optimized characteristics in design of hydrostatic bearings.

Most of the preservation processes are based on temperature control; they are economical, safe and well established. However, for certain foods these processes modify the valuable nutritional content and organoleptic properties. In recent years, a number of emerging food preservation processes have been developed to fill a market niche in which the consumer prefers to pay more to obtain processed foods with their natural properties. The paper seeks to address this issue.

In this study a review of the available scientific data in relation to high hydrostatic pressure (HHP) and pulsed electric fields (PEF) are presented, highlighting the quality advantages, industrial application and safety risks in their use.

Nowadays, more than 100 industrial applications are marketed and several companies design process equipments. Damage to cell membranes, enzymes or DNA is the most commonly cause of microorganisms' death by these technologies. In addition, within a population of microorganisms, some bacteria are killed, others survive, and a proportion is damaged. The latter is the concern population as the damage may be repaired and the microorganism maybe viable during the product shelf life. Acquisition of new or modified characteristics such as higher treatment resistance could also occur. Another potential risk has to do with the death pattern of microorganisms showing deviations from the traditional log‐linear kinetic model (shoulders, tails and sigmoidal shape). Therefore the developing of simple mathematical models, which can adequately interpret this behaviour, is necessary.

In summary, PEF and HHP technologies need to be evaluated by industries and regulatory authorities and more affordable equipments should be marketed to expand their use at industrial level.

The paper aims to determine whether the type selection and parameters determination of the compensation are most important for yielding the acceptable or optimized characteristics in design of hydrostatic bearings.

This paper utilizes the equations of flow equilibrium to determine the film thickness or displacement of worktable with respect to the recess pressure.

The stiffness due to compensation of constant‐flow pump increases monotonically as recess pressure increases. Also, the paper considers which is larger than that due to orifice compensation and capillary compensation at the same recess pressure ratio.

The findings show that the usage range of recess pressure and compensation parameters can be selected to correspond to the smallest gradient in variations of worktable displacement or film thickness.

The purpose of this paper is to study the deformation of Green‐Naghdi (type III) thermoelastic solid half‐space under hydrostatic initial stress and rotation.

The normal mode analysis is used to obtain the analytical expressions of the displacement components, force stress and temperature distribution.

The numerical results are given and presented graphically when mechanical/thermal source is applied.

Comparisons are made in the presence and absence of hydrostatic initial stress and rotation and their effect is shown graphically.