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This study aims to utilize the equations of flow equilibrium to determine the variations of film thickness or worktable displacement with respect to the recess pressure for both open‐ and closed‐type hydrostatic flat bearings. The static stiffness can be not only presented directly by these variations but also determined by the differentiation of flow equilibrium equations.

The single‐action variable compensations of three types including cylindrical‐spool, conical‐spool and membrane restrictors are taken into consideration in this study. Specifically, this study presents that membrane restrictor and both spool restrictors with or without preload whilst considering initial opening.

Consequently, the usage range of recess pressure and optimal parameters of appropriate compensation type can be obtained from maximum stiffness and also according to smallest gradient in variations of worktable displacement or film thickness.

This article studies the influences of single‐action variable compensations for its design varieties. The determination of stiffness comes from the differentiating recess pressure with respect to worktable displacement. The large and small positive stiffness correspond to a negative slope in steep and plain gradient, respectively; the negative stiffness and infinite stiffness are obtained by positive gradient and zero gradient, respectively, in the variations of film thickness. The finding results can be expressed further in the relationship between the static stiffness and the static load.

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.

Oil-free heat pumps that use the system refrigerant gases as lubricants are preferred for thermal management in future space applications. This study aims to numerically and experimentally investigate the static performance of externally pressurized thrust bearings lubricated with refrigerant gases.

The refrigerant gases R22, R410A and CO₂ were chosen as the research objects, while N₂ was used for comparison. Computational fluid dynamics was used to solve the full 3 D Navier–Stokes equations to determine the load capacity, static stiffness and static pressure distribution in the bearing film. The numerical results were experimentally verified.

The results showed that the refrigerant-gas-lubricated thrust bearings had a lower load capacity than the N2-lubricated bearings, but they presented a higher static stiffness when the bearing clearance was less than 9 µm. Compared with the N2-lubricated bearings, the optimal static stiffness of the R22- and CO2-lubricated bearings increased by more than 46% and more than 21%, respectively. The numerical and experimental results indicate that a small bearing clearance would be preferable when designing externally pressurized gas thrust bearings lubricated with the working medium of heat pump systems for space applications.

The findings of this study can serve as a basis for the further investigation of refrigerant gases as lubricants in heat pump systems, as well as for the future design of such gas bearings in heat pump systems for space applications.

Bellows-type fluid viscous damper can be used to isolate micro vibration in high-precision satellites. The conventional model cannot describe hydraulic stiffness in the medium- and high-frequency domain of this damper. A simplified analytical model needs to be established to analyze hydraulic stiffness of the damping element in this damper.

In this paper, a bellows-type fluid viscous damper is researched, and a simplified model of the damping element in this damper is proposed. Based on this model, the hydraulic stiffness and damping of this damper in the medium- and high-frequency domains are studied, and a comparison is made between the analytical model and a finite element model to verify the analytical model.

The results show that when silicone oil has low viscosity, a model that considers the influence of the initial segment of the damping orifice is more reasonable. In the low-frequency domain, hydraulic stiffness increases quickly with frequency and remains stable when the frequency increases to a certain value; the stable stiffness can reach 106 N/m, which is much higher than the main stiffness. Excessive dynamic stiffness in the high-frequency domain will cause poor vibration isolation performance. Adding compensation bellows to the end of the original isolator may be an effective solution.

A model of the isolator containing the compensation bellows can be derived based on this analytical model. This research can also be used for dynamic modeling and vibration isolation performance analysis of a vibration isolation platform based on this bellows-type fluid viscous damper.

This paper proposed a simplified model of damping element in bellows-type fluid viscous damper, which can be used to analyze hydraulic stiffness in this damper and it was found that this damper showed stable hydraulic stiffness in the medium- and high-frequency domains.

The main purpose of this paper is to investigate the vibration isolation performance of a quasi-zero stiffness (QZS) metastructure by employing the band gap (BG) mechanism.

The metastructure QZS characteristic was investigated through static analysis by numerical simulation. Based on that, the BG mechanism is primarily used in this article to investigate the wave propagation characteristics of this structure. The model's dispersion relation is then examined using theoretical (perturbation method) and finite element techniques. The dynamic response of the finite-size systems and experimental analysis is used to confirm the vibration mitigation property under investigation. Finally, the model's ability to absorb energy was examined and contrasted with a traditional model.

The analytical analysis reveals the dispersion curve and the effect of the nonlinear parameter on the curve shifting. The dispersion curve in the finite element method (FEM) result depicts five complete BGs within the range of 0–1,000 Hz, and the BG width accounted for 67.4% of the frequency concerned (0–1,000 Hz). Eigenmodes of the dispersion curves were analyzed to investigate the BG formation mechanisms. The dependence of BG opening and closure on structure parameters was also studied. Finally, the energy absorption property of the QZS metastructure was evaluated by comparing it with a classical model. The QZS structure absorbs 4.08 J/Kg compared to the 3.69 J/Kg absorbed by the classical model, which reveals that the QZS demonstrates better energy absorption performance. Based on the BG mechanism, it is clear that this model is an excellent vibration isolator, and the study reveals the frequencies at which complete vibration mitigation is achieved. As a result, this model could be a promising candidate for vibration mitigation engineering structures and energy absorption.

The tough vibration issue, which is primarily experienced in mechanical equipment, will be resolved in this study. This study provides a precise understanding of the QZS metastructure's isolation of vibration, including the frequencies at which this isolation occurs.

THE elastic members used in flexible engine mountings are nearly always made of rubber, cither natural or synthetic, bonded or unbonded. The reason for this is that although metallic springs could be designed to have the required stiffness properties they have very little natural damping and would allow very large amplitudes to build up at resonant conditions unless some external damping device such as friction disks or oil dashpots were employed. Also it is a difficult matter to anchor a metallic spring in such a way that fretting will not occur at the fixing point. Rubber on the other hand has considerable damping properties and it is this (plus its high specific resilience) which has largely determined its pre‐eminence in this field.

This paper aims to assess the feasibility of additively manufactured wind tunnel models. The additively manufactured model was used to validate a computational framework allowing the evaluation of the performance of five wing models.

An optimized fighter wing was additively manufactured and tested in a low-speed wind tunnel to obtain the aerodynamic coefficients and deflections at different speeds and angles of attack. The flexible wing model with optimized curvilinear spars and ribs was used to validate a finite element framework that was used to study the aeroelastic performance of five wing models. As a computationally efficient optimization method, homogenization-based topology optimization was used to generate four different lattice internal structures for the wing in this study. The efficiency of the spline-based optimization used for the spar-rib model and the lattice-based optimization used for the other four wings were compared.

The aerodynamic loads and displacements obtained experimentally and computationally were in good agreement, proving that additive manufacture can be used to create complex accurate models. The study also shows the efficiency of the homogenization-based topology optimization framework in generating designs with superior stiffness.

To the best of the authors’ knowledge, this is the first time a wing model with curvilinear spars and ribs was additively manufactured as a single piece and tested in a wind tunnel. This research also demonstrates the efficiency of homogenization-based topology optimization in generating enhanced models of different complexity.

Gas thrust foil bearings (GTFBs) are used to balance the axial load of engines. However, in some working conditions of large axial force, such as the use of single impeller air compressor, the load capacity of GTFBs is still insufficient. To solve this problem, the load capacity can be improved by increasing the stiffness of bump foil. The purpose of this paper is to explore a scheme to effectively improve the performance of thrust foil bearings. In the paper, the stiffness of bump foil is improved by increasing the thickness of bump foil and using double-layer bump foil.

The foil deformation of GTFBs supported by three different types of bump foils, the relationship between friction power consumption and external force and the difference of limited load capacity were measured by experimental method.

The variation of the foil deformation, bearing stiffness, friction power consumption with the external force at different speeds and limited load capacity are obtained. Based on experimental results, the selection scheme of bump foil thickness is obtained.

This paper provides a feasible method for the performance optimization of GTFBs.

The purpose of this paper is to propose a method to simulate the polytropic process of air springs.

An iterative finite element method (FEM) is proposed.

The proposed method is reliable and effective in solving the polytropic process of air springs.

This work would be helpful for understanding the simulation of pneumatic structures, and the proposed modified FEM would be useful for improving the simulation of the mechanical behavior of an air spring.

The purpose of this paper is to improve static/dynamic characteristics of active-controlled hydrostatic journal bearing by using fractional order control techniques and optimizing algorithms.

Active lubrication has ability to overcome the unpredictable harsh environmental conditions which often lead to failure of capillary controlled traditional hydrostatic journal bearing. The research develops a mathematical model for a servo feedback-controlled hydrostatic journal bearing and dynamics of model is analyzed with different control techniques. The fractional-order PID control system is tuned by using particle swarm optimization and Nelder mead optimization techniques with the help of using multi-objective performance criteria.

The results of the current research are compared with previously published theoretical and experimental results. The proposed servo-controlled active bearing system is studied under a number of different dynamic situations and constraints of variable spindle speed, external load, temperature changes (viscosity) and variable bearing clearance (oil film thickness). The simulation results show that the proposed system has better performance in terms of controllability, faster response, stability, high stiffness and strong resistance.

This paper develops an accurate mathematical model for servo-controlled hydrostatic bearing with fractional order controller. The results are in excellent agreement with previously published literature.

The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-07-2020-0272