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A potential, novel lubrication mechanism involving two-phase fluids and porous bearing materials is examined in this study both theoretically and experimentally. Lubricating oils with a secondary particulate phase have been considered operating in oil-saturated porous media with the elements of the particulate phase acting as one-way valves on the pores, blocking and unblocking them, depending on the direction of contact load. The goal is to enhance the lubrication, mainly in starved contacts and in some ‘difficult’ applications, as for example in big end bearings for marine engines. The theoretical part of this work deals with the mathematical analysis of an oil-saturated, porous slab, in contact with a solid sphere and lubricated with a two-phase oil containing thin and soft platelets. The problem is analysed using Biot's theory of consolidation in porous media. A subsequent study deals with the effects of the maximum contact load, size, and number of pores of the porous medium, elastic modulus of the medium, and the viscosity of the oil used to carry the particulate phase, on the lubrication performance of the system. Furthermore, a rig was built to study the concept on a macroscale and the results are reported in the paper. Both the theoretical and the experimental work gave good indications that the concept works, at least in some cases. Potential problems with application of this lubrication mechanism have also been identified and are briefly discussed in the paper. [ABSTRACT FROM AUTHOR]

Deplayable structures based on the alternative forms of the Bennett linkage have been proposed and investigated by some researchers, which can be fully folded to a bundle and deployed to a flat surface. For aerospace applications, a deployable membrane structure based on the alternative form of the Bennett linkage is proposed and developed in the current paper. When fully deployed, four bars of the structure are not coplanar and the membrane tensioned by them can form a hyperboloidal surface. The compatibility between the structure and the membrane during the process of deployment is investigated, and preferred ranges of main design parameters are proposed to ensure the compatibility. The method to construct the assembly of the structure is also considered. In addition, three physical models were manufactured to verify the analytical investigations of the current paper. [ABSTRACT FROM AUTHOR]

The current paper reviews and discusses the results of some important papers on rail corrugation in detail, and introduces the experimental study on mechanism of rail corrugation formation on curved track carried out using a full-scale test facility. The corrugation with different wavelengths on the test wheel tread is reproduced in the experiment. It is found that the passing frequency of the reproduced corrugation is the same as the excited natural frequency of the test rig. The natural frequencies of the test rig are identified through the modal experiment of the test rig using impulse method. The corrugation in the experiment is numerically analysed in the paper. In the analysis the contact geometry and steady creepage of the wheels/rollers in rolling contact are calculated. Kalker's rolling contact theory with non-Hertzian form is modified and used to calculate the frictional work density in the contact area of the wheel/roller. A model concerning the material loss per unit area proportional to the frictional work density is used to determine the wear on the contact surface of the wheel. The numerical results are in good agreement with the experimental results. They show that the test rig vibrating at high frequency can initiate a corrugation passing the same frequency on the smooth contact surface of the wheel under specific test conditions. The specific conditions include the non-zero steady creepage of the wheelset/rollers, the circumference of the wheel rolling circle approximately equal to multiple of the corrugation wavelength. The corrugation wavelength depends on the excited natural frequency of the test rig and the rolling speed of the wheelset. The depth and growth speed of corrugation depend on the fluctuation amplitude of the contact normal load of the wheelset/rollers. [ABSTRACT FROM AUTHOR]

The many facets of Bennett's investigation into his skew four-bar linkage and its several extensions have given rise to an abundance of studies by other workers. Among his imaginative endeavours was the deployment of a double helix to convert his planar 12-bar network into a spatial counterpart. A geometrically attractive idea, its algebraic equivalent had been difficult to realize because of a lack of underlying analytical relationships. As well, recent papers have revealed apparent shortcomings in Bennett's representation. The present work is an attempt to provide a complete algebraic treatment of Bennett's novel device. [ABSTRACT FROM AUTHOR]

Flexure-based compliant mechanisms have been used in ultra-precision stages, stages for nano-imprint machines, AFM scanners, and MEMS structures, etc. In this paper, a mathematical static model for flexure-based compliant mechanism driven by piezo stacks is derived. The force vector generated from piezo stacks was linearized in terms of displacement and applied voltage vectors. Then, the piezo force vector was substituted into the static model of a compliant mechanism. Finally, the force and the displacement vectors of input bodies, and the block force and the displacement vectors of output bodies were derived. The derived mathematical model was verified by FEM analyses and experiments. The derived mathematical model can well describe the static performance of a flexure-based compliant mechanism driven by piezo stacks. [ABSTRACT FROM AUTHOR]

Correlation integral method (CIM) is a perfect method for the detection of stall and surge. However, CIM is very time-consuming due to its computational complexity. This paper aims to resolve the disadvantage. First, the segmented computation of correlation integral (CI) is deduced; second, the mapping criterion is given; finally the improved correlation integral method (ICIM) is proposed. The criterion can search the repeated subset of points and pair of subsets efficiently, which aids the ICIM in eliminating all redundancy caused by the overlapping of consecutive time windows. By applying ICIM to the detection of surge precursor in centrifugal compressors, it is illustrated that CI has a sharp decline more than 1.5 s prior to the fully developed surge. Also the processing time of ICIM is much shorter than that of CIM. The explicit detection of surge precursor, its rapid recognition, and the resulting longer time available for the feedback preventing the surge are the principal advantages of this approach. These studies are significant for CIM and will boost its application in numerous fields, especially in the detection of stall and surge. [ABSTRACT FROM AUTHOR]

It is well known that there exist many more singularities in parallel manipulators. At the singular point, the motion of the parallel manipulator is uncertain. In order to make parallel manipulators produce concrete output at singular points, and go away from singular points with the desired configuration, the method for the manipulator to pass through type-II singularities with its original configuration has been investigated in the paper. First, the semi-regular hexagon Gough–Stewart manipulator is taken as an example to analyse the configuration bifurcation characteristics at the vicinities of the type-II singularities going with the input parameters. The studies show that on different configuration branches, the singularity-free moving region is different, and there are two or four assembly configurations in the space above the base for the same group of input parameters. By researching transition behaviours of the configuration bifurcation curves under the disturbances applied to the other input parameters, it is found that under a suitable disturbance the perturbed persistent configuration will go away from the non-persistent configuration. Based on this kind of character, a novel method for the manipulator to pass through the turning point with its original configuration has been presented. [ABSTRACT FROM AUTHOR]

Until very recently, the wrong belief that given forces in mechanics cannot depend on acceleration was a wide-spread opinion. As a consequence, little effort, if any, has been made to develop a formal mechanical theory for such forces.At the present time, a class of new problems involving the study of mechanical systems acted on by forces that depend on acceleration and higher derivatives can be considered on the basis of traditional statements of mechanical problems (of stabilization, stability, optimal control, etc.).The current paper is primarily devoted to equilibrium stabilization using acceleration-dependent forces. For definiteness, the analysis is concerned with the tilting railway car, which is a mechanical system where the use of such forces is indispensable. In spite of the specificity of this system, the analysis allows one to get an idea of the generalities of the use of acceleration-dependent forces in mechanics and shows that they can be used in practice to good advantage. [ABSTRACT FROM AUTHOR]

Vehicle ride comfort could be improved by controlling passenger vertical accelerations induced by random road excitations. In the current paper, to provide a certain level for the passenger's sensation of comfort, optimum values for all elasto-damping elements of the seat and passive suspension system are selected numerically by a genetic algorithm (GA). The root-meansquare (RMS) values of vertical acceleration are first calculated at a series of centre frequencies by power spectral density of an actual random road excitation and then the optimized parameters are found by minimization of difference between the obtained RMS values of acceleration and the boundary values specified by the ISO2631. For determining the applicability of the GA in optimization of the passive suspension system, this method is initially applied to a simple twodegrees-of-freedom (2DOF) half-car model and the results are compared with those obtained by non-linear programming as a gradient-based method. Since the GA proves to be an efficient optimization method, it is easily extended to a more complete 5DOF model. Simulation results demonstrate improvement of vehicle ride comfort and capability of the suggested method in optimizing multi-DOF (MDOF) mechanical systems. [ABSTRACT FROM AUTHOR]

In many cases, mechanical systems include elements that differ greatly in inertia characteristics. It seems to be quite natural for a researcher who has to deal with such a system to have the desire to neglect its comparatively small inertia characteristics by putting them equal to zero. On such a simplification, the researcher has to do with a mechanical system that, along with ‘massed’ bodies (all inertia characteristics of which are distinct from zero), also includes ‘massless’ bodies (some inertia characteristics of which are zero). An important feature of systems of massed and massless bodies is that they may turn out to be singular. The analysis of systems of this type, in comparison with regular ones, involves some additional problems, whose solution, despite currently available methods of study of singular and singularly perturbed equations, may present a considerable challenge.In the current paper, the notion of the 'rank of a system of massed and massless bodies' is introduced, and an approach to the solution of the above problems based on this notion is proposed. This approach makes it possible to write generalized Lagrange equations for singular mechanical systems, to identify conditions for going from singularly perturbed equations of motion to singular ones to be correct, to identify conditions for the unique existence of the solution of the resulting singular equations of motion and to write them in normal form. [ABSTRACT FROM AUTHOR]

In this paper a fault-detection (FD), filter-design method has been proposed for linear parameter-varying (LPV) systems. The FD filter is an optimal H∞ Luenberger observer synthesized by minimizing frequency conditions that ensure guaranteed levels of disturbance rejection and fault detection. Via the bounded real lemma (BRL) and the separation principle the design method is formulated as a convex linear matrix inequality (LMI) optimization problem. The resulting residual generator is parameter-dependent and uses the plant parameter assumed measurable online. Finally, an FD threshold logic is proposed in order to reduce the generation of false alarms. The effectiveness of the design technique is illustrated via a numerical example. [ABSTRACT FROM AUTHOR]

Majority of engineering system designs are deemed to be optimization problems with unknown multiple variables that are more than the known information and data. Several numerical algorithms have been evolved in the past half a decade in an attempt to improve the accuracy of results. The aim of this paper is to provide a perfect solver for the non-linear, single objective, and multi-variable optimization problems. The algorithm termed primer interfaced algorithm for non-linear optimization (PIANO) is a resolved solution methodology based on Hegde's primer value theorem. The methodology is formulated and developed by computing a primer adapter, which is interfaced with coefficient of the terms of constraints and objective functions to arrive at the decision vector. To demonstrate the procedure, two problems from the mechanics of structure are considered as exercises. The results are compared with the results recently published in the literature. The chosen examples for the optimization are a four bar truss and a simply supported beam with uniformly distributed load. The results of PIANO are compared with the results of fuzzy dynamic programming, and crisp optimal solutions are reported in the literature. The authors are sure of absolute contained perfection in the application of PIANO. To the authors' understanding, PIANO is original, new, and different. [ABSTRACT FROM AUTHOR]

Passive isolation systems based on springs are often used to resist vibration due to their low cost and reliability. The basic principle of these systems is that they try to decrease the natural frequency as low as possible. Stiffness of the overall spring system must be low to make the isolator achieve the low natural frequency. An approach to obtain the low dynamic stiffness is the combination of a negative stiffness system and a common isolator. There are, however, a lot of negative stiffness systems, and selecting the best one is difficult. In this paper, mathematical analyses are used to determine the best system that is then applied to construct a vertical isolator of the anti-vibration table. [ABSTRACT FROM AUTHOR]

In this paper, a stochastic modelling method is used to study the reliability evaluation problem of fault-tolerant control systems (FTCSs). The faults in the system are described by a Markov chain, while the fault detection and isolation (FDI) and system operation for reliability evaluation are described by two semi-Markov chains. The semi-Markov description of FDI removes the restrictive memoryless assumption in Markov models and provides a general model for cyclic FDI schemes. Furthermore, a reliability index and evaluation method are presented for FTCSs. This index reflects the control performance and hard deadline and can be used as a quantitative reliability measure for FTCSs. [ABSTRACT FROM AUTHOR]

The paper describes a novel algorithm for solving the synthesis problem of a multi-link wheel-guiding mechanism with a known topology and dimension. The synthesis objectives contain the elastokinematical specifications, described by a set of spatial displacements that the wheel carrier should undergo from a design position under specified loads corresponding to typical car manoeuvres. Radial spring rates of cylindrical elastomeric bushings, embodied in the suspension rods, are considered as design variables. Relations between the design variables and the objectives are established using the first-order kinematics and screw calculus, under assumptions about small displacements and linear force-deflection characteristics of the flexible elements. The problem is solved by using a constrained linear least-squares algorithm. Depending whether the input data is provided by a designer or acquired during suitable experiments, the algorithm can be used for synthesis or estimation of the stiffness parameters. Numerical examples are solved for two five-rod suspensions, with the same topology but different configuration and dimension, installed at rear-driven axles of actual cars. Static spring rates of the five rod-bushings are determined, for which both suspensions satisfy the formulated ride/handling criteria in the best way. Fundamental characteristics and limitations of the suspensions are described. [ABSTRACT FROM AUTHOR]

In this paper, a new design methodology is introduced to automate the configuration layout design and geometric sizing of rotary-wing micro air vehicles (MAV). The objective of this design-optimization problem is to organize a given set of components and payloads such that the resulting flight vehicle has the most compact overall size and still fulfils the given physical and control constraints. Genetic algorithm (GA) is chosen as the optimization engine because of its proven robust performance. A detailed discussion is presented to explain how the rotary-wing MAV design problem can be formulated as a GA optimization problem. From the case study performed, it is demonstrated that the proposed methodology is able to achieve the design goal. [ABSTRACT FROM AUTHOR]

This paper presents a numerical approach for modelling multiple-crack fatigue growth in a plane elastic infinite plate. It involves a generation of Bueckaler's principle, a displacement discontinuity method with crack-tip elements (a boundary element method) proposed recently by the author, and an extension of Paris' equation to a multiple-crack problem under mixed-mode loading. Because of an intrinsic feature of the boundary element method, a general multiple-crack growth problem can be solved in a single region formulation. In the numerical simulation, for each increment of crack extension, remeshing of existing boundaries is not necessary. Crack extension is modelled conveniently by adding new boundary elements on the incremental crack extension to previous crack boundaries. As an example, interaction among three parallel cracks under cyclic load is investigated using the numerical approach. Many numerical results are given. [ABSTRACT FROM AUTHOR]

The thrust strategy for extra-atmospheric flight plays a key role in the optimization process for the ascent trajectory of the launch vehicles. In this paper optimization software for the ascent trajectory of the launch vehicles is reported, and the performances, obtained using Q-guidance, proposed by Battin are compared with those obtained solving an optimal control problem via the calculus of variations. The differences with respect to the optimal case are related to the velocity-to-be-gained value. The condition where Q-guidance is a good alternative is defined. The thrust strategies are applied to maximize the payload mass of a four-stage launcher similar to the European launcher Vega. The results are presented in terms of final payload mass and thrust strategies. This comparison is made firstly for the complete trajectory and then only for the last-stage trajectory. In the latter case the performances are compared considering both planar and out-of-plane trajectories. [ABSTRACT FROM AUTHOR]

Nowadays, moulders and customers pay increasing attention to parts warpage, which becomes a determining quality criterion for parts acceptance. The accurate prediction of warpage of injection-moulded parts is an important and challenging task for numerical simulation of injection moulding. In this paper, the numerical analysis of warpage in injection-moulded parts was carried out in consideration of the residual stresses produced during both the packing and the cooling stages. For residual stress analysis, a thermorheologically simple viscoelastic material model was introduced to consider the stress relaxation effect and to describe the mechanical behaviour according to the temperature change. The deformation of injection-moulded parts induced by the residual stress was calculated on the basis of the theory of shells, represented as an assembly of flat elements formed by combining the constant strain and the discrete Kirchhoff triangular element. Experimental research on a flat plate was also performed to study the effect of mould structure and processing parameters on warpage. The simulation results were also compared with the experimental data for verification of the developed programme. It was found that the predictions were in agreement with experimental data, especially in qualitative analysis. [ABSTRACT FROM AUTHOR]

A new graphical representation of normal stress at one point and its corresponding deviatoric stress state are presented for the first time in this paper. The relationship between the normal stress figures and the deformation types is analysed as well. In addition, the internal hydrobulging forming process is analysed by using the normal stress figure. [ABSTRACT FROM AUTHOR]