Mechanical Engineering

Genetic programming techniques have been applied to a variety of different problems. In this paper, the authors discuss the use of these techniques in a virtual environment. The use of genetic programming allows the authors a quick method of searching shape and sound spaces. The basic design of the system, problems encountered, and future plans are all discussed.

Increasing software complexity, a growing number of vehicle variants, extensive diagnostic requirements, and stringent emission regulation requirements have significantly increased the calibration complexity. Shorter vehicle development times put further pressure on the development tasks. Technical advances have resulted in more tasks being done using simulation and on engine beds. But in-vehicle testing is still a crucial activity because human perception is still a key factor to assess vehicle calibration quality. But vehicle testing is expensive, so new techniques for in-vehicle calibration are required to reduce the time and cost without reducing calibration quality. In a vehicle development program, EMS calibration starts with base calibration optimization on the engine dynamometer. Once complete, the data must be validated on the vehicle and if necessary recalibrated. During the vehicle development phases several hardware and software modifications are necessary, which means t...

We present results on spatio-temporal correlations in the so-called mean drag version of the Durian bubble model in the limit of small, but finite, shearing rates, $\\dot{\\gamma}$. We study the rheology, diffusion, and spatial correlations of the instantaneous velocity field. The quasi-static (QS) effective diffusion co-efficient, $D_e$, shows an anomalous system size dependence indicative of organization of plastic slip into lines along the directions of maximum shearing. At higher rates, $D_e$ decays like $\\dot{\\gamma}^{-1/3}$. The instantaneous velocity fields have a spatial structure which is consistent with a set of spatially uncorrelated Eshelby transformations. The correlations are cut off beyond a length, $\\xi$. $\\xi\\sim \\dot{\\gamma}^{-1/3}$ which explains the $D_e\\sim\\dot{\\gamma}^{-1/3}$ behavior. The shear stress, $\\sigma$, follows a similar rate dependence with $\\delta\\sigma=\\sigma-\\sigma_y\\sim \\dot{\\gamma}^{1/3}$ where $\\sigma_y$ is the yield stress observed in the QS reg...

In certain aspects of our daily life, it is required that we eliminate or reduce the effect of vibrations. Thus, it is desirable to have a simple, compact and inexpensive way to do the same. Tuned vibration absorbers can be an efficient way to make this possible.
This discussion explains the effect of a wide range of operating parameters on the working of a tuned vibration absorber.

This paper deals with the analysis of active damping of geometrically nonlinear vibrations of doubly curved smart sandwich shells integrated with a patch of active constrained layer damping (ACLD) treatment. The substrate sandwich shell is composed of orthotropic laminated composite faces separated by a thick flexible core. The constraining layer of the ACLD treatment is made of the vertically/obliquely reinforced 1-3 piezoelectric composites (PZCs). The constrained viscoelastic layer is modeled using the Golla-Hughes-McTavish (GHM) method in the time domain. A three dimensional finite element (FE) model has been developed to study this coupled nonlinear electro-elastic problem. The numerical results indicate that the ACLD patch significantly improves the damping characteristics of the paraboloid and hyperboloid sandwich shells with laminated cross-ply and angle-ply facings for suppressing their geometrically nonlinear vibrations. Particular emphasis has been placed on investigating the effect of the variation of piezoelectric fiber orientation angle on the performance of the ACLD treatment. Unlike the doubly curved laminated composite shells, the performance of the ACLD treatment becomes maximum for causing active damping of geometrically nonlinear vibrations of doubly curved sandwich shells with laminated composite facings if the constraining layer of the treatment is made of obliquely reinforced 1-3 PZC.

The present study is concerned with the active control layer damping (ACLD) of the geometrically nonlinear vibrations of the smart functionally graded (FG) sandwich plates subjected to the thermal loading. The constraining layer of the ACLD treatment is considered to be made of the vertically/obliquely reinforced 1-3 piezoelectric composite (PZC) while the viscoelastic material is modeled by using the Golla-Hughes-McTavish (GHM) method in the time domain. A three dimensional coupled nonlinear electromechanical finite element (FE) model has been developed based on the first order shear deformation theory (FSDT) and Von Karman type nonlinear strain displacement relations to investigate the damping characteristics of the FG sandwich plates subjected to the thermal loading. Several FG sandwich plates with different thermal loading conditions have been investigated to evaluate the numerical results. Effects of metal or ceramic rich bottom surfaces subjected to the thermal loading, the variation of power-law index on the control authority of the ACLD patches have been thoroughly investigated. Emphasis has also been placed on investigating the effect of the variation of piezoelectric fiber orientation angle on the performance of the ACLD patches for controlling the geometrically nonlinear transient responses of FG sandwich plates.

A novel fuzzy carbon fiber heat exchanger (FFHE) is proposed in this study. The novel constructional feature of the FFHE is that the sinusoidally wavy carbon nanotubes (CNTs) are radially grown on the outer circumferential surface of the hollow cylindrical carbon fiber (HCF) heat exchanger. The effective thermal conductivities of the FFHE have been estimated by employing the method of cells (MOC) approach and the effective medium (EM) approach. The present study reveals that if the amplitudes of the radially grown sinusoidally wavy CNTs are parallel to the axis of the HCF then the effective axial thermal conductivity of the FFHE is significantly improved over that of the bare HCF heat exchanger (i.e., without CNTs). On the other hand, if the amplitudes of the radially grown wavy CNTs are transverse to the axis of the HCF, the effective transverse thermal conductivity of the FFHE is significantly improved over that of the bare HCF heat exchanger. It is also found that the CNT/polymer matrix interfacial thermal resistance does not affect the effective thermal conductivities of the FFHE. The present investigation suggests that exploiting the waviness of radially grown CNTs on the HCF a truly multifunctional and promising heat exchanger can be developed for advanced technological applications.

This paper deals with the investigation of active constrained layer damping (ACLD) of smart laminated continuous fuzzy fiber reinforced composite (FFRC) shells. The distinct constructional feature of a novel FFRC is that the uniformly spaced short carbon nanotubes (CNTs) are radially grown on the circumferential surfaces of the continuous carbon fiber reinforcements. The constraining layer of the ACLD treatment is considered to be made of vertically/obliquely reinforced 1-3 piezoelectric composite materials. A finite element (FE) model is developed for the laminated FFRC shells integrated with the two patches of the ACLD treatment to investigate the damping characteristics of the laminated FFRC shells. The effect of variation of the orientation angle of the piezoelectric fibers on the damping characteristics of the laminated FFRC shells has been studied when the piezoelectric fibers are coplanar with either of the two mutually orthogonal vertical planes of the piezoelectric composite layer. It is revealed that radial growth of CNTs on the circumferential surfaces of the carbon fibers enhances the attenuation of the amplitude of vibrations and the natural frequencies of the laminated FFRC shells over those of laminated base composite shells without CNTs.

The work is devoted towards incorporating the Murakami zigzag function (MZZF) for modelling the active constraining layer damping (ACLD) treatment of 'N' layered laminate cylindrical shells. The ACLD treatment in the patch form comprises of two material layers with the viscoelastic material layer constrained between the host shell and the smart 1-3 piezoelectric composite (PZC) material layer. The kinematics of deformation are derived successfully implementing the MZZF in the displacement fields. Virtual work principle has been employed for the finite element (FE) model to deduce governing equations of shell ACLD system in complete form. A feedback control system has been considered to arrive at closed loop governing equations of motion. Considering the above, a MATLAB code for the same is generated to emphasise on dynamics of the cylindrical shell ACLD system. Cylindrical shells with various lamination schemes have been considered to assess the validity and implementation of MZZF for ACLD treatment of shells. Also, the oblique orientation of the 1-3 PZC material layer and its effect on the damping behavior of the cylindrical shell has been thoroughly explored.

The relevant literature on machining operations selection in Computer-Aided Process Planning (CAPP) by decision trees, expert systems and neural networks has been reviewed, highlighting their contributions and shortcomings. This paper aims at contributing to the applicability of back-propagation neural network method for the selection of all possible operations for machining rotationally symmetrical components, by prestructuring the neural network with prior domain knowledge in the form of heuristic or thumb rules. It has been achieved by developing two forms of representation for the input data to the neural network. The external representation is used to enter the crisp values of the input decision variables (namely the feature type and its attributes such as diameter or width, tolerance and surface finish). The purpose of internal representation is to categorize the above crisp values into sets, which correspond to all the possible different ranges of the above input variables encountered in the antecedent ‘IF’ part of the thumb rules mentioned above. The input layer of the neural network has been designed in such a way that one neuronal node is allocated for each of the feature types and the sets of various feature attributes. In the output layer of the neural network, one neuronal node is allocated to each of the various feasible machining operation sequences found in the consequent ‘THEN’ part of the thumb rules. A systematic method for training of the neural network has been presented with the above thumb rules used to serve as guidelines for choosing the input patterns of the training examples. This method simplifies the process of training, reduces the time for preparation of training examples and hence the time to develop the overall process planning system. It can further help ensure that the entire problem domain is represented in a better manner and improve the quality of response of the neural network. The example of an industrially-relevant rotationally symmetrical workpiece has been analyzed using the proposed approach to demonstrate its potential for use in the real manufacturing environment. By this novel methodology, workpieces of complex shapes can be handled by investing a very limited amount of time, hence making it attractive and cost effective for industrial applications.

Surface roughness of the datum face is an important criterion to be considered for the selection of the datum during set-up planning as it can affect the tolerances among features. In this work, an experimental study on the effect of datum surface roughness on parallelism and perpendicularity tolerances in machining of prismatic parts by milling is carried out. A simplified mathematical model is developed to analyse the experimental findings. Statistical analysis of the experimental results has also been carried out. It is observed that sometimes a rough datum can provide better parallelism and perpendicularity than the smooth datum. Thus, the surface roughness of the datum should be decided judiciously considering the prescribed geometric tolerances and machining characteristics on a particular machine tool as well as the required surface integrity.