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This article investigates different types of compound die piercing punches and double cutting operation parameters in terms of optimization using finite element technique, Taguchi method, regression analysis, and analysis of variance. The article overcomes the current knowledge gap in studying various cutting edges of piercing punches such as flat, chamfered, flat edge with concave hemisphere, and convex shaped when using the compound dies in stamping operations. The analysis of the compound die is carried out using ANSYS software. The main focus is to determine the contribution of key parameters for obtaining optimum cutting tool design. The best piercing punch is selected based on minimum burr height of the product. The values of cutting process parameters and burr heights have been analyzed using Minitab software. The results obtained indicate that the burr heights of the final product are at a minimum when the sheet metals are thicker and larger when the sheets are thinner. The chamfered and convex punches provided minimum burr heights which are as low as 0.034 mm for a typical sheet metal. This study provides a better outcome compared to the available experimental data in the literature. The investigation also designed efficient compound dies resulting in improved product quality.

Frictional behaviour of mixed Elasto-hydrodynamic lubrication (EHL) arises from the coupling of the lubricant fluid and asperity interaction frictions. Due to the difficulties in modelling asperity interaction friction, existing approaches often use a constant friction coefficient obtained in boundary lubrication to approach the asperity interaction friction coefficient in mixed EHL. In this study, the asperity interaction friction is, for the first time, considered to result from either the boundary film friction or solid-to-solid ploughing and adhesion friction depending on the local contact and deformation conditions. The friction of mixed EHL was predicted by the combination result of lubricants fluid, boundary film, and solid-to-solid frictions. This development provides an alternative and cost effective method to estimate friction coefficient in mixed EHL.

A non-linear isotropic finite element (FE) model of a 29-year-old human crystalline lens was constructed to study the effects of various geometrical parameters on lens accommodation.The model simulates dis-accommodation by stretching of the lens and predicts the change in surface profiles of the lens capsule, cortex and nucleus at select states of stretching/accommodation. Multiple regression analysis (MRA) is used to develop a stretch-dependent mathematical model relating the lens sagittal height to the radial position of the lens surface as a function of dis-accommodative stretch. A load analysis is performed to compare the finite element results to empirical results from lens stretcher studies. Using the predicted geometrical changes, the optical response of the whole eye during accommodation was analysed by ray-tracing.Aspects of lens shape change relative to stretch were evaluated, including change in diameter, central thickness and accommodation. Maximum accommodation achieved was 10.29 D. From the multiple regression analysis, the stretch-dependent mathematical model of the lens shape related lens curvatures as a function of lens ciliary stretch well (maximum mean-square residual error 2.5 × 10(-3 ) μm, p0.001). The results are compared with those from in vitro studies.The finite element and ray-tracing predictions are consistent with Ex Vivo Accommodation Simulator (EVAS) studies in terms of load and power change versus change in thickness. The mathematical stretch-dependent model of accommodation presented may have utility in investigating lens behaviour at states other than the relaxed or fully accommodated states.

In this paper, the low frequency vibro-acoustic responses from a submerged hull are attenuated using passive, active, and hybrid control strategies. An analytical model representing a simplified physical model of a submarine hull is developed, including the effects of ring-stiffeners, bulkheads, and external fluid loading. At low frequencies, rotation of the propeller results in discrete tones at the blade passing frequency and its harmonics. The fluctuating forces at the propeller are transmitted through the propulsion system, resulting in excitation of the low frequency hull vibrational modes, which in turn results in a high level of structure-borne radiated noise. In this work tuned vibration absorbers, active vibration control, and hybrid vibration absorbers are used to attenuate the breathing and bending modes of the submerged hull. The control performance of a hybrid vibration absorber is compared to the attenuation achieved using a passive absorber and the control performance of a fully active system. Results show that implementation of the hybrid vibration absorber results in significant attenuation of the structural and acoustic responses of the hull. The hybrid vibration absorber also requires a control force of lower magnitude compared with a fully active control system.

Acoustic engineers are faced with the challenge of minimising reverberation time in their designs so as to contribute to the health and well-being of those traveling by train and those on the platforms. Although the problem is easy to identify, it is not as simple to solve. The acoustical environment of a train tunnel is complex, with a variety of noise contributing factors such as train announcements, speech of commuters, ventilation systems, electrical equipment and wheel and rail noise. As a result, there is some difficulty in modeling the complete acoustic environment with computational or acoustic first principles. In this study, an experimental rig was constructed to model the acoustic behavior within a tunnel. The modal properties for the 300 Hz to 1500 Hz range, including resonances and mode shapes were identified and were shown to successfully correspond to theoretical results and a computational model created in COMSOL using Finite Element Analysis.

Almost all of the pressure components produced at present are produced by welding and a good majority of them are used for high temperature application where creep damage can occur and requires the attention of the pressure equipment designers. An accurate creep life prediction model is required to predict the life of such pressure components. All of the creep life prediction models available today are either inaccurate or too cumbersome to apply. There is a need for an accurate creep life prediction model that would overcome the shortcomings of the existing models. Research team at UNSW have developed a creep life prediction model [Mahmood et al., in Front Mech Eng, 8(2):181–186, 2013; Mahmood et al., in Eng Integr J, 34:6–13, 2013; Mahmood et al. in Intl J Reliab Saf Eng Syst Struct D, 1(1):43–51, 2011] that accurately predicted the creep life of seamless pipes when applied to them. This paper is an extension of previous work and investigates the accuracy of the model when applied to a thick-walled pipe having a circumferential weld to predict the creep life of a welded pressure component. The paper shows that the proposed model can predict the creep life of the vessel with an error of less than 1 %.

This paper demonstrates the application of a new multiaxial creep damage model developed by authors using stress traixiality to predict the failure time of a component made of 0.5%Cr-0.5%Mo-0.25%V low alloy steel. The model employs strain energy density and assumes that the uniaxial strain energy density of a component can be easily calculated and can be converted to multi-axial strain energy density by multiplying it to a function of stress trixiality which is a ratio of mean stress to equivalent stress. For comparison, an elastic-creep and elastic-plastic-creep finite element analysis (FEA) is performed to get multi-axial strain energy density of the component which is compared with the calculated strain energy density for both cases. The verification and application of the model are demonstrated by applying it to thin tube for which the experimental data are available. The predicted failure times by the model are compared with the experimental results. The results show that the proposed model is capable of predicting failure times of the component made of the above-mentioned material with an accuracy of 4.0%.

A key step in the design of an accommodating gel to replace the natural contents of the presbyopic human crystalline lens is to find the equivalent homogeneous mechanical and material properties of the gel that yield comparable optical response as the lens with gradient properties. This process is compounded by the interplay between the mechanical and optical gradient. In order to find uniform properties of the lens both gradients need to be considered. In this paper, numerical ray-tracing and finite element method (FEM) are implemented to investigate the effects of varying the uniform elasticity and refractive index on the accommodative amplitude. Our results show that the accommodative amplitude be expressed as a function of gel refractive index and Young's modulus of elasticity. In other words infinite sets of elasticity and refractive index exist that yield a certain amount of accommodation.

The gradient refractive-index (GRIN) inside the crystalline lens has been described using a number of functions. One of the most widely used functions for this purpose is the polynomial. Changing the order of the GRIN polynomials alters the relative refractive index profile across (radially) and along (axially) the lens. In this paper, numerical methods are used to investigate the effects of varying GRIN polynomial order on the accommodative response of the lens; in particular, accommodative amplitude. Our results suggest that the GRIN order does not have a significant influence on the accommodation amplitude.

Resource constraints have forced engineering schools to reduce laboratory provisions in undergraduate courses. In many instances hands-on experimentation has been replaced by demonstrations or computer simulations. Many engineering educators have cautioned against replacing experiments with simulations on the basis that this will lead to a misunderstanding of the role of experimentation in engineering practice. However, little is known about how students conceptualize the role of experimentation in developing engineering understanding. This study is based on interviews with third-year mechanical engineering students. Findings are presented on their perceptions in relation to the role of experimentation in developing engineering knowledge and practice.

Lagging formed of jackets of porous materials such as glass wool and of impervious materials such as metal sheets are widely used to attenuate the sound radiated from pipes. A procedure is described for calculating the insertion losses produced by such lagging. The procedure yields the insertion losses corresponding to each of the low order mode types of the pipe. These are breathing, bending and ovalling mode types. Impedance and pressure transfer formulae for the various jacket types are given in terms of the fundamental properties of the jackets. The porous jacket, for example, is defined by its inner and outer diameters and the flow resistivity of the porous material. These formulae enable the frequency dependent insertion loss produced by an arbitrary pipe lagging to be determined. A comparison of the insertion losses predicted by this procedure with published results is given.

Conventional pipe laggings incorporate a porous jacket and an impervious outer cladding sheet. It has been observed during investigations of such pipe laggings that a simple porous jacket applied by itself to a pipe can actually increase the sound radiated. Reasons for this phenomenon are discussed. The effect of a rigid frame porous jacket around a pipe is examined theoretically for the breathing, bending, and ovalling modes of pipe vibration. The predicted insertion loss associated with the bending mode of pipe vibration is compared with the corresponding experimental result and some of the results of a parametric study are given.

A procedure for estimating the insertion losses produced by simple pipe laggings formed of either a porous jacket alone or a porous jacket covered by an impervious jacket is presented. The procedure is based on a model involving an infinitely long pipe, which is supporting various types of structural waves. It is pointed out why the bending type of structural wave is often of particular importance. Data that enables the insertion loss produced by laggings for the bending type of structural wave in the lagged pipe is given in a dimensionless form. An example of how this data can be used to predict the insertion loss produced by a typical lagging applied to a typical pipe is given.

Sound transmission loss (STL) tests of acoustic insulation panels are commonly performed in large reverberation rooms. Large size rooms are required by acoustic standards to ensure that a large number of modes can be excited in the frequency range of interest, to create a diffuse sound field. However for STL measurements in low frequency range small enclosures should be able to provide adequate homogenous sound fields, namely ‘pressure sound fields’. The expected effect of the air sealed in an enclosure backing a panel, is to increase the stiffness of the panel artificially raising the first natural frequency of the panel, which corresponds to a minimum value in the STL spectrum. In this paper the influence of the air cavity's added stiffness on the panel STL is investigated in detail. As expected the effect of the sealed air is to increase the plate stiffness and as a result to increase the frequency of its first natural mode, however the effect on the STL in this frequency region is unexpectedly insignificant which removes the need for correcting STL measurements using small enclosures in low frequency range-around their first natural frequency of the panels.