Andrew Guzzomi | The University of Western Australia (original) (raw)

Papers by Andrew Guzzomi

Mechanical Systems and Signal Processing, 2007

The torsional vibration of systems involving engines exhibits some phenomena not typical of vibra... more The torsional vibration of systems involving engines exhibits some phenomena not typical of vibration in general. These effects result from the geometry of the reciprocating mechanism and are revealed by detailed kinematic and dynamic analyses. Apart from the system's inertia varying with crank rotation, recent work by the authors has shown that it is also affected by piston-to-cylinder friction. In previous published work, that omitted friction, differences were observed between the measured and the predicted natural frequency function. This short paper revisits those differences and includes friction effects.

Proceedings of The Institution of Mechanical Engineers Part D-journal of Automobile Engineering, 2008

ABSTRACT In order to obtain greater accuracy in simulation, more sophisticated models are often r... more ABSTRACT In order to obtain greater accuracy in simulation, more sophisticated models are often required. When it comes to the torsional vibration of reciprocating mechanisms the effect of inertia variation is very important. It has been shown that the inclusion of this variation increases model accuracy for both single-cylinder and multi-cylinder engine torsional vibration predictions. Recent work by the present authors has revealed that piston-to-cylinder friction may modify an engine's ‘apparent’ inertia function. Kinematic analysis also shows that the piston side force and the dynamic piston-to-cylinder friction are interdependent. This has implications for engine vibration modelling. Most modern engines employ a gudgeon pin offset, and there is a growing interest in pursuing large crank offsets; hence, the effect of these on inertia variation is also of interest. This paper presents the derivation of the inertia function for a single engine mechanism, including both piston-to-cylinder friction and crank or gudgeon pin offset, and investigates the effect of each through predictions. The effect of crank offset on the variable inertia function is also verified by experiment.

Proceedings of The Institution of Mechanical Engineers Part K-journal of Multi-body Dynamics, 2007

ABSTRACT When developing vibration models, so as to reduce model complexity, it is typically expe... more ABSTRACT When developing vibration models, so as to reduce model complexity, it is typically expected that good prediction accuracy can be achieved by ignoring the complication of friction. In this paper, the significance of friction between the piston and cylinder on engine block dynamics is shown through simulation in both the time and frequency domains. Simulations and experiments indicate that large differences exist between model predictions for the engine block moment if this friction is not accounted for. This is especially true at low crankshaft rotational speeds when dynamic inertia effects are small. Experiments on a motored single cylinder engine at different average rotational speeds confirm the theory and very good tie-up with predictions is obtained. It is expected that these findings will also have implications for the torsional vibration of the engine.

The area of powertrain dynamics has received considerable attention over a number of years. The r... more The area of powertrain dynamics has received considerable attention over a number of years. The recent introduction of more stringent emission requirements together with economic pressure has led to a particular focus on increasing powertrain efficiency. This has seen ...

Proceedings of the Conference on Multi-body …, 2004

New trends in Mechanism and Machine Science 2013

Mechanism and Machine Theory, 2012

In this paper engineering drawing techniques are examined with a particular focus on the use of t... more In this paper engineering drawing techniques are examined with a particular focus on the use of the modulus concept in design. Modulus concept here means a unit of measure based on experience and relation to key attributes from which all the design corresponds. ...

Biosystems Engineering, 2012

Biosystems Engineering, 2010

Forestry and agricultural tractors are required to have roll-over protective structures (ROPS) fo... more Forestry and agricultural tractors are required to have roll-over protective structures (ROPS) for use on European roads. To that end, the ROPS must conform to a series of strength tests in accordance with the Organisation for Economic and Co-operation Development (OECD) Standard Codes or the relevant European Community (EC) Directives. Within these Codes, ROPS force and energy absorption test requirements are typically defined in terms of a ‘reference mass’. This mass, along with mass values for ‘unladen’, ‘ballast’, and ‘maximum laden’, required for the homologation documentation, is given by the tractor manufacturer. Recent international interest in operator safety has questioned the appropriateness of the mass definitions and specifically the use of the currently defined reference mass as the basis for ROPS testing. In this work, mass information pertaining to 24 wheeled type tractors was considered: 13 were T1 (Standard) type and 11 were T2 (Narrow track) type. Although tractors may have similar reference mass values (and hence ROPS testing requirements) it was found that their ballast and maximum laden masses can differ greatly. The average ratios to reference mass values were for ballast and maximum laden values 1.13 and 1.60 for T1 tractors and 1.12 and 1.64 for T2 tractors. Both tractor categories had some ratios with values greater than 1.80. This implies safety margins determined by reference mass vary depending on the tractor under consideration. The results highlight some criticisms of ROPS testing procedures and these are discussed.

Biosystems Engineering, 2009

Because in some applications the potential exists for tractors to rollover, to reduce the danger ... more Because in some applications the potential exists for tractors to rollover, to reduce the danger to the driver Roll-Over Protective Structures (ROPS) and their corresponding international testing procedures were introduced some time ago. However, some fatalities and serious injuries resulting from rollover accidents still occur. This has led to continuing interest in gaining further understanding of the parameters influencing rollover. The different initial conditions for rollover were analysed and the energy available at the start of rollover evaluated. In particular, the theoretical difference in available energy for lateral rollover on different planes, together with the inclusion of forward velocity, was analysed. Data pertaining to 102 narrow-track tractors fitted with front ROPS, with masses in the range 780–2380 kg were used to calculate the available energy. The results support the hypothesis that there is a non-linear relationship between tractor mass and available energy.

International Conference on …, 2010

Proceedings of The Institution of Mechanical Engineers Part D-journal of Automobile Engineering, 2010

ABSTRACT Torsional vibration modelling of powertrains is hindered by the lack of understanding of... more ABSTRACT Torsional vibration modelling of powertrains is hindered by the lack of understanding of tyre low-frequency torsional stiffness and damping characteristics. Torsional here means rotation about the wheel (spin) axis so that the rotation of the wheel hub is different from that of the periphery of the tyre. This paper explains a simple, practical test rig design that can be used to determine a tyre's torsional characteristics via simple modelling. The model assumes a complex stiffness that allows the damping type to be determined as a function of the frequency. The measurement of some torsional stiffness and damping characteristics of a small pneumatic tyre while under load and rolling is presented. The tyre was excited torsionally and, from the results obtained, the tyre's torsional stiffness and damping characteristics were calculated. The investigations were concerned with the low-frequency characteristics. It was found that there was a large torsional vibration associated with the tread pattern. Over the frequency range tested (10–50Hz), it was found that the damping is more accurately represented as hysteretic and not viscous when lightly loaded. The effects of rotational speed, preload, and inflation pressure on the stiffness and damping were also investigated. The damping type for the tyre (hysteretic or viscous) was found to vary depending on the loading and excitation. Tyre properties were then included in a lumped-inertia, frequency-domain powertrain model and the steady-state response predicted. The results indicated that the viscous or hysteretic damping assumption has significant effects on the predicted frequency response of the powertrain. The need for further studies investigating the damping characteristics of automotive tyres in torsion is therefore recommended.

Sommario La natura del carico nella biella automobilistica e le forti concentrazioni di sforzi re... more Sommario La natura del carico nella biella automobilistica e le forti concentrazioni di sforzi rendono quest'organo di macchina particolarmente esposto a rotture per fatica. Varie forme sono state proposte ma spesso le nuove ricerche si rivolgono a migliorare forme esistenti e non vengono rivisitate vecchie soluzioni. Ciò può essere dovuto al fatto che i potenti mezzi di ricerca bibliografica ora impiegati non contengono ancora una completa panoramica storica di quanto scritto sull'argomento. Una analisi su di un vecchio testo mostra una soluzione costruttiva nella quale si evita di dividere la biella in corrispondenza di una sezione diametrale dell' "occhio grande". Questo montaggio evita la necessità di ricorrere a viti per mantenere il giunto chiuso. Il presente lavoro rivisita una soluzione costruttiva che prevede un inserimento laterale del cappello e sistemi di precarico per eliminare il gioco fra le parti. I vantaggi e gli svantaggi della soluzione vengono confrontati con le soluzioni correnti. Abstract The nature of loads experienced by an automotive connecting rod during operation together with stress concentrations make these elements particularly susceptible to fatigue. Many design alternatives have been suggested and as is often the case with research and development very old solutions are not revisited. This is possibly due to the fact that the most common and readily accessible modes of finding texts, for example electronic databases, do not contain full historical lists of all published manuscripts. An analysis of an old text, reported in this paper, gives a constructive solution in which there is no need to split the connecting rod at the minimum cross-section in order to mount it on the crankshaft. This mounting technique removes the need for bolts or screws to maintain the joint closed. This paper revists that proposed solution which proposes that the end-cap be inserted laterally. The advantages and disadvantages of such a solution are also reported. Parole chiave: bielle automobilistica, cappello, viti, precarico, motore a scoppio, FEA