Vladis Kosse

Mechanical Properties of Pumpkin

Mechanical properties of three common varieties of pumpkin were evaluated and statistically compared. Toughness, rupture force, shear strength, and cutting force were determined for Jarrahdale, Jap, and Butternut varieties. The investigation was carried out in three cases of flesh, skin and unpeeled product, ignoring the toughness and rupture force of flesh. Relative contribution of skin to unpeeled case of each property was estimated. Varieties were found statistically alike in rupture force, toughness, and maximum shear strength force of unpeeled cases. Also the skin of three varieties showed similar strength in shear (p>0.05). Jap and Butternut varieties for some other properties showed close values. Maximum shear strength force of flesh, shear strength of unpeeled case, and relative contribution of skin to shear strength of unpeeled case were close (p>0.05) for these varieties. Jarrahdale had no difference in shear strength of flesh with two other varieties. It was also similar (p>0.05) to Jap in relative contribution of skin to shear strength, rupture force, and toughness of unpeeled case.

Mechanical Behaviours of Pumpkin Peel under Compression Test

Abstract Mechanical damages such as bruising, collision and impact during food processing stages diminish quality and quantity of productions as well as efficiency of operations. Studying mechanical characteristics of food materials will help to enhance current industrial practices. Mechanical properties of fruits and vegetables describe how these materials behave under loading in real industrial operations. Optimizing and designing more efficient equipments require accurate and precise information of tissue behaviours. FE modelling of food industrial processes is an effective method of studying interrelation of variables during mechanical operation. In this study, empirical investigation has been done on mechanical properties of pumpkin peel. The test was a part of FE modelling and simulation of mechanical peeling stage of tough skinned vegetables. The compression test has been conducted on Jap variety of pumpkin. Additionally, stress strain curve, bio-yield and toughness of pumpkin skin have been calculated. The required energy for reaching bio-yield point was 493.75, 507.71 and 451.71 N.mm for 1.25, 10 and 20 mm/min loading speed respectively. Average value of force in bio-yield point for pumpkin peel was 310 N.

Study of tissue damage during mechanical peeling of tough skinned vegetables

Peeling is an essential phase of post harvesting and processing industry; however the undesirable losses and waste rate that occur during peeling stage are always the main concern of food processing sector. There are three methods of peeling fruits and vegetables including mechanical, chemical and thermal, depending on the class and type of fruit. By comparison, the mechanical method is the most preferred; this method keeps edible portions of produce fresh and creates less damage. Obviously reducing material losses and increasing the quality of the process has a direct effect on the whole efficiency of food processing industry which needs more study on technological aspects of this industrial segment. In order to enhance the effectiveness of food industrial practices it is essential to have a clear understanding of material properties and behaviour of tissues under industrial processes. This paper presents the scheme of research that seeks to examine tissue damage of tough skinned vegetables under mechanical peeling process by developing a novel FE model of the process using explicit dynamic finite element analysis approach. In the proposed study a nonlinear model which will be capable of simulating the peeling process specifically, will be developed. It is expected that unavailable information such as cutting force, maximum shearing force, shear strength, tensile strength and rupture stress will be quantified using the new FEA model. The outcomes will be used to optimize and improve the current mechanical peeling methods of this class of vegetables and thereby enhance the overall effectiveness of processing operations. Presented paper aims to review available literature and previous works have been done in this area of research and identify current gap in modelling and simulation of food processes.

Innovative approaches to teaching engineering drawing at tertiary institutions

This paper arises from our concern for the level of teaching of engineering drawing at tertiary institutions in Australia. Little attention is paid to teaching hand-drawing and tolerancing. Teaching of engineering drawing is usually limited to computer-aided design (CAD) using AutoCAD or one of the solid-modelling packages. As a result, many engineering graduates have difficulties in understanding how views are produced in different projection angles, are unable to produce engineering drawings of professional quality, or read engineering drawings, and unable to select fits and limits or surface roughness. In the Faculty of Built Environment and Engineering at the Queensland University of Technology new approaches to teaching engineering drawing have been introduced. In this paper the results of these innovative approaches are examined through surveys and other research methods.

Development of Testing Facilities for Verification of Machine Condition Monitoring Methods for Low Speed Machinery

Machine condition monitoring (MCM) of low speed machinery is highly challenging task. Methods of MCM of machinery operating at a speed of 500 to 3000 rpm are well-developed including wear debris and vibration monitoring (both instrumentation and signal processing). Machinery operating at a speed below 500 rpm is usually grease lubricated and wear debris analysis cannot be effectively used. Monitoring of vibrations at such speed is very difficult because conventional accelerometers give very week signal especially at a speed below 100 rpm. There is a vital need to develop new approaches to monitoring fault development on low speed machinery, which include new sensors and alternative methods such as sound emission and ultrasonic emission. Essential part of this process is development of testing facilities that enable modeling of different combinations of loading conditions that take place on low speed machinery and verify new MCM methods. For this purpose a design study has been conducted to develop methods of modeling of different combinations of loads on bearings and gears operating at low speed. This study resulted in the development of a unique highly versatile test rig presented in this paper. It enables modeling of different types of bearings operating at a speed of 30 to 600 rpm under a combination of different loading conditions, in particular, steady load, impact load, swinging load, axial load and rumble. It also enables modeling of transitional processes in shaft-mounted, flange-mounted and foot-mounted gear drives under different loading conditions (start up, coast down, increase or decrease of speed). Special instrumentation enables monitoring of the supply frequency, phase current, power consumed and taking these parameters for recording.

Study of Mechanical Deformations on Tough Skinned Vegetables during Mechanical Peeling Process (A Review)

Peeling is an essential phase of post harvesting and processing industry; however undesirable processing losses are unavoidable and always have been the main concern of food processing sector. There are three methods of peeling fruits and vegetables including mechanical, chemical and thermal, depending on the class and type of fruit. By comparison, the mechanical methods are the most preferred; mechanical peeling methods do not create any harmful effects on the tissue and they keep edible portions of produce fresh. The main disadvantage of mechanical peeling is the rate of material loss and deformations. Obviously reducing material losses and increasing the quality of the process has a direct effect on the whole efficiency of food processing industry, this needs more study on technological aspects of these operations. In order to enhance the effectiveness of food industrial practices it is essential to have a clear understanding of material properties and behaviour of tissues under industrial processes. This paper presents the scheme of research that seeks to examine tissue damage of tough skinned vegetables under mechanical peeling process by developing a novel FE model of the process using explicit dynamic finite element analysis approach. A computer model of mechanical peeling process will be developed in this study to stimulate the energy consumption and stress strain interactions of cutter and tissue. The available Finite Element softwares and methods will be applied to establish the model. Improving the knowledge of interactions and involves variables in food operation particularly in peeling process is the main objectives of the proposed study. Understanding of these interrelationships will help researchers and designer of food processing equipments to develop new and more efficient technologies. Presented work intends to review available literature and previous works has been done in this area of research and identify current gap in modelling and simulation of food processes.

Design of hammer mills for optimum performance

Abstract Hammer mill manufacturers are under increasing pressure to deliver mills of high productivity with a reduced level of vibrations. However, in practice, excessive wear of the rods carrying the hammers takes place, and cracks develop in the vicinity of the holes holding the rods with the hammers, with the possibility of breakaway fracture and disastrous consequences. An increased level of vibrations has been found on many new mills. Existing design approaches have proved to be incapable of explaining this phenomenon. This paper presents a new approach to hammer mill design and enables the prevention of increased vibrations and uneven wear and, finally, provides better performance of hammer mills.

Condition Monitoring of Low-speed Bearings - a Review

Abstract Machines with operating speeds less than 600 rpm are classified as low-speed machinery. These machines are usually the most critical items in the production line, generally large and have high rotating inertias. Until recently, there has not been much interest in condition monitoring of these machines as they do not fail easily. However, if an expected failure does occur, the downtime and replacement costs can be enormous, which can lead to massive production loss. Unlike those medium- to high-speed machines, condition monitoring of low-speed machinery presents a challenge as traditional velocity and acceleration sensors are only sensitive to responses with high impact rates. The moving components of these machines that require condition monitoring are mainly bearings and gears. Due to the lack of interest until recently, there is limited literature on condition monitoring of low-speed machinery. In this review, the authors have attempted to gather together the innovative and advanced approaches on condition monitoring of low-speed machinery, with the main focus on rolling element bearing condition monitoring.

A novel testing system for a Cycloidal drive

At present, for mechanical power transmission, Cycloidal drives are most preferred - for compact, high transmission ratio speed reduction, especially for robot joints and manipulator applications. Research on drive-train dynamics of Cycloidal drives is not well-established. This paper presents a testing rig for Cycloidal drives, which would produce data for development of mathematical models and investigation of drive-train dynamics, further aiding in optimising its design.

Analysis of the Damping Properties of High-Transmission-Ratio Cycloidal Drives

Cycloidal drives are widely used in today’s industries for drives where large reduction ratios are required. Drive-train dynamics plays an important role in their design. This paper presents a new methodology for assessing damping characteristics of Cycloidal drives and compares the natural frequencies obtained from experiments and theoretical/numerical calculations using Fast-Fourier-Transforms.