Research in Agricultural Engineering, 2006 (vol. 52), issue 3

Impact induced mechanical damage of Agria potato tubers cultivated in different regimes

J. Blahovec, A. Hejlová, J. Vacek

Res. Agr. Eng., 2006, 52(3):81-86 | DOI: 10.17221/4883-RAE  

The Agria potato tubers were grown in 2005 in cultivation regimes involving different irrigation and fertilisation levels and forms. The impact induced tuber damage was simulated dynamically by an impact pendulum test and studied with the aim to detect some relationship between the cultivation regimes and the type and extent of the damage. The usual bruising presented as black spots is in many cases masked by other mechanisms of damage, e.g. by tuber cracking and/or crushing. The highest degree of tuber cracking and at the same time the least frequent bruising were observed for tubers cultivated in the regime with irrigation and without fertilising....

The plane interaction theory of the cleaning vane with the head of a root crop

V. Bulgakov, I. Holovach, M. Berezovyy

Res. Agr. Eng., 2006, 52(3):87-96 | DOI: 10.17221/4884-RAE  

New interaction theory of a flexible cleaning vane with the head surface of root crop in the case when the vane installed on the driving shaft makes a plane motion is proposed. Based on the obtained differential equations of the vane motion some new mathematical dependencies, describing the basic parameters of this interaction are given.

One-parameter model of sterilisation process. Heating and cooling period

M. Loučka, P. Veselý, F. Jaroš, J. Pavlík

Res. Agr. Eng., 2006, 52(3):97-106 | DOI: 10.17221/4885-RAE  

The article deals with the simplification of the heat transfer model for food sterilisation in cans and jars. The one-parameter model was derived and identification procedures of its parameters were examined. It is shown that the concept of the first order dynamics satisfies the technological purposes but the common method of the least squares is not suitable for the calculation of model constants. A new computing method is presented and compared with statistically evaluated experiments with wide range of stuffs and packages.

Exploitation of Hertz's contact pressures in friction drives

D. Herák, R. Chotěborský, A. Sedláček, E. Janča

Res. Agr. Eng., 2006, 52(3):107-113 | DOI: 10.17221/4886-RAE  

The paper is intent on the applications of equations which describe the Hertz's surface pressures in friction drives. In the paper the reduced equations are derived, which are useful to the surface pressures calculation in friction drives when ball - ball, cylinder - cylinder, cone - cone are kept in touch and their graphical representation of stress distribution in the contact area is presented. Using the Hertz's surface pressures and the Mohr's circles the substance of pitting start is derived and the stress distributions using the elementary joists, which were situated on the axe z in the section under the contact joist, are represented.

Influence of overlay layers on the abrasive wear

P. Hrabě, R. Chotěborský, R. Medlín

Res. Agr. Eng., 2006, 52(3):115-122 | DOI: 10.17221/4887-RAE  

A problem of machine parts wear decrease and in this way of the economical effectiveness of rapid wearable parts interferes with majority of manufacturing processes. Service life and operating reliability of a great number of machine parts is largely influenced by friction and wear, which take a significant part in the power and material losses. Wear affects significantly the maintenance, repair and renewal costs of machine parts, too. Today we can use a row of overlay materials. They differ above all by chemical composition, which determinates the conditions of use. Next conditions are the solidification of the welded-on material and the diffusion...