The loads induced during transport can be the highest to which an implement frame or tractor linkage is subjected. Modelling such loads requires consideration of non-linearities such as free play in the joints between the tractor and the implement. An approach has been developed, using the dynamic analysis package ADAMS, that is capable of dealing with such non-linearities. The model consists of representations of the physical parts of the vehicle, connected by joints and forces. Tyres may be modelled using standard software elements (e.g. linear springs and dampers) or mathematical expressions to calculate tyre forces. The ground input may be supplied from a data file or by using standard excitation functions and any tyre enveloping function may be applied. Using the most recent data available for the dynamic properties of the tyres in the vertical direction, comparisons have been made between predictions and measurements of loads at the three point linkage for a tractor and plough travelling along a farm roadway. The results showed that vibration frequencies were quite well modelled and that improvements in the load amplitude predictions would require stiffness and damping data for the tyres in the horizontal plane.
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