Delft University of Technology
Faculty Mechanical, Maritime and Materials Engineering Transport Technology
F.W.P. Smeets Conveyor Belt Splice Analysis. A Finite Element Model
Computer program, Report 2005.TL.6979, Transport Engineering and Logistics.
Conveyor belts are reinforced with cables and/or fabric to withstand the high tensile forces occurring. Since conveyor belts do not have an infinite length splicing is needed. To minimize the chance of splice failure extra strength analysis can be performed. In this report a splice analysis of the st 2400 pipe conveyor belt from Taeryuk is made using a Finite Element Method (FEM). The splice applied in this belt is a 3-step interlaced joint. The belt differs from the ISO standard by a difference in edge cable.
The belt consists of three materials. A rubber base, enforced with steel cables and two layers of fabric. Rubber is a non-linear material, especially over large deformations. The Neo-Hookean model is a linearization, and will give reasonable results at strains till 300%. Because of the windings of the cables a moment will occur when the cable is under tension. This property is referred to as the twist tension property. In this model the rotation is assumed to be small. Therefore the moment is only a function of the applied tension.
A common method to test the tensile strength of a belt is to create an H-Block. For this research first an FEM model of an H-Block is created. Three different cable arrangements with respect to the twist tension property of the steel cable are researched.
Because the testing equipment used has a limited tension range, the splice length in the H-Block is one fifth of the splice length in the Taeryuk belt. The relationship between the splice length and maximum stress is assumed to be linear. The displacement results from test done by Taeryuk are compared with the H-Block model and at lower forces they respond the same. At higher forces (3,000+ Newton) the model is a bit stiffer than the tests. Additional material research is needed to get a better match.
The maximum for a 100 mm H-Block stress is located at the end of the single cable. Although the deformed shapes for different cable options are different, the maximum stress does not differ significantly between the three models. In the force-stress diagram there is a clear non-linear trend visible. This trend can be used to estimate stresses at higher tensile forces. The strains are all within the 300% range, which validates the use of the Neo-Hookean linearization. The rotations are also within limits.
The assumption of a linear relationship between the splice length and maximum stress is tested by creating H-Blocks with larger splice lengths. For larger splices the maximum moves from the end of the single cable to the other side, the end, of the splice. This is because the elongation of the centre cable is larger than of the two other cables which results in high stresses at larger splice lengths. More research is needed to get full insight in the stress-splice length relation.
The same model properties of the H-Block model are used for creating a complete splice model. The mesh of this model is much coarser. Due to a maximum number of nodes allowed by ANSYS only a few splice sets can be modelled. Three different cable arrangements are examined. The maximum stress is located at the end of the cables for al options. The twist tension option of the steel cable does affect the deformed shape, but did not seem to affect the stress. The cables in the complete splice are subjected to the same forces and therefore no elongation differences occur.
If the 500 mm Block is compared to a 500 mm complete splice there is a clear difference due to the process of different cable elongation in the H-Block. The process is small in a 100 mm H-Block, and this H-Block did resemble the stress distribution of a 100 mm splice quite well. The maximum of the 100 mm splice did resemble the 500 mm complete splice, but the distribution was different and therefore fatigue testing could be not comparable. More practical research is needed on this subject.
Reports on Transport Engineering and Logistics (in Dutch)
