Analysis of the Drive Shaft Fracture of the Conveyor Belt for Transport of Coal

The conveyor belt for slag and coal transport in the open mine pit "Kolubara" – Serbia is driven by means of two drive drums, attached on separate shafts. Each shaft is driven by two electric motors on both sides. During exploitation, the conveyor belt drive shafts are subjected to torques and transverse forces due to belt tension. The gearboxes and the bearing units on both sides of the drive drum support each shaft. A fracture of one of the drive shafts of the conveyor belt occurred at its connection point with the gearbox. The first part of the paper defines the loads relevant for shaft calculation, based on measurements in different phases of operation and the manufacturer’s data. It is followed by the FEM analysis and fatigue analysis, for the most unfavourable load case. It has been established that the critical stress value has occurred near the connection point between the shaft and the gearbox, in the fracture zone. The second part of the paper presents chemical composition and mechanical properties of material, as well as metallographic examination of fracture surface. The experimental test procedure shows that the fracture has occurred not because of an error in the material but as a consequence of the inadequate heat treatment. Superposition of two negative influences: material fatigue and inadequate heat treatment, expressed in the cross section at the point of fracture is the main case of the conveyor belt shaft fracture

Analysis of the Drive Shaft Fracture of the Conveyor Belt for Transport of Coal

The conveyor belt for slag and coal transport in the open mine pit "Kolubara" - Serbia is driven by means of two drive drums : attached on separate shafts. Each shaft is driven by two electric motors on both sides. During exploitation, the conveyor belt drive shafts are subjected to torques and transverse forces due to belt tension. The gearboxes and the bearing units on both sides of the drive drum support each shaft. A fracture of one of the drive shafts of the conveyor belt occurred at its connection point with the gearbox. The first part of the paper defines the loads relevant for shaft calculation, based on measurements in different phases of operation and the manufacturer's data. It is followed by the FEM analysis and fatigue analysis, for the most unfavourable load case. It has been established that the critical stress value has occurred near the connection point between the shaft and the gearbox, in the fracture zone. The second part of the paper presents chemical composition and mechanical properties of material, as well as metallographic examination of fracture surface. The experimental test procedure shows that the fracture has occurred not because of an error in the material but as a consequence of the inadequate heat treatment. Superposition of two negative influences: material fatigue and inadequate heat treatment, expressed in the cross section at the point of fracture is the main case of the conveyor belt shaft fracture

Schwingfestigkeit laserauftraggeschweißter legierter Stähle

Laser cladding is an established, sustainable and value-adding process. So far, merely statically loaded parts profit from its application as its impact on part properties under cyclic loads was not investigated systematically, yet. It is shown that residual stresses are the driving factor determining fatigue strength. These can neither be manipulated by process parameters nor by thermal post-processing so as to influencing fatigue strength significantly positive. Either the material combination is to be chosen so that thermal expansion of the substrate material is higher than of the coating or mechanical post-processing, i.e. by deep rolling is to be applied. Compressive residual stresses are to be induced to the interface of substrate and coating as this area is most prone to failure. Within the representative example of laser cladding of high and low alloy steel with a cobalt-based alloy higher fatigue strength could be realised as for the latter in as-cast condition

Schwingfestigkeit laserauftraggeschweißter legierter Stähle

Laser cladding is an established, sustainable and value-adding process. So far, merely statically loaded parts profit from its application as its impact on part properties under cyclic loads was not investigated systematically, yet. It is shown that residual stresses are the driving factor determining fatigue strength. These can neither be manipulated by process parameters nor by thermal post-processing so as to influencing fatigue strength significantly positive. Either the material combination is to be chosen so that thermal expansion of the substrate material is higher than of the coating or mechanical post-processing, i.e. by deep rolling is to be applied. Compressive residual stresses are to be induced to the interface of substrate and coating as this area is most prone to failure. Within the representative example of laser cladding of high and low alloy steel with a cobalt-based alloy higher fatigue strength could be realised as for the latter in as-cast condition