TY - THES

T1 - Comparison of evaluation methods regarding the tooth root stress for spur and helical gears in pulsator tests

AU - Fiedler, Florian

N1 - embargoed until 11-05-2023

PY - 2021

Y1 - 2021

N2 - Gears are among the most important and widely used machine elements. For their use in gearboxes and machine components, long service life and reliability are essential requirements. For this reason, the determination of the appearing stresses and forces and the subsequent operationally stable design is of substantial importance. In addition to flank fatigue, tooth root stress has a decisive influence on the service life of gear wheels. Increased stresses can lead to crack propagation and breakage of a tooth and thus destroy the entire machine component. In this thesis, different evaluation methods for the tooth root stress, both for spur and helical gears, are performed and then compared. The methods are divided into analytical, numerical and experimental approaches. For the analytical approach, a calculation scheme is set up according to ISO 6336-3 to ascertain the critical stress. Using a FE simulation, the stress ratios in the tooth root of the gears are then determined at different load levels. For the experimental test, a gear holder is first constructed for the test gears. Static and cyclic tests are performed on the test rig and the occurring stresses are measured using previously attached strain gauges. The findings of the individual methods are then evaluated and presented. For this purpose, the respective results of the load levels are compared with each other and the correlation between applied load and occurring tooth root stress is examined. The comparison between the analytical values according to ISO 6336-3 and the FE simulation shows a satisfactory agreement for three tested load levels. Thus, a maximum deviation of 4% was achieved for the spur gears and a maximum deviation of 8% for the helical gears. A directly proportional relationship between load and tooth root stress was also found. The comparison between the values of the FE simulation and the results of the strain measurement tests also showed a satisfactory agreement for the examined load levels for both gear types. A maximum deviation of 8% was achieved for the spur gearing and a maximum deviation of 4% for the helical gearing at the respective load levels. Through these comparisons, it was found that the stresses are almost identical for the different evaluation methods. This observation validates the performance of the pulsator tests for the two gear types.

AB - Gears are among the most important and widely used machine elements. For their use in gearboxes and machine components, long service life and reliability are essential requirements. For this reason, the determination of the appearing stresses and forces and the subsequent operationally stable design is of substantial importance. In addition to flank fatigue, tooth root stress has a decisive influence on the service life of gear wheels. Increased stresses can lead to crack propagation and breakage of a tooth and thus destroy the entire machine component. In this thesis, different evaluation methods for the tooth root stress, both for spur and helical gears, are performed and then compared. The methods are divided into analytical, numerical and experimental approaches. For the analytical approach, a calculation scheme is set up according to ISO 6336-3 to ascertain the critical stress. Using a FE simulation, the stress ratios in the tooth root of the gears are then determined at different load levels. For the experimental test, a gear holder is first constructed for the test gears. Static and cyclic tests are performed on the test rig and the occurring stresses are measured using previously attached strain gauges. The findings of the individual methods are then evaluated and presented. For this purpose, the respective results of the load levels are compared with each other and the correlation between applied load and occurring tooth root stress is examined. The comparison between the analytical values according to ISO 6336-3 and the FE simulation shows a satisfactory agreement for three tested load levels. Thus, a maximum deviation of 4% was achieved for the spur gears and a maximum deviation of 8% for the helical gears. A directly proportional relationship between load and tooth root stress was also found. The comparison between the values of the FE simulation and the results of the strain measurement tests also showed a satisfactory agreement for the examined load levels for both gear types. A maximum deviation of 8% was achieved for the spur gearing and a maximum deviation of 4% for the helical gearing at the respective load levels. Through these comparisons, it was found that the stresses are almost identical for the different evaluation methods. This observation validates the performance of the pulsator tests for the two gear types.

KW - Zahnfußspannung

KW - Pulsatortest

KW - Tooth root stress

KW - Pulsator rig

M3 - Master's Thesis

ER -