MA Gen,ZHONG Jiru,GUAN Kaishu. Failure analysis of input shaft gear of plastic extruder[J]. Journal of Mechanical Transmission,2026,50(3):187-192.DOI: 10.16578/j.issn.1004.2539.2026.03.021.
Failure analysis of input shaft gear of plastic extruder
Aiming at the multi-tooth fracture problem of the high-speed clutch gear on the input shaft of a certain type of plastic extruder
the failure mechanism was explored
the fracture cause was clarified
and a basis was provided for gear structure improvement and service life enhancement.
Methods
2
Firstly
through macroscopic fracture morphology analysis and scanning electron microscope (SEM) characterization
the fatigue steps
fatigue striations on the fracture
and plastic extrusion/slip marks on the tooth surface were observed
and the failure mode was initially determined. Secondly
chemical composition detection and hardness testing were carried out to verify the compliance of the gear material composition
and the hardness of the tooth surface and core was tested to determine whether surface strengthening treatment had been performed. Then
the finite element method was used to establish a gear pair model
and three working conditions (normal fit
non-parallel centerlines
and misaligned centerlines) were simulated to analyze the stress distribution law of the tooth root
with emphasis on quantifying the influence of centerline misalignment on the tooth root stress amplitude. Finally
the bending stiffness check of the shafting was conducted
and the influence of insufficient shaft stiffness on the alignment of the gear pair centerlines was verified by calculating the equivalent diameter
moment of inertia of the shaft
and deflection at the gear.
Results
2
The gear failure mode is fatigue fracture
with obvious fatigue striations and fatigue source areas visible on the fracture. Insufficient bending stiffness of the shaft causes the shaft deflection at the gear to exceed the allowable deflection
leading to misalignment of the gear pair centerlines. When the displacement in the
Y
direction of the translational degree-of-freedom is 0.01 mm
the stress amplitudes at the tooth roots of the internal and external gears reache 62.66 MPa and 62.72 MPa respectively
which accelerate the initiation and propagation of fatigue cracks. No strengthening treatment such as carburizing is performed on the gear surface
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