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Corresponding Author

Mehran Dadgar

Document Type

Article

Keywords

Torsion bar, Projectile weaving machine, Finite element analysis, Stress concentration, Tooth width

Abstract

Premature failure of torsion bars in projectile weaving machines leads to production interruptions and increased maintenance costs. Previous failure analysis identified the shoulder transition as a critical stress-concentration region and suggested that increasing bar length could reduce peak torsional stress. This study re-examines these findings using a three-dimensional finite element (FE) model that explicitly represents the tooth geometry at both ends of an industrial torsion bar. Following a mesh-independence study, a common 3 mm global mesh was used to evaluate thirteen configurations, including seven bar lengths from 785 to 845 mm and six tooth-width configurations at the loaded and mounting ends. A torque of 905.5 N· m was applied to loaded end. Across seven bar lengths, maximum von Mises stress varied from 1310.0 to 1320.9 MPa, whereas changing the loaded-end tooth width from 2.3 to 2.7 mm changed the peak stress from 1289.5 to 1405.8 MPa. In all configurations, the global maximum occurred at a tooth root at the loaded 25 mm end rather than at the shoulder transition. This location was qualitatively consistent with an available laboratory fracture observation. Because experimental torsional fatigue data were unavailable, a representative two-point S-N curve was used for screening with R = 0 loading and Goodman correction. Resulting stresses exceeded the assumed S-N range, so the calculated fatigue life was not interpreted as a physical prediction. Under the investigated torque-controlled conditions, tooth width had a greater effect on peak stress than bar length. Further fatigue assessment requires experimentally calibrated elastic-plastic and dynamic/contact analyses.

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