Evaluation of stress risers severity in spur gears meshing

Abstract Increasing age expectations and number of joint replacement procedures have made interprosthetic femoral fractures (IFF) a progressively more common diagnosis and a challenge for surgeons. A gold standard and universally accepted classifications and guidelines do not exist yet. Customized structured electronic searches performed in PubMed database. Relevant key terms: IFF, classification interprosthetic fracture, peri-implant femoral fracture, biomechanics interprosthetic femur fracture, radiographic femur fracture, risk factor IFF. 42 articles finally included (up to 2019). High morbidity and mortality linked to IFF. Standardised classifications, management guidelines and surgical approaches are not available yet. Periprosthetic classification systems are still utilized even if not entirely appropriate. High rate of failure is related to thinner cortical bone, larger medullary canals and variable stresses depending on the distance among implants. High complication rates in all studies. Stress risers and implant stability based on fracture patterns and stress forces. Several surgical options with no uniformity. Less invasive surgical procedures are associated to reduction of metalwork failure rate, better preservation of vascularization and better functional-clinical outcomes. Lack of specific classification systems and management guidelines. Several surgical options are available with no uniformity of results. Attention to stress risers and preservation of bone stock and vascularization are key aspects for better results.

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Analysis of the Welding Type and Filler Metal Influence on Performance of a Regenerated Gear

Materials ◽

10.3390/ma14061496 ◽

2021 ◽

Vol 14 (6) ◽

pp. 1496

Author(s):

Svetislav Marković ◽

Dušan Arsić ◽

Ružica R. Nikolić ◽

Vukić Lazić ◽

Nada Ratković ◽

...

Keyword(s):

Heat Treatment ◽

Service Life ◽

Economic Analysis ◽

Filler Metal ◽

Performance Characteristics ◽

Experimental Investigations ◽

Spur Gears ◽

Soft Filler ◽

Welding Procedure

This paper presents the results of voluminous experimental investigations conducted to analyze the influence of the welding procedure on the performance of regenerated gears. Cylindrical spur gears were tested, both newly manufactured and regenerated, in two fundamentally different ways: by hard facing (surfacing) with the “hard” filler metal (DUR 600-IG) and with the “soft” filler metal (EVB2CrMo) with subsequent cementation and quenching. The regeneration procedures were defined and executed, while, subsequently, the microstructure and microhardness of the hard-faced layers were established and measured, followed by checking the durability of the hard-faced teeth flanks. Finally, techno-economic analysis was performed to establish the rationality of the conducted regenerations, i.e., the costs of regenerated and newly manufactured teeth were compared. Based on the results of the conducted investigations, it was possible to establish the influence of the welding type on the performance characteristics (primarily the service life) of the regenerated gears. For individual reparatory hard facing, the procedure with the “hard” filler metal exhibited better characteristics, while for batch reparation of numerous damaged gears, the reparation with the “soft” filler metal, followed by cementation and heat treatment, might be more convenient.

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