1、09FTM16AGMA Technical PaperAllowable ContactStresses in JackingGear Units Used in theOffshore Industryby A.N. Montestruc, Friede N is the number of cycles a typical gear toothwill see. That value should be in the range400 to 100,000 at most.For larger numbers of cycles the allowable contactstresses
2、are well established by others. The expo-nent is taken from Figure 17 of AGMA 2001-C95which shows the formula for “ZN” the pittingresistance stress cycle factor. The factor of 1.40fallsoutsuchthatAwillequalBratN=400. Thisisused due to the lack of any well documentedexperimental data.The user is caut
3、ioned that use of this relation insteelswithlowductility(lessthan14%elongation)is not advised as significant plastic deformation ofthe gear tooth surface takes place which will resultin work hardening of the surface, this is acceptableinthisapplication,ifthematerialwasductileenoughtostartout. Howeve
4、rif not,very rapidwear islikely.ConclusionsIn the design of gears for very slow speedapplications, where the number of cyclesis alsofarbelow what is considered normal for gear systemdesign, it is possible to build gear systems that willwork satisfactorily at contact stresses far abovewhat are publis
5、hed by AGMA when using relativelysoft through hardened steel for gears for hundredsto tens of thousands of cycles.The Brinell/Plastic Deformation stress, and theproposedallowablestressdiscussedinthispaperisa useful guide to indicate what contact stresses tostay belowinrollingloadcasesfor jackingsyst
6、ems,and like applications.Experimental work is called for in development of abetter more reliable guide to the limits of contactstresses especially as regards through hardenedsteels.AcknowledgementThis paper would not have been possible withoutthe cooperation and active assistance of themanagement a
7、nd employees of Energy ServicesInternational, Inc., of 1644 Coteau Road, HoumaLouisiana, 70364.References1. ANSI/AGMA 2001-C95, Fundamental RatingFactors and Calculation Methods for InvoluteSpur and Helical Gear Teeth2. TheHardnessofMetals,D.Tabor, 1951OxfordUniversity Press Inc., New York.Table 2.M
8、esh #Pinion ratioactual/BrinellstressGear ratioactual/BrinellstressPinion ratioactual/allstressGear ratioactual/allstressPinion lifetimejacking cyclesGear lifetimejacking cycles1 0.823 0.948 1.205 1.338 4114 4002 0.552 0.577 0.865 0.896 20,571 41143 0.542 0.488 0.805 0.742 92,571 20,5714 0.476 0.495 0.696 0.716 413,849 92,571.43
