Failures of bolts in helicopter main rotor drive plate assembly due to improper application of lubricant

Eliaz, Noam; Gheorghiu, George; Sheinkopf, H.; Levi, Ofer; Shemesh, G.; Ben-Mordechai, A.; Artzi, H.

doi:10.1016/s1350-6307(03)00018-9

Cited by 21 publications

(7 citation statements)

References 1 publication

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“…The axial preload is easily found, provided that the geometry of the screw and the friction coefficients in the thread and in the underhead are known. Previous research has shown that the friction coefficients have a strong impact on the performance of the threaded joints, and are in turn affected by several parameters, such as: (i) the materials in contact, [4][5][6][7][8] (ii) the wear or corrosion of the surfaces, [9][10][11] (iii) their state of lubrication, [12][13][14][15] (iv) the coating characteristics, 16 as well as (v) the tightening speed. 17 Moreover, the literature reports that a better exploitation of the screw material may be achieved, if the coefficients of friction take values within a certain interval.…”

Section: Introductionmentioning

confidence: 99%

The influence of lubrication on the frictional characteristics of threaded joints for planetary gearboxes

Agostinis

Fini

Olmi

2016

Proceedings of the Institution of Mechanical Engineers, Part C:

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Planetary gearboxes generally consist of a ring gear, or gear body, connected with the input and output flanges by means of several screws, equally spaced along the diameter. The ring gear is manufactured with steel, whereas the flanges are usually made of cast iron. These screws must provide axial preload between the parts, allowing the assembly withstanding the breakaway torque given by the difference between the output and input torque applied to the gearbox. For a given screw geometry, the axial preload can be calculated, provided that the friction coefficients in the thread and in the underhead are known. Most often, the tightening torque is the only parameter being controlled during assembly and service operations. Hence, it is mandatory to know the friction coefficients of the joint. These depend, among others, on the hardness, roughness and texture of the mating surfaces, as well as on the lubrication state of the joint. In fact, the addition of a lubricant modifies the tribological behavior of the joint, thus the wearing evolution of the surfaces across repeated tightening operations. The present work tackles the following two aspects: (i) the characterization of the preloading force–tightening torque relationship on the actual component by means of a dedicated specimen, (ii) the evaluation of the influence of lubrication on the evolution of the frictional characteristics of the joint across several re-tightening operations. The present work has been carried out by means of both numerical finite element analyses and experimental stress analysis techniques.

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Section: Introductionmentioning

confidence: 99%

The influence of lubrication on the frictional characteristics of threaded joints for planetary gearboxes

Agostinis

Fini

Olmi

2016

Proceedings of the Institution of Mechanical Engineers, Part C:

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“…Lab tests have then been performed with the aim of determining the mean friction coefficient in the screw connection and the actual preload force generated upon the ring-nut tightening. 15–19 The tightening force has been measured by an instrumented sleeve, where strain gages ( 1-LY11-1,5/120 by Hottinger Baldwin Messtechnik, HBM , Germany) were connected in a full Wheatstone bridge. Data sampling was performed by a NI C-DAQ 9184 equipped by the bridge module NI 9237 at the frequency of 10Hz.…”

Section: Methodsmentioning

confidence: 99%

A numerical and experimental approach to the design and failure analysis of a pinion shaft for wheel loaders

Croccolo

Agostinis

Fini

et al. 2018

Proceedings of the Institution of Mechanical Engineers, Part C:

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The present paper deals with the failure analysis and consequent design tips regarding a pinion shaft belonging to a differential gear for offroad machinery applications, namely wheel loaders. The motivations of the study arise from some in-field failures, which resulted in the fracture of the pinion shaft, originated at an external groove located at the end of its threaded portion. The issue has been tackled by means of analytical, numerical and experimental tools. The observed failures have been demonstrated to be due to the in-service loosening of a ring nut, whose function is to preload the tapered rolling bearings, which support the shaft. The weak points of the shaft design are highlighted and possible approaches to overcome the observed occurrence are presented at the end of the study.

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“…If some preconizations are not followed during assembly (lubrication, adjustment, maximum torque...), corrosion may appear and this even though there is a coating steel (Ni-Cr-Zn or Cd) [4]. The galling phenomenon occurs when there is a large difference in hardness between the assembled parts or when the lubrication is insufficient during the assembly [7]. Inadequate functional clearance can also foster this phenomenon by inducing very high stresses at the contact zone between the two parts.…”

Section: State Of the Artmentioning

confidence: 99%

Bolted Joints Disassembly: A Field Study for Thermal Influence on Large Diameters

Gitto

Maranzana

Segonds

et al. 2012

AMM

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is an open access repository that collects the work of Arts et Métiers ParisTech researchers and makes it freely available over the web where possible. Abstract.During maintenance operations, technicians have to work as quickly as possible. But they are often stopped during disassembly by blocked bolts or studs. This paper examines causes of blockage and suggests new method for disassembling bolted joint in this case. Several methods are analyzed and tested with finite element simulations. An experimental protocol to test a new disassembling method is also introduced in this paper.

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Failures of bolts in helicopter main rotor drive plate assembly due to improper application of lubricant

Cited by 21 publications

References 1 publication

The influence of lubrication on the frictional characteristics of threaded joints for planetary gearboxes

The influence of lubrication on the frictional characteristics of threaded joints for planetary gearboxes

A numerical and experimental approach to the design and failure analysis of a pinion shaft for wheel loaders

Bolted Joints Disassembly: A Field Study for Thermal Influence on Large Diameters

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