Contact Analysis of Dovetail Joint of Compressor Disc for

Fretting Fatigue

SUNITA KUMARI

M.TECH. - PDM

Under The Guidance OfP V SRIHARI

Associate Professor, RVCE

• Introduction• Literature Review• Objectives and Methodology• Geometrical modeling of dovetail

joints• Finite element modeling of dovetail

joints• Results and Discussion• Conclusions • References

Agenda

A special wear process that occurs at the contact area between two materials under load & subject to minute relative motion by vibration or some other forces .

Fretting is caused relative motion between two surfaces in contact with small amplitude (typically 1-100 μm) oscillatory Factors which influenced the fretting fatigue most are a) Temperature ,b) Material in contact, c) Cyclic frequency, d) Environmental condition, e) Contact surfaces, f) Coefficient of friction, g) Hardness of material, h) Contact pressure

Fretting Fatigue

Effect Of Fretting •Fretting is a dangerous situation, which often causes seizure, vibration, wear and fracture of the systems. •Fretting fatigue reduces the strength of the material as well as the quality of the contact surfaces which further degrade the fatigue strength & endurance limit of the surface by half or one third

One of the most common occurrences of fretting in an aircraft turbine engine is in the compressor section at the blade/disk interface. The combination of the rotating disk

and the airflow through the engine imposes centrifugal forces and circumferential oscillations on the blades.

This causes low amplitude cyclic stresses in the material. The combination of the cyclic stresses and fretting surface interactions promotes surface crack initiation and growth, which is often called fretting fatigue.

Fretting in Dovetail Joint

Authors and Published year

Paper Title Observation

Papanikos P, Meguid SA, and Stjepanovic Z

1998

Three dimensional nonlinear finite element analysis of dovetail joints in aero engines disc

Understanding the effect of critical geometricalfeatures, such as flank angle, fillet radii and skew angle upon the resulting stress field.

B.M. Gowda , H.R. Yeshovanth, C. Siddaraju

(2014)

Investigation and Efficient Modeling of an Dovetail Attachment in Aero-engine

Variation of stress and deformation at different speed

Anandavel K, and Raghu V. Prakash

2011

Effect of three-dimensional loading on macroscopic fretting aspects of an aero-engine blade–disc dovetail interface

Conclusions drawn are at as the COF goes on increasing the stresses and FFparameters goes on decreasing.

Tiago de Oliveira Vale, Gustavo da Costa Villar, and Joao Carlos Menezes

2012

Methodology for structural integrity analysis of gas turbine blades

The stress distribution results are compared with the literatures and found the results are matched with the literature.

Literature Survey Literature Survey

3D modeling and simulation of disk blade using ANSYS & CATIATo evaluate the primary fretting fatigue parameters of an aero-engine dovetail blade disc joints by finite element simulation methods.Investigating the fretting fatigue parameters for different geometrical models.To analyzing the model with minimum stress value

ObjectivesObjectives

Identify Literature gapProject ObjectiveSolid modelingFinite Element AnalysisResultValidationConclusion

MethodologyMethodology

In this work there are different dovetail models are utilized with different flank length and angleThese models are designed in CATIA V5R19 modeling software package, with the detailed dimensions as taken from the literature.

Geometrical modellingGeometrical modelling

2D Drafting views of straight dovetail model

Geometrical modellingGeometrical modelling

In aero engines the blades are just press fitted to the disc slot no external fastenings are made and the blade flank length and the disc flank lengths are in contact. So in this study particular non-linear contact analysis is carried out.ANSYS Workbench software tool is used to carryout the finite element analysis of dovetail joints.

Finite Element AnalysisFinite Element Analysis

Material SelectionThe material selected is Titanium alloy (Ti-6Al-4V)The Ti-6Al-4V alloy offers the best all-round performance for a variety of weight reduction applications in aerospace, automotive and marine equipments.

Component Wt.%

Al 6

Fe Max 0.25

O Max 0.2

Ti 90

V 4

Material Properties

Young’s modulus 114 Gpa

Poisson’s ratio 0.33

Density 4429 kg/m3

Tensile yield strength 930 Mpa

Tensile ultimate strength 1070 Mpa

Element TypeIn ANSYS the imported 3D model was selected as SOLID 187 element. SOLID187 element is a higher order 3-D, 10-node element.

Contact Pair GenerationIn this study surface to surface contact has created. These contact elements use a "target surface" and a "contact surface" to form a contact pair.

Figure 4. Contact pair generation.

The blade surface is modeled as contact surface with element CONTA174. The disc surface is modeled with the target element TARGE170

Mesh GenerationThe model is meshed with tetrahedron meshing with mesh size 5mm for full bodyIn order obtain accurate results near the contact regions a refinement of 1mm has been done.For 40mm thickness straight dovetail model the number of nodes created are 99,394 and the number of elements created are 60,502.

Boundary Conditions.

•Rotational velocity of 10000 rpm.•Blade mass inertia due to centrifugal force has been taken as 36000N•Normal displacement of side faces has constraint to zero.•Frictionless support at inner face of the disc to provide axis of rotation.•Bending & thermal stresses has not been considered.•Effect of vibration has not been considered.

• Different model with variation in flank angle (64°,66°,68°,70°) and COF (coefficient of friction) (0.1,0.15,0.2,0.25,0.3) has been modeled and Variation in Max Von-mises stress, Max deformation, Contact pressure & sliding distance has been analyzed

• Model with varying flank length (13,12,11,9mm) has been modeled and Variation in Max Von-mises stress, Max deformation, Contact pressure & sliding distance has been analyzed with different COF

Results and DiscussionResults and Discussion

Von-mises stresses for different flank angle and COF

Von mises stress for different flank angle & length with varying COF (coefficient of friction) has been analysed and plotted

Von-mises stresses for different flank length and COF

Von-mises stress 40mm straight dovetail at 0.25 COF

Max deformation for different flank angle & length with varying COF (coefficient of friction) has been analysed and plotted

Max deformation for different flank angle and COF

Max deformation for different flank length and COF

Max deformation 40mm straight dovetail at 0.25 COF

Sliding distance for different flank angle & length with varying COF (coefficient of friction) has been analysed and plotted

sliding distance for different flank length and COF

sliding distance for different flank angle and COF

Sliding distance variation in 40mm straight dovetail at 0.25 COF

Contact pressure for different flank angle & length with varying COF (coefficient of friction) has been analysed and plotted

contact pressure for different flank angle and COF

contact pressure for different flank length and COF

Contact pressure generated for straight dovetail blade of 0.25 COF

• There is 5% and 11% decrease in Max equivalent stress and max deformation respectively with the change in flank angle from 70° to 64° at coefficient of friction value 0.25.Variation is maximum at the COF value of 0.1

• There is 9% and 11% decrease in max equivalent stress and max deformation respectively with the change in flank length from 9 to 13 mm at coefficient of friction value 0.25.

• There is 19% and 20% decrease in contact pressure and sliding distance respectively with the change in flank angle from 70° to 64° at coefficient of friction value 0.25.Variation is maximum at the COF value of 0.1

• There is 19% and 15% decrease in contact pressure and sliding distance respectively with the change in flank length from 9 to 13 mm at coefficient of friction value 0.25.

• .

CONCLUSIONSCONCLUSIONS

[[1]P. Papanikos, SA. Meguid, Z. Stjepanovic, Three dimensional nonlinear finite element analysis of dovetail joints in aero engines disc, Finite Elements in Analysis and Design. 29 (1998) 173-186.

[2]Tiago de Oliveira Vale, Gustavo da Costa Villar, Joao Carlos Menezes, Methodology for structural integrity analysis of gas turbine blades, Journal of Aerospace Technology and Management. 4 (2012) 51-59.

[3]B.M. Gowda , H.R. Yeshovanth, C. Siddaraju , Investigation and Efficient Modeling of an Dovetail Attachment in Aero-engine, Procedia Materials Science. 5 ( 2014 ) 1873 – 1879.

[4]V. Chandrasekaran, L.R.G. Ledesma, Young-In Yoon, A.M.H. Taylor, D.W. Hoeppner, Evaluation and quantification of fretting damage and Corrosion pit morphology using the confocal microscope.1-22.

REFERENCESREFERENCES

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• [6]M. M. I. Hammouda,A. S. Fayed, Numerical approach to the mechanics of disc-blade dovetail joints in aero-engine compressors.

• [7]Dianyin Hu, Rongiqao Wang, Crack Growth Life Assessment on Turbine Component under Combined Fatigue Loading, 13th International Conference on Fracture.16–21 (2013).

• [8]D. Qiuwan, M. Jiaobin, Q. Jing, D. Zhang, Research on optimization for the mushroom-shaped root-rim structure of turbine blades, 5th International Conference on Civil Engineering and Transportation. (2015) 1921-1924.

• [9]K. Anandavel, R.V. Prakash, D. Antonio, Effect of Preloading on the Contact Stress distribution of a Dovetail Interface, International Journal of Mechanical, Aerospace, Industrial, Mechatronic and Manufacturing Engineering. 4-10 (2010) 1107-1112.

• [10]M. Kotresh, P.V. Srihari, K. Ramachandra, Fretting fatigue studies of aero engine dovetail roots using contact analysis, International conference on Computer Aided Engineering CAE, (2013) 93-98

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