PSI - Issue 14

ScienceDirect Available online at www.sciencedirect.com ScienceDirect Available online at www.sciencedirect.com ScienceDirect Structural Integrity Procedia 00 (2018) 000–000 Available online at www.sciencedirect.com Procedia Structural Integrity 14 (2019) 922–929 Structural Integrity Procedia 00 (2018) 000–000

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2 nd International Conference on Structural Integrity and Exhibition 2018 Fatigue Life Benefits of Cold Worked Holes in Fastener Joints L. Chikmath*, M.N. Ramanath* and B. Dattaguru* Department of Aerospace Engineering, Jain University, Jain Global Campus, Kanakapura Road, Jakkasandra Post, Ramansgara Dist, Bengaluru-562112, India Abstract Lug joints with fasteners play a vital role in connecting major components of flight vehicles by acting as primary load carrying members. The structural integrity of these fastener joints and in particular fatigue life is of prime concern from the design point of view. Cold working of holes is one of the methods of achieving enhancement of fatigue life of these joints and this aspect is computationally addressed in this paper. The process of cold working is modeled, consists of introduction of a large diameter mandrill into the hole and withdrawing it leaving behind plastically stretched material around the hole periphery. Later one can use this hole with interference or clearance fit pins for better fatigue life. Material non-linear analysis is employed during the cold working process. These issues are addressed in this paper through computational approach using FEM software MSC NASTRAN/PATRAN. The fatigue life is computed at the identified critical locations through stress analysis using modified Basquin's equation with Morrow's mean stress effect. Life of the lug joints before and after cold working of the hole are estimated and compared. 2 nd International Conference on Structural Integrity and Exhibition 2018 Fatigue Life Be efits of Cold Worked Holes in Fastener Joints L. Chikmath*, M.N. Ramanath* and B. Dattaguru* Department of Aerospace Engineering, Jain University, Jain Global Campus, Kanakapura Road, Jakkasandra Post, Ramansgara Dist, Bengaluru-562112, India Abstract Lug joints with fasteners play a vital role in connecting major components of flight vehicles by acting as primary load carrying members. The structural integrity of these fastener joints and in particular fatigue life is of prime concern from the design point of view. Cold working of holes is one of the methods of achieving enhancement of fatigue life of these joints and this aspect is computationally addressed in this paper. The process of cold working is modeled, consists of introduction of a large diameter mandrill into the hole and withdrawing it leaving behind plastically stretched material around the hole periphery. Later one can use this hole with interference or clearance fit pins for better fatigue life. Material non-linear analysis is employed during the cold working process. These issues are addressed in this paper through computational approach using FEM software MSC NASTRAN/PATRAN. The fatigue life is computed at the identified critical locations through stress analysis using modified Basquin's equation with Morrow's mean stress effect. Life of the lug joints before and after cold working of the hole are estimated and compared. Keywords: Cold working; Fastener joints, Fatigue life © 2019 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0/) Selection and peer-review under responsibility of Peer-review under responsibility of the SICE 2018 organizers.

Nomenclatures Nomenclatures

Width of the lug � Fatigue strength coefficient Push fit angle Separation angle Misfit parameter Cold working parameter Poisson's ratio Friction coefficient Stress Alternating stress Width of the lug � Fatigue strength coefficient Push fit angle Separation angle Misfit parameter Cold working parameter Poisson's ratio Friction coefficient Stress Alternating stress

Keywords: Cold working; Fastener joints, Fatigue life

Fatigue strength exponent

Regions of contact

Fatigue strength exponent Young’s modulus of the lug Young’s modulus of the pin Regions of contact Stress Concentration Factor (SCF) Young’s modulus of the lug Young’s modulus of the pin Length of the lug Crack initiation life Stress Concentration Factor (SCF) Pin load

Length of the lug Crack initiation life Stress ratio Inner radius f the lug

Pin load Stress ratio

Inner radius of the lug

* Corresponding author. Tel.: +91 80 27577231; fax: +91 80 27577233. E-mail address: lokamanyachikmath@gmail.com

2452-3216  2019 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0/) Selection and peer-review under responsibility of Peer-review under responsibility of the SICE 2018 organizers. 10.1016/j.prostr.2019.07.072 2452-3216© 2018 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0/) Selectio and peer-review der r sponsibility of Peer-review under responsibility of the SICE 2018 organizers. 2452-3216© 2018 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0/) Selection and peer-review under responsibility of Peer-review under responsibility of the SICE 2018 organizers. * Corresponding author. Tel.: +91 80 27577231; fax: +91 80 27577233. E-mail address: lokamanyachikmath@gmail.com