Experimental Mechanics

, Volume 22, Issue 1, pp 8–15

Photoelastic studies on progress of separation in interference fits

A photoelastic method is presented for studying the progress of separation in interference fits by identifying the break in electric circuit between metallic pin and a series of wires laid on CR-39 sheet
  • S. P. Ghosh
  • B. Dattaguru
  • A. K. Rao

DOI: 10.1007/BF02325696

Cite this article as:
Ghosh, S.P., Dattaguru, B. & Rao, A.K. Experimental Mechanics (1982) 22: 8. doi:10.1007/BF02325696


Interference fits are used extensively in aircraft structural joints because of their improved fatigue performance. Recent advances in analysis of these joints have increased understanding of the nonlinear load-contact and load-interfacial slip variations in these joints. Experimental work in these problems is lacking due to difficulties in determining partial contact and partial slip along the pin-hole interface. In this paper, an experimental procedure is enumerated for determining load-contact relations in interference/clearance fits, using photoelastic models and applying a technique for detecting progress of separation/contact up to predetermined locations. The study incorporates a detailed procedure for model making, controlling interference, locating break of contact up to known locations around the interface, estimating optically the degree of interference, determining interfacial friction and evaluating stresses in the sheet. Experiments, simulating joints in large sheets, were carried out under both pin and plate loads. The present studies provide load-separation behavior in interference joint with finite interfacial friction.


2 a

diameter of hole

E, G, v

elastic constants; Young's modulus, rigidity modulus and Poisson's ratio




material fringe constant in tension


thickness of model


pin load per unit thickness

r, θ;X,Y

polar and Cartesian coordinates relative to hole center


applied far-field stresses


applied stress-level parameter

\(2\theta _s ,2\theta _c \)

arcs of separation or contact


proportional interference between pin and hole=(pin diameter-hole diameter)/hole diameter


friction coefficient

σ, τ

direct and shear stresses with appropriate subscripts

\(\tau _{max} \)

maximum shear stress at a point



threshold for initiation of separation

s, p

refers to sheet and pin

x, y, r, π

directions, associated with load and stress level

Copyright information

© Society for Experimental Mechanics, Inc. 1982

Authors and Affiliations

  • S. P. Ghosh
    • 1
  • B. Dattaguru
    • 2
  • A. K. Rao
    • 2
  1. 1.Ministry of EducationGovernment of IndiaIndia
  2. 2.Department of Aeronautical EngineeringIndian Institute of ScienceBangaloreIndia

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