Determining Individual Stresses Throughout a Pinned Aluminum Joint by Reflective Photoelasticity

Abstract

Pinned (bolted) joints are an extremely important, but difficult to analyze, structural or mechanical element. They are a class of inverse problems in which the stresses at the pin/hole interface are typically unknown. Moreover, stresses vary non-linearly with applied load. Failures of mechanical or structural systems frequently initiate at connections. Although almost always present, many stress analyses of such mechanical connections ignore friction for simplicity. The stresses are evaluated here in an aluminum connector using a series solution of an Airy stress function, the coefficients being evaluated from known boundary tractions (near, but not including the contact region on the hole) and photoelastically measured data obtained from a bonded birefringent coating. Both friction and pin/hole clearance are accounted for, and individual stresses are evaluated full-field, including on the contact boundary of the hole.

Experimentally Determined Stresses Associated with Elliptical Holes Using Polar Coordinates

“…Classical photoelastic analysis of elliptically perforated members requires physically modelling the actual problem [23–28]. An alternative method could be to employ reflective grey‐field photoelasticity [41, 43]. Although the holes of Refs.…”

“…Although the holes of Refs. [41, 43] were round, non‐circular holes can be handled by stress/strain analysing the birefringent coating with a stress function in polar coordinates. Moiré, speckle or digital image analysis might be employed to stress analyse non‐circularly perforated members, but these techniques suffer from having to differentiate the measured data – something TSA avoids.…”

Characterization of friction at three contact pairs by photoelastic isotropic point (IP)

“…Equations (3), (4), (5) and (6) are four independent equations involving the six unknowns (Q 1 , γ 1 , Q 2 , γ 2 and P , γ 3 ). Therefore, any two unknowns are left undetermined at this stage.…”

“…al. 5 determined stress components distribution in a pin-loaded aluminum connection along steel pin and aluminum plate using a hybridized photoelastic-Airy stress function method. Burguete and Patterson 6 studied contact between a cylinder and a half-space using Photoelasticity.…”