PSI - Issue 39

Hithendra Karakampalle et al. / Procedia Structural Integrity 39 (2022) 711–721 Author name / Structural Integrity Procedia 00 (2021) 000–000

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1. Introduction Riveted joints are widely used in almost all areas of engineering, such as aircrafts, automobiles, ships, boilers, bridges, etc. Several studies have been carried out to assess the fatigue life of these joints, under varying parameters such as rivet diameters [Liu et al. (2020)], pitch between the rows [Liu et al. (2020)], rivet-hole interference [Lei et al. (2017)], squeezing force [Szolwinski et al. (2000)], etc. Most of them deal with the total fatigue life of lap and butt joints. Limited studies have focused on the fracture mechanics approach, viz., the presence of an initial crack and its propagation; for this, the knowledge of variation of SIF with crack length is required. Joints arranged in special pattern such as Lozenge’s are yet to be explored fully. This work is an attempt to fill this gap, with focus on SIF in straps used in the butt joint of plates, with 6 rivet joints in 3-2-1 Lozenge pattern. Straps are considered in this work, as initial cracks appear on them when the strap thickness is less than or equal to the plate thickness [Liu et al. (2020)]. Figure 1(a) shows a loaded double strap butt joint of plates with rivets in Lozenge pattern. Considering 100 percent load transfer, the strap can be assumed to be held in position by left half of the rivets and loaded by the right half of the rivets. Considering symmetry, it can be further simplified as an edge loaded plate, fixed at six joints in 3-2-1 pattern as shown in Fig. 1 (b). Using this geometrical configuration, three case studies have been considered to assess the impact of cracks and interference on the joints arranged in Lozenge pattern. a b

Fig.1(a) Double Strap Butt Joint, with rivets in Lozenge Pattern; (b) Simplified strap geometry.

Nomenclature 2a

crack length (mm) size of hole (mm) size of pin (mm) elastic modulus (GPa) height of plate (mm)

d

D E

h

K I

stress intensity factor, Mode I (MPa√mm) crack length from surface of the hole (mm)

l t

thickness of plate (mm) width of plate (mm)

w

ν σ

Poisson’s ratio

remote tensile stress (MPa)

σ h σ u σ x σ y

hoop stress (MPa)

ultimate strength in tension (MPa) normal stress in X direction (MPa) yield strength in tension (MPa)