Ductile Fracture Simulation of Shear-Out Strength Behavior and Design Equations of Bolted Lap Joints

This paper presents a detailed study of the fracture behavior and ultimate resistance of bolted lap joints that fail by shear-out rupture, including laboratory tests, detailed computational simulations of ductile fracture, and theoretical development of design strength equations. Four double-bolted lap joints were tested to provide validation data for shear-out failure and tension rupture. Parallel finite element models were developed to simulate the lap joints, incorporating two ductile fracture criteria whose parameters were calibrated by 12 coupon tests. The finite element model accurately simulated large-scale yielding, ductile fracture, and the influence of frictions at bolt shank-to-ply interface as well as ply-to-ply interface on the shear-out capacity of the joints. New design formulas are proposed to determine the ultimate shear-out strength, considering the friction between the bolt shank and ply plate as well as the ply plate and bolt geometry. The proposed design equations consider the distribution of shear stresses around the bolt hole and thus can accurately predict the shear plane position. The proposed design equations are compared with finite element parametric studies as well as test results and strength predictions by existing design standards. The comparison demonstrates that the proposed equations provide improved prediction of shear-out capacity.