Experimental and numerical exploration for the design of swift-constructed demountable blind bolts

In this study, a new type of blind bolt that combines high tensile resistance and stiffness with easy and fast installation and demounting capabilities is proposed, named Swift-Constructed Demountable Blind Bolt (SCDBB). The components, intended working mechanism, and fabrication process are first introduced. Geometric constraints of critical components are then derived based on the desired behaviour. To study the performance of SCDBBs under tensile loading and their behaviour during the installation process, 9 experimental tests were conducted. Two failure modes, namely, bolt shank fracture and buckling of the expansion nut blades, were revealed when subjected to maximum tensile loading. Subsequently, finite element (FE) models were developed and validated by comparing the numerical results with the experimental data. To further explore the impact of key design parameters on the behaviour of the bolts under tensile loading and performance during installation, parametric studies consisting of 106 FE models were conducted for bolts of three sizes with variations in four key design parameters. The findings indicate that the failure modes under maximum tensile loading and maximum installation force are sensitive to the length, thickness, and gap of the elastic expansion nut. The optimised ranges for each design parameter were identified to prevent undesirable blade buckling.