Experimental Studies of an Asymmetric Multi-Bolted Connection under Monotonic Loads

Area of Science:

• Mechanical Engineering
• Structural Analysis
• Materials Science

Background:

• Multi-bolted connections are critical in various engineering structures.
• Understanding bolt force behavior under operational loads is essential for structural integrity.
• Asymmetric connections present unique challenges in load distribution.

Purpose of the Study:

• To experimentally evaluate bolt forces in a preloaded asymmetric multi-bolted connection during its exploitation phase.
• To analyze the redistribution of forces within the connection after load application and removal.
• To establish a methodology for monitoring bolt forces in complex joint assemblies.

Main Methods:

• Development and utilization of specialized test stands for bolt calibration and connection analysis.
• Application of an optimal tightening sequence in three passes with strain gauge monitoring.
• Testing the connection under linearly increasing and decreasing exploitation loads using an Instron 8850 testing machine.
• Statistical analysis of measurement data saved in MATLAB Simulink.

Main Results:

• Bolt forces were monitored and recorded during cyclic loading and unloading.
• Statistical analysis revealed distributions of normalized bolt forces.
• Significant changes in individual bolt forces were observed after the unloading phase relative to initial preload values.

Conclusions:

• The preload in individual bolts of an asymmetric multi-bolted connection is not constant during exploitation.
• Unloading the connection leads to a redistribution of forces among the bolts.
• Experimental data provides crucial insights into the long-term behavior and reliability of bolted joints.