SBIR Phase I: A Novel System for Uniform Preload in Bolted Joints

The broader impact of this Small Business Innovation Research (SBIR) Phase I project is the development of an improved bolt tightening technology applicable to a wide variety of industries including renewable, power generation, transportation, and infrastructure. The basic bolt-tightening method utilizing a torque-wrench has remained largely unchanged since the introduction of the modern fastener in the 1800s. This results in a preload variation of up to 30% in a multi-bolt joint. New methods, including preload sensing, reduce this variation down to 15% albeit at a high cost. High preload variation leads to inefficient joints, bolt loosening, bolt rupture, and leakage problems over the joint’s lifetime. The proposed innovation can potentially reduce this variation down to 5%, a significant improvement. Additionally, it allows multi-bolt joint tightening in just two passes compared to the current method of four passes which saves time and labor. Successful implementation of the proposed technology will be beneficial in reducing the cost of energy, in particular, offshore wind which is poised for rapid growth in the US. Additionally, it will help prevent hazardous leakage of joints in the nuclear, petrochemical, and oil and gas industries and prevent vibration loosening of joints in the transportation, infrastructure, and heavy machinery industries. The proposed technology combines existing, widely used technologies, such as a torque-wrench and ultrasonic bolt tension measurement, with a unique and proprietary computer algorithm. The proposed innovation offers precise control of bolt tensioning, which is essential for the reliability of multi-bolt flange joints. The fundamental concept is already proven through high-fidelity simulations. In Phase I research, simulation studies will continue on more realistic multi-bolt joints to further validate the algorithm. The primary goal of Phase I research is the experimental validation and optimization of the proposed algorithm. Extensive testing will be conducted on a scaled-down flange joint with the help of ultrasonic preload sensors. The secondary goal is the development of a minimum viable product concept based on this system. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.