Meaning
Non-destructive testing method that determines fastener tension by measuring the time of flight of sound waves. The ultrasonic bolt measurement sends an ultrasonic pulse through the bolt and measures how long it takes to reflect back from the other end. As the bolt is tightened, it stretches and the speed of the sound wave changes.
This allows for a very precise measurement of the actual load without relying on friction based torque readings.
Tension Verification
Direct measurement of the bolt’s elongation provides a more accurate value than a torque wrench. Since friction varies wildly with lubrication and surface finish, ultrasonic bolt measurement is the preferred choice for critical joints.
Elongation Tracking
Recording the length of the fastener before and after tightening shows the exact amount of stretch. This data is used to calculate the clamping force applied to the assembly.
Clamping Force
Structural integrity of heavy machinery and bridges depends on these fasteners remaining under high tension. If the ultrasonic bolt measurement shows that the tension has dropped, the bolt must be retightened or replaced. This technique is often used during maintenance audits to check for loose bolts in hard to reach places.
It provides a documented record of the preload for quality assurance and safety compliance.
