1. Spring 2015 ECE Senior Design Topic Graduate Student Advisors
Development of a Portable Real-Time Bolt Preload Monitoring System using Piezo-ceramic Transducers
Faculty Advisor
Dr. Gangbing Song
Tel: x34525
Graduate Student Advisors
Mr. Seyed Mohammad Parvasi
Tel: x34498
Mr. Chenyu Wang
Tel: x34549
Sponsored by Cameron

2. Background
Bolt connections are the most commonly used connection element in structures and devices especially in Oil and Gas industry.
Bolted connections commonly fail due to insufficient/excessive preloads during installation or a loss of axis load (self-loosening) caused by external dynamic loads in service.

3. Bolt stress measurement using strain gauge
Commercial Methods for bolt monitoring
Commercial methods for bolt monitoring include
Direct measurement
The most current conventional techniques in industry for monitoring the bolted joints directly measure the stress between the connected pieces or the strain in the bolt.
Indirect measurement
Indirect measurement on the other hand are driven by ultrasonic technology.
Bolt stress measurement using strain gauge
Conventional application of ultrasonic measurements of bolt connections

4. Introduction to piezoceramics
Piezoceramics will generate an electric charge when it is subjected to a stress or strain and also produce a stress and strain when an electric field is applied to it in its polarization direction.
Piezoceramics can be utilized as both an actuator and a sensor.
In this research, PZT transducers (lead zirconate titanate), a type of commonly used piezoceramic material with high piezoelectric effect, may be used in the form of PZT patches and PZT stack devices to initiate and capture stress waves in bolted connections.
Piezoelectricity

5. Time reversal principle scheme
Time Reversal Technique
The time reversal technique is an adaptive wave transmission technique which can focus acoustic/ultrasound waves spatially and temporally in both homogenous and non-homogenous media. Based on TR, the input signal can be focused symmetrically at the excitation point using time reversal (TR) process and the peak value of the output signal shows the focused energy of the signal at the source point.
Complex media
Source
Time Reversal Mirror
Time reversal principle scheme

6. Proposed Method for Bolt Monitoring
An innovative time reversal technique using piezoelectric transducers is proposed to monitor bolt preload and torque levels in real-time without modifying the bolt joint body.
Two PZT patches mounted on a single lapped bolt joint. Different pre-loads were applied on the bolt joint by a torque wrench. Under each pre-load condition, the time reversal technique was utilized to obtain a focused signal peak.
Relationship between focused signal peak and preload torque
Bolted connection with PZT patches installed

7. Previous Achievements
We studied the feasibility of in real-time bolt preload monitoring of every single bolts of a flanged ball valve using time reversal procedure and piezoceramic transducers.
PZT 1: Actuator
PZT 2: Sensor

8. Experiment loads and conditions
35 lb.ft torque applied on all the nuts except L1 and C
Seven distinctive torque levels applied on L1 (5, 10, 15, 20, 25, 30, 35 lb.ft)
For each torque level on L1, we applied seven distinctive torque levels on C (5, 10, 15, 20, 25, 30, 35 lb.ft)
C : Center nut
L1: 1st left nut

9. The relationship between the focused signal peak and preload torque applied on nut C

10. Advantages of the proposed method
Compared to currently available methods, the use of time reversal based monitoring through PZT bonded tapes offers advantages include:
Hassle-free setup
Requires no structural modification to the bolted connection.
Simultaneous monitoring of all bolts in near real-time speed
Low cost and simple production for PZT-patches and flexible polymer tapes
The time reversal procedure used in this method is highly robust and can withstand high levels of noise in the system

11. Project Goal Major Tasks:
The objective of the proposed project is to design and build a portable, reliable, hassle free actuating/sensing device for real-time monitoring of bolt pre-loads in flanged structures.
Major Tasks:
Two flexible polymer tapes, one for actuation and the other for sensing, are fabricated separately with lengths matching the circumferences of the flange and the valve body (i.e. one tape for each circumference).
The actuator and sensor tapes will wrap around the circumference of the flange and valve body, respectively, and will have PZT patches installed on the inner surface of the tapes to act as the actuating/sensing transducer.
The number of PZT patches will correspond to the number of bolts in the valve of interest and will have a spacing equal to the distance of two consecutive bolts.
A DAQ board (NI systems) will be used for the generation and measurement of signals for the PZT patches.

12. What you will learn and Deliverables
Piezoceramic transducers
Active sensing method
Time reversal technique
Embedded system
Real time monitoring techniques
Deliverables:
A portable and functional device or monitoring protocol that can be economically and widely applied to monitor bolt connections under most conditions.
Preliminary database listing desired time reversal peak values for different size and shape bolted connections.

13. Questions ?