Magnetostrictive Sensor for Anchor Bolt Stress Monitoring
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Solution Overview
Problem
Conventional methods for measuring tensile stress in anchor bolts of concrete foundations, such as those supporting wind turbines, lack accuracy and accessibility, particularly since many components are embedded in concrete, and existing methods like ultrasonic measurements and friction measurements are offline and difficult to perform.
Innovation Solution
Incorporating a magnetostrictive load measuring sensor within the foundation body to measure tensile stress in anchor bolts, using magnetically encoded steel rods and magnetic field sensors to monitor stress without direct access, allowing continuous or regular monitoring of tensile stress during tightening and operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional torque measurement methods are used at the bolt nut, then the measurement can be performed with simple equipment, but the measurement accuracy is insufficient due to friction and manufacturing variations
Solution Approach 1:
The patent replaces mechanical torque measurement methods with magnetostrictive sensing technology. A magnetostrictive sensor detects changes in magnetic field caused by tensile stress in the anchor bolt, converting mechanical stress into measurable magnetic signal changes. This substitution eliminates friction-related errors and provides direct tensile stress measurement with high precision.
Solution Approach 2:
The patent utilizes the magnetostrictive effect where the magnetic properties of the anchor bolt change in response to tensile stress. By measuring changes in magnetic field parameters (flux density, field distribution) rather than mechanical torque, the system achieves accurate tensile stress measurement that directly reflects the actual load on the anchor bolt.
2Ease of operation
If ultrasonic or resonant frequency methods are used to measure bolt length and tension, then measurement can be performed, but these methods can only be conducted offline and are difficult to perform on embedded components
Solution Approach 1:
The magnetostrictive sensor is installed on the anchor bolt before the concrete foundation is poured, embedding the sensing element within the foundation structure during construction. This preliminary installation allows the sensor to remain in position and continue measuring tensile stress throughout the structure's operational life, eliminating the need for later access to embedded components.
Solution Approach 2:
The magnetostrictive sensor acts as an intermediary between the anchor bolt and the measurement system. By attaching the sensor to the bolt surface, it transmits mechanical stress information through magnetic field changes, enabling non-contact or minimal-contact measurement that works effectively even when the bolt is embedded in concrete.
3Measurement precision
If nominal torque values are used for bolt tightening, then the tightening process is simple, but the desired accuracy in tensile stress is not achieved due to friction and manufacturing aspects
Solution Approach 1:
The magnetostrictive sensor provides real-time feedback on the actual tensile stress in the anchor bolt during the tightening process. This feedback allows operators to adjust the tightening torque to achieve the desired tensile stress level, compensating for variations in friction and manufacturing tolerances that would otherwise make precise control difficult.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables precise and stable measurement of tensile stress in anchor bolts, reducing the need for excessive materials in foundations, detecting potential issues early, and optimizing foundation design for improved stability and operation safety.
Implementation Method 1
a magnetostrictive load measuring sensor for measuring loads on the at least one anchor bolt
Data Source
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AI summary
A foundation 100 for supporting a structure 20 is provided. The foundation includes a foundation body 102, at least one anchor bolt 110 connecting a lower anchor plate 104 and the structure 20, a magnetostrictive load measuring sensor 120 for measuring loads on the at least one anchor bolt, the magnetostrictive load measuring sensor being positioned within the foundation body 102.