Load-Sensing Washer With Strain Gauges for Bolted Joint Clamping Load
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Solution Overview
Problem
Conventional methods for determining the clamping force of bolted joints are time-consuming and provide only approximate axial load measurements, especially in applications with vibration, cyclic loading, or temperature variations, necessitating a more precise and efficient method for installation and periodic maintenance.
Innovation Solution
An instrumented washer with strain gauges and an integrated communication assembly, including a microchip, that senses deformation and wirelessly transmits axial load data to a reader device, allowing for accurate and efficient determination of clamping force in bolted joints.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional torque-based methods are used to determine clamping force, then the measurement process is simple, but the measurement precision is low and only provides approximate axial load values
Solution Approach 1:
The patent replaces conventional mechanical torque-based measurement methods with a strain gauge-based electrical sensing system. The strain gauges convert mechanical deformation of the washer body into electrical signals, enabling direct measurement of axial clamping load with high precision. This substitution eliminates the need for torque calculations and provides accurate real-time load data.
Solution Approach 2:
The instrumented washer acts as an intermediary element between the bolted joint components. It incorporates strain gauges that sense the deformation of the washer body caused by clamping forces, converting mechanical stress into measurable electrical signals. This intermediary device enables indirect but accurate measurement of the axial load without interfering with the joint's function.
2Productivity
If conventional torque-based methods are used to check bolted joints, then the equipment is simple, but the time consumption is high particularly when numerous joints need to be checked
Solution Approach 1:
The patent replaces time-consuming manual torque measurement procedures with an automated electrical sensing system. The strain gauges continuously monitor the axial load, and the communication assembly enables rapid data retrieval, allowing multiple joints to be inspected quickly without sacrificing measurement accuracy.
Solution Approach 2:
The instrumented washer enables continuous monitoring of the clamping force throughout the operational life of the bolted joint. The strain gauges and communication assembly allow for real-time or periodic measurement without interrupting the joint's function, significantly improving inspection efficiency compared to discrete torque checks.
3Measurement precision
If strain gauges and communication assembly are added to the washer, then the measurement precision and efficiency are improved, but the device complexity increases
Solution Approach 1:
The patent merges multiple functions into a single integrated component. The washer body combines structural support functions with sensing functions (strain gauges) and communication functions (integrated circuit and antenna) into one unified instrumented washer, eliminating the need for separate measurement devices and reducing overall system complexity.
Solution Approach 2:
The instrumented washer serves multiple functions simultaneously: it provides the traditional washer function of distributing load and protecting surfaces, acts as a sensing element through strain gauges, and enables wireless communication of load data. This multi-functionality reduces the need for additional components and simplifies the overall measurement system.
4Reliability
If strain gauges are exposed on the washer body, then the sensing function is direct, but the reliability decreases due to vulnerability to environmental factors
Solution Approach 1:
The patent embeds the strain gauges within a protective structure. The strain sensing elements are nested within the washer body or protected by a cover, shielding them from environmental damage while maintaining their ability to sense deformation. The integrated circuit and antenna are also protected within the washer structure.
Solution Approach 2:
The patent uses a protective cover or encapsulation layer that conforms to the washer body shape. This thin protective shell protects the strain gauges and electronic components from environmental factors such as moisture, dust, and mechanical damage, while allowing the strain gauges to continue sensing deformation through the protective layer.
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 efficient measurement of axial clamping load in bolted joints, facilitating accurate installation and maintenance, with the ability to store historical data and provide real-time adjustments, improving operational reliability and efficiency.
Implementation Method 1
One or more strain gauges are provided on the circumferential sidewall and are configured to sense a deformation of the washer body do to clamping forces of the bolted joint
Data Source
AI summary
An instrumented, load-sensing washer that can be used on a bolted joint to facilitate determining an axial clamping load of the bolted joint. The washer includes an annular washer body having first and second oppositely disposed axial ends and an outer circumferential sidewall. At least one strain gauge is provided on the circumferential sidewall and is configured to sense a deformation of the washer body do to clamping forces of the bolted joint. The washer further includes a communication assembly operatively coupled with the at least one strain gauge. The communication assembly may include an integrated circuit adapted to receive electrical signals from the at least one strain gauge related to the axial load borne by the washer.