Screw Fastener Torque Verification via dT/dF Analysis
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Solution Overview
Problem
Existing screw fastener tightening methods often result in insufficient clamping force between rigid machine elements due to incomplete tightening, leading to premature failure under fluctuating loads, and existing verification methods are either unreliable or labor-intensive.
Innovation Solution
A screw fastener testing tool that measures torque and its derivative during a rotational movement, comparing these values against stored thresholds to determine if the screw has been tightened correctly or beyond the yielding point, allowing for quick and accurate verification without loosening the screw.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If screw fasteners are tightened to a predetermined tightening torque, then the tightening process is simple and quick, but the clamping force is insufficient and the fastener may not be tightly fastened
Solution Approach 1:
The patent replaces traditional mechanical torque-based tightening control with an acoustic emission detection system. By monitoring acoustic signals generated during tightening, the system can detect when the fastener has reached sufficient tightness, eliminating the need for complex torque measurement mechanisms while ensuring reliable fastening.
Solution Approach 2:
The patent implements a feedback mechanism where acoustic emission signals during tightening are continuously monitored and analyzed. When the acoustic signal indicates sufficient tightness has been achieved, the tightening process is automatically stopped, providing real-time feedback control that ensures both speed and reliability.
2Strength
If screw fasteners are tightened beyond the yielding point to use 100% capacity, then the clamping force increases and varies less, but it is difficult to verify if the yielding point has been reached
Solution Approach 1:
The patent replaces complex mechanical measurement systems for detecting yielding with an acoustic emission detection system. The acoustic signals naturally change characteristics when the yielding point is reached, providing a simple yet precise method to verify tightening quality without requiring sophisticated measurement equipment.
Solution Approach 2:
The patent uses acoustic signal characteristics as an indicator of tightening state, analogous to color changes. Different acoustic signal patterns correspond to different tightening stages, allowing operators to easily identify when the yielding point has been reached through acoustic feedback rather than complex measurements.
3Measurement precision
If traditional verification methods are used such as measuring permanent elongation or using shim elements, then tightening quality can be checked, but the process becomes labor-intensive and time-consuming
Solution Approach 1:
The patent integrates verification into the tightening process itself through continuous acoustic emission monitoring. Rather than performing separate verification steps after tightening, the system continuously detects tightening quality in real-time, eliminating idle verification time while maintaining high measurement precision.
Solution Approach 2:
The patent enables the fastening system to self-verify its own tightening quality through acoustic emission detection. The system automatically monitors and assesses tightening quality without requiring external verification tools or additional manual steps, making the verification process as efficient as the tightening process itself.
4Reliability
If friction variation between screw fastener surfaces is accounted for by tightening to lower torque, then premature failure is reduced, but the fastener capacity is not fully utilized and over-dimensioning is required
Solution Approach 1:
The patent uses acoustic emission feedback to detect the actual tightening state of each fastener individually, allowing the system to optimize the balance between reliability and capacity utilization. By monitoring acoustic signals, the system can determine when sufficient tightness is achieved without being overly conservative, thereby fully utilizing fastener capacity while maintaining fatigue resistance.
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
Ensures that screw fasteners are correctly tightened and fully utilizing their capacity, reducing premature failure and labor-intensive verification processes, while providing high accuracy and ease of use for non-specialized operators.
Implementation Method 1
the fastener is subjected to a tightening process during which acoustic emissions are generated by the fastener and a sensor is arranged for detecting the acoustic emissions
Data Source
Figure 1a~1b
Figure 2
Figure 3~4
AI summary
A screw fastener testing method for verifying the status of a previously tightened screw fastener as regards installed torque (T) and actual torque growth per angle of rotation (dT/dF) properties including the following steps applying an increasing tightening torque on the fastener, measuring the torque magnitude (T) at the start of rotation of the fastener, measuring the rotational movement (F) of the fastener after said start of rotation, calculating the torque growth per angle of rotation (dT/dF) for a certain predetermined test interval of rotation (?F) from said start of rotation, comparing the torque magnitude (T) indicated during rotation and the calculated torque growth per angle of rotation (dT/dF) during said test interval (?F) of rotation with predetermined reference values (Tstart, KR) or (TE, KP), respectively, characteristic for the actual fastener when tightened to a desired target torque level, and approving or disapproving the fastener status in view of said reference values.