Fatigue Testing Device with Curved Jigs
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Solution Overview
Problem
Conventional fatigue testing devices face challenges in applying excessive stress to sheet or plate-shaped test pieces due to uncontrolled vibration amplitudes, leading to potential fracture and prolonged testing times, especially when testing at high frequencies or for extended service life evaluations.
Innovation Solution
The fatigue testing device fixes the test piece between two fixing surfaces with increasing space between the surface and the test piece, preventing excessive stress by limiting vibration amplitude and using a high-speed air valve to create controlled vibrations, allowing for efficient testing of sheet or plate-shaped materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the test piece is fixed only at the proximal end and vibrated with pulsed pressure waves, then the vibration frequency can be adjusted to resonance frequency, but the amplitude becomes too large when frequency is not adjusted appropriately, causing excessive stress and potential fracture
Solution Approach 1:
A stopper is introduced as an intermediary element between the test piece and the fixing jig. The stopper limits the vibration amplitude by physically stopping the test piece at predetermined positions during vibration, preventing excessive stress concentration and potential fracture while allowing high-frequency resonance vibration for efficient fatigue testing
Solution Approach 2:
The stopper is pre-positioned to counteract the potential harmful effect of excessive vibration amplitude before it can cause damage. By establishing predetermined stop positions in advance, the system prevents the test piece from experiencing stress levels that would lead to fracture, ensuring reliability during high-speed fatigue testing
2Speed
If mechanical drive or hydraulic drive is used for tension-compression stress type fatigue tests, then high-speed loading at or above 1000 Hz can be performed, but heat generation occurs due to strains in the test piece requiring cooling systems
Solution Approach 1:
The patent replaces mechanical drive systems with pneumatic drive using pulsed pressure waves generated by a high-frequency motor-driven pulse generator. This substitution eliminates the need for complex mechanical or hydraulic mechanisms, reduces heat generation from mechanical friction and strain, and enables high-frequency fatigue testing without requiring cooling systems
3Productivity
If completely reversed fatigue test with crank connected to rotating body is used for sheet or plate-shaped test pieces, then bending stress can be applied, but test frequency is restricted by rotational speed of drive motor, requiring about 2 to 5 days to load 1 × 10^7 cycles
Solution Approach 1:
The patent uses periodic pulsed pressure waves instead of continuous rotational mechanical drive. The high-frequency motor generates pulsed pressure variations that cause the test piece to vibrate at resonance frequency, achieving the required 1 × 10^7 cycles in much shorter time compared to mechanical crank-driven systems limited by motor rotational speed
Solution Approach 2:
The patent directly induces mechanical vibration in the test piece using pulsed pressure waves. By exciting the test piece at its resonance frequency, the system achieves high-cycle fatigue testing efficiently, bypassing the speed limitations of mechanical drive systems and significantly reducing testing time
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
This configuration effectively suppresses excessive stress and vibration amplitudes, enabling reliable fatigue life testing of sheet or plate-shaped materials without risk of fracture, while reducing testing time and cost by maintaining controlled stress levels.
Implementation Method 1
the vibration frequency of the test piece becomes a resonance frequency by adjusting the frequency of pressure variations in the pressure wave so as to match the resonance frequency of the test piece
Implementation Method 2
a test piece which is fixed at a proximal end side with a fixing jig is vibrated by applying a pulsed pressure wave generated from a pulse generator driven by a high-frequency motor
Implementation Method 3
a displacement detector for detecting a vibration displacement of the test piece
Implementation Method 4
a first fixing surface to which the test piece is fixed in a cantilever state, wherein a space between the first fixing surface and the test piece increases as a distance from a location where the test piece is fixed to the first fixing surface increases
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
A fatigue testing device 1 comprises a fixing member 4 constituted by a lower jig 2 and an upper jig 3. The lower jig 2 and the upper jig 3 are fixed with a bolt 5, and a sheet or plate-shaped metal plate 6 is fixed in a cantilever state such that it is interposed between the lower jig 2 and the upper jig 3. The lower jig 2 has a fixing surface 2a to which the metal sheet or plate 6 is fixed, and the fixing surface 2a has a curved shape such that the space between the fixing surface 2a and the metal sheet or plate 6 increases with increasing distance from the location where the metal sheet or plate 6 is fixed to the fixing surface 2a. The upper jig 3 also has a fixing surface 3a to which the metal sheet or plate 6 is fixed, and the fixing surface 3a has a curved shape such that the space between the fixing surface 3a and the metal sheet or plate 6 increases with increasing distance from the location where the metal sheet or plate 6 is fixed to the fixing surface 3a.