The testing fixture itself is a locking mechanism. There is no fixed structural pattern; the structure varies greatly depending on the different specimens and the magnitude of the test force.
Specimens subjected to high test forces generally employ an inclined plane clamping structure, with the clamping force increasing as the test force increases.
If testing fixtures are classified by structure, they can be divided into wedge-shaped fixtures (those using the inclined plane locking principle), clamp-on fixtures (those using the single-sided or double-sided threaded clamping principle), winding fixtures (those where the specimen is locked by winding), eccentric fixtures (those using the eccentric locking principle), lever fixtures (those using the lever force amplification principle), shoulder fixtures (those suitable for shoulder specimens), bolt fixtures (those suitable for testing the thread strength of bolts, screws, studs, etc.), and 90° peeling fixtures (those suitable for vertical or vertical peeling of two specimens), etc.
We know that mechanical locking structures include: threads (i.e., screws, nuts), bevels, eccentric wheels, levers, etc. Fixtures are combinations of these structures. Each fixture structure has its own advantages and disadvantages. For example, wedge fixtures have a small initial clamping force, which increases with the increase of the test force. Clamping fixtures have a large initial clamping force, which decreases with the increase of the test force.
