ASTM B871 Test Fixtures & Test Systems Model: G-ASTM-B871
Crack Initiation Energy: This standard measures the Tear Strength of aluminum using a Kahn-type specimen. It is the definitive measure of a material’s resistance to crack propagation.
Technical Specifications
| Specification | Value |
|---|---|
| Test Type | Standards |
| Industry Standard | ASTM B871 |
| Interface Description | Optimized for TestResources Load Frames; universal adapters available for legacy systems. |
Interface & Compatibility
Expert Commentary
The Dynamics of Fracture Energy: ASTM B871 is used to evaluate the toughness of aluminum alloys, specifically for aerospace skin materials. The MTO Tear Test Fixture utilizes a Pin-and-Clevis arrangement to allow the specimen to rotate slightly as the crack propagates. This rotation is essential; if the specimen is held rigidly in wedge grips, the crack will be forced to follow a path that doesn’t represent the material’s natural grain orientation. The engineering challenge is the Compliance Calibration. The fixture must be stiff enough to capture the rapid drop in load as the crack jumps through the microstructure. For 2000-series alloys, the Tear Index (the ratio of tear strength to yield strength) is the primary metric for damage tolerance. MTO’s fixtures are engineered to minimize pin-friction. If the pins bind, they store elastic energy that is suddenly released into the crack tip, causing a snap-fracture that overestimates the brittleness of the alloy. By using hardened, polished pins and a low-friction clevis, we ensure that the load-displacement curve is a pure reflection of the energy required to create new surface area (fracture energy), providing the high-fidelity data needed for aircraft life-extension programs.