ASTM B312 Test Fixtures & Test Systems Model: G-ASTM-B312

Viscoelasticity in Powder Compacts: ASTM B312 is critical for the powder metallurgy (P/M) industry, as it defines the handleability of a part before it is sintered. The Green specimen is essentially a compressed pile of dust held together by mechanical interlocking. The mechanical interface of the MTO 3-point bend fixture must utilize hardened, high-polish rollers to prevent digging into the soft edges of the compact. If the rollers are static or oxidized, they will induce a frictional drag that resists the expansion of the lower fibers, artificially inflating the recorded green strength. Engineering the load train requires a high-resolution, low-capacity load cell (typically 500N to 2kN); using a high-capacity cell will fail to capture the subtle crack initiation point that defines the rupture. The fixture must also account for the springback of the compact after it is ejected from the die. If the specimen isn’t perfectly flat, the initial load will be concentrated on a single point, causing a premature fracture that is a result of fixture misalignment rather than poor powder quality. Achieving a clean, linear stress-strain curve on a green compact is the gold standard for validating P/M lubricant and pressure consistency.