Overview
ISO 18591:2015 defines a standardized testing method to determine the compressive strength of ceramic granules used in fine/advanced ceramics. The method measures granule behavior under uniaxial compressive loading in a confining die using a Universal Testing Machine (UTM), records the load‑displacement response, converts it to a pressure–density curve, and identifies the critical pressure (compressive strength) at the slope change.
Key topics and technical requirements
- Test principle: Compact granules in a cylindrical die, record load‑displacement, convert to pressure–density, determine compressive strength from intersection of two slope regions.
- Apparatus & accuracy:
- Cylindrical die (hard material; diameter 10–25 mm; height/diameter ratio 0.3–0.5).
- UTM capable of simultaneous load and displacement recording; accuracy per ISO 7500‑1, Grade 1 (±1%).
- Balance (≥10 g capacity, precision ±0.001 g) and micrometer (precision ±0.01 mm).
- Procedure essentials:
- Typical crosshead speed: 1 mm/min for compaction.
- Test performed on three independent test portions; report average densities.
- Optional granule drying: 110 °C ±5 °C for ≥24 h if required (do not dry granules containing volatile organics).
- Lubrication: die‑wall lubrication or powder lubricant (0.1–3.0 wt% solid lubricant) is allowed but must be reported - lubrication can significantly affect results.
- Data and results:
- Convert load‑displacement to pressure (load/area) and compact density; plot on a pressure (log scale) vs density curve.
- Compressive strength = intercept point of two linear regions of different slope.
- Reporting:
- Test report per ISO/IEC 17025 requirements, including material batch, test conditions (temperature/humidity), lubrication details, compact dimensions, pressure–density curve and comments.
Applications
ISO 18591 is used for:
- Quality control of ceramic granules and powder feedstocks.
- Process optimization for pressing and forming of advanced/technical ceramics (electronics, structural, biomedical ceramics).
- Predicting green density and compaction behavior for powder‑to‑component processes.
- Comparative testing between batches, suppliers, or formulation variants.
Who should use it
- Materials scientists and ceramic engineers
- Manufacturing and quality labs in advanced ceramics industry
- R&D teams developing powder formulations and granulation processes
- Accredited testing laboratories seeking reproducible compressive strength data
Related standards
- ISO 7500-1 (UTM calibration and accuracy)
- ISO/IEC 17025 (testing laboratory reporting and competence)
- EN 725‑10, JIS R1639‑5/6, KS L 1623 (related compaction/ceramic powder test methods)
Keywords: ISO 18591, compressive strength, ceramic granules, fine ceramics, advanced ceramics, pressure–density curve, uniaxial compressive loading, universal testing machine, powder compaction, test report.
Open preview (PDF)Fine ceramics (advanced ceramics, advanced technical ceramics) — Determination of compressive strength of ceramic granules