Overview
ISO 3928:2016 - Sintered metal materials, excluding hardmetals - Fatigue test pieces specifies geometries, die-cavity dimensions and key manufacturing/identification requirements for fatigue test specimens made from sintered and powder-forged metals (hardmetals excluded). The standard covers both pressed-and-sintered (compact-formed) fatigue specimens and machined test pieces, and includes guidance on die design, finishing, orientation for bending tests, and specimen identification.
Key Topics and Requirements
- Scope: Applicable to all sintered metals and alloys excluding hardmetals.
- Pressed & sintered specimens: Die cavity dimensions and certain mandatory specimen limits (e.g., flatness and parallelism 0.1 mm). Micro-lamination in the gauge region shall not exceed 0.25 mm.
- Notched vs unnotched: Drawings and die recommendations provided for both forms. For notched pieces the die tooling radius must be reported because the tool radius is subject to wear.
- Stress concentration factors (Kt): Table provides Kt values vs notch radius; examples from the standard:
- r = 0.25 mm → Kt axial ≈ 4.41, Kt bending ≈ 3.11
- r = 0.45 mm → Kt axial ≈ 3.46, Kt bending ≈ 2.43
- r = 0.90 mm → Kt axial ≈ 2.52, Kt bending ≈ 1.89
- Unnotched specimen Kt ≈ 1.04–1.06
- Die design & tooling: Die material preferably hardmetal; small exit taper (recommended 0.01 per side) to aid ejection; die bore allowance for repressing (+0.5%). Dies should be supported with shrink rings (internal diameter 120 mm recommended) to minimize lateral expansion.
- Machined specimens: Grinding with a diamond wheel and longitudinal lapping/polishing is required; diameter uniformity in gauge length must be ±0.025 mm. Machined circular specimens often show 20–30% higher endurance limits compared with unmachined, as-compacted square/rectangular specimens.
- Orientation for bending tests: If unspecified, specimens are oriented so the torque vector is parallel to the pressing direction during compaction.
- Identification: Reports must state reference to ISO 3928, material type, density, dimensions, finishing treatments, die material, heat treatment state, hardness, and notch radius (if applicable).
Applications and who uses it
ISO 3928:2016 is used by:
- Powder metallurgy (PM) manufacturers and toolmakers for die design and specimen production
- Materials and mechanical testing laboratories performing fatigue testing on sintered metals
- Quality assurance, R&D and metallurgical engineers validating fatigue performance of PM components
- Designers specifying PM component testing and comparing machined vs as-sintered fatigue data
The standard helps ensure consistent specimen geometry, reliable fatigue data, and proper correlation between laboratory tests and component performance.
Related standards
- ISO 1099 - Fatigue testing, axial method
- ISO 1143 - Rotating bar bending fatigue testing
- ISO 1352 - Torque-controlled fatigue testing
- ISO 296 - Machine tool tapers (tooling interfaces)
Keywords: ISO 3928:2016, sintered metal, fatigue test pieces, powder metallurgy, die specifications, machined specimens, fatigue testing, stress concentration factor.
