Overview
ISO 2739:2012 is an international standard published by the International Organization for Standardization (ISO) that specifies a precise method for determining the radial crushing strength of sintered metal bushings. These bushings are hollow cylindrical components made from pure or alloyed metal powders through powder metallurgy processes. The standard outlines a consistent test procedure vital for assessing the mechanical integrity and quality of sintered metal parts used in various industrial applications.
This third edition replaces the previous 2006 version, incorporating technical revisions to improve accuracy and applicability. The method described is essential for manufacturers and quality assurance professionals to ensure product reliability and performance under radial loads.
Key Topics
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Test Principle
The test involves applying a continuously increasing radial load on a hollow cylindrical sintered metal bushing until breakage or a specified deformation limit is reached. The maximum load at failure is used to calculate the radial crushing strength.
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Test Specimen Requirements
Specimens must be sintered hollow cylinders without flanges, notches, or holes. They can be machined or oil-impregnated, but machining may affect test results. Precise dimensional measurements (diameter, length, and wall thickness) are required for accurate calculations.
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Apparatus and Setup
The apparatus includes a pressing machine capable of applying radial loads, highly accurate load-measuring devices, and two flat steel loading plates ensuring parallel contact with the specimen.
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Measurement Procedure
The bushing is placed horizontally between loading plates. Load is applied at a controlled speed not exceeding 5 mm/min until fracture or load drop occurs, recording the maximum load to an accuracy of 0.1%.
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Calculation of Radial Crushing Strength
Radial crushing strength (K) in N/mm² is calculated using the formula:
K = F / (2 × L × e × (D - e))
where F = maximum load (N), L = length (mm), D = external diameter (mm), and e = wall thickness (mm). The formula is valid if wall thickness to diameter ratio (e/D) is less than 1/3.
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Precision and Accuracy
The standard provides repeatability and reproducibility data, indicating the expected accuracy within and between laboratories to ensure consistent quality assessment.
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Test Reporting
Test reports must reference ISO 2739:2012 and include specimen identification, condition (sintered, sized, machined, or oil-impregnated), test results, and any test anomalies or optional procedures used.
Applications
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Quality Control in Powder Metallurgy
ISO 2739:2012 is critical for manufacturers of sintered metal bushings to verify mechanical strength characteristics during production and before delivery.
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Design and Material Selection
Engineers use radial crushing strength data to select materials and design bushings that withstand operational stresses in automotive, aerospace, industrial machinery, and other sectors.
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Research and Development
This standard supports R&D teams in evaluating new sintered materials and processing methods by providing a reliable test method for mechanical performance.
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Comparative Analysis
Enables benchmarking of sintered parts from different suppliers or production batches for consistent performance and compliance with industry specifications.
Related Standards
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ISO/TC 119 - Powder Metallurgy
The technical committee responsible for developing standards related to powder metallurgy, including sampling, testing methods, and specification standards.
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MPIF Standard 55
Provides related guidance on determining radial crush strength specific to powder metallurgy test specimens, often referenced for technical agreement.
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ISO/IEC Directives, Part 2
Defines the rules for drafting international standards, ensuring consistency and clarity across ISO documents.
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Other Metallurgical Testing Standards
Standards related to tensile strength, hardness, and fatigue testing of sintered metals complement ISO 2739 by providing a holistic mechanical property profile.
By implementing ISO 2739:2012, manufacturers and users of sintered metal bushings ensure products meet stringent mechanical requirements, supporting reliability and safety in demanding applications. This standard delivers a practical, replicable method to assess radial crushing strength-an essential parameter in powder metallurgy components.
