Overview
EN 15865:2009 is a European standard developed by the CEN Technical Committee on Adhesives. It specifies a test method for determining the torque strength of anaerobic adhesives applied to threaded fasteners. This standard modifies the ISO 10964:1993 method and is used primarily to evaluate the securing and locking effectiveness of anaerobic adhesives in threaded assemblies. The standard is applicable for comparative assessments and may also be adapted to other adhesives suitable for similar use.
Key Topics
Scope and Purpose
- Designed for assessing the locking effect of anaerobic adhesives in threaded fasteners.
- Enables comparative evaluation of adhesive performance in preventing loosening due to torque.
- Applicable to different types of adhesives when suitable.
Terminology and Definitions
- On torque (ΤON): Maximum torque to screw a nut onto a pre-coated bolt.
- Input torque (ΤIN): Torque applied to create or increase axial load.
- Breakaway torque (ΤBA): Torque needed to initially break the bond during unscrewing.
- Breakloose torque (ΤBL): Torque required to eliminate axial load in a preloaded assembly.
- Prevailing torque (ΤP): Torque after initial bond breakage, typically measured at a 180º nut rotation.
Test Principles
- The test determines torque values required to unscrew bonded bolt and nut assemblies.
- Measurements include breakage of adhesive bonds and the torque necessary for continued unscrewing.
- Tests performed on unseated (loose fit) and seated (preloaded) assemblies.
Test Equipment and Procedure
- Uses a test machine with:
- Clamping for bolt heads.
- A nut-turning device at constant speed.
- Accurate torque measurement tools, either with graphic recording or direct reading.
- Test specimens typically include M10 x 38 bolts and nuts of property class 8.8, conforming to EN ISO fastener standards.
- Adhesive application involves coating bolts and nuts with enough adhesive to cover the nut height plus two threads.
- Assembly and curing are performed per adhesive manufacturer guidelines.
- Testing speed commonly set between 2–10 rotations per minute, with torque values recorded precisely.
Reporting and Quality Control
- Comprehensive test report requirements include:
- Adhesive identification and batch details.
- Specimen size, preparation, and conditioning methods.
- Test conditions such as torque input, testing speed, and equipment used.
- Results presenting average torque values and standard deviations.
- Important for ensuring consistency and reproducibility in adhesive performance evaluation.
Applications
- Quality assurance in fastening systems: Ensuring reliability of anaerobic adhesives used in automotive, aerospace, electronics, and machinery industries.
- Product development and certification: Manufacturers can benchmark adhesive formulations against standardized torque strength values.
- Comparative testing: Selection and validation of adhesives for locking bolts and nuts in critical mechanical assemblies.
- Safety and maintenance: Preventing loosening or failure of threaded connections under operational stresses by verifying adhesive torque capacities.
Related Standards
- EN ISO 10964:1993 (modified): Original international standard on torque strength testing for anaerobic adhesives, superseded by EN 15865:2009.
- EN ISO 898-1:2009: Mechanical properties of fasteners – bolts, screws, studs with specified property classes.
- EN 20898-2: Mechanical properties of nuts with specified proof load values.
- EN ISO 291: Standard atmospheres for conditioning and testing plastics, relevant for specimen environment control.
- EN ISO 898-6: Mechanical properties of fine pitch thread nuts, complementing fastener property specifications.
By adhering to EN 15865:2009, companies and testing laboratories can ensure robust evaluations of anaerobic adhesives’ torque strength on threaded fasteners-enhancing product safety, reliability, and performance consistency across various industrial sectors.