Information on the most widely used ASTM standards within the materials testing industry
High Strength Bolts Testing
High strength bolts are critical fasteners widely used in steel structures, aerospace, automotive, and heavy machinery industries, where they bear high tensile, shear, or combined loads. High strength bolts testing is a set of standardized procedures to verify their mechanical properties, reliability, and compliance with design requirements. The tests cover core performance indicators such as tensile strength, yield strength, hardness, torque-tension relationship, and fatigue resistance.
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What's high strength bolts testing?
High strength bolts are critical fasteners widely used in steel structures, aerospace, automotive, and heavy machinery industries, where they bear high tensile, shear, or combined loads. High strength bolts testing is a set of standardized procedures to verify their mechanical properties, reliability, and compliance with design requirements. The tests cover core performance indicators such as tensile strength, yield strength, hardness, torque-tension relationship, and fatigue resistance.
The testing theory is based on the mechanical behavior of bolt materials under load and the load-bearing mechanism of bolted connections:
Material strength theory: High strength bolts are usually made of quenched and tempered alloy steels (e.g., ASTM A325, A490; ISO 898-1 Class 8.8/10.9). The tests verify whether the material reaches the specified yield strength (Re)) and ultimate tensile strength (Rm)) to avoid plastic deformation or fracture under working loads.
Connection reliability theory: Bolted connections rely on pre-tension force to clamp connected components, preventing slip or separation. Tests (e.g., torque-tension test, slip resistance test) ensure that the bolt can maintain stable pre-tension and that the connection does not fail under dynamic or static loads.
Fatigue failure theory: High strength bolts in dynamic load scenarios (e.g., aircraft engines, automotive chassis) are prone to fatigue cracks. Fatigue tests simulate cyclic load conditions to evaluate the bolt's service life and anti-fatigue performance.
Key Test Items and Principles
| 1 Tensile Test | Purpose: Determine the bolt's basic strength indicators, the most critical test for material qualification. Principle: Apply uniaxial tensile load to the bolt until fracture, record the load-displacement curve. Key Indicators:
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| 3 Hardness Test | Purpose: Rapid, non-destructive evaluation of material strength (hardness correlates with tensile strength for quenched and tempered steel). Principle: Use Rockwell (HRC for hard bolts) or Vickers (HV for precision) hardness tests. Test Positions: Bolt head, shank, and thread (ensure uniform heat treatment). Standard Requirements: e.g., ASTM A325 bolts require HRC 22–3 |
| 4 Torque-Preload Relationship Test | Purpose: Guide on-site installation (avoid over-tightening fracture or under-tightening slip). Principle: Record real-time tightening torque (T) and preload (F) during bolt tightening, establish the T-F curve. Key Indicator: Torque coefficient |
| 5 Fatigue Test | Purpose: Evaluate service life under cyclic loads (e.g., vibration, repeated stress). Principle: Apply sinusoidal cyclic tensile/compressive load (stress ratio R = 0.1–0.5) until fracture. Key Indicator: Fatigue life (N): Number of cycles before fracture (must meet standard minimum requirements). |
| 6 Slip Resistance Test (for Structural Bolts) | Purpose: Verify the anti-slip capacity of bolted connections (e.g., steel structure joints). Principle: Clamp two connected plates with the bolt, apply shear load, and measure the slip load (load at first plate slip). |
Main Applications
High strength bolts testing is indispensable in industries requiring reliable high-load connections:
Steel Structure Industry: Bridges, high-rise buildings, industrial frames (ISO 898-1 Class 10.9/12.9, ASTM A325/A490 bolts). Tests ensure connections resist wind, earthquake, and structural loads.
Automotive Industry: Chassis bolts, engine assembly bolts, wheel bolts. Tensile, torsion, and fatigue tests guarantee durability during driving and maintenance.
Aerospace Industry: Aircraft engine bolts, fuselage structural bolts. Strict tensile, fatigue, and torque-preload tests meet extreme environment requirements.
Heavy Machinery & Wind Power: Construction machinery hinges, wind turbine flange bolts. Torsion and slip resistance tests prevent loosening or fracture under heavy loads.
Manufacturing Quality Control: Validate production processes (heat treatment, thread rolling) via batch testing, ensuring consistent performance.
Failure Analysis: Investigate bolt fracture causes by comparing test data of failed and qualified bolts.
ISO & ASTM Standards
Standards unify test procedures, equipment requirements, and acceptance criteria for global comparability:
ISO Standards
ISO 898-1:2016: Core standard for mechanical properties of carbon/alloy steel fasteners. Specifies tensile strength, yield strength, and torsion requirements for Class 8.8–12.9 bolts.
ISO 16047:2005: Fastener torque-testing methods. Details clamping, loading speed, and data recording for torsion tests.
ISO 3269:2017: Fastener acceptance inspection. Defines sampling rules and batch qualification criteria for all tests.
ISO 6487:2017: Fastener fatigue testing. Specifies cyclic load parameters and fatigue life requirements.
ISO 14713:2016: Slip resistance of high strength bolted connections. Guides slip resistance test procedures for steel structures.
ASTM Standards
ASTM A325/A325M-23: High-strength structural bolts (120/105 ksi tensile strength). Includes tensile, hardness, and torsion requirements.
ASTM A490/A490M-23: Ultra-high strength structural bolts (150 ksi tensile strength). Strict fatigue and brittle fracture prevention criteria.
ASTM E8/E8M-23: Tensile testing of metallic materials. Specifies tensile test procedures for bolts.
ASTM E18-23: Rockwell hardness testing. Standards for bolt hardness measurement.
ASTM F1472-17: Torsional testing of fasteners. Core torsion test standard for North America.
ASTM F3125-23: Specification for high strength bolts, screws, and studs. Integrates A325/A490 requirements for unified acceptance.
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