ASTM B565

ASTM B565 provides a standardized method for determining the shear strength of brazed joints. Brazing is a joining technique commonly used in aerospace, automotive, HVAC, and industrial applications where high-strength, temperature-resistant joints are required. This method evaluates how well a brazed joint performs under shear loading, which is a critical mechanical property for structural integrity.

Purpose and Scope

ASTM B565 is designed to:

• Evaluate the shear strength of a brazed joint using a single-lap configuration

• Assess the quality and consistency of brazing processes

• Provide data for material selection, quality control, and product design

It applies to:

• Metals and alloys joined by brazing

• Base materials like aluminum, copper, steel, titanium, and nickel alloys

• Dissimilar metal combinations frequently used in aerospace and electronic assemblies

Equipment Required

• Universal Testing Machine (UTM):
  Must be capable of applying a controlled tensile load and measuring force accurately. A load cell appropriate for the expected shear strength range is required.

• Custom Shear Test Fixture or Grips:
  A lap shear fixture that holds the two sides of the specimen in alignment and transmits load parallel to the bond line.

• Data Acquisition System:
  To record load vs. displacement, and calculate maximum shear force.

• Specimen Alignment Tools:
  Proper alignment of the shear plane is crucial to ensure valid results.

Specimen Requirements

• Geometry:
  A typical test specimen is a single-lap joint, where two metal strips are brazed with an overlapping area.

• Dimensions:
  Common overlap areas are 12.7 mm × 25.4 mm (0.5 in × 1.0 in), though the standard allows for variations.

• Surface Prep:
  Specimens must be cleaned and brazed under controlled conditions to ensure repeatability.

• Brazing Conditions:
  Brazing filler alloy, temperature, time, and atmosphere should be reported and consistent across test specimens.

Test Procedure

1. Condition Specimens (if required):
   If post-braze heat treatments or environmental exposure are to be tested, perform these prior to testing.

2. Mount the Specimen in the UTM:
   Install the brazed specimen so that the shear plane is loaded in the direction parallel to the bonded surfaces.

3. Apply Load at a Constant Crosshead Speed:
   A recommended strain rate is typically 1.3 mm/min (0.05 in/min), but other speeds may be used depending on the application.

4. Record the Load at Failure:
   The maximum load sustained by the specimen is used to calculate shear strength.

5. Document Failure Mode:
   Determine whether failure occurred:

   • In the brazed joint (adhesive failure)

   • In the base metal (cohesive failure)

   • At the interface (mixed mode)

Final Calculation

Shear strength (τ) is calculated as:

τ = F / A

Where:

• τ = Shear strength (MPa or psi)

• F = Maximum force applied before failure (N or lbf)

• A = Area of the overlap joint (mm² or in²)

Reporting Requirements

A comprehensive ASTM B565 report should include:

• Material specifications of both base metals and braze filler

• Dimensions and overlap area of test specimens

• Brazing process parameters: temperature, atmosphere, duration

• Crosshead speed and loading configuration

• Maximum shear load and calculated shear strength

• Description of failure mode (adhesive, cohesive, interfacial)

• Number of specimens tested and statistical analysis (mean, std. dev.)

• Photographs of fracture surfaces (optional but recommended)

Common Applications

• Aerospace components: Fuel lines, turbine blades, heat exchangers

• Electronics and semiconductors: Ceramic-to-metal joints, hermetic seals

• HVAC systems: Copper and aluminum heat exchangers

• Medical devices: Stainless steel and titanium assemblies

Related and Similar Standards

If ASTM B565 doesn’t exactly match your materials or joint configurations, consider these related standards:

• AWS C3.2M/C3.2 – Standard Methods for Evaluating the Strength of Brazed Joints
  (Developed by the American Welding Society; includes multiple joint types and loading modes)

• ASTM E8 / E8M – Standard Test Methods for Tension Testing of Metallic Materials
  (Useful for base metal tensile strength, often tested alongside brazed joints)

• ASTM D1002 – Test Method for Apparent Shear Strength of Single-Lap-Joint Adhesively Bonded Metal Specimens
  (Similar shear test setup, but for adhesive bonding instead of brazing)

• ASTM D3165 – Strength Properties of Adhesives in Shear by Tension Loading of Single-Lap-Joint Laminated Assemblies
  (Also relevant for joint integrity testing in non-metallic or hybrid assemblies)

• MIL-STD-883, Method 2024 – Shear Strength for Microelectronic Devices
  (Used in the defense sector for small component joints)

Summary

ASTM B565 is the definitive standard for evaluating the shear strength of brazed joints. It provides vital data for product designers and quality engineers working with metallic joints subjected to mechanical stress. By simulating real-world shear loading, the test helps validate both brazing process quality and design performance.

This standard is widely used across aerospace, automotive, electronics, and medical device industries to ensure brazed assemblies meet strength, reliability, and regulatory standards.