Scope:

The ASTM D2557 test technique is used for determining the comparative shear strength of adhesives for bonding metals when tested on a standard specimen and under specified preparation and testing conditions at extreme subzero temperatures. This test procedure is performed in the temperature range of -267.8°C (-450°F) to -55°C (-67°F). For homogeneous sets of conditions, this test method can be used to compare the tensile shear strengths of various adhesives, surface preparations, and substrates. This test method can also be used to see how different surface preparations, substrates, and adhesive systems affect the adhesive joint’s durability at subzero temperatures.

Procedure:

The specimens are tested using the ASTM D2557 test process, which involves tension loading after conditioning. The specimens are placed in the testing machine’s pin-type grips and chilled by being totally surrounded by a low-temperature fluid (liquid or gas). On a dummy test specimen with two thermocouples positioned in the geometric center of the bond, the time required to reach the desired test temperature is determined. One thermocouple is embedded in the middle of the bond, while the other is overlaid and bonded or spot welded to the outer surface. The test specimens are immersed in liquids for 5 minutes longer than the time needed to  achieve equilibrium, then tested as follows, as per the ASTM D2557 test method: 

• There must be no slack in the test fixture right before applying load; if a preload is used, it must not exceed 345 kPa (50 psi) at room temperature. 

• When utilizing a gaseous coolant, the temperature is controlled via a thermocouple attached to the exterior surface of the test specimen in the bond area. 

• The test temperature tolerance must be within 1%. 

• At a rate of 8.3 to 7 MPa (1200 to 1400 psi)/min, the test specimen is loaded to failure.

Video 01: Shear strength adhesive testing

Specimen size:

The ASTM D2557 specimens are cut from panels and are bonded, spot welded, or mechanically attached. 

Data:

According to ASTM D2557, all fracture loads must be stated in megapascals (pounds per square inch) and reported to three significant figures if available.

Conclusion:

The ASTM D2557 test technique is used for determining the comparative shear strength of adhesives for bonding metals when tested on a standard specimen and under specified preparation and testing conditions at extreme subzero temperatures.