ASTM A1038 - Test Method for Portable Hardness Testing by the Ultrasonic Contact Impedance Method
ASTM A1038 Hardness Test Using Ultrasonic Contact Impedance Method (UCI Method) for Metallic Samples
Introduction
The ASTM A1038 test method is a valuable technique used to determine comparative hardness values in metallic samples through the application of the Ultrasonic Contact Impedance Method (UCI Method). This method offers the advantage of assessing hardness in positions that are challenging to access, such as tooth flanks or gear roots. It is particularly suited for measuring surface hardness conditions, making it a superficial determination that is essential for evaluating the quality and durability of metal surfaces.
Test Procedure
To conduct the ASTM A1038 hardness test, follow these steps:
Preparation: Connect the probe to the indicating unit and power on the instrument.
Probe Positioning: Hold the probe steadily, aligning its axis perpendicular to the surface of the test piece.
Loading Phase: Apply steady pressure against the test piece throughout the loading phase. Maintain the vertical position of the probe while the load is effective.
Measurement End: The instrument will signal the end of the measurement with an acoustic signal and display the hardness value.
Specimen Size
The specimen used for the ASTM A1038 hardness test consists of a probe containing a rod with a defined indenter. This indenter is instrumental in accurately assessing the hardness of the metallic surface.
Data Reporting
Hardness values obtained from ASTM A1038 testing are reported in SI units, providing a standardized measurement that is universally understood and accepted.
Error Calculation
The error (E) in the performance of the UCI hardness test concerning a standardized reference value is calculated as follows:
E = | 100 × ( x’ – xref. / xref. )
Where:
x’ = average measurements on a standard reference block.
xref = certified reference hardness reported for the standard reference block.
Conclusion
The ASTM A1038 test method employs the Ultrasonic Contact Impedance Method (UCI Method) to determine comparative hardness values in metallic samples. This technique holds significant importance in various applications, including assessing the quality and hardness of surfaces that are difficult to access.
Significance and Use
Conversion of Hardness Values: The hardness of a material is influenced by the test procedure and can be measured on different scales. To avoid the need for new hardness scales, the UCI method allows conversion into common hardness values like HV, HRC, and more.
Surface Hardness Determination: The UCI hardness test focuses solely on the hardness condition of the contacted surface. It does not provide insights into the material's subsurface properties.
Versatility: The UCI hardness test can be performed on components of various sizes and at different locations. It is particularly useful for measuring hardness in hard-to-reach positions, such as the tooth flanks or roots of gears.
Scope
The ASTM A1038 test method covers the determination of comparative hardness values using the Ultrasonic Contact Impedance Method (UCI Method). The values reported are in SI units and are considered the standard measurement for hardness evaluation. This method ensures a consistent and reliable approach to assessing the hardness of metallic surfaces across various applications.