ASTM A340: Magnetic Terminology Testing Services

Scope

ASTM A 340 provides standardized symbols and definitions for all magnetic quantities, material properties, and test parameters for DC and AC magnetic tests on ferromagnetic and soft magnetic materials. This standardizes the interpretation, reporting, and comparison of magnetic material property data.

ASTM A 340 magnetic testing terminology covers:

• ASTM A340 is a terminology standard. Its content is symbols, definitions, and conversion information, not a measurement procedure.
• Full title: Standard Terminology of Symbols and Definitions Relating to Magnetic Testing, published under the fixed designation A340.
• Subcommittee A06.92 on Terminology and Definitions develops it, within ASTM Committee A06 on Magnetic Properties.
• Committee A06 covers the development of nomenclature, definitions, test methods, and specifications for materials used in magnetic applications; A340 is its core glossary.
• A340-23a is the edition current at the time of writing. ASTM lists it as active, and it supersedes A340-23.
• Editions reviewed open with a table of symbols and their corresponding terms, then move on to an alphabetical set of definitions of magnetic testing terms.
• Among the many defined terms are the forms of permeability, coercive field strength, remanence, core loss, saturation induction, and hysteresis.
• Both direct-current and alternating-current magnetic quantities are addressed across soft magnetic materials and other magnetic materials.
• An appendix of selected conversion factors, found in the editions reviewed, relates SI, CGS electromagnetic, and customary magnetic units.
• No pass or fail criteria here. A340 also doesn’t define specimen preparation, apparatus, or test conditions, which belong to the individual test methods and product specifications.

Applications

• Consistent symbols and units in magnetic test reports for electrical steels, soft magnetic alloys, and other magnetic materials.
• Interpreting results from Epstein frame, toroidal core, ring specimen, and hysteresis graph measurements.
• A shared vocabulary for purchase agreements and material specifications that reference magnetic properties.
• When suppliers, customers, and laboratories work from different conventions, A340 helps reconcile data reported in different unit systems.
• Training. Engineers and technicians get an authoritative reference for the meaning of magnetic quantities.
• Settling disputes over what a reported property, such as permeability or core loss, actually represents.

Benefits

• Less ambiguity, since every reported magnetic quantity ties back to a recognized definition and symbol.
• Results are easier to compare between laboratories, suppliers, and customers.
• Converting between SI, CGS, and customary units gets simpler when data must be reconciled.
• Reports carry more credibility when the terminology is anchored to an ASTM committee consensus document.
• Buyers and engineers can write clearer specifications that cite the correct quantity for the intended property.
• Review cycles run shorter. Fewer questions come up about what the reported values mean.