ASTM D638 is a standard test method developed by ASTM International that outlines the procedure for conducting a tensile test on plastic materials. This test method is widely used to determine various mechanical properties of plastics, including tensile strength, elongation at break, modulus of elasticity, and yield strength.
The ASTM D638 test involves subjecting a standardized specimen of the plastic material to an applied tensile force until it fractures or breaks. The test is typically performed using a universal testing machine equipped with suitable grips to securely hold the specimen. The test machine applies a gradually increasing force to the specimen in a constant rate of crosshead displacement or constant rate of strain until failure occurs.
During the test, the load and elongation or displacement are recorded continuously. These measurements are used to determine key mechanical properties of the plastic material under tensile stress, such as maximum tensile strength, strain at break, and Young's modulus.
The ASTM D638 standard provides detailed instructions for specimen preparation, test conditions, and calculation methods. It ensures consistent testing practices and facilitates meaningful comparison of results across different laboratories and materials. However, it is important to note that ASTM D638 is specifically for plastic materials and may not be applicable to other materials such as metals or textiles.
When conducting a tensile test according to ASTM D638, it is crucial to follow the standard test method precisely to ensure accurate and reliable results.