ISO 6892金属材料の引張試験

The force measuring system of the testing machine used in ISO 6892-2 testing must be in accordance with ISO 75001-1 class 1, or better. The Instron 6800 Series offers test frames suitable for sheet metal testing (10kN) all the way up to the strongest aerospace alloys (300kN). The 6800 Series provides a superior load frame including pre-loaded bearings, precision ball screws, an extremely stiff crosshead and base beam, and low-stretch drive belts. These features contribute to an overall advanced performance, producing highly accurate results. The features also help to minimize the energy stored during a test, which is especially evident when testing high-strength metallic materials to ISO 6892-2.

As noted in the standard, during the pretest heat-up and soaking period thermal expansion can lead to compressive stresses on the specimen if a force is not applied. These 6800 Series test frames can be programmed to maintain a low, constant tensile load on the specimen, preventing this compression from occurring and ensuring good alignment of the load string once the test begins.

For testing up to 350°C, an environmental chamber can be used that typically encloses the specimens as well as the grips. For higher temperatures, more common in the testing of aerospace alloys, a furnace will be needed. Because furnaces operate at temperatures that exceed the recommended service temperature of most grips, specimens are typically coupled to Inconel pull rods. This can be accomplished using either a threaded coupler on round specimens, or a pin and clevis for flat specimens.

For specimens with gauge lengths 50 mm or smaller, temperature sensors called thermocouples are used to measure the temperature of the specimen at each end of the parallel length. For specimens of gauge length 50 mm or greater, an additional thermocouple is attached near the center of the parallel length. The furnace selected must be able to maintain the specified temperature, as measured along the test piece, within a narrow range, as specified by a table in the standard.

Each component of the temperature measuring system — including all sensors, cables, indicating device, and reference junction — must have a resolution equal to or better than 1°C and an accuracy of ±0.004 x the set temperature, or ±2°C (whichever is greater).

Instron’s 3 Zone Split Tube Furnaces, including the new 3119-160 1200°C option, ensure conformance to ISO 6892-2. Instron furnaces are manufactured with high-grade insulation that does not use refractory ceramic fiber (RFC). Each furnace is equipped with a protective shield to minimize contact for operator safety as well as for protection of the surrounding equipment.

The extensometer used for the determination of proof strength at elevated temperature must be in accordance with ISO 9513, class 1 or better, in the relevant range. For other properties determined at higher extensions, an ISO 9513 Class 2 extensometer is permitted. Extensometers used in elevated temperature testing are either self-supported on the specimen or hot mountable. Both configurations meet the requirements of the standard and offer unique benefits depending on the application. Hot-mountable extensometers are particularly valued for their consistent specimen alignment, and the ability to increase throughput on test frames configured with multiple furnaces.

Nearly all modern testing machines come with pre-installed software, and it is important that the calculations in the testing software are in compliance with ISO 6892-2 and match with existing data. Not all software packages are created equal, and it is important to know that the platform you choose provides reliable results. Thousands of customers around the globe rely on Bluehill Universal to test their material to ISO 6892-2. All calculations required in ISO 6892-2 testing are already pre-configured into Bluehill Universal, but for those who prefer to start from scratch and build their own method, the interface makes it easy for users to manually input their own calculations. The metals methods package also provides pre-built methods to all of the following standards: ISO 6892-1, ASTM E8 / E8M, ASTM A370, ASTM A615, ASTM E646, ASTM E517, EN10002, ISO 10113, and ISO 10275.

For labs seeking to increase throughput in their elevated temperature testing, Instron offers a dual furnace setup on 6800 Series high-capacity frames. The dual furnace carousel paired with a hot mountable extensometer enables one high temperature test to proceed while the next specimen is heating up.