GB/T 16865-2023Test pieces and methods for tensile test for wrought aluminium, magnesium and their alloy products (English PDF)

5.1 Testing Machine

5.1.1 The testing machine force measuring system shall be calibrated in accordance with JJG 139, JJG 475 or JJG 1063.The accuracy of the testing machine force measuring system used for the determination of room-temperature tensile mechanical properties of aluminum foil products shall reach or be superior to Level

0.5 specified in GB/T 16825.1-2022.The accuracy of the testing machine force measuring system used for the determination of mechanical properties of other products shall reach or be superior to Level 1.

5.1.2 The maximum load required for the test should be within the range of 10% ~ 90% of the maximum load of the testing machine.

5.1.3 Testing machines used for the determination of elastic modulus or mechanical properties of aviation and aerospace materials shall be inspected for coaxiality in accordance with GB/T 34104-2017.

5.2 Extensometer

5.2.1 The extensometer system shall be calibrated in accordance with JJG 762.When determining the elastic modulus, the accuracy of the extensometer shall reach or be superior to Level

0.5 specified in GB/T 12160-2019; when determining other mechanical properties, the accuracy of the extensometer shall reach or be superior to Level 1.

5.2.2 When determining the elastic modulus, the extensometer system shall be able to measure the average deformation on at least two opposite sides of the specimen. When adopting the automatic method to determine the plastic strain ratio, the extensometer system shall be able to measure the deformation in the length direction and the width direction of the rectangular specimen.

5.2.3 The gauge length of the extensometer (Le) should be greater than half of the original gauge length (L0) and not greater than the original gauge length (L0); when using an extensometer to determine the elongation after break, the gauge length of the extensometer (Le) shall be equal to the original gauge length (L0).

5.2.4 The part of the extensometer used for high-temperature tensile test or low-temperature tensile test that extends outside the heating device or cooling device shall be able to prevent interference from air flow.

5.2.5 Non-contact extensometer should be used for the determination of room-temperature tensile mechanical properties of aluminum foil.

5.3 Fixture The test fixtures can be wedge-shaped fixture (see Figure 2), flat-pushing fixture (see Figure 3), shoulder fixture (see Figure 4), collar fixture (see Figure 5), threaded fixture (see Figure 6) and pin fixture (see Figure 7), etc. The clamping surfaces of wedge-shaped fixture and flat-pushing fixture can be serrated surfaces and smooth rubber surfaces, etc.

5.4 Data Collection System When determining the elastic modulus, data shall be collected through a computer. The minimum data collection frequency (fmin) of the data collection system is calculated in accordance with Formula (1), and the value is expressed in Hertz (Hz). The calculation results are expressed to one decimal place, and numerical rounding is carried out in accordance with the stipulations of GB/T 8170.

6.3.1 Specimen selection principle

6.3.3 Extruded (or drawn and rolled) rods, wires, pipes or extruded profiles and extruded plates The specimen selection of extruded (or drawn and rolled) rods, wires, pipes or extruded profiles and extruded plates shall comply with the stipulations of Table 13.

6.4.1 General stipulations

6.4.1.1 In accordance with the sampling direction, the specimens are divided into longitudinal specimens, transverse specimens and high-direction specimens. For longitudinal specimens, the longitudinal axis of the specimens is parallel to the direction of the metal streamline; for transverse specimens, the longitudinal axis of the specimens is located on the cross section perpendicular to the metal streamline, and parallel to the long side (or cross-sectional width) direction of the cross section,

6.4.1.2 For each test, at least 2 parallel specimens shall be cut. When using preliminary tests to estimate the beam displacement rate, an additional parallel specimen shall be cut.

6.4.2 Rolled plates, strips and foils

6.4.2.1 For rolled plates, strips and foils of magnesium alloys, pure aluminum and aluminum alloys that cannot be heat-treated and strengthened, longitudinal specimens (the longitudinal axis of the specimens is parallel to the rolling direction) shall be taken. When the width of the aluminum alloy products that can be heat-treated and strengthened is not less than 230 mm, transverse specimens shall be cut (the longitudinal axis of the specimens is perpendicular to the rolling direction);

6.4.2.3 When specified in the product standards or order sheets (or contracts), for aviation products with a product thickness greater than

38.1 mm, the specimen can be cut at 1/4 of the thickness; for aviation products with a product thickness not greater than

38.1 mm, the specimen can be cut at the center of the thickness. Otherwise, when the product thickness is greater than 40 mm, the specimen shall be cut at 1/4 of the thickness; when the product thickness is not greater than 40 mm, the specimen shall be cut at the center of the thickness.

6.4.3 Extruded (or drawn and rolled) rods, wires, pipes or extruded profiles and extruded plates Along the direction of extrusion, at the front end of the extrusion, cut longitudinal specimens. When the demand-side requires cutting of transverse specimens or high-direction specimens, it shall be indicated in the order sheet (or contract). The specimen cutting of extruded or cold drawn (rolled) products shall comply with the stipulations of Table 15.

6.4.4 Forging products

6.4.4.1 Longitudinal specimens, transverse specimens and high-direction specimens shall be cut from forging products.

6.4.4.2 Specimens of forgings may be cut from an extension of the forgings, or from an additionally produced specimen piece. The cutting of the forging specimens shall also comply with the stipulations of Table 16.

6.5 Identification and Preparation of Specimens

6.5.1 Identification of specimens Each specimen shall be clearly identified, and the identification shall not affect the test.

6.5.2 Preparation of specimens

6.5.2.1 When cutting and machining specimens, sufficient machining allowance shall be left in the sample blank. The specimens shall be machined to an appropriate depth each time and thoroughly cooled (for example, using cutting fluid), so as to reduce the impact of hardening or overheating on the mechanical properties during the machining process.

6.5.2.2 After specimen machining, burrs shall be removed, and sharp edges should be chamfered.

6.5.2.3 The surface of the specimen shall be free of significant transverse tool marks, mechanical damage, obvious quenching deformation, cracks or metallurgical defects visible to the naked eye.

6.5.2.4 For rectangular specimen blanks cut from plates, strips and profiles, and arc-shaped specimen blanks cut from pipes and profiles, their original surfaces should be retained and shall not be damaged. Straightening or flattening of wires and sheet (strip) specimens cut from coils is allowed, but the straightening shall not have a significant impact on the mechanical properties of the specimens. For specimens whose elongation is not determined, the test can be carried out directly without straightening.

6.5.2.5 The preparation of aluminum foil specimens shall comply with the stipulations of GB/T 22638.11.

6.5.2.6 Except for pre-treatment membrane products, anodized membrane products, anodized composite membrane products or electrophoretic paint products, other surface-treated products shall remove the membrane layer on the surface of the specimens.

7.2.1 Requirements for rounding and error

7.2.2 Circular specimens In accordance with Formula (2), calculate the original cross-sectional area (S0) of circular specimens, expressed in (mm2).

7.2.3 Rectangular specimens In accordance with Formula (3), calculate the cross-sectional area of the three locations of the rectangular specimens, expressed in (mm2). Select the smallest area among the three locations as the original cross-sectional area (S0) of the specimens.

7.2.4 Arc-shaped specimens

7.2.4.1 In accordance with Formula (4), calculate the cross-sectional area of the three locations of the arc-shaped specimens, expressed in (mm2). Select the smallest area among the three locations as the original cross-sectional area (S0) of the specimens.

7.3.2 Other products

7.4 Selection of Fixtures Fixtures should be selected in accordance with Table 18.

7.5 Zero-point Setting of Test Force After the assembly of the clamping system is completed, and before the two ends of the specimen are clamped, set the zero-point of the force measurement system.

7.6 Specimen Clamping

7.6.1 Clamp the specimen on the testing machine and try to ensure that the longitudinal axis of the specimen coincides with the centerline of the clamping system (see Figure 1).

7.6.2 In order to obtain a straight specimen and ensure that the specimen is aligned with the chuck, a pretension force not exceeding 5% of the specified strength can be applied. For rectangular specimens or arc-shaped specimens, a positioning device should be used to ensure that the specimen is aligned with the chuck.

7.6.3 When multiple extensometers are clamped to determine the elastic modulus, the specimen can be preloaded to the upper stress limit of the evaluation area for the determination of elastic modulus. The difference between the strain increment measured by any extensometer and the average strain increment shall be within the range of 3%, otherwise, the specimen shall be re- clamped.

7.6.4 The clamping of aluminum foil specimens shall also comply with the stipulations of GB/T 22638.11.

7.7 Installation of Temperature Sensor When performing high-temperature tensile test or low-temperature tensile test, temperature sensors shall be installed. When the length of the parallel part of the specimen is not less than 50 mm, one temperature sensor shall be respectively installed at both ends and the middle of the parallel part of the specimen.

7.8 Settings of Test Temperature and Holding Time In accordance with Table 19, set the test temperature and holding time.

7.9 Extensometer Clamping and Gauge Length Correction The extensometer clamping and gauge length correction shall comply with the stipulations of Table

20.When determining the elastic modulus, the clamping position of the extensometer shall be symmetrical. When clamping a contact-type extensometer, the clamping force shall be appropriate to ensure accurate strain measurement and avoid obvious clamping marks.

7.11.5 Determination of elongation after break (A)

7.11.6 Determination of elongation (Ae) at yield point On the force-extension curve, read the extension (Le_1) corresponding to the first yield plateau, as shown in Figure

32.In accordance with Formula (17), calculate the elongation (Ae) at the yield point, expressed in (%). The calculation results shall retain two decimal places and rounded in accordance with the stipulations of GB/T 8170.