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GB/T 16865-2023 PDF in English


GB/T 16865-2023 (GB/T16865-2023, GBT 16865-2023, GBT16865-2023)
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GB/T 16865-2023: PDF in English (GBT 16865-2023)

GB/T 16865-2023
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 77.040.10
CCS H 22
Replacing GB/T 16865-2013
Test Pieces and Methods for Tensile Test for Wrought
Aluminum, Magnesium and Their Alloy Products
ISSUED ON: AUGUST 6, 2023
IMPLEMENTED ON: MARCH 1, 2024
Issued by: State Administration for Market Regulation;
Standardization Administration of the People’s Republic of China.
Table of Contents
Foreword ... 3
1 Scope ... 6
2 Normative References ... 6
3 Terms and Definitions ... 7
4 Method Overview ... 7
5 Instruments and Equipment ... 8
6 Specimens ... 13
7 Test Procedures ... 42
8 Result Determination ... 64
9 Test Report ... 65
Appendix A (informative) Estimation Method for Beam Displacement Rate ... 67
Test Pieces and Methods for Tensile Test for Wrought
Aluminum, Magnesium and Their Alloy Products
1 Scope
This document specifies the specimen requirements and test methods for the tensile test of
wrought aluminum, magnesium and their alloy products.
This document is applicable to the room-temperature, high-temperature and low-temperature
tensile test of wrought aluminum, magnesium and their alloy plates, strips, foils, pipes, rods,
profiles, wires, forgings and other processed products.
2 Normative References
The contents of the following documents constitute indispensable clauses of this document
through the normative references in the text. In terms of references with a specified date, only
versions with a specified date are applicable to this document. In terms of references without a
specified date, the latest version (including all the modifications) is applicable to this document.
GB/T 3246 (all parts) Inspection Method for Structure of Wrought Aluminum and Aluminum
Alloy Products
GB/T 8170 Rules of Rounding off for Numerical Values & Expression and Judgement of
Limiting Values
GB/T 10623 Metallic Material - Mechanical Testing - Vocabulary
GB/T 12160-2019 Metallic Materials - Calibration of Extensometers Systems Used in Uniaxial
Testing
GB/T 16825.1-2022 Metallic Materials - Calibration and Verification of Static Uniaxial Testing
Machines - Part 1: Tension / Compression Testing Machines - Calibration and Verification of
the Force-measuring System
GB/T 22638.11 Test Methods for Aluminum and Aluminum Alloy Foils - Part 11:
Determination of Mechanical Properties
GB/T 34104-2017 Metallic Materials - Verification of the Alignment of Testing Machines
JJG 139 Tension, Compression and Universal Testing Machines
JJG 475 Electronic Universal Testing Machine
JJG 762 Extensometer
F---force;
CL---the centerline of the clamping system and the longitudinal axis of the specimen;
1---fixture;
2---specimen;
3---extensometer.
Figure 1 -- Schematic Diagram of Tensile Test
5 Instruments and Equipment
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. The coaxiality of the testing machines used for the determination of elastic
modulus shall reach or be superior to Level 5. The coaxiality of the testing machines used for
the determination of mechanical properties of aviation and aerospace materials shall reach or
be superior to Level 10.
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. The extensometer used to measure the deformation in the width direction of the
specimen should be able to measure the average deformation at both ends of the gauge length
and the three widths in the middle.
7.1.6 For full cross-section specimens with shapes other than circular, rectangular and ring-
shaped, when the original cross-sectional area of the specimens is calculated using the actual
measurement method, the specimen size measurement method shall be agreed upon by both the
supply-side and the demand-side, or a cross-section scanner may be used for automatic
measurement.
7.1.7 When determining the plastic strain ratio of the material, measure the width at both ends
and the middle of the gauge length of the rectangular specimens; the accuracy shall be not
greater than 0.005 mm. Take the average value of the three widths as the average original width
(𝑏0) of the specimens; measure the original thickness (a0) at both ends and the middle of the
gauge length of the rectangular specimens; the accuracy shall be not greater than 0.001 mm.
The range of the three thicknesses should not exceed 0.013 mm. The specimens are allowed to
be machined to comply with the requirements for thickness range. When adopting the artificial
method to determine the plastic strain ratio, the original gauge length (L0) shall also be measured;
the measurement accuracy shall be not greater than 0.01 mm.
7.2 Calculation of Original Cross-sectional Area (S0) of Specimens
7.2.1 Requirements for rounding and error
7.2.1.1 When calculating the area of a circle, the constant  must be taken to at least four
significant figures.
7.2.1.2 The calculation results of the original cross-sectional area (S0) of the specimen shall
retain four significant figures, and the numerical rounding shall be carried out in accordance
with the stipulations of GB/T 8170.
7.2.1.3 The determination error of the original cross-sectional area of the specimen shall be not
greater than 1%, and the determination error of the original cross-sectional area of specimens
with a thickness less than 0.3 mm shall be not greater than 2%.
7.2.2 Circular specimens
In accordance with Formula (2), calculate the original cross-sectional area (S0) of circular
specimens, expressed in (mm2).
Where,
d0---the original diameter of the specimen, expressed in (mm).
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.
materials have different sensitivities to tensile rate. The selection of test rate shall be determined
in accordance with the material. When the product standard does not specify the setting method
for the test rate, the test rate recommended in 7.10.2 ~ 7.10.4 shall be used for testing. The
tensile test rate of the arbitration test is determined by the demand-side and the supply-side
through negotiation.
7.10.2 Strain rate2)
7.10.2.1 Room-temperature tensile test
7.10.2.1.1 Aviation materials
Adopt a strain rate ( ) of 0.000083 s1 (with a relative error of 40%) to perform the tensile
test, until the specified non-proportional elongation strength is determined. Afterwards, adopt
a strain rate not exceeding 0.0067 s1 to continue the test.
7.10.2.1.2 Aluminum foil
The selection of the test rate for the room-temperature tensile mechanical properties of
aluminum foil shall be carried out in accordance with the stipulations of GB/T 22638.11.
7.10.2.1.3 Other products
In accordance with different determination items, determine the strain rate:
---When it is necessary to determine the elastic modulus, adopt a strain rate ( ) of
0.000083 s1 (with a relative error of 40%) to perform the tensile test, until the elastic
modulus is measured. Then, adopt a strain rate ( ) of 0.00025 s1 (with a relative error
of 20%) to continue the tensile test, until the specified non-proportional elongation
strength is determined. Afterwards, adopt a strain rate ( ) not exceeding 0.0067 s1 to
continue the test.
---When it is not necessary to determine the elastic modulus, adopt a strain rate ( ) of
0.00025 s1 (with a relative error of 20%) to perform the tensile test, until the specified
non-proportional elongation strength is determined. Afterwards, adopt a strain rate ( )
not exceeding 0.0067 s1 to continue the test.
---When neither the elastic modulus nor the specified non-proportional elongation strength
is determined, adopt a strain rate ( ) not exceeding 0.0067 s1 to perform the tensile
test.
7.10.2.2 High-temperature tensile test
Adopt a strain rate ( ) of 0.000083 s1 (with a relative error of 40%) to perform the high-
temperature tensile test, until the specified non-proportional elongation strength is determined.
Afterwards, adopt a strain rate ( ) of 0.00083 s1 (with a relative error of 20%) to continue
2) If the extensometer is removed after determining the specified non-proportional extension strength, the test may
be continued using the beam displacement rate.
the test.
7.10.2.3 Low-temperature tensile test
Adopt a strain rate ( ) of 0.000083 s1 (with a relative error of 40%) to perform the low-
temperature tensile test, until the specified non-proportional elongation strength is determined.
Afterwards, adopt a strain rate ( ) of 0.0067 s1 to continue the test.
7.10.3 Stress rate
Adopt a stress rate ( ) of 2 MPa/s ~ 12 MPa/s to perform the room-temperature tensile test,
until the specified non-proportional elongation strength is determined. Afterwards, adopt a
beam displacement rate (vc) not exceeding 0.48 L0/min to continue the test. A constant beam
displacement rate should be maintained, so that the stress rate in the elastic deformation stage
of the specimen complies with the requirements. When the test rate is controlled in a closed
loop through the force sensor signal, after determining the specified non-proportional
elongation strength, the control mode shall be switched in time, so as to prevent the beam
displacement rate of the testing machine from being too fast or even out of control.
7.10.4 Beam displacement rate
In accordance with the strain rate ( ) specified in 7.10.2, and Formula (7), calculate the beam
displacement rate (vc), expressed in (mm/s). The calculation result shall retain two significant
figures and rounded in accordance with the stipulations of GB/T 8170. Or the beam
displacement rate can also be estimated with reference to Appendix A.
Where,
---the strain rate, expressed in (s1);
Lc---the parallel length, expressed in (mm).
7.11 Determination of Mechanical Properties
7.11.1 Specimen loading
7.11.1.1 Start the testing machine, load the specimen, and when determining the elastic modulus,
the loading of the specimen should be repeatedly performed for at least three times. If it is
necessary to simultaneously determine other mechanical properties, such as: specified non-
proportional elongation strength and tensile strength, loading may be performed only once; it
is also feasible to determine the elastic modulus after three loadings, and then, continuously
apply the load during the last loading, until the other required mechanical properties are
determined.
7.11.1.2 When determining the plastic strain ratio through the artificial method, stretch the
specimen, until it reaches the specified plastic (engineering) strain; when only the elastic
Description of indexes:
R---the stress;
e---the strain;
Rm---the tensile strength;
mE---the slope of the elastic part of the stress-strain curve;
Ag---the plastic elongation at maximum force;
1---the lower limit of the regression interval;
2---the upper limit of the regression interval.
Figure 36 -- Schematic Diagram of Determining the Value Range on the Stress-strain
Curve Based on the Regression Interval
7.11.10.1.2 The value n is related to the specified regression interval. The regression interval
used to determine the value n can be listed in the record or report in a table, or the regression
interval can also be marked with a subscript. For example, n515 represents the value n calculated
in the range of plastic (engineering) strain (ep) of 5% ~ 15%.
7.11.10.1.3 The plastic (engineering) strain range specified in the product standard, or order
sheet (or contract) shall be used as the regression interval. The regression interval shall be no
less than 2%. When the product standard or order sheet (or contract) specifies the value n for
determining a single plastic (engineering) strain level, a 2% strain range with the strain level as
the midpoint shall be selected as the regression interval, for example, the regression interval of
5% strain is 4% ~ 6% strain range. When the plastic (engineering) strain range or a single plastic
(engineering) strain level is not specified in the product standard or order sheet (or contract),
the entire uniform plastic (engineering) strain range should be selected for calculation.
7.11.10.1.4 The upper limit of the plastic (engineering) strain range used to calculate the value
n shall not be greater than the plastic elongation at maximum force (Ag). When the Ag of the
specimen is less than the upper limit of the strain range specified in the product standard or
order sheet (or contract), it cannot be used for the calculation of the value n. However, when
the demand-side and the supply-side agree and indicate it in the product standard or order sheet
(or contract), the Ag of the specimen can be used as the upper limit of the plastic (engineering)
strain range to calculate the value n.
7.11.10.2 Calculation of strain hardening index (value n)
7.11.10.2.1 On the stress-strain curve, determine the lower limit (e1) and upper limit (e2) of the
engineering strain corresponding to the upper and lower limits of the plastic (engineering) strain
of the regression interval.
7.11.10.2.2 In the range of e1 ~ e2 on the stress-strain curve, select at least 5 data points at equal
passing through the origin of the regression interval, and the numerical value is
dimensionless; then, in accordance with Formula (30), calculate the value r, and
numerical value is dimensionless. The calculation results shall retain two decimal
places and rounded to the nearest multiple of 0.05 in accordance with the
stipulations of GB/T 8170.
 From the test record, select the specified plastic (engineering) strain interval.
When the elastic strain in the length direction of all points in the interval is less
than 10% of the engineering strain, the total true strain (L) in the length direction
of the specimen can be calculated in accordance with Formula (10), and the
numerical value is dimensionless; in accordance with Formula (27), calculate the
total true strain (b) in the width direction of the specimen, and the numerical value
is dimensionless; in accordance with Formula (31), calculate the slope mr of the
best-fit straight line passing through the origin in the regression interval, and the
numerical value is dimensionless; then, in accordance with Formula (30), calculate
the value r, and the numerical value is dimensionless. The calculation results shall
retain two decimal places and rounded to the nearest multiple of 0.05 in accordance
with the stipulations of GB/T 8170.
7.11.11.3 Result expression
7.11.11.3.1 Expression of plastic strain ratio (value r)
The value r is related to the sampling direction of the specimen, and the specific plastic
(engineering) strain value (or interval). When recording or reporting, the specimen direction
and the specified plastic (engineering) strain value (or interval) can be listed in the table, or a
subscript can be used to identify the specimen direction and the specified plastic (engineering)
strain value (or interval).
EXAMPLE:
For example, r0/10 signifies the value r determined when the specimen direction is parallel to the rolling
direction, and the plastic (engineering) strain (ep) is 10%; r90/8-12 signifies the value r when the specimen
direction is perpendicular to the rolling direction, and the plastic (engineering) strain (ep) is in the range
of 8% ~ 12%.
7.11.11.3.2 Weighted average of plastic strain ratio (𝒓) and plastic strain ratio anisotropy
(r)
Under the same plastic (engineering) strain value (or interval), determine the value r of the
specimen in the three directions of 0, 45 and 90 (r0, r45 and r90 respectively). In accordance
with Formula (32), calculate the weighted average of the plastic strain ratio (𝑟 ), and the
numerical value is dimensionless. The calculation results shall retain two decimal places and
rounded to the nearest multiple of 0.05 in accordance with the stipulations of GB/T 8170. In
accordance with Formula (33), calculate the plastic strain ratio anisotropy (r), and the
numerical value is dimensionless. The calculation results shall retain two decimal places and
rounded to the nearest multiple of 0.05 in accordance with the stipulations of GB/T 8170.
NOTE: the value r in the three directions is determined at the same plastic (engineering) strain
value (or interval), and the symbol indicating the plastic (engineering) strain value (or
interval) in the subscript is omitted from the Formula.
8 Result Determination
8.1 When one of the following circumstances occurs in the test, the test results are invalid, and
the same quantity of specimens shall be taken from the same batch of materials for a re-test:
---The specimen has a poor machined surface, and the size does not comply with the
requirements, or its performance changes due to poor modes of machining;
---The test method is incorrect or the test equipment fails;
---When determining the elastic modulus, multiple different evaluation areas were selected,
but none of them could satisfy the determination coefficient r2  0.9995;
---When determining the value n, the Ag of the specimen is less than the upper limit of the
plastic (engineering) strain range specified in the product standard or order sheet (or
contract);
---When determining the value r, the Ag of the specimen is less than the plastic (engineering)
strain value (or upper limit of the interval) for the determination of the value r specified
in the product standard or order sheet (or contract);
---When determining the value r, the specimen laterally bends during the test (that is, the
middle part of the width of the parallel part of the rectangular specimens bulges in the
direction perpendicular to the specimen plane, and the cross section is similar to an arc-
shaped specimen);
---The fracture of the specimen is not within the middle area shown in Figure 37, and the
elongation after break is lower than the value specified in the product standard. In
addition, the tensile fracture is inspected in accordance with GB/T 3246.1 and (or)
e) Test rate method;
f) One or several of tensile strength, specified non-proportional elongation strength,
elongation after break, elongation at yield point, total elongation at maximum force,
plastic elongation at maximum force, reduction of area, elastic modulus, strain
hardening index, and plastic strain ratio;
g) Test equipment;
h) Test temperature;
i) Extensometer clamping and gauge length correction methods for high-temperature
tensile test or low-temperature tensile test;
j) Type of extensometer system when determining elastic modulus;
k) The number of loadings when determining the elastic modulus, and the elastic
modulus value determined for each loading;
l) The minimum stress value, maximum stress value and the number of stress-strain data
pairs in the evaluation range when determining the elastic modulus,
m) Coefficient of determination when determining the elastic modulus,
n) Plastic (engineering) strain range when determining the strain hardening index;
o) The number of data points for calculating the strain hardening index (which can be
omitted when using all data points in the regression interval) and the calculation
method (using the true plastic strain or total true strain for calculation);
p) The plastic (engineering) strain value or plastic (engineering) strain range when
determining the plastic strain ratio;
q) The determination method when determining the plastic strain ratio (artificial method
or automatic method);
r) The calculation method when determining the plastic strain ratio by the automatic
method (using the true plastic strain or total true strain for calculation);
s) Reasons for supplementary test;
t) Reasons for re-performed test;
u) Serial No. of this document;
v) Test personnel and test time.
Appendix A
(informative)
Estimation Method for Beam Displacement Rate
A.1 Estimation through Preliminary Tests
In accordance with the estimated beam displacement rate, carry out a preliminary test. Then, in
accordance with Formula (A.1), calculate the beam displacement rate (vc) corresponding to the
specified strain rate, expressed in (mm/s). The calculation results shall retain two significant
figures and rounded in accordance with the stipulations of GB/T 8170.
Where,
vc_p---the beam displacement rate of the preliminary test, expressed in (mm/s);
---the specified strain rate when determining the specified non-proportional elongation
strength, expressed in (s1);
---the actual strain rate of the preliminary test when determining the specified non-
proportional elongation strength, expressed in (s1).
A.2 Estimation through Testing Stiffness and Material Properties
A.2.1 When the stiffness of the testing machine (CM) is known, and the slope (m) at the specified
non-proportional elongation strength on the stress-strain curve of the specimen can be roughly
determined, the beam displacement rate (vc) can be calculated in accordance with Formula (A.2),
expressed in (mm/s). The calculation results shall retain two significant figures and rounded in
accordance with the stipulations of GB/T 8170. The values of m and CM within the elastic range
on the stress-strain curve shall not be used, especially when the stiffness of the test equipment
is non-linear (for example, when a wedge-shaped fixture is used), m and CM shall take a value
within the range around the specified non-proportional elongation strength.
Where,
m---the slope at the specified non-proportional elongation strength on the stress-strain curve,
expressed in (MPa);
CM---the stiffness of the test equipment, expressed in (N/mm).
A.2.2 After conducting the tensile test at a slow and constant beam displacement rate, determine
the slope (m) and strain rate ( ) at the specified non-proportional elongation strength on the
stress-strain curve of the specimen. Then, in accordance with Formula (A.3), calculate the
......
 
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