Steel is widely used
in various fields of life, architecture, bridges, scientific research, etc. The
quality of steel is subject to a variety of mechanical tests to ensure their
strength, elastic constants and other material properties. And their
performance in various practical conditions and environments. Tensile testing
is one of them.
Tensile test is a
test method for determining the properties of a material under axial tensile
load. The data obtained from the tensile test can determine the material's
elastic limit, elongation, elastic modulus, proportional limit, area reduction,
tensile strength, yield point, yield strength, and other tensile properties.
The tensile test of steel meets the ASTM E-8 standard.
There are 4 stages in
the tensile test procedure:
1, the elastic stage
(the stress and strain ratio increases, the unloading load can be restored)
2, the yield phase
(the increase in strain is greater than the increase in stress, began to
produce plastic deformation, the lower stress is the yield point)
3, strengthening
phase (strain increase stress also increases, the maximum is the ultimate
tensile strength)
4, necking phase
(strain increased stress, resulting in "neck" fracture)
Tensile test
procedure of steel
Step 1. Prepare the
test piece. The ruler is used to scribe a circle in the original gauge range
(or punch a small punch with a small steel) to divide the gauge length into ten
equal lengths. Use a vernier caliper to measure the diameter at two ends of the
specimen's original gauge length and in the middle at two mutually
perpendicular directions. Take the arithmetic mean value as the diameter of the
section at that location, and then use the minimum value of the three section
diameters to calculate The original section area A of the test piece.
Step 2. Adjust stell tensile
test machine. Calculate the maximum load of the specimen based on the tensile
strength σb of the steel and the original cross-sectional area, configure the
corresponding pendulum, and select the appropriate force measurement dial.
Start the tester and raise the worktable by about 10mm to eliminate the
influence of the worktable system's own weight. Adjust the active pointer to
the zero point, move the pointer and the active pointer closer, and adjust the
automatic drawing device.
Step 3. Set up the
specimen. First clamp the test piece in the upper clamp, then move the lower
clamp to the proper clamping position, and finally clamp the lower end of the
test piece.
Step 4. Check and test
run. Check the above steps to complete the situation. Start the tester, preload
a small amount of load (load corresponding to the stress can not exceed the
material limit of the ratio), and then unloaded to zero to check whether the
test machine is working properly.
Step 5. Test. Turn on
the tester and slowly and evenly load. Observe the rotation of the force hand
and the drawing of the drawing device. Pay attention to capture the yield load
value, record it to calculate the stress value σS at the yield point, pay
attention to observe the slip phenomenon in the yield phase. After the yield
phase, the loading speed can be faster. When the maximum value is to be
reached, observe the "necking" phenomenon. Stop the test piece
immediately after the break and record the maximum load value.
Step 6. Remove the test piece and recording paper.
Tension fixture
The tension clamp
itself is a locking mechanism. There is no fixed pattern in the structure.
According to different specimens and test force size, there is a great
difference in structure. The test specimen with large test force generally
adopts inclined clamping structure. As the test force increases, the clamping
force increases. , Shoulder specimens using suspension structure.
Related test machines
Hydraulic universal
tensile testing machine can achieve closed-loop control of various modes such
as constant force, constant stress, constant deformation and constant speed,
and complete the tensile, compression, bending and shear tests of metal
materials and non-metal materials. Microcomputer-controlled electro-hydraulic
servo universal testing machine adopts the under-cylinder under the fuel tank,
equipped with the electro-hydraulic servo oil source and the independent
low-noise clamping oil source imported from the Italian oil pump motor group
and servo valve. Full digital program-controlled amplifier with intelligent
control system setting expert system.