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1.Tension
Testing
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Tension test is used to ascertain several mechanical
properties. A specimen is deformed usually
to fracture with a gradually increasing tensile
load that is applied uniaxially along the long axis
of a specimen. Tensile testing is performed to determine
the yield strength, tensile strength, and elongation
of steel sheet. |
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c. Yield Ratio : (Yield point/tensile strength)
Low yield ratio means a wide difference between
tensile strength and yield point. Greater
difference translates into better workability
of sheets.
d. Modulus of Elasticity
It represents the "stiffness" of
the material, that is, resistance to elastic
strain. This manifests itself as the amount
of deformation in normal use below the yield
strength and the "springiness" of
material during formin
e. n-Value (Modulus of Work Hardening)
This is measured when the stress- strain curve
approximates .
Workability is proportionate to the n-value.
f. r-Value (Modulus of Plastic Deformation)
In wo / w
---------
In to / t
wo, w= width before and after testing, respectively
to, t=thickness before and after testing,
respectively
Surface shrinkage in the direction of thickness
is in an inverse relationship with the r-value
and the shrinkage in the direction of width
is directly proportionate to the r-value.
The higher the value, the less susceptible
to fracture, hence better drawability.
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4.DBTT Test:
Ductile to Brittle Transition test
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-Test Flow : Cup Forming (Blanking, Punching)
Temperature Change Drop
Weight Test
Inspect for brittle fracture (Transition temperature
is the lowest temperature without fracture.)
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5.DBTT Test Conditions
(No-trimming after Forming Cup)
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Classification
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Detail Item
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Conditions
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Classification
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Detail Item
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Conditions
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Forming Conditions
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Blank Dia.(mm)
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96
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Drop Weight Test
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Load (kgf)
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4.44
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Punch Dia.(mm)
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50
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Drop Heigh (m)
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0.9
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Punch type
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Flat Cup
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Weight type
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Cylinder
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Drawing Ratio
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1.92
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Test Piece position
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Laid on to the side
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* Drawing ratio range (1.7~2.16) : 85mm(1.7)~108mm(2.16)) |
6.Bending Test
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Bending test is performed to determine the ductility
of steel sheet. Test specimen for cold-rolled
steel sheet is designated in KS B 0801 No.3.
In the test, the specimen is bent to a specified
angle on a mandrel or a specified radius until fracture.
The ductility of the sheet is judged by the cracks
on the outside of the bent specimen. In case of
cold-rolled sheet the specimen is bent 180 degrees.
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7.Hardness Test
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Harness of steel sheet is closely related to other
properties like strength, wear resistance, and workability.
Hardness test is a good indicator of various properties
of steel sheet. For measuring the hardness of cold-rolled
steel sheet, Rockwell Hardness test is used.s |
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Rockwell Hardness Test
Material resistance to
indentation is a qualitative indication of
its strength. Steel ball or diamond is often
used as an indenter. With this system, hardness
value is determined by the difference in penetration
depth from an application of initial minor
load onto the indenter followed by a major
load.
B-scale uses 1/16(1.588mm)
steel ball indenter and major load is 100kg.
The B-scale most accurately measures specimens
with the thickness of 0.762mm(0.030in.)
or over.
F-scale uses 1/16(1.588mm)
steel ball indenter and major load is 60kg.
It is preferable to use the F-scale for specimen
with the thickness under 0.762mm.
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8.Drawing Test
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The drawability of cold-rolled steel sheet can
be measured with various testing methods. Drawing
involves many intricate fabrication process, thus
it is nearly impossible to determine the drawability
of a steel sheet by just applying one testing method.
The following methods are most commonly used. |
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