TENSILE Lab Sheet
TENSILE Lab Sheet
TENSILE Lab Sheet
TENSILE TEST
Introduction
Metallic materials tensile test is used as the standard TS 138 EN 10002-1 standard. These test methods
cover the tension testing of metallic materials in any form at room temperature, specifically, the methods
of determination of yield strength, yield point elongation, tensile strength, elongation, and reduction of
area.
The major parameters that describe the stress-strain curve obtained during the tension test are the tensile
strength (UTS), yield strength or yield point (σy), elastic modulus (E), percent elongation (ΔL%) and the
reduction in area (RA%). Toughness, Resilience, Poisson’s ratio(ν) can also be found by the use of this
testing technique.
Specimen Preparation
In this test, a specimen is prepared suitable for gripping into the jaws of the testing machine type that will
be used. The specimen used is approximately uniform over a gage length (the length within which
elongation measurements are done).
Tensile specimens are machined from the material to be tested in the desired orientation and according
to the standards. The cross section of the specimen is usually round, square or rectangular. For metals,
a piece of sufficient thickness can be obtained so that it can be easily machined, a round specimen is
commonly used.
For sheet and plate stock, a flat specimen is usually employed. The change in the gage length of the
sample as pulling proceeds is measured from either the change in actuator position (stroke or overall
change in length) or a sensor attached to the sample (called an extensometer).
A tensile load is applied to the specimen until it fractures. During the test, the load required to make a
certain elongation on the material is recorded. A load-elongation curve is plotted by an x-y recorder, so
that the tensile behavior of the material can be obtained. An engineering stress-strain curve can be
constructed from this load-elongation curve by making the required calculations. Then the mechanical
parameters that we search for can be found by studying on this curve.
Engineering Stress is obtained by dividing the load by the original area of the cross section of the
specimen.
Engineering stress and strain are independent of the geometry of the specimen.
Elastic Region: The part of the stress-strain curve up to the yielding point. Elastic deformation is
recoverable. In the elastic region, stress and strain are related to each other linearly.
Hooke’s Law: = Ee
The linearity constant E is called the elastic modulus which is specific for each type of material.
Plastic Region: The part of the stress-strain diagram after the yielding point. At the yielding point, the
plastic deformation starts. Plastic deformation is permanent. At the maximum point of the stress-strain
diagram (σUTS), necking starts.
Tensile Strength is the maximum stress that the material can support.
σUTS = Pmax/Ao
Because the tensile strength is easy to determine and is a quite reproducible property, it is useful for the
purposes of specifications and for quality control of a product. Extensive empirical correlations between
MM207E | Materials Science | Lab2_Tensile Test | Mechanic Lab.
tensile strength and properties such as hardness and fatigue strength are often quite useful. For brittle
materials, the tensile strength is a valid criterion for design.
Yield Strength is the stress level at which plastic deformation starts. The beginning of first plastic
deformation is called yielding. It is an important parameter in design.
B
A
Fig 3. a)Typical engineering stress-strain curve b) A comparison of typical tensile engineering stress–
strain and true stress–strain behaviors.
MM207E | Materials Science | Lab2_Tensile Test | Mechanic Lab.
Ductility is the degree of plastic deformation that a material can withstand before fracture. A material that
experiences very little or no plastic deformation upon fracture is termed brittle.
In general, measurements of ductility are of interest in three ways:
1. To indicate the extent to which a metal can be deformed without fracture in metalworking operations
such as rolling and extrusion.
2. To indicate to the designer, in a general way, the ability of the metal to flow plastically before fracture.
3. To serve as an indicator of changes in impurity level or processing conditions. Ductility measurements
may be specified to assess material quality even though no direct relationship exists between the ductility
measurement and performance in service.
A B
Fig 4. a) Schematic representations of tensile stress–strain behavior for brittle and ductile materials
loaded to fracture b) Diagram of the stress-strain curves of low, medium and high carbon steel.
Strain Hardening: The strain hardening exponent (also called strain hardening index), noted as n, is a
materials constant which is used in calculations for stress–strain behavior in work hardening. In the
formula,
σ = K εn
σ represents the applied stress on the material,
ε is the strain,
K is the strength coefficient.
MM207E | Materials Science | Lab2_Tensile Test | Mechanic Lab.
The value of the strain hardening exponent lies between 0 and 1. A value of 0 means that a material is a
perfectly plastic solid, while a value of 1 represents a 100% elastic solid. Most metals have an n value
between 0.10 and 0.50.
References
ASM Handbook, Vol. 8, Mechanical Testing and Evaluation, ASM Int., Materials Park, OH, 2000.
TS 138 Metallic materials – Tensile testing – Part 1: Method of test at ambient temperature
ASTM E8/E8M Standard Test Methods for Tension Testing of Metallic Materials
Meyers, M. A. and K. K. Chawla, Mechanical Behavior of Materials, Prentice Hall PTR, Par., NJ, 1999.
Courtney, T. H., Mechanical Behavior of Materials, 2nd ed., McGraw-Hill Higher Edu., Burr Ridge, IL, 2000.
Materials Science and Engineering, Eight Edition, William D. Callister and David G. Rethwisch
METU tension test sheet
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