Tensile Test on Steel

Efforts By:Devashish Soni

Engineering Materials -IIFaculty Coordinator-Prof. Anal Sheth

Properties of Steel• Chemical Composition: C=0.45%, Mn=0.75%,

P=0.04% max, S=0.05% max • Density : 7.872 x 10³ kg/m³ • Modulus of elasticity : 201 GPa • Thermal expansion (20 ºC) : 11.7 x 10-6 ºCˉ¹ • Specific heat capacity : 486 J/(kgK) • Thermal conductivity : 50.9 W/(mK) • Electric resistivity: 1.62*10-7 Ohmm • Tensile strength (hot rolled) : 565 MPa • Yield strength (hot rolled) : 310 MPa • Elongation (hot rolled) : 16%• Hardness (hot rolled) : 84 RB

The purpose of Tensile Tests is to calculate mechanical properties of steel, namely Modulus of Elasticity, yield stress, ultimate stress, resilience, fracture toughness, failure strain, and % area reduction.

Tension Members

The tension member is the one intended to resist axial tension.

They are basically divided in 4 types:

Wires and cablesRods and BarsSingle structural shapes and platesBuilt up sections

Equipments for Tensile Test

Instron Testing Machine

A universal Testing machineThe most common testing machine used in tensile testing is the universal testing machine. This type of machine has two crossheads; one is adjusted for the length of the specimen and the other is driven to apply tension to the test specimen. There are two types: hydraulic powered and electromagnetically powered machines

The most common testing machine used in tensile testing is the universal testing machine. This type of machine has two crossheads; one is adjusted for the length of the specimen and the other is driven to apply tension to the test specimen. There are two types: hydraulic powered and electromagnetically powered machines.[ The machine must have the proper capabilities for the test specimen being tested. There are three main parameters: force capacity, speed, and precision and accuracy. Force capacity refers to the fact that the machine must be able to generate enough force to fracture the specimen. The machine must be able to apply the force quickly or slowly enough to properly mimic the actual application. Finally, the machine must be able to accurately and precisely measure the gage length and forces applied; for instance, a large machine that is designed to measure long elongations may not work with a brittle material that experiences short elongations prior to fracturing.

Alignment of the test specimen in the testing machine is critical, because if the specimen is misaligned, either at an angle or offset to one side, the machine will exert a bending force on the specimen. This is especially bad for brittle materials, because it will dramatically skew the results. This situation can be minimized by using spherical seats or U-joints between the grips and the test machine. A misalignment is indicated when running the test if the initial portion of the stress-strain curve is curved and not linear.

Tensile specimens made from an aluminium alloy. The left two specimens have a round cross-section and threaded shoulders. The right two are flat specimen designed to be used with serrated grips.

Fracture Surfaces

0.002” fracture surface 1/64” fracture surface

1/32” fracture surface

Standard 1045 fracture surface

Tensile Specimen

A tensile specimen is a standardized sample cross-section. It has two shoulders and a gauge (section) in between. The shoulders are large so they can be readily gripped, whereas the gauge section has a smaller cross-section so that the deformation and failure can occur in this area.

The shoulders of the test specimen can be manufactured in various ways to mate to various grips in the testing machine (see the image below). Each system has advantages and disadvantages; for example, shoulders designed for serrated grips are easy and cheap to manufacture, but the alignment of the specimen is dependent on the skill of the technician. On the other hand, a pinned grip assures good alignment. Threaded shoulders and grips also assure good alignment, but the technician must know to thread each shoulder into the grip at least one diameter's length, otherwise the threads can strip before the specimen fractures.

In large castings and forgings it is common to add extra material, which is designed to be removed from the casting so that test specimens can be made from it. These specimen not be exact representation of the whole workpiece because the grain structure may be different throughout. In smaller workpieces or when critical parts of the casting must be tested, a workpiece may be sacrificed to make the test specimens. For workpieces that are machined from bar stock, the test specimen can be made from the same piece as the bar stock.

A schematic of various shoulder styles for tensile specimens. Keys A through C are for round specimens, while keys D and E are for flat specimens. Key:A. A threaded shoulder for use with a threaded gripB. A round shoulder for use with serrated gripsC. A butt end shoulder for use with a split collarD. A flat shoulder for used with serrated gripsE. A flat shoulder with a through hole for a pinned grip

Stress-Strain Plot For 1045 Steel With Cracks

0

20000

40000

60000

80000

100000

120000

140000

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08

Strain (in/ in)

Str

ess

(psi

) "1/64

"002.

"1/32

Standard 1045

Results

THANK YOU…

UC 5711 Devashish

Soni SBST 2nd Sem. CEPT

UNIVERSITY