Lab 1: Tensile Testing of Reinforced Steel to AS/NZ 4671

Civil 245: Construction Materials
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Table of contents
Introduction – page 3
Experimental procedure – page 4
Classification and designation – page 6
Stress Strain diagrams – page 7-9
Summary of mechanical properties – page 13
Data interpretation – page 14
Concluding remarks – page 14
References – page 14
Appendices – page 16

INTRODUCTION
Aim: To specifically test the properties of three different reinforcing bars in tensile strength, yield stress, elongation, modulus of elasticity, reserve strength and ductility.
OBJECTIVE: The objective is to determine the mechanical properties and ductility class of steel reinforcing bars
A good knowledge of the properties of steel in the field of engineering is imoerative. These These include elastic limit, yield strength, fracture strength and toughness. These factors contribute overall to the materials strength and overall load bearing capabilities.
With these materials engineers have created aesthetically pleasing unique structures. For these buildings to be structurally sound the right materials must be used such steel which is a major component in the reinforcement of concrete. The correct use of materials will ensure a strong, long lasting cost efficient building. However stell has many requirements and guidelines to do with quality control and its implementation in structures. To meet requirements, these steel bars undergo an array of tests.

Experimental procedure
The three steel bars were all tested on the instron 8033, and the test data was saved as an excel file.
1. The first step was to raise the height of the moveable arm in order to fit each 500mm long reinforcing bar into the grips of the testing machine.
2. The extension(mm)/minute was set to 1 until approximately 5 minutes passed. This was in order to get an accurate reading on the gradient of the stress/strain curve and therefore an accurate measurement of each material’s modulus of elasticity.
3. The extension(mm)/minute was then increased to 3 until the material entered plastic deformation
4. After the plastic deformation region the extension(mm)/minute was increased to 15 or 20 until the bar reached its yield strength and eventually necked and fractured.
5. All data was saved on a computer and stored as a file.

Details of sample
Each sample used is a reinforcing steel bar used in concrete slabs, each varying in composition and method of manufacturing.

Specific geometry
All bars have a length of 500mm. N12 and R12 have a diameter of 12mm, RW11.9 has a diameter of 11.9mm. All have a gage length of 200mm

Details of testing equipment
Instron servo hydraulic fatigue testing machine 8033.
This machine can test material in either compression or tension. The machine is comprised of a set of grips that can hold either a square, rectangular or cylindrical cross section the load capacity varies from 10kn to 500kn. It is connected to software that collects stress strain data in real time.
The speed of testing is dependent on the stress-strain relationship. During initial start of extension a slow rate is implemented to get an accurate elastic stress reading and gradient, to determine young’s modulus. After the rate of extension is increased to determine ultimate tensile stress.

Features Epsilon extensometer

• Specifically designed to be left on through specimen failure. The unit is designed so that the two halves of the extensometer come apart to prevent damage at specimen failure.
• Full bridge, 350 ohm