DT_Tensiometer Test

Introduction

Tensiometer test is categorized in the Destructive testing, in industry it is used to estimate changes in the different properties of material before it breaks for quality purpose which is achieved by applying stress on specimen with the help of tensiomenter.

Objective

Using the tensiomenter estimate the following properties of the given material on graph:

• Elasticity
• Plasticity
• yield stress
• fracture point

Apparatus

• Tensiometer
• Table
• Graph paper 
• Test materials (i.e. Brass and Carbon steel).

Safety Procedures

Tensiometer is an isolated instrument so we do not have to take much safety precautions however using gloves and eye protection may be essential as the material that we may use drop some particle around. Further the specimen will fly off when it breaks, so the people around must be paying attention.

Test Procedure

Setup the tensiomenter on the table; place a graph paper at the drum of the tensiometer, before fastening the specimen in position we need to reset the gauge to zero (this will be on no load condition), after placing the specimen in position as we put the material in stress condition by turning the cam, as the more stress is applied it began to elongate gradually and finally fails.

While the tensile force is applied we keep marking the reference points which will help determining us the different properties of the material on graph.

Before the material reaches its fracture point and fails it goes through two stages

i)                    Elastic range

ii)                  Plastic range

Elastic range is the position wherein the material may show some abnormal behaviour but it can retrieve to its original stage.

Plastic range is the position in which material show the abnormal behaviour but its too late for it to be able to retrieve to its original position.

We repeated the same procedure for two different specimen materials, i,e, brass and carbon steel.

Observation

As the material is elongated (due to the stress applied) the area is reduced. The reduction in area leads the material to its breakdown, apart from few of material was worn down and could be seen under the tensiomenter.

The elongation and reduction in area is noted in both the material. These properties are due to the yield stress that any material has. Brass having lower yield stress breaks with lower stress applied but have more elongation elastic or plastic range (material tend to be less stiff). Carbon steel having higher yield stress has less elongation (both elastic and plastic) but breaks with higher stress applied (material tend to be more stiff).

Result

Brass showed more elongation and Carbon steel showed lesser elongation before it broke. The following schematics are obtained from the graph:

Brass has longer elastic and plastic ranges and lower yield stress and ultimate tensile strength comparable to the carbon steel i.e. carbon steel has short elongation ranges and higher yield stress and ultimate tensile strength.

Conclusion

The higher the yield stress of material, the lesser will be area reduction and hence more force required to deform the material before it reaches its fracture point.

engineereverything by Asad Ali is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License. Based on a work at www.facebook.com. Permissions beyond the scope of this license may be available at http://engineereverything.blogspot.co.uk/2012/04/copy-right-note.html.