OBJECT: TO PERFORM HARDNESS/TOUGHNESS TEST ON STEEL BAR.

APPARATUS:

• Steel Specimen
• Diamond Cone Identor
• Rockwell Hardness Tester

THEORY:

1. HARDNESS TEST
   
2. ROCKWELL HARDNESS TEST
   

ROCKWELL HARDNESS APPARATUS

1. BRINELL HARDNESS TEST
   

VICKERS HARDNESS APPARATUS

BRINELL HARDNESS APPARATUS

1. VICKERS HARDNESS TEST
   

METHODOLOGY:

OBSERVATIONS & DISCUSSIONS

• Method adopted for hardness test of metal bar = _______________
  
• Hardness Scale used for hardness of metal bar = ________________
  
• Metal Bar type = _________________
  
• Hardness number = _______________
  

1. Which method should we adopt for hardness test and why?

RESULTS:

or

ROCKWELL HARDNESS TESTER

AIM: To determine the hardness of the given Specimen using Rockwell hardness test.

APPARATUS: Rockwell hardness testing machine,

MATERIAL: soft and hard mild steel specimens, brass, Aluminum etc., Black diamond cone indenter.

DIAGRAM:

THEORY:

Rockwell test is developed by the Wilson instrument co U.S.A in 1920. This test is an indentation test used for smaller specimens and harder materials. The test is subject of IS: 1586. The hardness of a material is resistance to penetration under a localized pressure or resistance to abrasion. Hardness tests provide an accurate, rapid and economical way of determining the resistance of materials to deformation.

There are three general types of hardness measurements depending upon the manner in which the test is conducted:

1. Scratch hardness measurement,
   
2. Rebound hardness measurement
   
3. Indention hardness measurement.
   

In scratch hardness method the material are rated on their ability to scratch one another and it is usually used by mineralogists only. In rebound hardness measurement, a standard body is usually dropped on to the material surface and the hardness is measured in terms of the height of its rebound .The general means of judging the hardness is measuring the resistance of a material to indentation. The indenters usually a ball cone or pyramid of a material much harder than that being used. Hardened steel, sintered tungsten carbide or diamond indenters are generally used in

PROCEDURE:

1. Examine hardness testing machine (fig.1)
   
2. Place the specimen on platform of a machine. Using the elevating screw raise the platform and bring the specimen just in contact with the ball. Apply an initial load until the small pointer shows red mark.
   
3. Release the operating valve to apply additional load. Immediately after the additional load applied, bring back operating valve to its position.
   
4. Read the position of the pointer on the C scale, which gives the hardness number.
   
5. Repeat the procedure five times on the specimen selecting different points for indentation.
   

OBSERVATION TABLE:

PRECAUTIONS:

1. The specimen should be clean properly
   
2. Take reading more carefully and
   
3. The test should not be made on specimens so thin that the impression shows through the metal, nor should impression be made too close to the edge of a specimen.
   

VIVA QUESTIONS:

1. Define Hardness
   
2. Size of the Ball to be used in Ball Indenter of Rockwell Hardness Test.
   
3. Different Types of Hardness Testing Methods.
   
4. Applications of Rockwell Hardness A – Scale, B-Scale, C-Scale
   
5. In Rockwell hardness test the hardness is measured by?
   

APPLICATIONS:

1. In manufacturing Industries
   

1. Bearing Manufacturing industries