To determine percentage elongation and percentage reduction in area of steel bar.

OBJECT: TO DETERMINE PERCENTAGE ELONGATION AND PERCENTAGE REDUCTION OF AREA OF STEEL BAR.

APPARATUS:

• Steel Bars
• UTM
• Vernier Calliper
• Tape

THEORY:

1. LENGTH ELONGATION OF STEEL BAR (LINEAR STRAIN)
   
2. AREA OF STEEL BAR (LATERAL STRAIN)
   

METHODOLOGY:

OBSERVATIONS:

• Diameter of steel bar = ______ mm = ________ inches
  
• Initial area (A1) = ____________ mm²
  
• Reduced area (A2) = ______________ mm²
  
• Initial gauge length of steel bar (L1) = ____________ inches
  
• Elongated length of steel bar (L2) = ______________ inches
  
• Percentage elongation in length = _______________ %
  
• Percentage reduction in area of steel bar = ____________ %
  

CALCULATIONS:

RESULTS:

or

AIM: Determine the tensile Strength of a given specimen using UTM.

OBJECT: To conduct a tensile test on a mild steel specimen and determine the following:

1. Limit of proportionality
   
2. (ii) Elastic limit
   
3. (iii) Yield strength
   
4. (iv) Ultimate strength
   
5. (v) Young’s modulus of elasticity
   
6. (vi) Percentage elongation
   
7. (vii) Percentage reduction in area.
   

APPARATUS:

1. Universal Testing Machine (UTM)
   
2. (ii) Mild steel specimens
   
3. (iii) Graph paper
   
4. (iv) Scale
   
5. (v) Vernier Caliper
   

DIAGRAM:

THEORY:

The tensile test is most applied one, of all mechanical tests. In this test ends of test piece are fixed into grips connected to a straining device and to a load measuring device. If the applied load is small enough, the deformation of any solid body is entirely elastic. An elastically deformed solid will return to its original form as soon as load is removed. However, if the load is too large, the material can be deformed permanently. The initial part of the tension curve which is recoverable immediately after unloading is termed. As elastic and the rest of the curve which represents the manner in which solid undergoes plastic deformation is termed plastic. The stress below which the deformations essentially entirely elastic is known as the yield strength of material. In some material the onset of plastic deformation is denoted by a sudden drop in load indicating both an upper and a lower yield point. However, some materials do not exhibit a sharp yield point. During plastic deformation, at larger extensions strain hardening cannot compensate for the decrease in section and thus the load passes through a maximum and then begins to decrease. This stage the “ultimate strength”’ which is defined as the ratio of the load on the specimen to original cross- sectional area, reaches a maximum value. Further loading will eventually cause ‘neck’ formation and rupture.

The tensile test is conducted on UTM. It is hydraulically operates a pump, oil in oil sump, load dial indicator and central buttons. The left has upper, middle and lower cross heads i.e; specimen grips (or jaws). Idle cross head can be moved up and down for adjustment. The pipes connecting the lift and right parts are oil pipes through which the pumped oil under pressure flows on left parts to more the cross-heads.

SPECIFICATIONS:

1. Load capacity = 0-40 Tones.
   
2. Least count = 8 kgf.
   
3. Overall dimension. =
   
4. Power supply = 440 V
   

PROCEDURE:

1. Measure the original length and diameter of the specimen. The length may either be the length of the gauge section which is marked on the specimen with a preset punch or the total length of the specimen
   
2. Insert the specimen into the grips of the test machine and attach the strain-measuring device to it
   
3. Begin the load application and record load versus elongation data.
   
4. Take readings more frequently as the yield point is approached.
   
5. Measure elongation values with the help of dividers and a ruler.
   
6. Continue the test till Fracture occurs.
   
7. By joining the two broken halves of the specimen together, measure the final length and diameter of the specimen.
   

OBSEVATION:

1. Initial diameter of specimen d1 =
   
2. Initial gauge length of specimen L1 =
   
3. Initial cross-section area of specimen A1 =
   
4. Load of yield point Ft =
   
5. Ultimate load after specimen breaking F =
   
6. Final length after specimen breaking L2 =
   
7. Diameter of specimen at breaking place d2 =
   
8. Cross section area at breaking place A2 =
   

CALCULATION:

Ultimate tensile strength = ^𝑁 / 𝑚𝑚2

Elastic limit = 𝐿𝑜𝑎𝑑 𝑎𝑡 𝑒𝑙𝑎𝑠𝑡𝑖𝑐 𝑙𝑖𝑚𝑖𝑡 / 𝑜𝑟𝑖𝑔𝑖𝑛𝑎𝑙 𝑎𝑟𝑒𝑎 𝑜𝑓 𝑐𝑟𝑜𝑠 𝑠 𝑠𝑒𝑐𝑡𝑖𝑜𝑛 = …………… ^𝑁/𝑚𝑚2

Modulus of Elasticity (E) = ^{𝑠𝑡𝑟𝑒𝑠𝑠 𝑏𝑒𝑙𝑜𝑤 𝑝𝑟𝑜𝑝𝑜𝑟𝑡𝑖𝑜𝑛𝑎𝑙 𝑙𝑖𝑚𝑖𝑡} / 𝑐𝑜𝑟𝑟𝑠𝑝𝑜𝑛𝑑𝑖𝑛𝑔 𝑠𝑡𝑟𝑎𝑖𝑛 =…….……… ^𝑁𝑚𝑚2

Yield Strength = ^{𝑦𝑖𝑒𝑙𝑑 𝑙𝑜𝑎𝑑} / 𝑜𝑟𝑖𝑔𝑖𝑛𝑎𝑙 𝑐𝑟𝑜𝑠𝑠 𝑠𝑒𝑐𝑡𝑖𝑜𝑛𝑎𝑙 𝑎𝑟𝑒𝑎 =……………. 𝑁𝑚𝑚2

% Reduction in area = (𝐴𝑓−𝐴𝑖)/𝐴𝑖 × 100 = %
Percentage of elongation = (𝑙𝑖−𝑙𝑓)𝑙𝑓 × 100 = %

Limit of Propagation = 𝐿𝑜𝑎𝑑 𝑎𝑡 𝑙𝑖𝑚𝑖𝑡 𝑜𝑓 𝑝𝑟𝑜𝑝𝑟𝑡𝑖𝑜𝑛𝑎𝑙𝑖𝑡𝑦 / 𝑜𝑟𝑖𝑔𝑖𝑛𝑎𝑙 𝑐𝑟𝑜𝑠𝑠 𝑠𝑒𝑐𝑡𝑖𝑜𝑛𝑎𝑙 𝑎𝑟𝑒𝑎

• Stress 𝜎 = 𝐿𝑜𝑎𝑑 /𝐴𝑟𝑒𝑎 = ^𝑃/A …………………..= ^𝑁 /𝑚𝑚2
• Strain = 𝜖 = 𝑐ℎ𝑎𝑛𝑔𝑒 𝑖𝑛 𝑙𝑒𝑛𝑔𝑡ℎ / 𝑜𝑟𝑖𝑔𝑖𝑛𝑎𝑙 𝑙𝑒𝑛𝑔𝑡ℎ = ………….
• Young’s modulus= E = 𝑠𝑡𝑟𝑠𝑠 / 𝑠𝑡𝑟𝑎𝑖𝑛 =…………. ^𝑁/𝑚𝑚2

PRECAUTIONS:

1. The specimen should be prepared in proper dimensions.
   
2. The specimen should be properly to get between the jaws.
   
3. Take reading carefully.
   
4. After breaking specimen stop to m/c.
   

RESULT:

( i) Average Breaking Stress =

1. Ultimate Stress =
   
2. Average % Elongation =
   

VIVA-QUESTIONS

1. Which steel have you tested? What is its carbon content?
   
2. What general information is obtained from tensile test regarding the properties of a material?
   
3. Which stress have you calculated: nominal stress or true stress?
   
4. What kind of fracture has occurred in the tensile specimen and why?
   
5. Which is the most ductile metal? How much is its elongation
   

APPLICATIONS:

• 1. In Aerospace
     
  2. Automotive
     
  3. Packaging
     
  4. sports