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To Determine Yield Strength & Tensile Strength of a Steel Bar



UTM, Test Specimen, Vernier Calipers, Ruler etc.

Description of UTM:

A machine designed to perform tensile, compression, bend and shear tests, is called UTM,. It mainly consists of two parts.

  • Loading Unit, control unit. In addition to these units, there are certain accessories like bending table, jaws for gripping recorders etc.
  • Loading unit consists of two crossheads i.e upper cross head and lower cross head and a table


  1. Prepare a test specimen of at least two feet.

  2. Measure caliper at least at three places and then find average.

  3. Insert the suitable jaws in the grip and select a suitable load scale on UTM.

  4. Insert the specimen in the grip by adjusting the cross heads of UTM.

  1. Start machine and continue applying the load.

  2. At a point when the values of the load at that point this is called yield point.

  3. When the specimen breaks stop the machine.

  4. Note the ultimate value of the load.

  5. Determine the yield strength and tensile strength of load dividing the yield load & ultimate load by cross sectional area of the bar.

Gauge length = 8 inch

ASTM Standards


Grade 40

Grade 60

Grade 75

Minimum Yield Strength

40,000 Psi

60,000 Psi

75,000  Psi

Maximum Yield Strength

60,000 Psi

90,000 Psi

1,00,000 Psi

Elongation = 9.8 8 = 1.9

S No

Dia of Bar

Yield Load(Tons)

Ultimate load(Tons)

Area of Bar,
A=∏ D 2 /4

Yield Strength=Yield Load *2204/ Area

Tensile Strength = Yield Load*2204/ Area


½ in



0.196 in2

67132.04 Psi

104352. 65 Psi


½ in



0.196 in2

54650.20 Psi

86023. 46 Psi


½ in



0.196 in2

61509.62 Psi

91196. 12 Psi


½ in



0.196 in2

61059.85 Psi

93445. 10 Psi


1/8 in



0.306 in2

50778.43 Psi

78868. 62 Psi

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