**Stress Concentration Experiment**

Complete the section of specimen dimensions.

Carry out calculation and complete section I of data sheet.

Plot Figure 1: A curve of stress vs. strain using the calculated data in Section I of data sheet.

Determine the average modulus of elasticity for the rubber specimen based on the curve in Figure 1. The average modulus of elasticity should be the slope of the best-fit straight line through data points in Figure 1.

Referring to the specimen drawing in data sheet, (a) where would the maximum stresses be at the hole? (b)what is the direction of the maximum stresses?

Carry out calculation and complete section II of data sheet. Document your calculation in report.

Calculate (a) the maximum local stress and (b) the maximum stress concentration factor at the hole using stress data in section II of datasheet.

MECH 210 – Materials Science and Engineering Laboratory

Stress Concentration Experiment

Date: __________________ Name: _______________________________

Specimen material: ______Natural Rubber______________

Thickness: ____4.65_____ mm = _____________________ m

Width: _______152______ mm = _____________________ m

Diameter of round hole: __25.74___mm = ______________ m

Total cross sectional area (A1): ________________________ m2

Net cross sectional area (A2): _________________________ m2

I. At a location away from the hole for the determination of elastic modulus

Load ( kg ) Load ( N ) Stress ( MPa ) Lx ( mm ) Lx ( mm ) Strain, x

0 0 0 79 0 0

2 80

4 81.5

6 83

8 84

10 85.5

12 87

II. At various locations for the determination of stress concentration factor and stress profile

Distance from the edge of the circular hole for location 1, di : 0 mm

Load ( kg ) Load ( N ) Nominal Stress(MPa) li (mm) li( mm ) Strain, i Local Stress (MPa)

0 0 0 3.6 0 0 0

12 4.7

Distance from the edge of the circular hole for location 2, di: 3.6 mm

Load ( kg ) Load ( N ) Nominal Stress(MPa) li (mm) li( mm ) Strain, i Local Stress (MPa)

0 0 0 3.6 0 0 0

12 4.4

Distance from the edge of the circular hole for location 3, di: 7.2 mm

Load ( kg ) Load ( N ) Nominal Stress(MPa) li (mm) li( mm ) Strain, i Local Stress (MPa)

0 0 0 3.6 0 0 0

12 4.2

Distance from the edge of the circular hole for location 4, di: 10.8 mm

Load (kg ) Load ( N ) Nominal Stress(MPa) li (mm) li( mm ) Strain, i Local Stress (MPa)

0 0 0 3.6 0 0 0

12 4.1