Direct Shear Test Of Metal Specimens Lab Report CE 213

 

DIRECT SHEAR TEST OF METAL SPECIMENS

 

 

1. OBJECTIVES

 

 

-To make a shear of metal specimens approximating the conditions of shear existing in rivets, pins, and bolts

 

-To determine the strength in single and double shear

 

-To observe the shape and texture of the fractured surface.

 

 

2. APPARATUS AND MACHINE

 

 

UTM, shear tool, Slide calipers, stop watch and computer.

 

 

3. SIGNIFICANCE

 

This experiment provides fundamental knowledge on direct shear behaviour of materials, test procedure, universal testing machine and its working principal, specimens, failure patterns etc.

 

4.  SPECIMENS Steel screws.

 

5.  THEORY

 

Shearing stress is one that acts parallel or tangential to stressed surface. It is different from normal stress that acts perpendicular to the stressed surface, e.g. tension, compression or bending stresses. It resists the tendency of a part of the body on one side of the plane to slide against the other side of the same plane.

 

                                              

                                                     

 

The direct shear test (also called transverse shear test) gives an approximation to the correct values of shearing strength. This test is usually done in a Johnson type shear (Figure

 

1)    of shear tool by clamping a portion of a material so that bending stress are minimized across the plane along which the shearing load is applied. Because of inevitable bending and friction between parts of tool, it gives an indication of the shearing resistance of materials. The direct shear test has further limitation for the determination of elastic strength or of the modulus of rigidity or shear rigidity, because of difficulty to measure shearing strain.

6. PROCEDURE

 

 

i)           Measure the diameter of the specimen with the slide calipers.

 

ii)         Fix the specimen in the shear tool such that it is in single shear and apply load until rupture takes place.

 

iii)      In the same way test the specimen for double shear.

 

 

7. SAMPLE CALCULATIONS

 

 

Calculate double, unit double and single shear stresses from maximum shear force data.

8. GRAPH

 

 

1.  Combined Double Shear, Unit Double Shear and Single Shear force vs. displacement graph.

 

9. RESULT

 

 

	Type of	Dia	Shear	Maximum Shear	Maximum	Failure	Fracture
	Shear		Area	force	Shear stress or	pattern	surface
			(mm2)		Shear strength
		(mm)		(N)	(MPa)
	Double
	Shear
	Unit
	Double
	Shear
	Single
	Shear
10. DISCUSSION

 

(Discuss on the results found, graphs, and failure patterns and also compare the results found, graphs and failure patterns.)

 

Point out the discussion

 

1.

 

2.

 

3. ….

 

 

11. ASSIGNMENT

 

 

1.  Why single shear strength is greater than unit double shear?

 

2.  How we can measure shear rigidity?