Technological World CH 12 Manufacturing Technical Objects Constraints

Technological World – CH 12 Manufacturing Technical Objects Constraints and Deformations 1

Constraints �A constraint describes the effect of external forces acting on an object or material � We will discuss: � Compression � Tension � Torsion � Deflection � Shearing 2

Compression �A material subjected to forces that tend to crush it is undergoing compression � Symbol: � Examples: � Squeezing sponge � Crushing can � Press � Dribbling 3

Tension �A material subjected to forces that tend to stretch it is undergoing tension � Symbol: � Examples: � Suspended � Tug of war � Tow truck 4 rope

Torsion �A material subjected to forces that tend to twist it is undergoing torsion � Symbol: � Examples: � Wringing a towel � Twisting an elastic � Twisting a flexible ruler � Chris Hadfield: � https: //www. youtube. com/watch? v=o 8 Tssbm. Y-GM 5

Deflection �A material subjected to force that tend to bend it is undergoing deflection �A force in the middle is being opposed by forces at the end � Symbol: � Examples: � Bow and arrow � Fish bending a rod � Clothes weighing down a clothesline � https: //www. youtube. com/watch? v=Nz_4 i 1 e 6 pp. M 6

Shearing �A material subjected to forces that tend to cut it is undergoing shearing � Requires forces acting in opposite directions � Symbol: � Example: � Scissors cutting paper � Metal cutters trimming � Skating 7

Material Deformation � When a material or object is subjected to a constraint, one of three types of material deformation can occur: � Elastic � Plastic � Fracture 8

Elastic Deformation �A temporary change in the shape or dimensions of the material occurs. When the constraint (force) is removed, the material returns to its original form. � Example: � Elastic band � Bouncing ball 9

Plastic Deformation �A permanent change in the shape or dimensions of the material occurs. Even when the constraint is removed, the material remains deformed. � Example: � Soda can � Bent spoon 10

Fracture � The 11 constraint is so intense that the material breaks