Technological World – CH 12 Manufacturing Technical Objects Constraints and Deformations

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

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

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

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=o8TssbmY-GM

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_4i1e6ppM

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

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

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

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

Fracture The constraint is so intense that the material breaks