Understanding Mechanical Properties and Structural Forces

Understanding Forces and Mechanical Properties

A force is capable of producing action, changing the state of rest or motion of a body, or producing strains. The unit of force in the International System of Units (SI) is the newton (N).

Mechanical properties determine the behavior of materials when one or more forces are applied:

• Resistance: The ability of a material to withstand forces without excessive deformation or breakage (e.g., steel, wood, plastic).
• Toughness: The capacity to withstand repeated forces without breaking (e.g., metal, wood, some plastics). Its opposite is fragility (e.g., glass).
• Elasticity: The ability of a material to recover its original shape after being deformed (e.g., rubber).
• Plasticity: Materials that can be deformed permanently without breaking (e.g., clay).
• Ductility: The property of certain materials to be deformed permanently into a thin wire without breaking.
• Malleability: The property of certain materials to be deformed permanently into thin sheets without breaking.
• Hardness: The resistance a material offers to being scratched or penetrated.

Structural Efforts and Forces

The resistance of an object to a given effort depends on three factors: size, shape, and the direction of the forces acting on the object.

• Traction (Tension): Two opposing forces acting on a body that tend to pull or extend it.
• Compression: Forces acting on an object in the same axis but in opposite directions, tending to crush or shorten it.
• Flexion (Bending): Forces applied against a piece perpendicular to its longitudinal axis, tending to bend it.
• Torsion: Forces that cause a body to twist or warp.
• Shearing (Cutting): Forces large enough to overcome the internal resistance of the material.

Structural Design and Engineering

Structures are sets of elements joined together with the basic function of supporting forces. There are two primary types:

• Armor (Truss): A strong set of elements linked together, constituting the skeleton of an object.
• Casing (Shell): Made up of sheets or panels bonded together to surround the object.

When designing structures, the most important factors are the material and the form. Materials should be highly resistant, and forms must be stable. In metallic structures, the simplest form providing high rigidity and resistance is the triangle. Structures are typically constructed using structural rolled steel profiles, such as IPN, U, HEB, angular, and T-profiles.