Material Mechanics (1): Material Mechanics and Load type

Material Mechanics: The study of the internal effects in materials due to external forces, specifically, the resistance of materials to failure (strength).

 

Internal Changes in Materials:

  1. Deformation: Presented as deformation or strain.
  2. Resistance to Force: Manifested as resistance or stress.

Types of Deformation:

  1. Elasticity: The property of a material that allows it to return to its original shape after removing the forces that cause deformation.
      A. Example: Rubber, springs
      B. A property manifested only in solids with a definite shape.

   2. Plasticity: The state of a deformed material not returning to its original state after the removal of the applied force; a permanent deformation.

Load: External forces acting on a body.

   1. Classification of loads based on the state of action:
      A. Axial load (normal load): A load acting in the direction of the material's axis (vertical).
         i. Tensile load: A load that acts by pulling the material in the axial direction.
         ii. Compressive load: A load that acts by pressing the material in the axial direction.
        
      B. Shear load: A load acting perpendicular to the material's axis.
      C. Bending load: A load acting when bending the material.
      D. Torsional and twisting load: A load acting when twisting the material.

   2. Classification of load based on the duration of action:
        
       A. Static load:
           i. The size and direction do not change over time.
           ii. If the size and direction change over time, the load is negligible.

       B. Dynamic load: The magnitude or direction of the load changes over time.
            i. Repeated load: A load in which forces of varying magnitudes act repeatedly and continuously.
            ii. Alternating load: A load whose magnitude and direction change over time, which can lead to overlapping effects due to vibration.
            iii. Impact load: A large load acting momentarily due to impact.

   3. Classification based on the distribution state of the load:
       A. Concentrated load: The load is concentrated and appears at a specific point.
       B. Distributed load: The load is spread over a certain length or area.
       C. Moving load: A load that acts by moving over the object.
            i. Example: The load that the railroad receives when a train passes over it.