Internal Forces (Stress)
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In materials science, stress refers to the internal forces that exist within a material as a result of external loads or forces acting on it. Stress in metals can be caused by a variety of factors, including temperature changes, mechanical loads, and corrosion.
There are five types of stress that can occur in metals: shear stress, bending stress, torsion stress, tensile stress, and compressive stress. In Vex robotics, the most common types are Bending, Torsion, and Compression/Tension (opposites).
The strength of a metal is determined by its ability to withstand stress without failing. When a metal is subjected to stress, it will either deform elastically (temporarily) or plastically (permanently). If the stress is high enough, the metal will eventually break, which is known as yielding or failure.
Stress can also affect the physical and mechanical properties of metals, such as their ductility, malleability, and toughness. For example, a metal that is subjected to high tensile stress may become more brittle and less able to withstand further stress.
Managing stress in metals is important in order to ensure their structural integrity and prevent failure. This can be done through various methods, such as using stress-relieving techniques, applying appropriate protective coatings, and designing structures to distribute stress evenly. In Vex, stress can be managed by assuring that loads are properly distributed and pieces are properly braced.
Bending is the most common type of stress in the robotics design process. Bending comes from a force being applied perpendicular to the length of an object. Commonly, a piece of metal that is used in a lift will have forces that cause bending.
Torsion is very common in underdeveloped robots. Torsion is caused by force applied tangent to an object's axis, commonly called twisting. Oftentimes, this is seen along long pieces of metal that might be sparsely supported or an axle in high torque situations with little support.
These two are opposite forces where a force is being applied through an axis of an object either pushing (compression) or pulling (tension). In robotics, this is often times seen at connections between pieces through screws, standoffs, or spacers that become inconsistent over time.
(Purdue SIGBots)
