For a design to be adequate, it is necessary to consider the stresses and deformations acting on the object. Each material has its own response, according to its characteristics.
The mechanics of materials is based in turn on statics, since it must make use of its methods and concepts, such as the different loads or forces and the moments to which bodies can be exposed during their operation. It is also necessary to consider the equilibrium conditions of an extended body.
In this way, the strength, rigidity, elasticity and stability of bodies are thoroughly studied.
The mechanics of materials is also known as resistance of materials or mechanics of solids.
History of material mechanics
Since the beginning of mankind, people have checked, by trial and error, the characteristics of the materials in their environment. It’s not hard to imagine hard-working stone age artisans choosing the right rocks to carve their arrowheads.
With the sedentary lifestyle, structures began to be built that over time evolved to the monumental buildings of the peoples of Ancient Egypt and Mesopotamia.
These builders knew well the response of the materials they used, to such an extent that even today the temples, pyramids and palaces that they left continue to cause astonishment.
The same can be said of the engineering of the ancient Romans, notable for its design in which they applied arches and vaults, as well as the successful use of materials.
Modern Materials Mechanics
The formalism of the mechanics of materials emerged centuries later, thanks to the experiments of the great Galileo Galilei (1564 – 1642), who studied the effects of loads on bars and beams made of different materials.
Galileo expressed in his book Two Science Caves his conclusions about the failures in structures such as cantilevered beams. Later, Robert Hooke (1635-1703) laid the foundations for the theory of elasticity, with the famous Hooke’s law , which states that the deformation, as long as it is small, is proportional to the stress.
Isaac Newton (1642-1727) established the laws of motion that define the action of forces on objects, and independently with Gottfried Leibnitz, he invented mathematical calculus, a fundamental tool for modeling the effects of forces.
Later, starting in the 18th century, several notable French scientists carried out experiments with materials: Saint-Venant, Coulomb, Poisson, Lame, and Navier, the most notable. The latter is the author of the first text on modern materials mechanics.
At the same time, mathematics evolved to provide tools for solving more complex mechanical problems. Notable are the experiments of Thomas Young (1773-1829), who determined the stiffness of different materials.
Today, many problems are solved using numerical methods and computer simulations, as advanced research in materials science continues.
Field of study mechanics of materials
The mechanics of materials studies real solids, those that can deform under the action of forces, unlike ideal solids, which are undeformable. From experience it is known that real materials can fracture, stretch, compress or flex, according to the load they experience.
For this reason, the mechanics of materials can be considered as the next step to statics. In this it was considered that solids were non-deformable, what follows is to find out how they deform when external forces act on them, because thanks to these forces, internal forces are developed in response to objects.
Deformation of the body and eventually rupture depend on the intensity of these efforts. Then the mechanics of materials provides the bases for an effective design of parts and structures, regardless of the material of which they are made, since the theory developed applies to all of them.
Strength and rigidity mechanics of materials
The response of the materials depends on two fundamental aspects:
The resistance of an object is understood to be its ability to withstand efforts without breaking or fracturing. However, in this process, the object can deform and its functions within the structure are diminished, according to its rigidity.
The stiffer the material, the less it tends to deform under stress. Of course, whenever an object is under stress, it will undergo some kind of deformation, which may or may not be permanent. The idea is that this object does not stop working properly despite this.
Types of efforts mechanics of materials
The mechanics of materials considers the effects of various efforts, which it classifies by their shape or duration. Due to its shape, efforts can be made of:
- Traction, is a normal stress (it acts perpendicular to the cross section of the object) and produces its elongation.
- Compression is also a normal effort, but it favors shortening.
- Shear, consists of forces in the opposite direction applied to the cross section of the body, the effect of which is to produce a cut, dividing it into sections.
- Bending, perpendicular forces that tend to bend, bend or buckle the element on which they act.
- -Torsion, they are pairs applied to the object that twist it.
And due to its speed, the efforts are:
- Static, which act very slowly on the body.
- Of impact, they are of short duration and intense effect.
- Fatigue, which consist of repetitive stress-strain cycles that end up fracturing the element.
Materials mechanics applications
Whenever you have a structure, machinery or any object, it will always be subjected to numerous efforts derived from its use. As mentioned before, these stresses cause deformations and eventual breaks: the beams can buckle, with the risk of collapse, or the gear teeth can break.
So the materials used in various utensils, machinery and structures must be appropriate, not only to guarantee their correct operation, but to be safe and stable.
In general, the mechanics of materials works in this way:
In the first instance, the structure, whose geometry is known, is analyzed, determining the forces and deformation, to find the maximum load that can be applied and that does not exceed a pre-established deformation limit.
Design mechanics of materials
Another option is to determine the dimensions of the structure, given certain loads and allowable stress and strain values.
In this way, the mechanics of materials is applied interchangeably to various areas:
- Civil engineering : for the design of buildings according to the type of loads they must withstand.
- Automotive and aeronautical mechanics: in the design of parts for cars, airplanes and boats.
- Medicine: biomaterials is a very interesting area, in which the principles described are applied in the design of various prostheses and as tissue substitutes, for example.
In this way, the mechanics of materials is positioned as the basis of the science and engineering of materials, a multidisciplinary branch with spectacular advances in recent times.