Is the shear force a single force

In strength theory, a distinction is made between different types of stress that can act on a component. Loads arise from forces that act on the component. Which type of load is applied depends on the direction of action of the force, its position, its distribution and its course over time.

Differentiation according to the point of attack and the direction of action

With this type of differentiation, a distinction is made between the types of stress on the basis of their point of attack and their direction of action, which characterize them. This results in the four types of basic load: normal force load (tension / pressure), bending, shear (shear load) and torsion (twisting).

Basically, any pollution can be broken down into these four typical types of base pollution. These types of base exposure can exist individually or in combination. In the case of a combination, it makes sense to break down the total load into the corresponding individual basic load types and to calculate them individually in the first step.

Normal force load - tension / compression
In the case of a normal force load, the force takes effect in the center of gravity, the direction of action of the force always being in the direction of the center of gravity. With normal force, one can differentiate between tensile and compressive loads, depending on whether the force vector points into or out of the cross-sectional area.

Shear / shear stress
Shear stress occurs when opposing transverse forces act on a component, slightly offset from one another. These forces cause what is known as shear stress or sliding. This is also referred to as shear stress, as this is where shear stresses arise in the component. Shear stresses typically occur in rivet, screw and bolt connections.

A distinction can also be made between two cases when it comes to bending. There are a) pure bending, in which there is a pair of moments at the rod ends, and b) transverse force bending, in which the bending moment is caused by a transverse force (perpendicular to the gravity axis).
In the case of transverse force bending, it is essential to note that in addition to the bending moment, the transverse force is also present as a load.

Torsion / twist
In the case of torsion, a torque is applied in the direction of the center of gravity - the component (e.g. beam, rod) is twisted in the process. This load is typically found in waves.

As mentioned earlier, these different types of exposure rarely occur as a single exposure. In most cases of real "everyday mechanical engineering", different stresses act together in a component. In most of the chapters of this mechanics script *, however, only the individual load types are described in isolation from one another. The calculation of superimposed loads is shown in later parts of the script.

Load types - differentiation according to load distribution

Point load
With point load, a force acts on a single point.

Line load
In the case of a line load, a force is distributed on a line / section. The force can be distributed evenly or unevenly.

Area load
With a surface load, the force is distributed over a certain area. The force can be distributed evenly or unevenly.

Types of exposure - differentiation according to the course over time

The temporal course of a load means whether a force acts permanently or possibly has a dynamic course and is variable over time. A distinction is made between the following types of load:

1. static load
The acting force and its direction of action remain constant; one speaks here of a static or static load.

2. dynamic loading
The acting force and / or its direction of action change over time.
A further distinction is made between dynamic loads:

a) dynamic-swelling load
The acting force fluctuates between two or more values, which, however, are always above or below zero (the load direction does not change => e.g. no change between tension and pressure).

b) dynamically changing load
The acting force fluctuates between two or more values ‚Äč‚Äčthat are alternately above and below zero (e.g. there is a constant change between tension and pressure).

c) harmonic loading
The acting force can be swelling or alternating, but shows a harmonic course - very often sinusoidal (often found in rotating parts).

d) random loading
The amount and direction of the acting force is random and therefore unpredictable.

e) sudden loading
The acting force is particularly high but the duration of the effect is only very brief. The sudden load occurs, for example, in a car crash or an explosion.