# Pressure wave vs. Shock wave in solid body

• tricha122
In summary: Remember, stress and strain are important concepts in understanding the behavior of materials under different conditions, and they can have significant implications in various fields such as engineering and physics.In summary, stress is the force applied to an object per unit area, while strain is the resulting deformation or change in shape of the object. Normal transmission of stress/strain refers to gradual and continuous distribution, while shock transmission occurs when there is a sudden and rapid increase. The speed of the pressure wave depends on the material properties and can lead to a shock wave if V > C. In the case of an elastic body exhibiting plasticity, the normal waves at initial impact
tricha122
Hi everyone,

I'm having some difficulty comprehending "normal" transmission of stress/strain through a solid body and "shock" transmission of stress/strain.

Imagine I have two bodies, one rigid - the other elastic.

If the rigid body is fixed in space, and the elastic body is flying at the rigid body with velocity V

At what speed does the pressure wave transmit backward through the elastic body upon impact with the rigid plate? Does this happen at the speed of sound in the medium (i.e. C = sqrt(K/row)). What if V >> C?
or V == C?

Finally, from what I have read, the "shock wave" comes from the increase in speed of sound through the medium with increasing pressure (density?) - and so if the elastic body exhibits plasticity & is crushed as it impacts the rigid plate - do the "normal waves" at initial impact get caught up with by "normal waves" of the compressed region a few milliseconds later, to form a shock?

I could be completely off base, I'm just trying to visualize the transmission of pressure/stress/strain through the solid body under impact.

Any help would be greatly appreciated!

ORF

Thank you for your question about the transmission of stress/strain through a solid body and the concept of shock waves. I can provide some information and clarification on these topics.

Firstly, let's define stress and strain. Stress is the force applied to an object per unit area, while strain is the resulting deformation or change in shape of the object. When a force is applied to a solid body, it will experience both stress and strain. In the case of a rigid body, the stress will be evenly distributed throughout the body and the strain will be minimal. However, in an elastic body, the stress will cause a deformation or strain in the body.

Now, let's address the concept of "normal" and "shock" transmission of stress/strain. Normal transmission refers to the gradual and continuous transmission of stress/strain through a solid body, where the stress is evenly distributed and the strain occurs gradually. On the other hand, shock transmission occurs when there is a sudden and rapid increase in stress/strain, resulting in a shock wave.

In your example of a rigid body and an elastic body colliding, the speed at which the pressure wave transmits backward through the elastic body will depend on the material properties of the elastic body. If the elastic body is made of a material with a low speed of sound, then the pressure wave will travel at a slower speed compared to a material with a higher speed of sound. This speed is often referred to as the "elastic wave speed" and is dependent on the material's stiffness and density.

If the velocity of the elastic body (V) is equal to the speed of sound (C) in the medium, then the pressure wave will travel at the speed of sound. However, if V is greater than C, then the pressure wave will travel at a speed faster than the speed of sound, and this is when a shock wave may occur. This is known as supersonic flow and can result in a sudden increase in stress/strain, causing a shock wave.

In the case of an elastic body that exhibits plasticity and is crushed upon impact with the rigid plate, the normal waves at initial impact will indeed get caught up with the normal waves of the compressed region a few milliseconds later, resulting in a shock wave. This is because the sudden increase in pressure and density in the compressed region will cause a rapid increase in the speed of sound, leading to a shock wave.

I hope this helps

## 1. What is the difference between a pressure wave and a shock wave in solid body?

A pressure wave is a type of mechanical wave that propagates through a medium, causing a temporary increase in pressure. On the other hand, a shock wave is a sudden and intense wave that travels faster than the speed of sound in the medium, resulting in a rapid increase in pressure and temperature.

## 2. How are pressure waves and shock waves produced in solid bodies?

Pressure waves can be produced by a variety of sources such as vibrations, impacts, or fluid flow. Shock waves, on the other hand, are typically produced by rapid and intense events such as explosions, supersonic aircraft, or meteorite impacts.

## 3. What are the effects of pressure waves and shock waves on solid bodies?

Pressure waves can cause temporary distortions or deformations in solid bodies, but usually do not cause permanent damage. Shock waves, on the other hand, can cause significant damage to solid bodies due to their intense and sudden increase in pressure and temperature.

## 4. Can pressure waves and shock waves be used for practical applications?

Yes, both pressure waves and shock waves have practical applications. Pressure waves are commonly used in non-destructive testing, ultrasonic imaging, and communication systems. Shock waves are used in various industries such as aerospace, medicine, and mining, for purposes such as material testing, shock therapy, and demolition.

## 5. How can we differentiate between a pressure wave and a shock wave in solid bodies?

One way to differentiate between a pressure wave and a shock wave is by examining the pressure and velocity changes. A pressure wave will cause a gradual increase in pressure and a corresponding decrease in velocity, while a shock wave will cause a sudden and intense increase in both pressure and velocity. Additionally, shock waves will have a steeper wavefront compared to pressure waves.

• Mechanics
Replies
8
Views
928
• Mechanics
Replies
5
Views
1K
• Mechanics
Replies
4
Views
1K
• Materials and Chemical Engineering
Replies
4
Views
2K
• Mechanics
Replies
1
Views
1K
• Introductory Physics Homework Help
Replies
23
Views
5K
• Mechanics
Replies
15
Views
7K
• Mechanics
Replies
1
Views
2K
• Engineering and Comp Sci Homework Help
Replies
1
Views
3K
• Other Physics Topics
Replies
4
Views
4K