5 - Total force due to traction
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Introduction to Total Force Calculation
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Welcome everyone! Today we are going to discuss how to calculate the total force due to traction in a cylindrical coordinate system. Can anyone remind me what we discussed about Linear Momentum Balance?
We talked about how it helps in analyzing forces in solids using different coordinate systems.
Exactly! Now, in cylindrical coordinates, we can simplify our calculations significantly. The key idea is to treat the traction as constant across the z planes. Can anyone tell me why we would want to do that?
It makes calculations easier by avoiding complex variations.
Correct! When we assume traction is constant, we simplify our total force computation. Let's visualize the cylindrical element and remember A for area as r∆θ∆z.
Understanding Taylor's Expansion
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Now let's talk about Taylor's expansion. When we include traction's behavior around the center of our cylindrical element, we focus on the z direction. Why do think we only deal with z coordinates?
Because we're considering how the traction changes with respect to the height?
Exactly! And remember, as the volume shrinks, those smaller order terms vanish in the calculations. This shows us the power of mathematical approximations. What is the outcome when we sum the traction forces on the z planes?
They cancel out and we get combined effects of partial derivatives?
That's right! Understanding how to manipulate these equations is essential.
Force on Radial and Angular Planes
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Next, let's break down how to calculate forces on the +r and −r planes. What is the relationship between the force and the traction at the center of these planes?
It’s similar to what we did with the z planes; we can use a constant value at the center for calculations.
Absolutely! And how do we address the areas of those planes?
By evaluating the curved edge times the height.
Exactly! This geometrical aspect is crucial in yielding the correct force outputs. How do those compare to forces on θ planes?
The areas are the same but we must consider the basis vector differences.
Combining Forces and Final Balance
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Finally, let’s discuss how we sum the forces from all the planes. How do we ensure we've covered everything in our balance equation?
By adding contributions systematically from each derived equation.
Correct! And when we take the limit as ∆V approaches zero, what happens to the smaller terms?
They disappear, giving us clean equations for the balance.
Nicely said! Remember, abstraction helps us see the essential differences between cylindrical coordinates and Cartesian systems. So why are these equations important?
They show detailed force interactions in solids based on their geometries.
Real-World Applications of Traction Forces
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To wrap up, let’s explore how the concept of traction forces applies in real-world scenarios. Can anyone think of examples where cylindrical coordinates are crucial?
Pipes carrying fluids — the flow would rely on these calculations.
Also in roller coasters or cylindrical tanks where pressure is involved!
Exactly! These principles help engineers design safe and efficient systems. By thoroughly mastering how to derive and analyze forces, you're equipped to tackle complex engineering challenges!
Introduction & Overview
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Quick Overview
Standard
The section elaborates on how to calculate the total force due to traction on different planes of a cylindrical element by simplifying the derivation process, focusing on constant traction and the implications of using Taylor's expansion. The outcome is a clarification of how forces are distributed in cylindrical coordinates.
Detailed
In this section, we explore the concept of total force due to traction in a cylindrical coordinate system. The force is derived from the traction acting across the cylindrical element's faces, particularly focusing on the +z, -z, +r, -r, +θ, and -θ planes.
- Recap of Previous Concepts: We begin with what was covered in the previous lecture regarding the formulation of Linear Momentum Balance (LMB) in cylindrical coordinates, illustrating the basic geometric configurations.
- Simplified Approach to Traction Calculation: By approximating traction as constant on z planes, and considering the area of these planes, we can compute the total force simply by multiplying traction by area, leading to the reinforcement of key equations and the mainstream understanding of how small order terms in Taylor's expansion influence the calculated forces.
- Force on r and θ Planes: For the forces exerted on the radial and angular planes, we maintain an approximation that simplifies calculations and allows an understanding of how geometric factors contribute to forces in cylindrical coordinates.
- Total Force Contribution: The total net force exhibiting on the cylindrical element consists of derived contributions combined over respective planes, shedding light on resultant interactions within the defined geometry.
- Final Balance and Implications: Conclusively, we encapsulate all derived forces into a structural equation that showcases how cylindrical coordinates differ from Cartesian systems, with additional terms necessitated by the geometric properties of cylindrical elements. This concludes our detailed exploration of traction forces and their implications in the realms of solid mechanics.
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Introduction to Total Force Calculation
Chapter 1 of 3
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Chapter Content
We have found the force due to traction on all the faces of the cylindrical element. We can add equations (1), (15) and (21) to obtain the total force on the cylindrical element due to traction to be (22).
Detailed Explanation
In this chunk, we summarize the approach taken to calculate the total force acting on all the faces of a cylindrical element due to traction. By reviewing earlier equations derived for the forces acting on various faces, we can consolidate these to form a comprehensive equation (denoted as (22)) representing the total traction force. This step involves the addition of calculated forces from each face, recognizing the contributions from different directions and their specific traction calculations.
Examples & Analogies
Imagine a balloon being pushed in various directions by hands from all sides. Each hand represents the traction force acting from a face of the balloon. The total push on the balloon (or total force due to traction) would be the sum of all individual pushes. In engineering, we often need to find the total effect of multiple forces on a structure, similar to this example.
Understanding Contributions from Different Faces
Chapter 2 of 3
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Chapter Content
Total force due to traction can be represented as follows: \( F = F_{+z} + F_{-z} + F_{+r} + F_{-r} + F_{+ heta} + F_{- heta} \).
Detailed Explanation
This equation articulates the total force as a sum of forces contributed by the six faces of the cylindrical element: two on the +z and -z planes, two on the +r and -r planes, and two on the +θ and -θ planes. Each term signifies the force contribution from that specific face due to traction. By understanding where each force originates from, one can analyze complex structures that experience varying stress conditions.
Examples & Analogies
Think of a cube where every side has a different group of friends pushing or pulling it. Each push or pull (traction force) from the sides can vary, and the total push on the cube would be the combined effort of all friends. Each friend represents a specific directional force, just as each face of the cylinder does in our analysis.
Equation Representation of Total Force
Chapter 3 of 3
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Chapter Content
Thus, the total force on the cylindrical element due to traction is calculated and represented mathematically in equation (22).
Detailed Explanation
The final step involves writing the total force equation explicitly. This reinforces the understanding that all contributions from the faces are accounted for in a systematic manner through a mathematical expression. This expression is crucial for subsequent analyses, which may include equations of motion or structural integrity assessments in real-world applications.
Examples & Analogies
When you calculate the total cost of ingredients for a recipe, each ingredient's price (like each face's traction force) is summed to get a final total. Just like the recipe needs exact measurements for flavor, engineers need precise calculations for forces to ensure stability and safety in structures.
Key Concepts
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Force Calculation: The total force due to traction in cylindrical coordinates is approached by approximating traction as constant.
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Taylor's Expansion: It simplifies the calculations by allowing us to focus on variation in a specific coordinate direction.
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Cylindrical vs Cartesian: The derived equations in cylindrical coordinates reveal additional intricacies not present in Cartesian systems.
Examples & Applications
A water tank that is cylindrical; forces acting on the walls must consider pressure variations.
Analyzing the motion of a cylindrical roller coaster where centripetal forces are crucial for safety.
Memory Aids
Interactive tools to help you remember key concepts
Rhymes
In a cylindrical plane, traction's the game; steady it may seem, yet forces can dream!
Stories
Imagine a water tank shaped like a cylinder. As the tank fills, the pressure evenly distributes forces on all walls, teaching us the essence of traction!
Memory Tools
To remember traction concepts, think 'T-C-A' for Traction, Cylindrical areas, and Assumed constants.
Acronyms
C-T-F for 'Constant Traction Forces' helps us connect back to what we learned today.
Flash Cards
Glossary
- Cylindrical Coordinates
A three-dimensional coordinate system that extends polar coordinates by adding a height component.
- Traction
The force acting on a material due to stress distribution across its surface.
- Linear Momentum Balance
A principle stating that the rate of change of momentum of a system is equal to the net force acting on it.
- Taylor's Expansion
A mathematical series that approximates a function as a sum of its derivatives at a certain point.
- Basis Vectors
Vectors that define the coordinate direction in a given coordinate system.
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