Welding Force: Get a Closer Look

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Discussion Overview

The discussion revolves around the forces involved in welding, particularly focusing on the pressure applied to a valve and how it relates to the material properties of the flapper. Participants explore the relationship between airflow, pressure, and the resulting forces on the weld, considering both steady-state and transient conditions.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant suggests starting with a solution approach, indicating a need for initial ideas on tackling the problem.
  • Another participant expresses confusion about how airflow from the valve relates to the pressure and the force applied to the weld, noting the importance of material properties.
  • A participant proposes that if the flapper is not fully open, the lifting force can be determined, suggesting a starting point for calculations.
  • One participant calculates the total force applied to the valve as the product of the contact area and pressure but struggles with the implications of material flexibility.
  • Another participant argues that the problem lacks sufficient detail about the flapper material, providing examples of how different materials would affect the force experienced at the weld, and speculates on the range of possible forces.
  • A participant inquires whether knowledge of Young's modulus would allow for an equation to determine the maximum force at the weld.
  • One participant requests further assistance, indicating they are still grappling with the practical aspects of the problem.

Areas of Agreement / Disagreement

Participants express varying degrees of uncertainty and differing perspectives on the relationship between material properties and the forces involved. There is no consensus on a definitive approach or solution to the problem.

Contextual Notes

The discussion highlights limitations in the problem's description, particularly regarding the material properties of the flapper and the assumptions made about steady-state versus transient conditions. There are unresolved mathematical steps related to the application of pressure and material flexibility.

Who May Find This Useful

This discussion may be of interest to those involved in welding engineering, materials science, or anyone dealing with fluid dynamics in mechanical systems.

GZunich
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Homework Statement
There is a flapper valve that is a 4.5mm disc welded to a body with a 3.5mm opening. They are attached with a spot weld approximately 0.5x0.5mm. There is a maximum flow through the opening of 0.20684N/mm2. What is the maximum force seen on the spot weld?
Relevant Equations
M=wl^2/2
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Perhaps you could attempt a solution first? What do you think the best approach is for this problem?
 
I’m having trouble trying to figure out how to start. The pressure applied to the weld comes from the air flowing through the valve. It’s controlled by air flow, but does that come from the pressure?

I know this for will apply a force to the valve but the force applied to the weld will be controlled by the properties of the material. I don’t know what equation will take the material properties into account.
 
If the flapper is less than 100% open pushing against the stops, you know how much lifting force there is. Can you start from that?
 
I’ve gotten here: total area of contact with the airflow times the pressure gives you the total force applied to the valve. But from there is where I get confused because of how flexible the material is.
 
Yes, as I read the problem it is incomplete without the description of the flapper material. I assume the problem is asking about the steady state where the flapper is held open at some position. For example there would be nearly zero force on a flapper made of tissue paper, it would just open completely. Hardened steel 2cm thick would hardly move at all and would take the full force from the pressure given. I suppose my answer would be somewhere between 0 and 2N.
If they want the transient solution, where the valve is closed and by some miracle the pressure is instantly applied, then it will see the full force as it starts to accelerate to open.
 
If the young’s modulus E was known, would there be an equation to fit the maximum force seen at the weld?
 
Can anyone help? I’m still stuck on this real world problem
 

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