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fonseh
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Question about shear flow / stress
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- Flow Shear Shear flow Stress
In summary: Consequently, the shear force across the nail in part b will be greater than the shear force across the nail in part a.In summary, the QB in part b is less than in part a, so the QB in part b is the red part only.
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PhanthomJay
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Nothing wrong with solution. Remember when determining bolt shear, use the full area of connected part when determining Q.fonseh said:
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Raeksis
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Sorry to bump this but when finding QB why can we not use one of the boards on the left or right? Why the center board?
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PhanthomJay
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You can do it that way and get the same result without having to divide by 2 when you use the center board, because now there is just one shear plane instead of 2 when using the first method.Raeksis said:
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Raeksis
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But I was thinking that only works here because the boards are the same dimensions.PhanthomJay said:
In a question like this below (b), if I use one of the side boards I get a different (wrong) answer than if I use the center board.
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PhanthomJay
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Part b is a bit more tricky than part a because in part b, the longitudinal shear flow across the nail is into the plane of the page (z direction) on the yz side face of a cubic element, in contrast to part a where the longitudinal shear flow across the nail is into the plane of the page (z direction) on the xz top face of a cubic element. Consequently, in part b, the shear flow is horizontally distributed across the top board, so you need to find Q based on the area of the board in between the nailed joints, and the vertical distance from its centroid to the neutral axis. Then divide result by 2 when determining shear flow, because there are 2 shear planes.Raeksis said:
Alternatively, you could use the Q of the area outside of the top cuts, but when so doing, you must use the full area , that is, the area of both vertical pieces times the vertical distance of its centroid to the neutral axis. This a more tedious way of finding it.
Part b is a stronger connection than part a, because the Q in part b is less.
FAQ: Question about shear flow / stress
1. What is shear flow/stress?
Shear flow or shear stress is a force that acts parallel to the surface of a material. It is caused by a combination of shear forces and shear strains, and is a measure of the resistance of a material to deformation due to shear forces.
2. What are the units of shear flow/stress?
The units of shear flow or stress depend on the system of measurement being used. In the SI system, shear stress is measured in newtons per square meter (N/m^2) or pascals (Pa). In the US customary system, it is measured in pounds per square inch (psi).
3. How is shear flow/stress calculated?
Shear flow or stress can be calculated by dividing the shear force acting on a material by its cross-sectional area. This gives the shear stress at a specific point on the material. To find the shear flow along the entire length of a material, the shear stress at each point must be multiplied by the distance from the neutral axis.
4. What is the neutral axis in shear flow/stress?
The neutral axis is an imaginary line that divides a material into two equal parts when subjected to bending or shear forces. It is the point at which there is no shear stress, and therefore no shear flow along the material.
5. What factors affect shear flow/stress in a material?
The amount of shear flow or stress in a material is influenced by several factors, including the magnitude and direction of the shear forces, the material's cross-sectional area, and its elastic modulus (a measure of its stiffness). The material's shape and geometry also play a role in determining its shear flow or stress.
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