A close-coiled helical spring is made of 5 mm diameter wire coiled to ...
To determine the maximum shear stress in a spring made of 3 mm diameter wire coiled to 30 mm mean diameter, we can use the concept of shear stress in a close-coiled helical spring.
Given data:
- Diameter of wire for the first spring (D1) = 5 mm
- Mean diameter of the first spring (d1) = 50 mm
- Maximum shear stress in the first spring (τ1) = 20 N/mm²
The formula for calculating maximum shear stress in a close-coiled helical spring is given as:
τ = (16 * W * R) / (π * d^3 * n)
where:
τ = maximum shear stress (N/mm²)
W = axial force acting on the spring (N)
R = mean radius of the spring (mm)
d = diameter of the wire (mm)
n = number of active coils in the spring
The number of active coils (n) can be calculated using the formula:
n = (L - C) / (π * d)
where:
L = length of the spring (mm)
C = length of one coil (mm)
Now, let's calculate the maximum shear stress in the second spring.
Step 1: Calculate the number of active coils (n1) for the first spring
Given: C1 = π * d1 (length of one coil for the first spring)
Using the formula: n1 = (L - C1) / (π * d1)
Since the length of the spring is not given, we can assume a value for L (let's say 100 mm)
n1 = (100 - π * 5) / (π * 5) = (100 - 15.7) / 15.7 ≈ 5.36
Step 2: Calculate the mean radius (R1) for the first spring
Given: d1 = 5 mm
Using the formula: R1 = d1 / 2 = 5 / 2 = 2.5 mm
Step 3: Calculate the axial force (W) for both springs
Since the axial force is given as the same for both springs (let's assume W = 100 N)
Step 4: Calculate the maximum shear stress (τ2) for the second spring
Given: d2 = 3 mm, R2 = d2 / 2 = 1.5 mm
Using the formula: τ2 = (16 * 100 * 1.5) / (π * 3^3 * n1)
τ2 = (2400) / (27.57 * 5.36)
τ2 ≈ 56.0 N/mm²
Therefore, the maximum shear stress in the spring made of 3 mm diameter wire coiled to 30 mm mean diameter, under the action of the same force, will be approximately 56.0 N/mm² (option C).
A close-coiled helical spring is made of 5 mm diameter wire coiled to ...
Maximum shear stress = 16 * force*mean radius of the spring/ pie * diameter of wire^3 max shear stress1 / max shear stress 2 = R1*d2^3/R2*d1^3 20/ max shear stress 2 = 25 * 3^3/15*5^3 max shear stress 2 = 15*5^3*20/25*3^3 max shear stress 2 = 37500/675 max shear stress 2 =55.56 N/mm^2