A beam of square cross section is subjected to a bending moment m and ...
Cross Section of the Beam
The cross section of the beam is square in shape, which means all sides of the square are equal in length. Let's assume the length of each side of the square cross section is 'a'.
Bending Moment and Maximum Stress
When a beam is subjected to a bending moment, it experiences a variation of stress across its cross section. The maximum stress developed in the beam occurs at the furthest point from the neutral axis, which in this case is at the corners of the square cross section.
Given that the maximum stress developed is 100 MPa, we can use this information to determine the moment of inertia of the square cross section. The moment of inertia, denoted by 'I', is a property of the cross section that influences its resistance to bending.
Diagonal Direction Bending Moment
Now, let's consider the scenario where the diagonal of the square cross section takes a vertical and horizontal direction while the bending moment remains the same.
In this case, the diagonal of the square cross section divides it into two right-angled triangles. Each triangle has a base of 'a' and a height of 'a'.
Effect on Moment of Inertia
When the diagonal is vertical and horizontal, the centroid of the cross section shifts. The new centroid position is at the intersection of the diagonals, which is at a distance of 'a/2' from each side.
The moment of inertia of the square cross section in this case can be calculated using the parallel axis theorem. It is given by the sum of the moments of inertia of the two right-angled triangles formed by the diagonal.
The moment of inertia of a right-angled triangle about its centroid is given by (base^3 * height)/12. Since there are two triangles, the total moment of inertia is 2 * [(a^3 * a)/12].
Calculating the New Maximum Stress
The maximum stress developed in the beam can be calculated by dividing the bending moment (m) by the moment of inertia (I).
So, when the diagonal of the square cross section takes a vertical and horizontal direction, the new maximum stress can be calculated using the equation:
New Maximum Stress = m / [2 * (a^4 / 12)]
Now, you can calculate the new maximum stress using the given bending moment (m) and the length of each side of the square cross section (a).
To make sure you are not studying endlessly, EduRev has designed Mechanical Engineering study material, with Structured Courses, Videos, & Test Series. Plus get personalized analysis, doubt solving and improvement plans to achieve a great score in Mechanical Engineering.