bending moment variation, Lab Reports of Stress Analysis

calculations and theory and applications of bending moment variation

Typology: Lab Reports

2019/2020

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DEPARTMENT OF MECHANICAL ENGINEERING
TECHNOLOGY
Faculty of Engineering and Built Environment
UNIVERSITY OF JOHANNESBURG
Doornfontein Campus
Experiment 3: Bending Moment Variation Away From the Point of
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By I. B. BABE
Student No: 218002346
Subject: Strength of Materials 3A
Date: 2021
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DEPARTMENT OF MECHANICAL ENGINEERING

TECHNOLOGY

Faculty of Engineering and Built Environment

UNIVERSITY OF JOHANNESBURG

Doornfontein Campus

Experiment 3: Bending Moment Variation Away From the Point of

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By I. B. BABE

Student No: 218002346

Subject: Strength of Materials 3A

Date: 2021

Aim:

To calculate the bending moment and compare it to the experimental value.

Assumptions:

 Beam is symmetrical in the plane along which bending occurs.  Only linear elasticity (up to proportionality limit) is analyzed.  Initially there is no deformation and there is no varying cross section.  Cross section of the beam is still plane after and during bending.  Appropriate proportions make it impossible for the beam to fail in any other way than because of bending (no buckling and so on).

Apparatus:

The Structure Test Frame (STR3) Hardware the bending moment in a beam, Beam, rolling pivot, Grooved hangers, cut position, support pivot, Moment arm, Supports, Force Sensor, “Set Zero” control. Figure 1 : Bending Moment Variation away from the P.O.L. (STR1012).

Procedure :

1. Set up the equipment as illustrated in Figure 1 such that the cut will be 140 mm from right support 2. Zero the force gauge before hanging any weights. 3. Measure the total distance between two supports (Total L)

140 ×3.924 + 440×RB = 0

RB = -1.249 N

∑ Fy =^0

RA – 3.924 – 1.249 = 0

RA = 5. 173 N

The bending moment at A is: MA = -3.924×0.14 = -0.549 Nm And the bending moment at the cut is: BMTheoritical = RB × ( 0.14 )=−1.249 × 0. BMTheoritical =−0.175 Nm Drawing the bending moment diagram:

  1. The experimental bending moment is: BM exp =0.125 × (−0.2) =0.025 Nm The forces of the masses are: W1 = 0.4kg×9.81 = 3.924 N W2 = 0.2kg ×^ 9.81=1.962^ N Drawing the force diagram:

The reactions at the supports are calculated using equilibrium equations:

∑ MA^ =^0

140 ×3.924 + 440×RB - 220×1.962 = 0

RB =−0.268 N

∑ Fy =^0

RB – 3.924 – 1.962 – 0.268 = 0

RA =6.154 N

The bending moment at A is: MA = -3.924×0.14 = -0.549 Nm At the point of application of the second mass: M 2 =−0.549+(−3.924 +6.154 ) × 0. M 2 =−0.0584 Nm And the bending moment at the cut is: BMTheoritical = RB × ( 0.14 )=−0.268 × 0. BMTheoritical =−0.0375 Nm Drawing the bending moment at the cut is:

And the bending moment at the cut is: BMTheoritical = RB × 0.14=2.051 × 0. BMTheoritical =0.287 Nm Drawing the bending moment diagram: