The beams can be square, rectangular, circular, I-shaped, triangular or any other shape they think will be successful. Ask the 'junior engineer' students to sketch their ideas for various beam designs before constructing the one they predict will have the best strength : beam weight ratio.

Have the students design a 7-inch long beam to span a 6-inch gap.

Explain that using less clay may increase their strength : beam weight ratio.

Give each team a 2-oz cube of polymer clay with which to make their own beam.

Divide the class into groups of two students each.

Challenge the students to design a beam that is very strong, but does not weigh very much. Use the cured length of polymer clay to demonstrate elastic deformation by showing that the polymer clay returns to its original shape after the weight is removed. Use an uncured length of polymer clay to demonstrate plastic deformation by putting it across a gap and showing that it bends, but does not spring back to its original shape, after a weight is added to it and removed.

Explain the concepts of stress, strain and deformation introduced in this lesson.

Tell them they will find out more about what engineers do in this activity.

Ask students to vote with a show of hands on the following question, 'Do engineers construct buildings with solid beams or hollow beams?' Tally responses on the board.

Cure one piece in the oven, but not the other piece.

Make two long, thin lengths of polymer clay for a demonstration.

If you want to cure the polymer clay with the students, preheat the oven to 130☌ (275☏).

For the stress testing, make sure you have a place, such as between two level tables, desks or chairs, to rest the beams and add weights.

Divide the 1.75 lbs of clay into 2-oz cubes (1¼ in cube size), resulting in 14 equal cubes.As you make your design, think about the stress and strain on the beam remember to keep material on the top and bottom surfaces where the stresses are the greatest! In this activity, you will design and build your own beam to find a good beam strength : beam weight ratio - you want to build a lightweight beam that can hold a lot of weight. This allows engineers to take away material from the inside of the beam where the stresses are minimal. Why do the hollow beam and I-beam perform as well as the solid beam? Due to the principles of stress and strain, the greatest tensile and compressive stresses are realized on the tops and bottoms of beams while the neutral axis (middle of the beam) experiences no stresses. Even though they weigh less, they can almost hold the same amount of weight as the solid beam! This means they have a much higher beam strength to beam weight ratio (written, beam strength : beam weight), and are more efficient and cost-effective to use in construction projects.

However, the hollow rectangle beam and the I-beam weigh less than half as much as the solid beam. The activity setup to stress test student-designed beams.Ĭopyright © Chris Yakacki, Integrated Teaching and Learning Program and Laboratory, University of Colorado at Boulder, 2003.The three types of beam designs shown in the drawing are all the same length, width and height. Perform data collection and analysis (ranking).

Describe the process of how engineers and scientists conduct materials testing to determine the ultimate tensile strength of a beam.Identify instances of elastic and plastic deformation.Recognize various engineered beam designs.Engineers specify the exact materials from which objects and structures should be made, so that walls support the weight of the roof, airplanes fly safely at high altitude, wheels do not fall off, chairs support the weight of people, bridges support the loads that travel them, shopping carts support groceries, and strollers support children, and so on.Īfter this activity, students should be able to: Civil engineers often use a system of beams and columns in their structural design, to keep us safe in our homes and schools. Engineers consider the forces of stress and strain in their choice of design and materials.

Beam breaks actimeter