1. Example 1 A concrete sidewalk is constructed between two buildings on a day when the temperature is 25ºC. The sidewalk consists of two slabs, each 3m in length and of negligible thickness. As the temperature rises to 38ºC, the slabs expand, but no space is provided for thermal expansion. The buildings do not move, so the slabs buckle upward. Determine the vertical distance y in the drawing.

2. Example 2 The aluminum lid of a jar of dill pickles is stuck to the jar. To loosen the lid so it can be opened, hot water is poured over the lid causing it to expand. If the temp. increase of the lid and the glass is 40C°, calculate the change in circumference of the lid and the glass on which it is screwed. The diameter of the lid before heating is 22cm.

3. Example 3 A metal rod (metal A) that is 30 cm long expands by 0.0750 cm when its temperature is raised from 0.0ºC to 100ºC. A rod of a different material (metal B) and of the same length expands by 0.040 cm for the same rise in temperature. A third rod, also 30 cm long, is made up of pieces of each of the above metals placed end to end and expands 0.0550 cm between 0ºC and 100 ºC Find each portion of the composite bars.

8. Seatwork

9. Thermal Stress Develops when one tries to prevent the contraction or expansion of a material being subjected to temperature change The reason why bridges usually have gaps between sections is to permit expansion or contraction to occur without thermal stresses developing. Tensile stress happens when a rod with length Lo and cross section area A is held at constant length while the temperature is reduced (negative ∆T)[ or increased (positive ∆T) ]

10. Thermal Stress