Stress and Strain

Stress and Strain

Today we spent our time discussing material strength – an important property in building materials if you want to make something that is able to withstand an earthquake! After a brief discussion of the various ways to stress and strain a material, the students experimented by bending paperclips, stretching rubber bands, and examining the light patterns in plastics as seen through polarizing films.

We learned that the strength of a material comes from its molecular structure. Students can explain why graphite is soft and diamond is hard even though they both have the same chemical formula: C (carbon). We also learned that introducing small flaws or impurities into a material’s crystal structure can actually strengthen the material, a fact blacksmiths have been exploiting for millennia.

 

Esfuerzo y deformación

Hoy discutimos sobre la resistencia de los materiales; una característica muy importante, en particular en los materiales de construcción si es que deseamos construir algo que sea capaz de soportar un terremoto. Después de una breve discusión sobre las variadas formas de esforzar y deformar materiales, los estudiantes experimentaron al doblar clips de papel, estirar bandas elásticas y examinar los patrones de luz que se generan al mirar el plástico a través de filtros polarizantes.

Aprendimos que la resistencia de un material proviene de su estructura molecular. Por ejemplo, los estudiantes son capaces de explicar por qué el grafito es blando y el diamante es duro, a pesar que ambos están compuestos por átomos de carbono. También aprendimos que al introducir pequeños defectos o impurezas en la estructura cristalina de un material, podemos aumentar la resistencia de éste.  Esta técnica ha sido ampliamente utilizada por los herreros desde la antigüedad.

 

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Author

Lauren Koppel

Lauren earned a Bachelor’s degree with a double major of Biology and Psychology from Clark University, and a Master of Education from the Harvard Graduate School of Education. During her undergraduate years, she worked in a evolutionary neurobiology lab that studied the neural development of annelids (marine worms), with a focus on the sox family of genes. Lauren loves learning about how the world works (including everything from biology to chemistry to engineering), and is passionate about sharing that knowledge and enthusiasm with others. In the past, she has interned at the Museum of Science, where she educated learners of all ages through hands-on activities, games, and experiments. Other science education organizations with which Lauren has worked include The People’s Science, EurekaFest, and Eureka! of Girls Inc. of Worcester. Currently she lives in Boston, where devotes her free time to playing Quidditch, reading sci-fi novels, playing her ukulele, and enjoying all the culinary delights the city has to offer.

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