The materials properties

Pulsa este enlace.
Dilatation of alluminiums://www.youtube.com/watch?v=EWN_-mC9cPI
Dilatation of ironhttps://fq-experimentos.blogspot.com/2010/07/129-dilatacion-de-los-metales.html
What problems can have the dilatation of materials in the bridges and the railways?