Hello everyone, I have a really interesting question here. I am measuring the factor of friction between two different metals. My results are a beat cloudy. When I use Steel - Brass surfaces the factor of friction, μ is being reduced while I am increasing the applied force. In other side, when I use Steel - Aluminum surfaces, when I am increasing the applied force on the two materials the factor of friction, μ goes up. Anyone can explain what is happening? There is no measurement mistake, that' s guaranteed.