does aliasing occur always if i sample a vibration in real world applications? I was reading about the aliasing effect and nyquist. I understand that aliasing effect occurs if the sampling rate is lower than twice the maximum frequency in the signal I want to sample. 

So I was wondering if aliasing is always in signal measurements. Example: If I have a vibrations sensor that has a max sample rate of 8kHz -> It can reconstruct signals till 4kHZ perfectly right?
But what about frequencies which occur also in the measurements with much higher frequencies? If there is a vibration with 16 kHz and because I sample with much lower rate, there could be aliasing in my measurement and false signals I don't know about? is this possible? That means i could have peaks in my measurements which are because of aliasing?
That is why, before sampling, a (steep) lowpass filter with cutoff frequency $f_c \leq \frac{f_s}{2}$ shall be applied. Thus, the amount of aliasing will be insignificant.