How to fix black strokes for contour detection

Hello, I’m new with openCV and I don’t know how to approach this problem.
I have some pictures for detect circles but the stroke seem to be so thin so I guess a dilate operation need to be performed.

I’ve tried HoughCircles but do not detect the circles, so I’m trying to detect it using findContours.
The problem is that the contour of a circle is being detect as several contours because it stroke is not smooth.

There is a way/process to dilate a black stroke and then smooth it?

Here is a picture example of a circle part and its detected contour