relation between hingeJoint's "target velocity" and the object's angularVelocity

there's an object. it has a HingeJoint component. now, as I am sure "targetVelocity" property in hingeJoint isn't the same as the object's rigidbody.angularVelocity. I imagine it more as being some kind of relation between the object that has the "hingeJoint" and the object that this hingeJoint is connected to. some kind of relation of those objects' "rigidbody.angularVelocity" properties. at least that's what I am looking for. if I have a limp hingeJoint, I want to monitor the joint's "angularVelocity relation" between those bodies and save them to an array, so that, later on, I could input variables from that array to the joint's "targetVelocity" so that the joint behaves exactly as it was during the time when we were "saving" those properties to an array.

how to compute that "angularVelocity"s relation of those objects?

If I understand your question, you just need to query hingejoint.velocity. See