There will not be anyone preventing you from boarding. Train stations do not have barriers.
But on the train the conductor will want to see a piece of identity together with the ticket. What name does this ID have? If that matches you are fine. If not you will have to cancel the ticket, and buy a new one.
Trains are mass transit. Think subway, but with nicer trains and longer distances. It is not like an airline, so do not expect similar procedures.
When you buy tickets at the station, in stead of on line they are anonymous, and there you will have no name issues.