Individual contribution to PhD thesis as a part of bigger project I have a question related to the personal contribution to PhD thesis (physics, materials science), when it was a small part of a big project and there were no real hypothesis or problem in your thesis "topic" except "we have these samples, go investigate them and find some results to report on" 
(yes, it is not the right way to do projects, but it happens and a good lesson for the future, which projects you should avoid =/).

As an outcome, PhD thesis is based on results, half of which was obtained by collaborators (other students). It is rather common situation as far as I understood - one group prepares samples and performes characterization; then you, being from another group, get these samples and investigate them using different methods. But then you use results of the characterization (made not by you but it is a part of joint publication) in your thesis before discussing data you got by yourself, because it makes sense to show the characterization to have a complete story.

The question: is it acceptable to submit a PhD thesis written in this way, where you did about 50% of all discussed results, the rest is done by others and this rest is included in joined publications? Surely, in every chapter it is mentioned if you did the measurement or it was done by coauthor/collaborator.

Have a great day and thank you in advance!
Hope I could explain more or less clear, what I would like to know.
If it is acceptable to your institution, then it is acceptable. I think that in a lot of lab sciences people in a given lab collaborate with each other quite extensively to contribute to the overall goals. Doctoral theses arise in this environment just as you say. Some one (PI?) hacks off a piece of a larger problem and passes it to a student to develop and report on. If it has "acceptable" significance then the student has a thesis. Hopefully it also advances the larger goals of the organization. 

But this is largely due to the fact that, to do anything at all in such fields, that collaboration is required, along with the PI who provides the lab through grants. It can be quite different in other fields, but they have their own standards and processes. 



Of course, the student could see an opportunity for a smaller problem in the context of the larger one, just as the PI can. I don't mean to imply that it is always the PI that initiates it. Usually the student will check with the PI whether it is good to pursue the idea.