These materials are exposed to high stresses in an engine block, a railroad track or a gas turbine, for example. Casting, forming or hardening in the manufacturing process creates internal stresses, which Michael Hofmann can determine using neutrons at the research neutron source. He is head of the residual stress and texture group at the MLZ and is responsible for the STRESS-SPEC neutron diffractometer. Hofmann vividly introduced the audience to the measurement of residual stresses and showed how this is useful in the production of better materials for the automotive industry or gas turbines.

Gold examined with neutrons

In addition to the engineering and technical research examples, Michael Hofmann also had something for history buffs in his repertoire: archaeologists used his scientific instrument to examine gold and iron finds from the Celtic period with neutrons in order to find out how they were made.

Is stress in rails desired?

The great interest of the audience was evident after the presentation. Many asked questions or crowded Michael Hofmann after the official Q&A session. One gentleman wanted to know whether residual stresses in rails were actually desirable. Michael Hofmann knew: “In the rail’s head, the residual stresses caused by the manufacturing process are not harmful during operation. In the foot, they must not exceed a certain value.” Other questions that occupied the audience included the number of neutrons that arrive at Michael Hofmann’s measuring instrument (10 million per second and square centimeter) and how the neutrons are guided to the instrument.