Characterization of residual stress distribution in structural materials by neutron diffraction at CANAM infrastructure

Charles Hervoches, Miroslav Vrána

Nuclear Physics Institute of the CAS v.v.i., Řež 130, 250 68 Řež, Czech Republic

Residual stresses are phenomena that develop in all welded structures due to local heating and slight difference between the chemical composition of the welding material and welded parts. Stresses have direct influence on ductility and toughness of both weld metal and heat affected zone of the weld area, which affect the service life time of structures.

The two-axis diffractometer SPN-100 at the Center of Accelerators and Nuclear Analytical Methods (CANAM) in Řež, is an instrument dedicated to macro/micro strain scanning of polycrystalline materials. Recently, the diffractometer has been equipped with a new two-dimensional position sensitive detector (2D-PSD).

For sample positioning, in addition to standard x-y-z translation stage, a new six-axis robotic arm has been installed to allow more flexible manipulation of complex samples.

Fig. 1: Layout of the neutron strain/stress scanner at the large research infrastructure Center of Accelerators and Nuclear Analytical Methods (CANAM)

Recent neutron diffraction experimental results obtained with the upgraded tools will be presented, this include:

· Strain/stress distribution measurements in the vicinity of butt weld from spherical storage tank made of C-Mn unalloyed steel.

· Comparison of residual stresses obtained after joining thick sheets of structural steel by the laser welding and arc welding methods.

· Study of residual stresses in cold rotary swaged tungsten heavy alloy.