A two － dimensional axisymmetric model of friction hydro pillar processing （FHPP） was established base on
Gambit software ．Using the commercial computational fluid dynamics software Fluent ， the numerical simulation of plastic
metal flow pattern was carried out in steady phase of FHPP ．While keeping the other parameters constantly during the process
of numerical simulation ，the velocity field and static pressure field distribution change of ideal metal plastic fluid during the
forming process were analyzed by changing only one critical parameter respectively ，such as the radial clearance between metal
stud and the base hole ，the material viscosity ，the rotary speed of metal stud ，the feed rate of metal stud and the bottom shape
of the base hole ．The result show that the static pressure distribution of plastic metal is affected remarkably by the feed rate （i ．
e ．the axial force） and the material viscosity of metal stud ，and has little to do with the rotary speed and the radial clearance ．
Although the feed rate and the radial clearance have little influence on the velocity distribution of plastic metal ，the effect of
rotary speed is relatively remarkable ，especially for the material neighboring to the wall of the velocity inlet and nearby the
metal stud ．The flow condition of the plastic metal material can be improved by changing the bottom shape of the base hole ，
which can also reveal the reason why there exist some defects at the bottom of the hole ．The above － mentioned research can
provide some guidance to the future experimental study adopting appropriate parametric combination ，and can also lay solid
foundation for the future numerical simulation by thermo － mechanical coupling ．

aking the surface-contact model between rigid flat punch and elastic half-space as the research subject, and through comparing the results of analytical solution and numerical simulation by the finite element method (FEM) software MSC.Marc, it is determined that the non-uniform meshing method and the third grade FEM calculation are reliable as to the surface-contact problem with definite contact area. For the most fundamental surface-contact problem involved with friction hydro pillar processing in friction stitch welding, the normal stress on the contact surface increases quadratically from center to the marginal side. The diameter of the metal stud and the applied external load has more influence to the distribution of normal stress on the contact surface, while the influence of radial clearance, the material combination between the metal stud and the predrilled hole are relatively small.