Friction is a critical issue in plastic forming which influences forming force, metal flow, forming quality and service life of die. Since friction is a highly nonlinear physical phenomenon which is interactively affected by so many factors, great efforts have been made to study the friction mechanism and controlling. The research progress of friction issues in plastic forming was summarized and discussed from four aspects： testing, characterizing, modeling and optimization/controlling. Considering urgent demands for green, efficient and precise forming of high-performance, lightweight and complex components in high-tech industries such as aerospace and automotive, the trends and challenges of friction study in plastic forming were proposed.
The tribological conditions between tools and sheet are the major factors affecting the product quality,forming limits and service life of tools in thin-walled titanium components warm forming.Using the orthogonal design based twist compression test in the temperature range of 25-300 °C,the significant factors affecting the coefficient of friction（Co F） and the influencing rules in CP-3 titanium sheet warm forming are clarified and discussed by changing tribological conditions such as tool material,lubrication,temperature and normal pressure.The results show that the significant factors affecting the Co F are lubrication,surface roughness,tool material,sliding velocity,normal pressure and temperature;compared with unlubricated condition,the graphite and Mo S2 greatly improve the friction condition and the maximum reduction of the Co F is 0.318;the Co Fs of Cr12 Mo V/CP-3 and QAl10-3-1.5/CP-3 tribo-pairs show a similar tendency：the Co Fs increase with increasing surface roughness and sliding velocity,and increase firstly then decrease with increasing normal pressure and temperature.
