Tang Qiong, etc. You guys are like families here, and thanks for those countless favours you have done for me, for driving away my v vi AGRADECIMIENTOS nostalgia, for all the fun we have had together. Last of the last, special thanks to Salva for being so mature and tolerating my tempers. For now, in my eyes, you are as lovely as the winds in summer nights(Oops, which is invisible..). v vi ABSTRACT kinematic hardening developed during preloading. Another one, not usually commented in the literature, is the influence of the size of the actual yield surface in the predictions under some loading paths, even if the same stress-strain curve is employed. Since an accurate determination of the actual size of the yield surface is difficult in some materials, the stress path during multiaxial loading may facilitate this determination.