Page 203 - Introduction to Continuum Mechanics

188 Stress

Fig. 4.8

Dividing by Ajt^A^A^ and letting A*/-» 0, we have

Since I,,. = Te, = 7J/ e ;-, therefore we have (noting that all e,- are of fixed directions in Cartesian
coordinates)

In invariant form, the above equation can be written

and in Cartesian component form