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Tensores

Abstract

Tensors As mentioned in the introduction, all laws of continuum mechanics must be formulated in terms of quantities that are independent of coordinates. It is the purpose of this chapter to introduce such mathematical entities. We shall begin by introducing a shorthand notation-the indicial notation-in Part A of this chapter, which will be followed by the concept of tensors introduced as a linear transformation in Part B. The basic field operations needed for continuum formulations are presented in Part C and their representations in curvilinear coordinates in Part D. Part A The Indicia1 Notation 2A1 Summation Convention, Dummy Indices Consider the sum s = a p l + as2 + a3x3 +-* + a,&,, (2A1.1) We can write the above equation in a compact form by using the summation sign: n s = ajxi i = l (2A1.2) It is obvious that the following equations have exactly the same meaning as Eq. (2A1.2) n j=l s = 2 ajxj (2A1.3) n s = c a m x m m = l (2A1.4) etc. 3