Dynamic Strength - Hybrid Anisotropic Materials for Wind Power Turbine Blades - page 135

5.6.2 Strain-Stress Relation

Hook's. law. is. the. linear. strain-stress. relation. for. iberglass/carbon. power.
turbine. blades.. It. is. derived. from. the. elastic. energy. as. a. basic. postulate. in.
the.theory.of.elasticity..If.the.axis.of.geometry.blades.is.consistent.with.warp.
direction.of.iber,.Hook's.law.is.represented.by.Equation.(5.62): 14

µ

σ µ

xy

x
x

zx
z

e = - E σ - E σ

x y z

E

y

µ σ µ

xy y zy

e = σ - E - E σ

y x z

E

x y z

µ

µ σ yz

xz
x

z
z

e = σ - E σ -

z x y

E E

y

. . (5.62)

τ

xy

γ = ;

xy

G

xy

τ

yz

γ = ;

yz

G

yz

τ

zx
zx

γ =

zx

G

Here:
e x ,.e y,, .e z. are.linear.deformations.in.x,.y,.z.directions;
.γ xy ,.γ yz, .γ zx. are.angle.deformations;
.σ x ,.σ y ,.σ z .are.the.tension/compression.stresses.in.x,.y,.z.directions;
.τ xy ,.τ yz ,.τ zx. are.the.shear.stresses.act.in.plain.xy.and.transverse.xz,.yz.
.E x ,.E y , . E z. are.the.modulus.of.elasticity.in.x,.y,.z.directions;
.G xy ,.G yz ,.G zx. are.the.shear.modulus.of.elasticity;
μ xy. ,.μ xz. μ yz. are.the.Poison's.ratio,.the.irst.index.indicate.stress.direction,.the.
second.index.indicate.strain.direction.

Investigation. of. strength. hybrid. turbine. blades. begin. from. measuring.
deformation. and. estimating. stresses. in. different. points. of. the. blades.. The.
widely. used. resistance. strain. gauges,. which. are. the. most. universal,. have.
recently.become.popular.for.measuring.elastic.deformations.in.longitudinal,.
transverse,.and.diagonal.45°.directions. 15
The. gauges. loop's. inluence. on. accuracy. measurement. deformations. can.
be.corrected.using.coeficient.χ: 16