Jtam-A4.dvi JOURNAL OF THEORETICAL AND APPLIED MECHANICS 54, 3, pp. 743-755, Warsaw 2016 DOI: 10.15632/jtam-pl.54.3.743 GREEN’S FUNCTION FOR A MULTIFIELD MATERIAL WITH A HEAT SOURCE Bogdan Rogowski Lodz University of Technology, Department of Mechanics of Materials, Łódź, Poland e-mail: bogdan.rogowski@p.lodz.pl Green’s functions for a multifield material subjected to a point heat source are presented in an explicit analytical form. The study concerns the steady-state thermal loading infi- nite region, half-space region and two-constituent magneto-electro-thermo-elastic material region. The new mono-harmonic potential functions, obtained by the author, are used in the analysis. The elastic displacement, electric potential, magnetic potential and induced by those coupledmultifield physical quantities, caused by internal or external heat sources, are limited and presented in a very useful form, exactly and explicitly. Keywords:Green’s functions, pointheat source,multifieldmaterial,magneto-electro-thermo- -elastic fundamental solution, multifield composites, exact solution 1. Introduction The basic solutions, related among others to multifield materials, are Green’s functions, which were first proposed byGeorgeGreen in 1828. There are two different analysis processes for solu- tions in scientific literature.Onehas focusedon thedisplacement, electric potential andmagnetic potential, constructing equilibriumequations. The secondhas emphasized equilibriumequations of stresses, electric displacements andmagnetic inductions aswell as compatibility equations for strains. There is Stroh’s formalism (Stroh, 1958) andLekhnitskii’s approach (Lekhnitskii, 1963), for example. On the other hand, there are three commonly used methods in analyzing boun- dary effects: the theoretical solution, numerical solution and the experiment. But, appropriate Green’s functions for a thermoelastic half-space is a specific task. This is due to the fact that the fundamental solution for the displacements is not limited at infinity, which is inconsistent with themechanical sense. For example, Hou et al. (2008) derived a solution with a logarithmic singularity in the generalized displacement fields. Thus, the consideration of static equilibrium of the thermoelastic half-space, a quarter of the space, an octant, a wedge, and a half-wedge under the action of a unit point (aswell as distributed) of the internal heat source andboundary temperature or heat flux is a special and important task. The importance is dictated by the fact that the computational scheme ofmany structural elements is reduced to those volumematerial regions. In the context of multifield materials, the solutions depend on a large number of material parameters. For magneto-electro-thermo-elastic materials, it is twenty one, making any solu- tion other than explicit analytical one impractical. The exact formulae, in terms of elementary functions for multifield materials, are presented in this study. The generalized displacements have been obtained with an accuracy up to arbitrary constants, which do not affect the value of stresses. This is the major motivation of the study presented in this paper. Although it sounds theoretically more reasonable, experiment based verification is still desired. It ismentioned here that mono-harmonic potential functions can be found in Chen et al. (2004), but some simpler results, obtained by the author of this paper, are presented for the reader’s convenience. 744 B. Rogowski The exact solutions related to crack and contact problems of multifield materials were re- cently presented by Rogowski (2012-2015) for instance. 2. The thermoelastic fundamental solution for magneto-electro-thermo-elastic multifield materials 2.1. The fundamental equations for a magneto-electro-thermo-elastic medium We consider an axisymmetric problem. Assume that the field variables are functions of r and z in the cylindrical coordinate system (r,θ,z). Constitutive equations for a piezoelectric, piezomagnetic, electromagnetic and thermoelastic material polarized in the positive z-direction subjected to mechanical, thermal, magnetical and electrical fields can be written, in matrix representation, as    σr σθ σz σrz    =   c11 c12 c13 0 c12 c11 c13 0 c13 c13 c33 0 0 0 0 c44      ur,r−αrT ur/r−αrT uz,z−αzT ur,z +uz,r    +   0 e31 0 e31 0 e33 e15 0   { φ,r φ,z } +   0 q31 0 q31 0 q33 q15 0   { ψ,r ψ,z } { Dr Dz } = [ 0 0 0 e15 e31 e31 e33 0 ]    ur,r+αrT ur/r+αrT uz,z +αzT ur,z+uz,r    − [ ε11 0 0 ε33 ]{ φ,r φ,z } − [ d11 0 0 d33 ]{ ψ,r ψ,z } { Br Bz } = [ 0 0 0 q15 q31 q31 q33 0 ]    ur,r+αrT ur/r+αrT uz,z +αzT ur,z+uz,r    − [ d11 0 0 d33 ]{ φ,r φ,z } − [ µ11 0 0 µ33 ]{ ψ,r ψ,z } (2.1) where σij, Di, Bi are mechanical stresses, electric displacements and magnetic inductions, re- spectively; T is a temperature change; c11, c12, c13, c33, c44 denote elastic stiffness; ε11, ε33, and µ11, µ33 denote dielectric permittivities and magnetic permeabilities, respectively; ekl, qkl and dll are piezoelectric, piezomagnetic andmagnetoelectric coefficients, respectively, and ur, uz are mechanical displacements, while φ and ψ are electric andmagnetic potentials, respectively; αr and αz are thermal expansion coefficients. The subscripts following a comma denote partial differentation with respect to the indicated variables.Wemention that various uncoupled cases can be reduced by setting the appropriate coupling coefficients to zero. The equilibrium equations and theMaxwell equations, in the absence of body forces, electric andmagnetic charge densities are given by ∂σr ∂r + ∂σrz ∂z + σr −σθ r =0 ∂σrz ∂r + ∂σz ∂z + σrz r =0 ∂Dr ∂r + ∂Dz ∂z + Dr r =0 ∂Br ∂r + ∂Bz ∂z + Br r =0 (2.2) The temperature field in the medium without heat generation in a steady-state is governed by the following equation λr (∂2T ∂r2 + 1 r ∂T ∂r ) +λz ∂2T ∂z2 =0 (2.3) where λr, λz are coefficients of thermal conductivity. Substituting constitutive equations (2.1) into equilibrium equations (2.2) yields the basic governing equilibrium equations for the displa- Green’s function for a multifield material with a heat source 745 cements ur and uz, electric potential φ andmagnetic potential ψ as follows c11B1ur+ c44D 2ur +(c13+ c44)D ∂uz ∂r +(e15+e31)D ∂φ ∂r +(q15+ q31)D ∂ψ ∂r −β1 ∂T ∂r =0 c44B0uz + c33D 2uz +(c13+ c44)D ∂[rur] r∂r +(e15B0+e33D 2)φ +(q15B0+q33D 2)ψ−β3DT =0 (e15+e31)D ∂[rur] r∂r +(e15B0+e33D 2)uz − (ε11B0+e33D2)φ − (d11B0+d33D2)ψ+p3DT =0 (q15+q31)D ∂[rur] r∂r +(q15B0+q33D 2)uz − (d11B0+d33D2)φ − (µ11B0+µ33D2)ψ+γ3DT =0 (2.4) where the following differential operators have been introduced Bk = ∂2 ∂r2 + 1 r ∂ ∂r − k r2 k =0,1 D = ∂ ∂z D2 = ∂2 ∂z2 (2.5) In addition, βi are the thermal moduli and p3, γ3 are pyroelectric and pyromagnetic constants, respectively, defined by β1 =(c11+ c12)αr + c13αz β3 =2c13αr+ c33αz p3 =2e31αr +e33αz γ3 =2q31αr + q33αz (2.6) Equations (2.1) to (2.3) contain 13 equations and 13 unknowns. The 13 unknowns are: two elastic displacements, fourth stresses, two electric displacements and two magnetic inductions, one electric and onemagnetic potential and temperature change of the body. Therefore, the 13 unknowns can be determined by solving the 13 equations (2.1) to (2.3). The governing equations are generalized equilibrium equations (2.4) and heat conduction equation (2.3), which induces five unknowns. These are: two displacements, one electric and one magnetic potential and temperature change of the body. The transversely isotropic multifield material is characterized by 17 material constants. If the effect of temperature change is taken into account then also four thermal constants appear in the analysis. Based on the method named the Schmidt method (Morse and Feshbach, 1953) the general solution to the governing equations are obtained by the generalized Almansi theorem. Then equations (2.4) can be further simplified to ur(r,z) = 4∑ i=0 α1iλi ∂ϕi ∂r uz(r,z) = 4∑ i=0 1 λi ∂ϕi ∂z φ(r,z) =− 4∑ i=0 α3i λi ∂ϕi ∂z ψ(r,z) =− 4∑ i=0 α4i λi ∂ϕi ∂z T(r,z) = α00 λ20 ∂2ϕ0 ∂z2 (2.7) where a1i = a1λ 6 i + b1λ 4 i + c1λ 2 i +d1 a2λ 6 i + b2λ 4 i + c2λ 2 i +d2 1 λ2i a3i = a3λ 6 i + b3λ 4 i + c3λ 2 i +d3 a2λ 6 i + b2λ 4 i + c2λ 2 i +d2 a4i = a4λ 6 i + b4λ 4 i + c4λ 2 i +d4 a2λ 6 i + b2λ 4 i + c2λ 2 i +d2 a00 = aλ80+ bλ 6 0+ cλ 4 0+dλ 2 0+e a2λ 6 0+ b2λ 4 0+ c2λ 2 0+d2 (2.8) 746 B. Rogowski where λ20 = λr/λz and λ 2 i are the roots of the following characteristic algebraic equation aλ8+ bλ6+ cλ4+dλ2+e =0 (2.9) whose parameters a, b, c, d and e and roots (eigenvalues) λ2i (i =1,2,3,4) are given in Appen- dix A. Themono-harmonic functions satisfy the equations ( ∆+ 1 λ2i ∂2 ∂z2 ) ϕi(r,z) = 0 i =0,1,2,3,4 (2.10) The parameters a1, b1, c1, d1, b2, c2, d2 and coefficients a3i and a4i, which are defined by the coefficient a1i, are listed in Appendix A for the reader’s convenience. The stresses are σr =− 4∑ i=0 α5i λi ∂2ϕi ∂z2 − (c11− c12) ur r −β1T σθ =− 4∑ i=0 α5i λi ∂2ϕi ∂z2 − (c11− c12) ∂ur ∂r −β1T σz = 4∑ i=0 α5i λ3i ∂2ϕi ∂z2 +λ−20 β1T σzr = 4∑ i=0 α5i λi ∂2ϕi ∂r∂z +λ−20 β1a00 ∂2ϕ0 ∂r∂z (2.11) where a5i = c11a1i− c13+e31a3i+q31a4i (2.12) The components of the electric field vector Er and Ez are Er =− ∂φ ∂r = 4∑ i=0 α3i λi ∂2ϕi ∂r∂z Ez =− ∂φ ∂z = 4∑ i=0 α3i λi ∂2ϕi ∂z2 (2.13) The electric displacements are Dr = e15 (∂ur ∂z + ∂uz ∂r ) +ε11Er+d11Hr = 4∑ i=0 a6iλi ∂2ϕi ∂r∂z Dz = e31 (∂ur ∂r + ur r ) +e33 ∂uz ∂z +ε33Ez +d33Hz+β3T = 4∑ i=0 a6i λi ∂2ϕi ∂z2 (2.14) where a6i = e15a1i+ e15+ε11a3i+d11a4i λ2i (2.15) The components of the magnetic field vector Hr and Hz are Hr =− ∂ψ ∂r = 4∑ i=0 α4i λi ∂2ϕi ∂r∂z Hz =− ∂ψ ∂z = 4∑ i=0 α4i λi ∂2ϕi ∂z2 (2.16) Themagnetic inductions are Br = q15 (∂ur ∂z + ∂uz ∂r ) +µ11Hr+d11Er = 4∑ i=0 a7iλi ∂2ϕi ∂r∂z Bz = q31 (∂ur ∂r + ur r ) +q33 ∂uz ∂z +µ33Hz +d33Ez +γ3T = 4∑ i=0 a7i λi ∂2ϕi ∂z2 (2.17) where a7i = q15a1i+ q15+µ11a4i+d11a3i λ2i (2.18) Green’s function for a multifield material with a heat source 747 3. Thermal problems for multifield materials Consider the problemof a point heat source placedwithin themultifieldmaterial. Introduce the following mono-harmonic functions, which are even functions with respect to the z-coordinate ϕi(r,zi)= Ai [ ziarcsinh (zi r ) −Ri ] zi = λiz Ri = √ r2+z2i i =0,1,2,3,4 (3.1) where Ai are constants to be determined. The derivatives ϕi are as follows ∂ϕi ∂r =− Ri r ∂ϕi ∂zi =arcsinh (zi r ) ∂2ϕi ∂r∂zi =− zi rRi ∂2ϕi ∂z2i = 1 Ri ∂2ϕi ∂r2 = z2i r2Ri ∂2ϕi ∂r2 + 1 r ∂ϕi ∂r + ∂2ϕi ∂z2i =0 (3.2) The physical multifields are as follows ur =− ∑ Aia1iλi Ri r (uz,φ,ψ) = ∑ Ai(1,−a3i,−a4i)arcsinh (zi r ) T = A0a00 1 R0 ∂T ∂z =−A0a00 λ20z R30 ∂T ∂r =−A0a00 r R30 σr =− ∑ Aia5iλi 1 Ri +(c11− c12) ∑ Aia1iλi Ri r2 −β1T σθ =− ∑ Aia5iλi 1 Ri − (c11− c12) ∑ Aia1iλi (Ri r2 − 1 Ri ) −β1T σz = ∑ Ai a5i λi 1 Ri + β1 λ20 T σzr =− ∑ Aia5i zi rRi − β1 λ0 z r T Er =− ∑ Aia3i zi rRi Ez = ∑ Aia3iλi 1 Ri Hr =− ∑ Aia4i zi rRi Hz = ∑ Aia4iλi 1 Ri Dr = ∑ Aia6iλ 2 i zi rRi Dz = ∑ Aia6iλi 1 Ri Br = ∑ Aia7iλ 2 i zi rRi Bz = ∑ Aia7iλi 1 Ri (3.3) where the following abbreviation notation is used ∑ = ∑4 i=0. Fig. 1. A point heat source 2Q in an infinite multifield material When we use the physical consideration that the total heat flux transmitted through a cylinder 0 ¬ z ¬ a, r ¬ b must be equal to a point heat source Q (see Fig. 1), the following equation can be written 748 B. Rogowski −2πλz b∫ 0 ∂T ∂z (r,a)r dr−2πλr a∫ 0 ∂T ∂r (b,z) dz = Q (3.4) The substitution of Eq(3.3)4,5 and integrations yields Q 2π = λzλ 2 0aa00A0 b∫ 0 r √ (r2+λ20a 2)3 dr+λrb 2a00A0 a∫ 0 1 √ (b2+λ20z 2)3 dz = λraa00A0 ( − 1√ r2+λ20a 2 )∣∣∣∣ b 0 −λra00A0 ( 1− z√ b2+λ20z 2 )∣∣∣∣ a 0 = λra00A0 ( − a √ b2+λ20a 2 + 1 λ0 + a √ b2+λ20a 2 ) = a00A0 √ λrλz (3.5) that is A0 = Q 2πa00 √ λrλz (3.6) Note that in an infinite medium with the point heat source 2Q, the constant A0 assumes the same value. The temperature and heat fluxes are T = Q 2π √ λrλz 1 R0 λz ∂T ∂z =−Q 2π λ0z R30 λr ∂T ∂r =−Q 2π λ0r R30 (3.7) Of course λr (∂2T ∂r2 + 1 r ∂T ∂r ) +λz ∂2T ∂z2 =0 (3.8) 3.1. The half-space problem The boundary conditions and the corresponding equations for Ai are (a) σzr(r,0)= 0 is identically satisfied (b) σz(r,0)= 0 4∑ i=1 Ai a5i λi + Q 2πλza00 (β1a00 λ0 +a50 ) 1 λ20 =0 (c) Dz(r,0)= 0 4∑ i=1 Aia6iλi+ Q 2πλza00 a60 =0 (d) Bz(r,0)= 0 4∑ i=1 Aia7iλi+ Q 2πλza00 a70 =0 (e) ur is finite at r =0 4∑ i=1 Aia1iλ 2 i + Q 2πλza00 a10λ0 =0 (3.9) Thus, the coupled field in a semi-infinite transversely isotropic multifieldmaterial is determined by solution (3.3) and the following constants Aiλi   A1λ1 A2λ2 A3λ3 A4λ4   =− Q 2πλza00   a51 λ21 a52 λ22 a53 λ23 a54 λ24 a61 a62 a63 a64 a71 a72 a73 a74 a11λ1 a12λ2 a13λ3 a14λ4   −1   1 λ20 (β1a00 λ0 +a50 ) a60 a70 a10λ0   (3.10) Green’s function for a multifield material with a heat source 749 Generally, the permittivity and permeability of air or vacuum is about 680 and 475 times smaller, respectively, than that of commercial multifield materials. In reality, Dz and Bz do not transmit through the free boundary of half-space as assumed in conditions (c) and (d) of equations (3.9). It can be seen from equations (3.10) and (3.3) that Green’s functions for point heat sources applied on the boundary of the half-space are expressed exactly and explicitly in terms of elementary functions. This will be greatly beneficial to the succeeding analysis of thermoelastic problems of magneto-electro-thermo-elastic materials. Note that the total heat flux transmitted through the free boundary z =0 is Q+2πλz ∞∫ 0 ∂T ∂z r dr = Q+Q λ0z R0 ∣∣∣∣ ∞ 0 = Q−Q =0 (3.11) This is a confirmation of the correctness of the obtained result. Note again that a5i = c11a1i− c13+e31a3i+q31a4i a6i = e15a1i+ e15+ε11a3i+d11a4i λ2i a7i = q15a1i+ q15+µ11a4i+d11a3i λ2i (3.12) and a1i, a3i, a4i are defined by equations (3.15), see also very coupled but alternative equations (A2) and (A3) in Appendix A and equations (3.22) in special cases. 3.2. An infinite body containing a point heat source 2Q If 4∑ i=0 Aia1iλ 2 i =0 and 4∑ i=0 Ai(1,−a3i,−a4i)= 0 (3.13) then the generalized displacements ur, uz, φ and ψ caused by the internal heat source 2Q are limited, but they cannot be calculated in the neighborhood of the z-axis, that is when r → 0. The displacements which are obtained with an accuracy up to an arbitrary constant do not affect the value of stresses. Arbitrary constants can be treated as linear displacements of the medium as a rigid body in the axial direction without rotation. The solution to algebraic system of equations (3.13) is   A1 A2 A3 A4   =− Q 2πa00 √ λrλz   1 1 1 1 a31 a32 a33 a34 a41 a42 a43 a44 a11λ 2 1 a12λ 2 2 a13λ 2 3 a14λ 2 4   −1  1 a30 a40 a10λ 2 0   (3.14) where the coefficients a1i, a3i, a4i for i =0,1,2,3,4 are as follows    a1i a3i a4i    =   (e31+e15)λ 2 i ε11−ε33λ2i d11−d33λ2i (q31+q15)λ 2 i d11−d33λ2i µ11−µ33λ2i c11+ c13λ 2 i e31+e33λ 2 i q31+ q33λ 2 i   −1  e33λ 2 i −e15+p3a00λiδi0 q33λ 2 i − q15+γ3a00λiδi0 c33λ 2 i + c13− (β3+β1λ −2 i )a00λiδi0    (3.15) This is an alternative and simpler form of parameters defined by equations (A2) and (A3). Note that the units of the elements of the last matrix are for typical multifield materials [e] =C/m2 [p3] = 10 −6C/(m2K) [a00] = 10 6K [p3a00] =C/m 2 [q] = 102N/(Am) [γ3] = 10 −4N/(AmK) [γ3a00] = 10 2N/(Am) [c] = 1010N/m2 [β1,β3] = 10 4N/(m2K) [(β1,β3)a00] = 10 10N/m2 (3.16) with the multiplier ∈ 〈1,10〉. 750 B. Rogowski This states that the constituents of the sums are of the same order in each row of the last matrix in (3.15). Green’s functions for the internal heat source applied in multifield materials are determi- ned by equations (3.3), (3.14) and (3.15). All physical components of multifield materials are expressed in forms of elementary functions. It is very simple and straightforward to give nu- merical results. The results may help the understanding of behaviour of “smart” devices and “intelligent” structures made by multifield materials. 3.3. Single phase materials and multifield composite materials Multifield composite materials usually comprise alternating piezoelectric and piezomagnetic materials. If the material is piezoelectric then we define the matrix CE =   (e31+e15)λ 2 i ε11−ε33λ2i 0 0 0 −∞ c11+ c13λ 2 i e31+e33λ 2 i 0   (3.17) and its inverse matrix C −1 E = 1 ∆E   e31+e33λ 2 i 0 −(ε11−ε33λ2i) −(c11+ c13λ2i) 0 (e31+e15)λ2i 0 0 0   ∆E =(e31+e15)λ 2 i(e31+e33λ 2 i)− (c11+c13λ2i)(ε11−ε33λ2i) (3.18) Of course CEC −1 E =   1 0 0 0 1 0 0 0 1   (3.19) For piezomagnetic material, it is CH =   0 −∞ 0 (q31+q15)λ 2 i 0 µ11−µ33λ2i c11+c13λ 2 i 0 q31+ q33λ 2 i   (3.20) Then we obtain C −1 H = 1 ∆H   0 q31+q33λ 2 i −(µ11−µ33λ2i) 0 0 0 0 −(c11+ c13λ2i) (q31+q15)λ2i   ∆H =(q31+q15)λ 2 i(q31+q33λ 2 i)− (c11+ c13λ2i)(µ11−µ33λ2i) (3.21) whereCHC −1 H = I; I is the square unit matrix. Thus { a1i a3i }E = 1 ∆E [ e31+e33λ 2 i −(ε11−ε33λ2i) −(c11+ c13λ2i) (e31+e15)λ2i ]{ e33λ 2 i −e15+p3a00λiδi0 c33λ 2 i + c13− (β3+β1λ −2 i )a00λiδi0 } { a1i a4i }H = 1 ∆H [ q31+q33λ 2 i −(µ11−µ33λ2i) −(c11+ c13λ2i) (q31+q15)λ2i ]{ q33λ 2 i −q15+γ3a00λiδi0 c33λ 2 i + c13− (β3+β1λ −2 i )a00λiδi0 } (3.22) respectively for the piezoelectric and piezomagnetic thermoelastic materials. Green’s function for a multifield material with a heat source 751 Note that for the piezoelectric material is a4i =0, but a3i defines a7i, that is also Bz by the electromagnetic constant d11. Similarly is for the piezomagnetic material where a3i =0, but a4i defines a6i, that is also Dz as a consequence of the electromagnetic effect (see equations (3.12)). Fore the two-phase multifield material, the constant A0 will be A0 = Q π ( a00 √ λrλz +a ′ 00 √ λ′rλ ′ z ) (3.23) where the material parameter of the second material is denoted by prime. The inverse matrices are obtained as arithmetically average values in this case. Since the plane z =0 is a plane of symmetry (σzr =0, Hr =0, Er =0, uz =0, φ =0 and ψ =0 on this plane), the solutions may be used for the two-phase multifield composite material. 3.4. Solution for a purely thermoelastic material For a transversely isotropic thermoelastic medium, the temperature field is the same as that obtained in Section 3 anddescribedby equations (3.7). The thermoelastic solution for the purely elastic problem can be easily derived from that of the piezoelectricmaterial (on assumption that ε11 − ε33λ2i → ∞ and e31 = e33 = e15 = 0) or the piezomagnetic material (by assuming µ11−µ33λ2i →∞ and q31 = q33 = q15 =0). Both formulae (3.22) give the same result a1i = c33λ 2 i + c13− (β3+β1λ −2 i )a00λiδi0 c11+ c13λ 2 i i =0,1,2 (3.24) and equations (2.12) and (2.8) yield a5i = c11a1i− c13 a00 = c44c33(λ 2 0−λ21)(λ20−λ22) β1(c33λ 2 0− c44)−β3λ20(c13+ c44) (3.25) The remainingmaterial parameters a3i, a4i, a6i and a7i vanish. The constants A1 and A2 are obtained as follows A1 =− Qλ1 2πλra00 ( β1a00 λ0 +a50 ) a12λ 3 2−a10a52λ30 a51a12λ 3 2−a52a11λ31 A2 = Qλ2 2πλra00 ( β1a00 λ0 +a50 ) a11λ 3 1−a10a51λ30 a51a12λ 3 2−a52a11λ31 (3.26) for the half-space problem and A1 =− Q 2πa00 √ λrλz a12λ 2 2−a10λ20 a12λ 2 2−a11λ21 A2 = Q 2πa00 √ λrλz a11λ 2 1−a10λ20 a12λ 2 2−a11λ21 (3.27) for an infinite body. The parameters λ1 and λ2 are the roots of the following equation c33c44λ 4− [c11c33− c13(c13+2c44)]λ2+ c11c44 =0 (3.28) These parameters are the eigenvalues of the transversely isotropic material. By defining α = √ c11c33−c13(2c44 +c13)+2c44 √ c11c33 c33c44 β = √ c11c33− c13(2c44+ c13)−2c44 √ c11c33 c33c44 (3.29) 752 B. Rogowski the eigenvalues λ1 and λ2 can be written as λ1 = 1 2 (α+β) λ2 = 1 2 (α−β) (3.30) It is noted that λ1 and λ2 can be either two positive real numbers or complex conjugatewith a positive real part. In other words, α = λ1+λ2 and it is always real. The results are valid even for the degenerate case of β = λ1−λ2 =0, including the isotropic material where λ1 = λ2 =1. In this case, the limiting calculations with the use of de l’Hospital’s rule give the solution. 4. Conclusions • In comparison with the traditional methods applied to the solution of boundary value problems of thermoelasticity, in the proposedmethod, there is no need to solve boundary value problems of heat conduction for preliminary determination of the temperature field (the first stage of solving the problem) and then to solve the equations of thermoelasticity (the second stage of solving the problem). • Green’s functions for the half-space, infinite space made bymultifield materials are obta- ined in an exact analytical form; the solutions are regular. • For the temperature and heat flux applied along the circumference on an arbitrary plane, the thermal loading conditionsmay bewritten bymeans of theDirac delta function.Then integration and/or superposition of Green’s functions gives the multi-field result. Appendix A. The material coefficients for mulifield materials A1. Thematerial parameters in characteristic equation (2.9) are as follows a = c44[µ33e 2 33+ε33q 2 33+ c33µ33ε33−d33(c33d33+2e33q33)] b = µ33{(e31+e15)[2c13e33− c33(e31+e15)]+2c44e33e31− c11e233− c33c44ε11} +ε33{(q31+q15)[2c13q33− c33(q31+q15)]+2c44q33q31− c11q233− c33c44µ11} −µ33ε33c̃2− (e31+e15)2q233− (q31+ q15)2e233−c44µ11e233− c44ε11q233 +2e33q33(q31+q15)(e31+e15)+d 2 33c̃ 2+2c33d33(e31+e15)(q31+ q15) +2c44c33d11d33+2e33q33(c44d11+ c11d33)−2d33(c13+ c44)[e33(q31+ q15) +q33(e31+e15)] c = µ33{2e15[c11e33− c13(e31+e15)]+ c44e231+ε11c̃2} +ε33{2q15[c11q33− c13(q31+q15)]+ c44q231+µ11c̃2} + c33c44µ11ε11+ c11c44µ33ε33+2(c13+ c44)(q31+q15)(d11e33+d33e15−q33ε11) +2(c13+ c44)(e31+e15)(d11q33+d33q15−e33µ11) +(q31+q15) 2(c33ε11+2e33e15)+(e31+e15) 2(c33µ11+2q33q15) −2(q31+q15)(e31+e15)(e33q15+ q33e15+ c33d11+c44d33) −2c11d33(e33q15+q33e15)−2c44d11(q33e15+e33q15) −2c11d11q33e33−2c44d33q15e15+2c44q15q33ε11 +2c44e15e33µ11+ c11q 2 33ε11+ c11e 2 33µ11−2c̃2d33d11− c11c44d233− c44c33d211 Green’s function for a multifield material with a heat source 753 d =−c11µ33(c44ε11+e215)−c11ε33(c44µ11+q215)−c44(e231µ11+q231ε11)−e231q215−q231e215 −µ11ε11c̃2+d11c̃2+2c11c44d11d33+2c13q15q31ε11+2c13e15e31µ11−2c11q15q33ε11 −2c11e15e33µ11+2c13q215ε11+2c13e215µ11+2e31e15q31q15+2c11e15q15d33 +d11[−2c13e15(q15+q31)−2c13q15(e15+e31)]+d11[2c11(e15q33+ q15e33)+2c44e31q31] e = c11[µ11e 2 15+ε11q 2 15+ c44ε11µ11−d11(c44d11+2e15q15)] c̃2 = c11c33− c13(c13+2c44) A2. The parameters a1, b1, c1, d1, and a2, b2, c2, d2 in Eq. (2.8) are a1 = β1[c33(ε33µ33−d233)+µ33e233+ε33q233−2e33d33q33]+β3[−(c13+ c44)(ε33µ33−d233) − (e31+e15)(µ33e33−d33q33)− (q31+ q15)(q33ε33−d33e33)] +γ3[−(c13+ c44)(d33e33−q33ε33)+(e31+e15)(d33c33+q33e33) − (q31+q15)(c33ε33+e233)]+p3[−(c13+ c44)(d33q33−e33µ33) +(q31+q15)(d33c33+q33e33)− (e31+e15)(c33µ33+q233)] b1 = β1[c33(2d11d33−ε33µ11−µ33ε11)+ c44(d233−ε33µ33)−ε11q233−µ11e233 +2d33(e33q15+q33e15)+2d11e33q33−2q15q33ε33−2e15e33µ33] +β3[−(c13+c44)(2d11d33−ε33µ11−µ33ε11) +(q13+q15)(q15ε33+q33ε15−d11e33−d33e15) +(e31+e15)(e15µ33+e33µ11−d11q33−d11q15)] +γ3[(c13+c44)(d11e33+d33e15−q15ε33− q33ε11) − (e31+e15)(c44d33+ c33d11+q15e33+e15q33)+(q31+q15)(c44ε33+ c33ε11+2e15e33)] +p3[(c13+ c44)(d11q33+d33q15−e15µ33−e33µ11) − (q31+q15)(c44d33+ c33d11+ q15e33+e15q33)+(e31+e15)(c44µ33+ c33µ11+2q15q33)] c1 =β1[c44(ε11µ33+ε33µ11−2d11d33)+c33(ε11µ11−d211)+ε33q215+µ33e215 −2d11(e15q33+q15e33)+2q15q33ε11+2µ11e15e33] +β3[(c13+ c44)(d 2 11−ε11µ11)− (e31+e15)(µ11e15−d11q15) − (q31+q15)(ε11q15−d11e15)]+γ3[(c13+ c44)(q15ε11−e15d11) +(e31+e15)(d11c44+q15e15)− (q31+ q15)(c44ε11+e215)] +p3[(c13+ c44)(e15µ11−q15d11) +(q31+q15)(d11c44+q15e15)− (e31+e15)(c44µ11+q215)] d1 =−β1[c44(ε11µ11−d211)+µ11e215+ε11q215−2e15q15d11] a2 = c44[β3(ε33µ33−d233)+γ3(d33e33+q33ε33)+p3(d33q33−e33µ33)] b2 = β1[(c13+ c44)(ε33µ33−d233)− (e31+e15)(d33q33−µ33e33) − (q31+q15)(d33e33−ε33q33)]−β3[c11(ε33µ33+d233) + c44(µ11ε33+µ33ε11)−2(q31+q15)(e31+e15)d33+(q31+q15)2ε33+(e31+e15)2µ33] −γ3[c11(d33e33−q33ε33)+ c44(d11e33+d33e15−q15ε33− q33ε11) − (c13+ c44)d33(e31+e15)−q33(e31+e15)2+ε33(q31+ q15)(c13+ c44) +e33(q31+q15)(e31+e15)]−p3[c11(d33q33−e33µ33) + c44(d11q33+d33q15−e15µ33−e33µ11)− (c13+ c44)d33(q31+ q15) −e33(q31+q15)2+µ33(e31+e15)(c13+ c44)+q33(q31+ q15)(e31+e15)] 754 B. Rogowski c2 =β1[−(c13+ c44)(ε11µ33+ε33µ11)+(e31+e15)(d11q33+d33q15) +(q31+q15)(d11e33+d33e15)− (q31+q15)(q15ε33+ q33ε11) − (e31+e15)(e15µ33+e33µ11)+2(c13+ c44)d11d33]+β3[c44(ε11µ11+d211) + c11(µ11ε33+µ33ε11)+µ11(e31+e15) 2+ε11(q31+ q15) 2−2(e31+e15)(q31+ q15)d11] −γ3[c44(q15ε11−e15d11)+(e31+e15)((c13+ c44)d11+(e31+e15)q15) − (q31+q15)((c13 +c44)ε11+(e31+e15)e15)− c11(d11e33+e15d33−ε11q33−ε33q15)] −p3[c44(e15µ11−q15d11)+(q31+ q15)((c13+ c44)d11+(q31+ q15)e15) − (e31+e15)((c13+ c44)µ11+(q31+ q15)q15)− c11(d11q33+ q15d33−µ11e33−µ33e15)] d2 =β1[(c13+ c44)ε11µ11− (e31+e15)d11q15− (q31+ q15)d11e15+(q31+q15)q15ε11 +(e31+e15)µ11e15− (c13+ c44)d211]−β3[c11(ε11µ11−d211)]−γ3[c11(e15d11−q15ε11)] −p3[c11(q15d11−e15µ11)] A3. The parameters a3i and a4i in Eq. (2.8) are defined by the parameter a1i as follows a3i = { {β1[(e31+e15)(q33λ2i −q15)− (c13+ c44)(d11−d33λ2i)] +β3[(e31+e15)(q31+q15)λi+(c44λ 2 i − c11)(d11−d33λ2i)] +p3[λi(c13+ c44)(q31+q15)+(c44λ 2 i − c11)(q33λ2i − q15)]}a1iλi +β1[(c33λ 2 i − c44)(d11−d33λ2i)− (q33λ2i − q15)(e33λ2i −e15)] +β3λi[(c13+ c44)(d11−d33λ2i)− (q31+q15)(e33λ2i −e15)] +p3λi[(c13+ c44)(q33λ 2 i −q15)− (q31+q15)(c33λ2i − c44)] } · {p3λi[(e31+e15)(q33λ2i −q15)− (q31+q15)(e33λ2i −e15)] +β1[(e33λ 2 i −e15)(d11−d33λ2i)− (q33λ2i −q15)(ε11−ε33λ2i)] +β3λi[(e31+e15)(d11−d33λ2i)− (q31+ q15)(ε11−ε33λ2i)]}−1 a4i =− { {β1[(e31+e15)(e33λ2i −e15)− (c13+ c44)(ε11−ε33λ2i)] +β3[(e31+e15) 2λi+(c44λ 2 i − c11)(ε11−ε33λ2i)] +p3[λi(c13+ c44)(e31+e15)+(c44λ 2 i − c11)(e33λ2i −e15)]}a1iλi +β1[(c33λ 2 i − c44)(ε11−ε33λ2i)− (e33λ2i −e15)2] +β3λi[(c13+ c44)(ε11−ε33λ2i)− (e31+e15)(e33λ2i −e15)] +p3λi[(c13+ c44)(e33λ 2 i −e15)− (e31+e15)(c33λ2i − c44)] } · {p3λi[(e31+e15)(q33λ2i −q15)− (q31+q15)(e33λ2i −e15)] +β1[(e33λ 2 i −e15)(d11−d33λ2i)− (q33λ2i −q15)(ε11−ε33λ2i)] +β3λi[(e31+e15)(d11−d33λ2i)− (q31+ q15)(ε11−ε33λ2i)]}−1 A4. The roots of characteristic equation (2.9) are presented by the formulae (eigenvalues of multifield materials) λ21 =− b 4a − 1 2 √ R5+R6− 1 2 √ 2R5−R6+ 1 4 R7√ R5+R6 λ22 =− b 4a − 1 2 √ R5+R6+ 1 2 √ 2R5−R6+ 1 4 R7√ R5+R6 Green’s function for a multifield material with a heat source 755 λ23 =− b 4a + 1 2 √ R5+R6− 1 2 √ 2R5−R6− 1 4 R7√ R5+R6 λ24 =− b 4a + 1 2 √ R5+R6+ 1 2 √ 2R5−R6− 1 4 R7√ R5+R6 where R1 =2c 3−9bcd+27ad2+27b2e−72ace R2 = c2−3bd+12ae R3 = √ R21−4R32 R4 = 3 √ 1 2 (R1+R3) R5 = b2 4a2 − 2c 3a R6 = R2 3aR4 + R4 3a R7 = b3 a3 − 4bc a2 + 8d a References 1. Chen W.Q., Lee K.Y., Ding H.J., 2004, General solution for transversely isotropic magneto- electro-thermo-elasticity and the potential theory method, International Journal of Engineering Science, 42, 1361-1379 2. HouP.F., LeungA.Y.T.,DingH.J., 2008,A point heat source on the surface of a semi-infinite transversely isotropic electro-magneto-thermo-elastic material, International Journal of Engine- ering Science, 46, 273-285 3. Lekhnitskii S., 1963,Theory of Elasticity in an Anisotropic Elastic Body, Holden-Day Inc., San Francisco 4. Morse P.M., Feshbach H., 1953,Methods of Theoretical Physics, McGrawHill, NewYork 5. Rogowski B., 2012, A concave indenter on a piezo-electro-magneto-elastic substrate or a layer elastically supported,The Journal of Strain Analysis for Engineering Design, 47, 6, 362-378 6. Rogowski B., 2013, Anti-plane crack emanating from the interface in a bounded smart PEMO- elastic structure, International Journal of. Applied Mechanics and Engineering, 18, 4, 1165-1199 7. Rogowski B., 2014, The analysis of mode I conducting crack under general applied loads in piezoelectromagnetoelastic layer, International Journal of Engineering Science, 75, 11-30 8. Rogowski B., 2015, The transient analysis of conducting crack in magneto-electro-elastic half- space under anti-plane mechanical and in-plane electric and magnetic impact, Archive of Applied Mechanics, 85, 29-50 9. Stroh A.H., 1958, Dislocations and cracks in anisotropic elasticity, Philosophical Magazine, 3, 625-646 Manuscript received May 12, 2015; accepted for print November 8, 2015