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CreeSo 0.5.1

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The mathematical model for the simulation

The centrepiece of our models is the Orowan equation:
$$d\varepsilon/dt=\frac{b \cdot \rho_m \cdot v_{eff}}{M}$$
ε   creep strain (elongation)
t   time
b   Burgers vektor
M   Taylor factor
ρm   mobile dislocation density
veff   effective velocity

You can see the Orowan equation in the set of differential equations below.

While Burgers vektor and Taylor factor are constants, mobile dislocation density and effective velocity are strongly influenced by the microstructure of the material. Most of the equations below therefore focus on the prediction of microstructural evolution.




Show / hide the equations / code of the model

Code / Equations


$$\sigma_i=\alpha \cdot M \cdot G \cdot b \cdot \left(\rho_m+c_s \cdot \rho_s\right)^\left(\frac{1}{2}\right)$$ sigma_i=alpha*M*G*b*(rho_m+c_s*rho_s)^(1/2)
$$h_b=\frac{\frac{1}{\rho_b+\rho_s}}{R_{sgb}}$$ h_b=1/(rho_b+rho_s)/R_sgb
$$P_{eff}=\frac{4}{3} \cdot G \cdot b^2 \cdot \rho_b \cdot \left(1-\frac{\pi}{2} \cdot \left(r_{prec,sgb}^2 \cdot N_{prec,sgb}\right) \cdot R_{sgb}\right)$$ P_eff=4/3*G*b^2*rho_b*(1-pi/2*(r_prec_sgb^2*N_prec_sgb)*R_sgb)
$$M_{sgb}=\frac{2 \cdot \pi \cdot \eta_v \cdot D_s \cdot \omega}{b \cdot k_B \cdot T \cdot \theta_{EBSD}}+\frac{2 \cdot \pi \cdot b \cdot D_{vp} \cdot \omega \cdot \theta_{EBSD}}{h_b^2 \cdot k_B \cdot T}$$ M_sgb=2*pi*eta_v*D_s*omega/(b*k_B*T*Winkel_EBSD)+2*pi*b*D_vp*omega*Winkel_EBSD/(h_b^2*k_B*T)
$$v_{g,T1}=exp\left(\frac{-Q}{k_B \cdot T}\right)$$ v_g_Term1=exp(-Q/(k_B*T))
$$v_{g,T2}=exp\left(\frac{-\sigma_i \cdot V_r}{k_B \cdot T}\right)$$ v_g_Term2=exp(-sigma_i*V_r/(k_B*T))
$$v_{g,T3}=sinh\left(\frac{\sigma_{app} \cdot V_r}{k_B \cdot T}\right)$$ v_g_Term3=sinh(sigma_app*V_r/(k_B*T))
$$v_g=a_1 \cdot v_{g,T1} \cdot v_{g,T2} \cdot 2 \cdot v_{g,T3}$$ v_g=a_1*v_g_Term1*v_g_Term2*2*v_g_Term3
$$\rho_t=\rho_m+\rho_s+\rho_b$$ rho_t=rho_m+rho_s+rho_b
$$L_{\alpha}=\frac{\left(1+\nu\right) \cdot G \cdot b \cdot \omega}{6 \cdot \pi \cdot \left(1-\nu\right) \cdot k_B \cdot T}$$ L_alpha=(1+nue)*G*b*omega/(6*pi*(1-nue)*k_B*T)
$$L_p=2^\left(\frac{1}{2}\right) \cdot a_g \cdot exp\left(\frac{\delta_W}{2 \cdot k_B \cdot T}\right)$$ L_p=2^(1/2)*a_g*exp(delta_W/(2*k_B*T))
$$v_{c,T1}=exp\left(\frac{-\sigma_i \cdot \omega}{k_B \cdot T}\right)$$ v_c_Term1=exp(-sigma_i*omega/(k_B*T))
$$v_{c,T2}=2 \cdot sinh\left(\frac{\sigma_{app} \cdot \omega}{k_B \cdot T}\right)$$ v_c_Term2=2*sinh(sigma_app*omega/(k_B*T))
$$v_{c,T3}=2 \cdot \pi \cdot \eta_v \cdot D_s$$ v_c_Term3=2*pi*eta_v*D_s
$$v_{c,T4}=L_{\alpha} \cdot \rho_t^\left(\frac{1}{2}\right)$$ v_c_Term4=L_alpha*rho_t^(1/2)
$$v_{c,T5}=b \cdot \left(1-\eta_v \cdot log\left(v_{c,T4}\right)\right)$$ v_c_Term5=b*(1-eta_v*log(v_c_Term4))
$$v_{cl}=\frac{v_{c,T3}}{v_{c,T5}} \cdot v_{c,T1} \cdot v_{c,T2}$$ v_cl=v_c_Term3/v_c_Term5*v_c_Term1*v_c_Term2
$$v_{cp}=\frac{2 \cdot \pi \cdot b \cdot D_{vp}}{L_p^2} \cdot v_{c,T1} \cdot v_{c,T2}$$ v_cp=2*pi*b*D_vp/L_p^2*v_c_Term1*v_c_Term2
$$v_c=v_{cl}+v_{cp}$$ v_c=v_cl+v_cp
$$v_{eff}=\frac{1}{\frac{1}{v_g}+\frac{\frac{\pi}{2} \cdot N_{prec,gi} \cdot r_{prec,gi}^3}{v_c}}$$ v_eff=1/(1/v_g+pi/2*N_prec_gi*r_prec_gi^3/v_c)
Orowan equation $$\dot{\varepsilon}=\frac{b}{M} \cdot v_{eff} \cdot \rho_m$$ eps_punkt=b/M*v_eff*rho_m
$$\rho_{m,T1}=\rho_m^\left(\frac{3}{2}\right)$$ rho_m_Term1=rho_m^(3/2)
$$\rho_{m,T2}=\frac{\beta \cdot \rho_s \cdot R_{sgb}}{h_b^2}$$ rho_m_Term2=beta*rho_s*R_sgb/h_b^2
$$\rho_{m,T3}=\frac{-\rho_m}{2 \cdot R_{sgb}}$$ rho_m_Term3=-rho_m/(2*R_sgb)
$$\rho_{m,T4}=\frac{-8 \cdot \rho_m^\left(\frac{3}{2}\right) \cdot v_c}{v_{eff}}$$ rho_m_Term4=-8*rho_m^(3/2)*v_c/v_eff
$$\rho_{m,T5}=-d_{anh} \cdot \left(\rho_m+\rho_s\right) \cdot \rho_m$$ rho_m_Term5=-d_anh*(rho_m+rho_s)*rho_m
$$\rho_{m,Tges}=\rho_{m,T1}+\rho_{m,T2}+\rho_{m,T3}+\rho_{m,T4}+\rho_{m,T5}$$ rho_m_Term_ges=rho_m_Term1+rho_m_Term2+rho_m_Term3+rho_m_Term4+rho_m_Term5
$$\dot{\rho_m}=v_{eff} \cdot \rho_{m,Tges}$$ rho_m_punkt=v_eff*rho_m_Term_ges
$$\rho_{s,T1}=\frac{\rho_m}{2 \cdot R_{sgb}}$$ rho_s_Term1=rho_m/(2*R_sgb)
$$\rho_{s,T2}=\frac{-8 \cdot v_c \cdot \rho_s}{v_{eff} \cdot h_b}$$ rho_s_Term2=-8*v_c*rho_s/(v_eff*h_b)
$$\rho_{s,T3}=-d_{anh} \cdot \rho_s \cdot \rho_m$$ rho_s_Term3=-d_anh*rho_s*rho_m
$$\rho_{s,Tges}=\rho_{s,T1}+\rho_{s,T2}+\rho_{s,T3}$$ rho_s_Term_ges=rho_s_Term1+rho_s_Term2+rho_s_Term3
$$\dot{\rho_s}=v_{eff} \cdot \rho_{s,Tges}$$ rho_s_punkt=v_eff*rho_s_Term_ges
$$\dot{\rho_b}=\frac{8 \cdot \left(1-2 \cdot \zeta\right) \cdot \rho_s \cdot v_c}{h_b}-\frac{M_{sgb} \cdot P_{eff} \cdot \rho_b}{R_{sgb}}$$ rho_b_punkt=8*(1-2*zeta)*rho_s*v_c/h_b-M_sgb*P_eff*rho_b/R_sgb
$$R_{sgb,T1}=M_{sgb} \cdot P_{eff}$$ R_sgb_Term1=M_sgb*P_eff
$$R_{sgb,T2}=\frac{G \cdot \eta_v \cdot K_c^2 \cdot \left(\left(\rho_m+\rho_s\right)^\left(\frac{1}{2}\right)-\frac{K_c}{2 \cdot R_{sgb}}\right) \cdot D_s \cdot \omega}{2 \cdot k_B \cdot T}$$ R_sgb_Term2=G*eta_v*K_c^2*((rho_m+rho_s)^(1/2)-K_c/(2*R_sgb))*D_s*omega/(2*k_B*T)
$$\dot{R_{sgb}}=R_{sgb,T1}+R_{sgb,T2}$$ R_sgb_punkt=R_sgb_Term1+R_sgb_Term2



Show / hide all variables

Variables

PosNameSymbolDescrInitDeriv
1i\(i\)Loop counter0
2t\(t\)time in seconds0
3dt\(dt\)time increment100
4max_loop_count\({max\_loop\_count}\)maximal number of iterations3.6e+06
5T\(T\)Temperature in Kelvin923
6sigma_app\(\sigma_{app}\)Applied stress in megapascal
7eps\(\varepsilon\)Creep strain0eps_punkt
8a_g\(a_g\)Gitterkonstante Fe-bcc. [m]2.866e-10
9alpha\(\alpha\)[-]0.02
10b\(b\)Burgers - Vektor [m]2.48e-10
11c_s\(c_s\)[-]0.3
12d_anh\(d_{anh}\)edge dislocations [m]-999
13D_s\(D_s\)in 9Cr steel at 650°C [m²/s]2e-19
14D_vp\(D_{vp}\)in P91, 650°C [m²/s]4.75e-19
15eta_v\(\eta_v\)ferritic steel0.0002
16G\(G\)650°C, [Pa]6.2e+10
17k_B\(k_B\)[J/K]1.38065e-23
18K_c\(K_c\)for P912.1
19M\(M\)Taylor Faktor3
20omega\(\omega\)Volume per Atom [m³]-999
21Q\(Q\)Activation energy for dislocation glide4.01e-19
22Winkel_EBSD\(\theta_{EBSD}\)[rad]0.0524
23V_r\(V_r\)Activation volume for dislocation glide-999
24nue\(\nu\)0.317
25delta_W\(\delta_W\)[J]1.26e-19
26zeta\(\zeta\)[-]0.034
27a_1\(a_1\)3.9
28A\(A\)0.035
29beta\(\beta\)0.0375
30rho_m\(\rho_m\)[m/m3]4.5e+14rho_m_punkt
31rho_s\(\rho_s\)[m/m3]4.5e+11rho_s_punkt
32rho_b\(\rho_b\)[m/m3]5.9e+14rho_b_punkt
33R_sgb\(R_{sgb}\)4e-07R_sgb_punkt
34r_prec_gi\(r_{prec,gi}\)1.6e-08r_prec_gi_punkt
35N_prec_gi\(N_{prec,gi}\)2.36e+20N_prec_gi_punkt
36k_prec_gi\(k_{prec,gi}\)1e-31
37r_prec_sgb\(r_{prec,sgb}\)7e-08r_prec_sgb_punkt
38N_prec_sgb\(N_{prec,sgb}\)1.17e+19N_prec_sgb_punkt
39k_prec_sgb\(k_{prec,sgb}\)1e-28
40rho_b_punkt\(\dot{\rho_b}\)0
41rho_m_punkt\(\dot{\rho_m}\)0
42rho_s_punkt\(\dot{\rho_s}\)0
43R_sgb_punkt\(\dot{R_{sgb}}\)0
44r_prec_gi_punkt\(\dot{r_{prec,gi}}\)0
45r_prec_sgb_punkt\(\dot{r_{prec,sgb}}\)0
46N_prec_gi_punkt\(\dot{N_{prec,gi}}\)0
47N_prec_sgb_punkt\(\dot{N_{prec,sgb}}\)0
48eps_punkt\(\dot{\varepsilon}\)0
49pi\(\pi\)3.14159
50sigma_i\(\sigma_i\)Parameter for Microstructure0
51h_b\(h_b\)Parameter for Microstructure0
52P_eff\(P_{eff}\)Parameter for Microstructure0
53M_sgb\(M_{sgb}\)Parameter for Microstructure0



Show / hide the code for additional initialisation

Start code

Equations / code evaluated at start


$$d_{anh}=5 \cdot b$$ d_anh=5*b
$$\omega=\frac{a_g^3}{2}$$ omega=a_g^3/2
$$V_r=35 \cdot \omega$$ V_r=35*omega