diff --git a/environment.yml b/environment.yml
index c882516ec2e31faf8e2dfbc4e54306d4c2776240..ef56fa273a6439233977e3bddaef4f5fd20e9e02 100644
--- a/environment.yml
+++ b/environment.yml
@@ -7,7 +7,7 @@ dependencies:
 - numpy==1.19.4
 - sympy==1.7.1
 - scipy==1.5.3
-- k3d==2.9.3
+- k3d==2.9.7
 - ipywidgets==7.6.3
 - ipympl==0.7.0
 - ipyregulartable==0.2.0
diff --git a/tour2_constant_bond/fragmentation.ipynb b/tour2_constant_bond/fragmentation.ipynb
index 5f0a3a3fc69a86be6e1b17fb1ac8283ac6bcedd6..b90929047ec0e938929e4973d9942993ced13a31 100644
--- a/tour2_constant_bond/fragmentation.ipynb
+++ b/tour2_constant_bond/fragmentation.ipynb
@@ -122,14 +122,14 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 1,
+   "execution_count": 2,
    "id": "labeled-regression",
    "metadata": {},
    "outputs": [
     {
      "data": {
       "application/vnd.jupyter.widget-view+json": {
-       "model_id": "57c3b9b7874c46e3874f6de2175af38a",
+       "model_id": "3a5b0eaf752140448e94538c89af305d",
        "version_major": 2,
        "version_minor": 0
       },
@@ -396,17 +396,17 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 2,
+   "execution_count": 72,
    "id": "regulation-bronze",
    "metadata": {},
    "outputs": [],
    "source": [
-    "E_m = 28000 # concrete stiffness [MPa]\n",
-    "E_f = 210000 # reinforcement stiffnes [MPa]\n",
+    "E_m = 25000 # 28000 # concrete stiffness [MPa]\n",
+    "E_f = 182000 # 210000 # reinforcement stiffnes [MPa]\n",
     "A_c = 100 * 100 # dimensions [mm]\n",
     "d = 16 # diameter [mm]\n",
-    "sig_mu = 3 # concrete tensile strength [MPa]\n",
-    "sig_fu = 500 # reinforcement strength [MPa]"
+    "sig_mu = 3 # 3 # concrete tensile strength [MPa]\n",
+    "sig_fu = 1380 # 500 # reinforcement strength [MPa]"
    ]
   },
   {
@@ -419,7 +419,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 3,
+   "execution_count": 78,
    "id": "stock-interval",
    "metadata": {},
    "outputs": [],
@@ -427,24 +427,24 @@
     "p = 3.14 * d # bond perimeter\n",
     "A_f = 3.14 * (d/2)**2 # reinforcement cross section\n",
     "A_m = A_c - A_f # concrete cross section\n",
-    "V_f = A_f / A_c # reinforcement ratio / fiber volume fraction\n",
+    "V_f = 0.01 # A_f / A_c # reinforcement ratio / fiber volume fraction\n",
     "E_c = E_m * (1 - V_f) + E_f * V_f # composite stiffness\n",
     "alpha_e = E_m * (1 - V_f) / (E_f * V_f) # homogenization coefficient"
    ]
   },
   {
    "cell_type": "code",
-   "execution_count": 4,
+   "execution_count": 79,
    "id": "junior-patrol",
    "metadata": {},
    "outputs": [
     {
      "data": {
       "text/plain": [
-       "31657.472"
+       "26570.0"
       ]
      },
-     "execution_count": 4,
+     "execution_count": 79,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -453,6 +453,27 @@
     "E_c"
    ]
   },
+  {
+   "cell_type": "code",
+   "execution_count": 80,
+   "id": "e77defe7-ce4a-42f2-9ac2-8cbdc5302d5c",
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "0.01"
+      ]
+     },
+     "execution_count": 80,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "V_f"
+   ]
+  },
   {
    "cell_type": "markdown",
    "id": "short-apparel",
@@ -463,19 +484,41 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 5,
+   "execution_count": 81,
    "id": "fundamental-bulletin",
    "metadata": {},
    "outputs": [],
    "source": [
     "eps_1, sig_1 = 0, 0\n",
-    "eps_2, sig_2 = sig_mu / E_m, sig_mu\n",
-    "eps_3, sig_3 = sig_mu / E_m * (1 + 0.6666 * alpha_e), sig_mu\n",
+    "eps_2 = sig_mu / E_m\n",
+    "sig_2 = eps_2 * E_c\n",
+    "eps_3, sig_3 = sig_mu / E_m * (1 + 0.6666 * alpha_e), sig_2\n",
     "sig_4 = sig_fu * V_f\n",
     "E_r = E_f * V_f # effective reinforcement stiffness related to the composite cross section \n",
     "eps_4 = eps_3 + (sig_4 - sig_3) / E_r"
    ]
   },
+  {
+   "cell_type": "code",
+   "execution_count": 82,
+   "id": "bb9b6f0f-ad91-4b18-a65f-b19873afd2b4",
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "(3.1884, 13.8)"
+      ]
+     },
+     "execution_count": 82,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "sig_2, sig_4"
+   ]
+  },
   {
    "cell_type": "markdown",
    "id": "configured-picnic",
@@ -486,14 +529,14 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 6,
+   "execution_count": 71,
    "id": "nuclear-firmware",
    "metadata": {},
    "outputs": [
     {
      "data": {
       "application/vnd.jupyter.widget-view+json": {
-       "model_id": "207eef47c0904fe48f812ba2efbdb2a7",
+       "model_id": "56d65678687048f985d17f154c01c1ca",
        "version_major": 2,
        "version_minor": 0
       },
diff --git a/tour5_damage_bond/5_1_Introspect_Damage_Evolution_Damage_initiation.ipynb b/tour5_damage_bond/5_1_Introspect_Damage_Evolution_Damage_initiation.ipynb
index e3eb88ad3a998920b692bd8ba5f928b37b74721b..cb32b7ee0efa0bd7c7b400b639e85c8ca62a2d86 100644
--- a/tour5_damage_bond/5_1_Introspect_Damage_Evolution_Damage_initiation.ipynb
+++ b/tour5_damage_bond/5_1_Introspect_Damage_Evolution_Damage_initiation.ipynb
@@ -1456,7 +1456,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.8.10"
+   "version": "3.8.8"
   },
   "toc": {
    "base_numbering": 1,
diff --git a/tour6_energy/6_2_Energy_released_in_pullout_constant_bond_and_rigid_matrix.ipynb b/tour6_energy/6_2_Energy_released_in_pullout_constant_bond_and_rigid_matrix.ipynb
index 76c75361baf52bf7312928675b857a51d35d8ddb..7fa64bf1047fbc37d6d3bbe8d12a316aed1737c6 100644
--- a/tour6_energy/6_2_Energy_released_in_pullout_constant_bond_and_rigid_matrix.ipynb
+++ b/tour6_energy/6_2_Energy_released_in_pullout_constant_bond_and_rigid_matrix.ipynb
@@ -1043,7 +1043,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.8.10"
+   "version": "3.8.8"
   }
  },
  "nbformat": 4,
diff --git a/tour6_energy/6_3_localized_energy_dissipation.ipynb b/tour6_energy/6_3_localized_energy_dissipation.ipynb
index 941e929f7063028703c3a9da71e85cfb056bd8d4..ad8b4c6ec31c45aceac531a99cf6be8a926b0f7f 100644
--- a/tour6_energy/6_3_localized_energy_dissipation.ipynb
+++ b/tour6_energy/6_3_localized_energy_dissipation.ipynb
@@ -605,7 +605,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.8.10"
+   "version": "3.8.8"
   }
  },
  "nbformat": 4,
diff --git a/tour7_cracking/7_1_bending3pt_2d.ipynb b/tour7_cracking/7_1_bending3pt_2d.ipynb
index bf00882a30ad42f3081c8986ae338f31fc5381e8..a725552d750e432c1a0c15be5ab8fe57e40af260 100644
--- a/tour7_cracking/7_1_bending3pt_2d.ipynb
+++ b/tour7_cracking/7_1_bending3pt_2d.ipynb
@@ -1102,7 +1102,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.8.10"
+   "version": "3.8.8"
   }
  },
  "nbformat": 4,