diff --git a/notebooks/2015-09-24-Ideal plastic Von Mises material.ipynb b/notebooks/2015-09-24-Ideal plastic Von Mises material.ipynb
index 9a60072..d34f7c9 100644
--- a/notebooks/2015-09-24-Ideal plastic Von Mises material.ipynb	
+++ b/notebooks/2015-09-24-Ideal plastic Von Mises material.ipynb	
@@ -13,7 +13,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 1,
    "metadata": {
     "collapsed": false
    },
@@ -34,11 +34,28 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 2,
    "metadata": {
     "collapsed": false
    },
-   "outputs": [],
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "6x6 Array{Float64,2}:\n",
+       " 2.69231e5  1.15385e5  1.15385e5  0.0        0.0        0.0      \n",
+       " 1.15385e5  2.69231e5  1.15385e5  0.0        0.0        0.0      \n",
+       " 1.15385e5  1.15385e5  2.69231e5  0.0        0.0        0.0      \n",
+       " 0.0        0.0        0.0        1.53846e5  0.0        0.0      \n",
+       " 0.0        0.0        0.0        0.0        1.53846e5  0.0      \n",
+       " 0.0        0.0        0.0        0.0        0.0        1.53846e5"
+      ]
+     },
+     "execution_count": 2,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
    "source": [
     "\n",
     "\n",
@@ -90,11 +107,22 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 3,
    "metadata": {
     "collapsed": false
    },
-   "outputs": [],
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "calculate_stress (generic function with 1 method)"
+      ]
+     },
+     "execution_count": 3,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
    "source": [
     "\n",
     "M = [1 0 0 0 0 0;\n",
@@ -231,10 +259,9 @@
     "\n",
     "        σ[:]  += result[1:6]\n",
     "    else\n",
-    "        dϵᵖ = zeros(Float64, (6, 1))\n",
     "        σ = σ_tria\n",
     "    end\n",
-    "    return (dϵᵖ, σ)\n",
+    "    return σ\n",
     "end"
    ]
   },
@@ -247,11 +274,22 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 8,
    "metadata": {
     "collapsed": false
    },
-   "outputs": [],
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "linspace(-0.0,-0.0006,10)"
+      ]
+     },
+     "execution_count": 8,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
    "source": [
     "steps = 10\n",
     "\n",
@@ -260,7 +298,8 @@
     "# Adding only strain in x-axis and counting for the poisson effect\n",
     "ϵ_tot[:, 1] = linspace(0, 0.002, steps)\n",
     "ϵ_tot[:, 2] = linspace(0, 0.002, steps).*-ν\n",
-    "ϵ_tot[:, 3] = linspace(0, 0.002, steps).*-ν"
+    "ϵ_tot[:, 3] = linspace(0, 0.002, steps).*-ν\n",
+    "#ϵ_tot[:, 2] = 1/3 * linspace(0, 0.002, steps)"
    ]
   },
   {
@@ -276,12 +315,64 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 9,
    "metadata": {
     "collapsed": false,
     "scrolled": false
    },
-   "outputs": [],
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "[44.44444444444445 -3.552713678800501e-15 -3.552713678800501e-15 0.0 0.0 0.0]\n",
+      "([-3.552713678800501e-15,-3.552713678800501e-15,44.44444444444445],\n",
+      "[0.0 0.0 1.0\n",
+      " 1.0 0.0 0.0\n",
+      " 0.0 1.0 0.0])\n",
+      "[88.8888888888889 -7.105427357601002e-15 -7.105427357601002e-15 0.0 0.0 0.0]\n",
+      "([-7.105427357601002e-15,-7.105427357601002e-15,88.8888888888889],\n",
+      "[0.0 0.0 1.0\n",
+      " 1.0 0.0 0.0\n",
+      " 0.0 1.0 0.0])\n",
+      "[133.33333333333334 0.0 0.0 0.0 0.0 0.0]\n",
+      "([0.0,0.0,133.33333333333334],\n",
+      "[0.0 0.0 1.0\n",
+      " 1.0 0.0 0.0\n",
+      " 0.0 1.0 0.0])\n",
+      "[177.7777777777778 -6.217248937900877e-15 -7.105427357601002e-15 0.0 0.0 0.0]\n",
+      "([-7.105427357601002e-15,-6.217248937900877e-15,177.7777777777778],\n",
+      "[0.0 0.0 1.0\n",
+      " 0.0 1.0 0.0\n",
+      " 1.0 0.0 0.0])\n",
+      "[207.40740740740782 7.407407407407826 7.407407407407835 0.0 0.0 0.0]\n",
+      "([7.407407407407826,7.407407407407835,207.40740740740782],\n",
+      "[0.0 0.0 1.0\n",
+      " 1.0 0.0 0.0\n",
+      " 0.0 1.0 0.0])\n",
+      "[222.22222222222263 22.22222222222264 22.222222222222648 0.0 0.0 0.0]\n",
+      "([22.22222222222264,22.222222222222648,222.22222222222263],\n",
+      "[0.0 0.0 1.0\n",
+      " 1.0 0.0 0.0\n",
+      " 0.0 1.0 0.0])\n",
+      "[237.03703703703744 37.037037037037436 37.037037037037436 0.0 0.0 0.0]\n",
+      "([37.037037037037436,37.037037037037436,237.03703703703744],\n",
+      "[0.0 0.0 1.0\n",
+      " 1.0 0.0 0.0\n",
+      " 0.0 1.0 0.0])\n",
+      "[251.85185185185227 51.85185185185227 51.851851851852274 0.0 0.0 0.0]\n",
+      "([51.85185185185227,51.851851851852274,251.85185185185227],\n",
+      "[0.0 0.0 1.0\n",
+      " 1.0 0.0 0.0\n",
+      " 0.0 1.0 0.0])\n",
+      "[266.6666666666671 66.6666666666671 66.66666666666711 0.0 0.0 0.0]\n",
+      "([66.6666666666671,66.66666666666711,266.6666666666671],\n",
+      "[0.0 0.0 1.0\n",
+      " 1.0 0.0 0.0\n",
+      " 0.0 1.0 0.0])\n"
+     ]
+    }
+   ],
    "source": [
     "ϵ_last = zeros(Float64, (6))\n",
     "ϵᵖ = zeros(Float64, (6))\n",
@@ -290,20 +381,36 @@
     "σy =  200.0\n",
     "ss = zeros(Float64, steps)\n",
     "ee = zeros(Float64, steps)\n",
-    "for i=1:steps\n",
+    "for i=2:steps\n",
     "    dϵ = (reshape(ϵ_tot[i, :, :], (6, 1)) - ϵ_last) / Δt \n",
-    "    dϵᵖ, σ = calculate_stress(dϵ, Δt, σ, C, σy)\n",
+    "    σ = calculate_stress(dϵ, Δt, σ, C, σy)\n",
     "    ϵ_last += dϵ * Δt\n",
     "    ss[i] = σ[1]\n",
     "    ee[i] = ϵ_last[1]\n",
+    "    sdt = [σ[1]    0   0;\n",
+    "           0    σ[2]   0;\n",
+    "           0       0 σ[3]]\n",
+    "    princip = eig(sdt)\n",
+    "    println(σ')\n",
+    "    println(princip)\n",
+    "    \n",
     "end\n",
-    "PyPlot.plot(ee, ss)\n",
-    "PyPlot.title(\"Stress-Strain curve\")\n",
-    "PyPlot.xlabel(\"Strain\")\n",
-    "PyPlot.ylabel(\"Stress\")\n",
-    "PyPlot.ylim([0, 250])"
+    "#PyPlot.plot(ee, ss)\n",
+    "#PyPlot.title(\"Stress-Strain curve\")\n",
+    "#PyPlot.xlabel(\"Strain\")\n",
+    "#PyPlot.ylabel(\"Stress\")\n",
+    "#PyPlot.ylim([0, 250])"
    ]
   },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {
+    "collapsed": true
+   },
+   "outputs": [],
+   "source": []
+  },
   {
    "cell_type": "code",
    "execution_count": null,