FEM: revert 5f8b459 and use a better fix fir frd reading of NaN floats

src/Mod/Fem/feminout/importCcxFrdResults.py

@@ -111,8 +111,7 @@ def importFrd(filename, analysis=None, result_name_prefix=None):
             error_message = (
                 "We have nodes but no results in frd file, which means we only have a mesh in frd file. "
                 "Usually this happens for analysis type 'NOANALYSIS' or if CalculiX returned no results because "
-                "of nonpositive jacobian determinant in at least one element or if the time step in frd file = 0.0."
-                "If the later an error message should have been printed.\n"
+                "of nonpositive jacobian determinant in at least one element.\n"
             )
             FreeCAD.Console.PrintMessage(error_message)
             if analysis:
@@ -158,6 +157,8 @@ def readResult(frd_input):
     elements_seg3 = {}
     results = []
     mode_results = {}
+    mode_results['number'] = float('NaN')
+    mode_results['time'] = float('NaN')
     mode_disp = {}
     mode_stress = {}
     mode_stressv = {}
@@ -182,7 +183,6 @@ def readResult(frd_input):
     input_continues = False
     mode_eigen_changed = False
     mode_time_changed = False
-    zero_mode_time = False  # result will not be imported
 
     eigenmode = 0
     eigentemp = 0
@@ -401,10 +401,6 @@ def readResult(frd_input):
             # we found the new time step line
             # !!! be careful here, there is timetemp and timestep! TODO: use more differ names
             timetemp = float(line[13:25])
-            if timetemp == 0:
-                FreeCAD.Console.PrintError('Time step in frd file = 0.0, result will not be imported.\n')
-                # https://forum.freecadweb.org/viewtopic.php?f=18&t=32649&start=10#p274686
-                zero_mode_time = True
             if timetemp > timestep:
                 timestep = timetemp
                 mode_time_changed = True
@@ -565,7 +561,7 @@ def readResult(frd_input):
         if line[1:5] == "9999":
             end_of_frd_data_found = True
 
-        if (not zero_mode_time) and (mode_eigen_changed or mode_time_changed or end_of_frd_data_found) and end_of_section_found and not node_element_section:
+        if (mode_eigen_changed or mode_time_changed or end_of_frd_data_found) and end_of_section_found and not node_element_section:
 
             '''
             print('\n\n----Append mode_results to results')
@@ -581,6 +577,8 @@ def readResult(frd_input):
             # append mode_results to results and reset mode_result
             results.append(mode_results)
             mode_results = {}
+            mode_results['number'] = float('NaN')  # https://forum.freecadweb.org/viewtopic.php?f=18&t=32649&start=10#p274686
+            mode_results['time'] = float('NaN')
             end_of_section_found = False
 
         # on changed --> write changed values in mode_result --> will be the first to do on an empty mode_result

src/Mod/Fem/feminout/importToolsFem.py

@@ -442,12 +442,16 @@ def calculate_principal_stress(i):
     sigma = np.array([[i[0], i[3], i[5]],
                       [i[3], i[1], i[4]],
                       [i[5], i[4], i[2]]])  # https://forum.freecadweb.org/viewtopic.php?f=18&t=24637&start=10#p240408
-    # compute principal stresses
-    eigvals = list(np.linalg.eigvalsh(sigma))
-    eigvals.sort()
-    eigvals.reverse()
-    maxshear = (eigvals[0] - eigvals[2]) / 2.0
-    return (eigvals[0], eigvals[1], eigvals[2], maxshear)
+
+    try:  # it will fail if NaN is inside the array,
+        # compute principal stresses
+        eigvals = list(np.linalg.eigvalsh(sigma))
+        eigvals.sort()
+        eigvals.reverse()
+        maxshear = (eigvals[0] - eigvals[2]) / 2.0
+        return (eigvals[0], eigvals[1], eigvals[2], maxshear)
+    except:
+        return (float('NaN'), float('NaN'), float('NaN'), float('NaN'))
 
 
 def calculate_disp_abs(displacements):