private bool IsCutElement(XContinuumElement2D element)
{
var polygon = ConvexPolygon2D.CreateUnsafe(element.Nodes);
// Look at each segment
foreach (var crackSegment in Segments)
{
var segment = new LineSegment2D(crackSegment.Start, crackSegment.End);
CartesianPoint intersectionPoint;
foreach (var edge in polygon.Edges)
{
LineSegment2D.SegmentSegmentPosition position = segment.IntersectionWith(edge, out intersectionPoint);
if (position == LineSegment2D.SegmentSegmentPosition.Intersecting)
{
// TODO: Perhaps the element should not be flagged as a Heaviside element, if the segment passes
// through 1 node only. To detect this, check if the intersection point coincides with an element
// node. If it does store it and go to the next edge. If a second intersection point (that does
// not coincide with the stored one) is found then it is a Heaviside element.
return(true);
}
else if (position == LineSegment2D.SegmentSegmentPosition.Overlapping)
{
return(true);
}
}
}
// Look at the vertices
// (if a segment is entirely inside an element, it will not be caught by checking the segment itself)
bool previousVertexOnEdge = false;
LinkedListNode <CartesianPoint> currentNode = Vertices.First.Next;
LinkedListNode <CartesianPoint> lastNode = Vertices.Last;
while (currentNode != lastNode)
{
PolygonPointPosition position = polygon.FindRelativePositionOfPoint(currentNode.Value);
if (position == PolygonPointPosition.Inside)
{
return(true);
}
else if (position == PolygonPointPosition.OnEdge || position == PolygonPointPosition.OnVertex)
{
if (previousVertexOnEdge)
{
return(true);
}
else
{
previousVertexOnEdge = true;
}
}
else
{
previousVertexOnEdge = false;
}
currentNode = currentNode.Next;
}
return(false);
}
private ElementEnrichmentType CharacterizeElementEnrichment(XContinuumElement2D element)
{
var polygon = ConvexPolygon2D.CreateUnsafe(element.Nodes);
int tipIndex = Vertices.Count - 1;
// Check tip element
PolygonPointPosition tipPosition = polygon.FindRelativePositionOfPoint(Vertices[tipIndex]);
if (tipPosition == PolygonPointPosition.Inside || tipPosition == PolygonPointPosition.OnEdge ||
tipPosition == PolygonPointPosition.OnVertex)
{
PolygonPointPosition previousVertexPos = polygon.FindRelativePositionOfPoint(Vertices[tipIndex - 1]);
if (previousVertexPos == PolygonPointPosition.Inside)
{
// Problem with blending elements, if the tip element is also enriched with Heaviside. What happens
// after the crack tip? Based on the LSM, the signed distance of the blending element after the
// crack tip should have a positive and negative region, however that element is not split by the
// crack and thus should not have discontinuity in the displacement field.
var builder = new StringBuilder();
builder.Append("Crack tip ");
builder.Append(Vertices[Vertices.Count - 1].ToString());
builder.Append(" and kink point ");
builder.Append(Vertices[Vertices.Count - 2].ToString());
builder.Append(" inside the same element with nodes: ");
foreach (var node in element.Nodes)
{
builder.Append(node.ToString());
builder.Append(' ');
}
throw new ArgumentException(builder.ToString());
//return ElementEnrichmentType.Both;
}
else
{
return(ElementEnrichmentType.Tip);
}
}
// Look at the other vertices
// (if a segment is inside an element, it will not be caught by checking the segment itself)
bool previousVertexOnEdge = false;
for (int v = 0; v < tipIndex; ++v)
{
PolygonPointPosition position = polygon.FindRelativePositionOfPoint(Vertices[v]);
if (position == PolygonPointPosition.Inside)
{
return(ElementEnrichmentType.Heaviside);
}
else if (position == PolygonPointPosition.OnEdge || position == PolygonPointPosition.OnVertex)
{
if (previousVertexOnEdge)
{
return(ElementEnrichmentType.Heaviside);
}
else
{
previousVertexOnEdge = true;
}
}
else
{
previousVertexOnEdge = false;
}
}
// Look at each segment
foreach (var crackSegment in Segments)
{
var segment = new LineSegment2D(crackSegment.Start, crackSegment.End);
CartesianPoint intersectionPoint;
foreach (var edge in polygon.Edges)
{
LineSegment2D.SegmentSegmentPosition position = segment.IntersectionWith(edge, out intersectionPoint);
if (position == LineSegment2D.SegmentSegmentPosition.Intersecting)
{
// TODO: Perhaps the element should not be flagged as a Heaviside element, if the segment passes
// through 1 node only. To detect this, check if the intersection point coincides with an element
// node. If it does store it and go to the next edge. If a second intersection point (that does
// not coincide with the stored one) is found then it is a Heaviside element.
return(ElementEnrichmentType.Heaviside);
}
else if (position == LineSegment2D.SegmentSegmentPosition.Overlapping)
{
return(ElementEnrichmentType.Heaviside);
}
}
}
// Then it must be a standard element
return(ElementEnrichmentType.Standard);
}
