Apply Pressures

Create pressure loads on elements by applying a load, representing pressures, to a 1D or 2D element, or to the face/edge of a solid element.

For most solvers, the pressure load is considered as force/area, therefore the magnitude of the pressure is multiplied by the calculated area of the elements to which it is applied and resolved as concentrated force loads at the associated nodes.

Pressures are load config 4 and are displayed as a vector with the letter P at the tail end.

You can specify the pressure's footprint by selecting the elements it affects, as well as its direction, magnitude, and the size in which its visual indicators are drawn. You can also apply the pressure to the faces of solid elements, or to the edges of plate elements.

For plate elements, the pressure is applied along the positive element normal. The Normals tool should be used first to obtain the correct orientation. The nodes on face option is not necessary if applying the pressure to the face of a plate element. If applying the pressure to the edge of plate elements, the nodes on edge option is required to define which of the three or four edges of the plate element you wish to apply the pressure to. For solid elements, the nodes on face option is required to define which of the faces you wish to apply the pressure to.

注: In the Radioss, Abaqus, and LS-DYNA profiles, load entities are created immediately upon entering the tool. Use the エンティティエディター to modify any properties. In all other solver profiles, load entities aren't created until you make your selections then click Create.
  1. From the Analyze ribbon, Loads tool group, click the Pressures tool.
    図 1.


  2. Select the keyword to create from the Load Type menu.
    The available types depend on the current solver interface.
  3. If applicable, set the entity type to Elements or Sets.
  4. Select elements (1D, 2D, 3D) or sets to which pressures will be applied.
  5. Specify the magnitude and direction of the pressure.
    Constant Components
    Specify the direction and magnitude of the load by entering the X, Y, and Z values of the components.
    Constant Vector
    Specify the magnitude, then use the plane and vector tool to specify the vector along which the load should act.
    Curve Components
    Specify the X, Y, and Z components to define the direction and magnitude, for example, (2,2,2) will be twice the magnitude of (1,1,1). Next, select an existing curve. Last, specify a factor for the curve’s xscale to use the same curve for many different cases, but vary the scale of its intensity or time to match the needs of your current load.
    Curve Vector
    When working with loads that are time dependent, use this method to first specify a magnitude (yscale) for the curve. Next, select an existing curve, then use the plane and vector tool to specify a direction, if necessary. Last, specify a factor for the curve's xscale to use the same curve for many different cases, but vary the scale of its intensity or time to match the needs of your current moment.
    Equation
    Specify the loading equation. Use the plane and vector tool to specify a direction, then select the coordinate system to which the vector corresponds.
    Field Loads
    Interpolate and extrapolate loads from existing loads. You can then select the desired elements to which you wish to add loads, and any existing loads on which you wish to base additional forces.
    When you create, HyperMesh uses a Green's function with the given boundary loads in order to create the loads on all of the selected nodes. For smoothness, the gradient at the boundary points is enforced to be zero; this ensures that the extrapolated loads remain lower than the input loads. For this reason it is recommended to use representative boundary values as input to be able to capture the peaks reasonably.
    注: This version differs from linear interpolation both in the way that the load magnitudes are determined, and also in the fact that it can be applied to nodes outside the boundaries of the chosen existing loads.
    Linear Interpolation
    Interpolate loads from a saved file or existing loads.
    注: Only available for shell elements.
    Each row of the input file contains the x,y,z coordinates of the load followed by its three components. The data can be separated by a space or tab.
    You can then select the desired nodes to which you wish to add loads, and pick three or more existing loads that enclose those nodes. When you interpolate, a linear function is used to create additional loads on the selected nodes, with magnitudes based on the magnitudes of the loads that you had selected.
    図 2.


    In the search radius field, specify the search distance to find the loads which are within that distance from a centroid or node on which a load is being interpolated. The nearest three loads located within that distance are used to create the load at the centroid or node by linear interpolation. Linear interpolation uses a triangulation method, so if it finds fewer than three loads within that distance no interpolation takes place. While reading the initial loads from a file, if linear interpolation is not possible because the search radius is too small, the original loads are simply applied to the nearest centroid or node.
    Select fill gap to create a load at every selected element centroid or node irrespective of the size of the search radius.
  6. If working in a controller, click Create.

Equationの指定によって、集中荷重、モーメント、荷重、温度、流束などを、適用するエンティティの座標値によって変化する荷重量を定義できます。このような荷重の例としては、適用点からの距離によって変化する温度の適用や内部の流体の高さによって変わるコンテナの壁にかかる圧力などが考えられます。

関数はmagnitude= f(x,y,z)の形式で指定します。変数は、x、y、z（すべて小文字）のみが使用可能で、荷重の適用されるエンティティの座標値を表します。点荷重（集中荷重、モーメントまたは温度）の場合、ポイントの座標値が使用されます。要素荷重（圧力または流束）の場合は、要素中心の座標地が使用されます。円筒または球座標系が使用される事象の場合、x、y、zが使用され、それぞれに対応する方向を参照します。一般的な数学演算子と関数が使用可能ですが、外部データが必要となる関数は適用できません。
注: 式の書式にエラーがある場合、警告のメッセージは表示されませんが、荷重は、荷重量ゼロで作成されます。
図 3. 平面と集中荷重を適用するための線形関数 magnitude = 20 – (5*x+2*y)：. X-Y平面に平行で、原点が中心である20 x 20の平らな平面。


図 4. 平面と多項式関数 Magnitude = x^2-2y^2+x*y+x+y. X-Y平面に平行で、原点が中心である20 x 20の平らな平面。


図 5. 曲面サーフェスへの圧力荷重 多項式関数 Magnitude = -((x^2+2*y^2+z)/1000). 圧力荷重は、円筒座標系（要素の上部エッジ付近に表示）に基づいて適用。