FIELD OF INVENTION
The invention relates to a device to assist finite element analysis of structures consisting of standard beam elements using commercially available finite element packages which are used for Finite Element (FE) Analysis of structures with standard structural beams (as beams, colums or stifFeners) using commercial FE packages such as ANSYS.
BACKGROUND
Structural anaylsts quite often resort to usage of Beam elements in their Finite Element models. Beam element is very simple as far as its generation is concerned. But correct and consistent input regarding the cross sectional properties (like area, moments of inertia, offset distances, extreme fiber distances) is quite essential. The format in which these properties are input depends upon the software. In case of ANSYS these properties are input in a set of four lines. When beams in a given model are oriented in space then it becomes difficult or rather tedious to make correct and consistent input. It is here that this device would be of help to the analyst.
PRIOR ART
No such device has been reported in any of publications nor it is known in the art.
OBJECTS OF INVENTION
An object of the invention is to orient a given beam element.
Another object of the gadget is to help in identifying the type of orientation of the said element. Once the orientation is identified, subsequent finite element analysis becomes easy, correct and consistent.
Further objects and advantages of this invention will be more apparent from the ensuing description.
At the outset of the description which follows, it is to be understood that the ensuing description only illustrates a particular form of this invention. However, such a particular form is only an exemplary embodiment and without intending to be understood as an exemplary and teaching of the invention and not intended to be taken restrictively.
STATEMENT OF INVENTION
According to this invention, there is provided a device to assist finite element analysis of structures consisting of standard beam elements, comprising:a pair of metallic rods (2) having at one end a swiveling joint (A) with a base (1), the other ends of the said rods (2) connected through a swiveling joint (B) with another pair of metallic rods (3), the said rods (3) provided with another swiveling joint (C) in which a metallic pin (12) is mounted, disc-1 (4), disc-2 (5) and disc-3 (6) rotatably mounted on the said pin (12), and an X-Z plane (7) fixed to disc-1.
PESCRIPTION OF ACCOMPANYING DRAWINGS LEFT WITH PROVISIONAL SPECIFICATION;
Fig 1 shows the front, side and top views of the device. Fig 2(a) shows the schematic view of the device Fig 2(b) shows the disc -1 Fig 2(c) shows the disc -2 Fig 2(d) shows the disc -3
Fig 2(e) shows cross section of a beam element
Fig 3 (a) shows defining of beam element orientation using default option when local X
axis is parallel to global X axis Fig 3(b) shows defining of beam element orientation using default option when local Y
axis is parallel of global Y axis Fig 3(c) shows defining of beam element orientation using default option when local Z
axis is parallel to global Z axis Fig 4(a) and 4(b) shows defining of beam element orientation using third node option,
DETAILED DESCRIPTION OF INVENTION WITH REFERENCE TO DRAWINGS
This invention comprises a base (1) made of a metallic material on which is mounted a pair of metallic rods (2) having a swiveling joint (A) with the base (1), comprising a metallic bush (9) and a metallic stud (12). Another swivelling joint (B) is provided at the other end of the said rods comprising a metallic bush (11) and a metallic stud, with which another pair of metallic rods (3) is connected. These rods (3) have another swivelling joint (C) at the other end to which is mounted a Pin (12). Three discs disc 1 (4), disc 2 (5), disc 3 (6), made of acrylic sheet are rotatably mounted on the metallic pin (12) with a metallic bush (10). AnX-Z plane (7) for third node made of acrylic sheet is fixed to disc -1. The base is provided with 4 shoes (5) made preferably of hard rubber. The metallic parts are made of aluminium, mild steel or brass.
The base is marked with two axes X and Z. These two axes together with rod (2) define the global XYZ axes. Rod (3) is aligned along the direction of beam in space. This becomes the local X axis of the beam. Three disks (4, 5 and 6) which are in a plane perpendicular to 3 represent local YZ plane. The first disk, (4) (Fig. 2b) forms a background disk which has a plane
(7) attached to it. Disk (5) has two axes marked on it (XP and YP) as shown in Fig. 2(c). These are the two axes referred in the hand book (ISI Hand Book for Structural Engineers 1. Structural Steel Sections (Revised) Indian
Standards Institution SP: 6(1)- 1964) to describe various section properties. Above this disk the section replica is mounted in a manner similar to the one existing in the given case. Disk (6) which is mounted above the replica of section has two axes marked on it YL and ZL as shown in Fig. 2(d). These are local Y and Z axes. Correct orientation of these axes is the important aspect of any analysis using beam elements. Orientation of cross section in space is communicated to the conventional FE software by two ways. The first way is by means of default options and the other way is explicit mention through specification of a third node.
The beam element oritentation is generally defined using one of the two options namely 'Default Option and 'Third Node Option'.
Default option is generally used when local- X axis of the beam is parallel to one of the global axes (X, Y or Z). In this situation. ANSYS one of the commercially available finite element analysis package has the following rule:
Local Y axis is parallel to global XY plane. If both local axes ( Y and Z) are parallel to Global XY plane (When local X axis is parallel to global Z axis) the local Y axis is parallel to global Y axis also.
This is demonstrated by example shown in Fig 3 a to 3 c. Fig 3 a, b and c show the cases where local X axis of beam is parallel to one of the global axes. Depending upon the situation the orientation number ( 1 or 2) is to be identified.
Defining a beam orientation using third node is a well known concept in FE analysis using beam element. Beam element is represented by line and local axis get automatically defined. The local YZ plane, i.e. the plane normal to local X axis also gets defined. The exact orientation of either local Y or local Z axis in this local YZ plane is required to be defined. This is done by defining a third node. These three nodes, two nodes which define the beam and the third node are used to define either local XZ or local XY plane. In ANSYS, it defines local XZ plane. Once XZ plane is defined the orientation gets totally defined.
Selecting a third node is always left for the analyst to choose and in general an available node is chosen. Whether the selected third node lies along Xp and Yp defines the orientation of the beam as either 1 or 2. This is shown in Fig 4a and 4b.
The procedure for using this device is as follows: Rod (3) is oriented in space in a manner similar to the orientation of beam in question. First disc (4) is mounted on rod (3). Disc (5) is mounted next followed by the replica of the beam cross section. The axes Xp and Yp marked on disc (4) are aligned w.r.t. cross section in a manner similar to that given in the data hand book to calculate the sectional properties. The two discs and the section replica are clamped in this position by means of a nut. Third disc (6) is now placed and oriented in such a manner that it is consistent with either the third node or the default option. If Xp and XL are parallel to each other the orientation is declared as type 1 otherwise it is declared as type 2.

WE CLAIM:
1 . A device to assist finite element analysis of structures consisting of standard beam elements, comprising:
a pair of metallic rods (2) having at one end a swiveling joint (A) with a base (1), the other ends of the said rods (2) connected through a swiveling joint (B) with another pair of metallic rods (3),
the said rods (3) provided with another swiveling joint (C) in which a metallic pin (12) is mounted,
disc-1 (4), disc-2 (5) and disc-3 (6) rotatably mounted on the said pin (12), and an X-Z plane (7) fixed to disc-1 .
2. A device as claimed in claim 1, wherein each said swiveling joint (A, B, C) comprises
a metallic bush (9), a metallic stud (12) and at least two nuts.
3. A device as claimed in claim 1, wherein the metallic parts comprise material selected
from aluminium, brass or mild steel.
4. A device as claimed in claim 1, wherein the said discs (4, 5, 6) and said X-Z plane (7)
are made of acrylic sheet.
5. A device as claimed in claim 1, wherein the Disc-2 (5) has two axes XP and marked on it.
6. A device as claimed in claim 1, wherein the Disc-3 (6) has two axes YL andZL, marked on it, YL and ZL being local Y and Z axes.
7. A device as claimed in claim 1, wherein the base (1) is marked with X and Z axes.
8. A device as claimed in claim 1, wherein the base is provided with shoes (5)
preferably made of hard rubber.
9. A device as claimed in claim 1, substantially as herein described and illustrated in Fig
1 to 4 of accompanying drawings .