Electricidad

Application of Joints and Springs in ANSYS

Introduction
This tutorial was created using ANSYS 5.7.1. This tutorial will introduce:
* the use of multiple elements in ANSYS
* elements COMBIN7 (Joints) and COMBIN14 (Springs)
* obtaining/storing scalar information and store them as parameters.
A 1000N vertical load will be applied to a catapult as shown in the figure below. Thecatapult is built from steel tubing with an outer diameter of 40 mm, a wall thickness of 10, and a modulus of elasticity of 200GPa. The springs have a stiffness of 5 N/mm.

Preprocessing: Defining the Problem
1. Open preprocessor menu
/PREP7
2. Give example a Title
Utility Menu > File > Change Title ...
/title,Catapult
3. Define Element Types
For this problem, 3 types ofelements are used: PIPE16, COMBIN7 (Revolute Joint), COMBIN14 (Spring-Damper) . It is therefore required that the types of elements are defined prior to creating the elements. This element has 6 degrees of freedom (translation along the X, Y and Z axis, and rotation about the X,Y and Z axis).
a. Define PIPE16
With 6 degrees of freedom, the PIPE16 element can be used to create the 3D structure.* Preprocessor > Element Type > Add/Edit/Delete... > click 'Add'
* Select 'Pipe', 'Elast straight 16'
* Click on 'Apply' You should see 'Type 1 PIPE16' in the 'Element Types' window.
b. Define COMBIN7
COMBIN7 (Revolute Joint) will allow the catapult to rotate about nodes 1 and 2.
* Select 'Combination', 'Revolute Joint 7'
* Click'Apply'.
c. Define COMBIN14
Now we will define the spring elements.
* Select 'Combination', 'Spring damper 14'
* Click on 'OK'
In the 'Element Types' window, there should now be three types of elements defined.
4. Define Real Constants
Real Constants must be defined for each of the 3 element types.
d. PIPE16
* Preprocessor > Real Constants >Add/Edit/Delete... > click 'Add'
* Select Type 1 PIPE16 and click 'OK'
* Enter the following properties, then click 'OK'
OD = 40
TKWALL = 10
e. 'Set 1' will now appear in the dialog box
f. COMBIN7 (Joint)
Five of the degrees of freedom (UX, UY, UZ, ROTX, and ROTY) can be constrained with different levels of flexibility. These can be defined by the 3 realconstants: K1 (UX, UY), K2 (UZ) and K3 (ROTX, ROTY). For this example, we will use high values for K1 through K3 since we only expect the model to rotate about the Z axis.
* Click 'Add'
* Select 'Type 2 COMBIN7'. Click 'OK'.
* In the 'Real Constants for COMBIN7' window, enter the following geometric properties (then click 'OK'):
X-Y transnational stiffness K1: 1e9
Zdirectional stiffness K2: 1e9
Rotational stiffness K3: 1e9
* 'Set 2' will now appear in the dialog box.
Note: The constants that we define in this problem refer to the relationship between the coincident nodes. By having high values for the stiffness in the X-Y plane and along the Z axis, we are essentially constraining the two coincident nodes to each other.
g. COMBIN14 (Spring)* Click 'Add'
* Select 'Type 3 COMBIN14'. Click 'OK'.
* Enter the following geometric properties:
Spring constant K: 5
h. In the 'Element Types' window, there should now be three types of elements defined.
5. Define Element Material Properties
a. Preprocessor > Material Props > Material Models
b. In the 'Define Material Model Behavior'Window, ensure that Material Model Number 1 is selected
c. Select Structural > Linear > Elastic > Isotropic
d. In the window that appears, enter the give the properties of Steel then click 'OK'.
Young's modulus EX: 200000
Poisson's Ratio PRXY: 0.33
1. Define Nodes
Preprocessor > (-Modeling-) Create > Nodes > In Active CS...
N,#,x,y,z
We are going to define...