Dynamic Analysis of a Slider Crank with a Flexible Connecting Rod - OS-1210

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The slider crank model shown in the figure below consists of a rigid crank, a flexible connecting rod, and a rigid sliding block. The objective of this analysis is to determine the deformation and stress of a flexible connecting rod under the high speed motion of the system.

This exercise includes the creation of PRBODY (rigid body definition), PFBODY (flexible body definition), and JOINT in HyperMesh 8.0.

An existing finite element model will be used in this tutorial problem.

$image\slider_crank_model.gif$

Slider crank model

The following exercises are included:

· Setting up the problem in HyperMesh 8.0

- PRBODY

- PFBODY

- JOINTS

- MBSIM (simulation parameter)

- INVELB (initial velocity)

· Submitting the job

· Viewing the results in HyperView

Setting up the problem in HyperMesh

To define the OptiStruct user profile and retrieve the structural model:

Launch HyperMesh.
Select OptiStruct in the User Profile dialog and click OK.
Select the Files panel toolbar button $image\files_panel.gif$ .
Select the hm file subpanel using the radio buttons on the left-hand side of the panel.
Click retrieve… .

An Open file… browser window pops up.

Select the slider_crank.hm file, located in the HyperWorks installation directory under <install_directory>/tutorials/os/.
Click open.
Click return to go to the main menu.

To define the parts as PRBODY (Rigid Body definition) and PFBODY (Flexible Body definition):

From the Analysis page, select the bodies panel.
Select the create subpanel using the radio buttons on the left-hand side of the panel.

PRBODY for component, support, will be created.

Click name= and enter support.
Click type= and select PRBODY.
Click the comps button and select support.
Click create.

PRBODY for component, crank, will be created.

Click name= and enter crank.
Click type= and select PRBODY.
Click the comps button and select crank.
Click the nodes button and select the node (ID 25231) at the center of RBE2 spider between connecting rod and crank (see the following figure).

$image\prbody_crank.gif$

PRBODY for crank

Click create.

PRBODY for component, sliding block, will be created.

Click name= and enter block.
Click type= and select PRBODY.
Click the comps button and select block.
Click the nodes button and select the node (ID 25232) at the center of RBE2 spider between connecting rod and block (see figure).
Click create.

$image\prbody_sliding_crank.gif$

PRBODY for sliding block

This completes the definition of PRBODY; the next step is to define PFBODY for the connecting rod. The first step, then, is to create a PFBODY for the connecting rod.

Click name= and enter rod.
Click type= and select PFBODY.
Click the comps button and select rod.
Click the elems button and select two RBE2 elements that are inside a hole on the connecting rod.

$image\prbody_con_rod.gif$

PFBODY for connecting rod

Select Craig-Bampton as the CMS Method:, and the number of modes to be 10.

$image\craig_bampton.gif$

Click create.
Click return.

To create the component for the joints:

Click the Collectors toolbar button $image\collectors.gif$ .
Select the create subpanel using the radio buttons on the left-hand side of the panel.
Click the collector type switch and select components from the pop-up menu.
Click name= and enter joints.
Click the switch beside card image= and select no card image from the pop-up menu.
Click color and select any color.
Click create.

This creates the new component called joints.

Click return to get back to the main menu.

In this tutorial problem, three revolute joints, one fixed joint, and one translational joint are created to constrain the degrees of freedom.

Type of Joint	Removes translational dof	Removes rotational dof	Removes total number of dof
Revolute	3	2	5
Fixed	3	3	6
Translational	2	3	5

$image\model_joints.gif$

Joints in the model

To create the joints:

From the 1D page of the main menu, select the joints panel.

First, the fixed joint between ground and support will be created.

Click the joint type: selection switch and select fixed.
Select node ID 25313 as first terminal (see the following figure).
Select node ID 25543 as second terminal.

Note:

Nodes 25313 and 25543 are coincident. Coincident node picking in options panel in HM will help pick these coincident nodes if nodes need to be picked in the screen.

$image\nodes_fixed_j.gif$

Nodes for the definition of fixed joint

Click create.

Next, the revolute joint between support and crank will be created.

Click the joint type: selection switch and select revolute.
Select node ID 25472 as a first terminal (see the following figure).
Select node ID 15124 as a second terminal.
Select coordinates as first orientation and type x=0.0, y=0.0, z=1.0. The z-axis will be the axis of rotation of revolute joint.
Click create.

$image\support_crank.gif$

Joint between support and crank

A revolute joint between the crank and connecting rod will be created next.

Click the joint type: selection switch and select revolute.
Select node ID 25229 as a first terminal (see the following figure).
Select node ID 25231 as a second terminal.
Select the coordinates as the first orientation and type x=0.0, y=0.0, z=1.0. The z-axis will be the axis of rotation of revolute joint.

$image\crank_rod.gif$

Joint between crank and connecting rod

Click create.

A revolute joint between the connecting rod and sliding block will be created next.

Click the joint type: selection switch and select revolute.
Select node ID 25230 as a first terminal (see the following figure).
Select node ID 25232 as a second terminal.
Select coordinates as first orientation and type x=0.0, y=0.0, z=1.0. The z-axis will be the axis of rotation of revolute joint.

$image\rod_block.gif$

Joint between connecting rod and sliding block

Click create.

A translational joint between the sliding block and ground will be created next.

Click the joint type: selection switch and select translational.
Select node ID 14519 as a first terminal (see the figure below).
Select node ID 25228 as a second terminal.
Select coordinates as first orientation and type x=1.0, y=0.0, z=0.0. X will be the direction of translation.
Click create.
Click return.

$image\block_ground.gif$

Joint between sliding block and ground

To create DTI, UNITS:

From the Analysis page, select the control cards panel.
Click DTI_UNITS.
Define the unit system as shown below.

$image\dti.gif$

Click return twice.

To define MBSIM and INVELB:

Click the Collectors toolbar button $image\collectors.gif$ .
Click the collector type switch and select load collectors from the pop-up menu.
Click name= and enter SIM.
Click color and select any color.
Click the creation method switch and select card image from the pop-up menu.
Click card image= and select MBSIM.
Click create/edit.
Input the values as illustrated below.

$image\mbsim.gif$

Click return.
Click name= and enter Velocity.
Click color and select any color.
Click the creation method switch and choose card image from the pop-up menu.
Click card image= and select INVELB.
Click create/edit.
Click BID and select block.

$image\bid.gif$

Click VX and enter -50.
Click return twice.

To create an OptiStruct subcase:

From the Analysis page, select the subcase panel.
Select the type: multi-body dynamics.
Click name= and enter dynamic.
Check the box preceding MBSIM.

An entry field appears to the right of MBSIM.

Click on the entry field and select SIM from the list of load collectors.
Check the box preceding INVEL.

An entry field appears to the right of INVEL.

Click on the entry field and select velocity from the list of load collectors.
Click create.
Click return to go to the main menu.

Submitting the job

To launch OptiStruct:

Select the OptiStruct panel on the Analysis page.
Click save as… following the input file: field.

A Save file… browser window pops up.

Select the directory where you would like to write the OptiStruct model file and enter the name for the model, slider_crank_complete.fem, in the File name: field.

The .fem file name extension is suggested for OptiStruct input decks.

Click Save.

Note that the name and location of the slider_crank_complete.fem file is displayed in the input file: field.

Set the memory options: toggle to memory default.
Click the run options: switch and select optimization.
Set the export options: toggle to all.
Click OptiStruct.

This launches an OptiStruct run in a separate (DOS or UNIX) shell.

The default files written to the directory are:

slider_crank_complete.html	HTML report of the analysis, giving a summary of the problem formulation and the results from the final iteration.
slider_crank_complete.out	OptiStruct output file containing specific information on the file set up, estimates for the amount of RAM and disk space required for the run, and compute time information. Review this file for warnings and errors.
slider_crank_complete.h3d	Binary results file (Nodal results).
slider_crank_complete.stat	Summary of analysis process, providing CPU information for each step during analysis process.
slider_crank_complete_osm.abf	Binary plotting file.
slider_crank_complete_mbd.h3d	Binary results file (Modal results).
slider_crank_complete_osm.log	Log file from OS-Motion containing the information on the joints and markers, simulation etc.., which are specific to MBD analysis.
slider_crank_complete_osm.mrf	Binary results file for plotting.
slider_crank_complete_osm.xml	Model file in .xml format – solver intermediate input deck.

Viewing the Results in HyperView

This section describes how to view the results in HyperView which will be launched from within the OptiStruct panel of HyperMesh.

HyperView is a complete post-processing and visualization environment for finite element analysis (FEA), multi-body system simulation, video and engineering data.

To view a contour plot of the displacement and stress:

While in the OptiStruct panel of the Analysis page, click the green HyperView button.

Note that the path and filename for slider_crank_complete.h3d appears in the fields to the right of Load model and Load results. This is fine because the .h3D format contains both model and results data.

The model and results are loaded in the current HyperView window.

Click the Contour panel toolbar button, $image\5020_contour.gif$ .
Under Results type:, select Displacement.
Click Apply.
Verify that the Animate Mode Menu is set to Transient, $image\light.gif$ .
Click the traffic light icon $image\traffic.gif$ to start the animation.

$image\disp_res.gif$

Displacement results

Click the director's chair icon $image\directors.gif$ to go to the Animation Controls panel.
With the animation running, use the slider bar next to Speed: on the left side of the panel to adjust the speed of the animation.
Click the traffic light icon $image\traffic.gif$ to stop the animation.
Go to the contour panel $image\5020_contour.gif$ and select Element Stresses [2D & 3D] as Results type.
Stress type should be von Mises.
Click Apply.
Click the traffic light icon $image\light.gif$ to start the animation.

$image\stress_res.gif$

Stress results

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