Momentum – 360 Linear Momentum
Overview: Computes the Impact Speeds, DeltaVs, PDOFs, Energy and Momentum data for angular and inline collisions.
Entry into Module:
This module of the program is normally entered by clicking on the REC-TEC block in the upper left of the REC-TEC Window causing the drop-down menu to appear. Place the cursor on the Momentum block and click on 360 Linear Momentum on the sub-menu to initiate this module.
Under certain circumstances, the user may choose to use the Files block instead of the drop-down menu approach. Selecting any file with an .LMO extension in the Dialog box accessed from either the Open Single File or Open Multiple Files block opens this module.
Selecting AutoLoad [ON] from either the Setup Menu or the AutoLoad Icon on the upper right side (third line) of the REC-TEC Window automatically loads the scenario that was on the screen when the module was closed, either individually, or when the program was closed. With AutoLoad [OFF] on the main REC-TEC Window, modules will start without loading a file.
Number of Fragments (1 - 4)
· Program accommodates up to four exit fragments for each Entry Unit
Checkbox for Inline Collision (EBS) – Check if Inline Collision with or without known EBS values for vehicles
· Checking this box calls up a frame for entering EBSpeeds for both units if desired. The Equivalent Barrier Speeds enter into the computations for the impact speeds. If unknown program generates a Minimum/Maximum value for V1 and V2.
V2 Speed (Known) – Enter Value in Textbox
· Negates the computation of V2 and proceeds to compute V1 based on the value entered.
Checkbox for Inline Collision (V’ & Ed or Dv1) – Check if Inline Collision with known common, post-impact speed (V’) plus, either a known DeltaV1 or, known total Damage Energy.
· Checking this box calls up a frame for entering known Common Post-Impact Speed for both units. The known DeltaV1 (use +/- sign) or total Damage Energy must also be entered. This procedure computes the approach angles for the vehicles.
This module contains the following data entry blocks for each of the two Units within the leftmost set of frames:
· Angle (1 or 2) – Approach Angle (Enter appropriate angle for Left or Right Hand Coordinate System / Heading or Radial configuration)
· Motion Analysis files may be used for Departure information (single fragment only). These files will supply Departure Speeds and Trajectory data for Animation.
Odd / Even Fragments:
· Angle (N) – Approach Angle (Enter appropriate angle for Left or Right Hand Coordinate System / Heading or Radial configuration)
· Weight – Entered as actual weight or ratio
· Speed – Enter Post-Impact speed or enter zero (0) to display frame for entering the following data: Entering “X” for the Speed of V3 initiates entries and computations using the Longitudinal DeltaV (CDR) and user supplied PDOF for Vehicle 1 in lieu of the post-impact speeds of both vehicles. This computation can be used as a conformational check on other data.
· Longitudinal DeltaV for Vehicle 1 - (CDR download)
· PDOF (1) – User supplied
· Slip Angle (Degrees)* - Angle between the Longitudinal Axis of Vehicle 1 and its Pre-Impact direction of travel
· Grade (Test)
· Grade (Scene)
· % Braking (100)
The two frames on the right side of the screen show the Output – Unit (1 or 2) information as follows:
· PDOF(A-Number) – Direction of Impulse Vector relative to heading of Vehicle
· Impulse: Change of Momentum
· DeltaV-Lat: Lateral Change of Velocity (Primary)
· DeltaV-Lat: Lateral Change of Velocity (Secondary)
· DeltaV-Lng: Longitudinal Change of Velocity (Primary)
· DeltaV-Lng: Longitudinal Change of Velocity (Secondary)
· DeltaV: Change of Velocity (Primary)
· DeltaV: Change of Velocity (Secondary)
· Speed: Impact Speed (Primary) – Input or Computed
· Speed: Impact Speed (Secondary) – Input or Computed
Intercept (Pre-Impact) and Separation (Post-Impact)
· Angle: Intercept (Closure) / Separation
· Momentum: Pre-Impact / Post-Impact
· Energy: Kinetic at Impact / Kinetic after Impact
· Energy: Actual / Maximum for Damage including Rotation
· Speed: Speed (Primary) – Closure / Separation
· Speed: Speed (Secondary) – Closure / Separation
· Speed: Impact Speed (Primary)
· Speed: Impact Speed (Secondary)
· eVelocity: Coefficient of Restored System Velocity (Restitution)
· rVelocity: Coefficient of Retained System Velocity (Vs/Vc)
Several Command Buttons appear in a frame located at the lower right corner of the module Window. The Command Buttons allow the user to engage options including the option to Open and Save the data required to generate the scenario shown on the screen at the time the file was saved.
· Open .CSV File – Calls up a Dialog box, which can Open a pre-existing CadZone (.CSV) Linear Momentum file and displays the output results.
· Open .LMO File – Calls up a Dialog box, which Opens any pre-existing .LMO file and displays the output results.
· Save .LMO File – Calls up a Dialog box, which Saves data on the screen to files with any user-selectable filenames. This is independent of the automatic saving as “LastFile.LMO” of the data at the close of this module or the close of the program.
· Formulae – Opens a word processor (set by the user in Setup) with a file showing the basic formulae used in this module of the program. While the user may add to or modify the information in this file, it does not change the formulae imbedded into the program.
· Formulae* - Toggles a frame displaying the formulae for computing the unknowns in this module. In addition to the basic formulae, the frame shows intermediate steps with the actual input data shown in the computation.
· Graphics – Displays the Linear Momentum graphics along with LM data on the sight side of the screen. Clicking on the right mouse button brings the graphics for calculating the Line of Impact and Restitution. [Esc] to Exit
· Vector Analysis – Displays the Linear Momentum Vector Sum Analysis diagram along with LM data on the sight side of the screen. Line of Impact is toggled by clicking the right mouse button. [Esc] to Exit
· Velocity Vector Analysis – Displays the Velocity Vector Analysis diagram along with LM data on the sight side of the screen. Line of Impact is toggled by clicking the right mouse button. [Esc] to Exit
· Animation –The display shows the two Units in 360-degree format. This module permits loading scale vehicles (.CRS – Crush) in animation – negates tilting of Z-Axis. Vectors scaled to Velocity/Distance, Velocity or Momentum. User selectable views include the ability to Tilt or Rotate the X, Y and Z-Axis of the animation. Maximum Engagement point can be matched to collision. Animation may be stopped and then resumed using the mouse or the spacebar. [Esc] to Exit.
Using the Animation interface, the selected Vehicle and Motion Analysis files can be previewed by clicking on the V1 / V2 buttons.
Note: Files may be removed by clicking on Browse or M/A File as appropriate and then selecting Cancel.
· Energy Momentum – Uses an Energy-Momentum Quadratic to calculate the correct angular relationship between the Approaching Units and showing the computed angle for Unit 2. The screen shows the new Impact speeds based on the changed angle and allows transfer of the information back to the Linear Momentum main entry screen correcting Approach Angle 2.
· N – This button toggles a graphical number pad on the screen that can be used to enter data into the input boxes without using your keyboard number pad. This may be useful for presentations as data entry can be accomplished using a wired/wireless mouse.
· Iteration / FDA Menu – Calls up a frame that permits the user to input the minimum and maximum values for selected input variables along with the interval for Iteration. If Finite Difference Analysis (FDA) is selected, the resulting analysis computes the uncertainty level for the specified range of the input variables.
For a more in-depth description of Finite Difference Analysis, see the Finite Difference Analysis Section of this Manual – Press [F2] from any Active module of the program.
· 360LM > smac-RT (New) – Platinum Version option. If the user has specified CRUSH file (.crs) vehicles with the latest formatting, this option will assist in creating the initial setup file in SMAC.
Note: The vehicles can be entered using the tools available in the Animation option. The file must be in one of the recent formats for .crs files. This may be accomplished by loading an older format .crs file into CRUSH and resaving it as a named file after engaging the Graphics Suite option in CRUSH.
When this option is selected, the user will be shown the “B” stiffness value for each vehicle as well as the “Kv” value computed for the damage and impact speed in this collision. The user may then specify which value is transferred.
Selecting Transfer to SMAC calls up the interface for the SMAC module, transferring information from the Vehicle files along with Linear Momentum data to the SMAC interface. The program will position the vehicles so that the Centroid of Damage of each vehicle will both cross over the same point one second into the run. No post-impact data (acceleration/steering) is transferred and only a generic friction value is transferred, as this information is not available from CRUSH or Linear Momentum. This information can be entered directly on the SMAC interface.
Minor changes to the positions of the vehicles are easily accomplished in SMAC using the improved Scene option from the SMAC interface, which now provides for incremental (graphic) repositioning using right, left, up, and down (+/- X and Y axis) buttons for each vehicle.
The SMAC interface now has a Collision Interface Protocol (CIP) that repositions the Collision Interface using just a few mouse clicks. This procedure is especially useful when animating over bitmaps such as CAD drawings, aerial photographs, and other bitmap (bmp, gif, jpg) files. This is made even simpler by using the LM>SMAC transfer.
Exiting the SMAC interface (remember to save the file as a named file) will return the user to the Linear Momentum module. The Linear Momentum file should also be saved as a named file.