Ammunition Dynamics in Rapid Fire Guns using MSC Adams

Transcription

1 Ammunition Dynamics in Rapid Fire Guns using MSC Adams Jerry Browne General Dynamics Armament and Technical Products

2 Abstract Ammunition Dynamics in Rapid Fire Guns Using MSC Adams Presentation Number Jerry Browne General Dynamics Armament and Technical Products 128 Lakeside Avenue, Burlington, Vermont, Phone: , Fax: , Multi-barrel Guns are designed for high rate of fire. High rate of fire requires automated ammunition feed and spent case extraction. The dynamics of an automated ammunition feed system at the gun interface is modeled using Adams. Items included in the model are the following (1) full round of ammunition transported into a multi-barrel gun via feed sprockets, (2) rounds directed by guiding surfaces and sprockets rotating with defined motions, (3) round pick-up and seating in its firing position by gun bolt and (4) extraction of spent case from the gun bolt and rotor along defined path. The Adams model is used to determine the effects of changes in ammunition inertial properties, ammunition surface geometry, guide surface geometry and feed rate on the round hand-off process. The model employs rigid bodies, some of which are constrained to defined motion, and others that are free bodies moving only through contact with guide surfaces and these constrained motion bodies. Shell for all bodies are incorporated and used to generate three dimensional contacting surfaces. These contacting surfaces provide narrow passages with very little room for round path error. It is essential that the hand-off process be well timed and round dynamics be well defined to ensure proper functioning of the gun. This presentation will demonstrate both the capabilities of IDEAS/Adams in simulating such a high speed process, and illustrate where additional capabilities would be an asset to high-speed dynamic processes containing guiding surface contact. 2

3 Agenda Introduction - Project Methodology Details Results Lessons Learned Follow on Work 3

4 Introduction Multi-barrel Guns are designed for high rate of fire. High rate of fire requires automated ammunition handling. IDEAS & MSC Adams used to model ammunition hand-off dynamics at the gun interface. Features of the process are provided in this document 4

5 Methodology Create assembly of parts in IDEAS Include essential only Locate parts in the initial configuration Subdivide large parts Convert assembly to multi-body rigid model using Mechanism Simulation Generate rigid bodies & essential markers Create constraints, splines, forces and motions Complete modeling in Adams Generate body-to-body contacts Run simulation and post process results 5

6 Details Modeled Items: Ammunition (Rounds) transport into a multi-barrel gun via Guides and Sprockets with defined motion Gun Bolt pick-up, seating and transport of round to and from its firing position Unloading of spent case from Gun Bolt, and its transport return to storage container via Sprockets and Guides 6

7 Details - IDEAS Model Objective: Create assembly of parts to represent ammunition passage through gun, feed and unload systems Parts placement in assembly Parts material properties defined Coordinate systems for joints 7

8 Details - IDEAS Model Gun Bolt Ammunition Gun Rotor Feed Guides & Sprockets Unload Guides & Sprockets 8

9 Details MSC Adams Model Objective: Understand round hand-off process & influences: Ammunition inertial properties Ammunition surface geometry Guide surface geometry Feed rate 9

10 Details MSC Adams Model 3-axis Translational Motion: Gun Housing Rotational Motion: Rotor, Feed Sprockets, Unload Sprockets Translational Motion: Gun Bolts Body-to-Body Contact between Ammunition and other Parts 10

11 Details MSC Adams Model Model contains Rigid bodies with motion constraints Free bodies moving through contact with constrained-motion bodies and guide surfaces Shell for all bodies used to generate three dimensional contacting surfaces. Contacting surfaces provide narrow passages; little room for round path error. Hand-off process must be well timed and round dynamics be well defined. 11

12 Details MSC Adams Model Gun Bolt Path Round Path Inner Guides Feed Sprockets Unload Sprockets 12

13 Results MSC Adams Model Animation 1 Two Round Unloading (auto or double-click to play) 13

14 Results MSC Adams Model Animation 2 Two Round Unloading (auto or double-click to play) 14

15 Lessons Learned Surface details significantly influence body-to-body contact. Partitioning solid model surface increases realistic surface contacts Contact with thin shell objects difficult to maintain (large aspect ratio objects slips through its contact. Solution for round ramming into barrel requires extreme care to obtain solution 15

16 Follow-on work / Wish List Replace some rigid guides by their finite element models Rigid-to-Fem or Fem-to-Fem contact difficult to model with moving contact. Wish List Provide simplified method of generating body to body contact between two finite element parts or rigid-to-fem part 16