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Adjustable Shock Absorber for Oversized Application

Description:

OUSD (R&E) CRITICAL TECHNOLOGY AREA(S): Sustainment

 

OBJECTIVE: Develop a large, adjustable shock absorber that can be tuned prior to compression in order to absorb energy and shock that varies in magnitude from one event to the next.

 

DESCRIPTION: The Navy requires a shock absorber that is larger in size than typical shock absorbers and that can be adjusted/ programmed to a specific setting prior to an event in order to optimize the resistance (i.e., rate of energy absorption for a given velocity and stroke position) given the expected initial conditions. This shock absorber will be required to dampen initial shock impulses and resist forces applied to it by converting kinetic energy to another form (such as heat or electricity) that can be safely dumped to the ambient environment. State-of-the-art shock absorbers are comparatively much smaller in size than required for this application. Prior research in this area of study has primarily focused on the fields of electromagnetism, and materials and fluid sciences, including rheology and tribology. However, innovative solutions leveraging other advances or developing new technologies are also welcome and encouraged. Although non-mechanical adjustment is preferred, the Navy is open to all ideas and will not limit innovation or disqualify a particular class of concepts. Many Navy and commercial applications utilizing relatively smaller shock absorbers and/or hydraulic cylinders would benefit from this technology if successful. The requirements of this shock absorber are as follows:

 

1. A shock absorber that is larger in size than typical shock absorbers, and that can be adjusted/programmed to a specific setting prior to an event in order to optimize the resistance (i.e., rate of energy absorption) given the expected initial conditions.

2. The shock absorber shall be required to damp initial shock impulses and resist forces applied to it, converting kinetic energy to another form of removable energy.

3. Heat must be released; electricity must be dumped/recovered.

4. The shock absorber design may include typical components, such as a cylinder, piston rod, accumulator, and check valve; or utilize a completely novel design.

5. Non-mechanical settings adjustment is preferred, but not mandatory.

6. Scalability of this technology is a desired objective.

7. The shock absorber shall satisfy all requirements in the military standards for vibration (MIL-STD-167-1A [Type 1]), shock (MIL-DTL-901E [Grade A]), electromagnetic interference (MIL-STD-461G), and environmental factors (MIL-STD-810H).

8. The shock absorber shall be operable in an industrial and marine environment.

9. Shock absorber shall fit within a space of 23 in. by 23 in. by 109 in. (58.42 cm by 58.42 cm by 276.86 cm) compressed.

10. Shock absorber stroke shall be no greater than 9 ft (2.74 m).

11. The shock absorber weight, including supports, shall not exceed 10,500 lb. (4,762.72 kg).

12. The shock absorber connects to a wire rope via multiple sheaves. Due to the nature of the application, the piston rod (or equivalent) will experience a different amount of input force and speed each time it is cycled. The velocity and force of the cable shock absorber shall be predictable in nature for set input loads.

13. The shock absorber shall be adjustable by adjusting the rate of stroke/energy absorption for low, medium, and high energy events (or with greater granularity).

14. The shock absorber shall compress during an event, and then extend to its original position after an event; this application does not call for a shock absorber that oscillates in the positive and negative directions during operation.

15. The shock absorber shall be adjustable to satisfy all specifications of the existing shock absorber operations.

16. The shock absorber shall be controllable/programmable to provide a force from nominally 0 lbf to 250,000 lbf, throughout its stroke and speed range, with a max stroke of 9 ft (2.74 m) and a speed range of 0 ft/s to 40 ft/s (0 m/s to 12.2 m/s), all while maintaining positive tension on the wire rope.

17. The shock absorber shall be controllable/programmable in its return to starting position by providing nominally 0 lb. to 35,000 lb. (0 kg to 15,875.73 kg) of force and 0 ft/s to 5 ft/s (0 m/s to 1.52 m/s).

18. The shock absorber shall provide a resistive force of up to 35,000 lb. (15,875.73 kg) indefinitely while in its starting position.

19. The tunable shock absorber shall have a minimum of 3 settings.

20. It is desirable that the shock absorber is capable of adjusting its setting within 5 seconds; however, if longer times are necessary to adjust the shock absorber setting, the setting shall be constantly maintained throughout repetitive cycles without deliberate adjustment.

21. The shock absorber shall operate within a temperature range of -13°F and 149°F (-25°C and 65°C) and withstand a storage temperature range of -27 °F and 160 °F (-33 °C and 71 °C).

22. The shock absorber shall provide functionality repeatedly for multiple cycles, at a minimum cycle time of 45 seconds, for 28 consecutive cycles in 21 minutes.

23. The shock absorber will experience cyclic loading so consideration in later phases shall be given to how repeated use will affect performance from a thermal and stress/fatigue standpoint.

24. The shock absorber shall be capable of supporting a cyclic operation sustained rate of 4,200 (Threshold)/5,600 (Objective) total cycles sustained over 30 operating days (12 hrs.).

25. The shock absorber shall be capable of supporting a surge cyclic operation sustained rate of 270 (Threshold)/310 (Objective) total cycles sustained over four (4) (Threshold)/6 (Objective) operating days (24 hrs.).

26. The shock absorber shall be capable of supporting a cyclic operation of at least 500,000 cycles within a 25-yr life without failure in fatigue.

27. The shock absorber shall be capable of monitoring and providing real-time information on the stroke position as well as the conditions of the system (e.g., hydraulic pressure and temperature).

 

The ability to provide dynamic control throughout the shock absorber stroke is not required.

 

Innovative solutions leveraging other advances or developing new technologies are also welcome and encouraged.

 

PHASE I: Design and develop a concept for an adjustable shock absorber that utilizes technologies that will allow it to function at the scale required for this application. Demonstrate feasibility using modeling and simulation, including 3D computer-aided design (CAD), fluid mechanics, stress analysis, control theory, and other appropriate design methodologies. Clearly explain the means by which the shock absorber response is adjusted. Full-scale designs are preferred, even at this preliminary stage, as size is considered one of the primary challenges. Subscale designs are allowable assuming the concept is scalable. A subscale design has value in that it can be used to inform creation of a physical prototype, which will be required in Phase II. If only a subscale design is provided during Phase I, supporting documentation will be required to assess whether the subscale system can be scaled-up effectively to meet requirements. Prepare a Phase II plan that includes prototype development plans.

 

PHASE II: Design and build a shock absorber prototype based on Phase I work. Prototype design may also include design of a system capable of subjecting the shock absorber to forces that vary in magnitude. Demonstrate the technology by performing preliminary tests that impart characteristic forces on the shock absorber. Utilize sensors and data acquisition to illustrate how the shock absorber absorbs energy/shock, and how the absorption changes when tuned to different settings. Employ iterative design, incorporating changes based on lessons learned during repeated testing. Complete the design, perform final testing, and validate that the concept meets operational needs and will work at scale. Prepare a Phase III commercialization/transition plan that includes construction of a full-scale prototype and verification against requirements.

 

PHASE III DUAL USE APPLICATIONS: Design, develop, and fabricate a full-scale working adjustable shock absorber based on work completed during earlier phases. Perform final testing at full-scale velocities and forces to validate and verify performance. Demonstrate adjustability by absorbing low, medium, and high energies as described.

 

Shock absorbers are used in countless mechanical applications in both the private sector and the DoD to attenuate unexpected shocks and in hydraulic and pneumatic mechanical control systems. The most commonly known applications for shock absorbers are in automobiles to prevent excessive bouncing when a vehicle wheel encounters a road hazard or a pothole. With an adjustable shock absorber, a mechanical control system can increase its functional range without being physically replaced, dramatically increasing the functional range of hydraulic and pneumatic control systems.

 

REFERENCES:

  1. Department of Defense. (2019, January 31). MIL-STD-810H. Department of Defense test method standard: environmental engineering considerations and laboratory tests. http://everyspec.com/MIL-STD/MIL-STD-0800-0899/MIL-STD-810H_55998/
  2. Department of Defense. (2017, June 20). MIL-DTL-901E: Detail specification: Shock tests, H. I. (high-impact) shipboard machinery, equipment, and systems, requirements for. http://everyspec.com/MIL-SPECS/MIL-SPECS-MIL-DTL/MIL-DTL-901E_55988/
  3. Department of Defense. (2005, November 2). MIL-STD-167/1A. Department of Defense test method standard: Mechanical vibrations of shipboard equipment (Type I-environmental and Type II-internally excited). http://everyspec.com/MIL-STD/MIL-STD-0100-0299/MIL-STD-167-1A_22418/
  4. Department of Defense. (2015, December 11). MIL-STD-461G: Department of Defense interface standard: Requirements for the control of electromagnetic interference characteristics of subsystems and equipment. http://everyspec.com/MIL-STD/MIL-STD-0300-0499/MIL-STD-461G_53571/

 

KEYWORDS: Shock Absorbers; Hydraulics; Dampeners; Control Systems; Rheology; Tribology; Electromagnetics

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