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Research Papers

Elastic Leak for a Better Seal

[+] Author and Article Information
Zhengjin Wang

School of Engineering and Applied Sciences,
Kavli Institute for Nanobio Science
and Technology,
Harvard University,
Cambridge, MA 02138
State Key Laboratory for Strength
and Vibration of Mechanical Structures,
International Center for Applied Mechanics,
School of Aerospace Engineering,
Xi'an Jiaotong University,
Xi’an 710049, China

Qihan Liu, Zhigang Suo

School of Engineering and Applied Sciences,
Kavli Institute for Nanobio Science
and Technology,
Harvard University,
Cambridge, MA 02138

Yucun Lou

Schlumberger-Doll Research,
One Hampshire Street,
Cambridge, MA 02139
e-mail: ylou@slb.com

Henghua Jin

Schlumberger-Rosharon Campus,
14910 Airline Road,
Rosharon, TX 77459

Contributed by the Applied Mechanics Division of ASME for publication in the JOURNAL OF APPLIED MECHANICS. Manuscript received May 5, 2015; final manuscript received May 18, 2015; published online June 9, 2015. Editor: Yonggang Huang.

J. Appl. Mech 82(8), 081010 (Aug 01, 2015) (5 pages) Paper No: JAM-15-1222; doi: 10.1115/1.4030660 History: Received May 05, 2015; Revised May 18, 2015; Online June 09, 2015

Elastomeric seals are widely used to block fluids of high pressure. When multiple seals are installed in series and the spaces between the seals contain compressible fluids (e.g., gas or gas–liquid mixture), the seals often damage sequentially, one after another. Here, we demonstrate that the serial seals achieve high sealing capacity if individual seals undergo elastic leak, without material damage. When individual seals leak elastically, fluid fills the spaces between the seals. Instead of damage one after another, all the seals share the load. The elastic leak of individual seals greatly amplifies collective sealing capacity of serial seals.

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Figures

Grahic Jump Location
Fig. 1

Elastic leak of individual seals amplifies the collective sealing capacity of multiple seals. (a) Schematic of a continuous sealing design. (b) Schematic of a spaced sealing design. (c) After sealing, the spaces between sealing elements are partially filled with water. The first element deforms under the external pressure P1, but the second element is nearly undeformed. (d) As P1 reaches a critical value, the first element leaks elastically and the water fills the space between elements. (e) After water fully fills the space between the two elements, both elements deform and resist the differential pressure collectively. (f) The fluid pressures P1 and P2 as functions of time in the process (c)–(e).

Grahic Jump Location
Fig. 2

Experimental setup. (a) Two blocks of a hydrogel, of dimensions h, l, and w in the undeformed state, are glued to a sheet of glass and to an acrylic spacer. Two acrylic steps with height t are glued to the base glass sheet and in contact with the front side of hydrogel blocks. An acrylic sheet of thickness Δh is attached to the cover glass sheet. (b) When the cover glass sheet is glued to the spacer, the hydrogel is precompressed with a displacement Δh. The glass, spacer, and hydrogels define two closed chambers. The first chamber connects to a syringe pump and a pressure gauge, and the second chamber connects to another pressure gauge. (c) For comparison, in the other setup, a hydrogel of dimensions h, 2 l, and w in the undeformed state, is used.

Grahic Jump Location
Fig. 3

Comparison between spaced and continuous sealing designs. In the spaced sealing design, two hydrogels (crosslinker (wt. %) = 0.06% and water (wt. %) = 88%) with dimensions of l = 15.00 mm, h = 6.00 mm, and w = 120.00 mm, is precompressed with a displacement Δh = 0.80 mm, i.e., ɛ=13.3%. The height of the steps t = 2.60 mm. The two chambers are filled with water before loading. The syringe pump injects water at a constant rate of 2 ml/min until the seals leak steadily. In the continuous design, all the conditions are identical to spaced design except the sealing element becomes a continuous block with the dimensions 2 l×h×w. (a) The fluid pressures as functions of time for spaced design. (b) The fluid pressure as a function of time for continuous design. (c) and (d) show the snapshots of the seals at the unpressurized state and leaking state corresponding to (a) and (b), respectively.

Grahic Jump Location
Fig. 4

Spaced sealing design with air filled between elements before loading. Two blocks of a hydrogel with the identical dimensions to the previous test are precompressed with a displacement of Δh = 0.75 mm, i.e., ɛ=12.5%. The height of steps t = 2.57 mm. The syringe pump injects water at a constant rate of 2 ml/min. (a) The fluid pressures in the first and second chambers as functions of time. (b) Three snapshots of the seals corresponding to the states marked in the pressure–time curves in (a).

Grahic Jump Location
Fig. 5

The spaced hydrogels fail sequentially by material damage. Two blocks of a hydrogel (crosslinker (wt. %) = 0.3%, water (wt. %) = 92%) with dimensions of h = 6.00 mm, l = 15.00 mm, and w = 120.00 mm, are precompressed with a displacement Δh = 1.50 mm, i.e., ɛ=25%. The height of steps t = 3.00 mm. The syringe pump injects water at a constant rate of 5 ml/min until both the hydrogels fail. The high concentration of crosslinks makes the hydrogel brittle, so that the individual seal leaks by forming cracks. (a) The fluid pressures in the first and second chambers as a function of time. (b) Two snapshots of the seals corresponding to states marked in the pressure–time curves in (a). (c) Schematic of sequential failing of spaced seals by material damage.

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