Previous SEM Test Efforts:
Several test efforts have been run on the SEM shock technology to date. There have been 2 high load drop test efforts and 3 full sized vehicle impact test with impact speeds ranged from low to moderate to high. The following photos (Figs. 1 -6) show the previous drop and crash test efforts that have been performed on various SEM shock designs.
The following is a summary of these previous test efforts.
Fig.1 - In November and December of 1996 a series of drop tests were run at the NUWC (Naval Undersea Warfare Center) Navy test lab in Keyport, WA. Some 30 drop tests were run on a series of SEM shock samples, with the only constant test parameters being the shock housing’s 1.0" ID and the piston’s 9.0" of available travel. The tool’s drop height was 5.5 ft which resulted in an impact velocity of 12.8 mph. A consistent 45 g deceleration was administered to the tool assembly, whereas the 680 lb impact piston, being supported by the SEM shock samples, had a range of deceleration spikes from 17 plus g’s (11,560 lbsf) down to 9.3 g’s (6,324 lbsf). The displacements for the test shocks ranged from 2.5" up to 8.1".
Fig.2 - On June 18, 1997 a series of low speed crash tests were run at the NUWC test facilities, in Keyport, WA. The crash test vehicle was a 1989, 3/4 ton, extended cab, 4 X 4 Chevy pickup, with an approximate gross weight of 5,400 lbs. Seven impact tests were run, with the impact velocities ranging from 3.5 mph up to 7.5 mph; but even at these relatively high speeds, no damages were delivered to the stock Chevy truck parts. Each SEM test shock consisted of a 1.5" OD x 1.0" ID shock housing, with a 0.25" ejection groove and a max available travel of 7.0". All of the ejection material types were elastomers with a nylon fiber weave. A YouTube video of this test effort was recently posted (http://www.youtube.com/watch?v=R9xPNrIvnLM). In this video a recent Insurance Institute for Highway Safety report is referenced which discusses the high damage costs that 17 new model vehicles received in 4 low speed collisions.
Fig.3 - In December of 1998 a more aggressive drop test effort was run by E-Tech Testing Services, Inc. in Rocklin, CA. The E-Tech tool assembly that received the SEM test shocks was statically mounted on the ground and a cable-guided 500 lb impact weight was released from 30 ft. The drop weight obtained impact speeds of approximately 30 mph. Several SEM shock designs were tested, with the only consistent test parameter being a 1.0" OD piston with an available travel of 18.0". All of the SEM test shocks performed within the 18.0" of available travel, with no damage being delivered to any of the SEM shock components.
Fig.4 - In early 1999 a number of high speed vehicle impact tests were run at the test facilities of E-Tech Testing Services, Inc. The testing utilized a modified crash test vehicle that weighed 1,700 lbs. The test vehicle ran two speed ranges: a moderate speed range of 42 mph and a high speed range of 62 mph. The test vehicle impacted a barrier that employed the SEM shock technology with only one 1.25" ID shock housing and a maximum available travel of 15.0 ft.
Fig. 5 &6 - In Nov 2004 and in Nov 2005 a total of 9 impact tests were run at the Texas Transportation Institute (TTI) and the two test efforts were funded by the National Academies High Speed Rail-IDEA program. The major focus of the HSR-45 study was to test SEM modified railcar passenger seats to determine if the impact injures suffered by unbelted railcar passengers could be reduced. In addition to using the SEM shock technology in the railcar passenger seat, SEM shocks were also used in the impact barrier (Fig. 6) to deliver a tailored crash pulse, which mimicked the deceleration history that a passenger train would experience in an aggressive derailment or collision. The SEM impact barrier actually came very close to delivering the spec 8-g by 250 ms triangular crash pulse but in the first test series (Nov 2004) the SEM seat shocks were too stiff, to where the seat structures did all of the yielding. Thus another 3 impact tests were run in Nov 2005 with the SEM seat shocks redesigned. In the 2nd test effort the forward seat shocks performed as planned with some substantial displacement of the seat shocks. When the data was reduced, it was found the existing seat crash load performance had not been greatly improved, with SEM seat shock mods. Instead it was determined that some form of soft padding on the seat back would probably do a much better job at reducing the initial spike loads. This is not to say that SEM seat shocks would not improve some seat designs. For instance if seat structure were designed to do very little yielding much like older seat models (note: this newer seat model was designed to bend or yield under unbelted passenger loading); and the seat backs were padded, then the SEM shocks could be designed into the floor and wall mount to reduce the secondary loading. Also, another seat application that the SEM technology would be ideal for, would be the vertical impact loading which is experienced by military helicopter seating during emergency landings, as well as the vertical spike loading that the personnel seating in military ground vehicles experience during mine blast events. Since there is no "free-flight" before a passenger contacts the seat (e.g. they are always seated) there will be no extreme initial spike loading, as with the unbelted passengers in a horizontal load event.
Lastly, once again it must be pointed out that while the major focus of the HSR-45 study was the seat shock test effort, still the SEM barrier performed extremely well in this test effort by decelerating the 4,100 lbs Bogie test vehicle from its initial impact velocity of 23.5 mph. And in those tests the SEM barrier came very close to delivering the spec crash pulse. A short video clip that touches on the HSR-45 test effort can be found at the following YouTube web address (http://www.youtube.com/watch?v=sF3_Cc8G0zI).
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