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Development and validation of adaptive ride down safety systems
2006 (English)Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

The work done in this master thesis can de divided into several categories, but the main idea was to optimize the principle of energy absorption that was developed in the Sirius course. If possible, the principle would then be implemented in three applications in the interior of a personal vehicle. These applications were the steering column - which would get the main focus, the ride down seats and the shoulder belt load limiter. A drop test rig, which tried to resemble a crash situation, was built in order to test di erent materials and cutting geometries. By input from VMCC, the mass of the weight and the height from which it was dropped could be calculated. From previous experience it was known that a material that gave short chips gave large fluctuations in force, so a search was carried out to find materials that would give long chips. Also, the geometry of the cutting insert was thought to play a role in the stability of the resulting forces. Therefore, an investigation of cutting geometries was carried out. This resulted in five di erent materials (aluminium, copper, brass, bronze and PTFE) and six cutting geometries that were to be tested. A testing matrix was developed so that each cutting geometry would be tested three times on each material. This first test series lead to the conclusion that aluminium was the most suitable material, but it was also realized that the test rig was not sti enough to decide the best geometry of the cutting insert. This understanding lead to a redesign of the test rig. In the second test setup two cutting inserts were put with cutting edges pointing towards each other, and the aluminium test plates fell down between. This way the perpendicular forces were cancelled out and the cutting process got much more stable. Again, all cutting geometries were tested, but only with the aluminium test plates. After some statistical analysis, the choice of most optimal cutting geometry could be decided. With both the material and cutting geometry chosen, other parameters could be examined. Different cutting depths were tested to see if a dependency between depth and force could be found. An almost linear relationship was found when the cutting depth was plotted with the cutting force, but a somewhat di erent behaviour was shown when the specific cutting force was plotted next to the force. This means that if both cutting inserts has nearly the same cutting depth the force is linear to the cutting depth, but if they di er, especially at low cutting depths, the linearity is broken. Tests with varying temperatures were also carried out. A series of tests were performed both at -15 C and 55 C, but no big di erences could be seen in relation to the tests performed at room temperature. Finally, the static load at which cutting first started was investigated. A test performed in a tensile strength measuring machine showed that the cutting force is independent of the velocity. This was also confirmed when looking at the plots from the drop tests, as the force did not rise towards the end of the cutting process, when the cutting velocity obviously was lower. To summarize the energy absorbing principle, the tests performed in this work show that the stability of the force level is strongly depending of the material. The cutting geometry has only a small influence, while the temperature and the velocity has little to none. Design proposals of the steering column, ride down seats and shoulder load limiter are presented at the end of this rapport, specially designed to take as little space as possible and using the same principle as in test setup two.

Place, publisher, year, edition, pages
Keyword [en]
Technology, Säkerhetssystem, Energiupptagningar, Styrkolonner, Bilar
Keyword [sv]
URN: urn:nbn:se:ltu:diva-49138ISRN: LTU-EX--06/167--SELocal ID: 68764da4-e8a5-4a15-9ffc-fbbff59b5fa0OAI: diva2:1022483
Subject / course
Student thesis, at least 30 credits
Educational program
Mechanical Engineering, master's level
Validerat; 20101217 (root)Available from: 2016-10-04 Created: 2016-10-04Bibliographically approved

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