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The automobile industry is seeing an increased need for the application of plastics and their derivatives in various forms such as fiber reinforced plastics, in the design and manufacture of various automotive structural components, to reduce weight, cost and improve fuel efficiency. A lot of effort is being directed at the development of structural plastics, to meet specific automotive requirements such as stiffness, safety, strength, durability and environmental standards and recyclability. This paper presents the many different conceptual cross sections being evaluated during the development of fiber reinforced plastic automotive cross sections. The concepts consists of foam filling of the fiber reinforced plastic cross sections with light weight metal or composite reinforcements. The metal reinforcement is in the form of lightweight metallic tubes. The composite reinforcement is in the form of a carbon fiber bundle.

With the increasing emphasis on fuel efficiency and environmentally friendly vehicles, much effort is being directed by the auto industry to develop efficient, lightweight and alternative-powered vehicles. One of the ongoing research programs at DaimlerChrysler's Liberty and Technical Affairs is not only aimed at reducing the overall weight of the automobile body structure, but also reducing the cost of manufacturing it. In addition, an automobile body structure needs to meet the requirements of noise, vibration and harshness (NVH), durability, crashworthiness and recyclability. The objective of this paper is to provide a review of the ongoing research and development activities leading to an automobile body structure that meets the above objectives. The paper highlights the many different technology development challenges faced during the process.

The purpose of this work was to measure on-road the objective and subjective changes in vehicle interior noise due both to changing from the current 3-ply windshield construction to an experimental 2-ply windshield and to changing the thickness of the single glass ply in the 2-ply construction. Measurements and subjective ratings of interior noise were made under a variety of test conditions in two nominally identical vehicles. One vehicle served as the “baseline” vehicle, while the other vehicle contained the particular windshield under test. Test conditions were chosen to study how the interior noise due to the intrusion of traffic noise, engine noise, road noise, windrush noise, raindrop noise, and wiper blade-on-windshield noise was changed by the various windshields. A jury of test subjects rated the interior noise on a 10-point scale in both front and rear seat positions in back-to-back rides in the two vehicles.

A new experimental procedure, analogous to that used in structural modal analysis, has been developed to perform acoustic modal analysis in three-dimensional cavities. The procedure involves measurement of the vector components of the acoustic particle acceleration using two closely-spaced microphones. Particle acceleration transfer functions are then determined using these measurements referenced to either a third microphone mounted near the source driving the cavity or an accelerometer mounted on this source. Since these transfer functions contain both magnitude and single axis directional information, acoustic mode shape results can be determined unambiguously. This is not the case if acoustic pressure transfer functions are measured. Standard FFT equipment is used to perform the measurements, and the procedure is easily implemented as a “user data acquisition procedure” in standard structural modal analysis software.

Experimental investigations were conducted to identify and quantify the noise mechanisms of individual elements of truck tire tread patterns. The element under study was handcarved into an otherwise blank tread, full-rubber-depth truck tire. The tire was mounted on the GMR Single Wheel Tire Noise Trailer and the noise radiated by the element was measured on-road as a function of position within the contact patch and tire speed using the two-microphone cross-spectral method of measuring acoustic intensity enhanced by position-triggered sampling. This report deals specifically with the noise mechanisms of cross groove type tread elements, which includes both individual cross groove and cross lug elements. The parameters investigated included groove depth, angle of the groove relative to the sidewall, groove shape, and spacing between grooves.

A technique has been developed to evaluate interior wind rush noise during wind tunnel tests of full-size clay models of vehicles. A small, box-like enclosure with acoustic characteristics made similar to those of a typical vehicle interior is inserted into the clay model behind an actual front sideglass. The wind rush noise coming through the sideglass is directly measured by microphones located within the enclosure. The technique can readily detect wind rush noise changes due to body modifications in the vicinity of the windshield-pillar. In addition, the wind tunnel results agree well with those found on-road.