|July 5, 2011
Source: Audi of America
The body of the Q3 establishes the foundation for the high build quality, the sporty handling, the acoustic comfort of the cabin and safety. Large portions of it are made of high-strength steels, which are a decisive factor for the high static and dynamic rigidity. Two torsion rings – in the area of the rear seats and the cutout for the tailgate – also make significant contributions here.
Audi once again demonstrates its competence in “ultra” lightweight construction with the Q3. The front-wheel drive version of the compact SUV, scheduled to appear somewhat later, weighs 1,445 kilograms (3,186 lb), with the body-in-white accounting for just 301 kilograms (664 lb). Even the add-on parts are lightweight. The engine hood and the wrap-around tailgate are made of aluminum. They weigh just 8.8 and 10.8 kilograms (19.40 and 23.81 lb), respectively – nearly 50 percent less than corresponding parts of steel sheet. The engine hood is secured to the body by two releases, allowing a crash-optimized construction with low sheet thicknesses and high geometrical stability.
The occupant cell integrates numerous panels with tailored thicknesses (tailored blanks). 74 percent of all panels in the body are made of high-end steels. Topping the materials pyramid are the hot-shaped steels. The blanks are heated in a furnace to over 900 degrees Celsius (1,652 degrees Fahrenheit) and shaped immediately thereafter at around 200 degrees Celsius (392 degrees Fahrenheit) in a water-cooled pressing die.
The abrupt change in temperature imbues the finished panels with a tensile strength of up to 1,550 megapascals – the same as the cables of a suspension bridge. A single wire with a cross-section of one square millimeter can suspend a weight of 150 kilograms (331 lb). The martensitic structure of the panels can only be machined with a laser or diamond-coated tools.
Hot-shaped steels, which because of their strength require only relatively low wall thicknesses, make up 13 percent of the body. They are used in the transition from the front end to the occupant cell, at the center tunnel, in large areas of the roof frame, for the interior sills and for the B-pillars. The latter are each formed from a single blank, but undergo different heat treatments in different areas. As a result, their strength varies in three zones so that the B-pillars offer optimal protection in a side-impact collision.
One factor for enhanced rigidity is 74 meters of structural adhesive. The adhesive bonds supplement the 4,400 weld points and provide for strong and tight connections, often eliminating the need for additional sealing and corrosion protection measures – which in turn saves weight.
The seam around the water outlet at the trunk and the invisible seam between the side panel and the roof – two particularly problematic areas – are made using the laser beam or the plasmatron brazing process. Audi performs both high-end processes with exacting precision. The roof joint strips are eliminated. Laser welds also join the frame and the interior portions of the doors.
Carefully matched: vibrational comfort
The development engineers precisely matched the resonant frequencies of the body and those of the add-on and internal components to give the Q3 its excellent vibrational comfort and acoustics. Bulkheads and lightweight materials such as foams and spray insulation divide large cavities like the D-pillars and have a calming effect on the large sheet metal surfaces. In addition to the good acoustic properties, these measures offer the added advantage of saving two to three kilograms (4.41 to 6.61 lb) of weight compared to thick film coatings.
Particular attention was focused on sound radiation in all areas where the driver and front-seat passenger are in contact with the car, such as the seats, parts of the floor and the steering wheel.
The engineers use state-of-the-art simulation tools and computational methods in all fields of work. For example, they were used to develop a reinforcement for the tailgate latch with molded bulkheads that significantly reduces the sound radiation of the tailgate. Another factor contributing to the low noise level on board the Q3 are the sophisticated seals at the doors and windows, plus numerous geometric details of the body. Audi also offers an acoustic windshield with a noise-damping intermediate film as an option.
Enhanced safety: excellent occupant protection
The Audi Q3 is also at the head of its class when it comes to passive safety. There are three load levels in the front end. The lowest one comprises the subframe for the front axle. Two longitudinal members are used on the middle level. Connected to one another via the front cross-member, they distribute the load in an offset crash to both sides of the occupant cell. On the top level, two additional members dissipate energy via the fenders.
The ultra-high-strength B-pillars provide outstanding protection in a side-impact collision. Large overlaps brace the doors against the pillars and the triple-shell sills. Two cross-members reinforce the floor structure. The longitudinal members absorb energy in the event of a rear-end collision. Their strength gradually decreases moving forward. The members can be replaced in sections, which reduces costs.
Five crash sensors that react to acceleration and changes in air pressure stand guard in the Audi Q3. One of them is located at the center of the front end, the other four in the area of the B- and C-pillars. They provide detailed information to the airbag controller, which itself includes three sensors.
The compact premium SUV comes standard with two front airbags, thorax-pelvis side airbags in the backs of the front seats and curtain head airbags. Pyrotechnic belt tensioners up front, belt force limiters and the integral Audi head restraint system, which mitigates the consequences of a rear-impact collision, round out the package. Side airbags in the rear are optionally available.
Isofix child seat anchor points in the rear are standard. Sensors monitor whether the rear safety belts are fastened. Isofix child seat anchor points for the front passenger seat together with deactivatable airbag are optionally available. The accessories line includes child seats for every age group.
Audi’s latest model also represents the state of the art when it comes to pedestrian protection. The front bumper and the cross-member behind it, the energy-absorbing foam between the two components and the aluminum engine hood make for an effective package.
Low-speed collisions – the standard insurance category crash and the bumper crash, both of which are important for determining the comprehensive insurance category – result in no major damage. The front cross-member and the crash boxes bolted to the longitudinal members are closed, extruded sections of aluminum. They form a structure that provides effective protection for expensive components such as the radiator and air conditioning units, as well as the welded body structure. The bumper is made up of three parts, each of which can be replaced individually.
Extremely sophisticated: the aerodynamics
The base version of the Audi Q3 boasts a coefficient of drag of 0.32 – tops among its competition. It has a front surface area of 2.44 square meters (26.26 sq ft). The low lift at the axles ensures superior stability at high speed.
The aerodynamic specialists at Audi performed exhaustive fine-tuning with their virtual tools and at the Wind Tunnel Center. They reduced the coefficient of drag by 0.16 from the first design model of the Q3. This resulted in a reduction in fuel consumption of 0.6 liters per 100 km in the EU cycle. At 130 km/h, the result is an even more impressive reduction of 2.3 liters per 100 km.
The greatest challenge proved to be the rear of the car, the zone in which the flow of air has to break off cleanly. The large spoiler with the integrated third brake light over the rear window extends the roof contour by 32 centimeters (12.60 in). Two “aero strips” to the left and the right of the window form lateral spoiler lips. Their black, high-gloss finish lends them a subtle and elegant appearance. The vertical contours in the tail lights serve similar purposes.
Very sophisticated aerodynamic tuning also went into the side mirrors. With their elegant design and slender base, they contribute just 3.1 percent of the total wind resistance. The noise generated at the mirrors remains low, and the glass barely fouls in the rain. The water-catching strips at the A-pillars keep the side windows clean by diverting the rain water pushed in their direction by the windshield wipers downward or upward.
The underbody also plays a major role in the aerodynamics concept. Except for the exhaust system and the back of the vehicle, it is covered by a plastic liner that protects it against salt and stone chipping and provides for a more aerodynamic flow of air. Small spoiler lips are integrated in front of the wheels. The aerodynamic underbody lowers the coefficient of drag by 0.03 or nine percent, and is precisely matched to the flow separation at the rear of the vehicle.
The aerodynamics experts also pared further valuable percentage points from the flow of air through the engine compartment. The single-frame grille and the surrounding area are completely sealed so that the inflowing air reaches the radiator with almost no losses rather than becoming turbulent.