Search Results

Friction Stir Spot Welding (FSSW) is an emerging joining technique that has seen some successful automotive applications in the past few years. One of the most significant factors that influence the joint strength of a friction stir spot weld is the tool geometry. The tool geometry used in FSSW has been traditionally derived from friction stir linear welding and there has not been much focus on developing tool geometries specifically for FSSW. The main objective of this paper is to evaluate different pin geometries that are specifically catered towards maximizing the strength of friction stir spot welds. In order to evaluate the effect of only the pin, all tools considered had flat shoulders. Four different pin shapes were evaluated - baseline, thick, tapered and inverse tapered pins. Three different pin lengths were considered for each pin shape - 1.0, 1.2 and 1.4mm.

Experiments were carried out to study the effect of thermal expansion of the tool during Friction Stir Spot Welding (FSSW) of large commercial automotive grade aluminum sheets. The objective of this study was to evaluate the tool “growth” using both experimental and numerical techniques and to see its effect on the weld quality (measured in terms of static strength). Two hundred friction stir spot welds were made over 25 Al sheets (A6022-T4) with a specific time interval between each sheet, thereby trying to simulate the welding conditions/sequence on a production line. An Infrared (IR) camera was used to monitor the temperature gradient on the tool during the welds. In addition, finite element analysis was run to predict the thermal expansion of the tool based on the temperature boundary conditions obtained from the IR camera during the experiment.

This paper describes a cold start emission reduction system developed for a 3.0L V6 test vehicle in order to meet SULEV emission regulations. The emphasis of this research is how the system can be used to meet SULEV emission standards without the need for a heavily loaded catalyst. A fuel-vaporizing device has been developed that generates vaporized fuel to be consumed during engine start up. The device allows for lean A/F ratio control during engine start and idle and is called a Combustion Stabilizing Device (CSD). A vehicle with a CSD mounted to the engine was tested in an emission lab. The test vehicle resulted in approximately 50% HC emission reduction in the first 20s of engine startup and had a catalyst warm-up time to T50 (50% converter efficiency) of less than 20s.

Emissions tests were performed to study the operating characteristics of a wide range air/fuel ratio (AFR) sensor in closed loop control. The AFR sensor used here has an output voltage with respect to AFR that is linear and can be characterized by a fourth order polynomial function. For this study the output signal of the AFR sensor was fed into a General Control Unit (GCU). The GCU converted this analog input signal into a square wave similar to a lambda sensor. The output from the GCU was fed into the Engine Control Unit (ECU) of the 3.8L, V6 test engine to control the engine A/F ratio. Emissions tests were conducted in closed loop mode under steady state and transient condition. Emissions of HC, CO and NOx using the AFR sensor will be shown. Results of these tests showed that the AFR sensor allowed for precise control of the AFR at the stoichiometric point (λ = 1.0).