Ronald Paul Cooper

Elongation Variability of AM60 Die Cast Specimens

Tensile properties of die cast magnesium AM60 were investigated by testing tensile bar specimens obtained from three sources. The first series of tensile bars were cut from eight locations from multiple copies of a die cast magnesium AM60 automotive instrument panel beam. The second series were cut from six-inch square AM60 die cast plates in both the parallel and perpendicular to the flow direction. The last series of specimens were die cast AM60 tensile bars. The measured yield stress did not significantly depend on the specimen source and matched published values. However, the elongation as determined by the engineering strain at break in the tensile test varied significantly for samples cut from the automotive instrument panel beams and those cut from the six-inch by six-inch plates. The elongation remained constant for the cast tensile bars. Statistic General Linear Models were used to study the effect of casting conditions on both the yield stress and the strain at break. Sample location within the beams was the main factor for the material property variation.Copyright

Ultrasonic Welding of Aluminum 6111: Reliability and Maintainability Study of Robot Mounted C-Gun Welding System

Ultrasonic metal welding (USW) is a promising joining method for aluminum automotive body construction applications. During USW, aluminum weldments are joined together by applying high frequency vibrations while holding the parts together with a moderate clamping force. In an effort to further the development of USW for high volume robotic body construction applications, a reliability and maintainability study was performed using a robotic welding cell installed in the Ford Research and Innovation Center. The robot was equipped with a modified Sonobond ultrasonic metal welder, which was mounted on a C-frame. The study consisted of welding fully overlapped 550 mm × 350 mm × 0.9mm thick AA6111-T4 aluminum panels with 330 welds on each panel until 100,000 welds were made. Consistency in welder operation was monitored by welding fully overlapped AA6111-T4 aluminum strips (25mm wide × 550 mm long × 0.9mm thick) at the end of each day’s welding and then tensile testing the strips in a T-peel configuration. There was no statistical difference in average T-peel strength over the course of the 100,000 weld study. There was also no degradation noted in lap shear failure loads between samples welded at the end of the 100,000 weld study and those generated before initiation of the study. Reliability of the USW process during this study was monitored by periodic inspection of the robot and welder joints, attachments, fittings, tip, anvil, clamps, cables, etc. Only very minor wear of the welder tip and anvil contact surfaces were noted after the study was completed. However, during the study, after 82,000 welds a small piece of aluminum was removed from between the tip grooves, even though the weld strength was unaffected by the presence of the aluminum. There were no failures of any mechanical or electrical parts during the study. In addition, primary voltage and current signals of the ultrasonic welder’s power controller were periodically recorded during the weld study and it was determined that there was no change in the electrical behavior of the welder.Copyright

Property Variation Within the Thin-Walled Magnesium Alloy Components

Utilization of magnesium alloys within the field of vehicle design offers substantial opportunity for mass reduction. This has resulted in a wide range of automotive applications. More recently, the scope of application has been extended to include components that are considered crash critical. However, the magnesium die casting process is widely reported as producing parts that exhibit large local variation in part properties. Hence, this introduces the technical challenge of how to design effectively based upon these constraints. In order to better understand this phenomenon, two large size thin walled production components were examined. Tensile test coupons were extracted from multiple locations. Micro and macro level investigations were also conducted in an effort to identify the root cause of property variation. This paper discusses the influences of porosity on mechanical property variation, specifically tensile strain to failure. Further discussion is also presented, detailing a proposed empirical model, for the prediction of local strain to failure.Copyright