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Many automotive production plants are using various prepulse schedules for resistance spot welding thin gauge galvanized steel. The claimed reasons are that wider current range and longer electrode life are obtainable in comparison to the conventional schedule. However, data to support this are not available. The objective of this program was to determine the effect of prepulsation on spot weldability of galvanized steel. In this work, several prepulse resistance spot welding schedules were evaluated in two full factorial experiments. The effect of the number of prepulse cycles, the prepulse heat level and the effect of cool time were studied in detail. Weldability was evaluated using an electrode life test procedure in which the current range was periodically examined over the life of the electrodes. Generally, the results indicate that prepulsation has a negative effect on the resistance spot weldability of thin gauge galvanized steel.

Deformation Resistance Welding (DRW) is a process that employs resistance heating to raise the temperature of the materials being welded to the appropriate forging range, followed by shear deformation which increases the contacting surface area of the materials being welded. Because DRW is a new process, it became desirable to establish variable selection strategies which can be integrated into a production procedure. A factorial design of experiment was used to examine the influence of force, number of pulses, and weld cycles (heating/cooling time ratio) on the DRW process. Welded samples were tensile tested to determine their strength. Once tensile testing was complete, the resulting strengths were observed and compared to corresponding percent heat and percent reduction in thickness. Tensile strengths ranged from 107 kN to 22.2 kN. A relationship between the maximum current and the weld variables was established.

Phase IV of the National Highway Traffic Safety Administration's (NHTSA) rollover research program was performed during the spring through fall of 2001. The objective of this phase was to obtain the data needed to select a limited set of maneuvers capable of assessing light vehicle rollover resistance. Five Characterization maneuvers and eight Rollover Resistance maneuvers were evaluated [1]. This paper is “Volume 2” of a two-paper account of the research used to develop dynamic maneuver tests for rollover resistance ratings. Test procedures and results from four Rollover Resistance maneuvers are presented. The Consumers Union Short Course (CUSC), ISO 3888 Part 2, Ford Path Corrected Limit Lane Change (PCL LC), and Open-Loop Pseudo Double Lane Changes are discussed. Details regarding the NHTSA J-Turn, and the three fishhook maneuvers are available in “Volume 1” [2].

Phase IV of the National Highway Traffic Safety Administration's (NHTSA) rollover research program was performed in 2001, starting in the spring and continuing through the fall. The objective of this phase was to obtain the data needed to select a limited set of maneuvers capable of assessing light vehicle rollover resistance. Five Characterization maneuvers and eight Rollover Resistance maneuvers were evaluated [1]. This paper is “Volume 1” of a two-paper account of the research used to develop dynamic maneuver tests for rollover resistance ratings. Test procedures and results from one Characterization maneuver (the Slowly Increasing Steer maneuver) and four Rollover Resistance maneuvers are discussed (the NHTSA J-Turn, Fishhook 1a, Fishhook 1b, and Nissan Fishhook). Details regarding NHTSA's assessment of the Consumers Union Short Course (CUSC), ISO 3888 Part 2, Ford Path Corrected Limit Lane Change (PCL LC), and Open-Loop Pseudo Double Lane Changes are available in “Volume 2” [2].

Resistance welding control systems utilizing secondary current feedback receive widespread utilization both in Europe and Japan. However, these types of control systems are only beginning to be used in any extended basis in this country. Currently, two variants of these systems are available; so called “self-teaching” systems, and “learning curve” systems. Either system has been shown to be capable of providing a stable secondary resistance welding current within two cycles. Recent work has indicated, however, that the self-teaching type control systems may be adversely affected by non-optimum set-up conditions, particularly poor fit-up and the introduction of organics (sealers or adhesives) at the faying surface. This work examines the performance of learning curve type constant current control systems under these adverse set-up conditions. Six conditions were selected for study; three degrees of progressively poorer fit-up, with and without an organic sealer.

The soil response to traffic loads as affected by tire inflation pressure, track width and drawbar pull was measured. The change in soil physical properties caused by a John Deere 8870 tractor at two tire pressure settings and CATERPILLAR Challenger 65 and 75 tractors with 64 and 89 cm wide belt tracks, were measured at two load levels; no draft (tractor only) and tractor pulling a 12.5 m field cultivator. The Ohio State University Soil Physical Properties Measurement System was used to measure cone penetration resistance, air permeability, air-filled porosity, and bulk density. The results show the dual overinflated tires caused the greatest change, followed by the CATERPILLAR Challenger 65 track, then the CATERPILLAR Challenger 75 track, and finally dual correctly inflated tires caused the least effect on soil physical properties. These results were consistent at each depth. The effects of the two draft levels give the same ranking of the tractive units.

Soil response to differences in tire size and inflation pressure was measured for a JD 9600 combine with 18.4R38 dual tires, 30.5L32 single tires, 68x50.00-32 single tires at 103 and 166 kPa inflation pressure and a John Deere half-track system on two different soils (Kokomo and Crosby) near Urbana, Ohio. A loaded 42.3 m3 grain cart was included on the Kokomo soil for comparative purposes. The Ohio State Soil Physical Properties Measurement System was used to sample and measure the bulk density, air-filled porosity, air permeability and cone penetration resistance between 10 and 50 cm depths. The results for Kokomo soil show the grain cart had the greatest effect with an average decrease in total porosity of 12.90 percent, compared to 7.95%, 6.05%, 4.56%, 3.06%, and 2.04% for singles, tracks, duals, wide overinflated, and wide rated pressure tires, respectively, on the combine.

This study examined the effect of primers containing a conductive pigment on the resistance spot weldability of hot-dip galvanized steel. The pigment used was ferrophos, essentially Di-iron phosphide. Basically, two types of tests were used in this work. Current range tests were used to establish the effect these primers have on the effective ranges of weldability. Limited electrode life tests were used to infer the long term performance of the hot-dip galvanized steels with and without this paint. It was found that the addition of the Ferrophos bearing paints had pronounced effects on weldability. Typically, required current levels were reduced by several thousand amps, and effective current ranges were increased by 50 to 100 percent. During electrode life testing significant reductions were also noted both in the rates of electrode face diameter increase, and the degree of electrode pitting.

This paper describes the National Highway Traffic Safety Administration's (NHTSA) efforts to determine how different outrigger designs can affect J-Turn and Road Edge Recovery test maneuver outcome. Data were collected during tests performed with three different outrigger designs (made from aluminum, carbon fiber, and titanium) having different physical properties (geometry and weight). Four sport utility vehicles were tested: a 2001 Chevrolet Blazer, 2001 Toyota 4Runner, 2001 Ford Escape, and a 1999 Mercedes ML320. The 4Runner and ML320 were each equipped with electronic stability control, however the systems were disabled for the tests performed in this study. A detailed description of the testing performed and the results obtained are discussed. From the results, a comparison of how the three outrigger designs affected the test results is provided.