Jeep Wrangler Has “Hot Blow-Formed” Steel Sport Bars
The new generation of the Jeep Wrangler, which is on sale now, has “Hot Blow-Formed” sport bars. This is what FCA calls the sports bars running from the start of the A-pillar back to the end of the C-pillar. FCA body systems and components engineer, April Bagley, has explained the technology of the structures during the 2019 Great Designs in Steel, which happened in May 2019. The Wrangler started with new 2018 model year, so repairers are probably already seeing them.
According to Bagley, the sports bars are made in part of the 14.4 percent of the vehicle hot-stamped ultra-high-strength steel. FCA’s free OEM repair procedures indicate they’re two unsectionable, 1,300-megapascal structures connected at the B-pillar. It’s unclear if the free FCA PDFs are updated consistently to reflect the content on the paid site.
Bagley said the tubes were formed by introducing hot air into steel within a die, blowing up the iron to the appearance of the die. A dose of water then quenches the structure into the sturdy, light construction you receive. The technique also allows for multiple sections and dimensions, reducing residual stresses and tighter tolerances, she said, calling the latter essential for an upper body.
It has removed six bolted joints, which is worth 26 bolts from the process. FCA wanted to use the 2018 Wrangler’s sports bars which meet the roof crush requirements. “It was a challenge,” Bagley said.
The front sports bar remains constant. The rear sport bars differs between the two- and four-door Wrangler. “The sports bar is our upper body, it needed to be dimensionally stable and structurally sound,” Bagley said.
The Jeep repair procedures have part or all of the B-pillar (which is the entire structure on the two-door and the outer of the four-door), and the hinge pillar reinforcement is 1,300 MPa. They are not permitted to be sectioned. Just like the B-pillar inner on the four-door Wrangler, which is a 690 MPa, and it can’t be sectioned either.
From the presentation, it’s unclear if the B-pillar on the two-door Wrangler alternative is blow-formed, according to repairerdrivennews.com. “Due to the usage of the type of metal in conjunction with the tensile strength involved on the inner components and reinforcements sectioning of these parts are not allowed,” it’s found in the free repair procedures that FCA writes. “Complete replacement of the component or reinforcement is the only acceptable repair.
“It will be necessary to use a Tungsten Carbide Drill Bit to release the spot welds along with the areas where these parts join other components.” Bagley also said the blow-formed sports bars play a role in the Wrangler’s small-overlap crash protection too. The IIHS test involves driving the driver and the passenger-side quarters of the front end into a 5-foot-tall barrier at 40 mph, which simulates what it feels like smacking into a tree.
Bagley said that test is a “new feature for us.” It could be a reference to the prior-generation Wrangler which debuted in the 2007 model year, which was five years before the IIHS test’s introduction. The old Wrangler did well, considering that the two-door version got a “marginal,” but the four-door Wrangler received a “good.”
The structure is a combination of frame and body structural load paths, which absorbs push and energy from the Wrangler off the barrier, according to Bagley. Bagley’s presentation portrayed a DP-780 hinge pillar outer, HSLA-550 shear plate, and TRIP-690 hydroformed tubes containing a fiberglass-reinforced composite insert. The HSLA-340 spring seat appears on the frame rail, which is what the presentation presents.
Defensive structures like sports bars and other hot-stamped reinforcements. High-strength steel load paths prevent intrusion into the passenger cabin and provide a safety cage, according to Bagley. Bagley’s presentation has indicated the “Upgraded Sill section for higher strength” and has mentioned the “State-of-the-art detailed simulation models used for spot weld and material rupture characterization.”
FCA used the “same strategy,” for side-impacts Bagley said. According to Bagley, the high-strength steel underbody cross members, the sport bar, and the hot-stamped B-pillar all play a role. Bagley has also pointed out that the B-pillar had a lower-strength transition and soft-zone to manage the energy.
Roof crush strategies also included a high-strength steel front header. According to the presentation, there are also roof bows to transfer energy across the vehicle.