FCA US Discusses the Mixed Material Approach Used on the Chrysler Pacifica, Winner of the 2017 Altair Enlighten Award Full Vehicle Category

31st January 2018

With the recent announcement calling for 2018 Altair Enlighten Award submissions, and to follow the interviews from Toyota and AP&T about their 2017 wins, we’re excited to share another interview video about the mixed material approach FCA applied to the 2017 Chrysler Pacifica, which took home the Full Vehicle category prize.

Shortly after the CAR MBS, we caught up with James Truskin along the Detroit River at the city’s Cobo Center.  In the video below, we capture his thoughts on the state of the industry with regards to lightweight design, some of the processes that took place to achieve the weight savings they did on the Pacifica, and the Enlighten Award.

 

For those who prefer to read over watching the video, here is a full transcription:

On behalf of the team, we are just very humbled and very thrilled to receive this award from CAR and from Altair. It’s really a testament to the hard work and the effort that everybody put in to launch this product. Thank you.

It’s important for car companies to reduce weight for several reasons. We need to reduce weight to reduce emissions and increase fuel economy, and provide a better product to our customers. The 2017 Chrysler Pacifica was submitted for the Enlighten Award entry based on the fact that we’d achieved 113 kilogram vehicle weight reduction from the predecessor vehicle. From that we achieved 76 kilograms out of the body system alone and 60 kilograms from the body in white, using 72 percent advanced high-strength steel strategy.

So one of the enablers on the Pacifica development to balance the costs was to use tailor welded blanks, which enable us to combine multiple pieces of steel material into one blank assembly, reduce the waste from the stamping, and also use a high-strength material which helps improve performance. We also used a magnesium diecast liftgate inner panel which reduced the number of components in the liftgate assembly by 50%. That also helps to offset and reduce cost of that lightweight material.

I think the most innovative process that we applied on the Chrysler Pacifica was the way the team got together from a functional science point of view and simulation, as well as body design and program management to help balance weight and apply new tools and processes which ultimately enable us to meet our weight reduction goal. The processes that we pioneered to design and optimize the Chrysler Pacifica are now standard on all our future developments of the body in white at FCA US.

So the rapid constant development process that we pioneered on the Chrysler Pacifica is a way for us to develop multiple design concepts early in the design phase faster than a traditional approach. We combine advanced CAE tools, optimization, as well as multidisciplinary optimization, to understand the function and performance of every panel in the body structure and how we can possibly make it better. This ensures when we get to the concept approval phase that we have a design that meets its functional objectives at the lowest possible weight.

Some of the challenges that we faced with doing a parallel hybrid version of the Pacifica was where to put the battery and how to make sure that it remained safely protected in a side impact. So we had some innovations involved in the structural design to ensure we released a safe product for the customer.

Optimization techniques were a critical part in achieving the weight savings that we were able to achieve on the Chrysler Pacifica. The design process was based around developing new optimization tools and processes to apply on a full-body system level as well as on a component level. So we used optimization tools, like Altair’s OptiStruct, for optimization of the liftgate load paths as well as the full body in white load paths in the front cradle. This allowed us to identify the most efficient load paths where energy would flow through the body structure and then come up with the design to minimize the required material and allowed us to develop a body structure with the lightest possible weight.

An example where we used topology optimization to reduce weight on the Chrysler Pacifica was on the engine box. The Chrysler Pacifica was a minivan that has a hard-mounted, or integrated, front cradle for this part of the engine box. It’s not isolated like many other minivans. So we had to make sure we came up with the most efficient load paths to ensure we met the isolation requirements, as well as the impact and stiffness requirements of the vehicle. To do this, we employed topology optimization to ensure we had the most efficient design.

The main reason we look at mixed material in a vehicle design is to reduce weight, optimize stiffness, and optimize strengths for the vehicle performance objectives. Using only one material can either lead to a design that’s too light, not stiff enough, or not strong enough, or it’s too heavy, so our objective as engineers is to balance the requirements to come up with the right material strategy for the requirements of the customer. Looking around the industry, we’re starting to see vehicles move away from being heavily aluminum or heavily steel. And, especially, even the exotic vehicles are actually finding a balance in between steel and aluminum. That really is becoming a situation where we find the best material for the right application. In my opinion, the future of car design is going to involve using a balance of lighter materials as well as an intelligent integration of higher strength materials to reduce the weight of existing materials, such as steel. We’ll likely see further applications of aluminum especially on close-out panels and castings where it makes sense.

Some of the challenges that come along with the mixed material approach is how to assemble them in the body shop and how they respond to the heating in the paint ovens during the E-coat and the paint cure, so we have to make sure when we design these parts that the change in size due to thermal expansionis compensated for in the design.

I’m excited that we were able to work as a team to get such an exciting product out, and it’s really laid a really solid foundation for how we do all our future products moving forward. We’ve got some exciting launches coming up, I hope we get the chance to share more about the exciting engineering technology applied in those vehicles.

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