Cu s t o m e r Sp o t l i g h t

Packaged for Freshness with Realistic Simulation Simulation of material and fluids with Abaqus FEA helps decrease development time while improving quality of innovative aseptic packaging

At the turn of this century, many experts Manager, Virtual Engineering at Tetra Pak. tube, above the folding system, reduces the compiled “Top-ten” lists for the greatest “That requires an in-depth knowledge of the amount of backflow up the tube. But the record-setting athletic performances, the loads and forces involved—both liquid and packaging tube is subject to deformation best all-time songs, the top news stories, material.” under folding and considerable changes and many other social achievements of the in fluid pressure, and it needs to retain its previous hundred years. The Number One , Fluids, and Forces structural integrity without breaking or food science innovation of the twentieth Both for cost and for control, the packaging crimping. century selected by the Institute of Food process is designed to be as simple as Technologists — ahead of even concentrated possible. But keeping it simple poses “When designing new package shapes and juices, safe , and freeze drying — tremendous engineering challenges. A sizes,” Olsson says, “or when modifying was and packaging. continuous reel of -based packing the filling machine—for instance by material—a composite of mostly paper, increasing the filling speed—the folding Aseptic processing dates from the early with some ultra thin layers of plastic and and forming of the package are critical. 1960s. It involves ultra-high-temperature aluminum—is fed into the top of a filling In the past, these have been difficult to (UHT) treatment of milk and other liquid machine and sterilized along the way. The predict.” Customarily, the packaging and foods for a few seconds in order to remove flat packaging material is formed into a tube filling process was verified by physical all harmful micro-organisms while and sealed longitudinally. A pipe from the testing on a nearly finalized machine. But preserving nutrients and flavor compounds filling machine enters the top of this packing if the test revealed design problems at that better than traditional pasteurization and material tube, filling it with liquid and stage, it was more expensive to introduce canning done at lower temperatures for causing it to expand. A mechanical system changes than it would have been earlier in longer times. The result is that UHT food folds and transversely seals the package, product development. “What we needed,” products remain fresh for months during below the surface of the fluid, keeping it Olsson points out, “was a realistic, reliable shipping or storage without requiring sterile while forming it into the desired simulation method that took into account the refrigeration or preservatives. This provides shape. The tube is then cut into individual liquid, the packaging material, and all the significant cost savings to everyone—from packages. major forces acting—and interacting—on the producer to the consumer—as well as them.” long-life, healthy nourishment in developing The packaging material So Tetra Pak selected Abaqus finite element countries lacking adequate power grids, cold The packaging is formed into a tube material analysis software from SIMULIA, the chains or transportation infrastructure. is sterilized Dassault Systèmes brand for realistic The tube is filled Tetra Pak is the ’s largest supplier of with the product simulation, to evaluate the complexities aseptic packaging. Its founder, Dr. Ruben of its packaging process. The company Rausing, began the company in , had previously used Abaqus for structural

Sweden in 1951 with a simple tenet: “A The tube is shaped and analyses, but this was the first time that cut into individual package should save more than it costs.” packages Tetra Pak engineers simulated the dynamics Rausing invented the packaging technology of the fluid-structure interaction during that still forms the basis for much of Tetra Reel of packaging. The resulting analysis generated packaging Pak’s business. Currently the company material a greater understanding of the packaging distributes more than 387 million packages process and provided a means to model it per day in over 150 countries, for a total of Schematic of a filling and packaging system for an earlier in the design stage. “We anticipate more than 141 billion delivered worldwide aseptic liquid container. that use of simulation will help save us a in 2008. significant amount of product development Even though the process is simple, the time,” says Olsson. As the company is committed to providing forces it is subject to are not. “Gravity the lowest-cost packages possible, every is driving the liquid down,” Olsson says, A Model Packaging Process new product line presents a challenge: “but the folding and the tube deformation For their initial trial analysis, the engineers is the thin, lightweight material strong are forcing it backward”—much like the selected the Tetra Fino Aseptic 500 ml, TFA enough to withstand the filling and sealing action of putting a kink in a garden hose. 500s milk package—the mid-range size of process? “Complete control over the process A pressure flange (essentially a flat disk an extremely low-cost and high-volume is paramount,” says Dr. Mattias Olsson, with small holes in it) mounted inside the product line. “We already had a strong

10 INSIGHTS January/February 2010 www.simulia.com Packaging material tube

Inlet system

knowledge of production parameters for this Because the packaging process is Floater application,” Olsson says, “so it made an axially symmetric, the engineers were Pressure flange excellent choice for our initial analysis.” Dr. able to model one-half of the system to Anders Magnusson, Technology Specialist substantially reduce processing time. The at Tetra Pak, worked with Olsson on the model involved roughly 220,000 elements, simulation. with approximately 700,000 variables. The Folding system analysis ran on a Linux 86-64 platform with There were a number of challenges to an Intel Xeon Dual core processor, with modeling the process. The packaging the runs taking about 24 hours on 8 to16 material was very thin and flexible, which processors. made for large deformations under pressure changes. The cross-section of the tube Once the Coupled Eulerian-Lagrangian

rapidly changed from circular cross-section approach enabled the simulation to capture Half symmetry model of the structural components to fully closed when folded. Most important, the deformation of the packaging material, of packaging system. there was a strong fluid-structure interaction the behavior of the fluid and the interaction to be modeled that had to take into account between them entirely within a single FEA the changing pressure waves in the fluid and model, the engineers were able to model and their effects on the packaging material. define a variety of design parameters: The model for analysis included the • Sequencing the folding system action, following components: including the deformation of the material • The composite packaging material (a • Determining the choice and suitability of paper, aluminum and plastic carton tube, the packaging material modeled as a homogenous material) • Establishing the correlation between • The packaged fluid, including its flow fluid injection rate and formed packaging and pressure properties volume • The flotation device that rests on top of • Defining the tensile load applied to the the fluid surface material so as to prevent breakage or crimping • The system that folds the packaging material “We were trying to model all the aspects of packaging that we had tested in physical • The pressure flange that controls prototyping,” Magnusson says. “In the end, (dampens) pressure waves inside the tube we were able to simulate all the important With the exception of the deformable forces of the process, from flow under Deformation of the packaging tube packaging-material tube and the liquid, gravity and pressure changes in the liquid, as the packaging seals. the components were modeled as rigid to deformation in the material.” bodies. These structural items were modeled in a Lagrangian framework, which is a The Results—Good to Go In the long run, the Abaqus simulation will commonly used method of simplifying The FEA analysis realistically captured the aid Tetra Pak as it develops new packages the application of forces to objects and packaging process, right down to arriving and upgrades existing machines. Using quantifying their reactions. at the desired final shape of the filled and simulation early in design is expected sealed package. It also demonstrated that to decrease the development time of the The flexible packaging material was including the interaction of the fluid and packaging processes while increasing modeled with shell elements calibrated to the packaging material in the simulation is package quality—an important goal for represent the laminated material as though imperative in order to calculate the degree a packaging company whose motto is it were homogenous, which reduced the of package deformation during filling and “Protects What’s Good,” and that strives computation time for the analysis. sealing. The simulation showed the need to provide healthy and nutritious food throughout the world. The fluid was modeled using an Eulerian and effectiveness of the pressure flange device to control the gross bulk motion of approach that captures the characteristics “Tetra Pak’s vision is that we commit to the fluid, reducing the dynamic interaction of non-viscous fluid flow. By coupling this making food safe and available everywhere,” between the fluid and the tube of packaging with the Lagrangian approach, Tetra Pak’s says Olsson. “This FEA analysis is a part material. “Originally it was believed that engineers could now model the interaction of that vision, and it has significantly modeling the role of the pressure flange of the packaging tube and the fluid in one strengthened our understanding and would be difficult using the Coupled analysis. “The Coupled Eulerian-Lagrangian knowledge of the physics at play in our Eulerian-Lagrangian method, since physical capability in Abaqus allowed us to include packaging systems. SIMULIA will be tests had demonstrated turbulence effects,” effects from the packaging dynamics—tube important to our process development Olsson observes. “But our analyses, with deformation under flow and pressure method going forward.” changes—that we had never simulated and without the flange, proved that this method could capture the fluid behavior in a single model before,” Magnusson For More Information well.” The next step is to verify the results says. Abaqus’ strong contact and nonlinear www.tetrapak.com with physical testing. capabilities were also essential to the www.simulia.com/cust_ref analysis. www.simulia.com INSIGHTS January/February 2010 11