Simulate Stamp, Welding and Product Assembly with ESI’s SYSWELD

Control and validate distortion tolerances, material characteristic and residual stress

ESI Group has sponsored this article and updated it March 27, 2020.

When optimizing a product, it’s easy to forget how the manufacturing process can
impact the design’s performance. Therefore, to properly optimize a product’s
design, engineers need to understand how that product will be manufactured and
assembled and how these processes might create unexpected distortions in the
final product.

“Virtual Prototyping enables design and process engineers to virtually
manufacture and assemble components long before their physical prototypes are
built and tested,” said Yannick Vincent, Solution Manager at ESI Group. “It
facilitates the creation of countermeasures to control distortions and residual
stresses in BIW welded assemblies. It also shortens time to market and minimizes
the cost of manufacturing planning, tryouts, and pre-production validation.”

ESI Group’s
Virtual Welding & Assembly Solution is a computer-aided engineering (CAE)
platform that studies the effects of stamping, welding, and assembly processes
on BIW assemblies distortions during product development. The solution helps
engineers to simulate and mitigate the residual stresses, distortions, and
defects by modeling the chained manufacturing process. 
“The goal is to ensure
the dimension accuracy of BIW assemblies throughout the product development
journey. You can identify the critical joints, perform virtual try-out of
different clamp locations, weld and clamp sequences optimization while
minimizing the cost and time for manufacturing planning and pre-production
validation” explained Saurabh Aggarwal, Manager of Market Strategy and Business
Development at ESI Group.

How Manufacturing Effects Add Dimensional Inaccuracies in BIW Assemblies

It can be a long, hard and expensive journey designing a product and its
production chain. Engineers will need to tweak the product and its production
process multiple times before residual stresses and distortions are controlled.

“During the stamping process, astification leads to material hardening and
thinning. Unloading also creates springback. These all lead to residual stresses
and distortions” explained Saurabh. “In the case of hot forming of steel alloys,
phase transformation takes place. All these effects have a significant influence
on the assembly behavior of parts during cold and hot joining processes in
welding and assembly body shops.”

“In other words, mechanical load and heat effects of the welded assembly process
modify material characteristics and introduce residual stresses, which leads to
dimensional inaccuracies in the welded assemblies,” clarified Saurabh.

Traditionally, these structural influences on the product were mitigated with
manufacturing and engineering gut-feeling modifications to the production
processes. However, this level of trial and error isn’t efficient or accurate.

“The optimization of the clamping tools without simulation is a very difficult
task— more clamps mean that more stresses are conserved in the structure, which
is completely contrary to the goal,” said Yannick. “The fewer clamps, the more
distortion develops, but the tolerances need to be kept. ESI’s Welding &
Assembly Solution helps process engineers find quickly the best compromise.”

CAE tools, like Welding & Assembly Solution, can iterate through fixes to the
production issues faster and without costly physical trials. This helps
engineers better predict and correct the deformations. Simulation makes it much
easier to sequence welds and pre-bend a clamped part so that the part will fit
within specification once the welding is completed.

How to Virtually Model a Production Process with ESI Group’s CAE Technology

First, engineers can use

ESI PAM-STAMP
to simulate the stamping of parts from thin metal sheets. The
output from the simulation tool is the plastic strain, stresses, and variable
thickness, along with the deformed mesh. This information and the post-stamping
deformation mesh are then imported into the ESI’s Welding & Assembly Solution.

“If you are in the pre-production stages when you already have the stamped
parts and doing the physical try-outs for assembly processes to control
distortions,” said Saurabh. “In such cases, you can also use the scanned
geometry of stamp parts to start the welding & assembly simulation.”

“Sometimes the distortions cannot be reduced as expected and parts have to be
compensated. In this case, design engineers must compensate for the deformed
shape on the welded assembly side because doing so on the stamping side would be
either very costly or highly impractical,” explained Saurabh.

 

ESI’s Welding & Assembly Solution simulates the stamping, prepositioning, holding and joining of parts. (Image courtesy of ESI Group)

Inheriting details of the “as manufactured” components from the press
shop, ESI SYSWELD simulates the entire assembly and welding process chain in
the body shop; step by step.

 (Image courtesy of ESI Group)

“ESI
SYSWELD imports the deformed mesh after stamping,” said Vincent. “Stamped
key data results, such as plastic strain, stresses, and variable thickness, are
mapped. Then, subsequent simulations for prepositioning, holding and joining are
performed. To chain simulations, key data and results must be transferred and
mapped from stamping to prepositioning to clamping and finally to the welding
simulation model. In order to reduce the time needed to perform such operations,
CAT (Control Adapt Transport) is available.”

ESI SYSWELD provides dedicated workflows to include every design feature of a
welding assembly process (pre-positioning, holding, and joining chained
manufacturing).

The prepositioning advisor helps engineers to define a reference point
system (RPS) by creating guides, locators, and fixtures/clamps. The advisor
defines how the clamps will close the gaps between the components before they
are joined. Engineers have access to various parameters that define the type,
shape, number position, offset and sequence of clamps. Engineers can tweak these
parameters until they are optimized to limit product stress and deformities.

“Finally, the user can export the deformed mesh, residual stresses and
plastic strain from stamping, prepositioning and holding processes to simulate
the welding operation with the defined weld properties,” said Vincent.
“Depending upon the case, seam (laser and arc welding) and spot-welding effects
can be taken into account.” This simulation determines the final distortions and
residual stresses from the chained stamping and welding & assembly processes.

After assessing the manufacturing of the product, the user can employ further
simulations to explore the product’s durability and performance in the field.

“In a nutshell, structural distortion, residual stress, plasticity behavior and
phase transformation of hot and cold joined assemblies are predicted during
chained manufacturing processes,” clarified Saurabh.

“The change of thermal, metallurgical and mechanical properties in a
structure during chained manufacturing is thoroughly analyzed and
countermeasures are taken to control the distortions and residual stresses,” he
added. “The benefits include reduced costs in both design and manufacturing as
physical prototyping and testing is dramatically reduced.”

For more information visit

https://www.esi-group.com/software-solutions/virtual-manufacturing/welding-assembly-simulation
  

 

Written by

Shawn Wasserman

For over 10 years, Shawn Wasserman has informed, inspired and engaged the engineering community through online content. As a senior writer at WTWH media, he produces branded content to help engineers streamline their operations via new tools, technologies and software. While a senior editor at Engineering.com, Shawn wrote stories about CAE, simulation, PLM, CAD, IoT, AI and more. During his time as the blog manager at Ansys, Shawn produced content featuring stories, tips, tricks and interesting use cases for CAE technologies. Shawn holds a master’s degree in Bioengineering from the University of Guelph and an undergraduate degree in Chemical Engineering from the University of Waterloo.