This presentation was made at the NAFEMS Americas Seminar - Confidence in Engineering Simulation: The Next 10 Years of CAE in Mexico.
What is the future for engineering analysis and simulation in Mexico? Discover innovative engineering simulation processes and tools which are helping companies in Mexico improve production capabilities. Engage with domain experts, industry leaders, and peers in a focused, comprehensive one-day event that covers topics on engineering analysis, simulation, and systems modeling and simulation that every engineer in Mexico should know.
Using rivets to join work pieces (or plates) together is still very popular in automotive industry, due to its easy setup, low cost in capital investment. A riveted assembly is completed when a pre-formed rivet is upset on its tail with to-be-joined plates being securely sandwiched in between.
Although upsetting the rivet has been used for very long time in production lines, Numerically simulating its behavior has not been brought about until recently because of many challenges involved. One of challenges is that the rivet material is severely undergoing large plastic deformation as the tail of rivet quickly flows to be shaped into a rivet head.
Presented in this work will be a riveting simulation with the use of an explicit finite element code generally available in the market. The model for the simulation is 3D-based in order to make it more versatile in a variety of riveted assembly.
Rather than a single rivet to join multiple plates face-to-face (without any intentional gaps), a spacer-type rivet will be used, as an example in this simulation, to joint four plates with 2 inner plates being spaced at a given distance. Thus, instead of upsetting each rivet tail to form two heads one by one, we have simulated a single process such that two shop heads are formed simultaneously to cut the production time by more than half. Basically, as the moving press head pushes one tail of rivet with the other being supported on the stationary base, both rivet heads are actually formed. The rivet shanks at both end do not have to be equal in diameter or length to be able to form typical heads, even though the forces applied at the one tail must be equal to the force reacted at the other. The blind holes at the center of shanks are found to be effective in tuning both rivet heads to their desired sizes, as will be demonstrated in this simulation work.
The required force to upset a rivet joint can be easily available as the result of simulation, which certainly becomes a important piece of info for planning in manufacturing plant. By the means of simulation, we can easily and quickly assess the amount of material filling the radial gap originally existing between the shank and hole. There is no question that the stress and strain state on the rivet and the work pieces (or plates) can be displayed to identify the potential troublesome areas susceptible for cracks during the riveting. More importantly, the stress that remains within a rivet or work piece, or residual stress, is very vital for their continued capability to handle service loads, once the joined assembly is put in service.
In short, virtual riveting through simulation can be an important arena of FEA simulation to make our simulation more valuable to product/process design and integration.
|Date||8th November 2018|
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