LS-DYNA: Implicit Quick-Start for Explicit Simulation Engineers

This is the 5th in a series of informal articles about one engineer’s usage of LS-DYNA to solve a variety of non-crash simulation problems. The first was on LS-DYNA: Observations on Implicit Analysis, the second was on LS-DYNA: Observations on Composite Modeling, the third was LS-DYNA: Observations on Explicit Meshing, and the fourth was LS-DYNA: Observations on Material Modeling

Most FEA work in the world is dominated by linear elastic stress and vibration analysis (implicit). The complexity varies tremendously within this realm and can be every bit as challenging as a highly nonlinear transient model (explicit). In the linear world, stress values are very sensitive to small changes in strain, and often take on even greater importance, since their values are used to verify the design margin of a structure or its fatigue life. Since the mission statements and analysis requirements between implicit and explicit analyses are different, one has to shift gears to move from one to the other. It is the focus of this short note to point out how a journeyman explicit simulation engineer can quickly and efficiently create implicit analyses from linear to nonlinear.

Where do I really start?

LS-DYNA Blast Analysis of Large Generator Housings

For more than 15 years, LS-DYNA FEA consulting services have been an integral part of Predictive Engineering. In a recent project, we investigated the blast resistance of several large generator housings. The blast pulse was determined by ConWep calculations given the TNT charges and distances from the housings.

Although LS-DYNA has several built-in methods for simulating blast loading (e.g., *LOAD_BLAST_ENHANCED and *PARTICLE_BLAST), most far-field air blast load calculations of exposed structures can be done as shown in the graphics below. Results from this investigation allowed our client to decrease the weight of their design to such an extent that analysis costs were easily recovered, and that the housings would meet all infrastructure protection requirements at the base. 

LS-DYNA Blast Analysis of Large Generator Housings 01

LS-DYNA Blast Analysis of Large Generator Housings 02

Trip & Training Recap: Houston, Lockheed Martin, and BBQ

BBQ in HoustonThe weather was hot and muggy as Tropical Storm Cindy floated past Houston but fortunately, the power stayed on and the FEMAP and NX Nastran training class went off without a hitch. Ten analysts from Lockheed Martin’s Orion program participated in the training and worked through real-world examples from CAD geometry to full Global-Local models.

The engineers have honed their Nastran skills working on the Orion Multi-Purpose Crew Vehicle and now have the FEMAP pre and post processing techniques to liberate them from the dreaded text editing and manual meshing.

I’d like to thank the class for their challenging questions and in-depth discussion of finite element modeling and analysis. To expand your own FEMAP and NX Nastran skills, visit us in Portland, Oregon for our next training on October 9th 2017.



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