Hiring guide for LS-DYNA Engineers

LS-DYNA Developer Hiring Guide

LS-DYNA is a general-purpose finite element program capable of simulating complex real-world problems, developed by the Livermore Software Technology Corporation (LSTC). It was first released in 1976 as DYNA3D and later evolved into LS-DYNA in 1987. The software's fully implicit method makes it highly effective for solving static problems and dynamic response. Its applications range from automotive crashworthiness to metal forming, blast loading, and biomechanics. LSTC continues to develop LS-DYNA with new features that keep it at the forefront of simulation technology.

Ask the right questions secure the right LS-DYNA talent among an increasingly shrinking pool of talent.

First 20 minutes

General LS-DYNA app knowledge and experience

The first 20 minutes of the interview should seek to understand the candidate's general background in LS-DYNA application development, including their experience with various programming languages, databases, and their approach to designing scalable and maintainable systems.

How would you define a finite element in LS-DYNA?
A finite element in LS-DYNA is a discrete representation of a continuous body. It is a small, simple shape to which physical properties can be assigned, and it is used to discretize a larger, more complex body for analysis.
What are the key features of LS-DYNA?
Key features of LS-DYNA include capabilities for explicit and implicit computation, multiphysics simulation, fluid-structure interaction, and coupled thermal-mechanical analysis. It also supports a wide range of element formulations and material models.
Describe the difference between explicit and implicit analysis in LS-DYNA.
Explicit analysis is a time-domain method suitable for short-duration, high-speed events like impacts or blasts. It uses small time steps for solution accuracy. Implicit analysis is a frequency-domain method suitable for static or quasi-static events like bending or buckling. It uses large time steps for computational efficiency.
How would you handle contact definitions in LS-DYNA?
Contact definitions in LS-DYNA are handled by assigning contact types between bodies or parts. These types include single surface, node-to-surface, surface-to-surface, automatic single surface, and automatic general contact. The appropriate type depends on the specific interaction being modeled.
What are the common sources of error in an LS-DYNA simulation?
Common sources of error in an LS-DYNA simulation include inappropriate element formulation, incorrect material model, inaccurate boundary conditions, improper contact definition, and insufficient mesh quality or density.
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What you’re looking for early on

Has the candidate shown a strong understanding of LS-DYNA software?
What level of experience does the candidate have with finite element analysis?
Is the candidate able to demonstrate problem-solving skills?
Does the candidate possess strong programming skills, particularly in languages such as C++ or Python?

Next 20 minutes

Specific LS-DYNA development questions

The next 20 minutes of the interview should focus on the candidate's expertise with specific backend frameworks, their understanding of RESTful APIs, and their experience in handling data storage and retrieval efficiently.

Describe the difference between Lagrangian and Eulerian formulations in LS-DYNA.
Lagrangian formulation follows individual material particles through time, making it suitable for solid mechanics problems. Eulerian formulation fixes the computational grid in space, making it suitable for fluid dynamics problems. LS-DYNA allows for coupled Lagrangian-Eulerian analysis.
How would you optimize the performance of an LS-DYNA simulation?
Performance of an LS-DYNA simulation can be optimized by improving mesh quality, reducing model complexity, choosing appropriate element formulations and material models, using parallel processing, and tuning solver parameters.
What are the considerations when defining a material model in LS-DYNA?
When defining a material model in LS-DYNA, one must consider the material's mechanical behavior under various loading conditions, its failure criteria, its strain-rate dependency, and its thermal properties if relevant. The choice of model should be validated with experimental data.
Describe the difference between static and dynamic analysis in LS-DYNA.
Static analysis in LS-DYNA assumes that loads are applied slowly and do not change with time, allowing for equilibrium solutions. Dynamic analysis assumes that loads can vary with time, requiring the solution of motion equations.
How would you model a fluid-structure interaction in LS-DYNA?
A fluid-structure interaction in LS-DYNA can be modeled using coupled Lagrangian-Eulerian analysis, where the structure is modeled with Lagrangian elements and the fluid with Eulerian elements. The interaction between them is handled by a special contact algorithm.
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The ideal back-end app developer

What you’re looking to see on the LS-DYNA engineer at this point.

At this point, a skilled LS-DYNA engineer should demonstrate strong problem-solving abilities, proficiency in LS-DYNA programming language, and knowledge of software development methodologies. Red flags include lack of hands-on experience, inability to articulate complex concepts, or unfamiliarity with standard coding practices.

Digging deeper

Code questions

These will help you see the candidate's real-world development capabilities with LS-DYNA.

What does the following LS-DYNA code do?
This code represents an empty contact definition in an LS-DYNA input file. It starts with the *KEYWORD directive, which is mandatory in any LS-DYNA input file. Then it has a *CONTACT keyword with no parameters, indicating an empty contact definition. The *END keyword indicates the end of the input data.
What will be the output of the following LS-DYNA code?
This code represents an empty material definition in an LS-DYNA input file. It starts with the *KEYWORD directive, which is mandatory in any LS-DYNA input file. Then it has a *MAT keyword with no parameters, indicating an empty material definition. The *END keyword indicates the end of the input data.
What does the following LS-DYNA code do?
This code defines two nodes in an LS-DYNA input file. The *NODE keyword is followed by the node ID and its coordinates. The first node with ID 1 is at the origin (0.0, 0.0, 0.0) and the second node with ID 2 is at (1.0, 0.0, 0.0).
What does the following LS-DYNA code do?
This code defines a shell section in an LS-DYNA input file. The *SECTION_SHELL keyword is followed by the section ID, the material ID, and the thickness of the shell. Here, the section with ID 1 is assigned the material with ID 1 and has a thickness of 0.01.

Wrap-up questions

Final candidate for LS-DYNA Developer role questions

The final few questions should evaluate the candidate's teamwork, communication, and problem-solving skills. Additionally, assess their knowledge of microservices architecture, serverless computing, and how they handle LS-DYNA application deployments. Inquire about their experience in handling system failures and their approach to debugging and troubleshooting.

What are the challenges in simulating high-speed impact events in LS-DYNA?
Simulating high-speed impact events in LS-DYNA is challenging due to the need for accurate material models that can handle large strains, high strain rates, and failure. Also, the model must be adequately refined near the impact zone to capture the rapid changes in stress and strain.
Describe the difference between node-based and element-based hourglass control in LS-DYNA.
Node-based hourglass control in LS-DYNA uses extra forces at the nodes to resist hourglass modes, while element-based hourglass control uses extra internal energy in the elements. The former is more robust but less accurate, while the latter is more accurate but less robust.
How would you validate the results of an LS-DYNA simulation?
The results of an LS-DYNA simulation can be validated by comparing them with experimental data or analytical solutions, checking for energy balance, examining the convergence with mesh refinement, and ensuring the physical plausibility of the results.

LS-DYNA application related

Product Perfect's LS-DYNA development capabilities

Beyond hiring for your LS-DYNA engineering team, you may be in the market for additional help. Product Perfect provides seasoned expertise in LS-DYNA projects, and can engage in multiple capacities.