Many engineering teams trust their simulation results without questioning whether the study type was correct. In practice, this is one of the most common reasons designs fail late in the process, leading to costly rework and delays.

With so many study options available, designers, both new and experienced, often struggle to understand why their manual calculations differ from simulated results. Although there are various factors to consider, the first step in any simulation is choosing the correct study option for your design and required results.

But why does choosing the correct study matter?

First, consider the cost of trusting an incorrect simulation. Running a linear static analysis when your design actually behaves nonlinearly can lead to design failure and costly redesigns. On the other hand, running a complex nonlinear simulation for hours when you only require results in the linear region wastes valuable time.

As a Mechanical/Applications Engineer specialising in SOLIDWORKS Simulation at MECAD Systems, I have worked with clients across various industries, discussing simulation best practices through technical support, training, webinars and demonstrations. During these discussions, I have seen how a minor misunderstanding at the start of a simulation can propagate throughout the setup, leading to inaccurate or completely incorrect results.

In this article, we will explore why choosing the correct study and understanding material behaviour is crucial for any designer, covering:

• What a material yield point is
• The difference between linear and nonlinear studies
• When to use linear static, frequency and thermal studies
• When a linear analysis is no longer sufficient

Why Choosing the Wrong Study Costs You Time and Money

Before deciding which study is appropriate, it is important to understand basic material behaviour. Think about a thin steel wire. If you pull it at one end, it stretches slightly and then returns to its original shape. If you continue pulling, it begins to stretch permanently and remains deformed even after the force applied has stopped. With enough force, it will eventually break.

The material yield point is the stress level at which the material begins to plastically deform. In simple terms, this is the point where the material will not return to its original shape once the applied force is removed.

To fully understand this, refer to the below stress-strain graph for a ductile material.

The material behaves linearly up to the yield point. Young’s modulus, or elastic modulus, can be calculated within this region. Once the stress increases beyond the yield point, the material can no longer be approximated as linear, as strain hardening begins.

We can therefore conclude that beyond the yield point, a linear study is no longer accurate, and a nonlinear study is required.

Understanding Material Behaviour: Where Linear Breaks Down

Now that we understand ductile material behaviour in relation to the yield point, we can examine the differences between linear and nonlinear studies in SOLIDWORKS Simulation.

A manufacturer in Gauteng was preparing a design for production where even minor deformation was considered failure. Their initial nonlinear study added unnecessary complexity and long solve times. After reviewing the requirements, we confirmed that a linear static study was sufficient, reducing simulation time significantly while still ensuring reliable results.

In contrast, an engineer in the rubber industry may require the maximum extension of a rubber pipe and a detailed stress analysis during stretching. In this case, a nonlinear study is required because rubber exhibits nonlinear elastic behaviour.

A linear static study is suitable when the following assumptions apply:

• Loads are applied slowly and gradually
• Loads remain constant after reaching full magnitude
• Inertial and damping forces are negligible
• Loads and the response of the model to the loads are linear
• All materials behave linearly
• Structural deformations are small

In practice, many real-world designs violate at least one of these assumptions, which is where engineers unknowingly introduce risk into their simulation results. If any of these assumptions are not valid, a dynamic nonlinear study should be considered.

Linear vs Nonlinear: What Actually Changes in Practice

Choosing the right study depends on the results you need and the type of loading applied.

The following table lists common questions you might have asked before running a study and scenarios where the study is no longer recommended for your analysis.

When Linear Studies Are Enough (and When They Are Not)

In summary, a linear analysis is no longer sufficient when:

• Displacements are large
• The material exceeds the elastic limit or reaches the yield point

In SOLIDWORKS Simulation, a Linear Static study should only be used if the Factor of Safety remains within the elastic region of the stress-strain curve.

The Bottom Line

To prevent costly redesigns and avoid unnecessarily complex simulations, the first step in any simulation is choosing the correct study type.

Once your model reaches its yield limit, a nonlinear analysis is required for accurate results.

A practical approach is to:

• Identify how your model could fail
• Understand the type of loading applied
• Determine whether behaviour remains within the elastic region

Choosing the right simulation study from the outset, based on material behaviour and loading conditions, is essential to achieving accurate results while minimising both time and cost.

In practice, the most effective approach is to start simple, validate assumptions, and only introduce complexity when required.

If there is uncertainty around material behaviour or loading conditions, it is always worth validating your study setup before trusting the results, as this is often where the biggest errors occur. If you are unsure whether your current simulation approach is appropriate, a quick review can often prevent hours of rework later in the process.