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FEA: Static and Dynamic Analysis of Mechanical Parts

The Static and Dynamic analysis of mechanical parts plays a very important role for the efficiency and precision of the work performed by any engineer, including product development engineers, QA engineers, reliability engineers, design engineers, among others.

These type of analyses are performed with the purpose of estimating the behavior of the mechanical parts under specific operational conditions.

In the past, these analyses were performed through tests that were carried out on prototypes of the product, which meant an increase on the time needed to develop the product, as well as an increase on the related costs.

However, technological advancements have allowed developers and engineers to depend upon computational tools to carry out these tests virtually via the Finite Elements Method (FEM), which is also referred to as Finite Element Analysis (FEA).

FEM is a numerical method that provides the ability to solve complex problems through mathematical models that can be represented by means of differential equations.

At present, CAD/CAE systems have modules to perform the analyses described above. Among the most commonly used, there are:

  • Solidworks Simulation
  • Autodesk NASTRAN In-CAD
  • ANSYS
  • ABAQUS
  • FEMAP with NX NASTRAN, MSC NASTRAN etc

Static Analysis of Mechanical Parts

The static analysis of mechanical parts is intended to calculate the effects of constant loads on the structure ignoring the effects of inertia and shock that are commonly found when the applied loads change rapidly.

Nevertheless, a static analysis may include constant inertia loads such as gravity, as well as loads that vary with time but which can be approximated to a static equivalent, as is the case of loads resulting from the wind which are defined by construction codes.

Some of the most common static analyses are:

  • Linear stress analysis. This analysis allows engineers to validate the quality, performance and the safety of the design in a very efficient and accurate way. In this static analysis, the stress and displacement experienced by the geometry are calculated. In addition, this calculation helps to determine how the part will react to the effect of different forces, temperature and the contact between different components.
  • Deformation analysis. Likewise, this analysis allows designers to verify the quality, performance and the safety of the mechanical part, in this case based on the geometrical changes that can be noticed when specific load conditions are established.
  • Thermal analysis. In this analysis, the engineer is able to study how the part would react to the possible temperature variations it may experience during operation. In this case, the thermal expansion coefficient of the material plays an important role, as it will determine how much deformation, if any, will occur on the part due to temperature changes.

Also, it is important to highlight the fact that static analyses help to determine different mechanical properties of the part, such as hardness requirements, traction resistance, compression resistance, shear resistance, sag resistance and torsion resistance.

Forced Response Fatigue Optimization
Performed for Fresco NZ Ltd.

Dynamic Analysis on Mechanical Parts

The dynamic analysis of mechanical parts is the study of the dynamic properties of the structures under vibrational excitation. It can be used to determine the vibrational characteristics of the part, such as natural frequencies, to evaluate the impact of the transient loads or to avoid noise and vibration problems with the design.

Performing this kind of analysis during the design stage can prevent or reduce the need and the costs of trials on test benches. Moreover, the failures under dynamic loads can be dramatic, so significant, costly errors, as well as the loss of brand reputation can be avoided.

Among the most common dynamic analyses, we can find:

  • Modal analysis. This analysis is used to determine the natural frequencies of the part. It allows the engineer to develop the product with the certainty that the operational vibrations will never match the natural frequencies, with the intention to eliminate or, at least, minimize excessive vibrations that may result in critical failure.
  • Harmonic response analysis. A follow on from modal analysis, harmonic analysis allows the evaluation of the part response to actual expected dynamic loads. E.g. stress, deflection and fatigue life of a part can be predicted based on dynamic loading.
  • Transient dynamic analysis. In this analysis, the engineer can determine the response of the part due to loads that are a function of the time – similar to harmonic response except the loading can be non-periodic. It is commonly applied under conditions related to seismic or shock events.

In conclusion, static and dynamic finite element analysis can be used to “virtually prototype” designs before they are built, reducing risk, costs and speeding up time to market.

Motovated's Leon Daly

Leon Daly                                  General Manager                      Motovated Design & Analysis