# Analysis and Optimization in Design

## Types of analysis in engineering design

There are numerous types of analysis that you can use in the embodiment design, depending on the nature of the designed project and customer’s requirements. An important role in the efficiency and accuracy of a design project belongs to static and dynamic analysis of the product.

Static analysis considers the effects of constant loading on a system, while ignoring inertial and damping effects, as well as time-varying loads. However, steady inertia loads such as gravity and rotational velocity can be included in static analysis. Dynamic analysis is used to define the vibration characteristics (natural frequencies and mode shapes) of a product being designed. The main tool for these types of analysis is the FEA – Finite Elements Analysis.

Few examples of different types of the engineering analysis are presented in this section.

• ### Stress, strain, and displacement

Finite element analysis allows to reduce stress concentrations. Knowing the results of stress distribution simulation, you can redesign critical sections, for example, add fillets to avoid stress concentrations in sharp corners. In the following figure displacement, strain and Von Mises stress distributions in the part are shown. Using FEA for such analysis ensures that in the final design the maximum yield strength is not exceeded which will prevent permanent deformation and ensure that all deformations are elastic.

Finite Element Analysis of a part for a) displacement, b) strain and c) von Mises stress

• ### Vibration analysis

There are many major sources of vibrations that may occur in a system. Some frequencies, that are called natural, are intrinsic to all objects, others may appear due to specific peculiarities of an object, e.g., whirling. Various vibration causes can be addressed during mechanical design, others require proper selection of components and operating modes.

Probably, the most important type of vibrations is the resonant vibration that depends on the system’s natural frequency.

The spring-mass system has only one natural frequency. Two-mass system has two natural frequencies, and so on. The more masses the system has, the more natural frequencies it has, and resonance in a system may occur at any of its natural frequencies. To prevent system vibration, you must ensure that all its natural frequencies are much greater than the expected frequency of acting forces. For a vibration isolation platform, it is better to make its natural frequency much lower than the vibration frequency transferred by the floor on which the platform stands.

• ### Thermal analysis

Another widely used type of analysis is thermal, for example, for the evaluation of thermal performance of the battery module of an electric vehicle. In the figure, result of the thermal simulations conducted using SolidWorks is presented. Here the ambient air temperature surrounding the battery module is set to –20°C. The simulation results show temperature distribution throughout the cells at fixed ambient air temperature, and the maximum temperature difference throughout the stacked cells is defined as approximately 17°C.

Thermal analysis diagram

These figures illustrate only FEA, however, the variety of possible types of analysis in the embodiment design phase is huge and for each project is limited only by the nature of the designed product.

• ### Fatigue analysis

Fatigue is a process of the cycle-by-cycle accumulation of damage in a material undergoing fluctuating stresses and strains. Fatigue failure is characterized by the two stages: the fatigue crack initiation that starts from the surface of a component, where fatigue damage begins as shear cracks; the crack growth in a direction normal to the applied stress.

• ### Computational fluid dynamics analysis

Computational Fluid Dynamics (CFD) is the analysis of fluid flows using numerical solution methods. With the help of CFD, you can analyze complex problems related to fluid-fluid, fluid-solid and fluid-gas interaction. CFD analyses are frequently used in aerodynamics and hydrodynamics, where lift and drag, or pressures and velocities are required. Fluid dynamics transforms physical laws to the form of partial differential equations, and CFD solvers further transform them into algebraical equations. The latter then are solved numerically.

• ### Load case analysis

The analysis in specific applications can vary from resource consuming simulations involving multiple parameters, complicated mathematical methods, and compound techniques, to simplified methods carried out with standard excel-based algorithms. A fragment of the excel file with load case analysis of a vehicle is shown here.

Excel file fragment with load cases analysis

## Optimization in Engineering Design

Optimization is often used during engineering design process. It is a systematic process that uses design constraints and criteria to allow finding an optimal solution. A wide range of optimization techniques and methods is available for researchers and designers, and they are selected in accordance with the nature of the optimization tasks, applications involved, and designer's expertise. Therefore, despite the importance of optimization for the engineering design, introduction of various optimization techniques is not the scope of this web site, and you can find multiple resources for the optimization methods elsewhere.