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Need of Linear Static Analysis

Most of the engineering problems are considered dynamic although we mainly focused on solving static problems analytically in undergraduate educations. However, the term of dynamic might be confusing sometimes for those who are interested in FE software solutions.

In engineering education, the term of dynamic is used to describe non-static situations where loading conditions change depending on time rather than its location. However, Ansys gives us flexibility to play with both location and magnitude of the loading conditions thanks to Transient Analysis.

Structural design, and assess structure to ensure that they are efficient and stable. Static analysis is a comprehensive determination to assure that the deformations due to load in a structure will be satisfactory and lower than the permissible limits, and failure of structure will never occur.

It is a method by which we find out how a structure or a member of a structure behaves when subjected to different loads. The results of the analysis are used to verify the structure’s strength for its uses.

The process to determine the response or behaviour of a structure under some specified loads or combinations of loads is known as static analysis. Analysis helps to find out support reactions, bending moment, rotation, stresses, strains, shear force, and deflection that, the particular member would undergo due to the application of different types of loads. Analysis of a structure involves its study from the viewpoint of its strength, stiffness, stability, and vibration.

Static analysis is an essential procedure to design a structure. Using static analysis, the structure's response to the applied external forces is obtained. Moreover, the static analysis is performed when the structure is subjected to external displacements, such as differential support settlements. The structure's response includes internal forces/moments and internal stresses that are used in the design process. In general, using a finite-element-based Static  analysis scheme, first, the unknown displacements are obtained from equilibrium equations of an active system and then, the external and internal forces and stresses are calculated from structure's global equilibrium equations.

Why to start with linear static analysis?

ü  Linear static analysis is the simplest simulation one can do

ü  It provides you a direct answer to the question “will my design fail?”

ü  It shows you if your product is over dimensioned

ü  To avoid failure by preventing stress concentration

ü  To retain a uniform stress distribution, elimination unnecessary parts and further strengthen necessary parts in order to produce an optimum design

What is Linear Static  Analysis?

A static structural analysis determines the displacements, stresses, strains, and forces in structures or components caused by loads that do not induce significant inertia and damping effects. Steady loading and response conditions are assumed; that is, the loads and the structure’s response are assumed to vary slowly with respect to time. A static structural load can be performed using the ANSYS, Samcef, or ABAQUS solver.

The types of loading that can be applied in a static analysis include:

• Externally applied forces and pressures
• Steady-state inertial forces (such as gravity or rotational velocity)
• Imposed (nonzero) displacements
• Temperatures (for thermal strain)

The simplest and most common Static Structural model can be solved with just the Isotropic Elasticity material model, which requires two property values: Young's Modulus and Poisson's Ratio. With those two values, you can calculate stress and deformation. This is only appropriate if the material you want to simulate is isotropic with linear elastic behavior. There are other material models for other behaviors such as hyperelasticity if you have a rubber material for example.

To evaluate if the stress has exceeded the linear elastic range of the material, you will need to know at least the Tensile Yield Strength. Strength values do not have to be put into the material definition since the calculation of stress and deformation is not affected by them being listed in the material.  If you do add the Tensile Yield Strength value to the material, it is used by the Stress Tool, a result that can include a Safety Factor (SF) plot, which just divides strength by stress so SF > 1 is good (stress below yield), SF < 1 is bad (stress above yield).

In other words, these features are used more static loading conditions which does not change for particular time and location.

ASSUMPTIONS

ü  The material behaves within the elastic region following the Hooke’s Law

ü  The deformation must be small enough to ignore changes in structural stiffness due to deformations

ü  The boundary conditions must not change while a load is being applied and the subsequent structural deformation is occurring

Ø  Loads do not vary in time

Ø  Inertial and damping forces are ignored

General FEA analysis will have 3 stages 1. Pre-processing 2. Solution Phase and 3. Post processing. In which, modeling, meshing, boundary conditions, loads, material details, element properties will come under pre-processing phase. According to the functionality usage of the product solution options are set, where physical scenario is changed to mathematical equations to know the required results. Post- processing is the phase in which, validation is made based on the applied loads and boundary conditions. Further, it also provides to know about various results such as displacement, stress, strength and durability based on analysis.

For demonstration purpose, a simple 3D chair Model was created, meshed, applied boundary conditions, loads and solution option settings are made for further process. The below figures show the load and boundary conditions application and the results of the chair i.e., displacement and stress plots to know the strength, factor of safety and durability of a structure.

https://gharpedia.com/blog/structural-analysis/