# Blog

## Stress distribution analysis by static force using SolidWorks – Introduction

In engineering disciplines, stress and strain analysis is a method to determine the stresses and strains in material or structures under specific force. As we now in physics study, “stress” is physical quantity that express internal forces that neighboring particles of a continuous material exert on each other. You can imagine “stress” as intensity of force per unit area.

Above image is simple representation of cubical object that force is imposed to it, and stress is generated inside the object (shown using free body diagram, red arrows shows the internal forces, which per unit area is defined by stress).

We all know that was simple enough, since the object is simple, so the calculation is off course also simple. But in reality, the object could be non symmetrical, or even irregular shape. For example, a car engine block, car body, motorcycle frame, etc. Not only the shape of the object, also if the force exerted is complex, the calculation also become complex. This would be troublesome to calculate.

The possible way to calculate the stress over irregular shape or complex forces is to make simplification of the shape or the force. For example, you can make simple discrete objects (example : cube shape, prism shape, or spherical shape) to divide the complex object. Then, the calculation is made over that “simple discrete object” one by one, connecting the resulting force and stress so that it will represent the actual stress over the object. See below picture for easy imagine.

You can see that the “whole object” is divided into smaller part in prism shape which i called “simple discrete object”. This method is called “Finite Element Analysis (FEA)” in engineering world. If the small discrete object just a few, then manual calculation using hand and calculator is possible, but is realistic case, the small discrete object must be made so much so that the error is reduced and the result almost represent the actual stress. That is why computer aided design is very useful in engineering world.

Now lets talk about this method on SolidWorks. SolidWorks is one of popular CAD software among engineers. It has a lot of features, drawing 3D object, sketching 2D drawing, assembling parts, motion simulation of assembly object, and even fluid flow analysis, and stress and strain analysis, etc. Now we will only talk about stress and strain analysis. In this post, i made the title as stress distribution analysis by static forces. Yes, static. Since there is term static, there is also term dynamic forces. The difference is simply explained by below picture :

Picture on the left shows standing person holding books in his hands. This is represented as static force (since the book is in motionless, the load acting on the man hands is constant). Picture on the right shows walking person while holding books in his hands. This is represented as dynamic force (since the book is in motion, the load acting on the man hands is changing, or in the other word, not constant).

Now, you have the idea of how static force is. That idea will be implemented on object, and we will now use SolidWorks to assess the stress and strain phenomenon.

In SolidWorks, we called this analysis as “Linear Stress Analysis”, since the force acting on the object is static force. Linear stress analysis calculate the stresses and deformations of geometry given three basic assumption :

1. The part or assembly under load are deforms with small rotations and displacements
2. The product loading is static (ignores inertia) and constant over time
3. The material has constant stress strain relationship (Hooke’s Law)

As i explained earlier, SolidWorks simulation also uses Finite Element Analysis (FEA) to discretize component into smaller object, then uses linear stress analysis to determine the response of parts and assemblies due to the effect of :

1. Forces
2. Pressures
3. Accelerations
4. Temperatures
5. Contact between components

The special part using SolidWorks is that, this load can be imported from thermal, flow, and motion simulation studies to perform multiphysics analysis.

At first, before you start doing linear stress analysis on SolidWorks, you must prepare the component material data. The pros using SolidWorks, is that it contain various material database which you can apply on your design component. The database is also easily customizable to include your particular material requirements.

This is the example, result of linear static analysis using SolidWorks :

If you are interested more in this topic, wait for my next post, i will make step by step tutorial on how to draw, create part, and doing linear stress analysis using SolidWorks.

Thanks, have a great day 😉

## Brief Story of Computer Aided Design (CAD)

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Back then before the advent of CAD, the only source for draftsmen was pencil and paper for drawing sketches. And then, the story of CAD started around the mid 1970, as computer system began to provide more capability than just an ability to reproduce manual drafting with electronic drafting. Because of this, the cost benefit for companies to switch to CAD became apparent. But why? What is benefit of CAD compared to manual drafting? Perhaps this questions often comes to your mind. The benefits (using “s” means more than one benefit !) of CAD systems over manual drafting are; easy data storing and accessibility, ability to use 3D view, easy revision, faster speed and less time to create a drawing, drawing accuracy, automated generation of Bill of Material, auto layout in Integrated Circuits, Interference Checking, and many others.

Computer Aided Design (CAD) often use by engineer for many purposes, depend on the profession and type of software used. The features in the CAD system can be used for the variety of tools for measurement such as tensile strength, yield strength, electrical or electro-magnetic properties, and also its stress, strain, how the element gets affected in certain temperatures, etc. CAD is one part of the whole Digital Product Development (DPD) activity within the Product Lifecycle Management (PLM) processes, and as such is used together with other tools, which are either integrated modules or stand-alone products, such as :

• Computer Aided Engineering (CAE) and Finite Element Analysis (FEA)
• Computer Aided Manufacturing (CAM)
• Photorealistic Rendering and Motion Simulation
• Document management and revision control

There are several different types of CAD, each requiring the user to think differently of how to use them and design their virtual component in a different manner to reach. In short, there are two kinds of CAD, 2D design and 3D design. 2D design is the same as result in manual drafting. And then, there is 3D wireframe which is basically the extension of 2D design (3D design that consist of several lines that looks like wireframe structure) and not often used today. There is also 3D “dumb” solids, which is created in a way analogous to manipulations of real world objects. Basic three-dimensional geometric forms (prism, cylinder, sphere, and so on) have solid volume added or subtracted from them, as if assembling or cutting real world objects. This is not often used today. The last, there is 3D solid modelling which has two types:

1. Parametric Modelling, when the objects and features created are modifiable. Any future modifications can be made by changing how the original part was created.
2. Direct or Explicit Modelling, which provide the ability to edit geometry without a history tree. With direct modelling, once sketch is used to create geometry, the sketch is incorporated into the new geometry and the designer just modifies the geometry without needing the original sketch.

To create CAD design, there are several software that can be used, start from licensed and freeware. The choice depends on design purpose and features user want to use, since each software has its advantages and disadvantages. Below are major CAD applications for your choices, groped by usage statistics :

Commercial

Freeware and Open Source