Question

Discuss briefly the three major steps in applying Finite Element Analysis in MCAE software such as IDEAS. b) Define "Socialware" and state three consequences of it on the engineering design process. c) Explain four engineering design attributes of a surgical scalpel.

Answer 1

a) Discuss briefly the three major steps in applying Finite Element Analysis in MCAE software such as IDEAS.

ANSWER: The three major steps in applying Finite Element Analysis are as the following

1. Pre-processing
2. Computation
3. Post-processing

  

1. Pre-processing: In the pre-processing phase the following decisions and actions are taken:

The geometry of the part is imported from the CAD model. Because solid models contain great detail, they often must be simplified by deleting small non-structural features and taking advantage of symmetry to reduce computation time. Make decisions concerning the division of the geometry into elements, often called meshing. The issue will knows which types of elements to use, linear, quadratic, or cubic interpolation functions, and building a mesh that will provide a solution with the needed accuracy and efficiency. Most FEA software provides a means for automatically meshing the geometry. The finite element mesh is applied in one of two ways: structured (mapped) mesh or unstructured (free) mesh. Structured meshes have a clear structure of triangles or quadrilateral elements (for 2-D) or tets or hexes (for 3-D) that are produced by rule-based mapping techniques. Grid points can be distributed along lines with effective spacing, and well-graded grids can be constructed. This approach is effective when the geometry is relatively simple. With complex geometries a multi block approach is used, in which the geometry is filled with an assemblage of meshed cubes. This requires the additional step of setting up the connections between the blocks. Unstructured meshing does not show structure in the placement of the elements. Determine how the structure is loaded and supported, or in a thermal problem determine the initial conditions of temperature. Make sure you understand the boundary conditions. It is important to incorporate sufficient restraints to displacement so that rigid body motion of the structure is prevented. Select the constitutive equation for describing the material (linear, nonlinear, etc.) that relates displacement to strain and then to stress.

2. Computation: The operations in this phase are performed by the FEA software.

The FEA program renumbers the nodes in the mesh to minimize computational resources by minimizing the size of the global stiffness matrix K.

It generates a stiffness matrix k for each element and assembles the elements together so that continuity is maintained to form the global or structural matrix K . Based on the load vector the software generates the external loads and applies displacement boundary conditions.

Then the computer solves the massive matrix equation for the displacement vector or whatever is the dependent variable in the problem.

3. Post-processing: These operations are also performed by the FEA software.

In a stress analysis problem, post processing takes the displacement vector and converts into strains, element by element, and then, with the appropriate constitutive equation, into a fi eld of stress values.

                                    A finite element solution could easily contain thousands of field values. Therefore, post processing operations are needed to interpret the numbers efficiently. Typically the geometry of the part is shown on which contours of constant stress have been plotted, Fig. 10.25.Mathematical operations may have to be performed on the data by the FEA software before it is displayed, such as determining the Von Mises effective stress. Increasingly, FEA software is being combined with an optimization package and used in iterative calculations to optimize a critical dimension or shape.

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b) Define “Socialware”? And state three consequences of it on the engineering design process.

ANSWER:

          Definition: Socialware the companies and their employees engage, communicate and collaborate with clients and one another.

1. Prestructered software engineering methodologies are replaced by flexible user centred software engineering design models which are parallel interactive engineering approaches.
2. Continuous attention to the technical excellence and good design.
3. Simplicityand effectivenes

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c) Explain four engineering design attributes of a surgical scalpel.

ANSWER:

A scalpel is a very sharp, thin knife which is normally thought of as a medical device used in surgery. There are also scalpels that are used in hobbies and crafts. Scalpels can be reusable or disposable, and their blades can be made from different materials and come in many shapes and sizes. The major attributes of a surgical scalpel are as follows:

1. Effectiveness-Flexibility:

A surgical scalpel’s effectiveness in design while being ambidextrous and autoclavable is important. The design of the device affords left handed or right handed medical personnel with the feel, weight and balance of the original metal unguarded scalpel, while maintaining safety through the shielding of the blade during non-use and the ability to dispose of the blade in a safe controlled manner without having to place ones hands near the unguarded sharp. Surgeons of either dexterity are able to learn and operate using similar techniques and instruments heretofore not available to them. No longer must a left handed surgeon be forced into the right handed world to perform surgery.

            

2. Cost: Cost is also one of the major attribute to consider while designing the product along with effectiveness.

3. Reusability: There are basically two types of scalpels in design either the scalpel is reusable and disposable.

4. Sharpness: It is the key attribute for the scalpel.

5. Size and Shape: The flexibility also depends and the size and shape of the scalpel.