| | Traditional Engineering
Tried and true methods using manual and spread sheet calculation. This is the basis for all other engineering approaches and can be the most economical approach. Every problem does not require extensive computer modeling for a reasonable solution. However, these methods do not easily account for the complex interactions equipment and processes experience or allow for detailed analyses. These methods can be automated using spreadsheets, computer programming, or equation-based math programs and solving packages. | |
| | Code Software
Many technical groups such as ASME (American Society of Mechanical Engineers), SAE (Society of Automotive Engineers), and API (American Petroleum Institute) as well as governmental have developed specific standards, guidelines, data tables, and required calculations for a given equipment item or application. Code software automates this process, allowing for rapid solution of standard design and analysis requirements. These software packages are usually very specific and are of limited use for failure analysis, troubleshooting, and nonstandard designs. Other software packages can provide the entire code, including drawings and equations, on CD-ROM with complete searching features. This helps the designer to ensure no citations or references are missed. | |
| | Pipe Stress Analysis
The evaluation of piping systems and the interaction between piping, their components, and the various temperatures and pressures the system will experience. Today this type of analysis is usually done using pipe stress software, combining aspects of code software and Finite Element Analysis to provide rapid modeling and solving of the stresses induced in a piping system. Go To Top | |
| | Finite Element Analysis (FEA)
A computational method used to model mechanical response to various conditions, including force, moment, pressure, vibration, temperature, radiation, heat flux, EMF, and deflection. Highly complex geometries with a variety of materials, including composites, can be modeled in detail and analyzed for a combination of applied loads. The results can show the stresses, temperatures, heat transfer, deflections, and other responses. For example, a pressure vessel or turbine in critical service could be modeled in start up, steady state, and upset conditions, showing the areas of high stress and temperature and indicating whether it will exceed the material's abilities. Parametric and optimization routines can speed model changes and increasing efficiency. This technique can be used during the design phase, be modeled "as built" to determine reliability, or as part of a failure analysis. As with any form of mathematical modeling, solid engineering judgment and experience must be used to ensure accurate results. Otherwise, while the model may converge and yield very convincing color plots, the results can easily be disastrously wrong.
Auto mesh vs. Manual Mesh
If you are familiar with FEA, you may be aware of arguments for and against using "automesh" features in today's software packages. Meshing controls the resolution of the analysis. Too coarse of a mesh in a given region will result in inaccurate results. Too fine of a mesh means wasted computation power, a critical factor years ago when it took hours and even days for a solution to converge. However, manual meshing can be very time consuming, taking up to three times the time it took to develop the unmeshed model. As with most debates, both sides are right. Detailed analysis and various advanced modeling techniques require careful meshing. However, modern computer power as made it possible to auto mesh entire assemblies of items, giving the user the ability to analyze large systems for an overall evaluation. While this coarser, generalized analysis will not be as precise or accurate as manually meshing, it can reveal trends and identify areas of concern for closer analysis. Both approaches are valuable tools for engineering design and analysis. In the tank head case study, the model was manually meshed since the area of interest was known. In the U-joint example, the entire system was modeled to examine mechanical interactions between parts. | |
| | Computation Fluid Dynamics (CFD)
Similar to FEA, this is a computation method to determine pressure gradients, temperature gradients, and flow vectors for gasses and liquids within a specified geometry. This can be used to analyze fluid flow through a heat exchanger tube sheet, gas flow across a body, or plastic flow through a die. This method is often used in conjunction with FEA to determine the fluid temperatures and pressures across structures, developing precise boundary conditions for FEA modeling. Visualiztion of flow patterns can be key in the design process. Go To Top | |
| Kinematic Modeling
This computation method models the physical mechanical interactions, such as forces transmitted by gear trains or material within a material handling system. Friction, mass, gravity, air pressure, and forces are applied in the computer model, allowing mechanical reactions to be analyzed before the first bolt is turned or shaft installed. Pin joints, revolute joints, slots, motors, "ropes," pulleys, even linear and nonlinear springs and dampers can be included in the model. This technique can be used to explore vehicle dynamics, mechanical tolerances, rotordynamics, power train efficiency, bearings, and other mechanical situations. This technique can also be used to put an equipment items through its full range of actions to find peak forces and moments to be used as boundary conditions for a subsequent Finite Element Analysis. | |
| Computer Aided Drafting (CAD)
Using computer programs such as AutoCad, drawings can not only be quickly produced, but easily replicated and modified as needed. This has been the standard way to produce engineering and construction drawings for over a decade. This is primarily a 2-D approach, although many CAD packages now have some 3-D capabilities. | |
| Solid Modeling
Instead of starting with a 2-D drawing and trying to create 3-D geometries as in CAD packages, solid modeling is designed specifically to produce 3-D models. This allows users to create the entire equipment item, assembly, or structure as separate components or as assemblies. Shop drawings are created by specifying the planes to "cut" the model in, creating the traditional multi-viewed dimensioned drawings. This method not only increases 3-D modeling efficiency and gives the designer full view of the entire system, it also creates the required geometry files for FEA, CFD, and Kinematic Modeling as well as photo-realistic rendering and animation, reducing the time and costs when more than one type of 3-D service is required. See a walk through of solid modeling used in the design process. Go To Top | |
| Virtual Prototyping
Physical prototypes of products, equipment, and even repairs can be an expensive and repetitive undertaking. Even getting something that works the first few times does not necessarily meet long term reliability requirements. Using solid modeling, kinematic modeling, and other computer techniques a design can be tested and evaluated for a wide variety of conditions before the wrench is turned. This process starts with the conceptual design and going all the way to the shop drawings for the physical prototype. Once a physical prototype is created and tested, the results of the testing can be used to "tune" the virtual prototype, providing greater accuracy in performance prediction. See an example of a virtual prototyping process. | |
| Conceptual Design
Designs to not start with a finished drawings. Usually a new product, equipment item, or service starts as simply an idea. A conceptual design is a visualization of how the new item may look or function as a stand alone item or as part of a larger system and can be done with 2-D illustration, 3-D modeling, or even animation superimposing video of the intended site. Issues such as ergonomics, installation, maintenance, and overall systems integration can be addressed at the outset, providing critical design guidance. This gives the design's creator a tool for explaining the concept in a clear, concise manner and can then be the starting point for subsequent detailed development. A conceptual design can also be used to provide a technical illustration or animation of a product or service without revealing important technical details. See an example of a conceptual design. Go To Top | |
| Shop Drawings
For design projects, this is often the final engineering product. From these drawings the fabricator will have all of the information needed to produce the item designed. These drawings can be 2-D views in plan and side elevations with required dimensions, assembly drawings, or bill of materials. In other projects such as failure analysis or equipment modifications, this is often the first step in determining how the equipment item was originally designed. | |
| Failure Analysis
A specific technical discipline, failure analysis uses a wide variety of tools such as FEA, CFD, kinematic modeling, and traditional engineering methods to determine what conditions contributed to an equipment failure. Failure analysis often uses a systematic approach to evaluate various factors in a failure and is the first step in eliminating the root cause of a particular failure. | |
| Reliability Analysis
Similar to a failure analysis, a reliability addresses the equipment's lifespan. Where a failure analysis asks, "Why did it fail?", reliability analysis asks, "When will it fail?" and "How can I prolong its lifespan?" Using a variety of techniques such as FEA, CFD, kinematic modeling, and traditional engineering methods, the equipment is evaluated for a predicted range of conditions. Based on the mechanical and process response, a lifespan estimate is developed. See an example of a reliability analysis of a vehicle barrier as well as a crane bucket.. | |
| Photographic Interpretation
A technical analysis of photographs or video to extract specific information such as dimensions, elapsed time, location, or amount of damage. While this technique is almost as old as photography itself, modern imaging techniques have provided powerful tools for photographic interpretation. | |
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