“The journey of an object from birth till death is called Life Time Machine (LTM) or Life Time Engineering System — it is more like a time machine…” – Dennis R. Pigneur, Automated Control Systems for Civil Engineers.
When we create a design for another product at work, most commonly known as ‘Automation’, there are several factors we take into consideration. These include whether our designs will be developed in-house or are required by our clients. This article looks into some of these elements that may be considered part of life cycle management.
We’re going to cover what autocad/fused-layer modelling is and how you can start incorporating it into your own practice and understanding of using CAD software. You’ll also get a brief view on how you can leverage this technology. Alongside our discussion we will look into the various ways that AutoCAD allows us to manage our products based on their lifecycle needs.
Read further below for more details:
What is Fused Layer Modelling?
Fused layer modelling is one of the techniques used within the field of 3D modelling. For those unfamiliar with fused layer modelling (FLM), it adds layers to existing models allowing users to extend upon their existing model or change or enhance its properties to fit the desired outcome of the project. It can be thought of as being similar to extruding layers to a material, which results in a new model that acts “different” than the original. One advantage of this technique is that it is able to produce much higher quality models. By adding additional layers, the overall cost of the design is reduced to an almost negligible amount. However, by adding layers, you are limited in the changes that can be made which will affect the final result of the design. The main disadvantage is that if one does not have access to appropriate CAD software (for example with no knowledge of Photoshop, Corel, Maxima etc), is that there is a risk of creating incorrect models as one cannot add layers at the end of each iteration and therefore cannot complete full copies of a design.
The majority of FLM systems being produced are now available to the public including Adobe Design Suite, Autodesk InDesign and many others making them accessible to anyone wishing to use a FLM software package. Although they may not be able to support every single feature of modern software packages, it can still be useful to incorporate them into the workflow in order to improve productivity.
What Can I Use Software Packages for?
The advantages of AutoCAD/fused-layer modelling techniques are generally applicable to any type of engineering task where there is a need to alter variables in the model. It can be particularly useful when designing aerodynamic surfaces of planes, bridges, tunnels, domes and other structures. A good illustration of the uses for these models would be a curved tunnel. Most generalised applications such as roundabouts could be used for flat earths. In cases, where you would wish to modify the model by extending and modifying sections, flocked-model software should be used. Below are some examples of where the methods are generally applicable:
Geometrical Flows
Flows around pipelines, dams, bridges, domes etc should be modelled as pipes and water tables. Flowing along them may appear smooth but when you apply pressure on either end of the pipe on the surface, cracks of different sizes can start appearing in the surface. As soon as the structure begins to collapse over, the flow cannot be allowed to continue so the water table level will increase unless some form of correction is applied.
A curved tunnel under construction should have both sides cut-off so the flow can exit through the roof.
The above image shows the main section of a curved tunnel under construction.
A curved tunnel section (from left to right) shows multiple cracks forming while the upper side remains clear.
In contrast, an unbraced tunnel section shows just a crack in the base of the tube, as a result the total depth of the cave is equal to the length of time taken across the boundary of the first point of entry. If a tunnel is fully filled then the flow goes forever. This is commonly seen using hydraulic structures where they can be shaped in a way that causes the tunnel to deform over. As a result, it looks nearly identical to a river, although the flow will never terminate. Under normal circumstances, the walls would form again after the damage has stopped but if the whole tunnel was constructed without considering the cracks then the wall will be destroyed and this will lead to a large hole.
The image above shows all the fractures created as a result of the deformation and breaking off. This will require building to act as a barrier to block and stop the flow and allow some water to run through.
How Does Material Flowing Through the Tunnel Create More Cracks and Damage?
If a tunnel has cracks in the base and other cracks on the outer wall, how can it be safely managed? This is a common concern among civil engineers who want to avoid cracks and can cause catastrophic failure especially in regions like high altitude caves or tunnels. When materials get too close together there can be small tears forming in the seams, which will widen slowly until eventually causing the entire structure to disintegrate. There is thus a danger of simply letting some material flow through the cracks and see if the cracks widen before finally collapsing beyond control over the surface. So how do we manage cracks on the surface?
Although the cracks are present on the surface and as mentioned previously, they appear to disappear over time. Some ways that cracks can be maintained over longer timescales are listed below. This approach relies upon building to protect the surface rather than trying to completely fill the cracks. This will involve filling cracks with concrete bricks and then reinforcing adjacent sections. While this method seems to prevent cracks from growing due to erosion, it may however lead to cracks becoming larger on the surface as a consequence of the weight of the parts and the force exerted on them. At least on a superficial level, cracks in tunnels are created by forces of gravity acting over them, because sometimes the tunnel walls and ceiling need to be removed or broken down and then installed in place. Once this happens, the cracks become wider, more difficult and more likely to grow back. Another possible cause of failure is poor drainage and exposure to moisture. Therefore, it is important to consider weather conditions in which the surface takes place, ie. where there are temperature ranges and humidity levels. The cracks can be controlled by placing concrete bricks on top of the surfaces. They will only enter through certain edges in order to provide better protection from damage but will not enter underneath the surface. Furthermore, cracks become smaller over time as water leaks out the cracks.
By taking steps to build against the cracks, cracks that don’t begin to grow quickly because they remain the widths that were initially formed can be more easily managed. Here is a video showing this process (see video for more information)
Build against the cracks by putting cement blocks on each edge and then applying a grouting solution to create new spaces in the cracks.
Another way to reduce chances of cracks occurring is to ensure proper ventilation through providing vents, holes and openings in the tunnel sides. Ventilation is essential to the successful operation of the system. Additionally, having external controls for opening, closing and changing directions ensures that the system’s Centre of gravity is not shifted too far away from the surface. Depending upon the location, having continuous flow in and out makes it harder to move the tunnel, which will reduce the likelihood of moving it outwards in case of natural disasters such as floods. Finally, if cracks are properly ventilated and not allowed to spread wide inside the tunnels they will gradually disappear which greatly increases the viability of the tunnel and reduces downtime.
Builders and architects will often advise you to construct a trench around the cracks so that fluid will not enter the cracks but instead exit them through the sides of the tunnel wall.
What Are Models Made From?
A lot of people might seem surprised to hear about the possibility that models can be built from scratch, especially when it comes to buildings which are designed with a particular purpose in mind. A model (also called digital data) in itself can be made from pretty much anything and can be derived from a variety of materials. The choice of material can be dictated by size, shape, appearance and purpose.
For example, a rectangular shaped house can be modeled using a solid slab of wood or clay. As the dimensions are fixed, these can be represented by two numbers representing height and breadth. Alternatively, larger and broader rectangles could be made from mud brick or stone blocks while a triangular shapes can be made up of stones, bricks or even metal blocks. All are of course dependent upon the shape of the building.
Building a model out of clay could result in the creation of a cube and a square. Clay models are often used in research to test for potential errors in geometry. Also, it is used in simulations to simulate real-life phenomena, for instance earthquake prediction (see How Earthquake Prediction Programs Work). When we build a model, we usually think of the materials used in building blocks and usually base that on a set of measurements taken from a given site but some examples of other types of models include hollow and open cylinders, cylinders in cylinders and spheroids (see Building Spherical Objects in Solid Blocks vs Hollow Ones)
Building a model out of stone has been a widely successful technique used in archaeological digs. Stone is a naturally shaped clay which tends to be highly porous and requires lots of labour to obtain adequate amounts. It can thus easily be created on demand with a number of raw materials (think
