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Stainless Steel Architectural wire mesh is a series of high-tensile, grade 316 stainless-steel wires interlocked together and is commonly produced from 70% recycled material. The individual wires are woven on large weaving looms at Haver & Boecker, our German-based parent company, using a similar technique used to make clothes.
While it appears rigid and unyielding, stainless steel architectural mesh proves to be fairly flexible when a certain length is reached. Because of this characteristic, architectural mesh panels can be applied to countless applications.
The term weave type refers to the way in which the warp and weft wires cross each other. It encompasses four different mesh categories: Woven wire, Cable, Fine, and Specialty.
Wire mesh is best defined as an assortment of rigid wires that have been woven together to form a sheet of mesh that is interlaced.
Cable mesh is a mesh type that is woven on a specialized weaving loom, much like woven wire. The key difference between the two is that cable mesh uses cables rather than stainless steel wires in the warp (vertical) direction.
Mesh profiles that are constructed out of wires that have a very small wire diameter. Fine mesh is particularly sensitive when introduced to mechanical stresses. That said, the application of the mesh is a key factor when classifying fine mesh.
Specialty mesh is a mesh that features a unique pattern and carries the characteristic of employing several different wire types.
A weaving loom that is specifically designed to properly weave stainless steel wires is employed to weave architectural mesh. These looms consist of a warp beam, heddle frames (predetermined amount), a reed, a rapier band, and a front take-up mechanism.
The warp wires are the wires that run lengthwise and are fed directly from the warp beam.
The weft (or shute) wires are the wires that run across the width of the cloth during the weaving process.
The warp beam is a cylindrical drum that is wound with a specific number and length of warp wires depending on the mesh profile and size of the mesh panel. These specifications are calculated prior to winding the wires.
Heddle frames are holders used to separate the warp wires. Each loom contains at least two heddle frames. In a loom that uses two heddle frames, heddle frame 1 initially lifts half of the warp wires while heddle frame 2 pulls the other half down. The heddle frames switch positions after the weft wire is driven between the two sets of warp wires.
A rapier band is the mechanism that drives the weft wire between the two sets of warp wires after each heddle frame cycle.
A reed is the instrument that holds the warp wires in the desired spacing while also driving the weft wire into position.
Lastly, the finished roll of woven wire cloth is wound onto a front take-up mechanism and is removed in increments needed by the framing system of the project.
Once the beam is wound, and the heddle frames and reed are threaded, the whole assembly is transported to a weaving loom. The setup of the loom is then completed by a dedicated technician.
Once assembled, the weaving process is virtually automatic and seamless.
As the loom starts up, the warp beam begins to unwind in very small increments. The front take-up mechanism simultaneously winds the woven cloth at the same small increment in the same direction.
This movement allows the loom to maintain specific tensioning, which is critical when producing high-quality mesh panels.
As the two beams rotate, heddle frame 1 pulls half of the warp wires up while heddle frame 2 drives the other half down. It's at this point that the rapier, whether a two-part or one-part rapier, drives a weft wire between the two sets of warp wires.
Each weft wire is delivered from a separate spool of wire located at the side of the loom. As the rapier returns to its resting position to gather another weft wire, the reed pushes the latest weft wire into its final position.
This process is what creates the precise cross-sections needed to create the perfect aesthetic.
Once the weft wire is in place, the reed returns to its original position. The warp beam and front take-up mechanism then rotate at the same small increment, the heddle frames change position and the loom begins a new cycle.
These simultaneous movements are repeated over and over until the entire mesh cloth is woven.
If you are looking for more details, kindly visit Sheet Mesh.
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Mesh size is one of the most common problems in FEA. There is a fine line here: bigger elements give bad results, but smaller elements make computing so long you don&#;t get the results at all. You never really know where exactly is your mesh size on this scale. Learn how to choose the correct size of mesh and estimate at which mesh size accuracy of the solution is acceptable.
As an example, I will use a simple discretely supported shell. As an &#;outcome&#; I will use the critical load multiplier of the first eigenvalue.
It&#;s perhaps worth mentioning that the &#;outcome&#; can be anything that interests you. If you want to know the certain stress component in a certain node, or a displacement of selected DOF that is ok. Whatever you choose goes, as long as it is actually influenced by the mesh size! I took the multiplier simply as it is easy to obtain, and linear buckling computes very fast &#;
You can see the model I used below. Notice how deformation shape and outcomes change with the mesh refinement. I should write that a mesh refinement check (often called mesh convergence) should be made for each problem. This is somewhat true but let&#;s face it, you won&#;t make it for each problem most likely&#; it simply takes a lot of time! I would suggest you do such a study for some of the most important projects/parts and based on that experience you can extrapolate the knowledge to similar problems.
In this example, I am using QUAD4 elements (normal 4 node quadrilateral elements, sometimes referred to as &#;S4&#;).
In order to establish suitable finite element size:
For our shell, I have performed some analysis for different element sizes. On the drawing above you can see the outcome for few selected meshes. Please notice, that for the biggest elements actual eigenvalue shape is different than in the case of models with more refined mesh.
Usually smaller mesh means more accurate results, but the computing time gets significant as well.
You should search for a balance between computing time and accuracy. In some instances you can increase computing time over 2 times to improve accuracy by 1% &#; for me, that seems unreasonable. Knowing your problem you will know best what makes sense and what doesn&#;t, based on what accuracy do you need.
When mesh density is being discussed in tutorials, different problems are solved with known analytical solution. You can then easily compare the FEA outcome to a known solution &#; you get an error value without trouble. This is a fantastic approach that can teach you a lot, but unfortunately in reality you don&#;t know the correct answer&#; so you can&#;t really do that can you?
Unfortunately in almost all analyses performed for commercial or scientific purposes, the solution of the problem is unknown. In those cases, the &#;typical&#; approach doesn&#;t work. Instead, you will have to &#;guess&#; the correct answer based on the models with different meshes you have done. This is done with the following chart:
Reduction of finite element size leads to more elements, which in turn leads to more nodes in the model. If we build a chart showing the outcome (in this case first eigenvalue) dependence on node count in the model, this chart will be asymptotically reaching for the correct answer (in this case 0.). Node count is only one of the parameters possible here. Since I simply decreased the element size in the entire model it made sense. You can just as easily use a number of elements on the width of your part, or the size of the &#;typical&#; element. If you refine mesh only in a small area (i.e. where the stress concentration is) you can easily use a node count in that area instead of the entire model etc.
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Whatever metric you will use, will depend on the problem you are solving. Node count is the most popular one, simply since it is the easiest one to do &#;
The exact estimation of asymptotic value on the chart above may be problematic or time-consuming. There is a simple trick to make things easier to calculate: instead of node count on horizontal axis let us use 1 / node count. This way the correct answer will be where the horizontal axis value reaches 0. This means that if we approximate our curve with the equation (in most cases linear approximation is sufficient, Excel does this automatically) it is very easy to calculate the &#;y&#; value for x = 0.
Note that the obtained curve is almost linear which is usually the case in most models. From the equation provided by Excel, it is easy to derive the correct answer when x = 0. At this stage, since we know the correct answer, we can calculate how big errors were made in the estimation of results for each finite element size. Below is a chart showing dependence between error and computing time, and between error and finite element size:
From the above chart it is easy to notice that after a certain point, any significant increase in accuracy will &#;cost&#; enormous additional computing time. When I am asked to do a convergence check on mesh refinement those 2 charts are the real answer (you can easily change the mesh element size with node count if you like). Now you know the errors each mesh size gives and the computing time it costs &#;
Now you know how accurate results you will get with a given mesh, and how much time computing will take with such an approach. Making a decision is always problematic. I usually think about how sure I am about loads or boundary conditions &#; usually, those are just &#;estimated&#; and then increased &#;just to be sure&#;. When that is a case a mistake of a few percent won&#;t do any harm.
Time is also a factor to consider here. If you have 100 similar models to calculate increasing computing time 2 times will take A LOT of time&#; just something to consider.
Notice that this chart is asymptomatically reaching 0%&#; if you have made all the steps, described here, and your chart does not go toward 0 chances are you used too big elements. Just know that if you are not sure it is wise to make one model with &#;extremely&#; small elements &#; you know&#; just in case.
When you first do mesh convergence you will realize, that to have a great accuracy computing time will be significant. That is true, but you are not defenseless. Look at the similar shell below. Coarse mesh gives bad results for sure, but the very fine mesh takes a lot of time to compute. Knowing that the stability failure occurs at the bottom I have made a third model (on the right) that has a very fine mesh where it is important, and a coarse mesh where &#;nothing happens&#;.
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This way I go the accurate outcome without incredible long computing time. Of course, there are limits, since you cannot be sure where failure will occur, etc. in some problems. Regardless it is always a good idea to make a coarse mesh, check when things will go south, and then refine the mesh in those &#;hot regions&#; rather than on the entire model. This does not work in all cases, but it works in some &#;
If you have a spare 15 seconds write a comment with your thoughts on the matter or any questions you might have. I have a good history of replying to each and every comment!
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