Update May 1, 2010: This position is no longer available. Our sincere thanks to all the applicants. We greatly appreciate your response and wish you all success in your future endeavors. - Rob.
CAE Sales Engineer - Rochester, NY SimuTech Group, Inc., is a leading mechanical engineering firm specializing in offering high-end engineering simulation services and products to our customers. SimuTech is the largest reseller of ANSYS engineering simulation software across North America. To complement the sales and support of this technology, the company provides training, mentoring, consulting and testing services. We are also resellers of other leading simulation software such as Autodesk Moldflow, fe-safe, TOSCA and CivilFEM.
At SimuTech, we pride in our employees and their dedication towards providing excellence in engineering simulation. We hire and retain the top engineering simulation experts in the industry. We offer industry leading compensation and benefits package. We have an immediate opening for a passionate and top performing Sales Engineer to grow our upstate NY (East) territory for all ANSYS products.
In this position, the individual is responsible for locating and developing new accounts and maintaining existing ANSYS customer relationships. Below are key qualifications and job requirements:
Preferred qualifications:
2+ years min. of proven direct sales experience
Bachelors degree in engineering (preferably mechanical engineering)
Excellent prospecting, qualification, presentation and selling skills
A team player attitude, customer service oriented with strong work ethic and hunter attitude.
Experience in selling engineering simulation is not required but knowledge is preferred.
Experience selling to C-level and major accounts is a plus.
Valid driver's license with a clean driving record is required.
Travel about 25% of time is expected.
If you are a top performer, have a drive to succeed and a passion for sales, please forward your resume to roba@simutechgroup.com
Ever see those cool CFD animations of a model with a moving boundary? Ever wondered how much of a headache those are to set-up? Well it turns out it is not bad at all. I have run through a generic example below to show you how quickly you can do it in CFX.
Problem Description:
In this problem we are going to be modeling a moving wall on a tank. The assumption that the wall motion is know will be made and supplied to the CFX in a comma separated value (csv) format. The model will be general so that you can apply the method to similar problems.
Set-up:
The geometry was generated with two bodies combined in one part. The one domain, hereafter called the port, is the domain where the mesh is going to be deformed because of the moving wall. The other domain is the tank to which the fluid is being ejected. The mesh in this region will not be deformed.
So we move along to opening the mesh file in CFX and we begin by changing it over to a transient run. The next step would be to opening the Default Domain and in the panel change the Mesh Deformation option to Regions of Motion Specified. The next step is to create a sub-domain for the port region under the Default Domain. In the sub-domain panel, select the port region for the location and move over to the Mesh Motion tab.
We are going to use a specified mesh motion using ccl. In the current case the motion is in the z-direction so I specify a name of the cel expression MeshMotion which we will define next. A key point we are going to use is that we want to compress the mesh in the entire domain evenly to maintain the best quality mesh we can.
Defining a temporal functions from csv file
Since we are assuming we know the movement of the wall, we are going to read it in using a csv file. We first must make sure that it has the proper header. The header of the csv file should follow:
[Name]
SpecifiedMotion
[Spatial Fields]
X
[Data]
X [m], displacement []
…
Now the data should be a function of time. But we import it as a spatial variable. We will change it over when we define our cel expressions. To bring this file into CFX, we choose Tools -> Initialize Profile Data from the pull-down menu. After selecting the data file we notice the function is consistent with our header.
The next step is to change the spatial function into a temporal one. We will do this by creating an expression called MeshDeformation. We will then define this as SpecifiedMotion.displacement(t * 1[m] / 1 [s] ) * StrokeDistance. Note we will define StrokeDistance later.
Interpolation Functions and Other Expressions
First we will generate a function that will be used to make sure we compress the entire sub-domain evenly. We do this by generating a user-function we will call InterpolationLocation. We put unit of [m] in the Argument Units and [] for the Resulting Units. For the one-dimensional function we will supply the data pairs 0, 0 and 4, 1. We do this because the port mesh at 0 [m] will not be deformed and the port mesh at 4 [m] will deform the full amount we will specify (my port is 4 [m] long).
Next we must create our MeshMotion expression. For this we define it at MeshDeformation*InterpolationLocation(z-Total Mesh Displacement Z). Note the InterpolationLocation is the function we just defined and Total Mesh Displacement Z is the predefined expression that outputs the total mesh displacement in the z-direction relative to the initial mesh. We defined the MeshDeformation expression earlier.
The final expression we need to define is the StrokeDistance. We simply define this through a cel expression to be -4 [m]. The negative sign indicates that displacement will be in the –Z direction.
That is all there is to it. That wasn’t so bad was it? Now there are just the smaller things to add into the model such as transient result files and initial conditions. These are straightforward as in your other models. Hope you found it useful. Obviously more complexity can be built into the model, but this shows the basics of the moving mesh portion.
_____________________________________________________
Per requests, I have included some images to help you follow along. The first image is shows how to set-up the CSV file. Note you can do this in a text editor like notepad, or you can use Excel to develop the data and save the data as a CSV file. Either way the ASCII data should look like:
How the CSV file should be spaced.
The next step after we generate our CSV file is to import this into CFX. This is done by selecting from the pull-down menu Tools -> Initialize Profile Data. Point to the location of your CSV and select OK. If you now look under User Functions in the tree, you will see SpecifiedMotion. Double-click this and the image below would appear.
Function from CSV File
Now that we have this we can generate our CEL expressions. These expressions are given above and shown in the image below.
CEL for the above Example
The file piece of the puzzle is to add the InterpolationLocation user-function. The final syntax of this user-function is shown below. Note that the 4 is length of the chamber we wish to compress.
Using a CFX user function for interpolation
I hope you found the original demo interesting and new images helpful in generating these types of models. Cheers!!!
I just worked on an FEA model which was essentially a flat, very thin plate of plastic with a pressure applied. Initially, I always use small displacement and linear contact (bonded) for debugging a model just to make sure that loads and boundary conditions are correct. This saves time because large deformation effects can introduce much longer solve times. The linear model solved fine.
When I turned on the large displacement option (nlgeom), the model failed to converge even after several cutbacks (bisections). I certainly did not expect to solve the model in one substep, but I thought the default bisection algorithm would find a converged solution. I was using automatic timestep control. I reduced the initial substep until I eventually obtained a solution, but by this point the subsequent substeps were so small that it would take many, many substeps to complete the load step.
I noticed that after the first substep converged, convergence for later substeps required only a few iterations. Therefore, I broke the load step into 2 separate steps. In the first step, the load was reduced to the value that converged earlier, about 1/1000th. In the second step, I specified the full load with a reasonably sized initial substep. The model had no trouble converging, even though the load had dramatically increased between steps. The reason is that the initial stiffness of the plate is bending only, because it was flat. Since it was a very thin plastic component, the bending stiffness is very low. The first step established some membrane stiffness as the plate tries to assume a more spherical shape. Once the load generates some membrane stress and there is membrane stiffness, subsequent predictions of displacement are more accurate.
I have also used this 2 step load strategy for preloading of bolts. Sometimes, not always, the contact resisting the preload has trouble converging with the full preload. Before contact is established, there is no stiffness resisting the preload. Then, the contact overcloses so much that the solver cannot resolve the overclosure efficiently.
I have been watching Vancouver Winter Olympics 2010 with great deal of attention. My loyalties lie with US but cheer any genuinely great sporting achievement. What fascinates me is the true grit and determination of these athletes to overcome great odds to attain perfection! And knowing our passion "engineering simulation" has helped them along towards these levels of perfection really brings a huge smile on my face.
Images Courtesy: www.fluent.com
I wanted to bring light to some of the engineering simulation such as FEA, CFD etc., that goes on in preparation towards these levels of perfections.
Above images show pressure contours on a simulated skeleton slider, with pathlines colored by velocity magnitude (Postprocessed by Ensight). The story behind the simulation is as interesting as the technology itself. You can read the complete story here. The story in short goes something like this: In preparation for 2006 Winter Olympics at Turin, Italy, Kristan Bromley, the top-ranked skeleton bobsled competitor in the UK, approached the Elite Sports CFD Unit - a part of the Sports Engineering Research Group (SERG) in Sheffield, UK - and asked them to provide CFD flow simulation support to increase his chances of success. Bromley's goal: Minimize the overall aerodynamic drag by assessing small changes in surface texture of his skin-suit. Bromley ended up with a respectable 5th ranking in Turin Winter Olympics and went on to bring home the first gold medal for Britain since 1965 at the 2008 FIBT World Championships. Bromley maintains philosophy of using advanced technology to enhance on-ice performance. Although, the CFD analysis may have been just a drop in the ocean in terms of the dedication, grit and determination for such olympic athletes, it is still atleast a drop!
More information: http://www.bromley-aet.com/
Below are a few more articles that show the role of engineering simulation that goes into such perfection! ANSYS Article: Giving Ski Racers an Edge FLUENT Article: CFD for Bob Sled Team ANSYS Article: Finite Element Analysis on Mountain Climbing Ice Axe to study crack initiation on serrated blade.
Hats off to all the fantastics athletes and the engineering simulation that is enhancing their performance on ice! :)
I have recently had the opportunity to work on a few steam turbine blade failure investigations and have found a whole new world of engineering simulation that I had not been exposed to. Analysis of turbine blades is its own animal and even though steam turbines have been in use in power generation for a very long time, the physics of power generation is so complex there are many areas that are still not well understood. Being new to turbine analysis I thought my experiences as I lean steam turbine analysis may be useful to others. The first topic I would like to describe has been fundamental to all of the turbine projects that I have been involved with: Modal analysis of a bladed disk row. In each investigation, modal analysis was used to calculate the natural frequencies and mode shapes for a particular stage of blades. This is a valuable tool in determining if the blades are operating near a resonant condition that could be responsible for a failure.
As you can find in any vibrations textbook, modal analysis is an eigenvalue procedure in which the eigenvalues of the equation of motion are the square of the natural frequencies and the eigenvectors are the mode shapes. For blade analysis, SimuTech Group uses an in-house developed code to run a modal Finite Element Analysis on turbine blades. This program is called BLADE.
A portion of the bladed disk is modeled in BLADE which usually consists of a 360°/N sector, where N is the number of blades in the row. The mass and stiffness matrices for the bladed disk sector are then reduced to a superelement containing selected fewer degrees of freedom. These selected degrees of freedom are called master degrees of freedom. They are selected in such a way as to be able to represent and predict the dynamic behavior of the bladed disk.
At operating speed, the rotating system stiffens because of the centrifugal effects. This stress stiffening causes the natural frequencies to be higher than their corresponding values calculated at zero RPM. The effect of the stress stiffening is evaluated and incorporated in the analysis.
If a rotating bladed disk is excited by a forcing which is fixed spatially, there are 3 conditions that need to be satisfied in order to produce a resonant condition:
1.The natural frequency of the blade row is equal to some per-rev forcing frequency
2.The number of nodal diameter of the natural mode equals the forcing harmonic number.
3.The excitation must be able to couple with the blade disk mode shape. For example, the forcing on the blade row must be in a direction that matches the mode shape deflection. If the forcing is along the axial direction of the turbine and the mode shape shows deflection only in the tangential direction, the mode can not be excited. Of course many modes contain components in both axial and tangential directions.
If all of the above conditions are met, resonance will occur. This natural frequency-forcing relationship is usually illustrated as an Interference diagram. In the Interference diagram, the natural frequency is plotted against the number of nodal diameters (harmonic content of a mode). An example of an interference diagram is shown above. The line through the origin is called the Impulse Line which corresponds to the operating speed. Whenever the Impulse Line intersects the natural frequency curves, a resonant condition may exist.
The Interference diagram is used to locate frequencies of interest for a more detailed stress analysis. Resonant stresses are calculated for these conditions and detuned as necessary to estimate the true dynamic stress in each blade. The dynamic stress will also depend on the damping present in the system as well as the stimulus ratio (the ratio of dynamic forcing to the steam bending force in the blade). Dynamic stress analysis is a discussion on its own and will likely be a topic of future entries.
I worked on a 2007 ASME B&PV Code, Section VIII, Div 2 analysis of what was essentially an elbow casting with some additional detail. The more traditional approach would be to use stress linearization on an elastic analysis for stress categorization. However, since the elbow was thick-walled relative to the radius, stress linearization can be non-conservative because the stress distribution is non-linear. Think about the difference between a thick walled cylinder and. thin walled cylinder.
I used the limit load analysis method instead. The limit load analysis has established itself as the preferred method, subject to its limitations, to assess primary sizing (Protection Against Plastic Collapse). The limit load analysis eliminates the need for stress categorization because it is a pass-fail criterion. The material definition is elastic-perfectly plastic. So, the limit load analysis is trying to predict when a plastic hinge forms in a plate an uncontrolled deformation with result with any additional applied load.
The basis for the limit load is straightforward. A value of 1.5 is applied to the desired load (i.e. design pressure+static head+dead weight). Recall that a plastic hinge is formed in a rectangular cross-section beam with an elastic-perfectly plastic material when the moment is 1.5 X the moment required for initial yield. You can find this discussion in a Continuum Mechanics textbook in a section on Beams. I have the book by Shames and Cozzarelli, "Elastic and Inelastic Stress Analysis," which has a pretty good description of this derivation with lots of pictures. So, if you enter 1.5*S (in some cases 1.5S is equal to yield strength at temperature) as your FEA yield strength, and the model converges, you will not develop a plastic hinge in the component you are analyzing. There will likely be plastic strain, especially at structural discontinuities.
Bottom Line: Did the analysis model converge at the desired load (i.e.1.5*Design Pressure)? If yes, Section 5.2, Protection Against Plastic Collapse is satisfied. If not, Section 5.2, Protection Against Plastic Collapse is NOT satisfied.
Advances in the capabilities of computers have enabled the method, since the limit load analysis will take longer to run than an elastic stress analysis. However, post-processing effort is reduced to near zero. Also, there is no question about whether or not the stress categorization line (stress cutline) is in the limiting location.
First question we asked ourselves is why blog? Does this help our customers? The simulation community? Does it help us?
Being an engineering simulation consulting firm and working with a wide range of customers in various industries, we see several unique simulation requirements, from leading edge to bleeding edge! We have seen several times how what we learn in simulating for one industry can so easily be transferable to another industry; how simple tricks or having "been there, done that" would have saved us hours and hours of frustration (if not days!). We also have done some "cool" projects which we love to share with anyone over a cocktail discussion. We have a love-hate relationship with simulation... years of passion and also sometimes days of frustration!
So, that being said, we thought, blogging about our experiences, analyses and physics in general could be a great way to help the simulation community, our customers and also create our voice! So, we plan to post interesting analysis stories, tricks, tips, macros, glitches, software patches (or atleast direct to the right resource), FEA vs. Testing, our perspectives and more.... If our experience, macros, resources etc., can save a few hours for a fellow analyst, we will consider our blog a success!
Let us "Engineer, Simulate and Innovate" together.
This blog is maintained by our engineering analysis group out of Rochester, NY office.
Our blogging team (The SimuSquad) includes:
Jeff Heckman, Jason Zbick, Rolf Orsagh, Mike Sobol, Nick Lynn and Sriram "Rob" Atchutuni.
," which has a pretty good description of this derivation with lots of pictures. So, if you enter 1.5*S (in some cases 1.5S is equal to yield strength at temperature) as your FEA yield strength, and the model converges, you will not develop a plastic hinge in the component you are analyzing. There will likely be plastic strain, especially at structural discontinuities.
