FEA: Splitting Quadrilateral Elements | Quality fixing for thinshell elements in FEA meshing | Ansys, Hypermesh, Solidworks, Nastran

To get accurate results, quality fixing of 2D thin shell element is inevitable in meshing task. Apart from dragging the nodes to solve the quality errors and warning, we can also split the Quad elements into triangular elements to solve the error.

Note that, this method should be done only if the quality cannot be solved by dragging the nodes of quad element.


Usually the pre-processor like Hypermesh, Ansys, Solidworks, NX etc has a manual Meshing sub panel includes two following options for splitting quadrilateral elements:

• Split Diagonal → splits a quadrilateral element into two triangular elements.
• Split Quad → splits a quadrilateral element into four quadrilateral elements.

We  can split quadrilateral thin shell, plane strain, plane stress, plate, or membrane elements.

The two or four new elements:

• have the same attributes as the original element, such as thickness and material properties, family, and direction of the normal
• have new element labels

Note: If the element er split is associated with geometry, the two resulting elements will also be associated with the geometry. 

FEA : Solving element interference in mesh model | Ansys, Hypermesh, Solidworks, Nastran NX

To solve Element Interference

Interference Check tools are used to check the mesh model for element interference, the Element Interference Result/Fix form allows us to view, manipulate, and try to solve the areas where interference occurs.

The tools on the Element Interference Result/Fix form should only be used to repair regions where the amount of interference is relatively small, relative to the elements' size and thickness.
Usually, the Element Interference Result/Fix form does not allow we to fix areas of self-intersection within a single component.

The Element Interference Result/Fix form divides the model into separate "problem areas" that represent the regions where interference occurs. Generally the pre-processor software designates these regions by finding each interfering element and then clustering an interconnected set of elements that interfere with each other. Because resolving interference on a large model can be a difficult and iterative process, working with one problem area at a time can help we manage the scope of the problem. Each problem area is comprised of multiple components.

To actually repair the interference between components, the pre-processor moves the nodes on the interfering elements as well as on the elements surrounding them based on a percentage of the elements' thickness. Different options on the Element Interference Result/Fix form allow we to constrain either specific nodes or entire components to control this movement. If we're repairing the interference on a model that contains associated geometry, the software maintains the geometry association.

Process of Interference Repair

The following is a general process to guide we through the basic steps of identifying and repairing element-based interference:

1. Use Interference Check to check the model for interference. Use the Interference Check Options form to specify options for performing the check.
2. If the software detects interfering elements, pick Result/Fix Form from the right hand menu to open the Element Interference Result/Fix form.
3. Use the different display and grouping icons at the top of the form to examine the different problem areas and determine in which order we're going to try to address them.
4. Use the constraint icons at the bottom of the form to view the existing nodal constraints on each component and modify them if necessary.
5. When we are satisfied with the nodal constraints,we can pick Fix Interference to repair selected components.
6. Select OK to accept the changes to mesh model, or Select Undo to undo the interference repairs between selected components.

Nodal Movement during Interference Repairs

With Fix Interference, the software moves the nodes in the direction of their constraints. In order to prevent the drastic changes in curvature that could by caused by moving just the nodes on the interfering elements, the software also moves nodes on four surrounding rings of elements.
Interference Repairs Performed in a Series of Iterations

The pre-processor would move the nodes on the rings of elements in a series of up to ten iterations. After we use Fix Interference, the software reports the number of iterations performed in the List region. If the software is unable to repair the interference in ten iterations, we can pick Re Iterate from the right hand menu to have the software perform up to ten additional iterations.

FEA : Shell Element Normals, Assign Material Side orientation in Thinshell Meshing, | Ansys , Hypermesh, Solidworks, Nastran NX

Checking Shell Element Normals in thin shell meshing

All shell elements have a normal (perpendicular) that defines the top and bottom of the mid surface meshing.
If we create,copy or move elements, shell normals may have a chance to change their different directions. During Post Processing and Optimization, it is necessary that the elements should have consistent tops and bottoms. All perpendiculars must point the same direction.

Shell normals and material orientation are independent of one another.Usually the pre-processing softwares have two tools for controlling shell element normals.

• Shell Element Normals (Meshing task) lets you change shell element normals on a model that doesn't contain underlying geometry.
• Material Side (Modeling task) lets you specify shell element normals on a model that contains underlying geometry.

Using Shell Element Normals

To use Shell Element Normals, select a "base element" with the desired orientation. Starting at that element, the command shifts the shell normals of the elements adjoining the base element until every element in the model is aligned.

For example, let us consider a sheet metal car bracket has been created in one quarter and then duplicated downward by reflecting. As a result, the shells normals of the lower half point in the opposite direction. By choosing a base element in the upper half, the command adjusts the lower elements until they're all pointing in the same direction.

Using Material Side

We can use Material Side in the Modeling task to control the direction of shell element normals when we mesh surfaces. Once you assign a material side to a surface, the mesh generator uses the material side's direction as the direction of the element normals.

We can't modify the material side for surfaces that make up a volume.

If we don't set the material side before you mesh surfaces, the mesh generator would automatically assigns a consistent direction for element normals. For example, let us consider of a mesh is generated on a non-manifold part and a manifold part where the software assigned the element normals.

If we use material Side and then mesh the part, the element normals point in the direction of the material side. Here, we should use Material Side to control the shell element normals on a non-manifold part and a manifold part .

Chrome : To Fix the error ERR_CONNECTION_REFUSED | Error 102 (net::ERR_CONNECTION_REFUSED): Unknown error in MAC, Windows, Android

Error display in chrome browser :

Error 105 (net::ERR_NAME_NOT_RESOLVED)



Solution:

1.Remove Cookies : 

In chrome browser, Go to settings → Show Advanced Settings → Privacy → Content Settings → Cookies →All cookies and site data → Remove all

2.Check Firewall Settings 

If you have any antivirus or firewall enabled in your device, then ensure, Google chrome is allowed in antivirus and firewall.

3.Check Proxy Settings

In Chrome browser, Go to settings → Show advanced settings → Change Proxy settings → LAN settings. Check Automatically detect settings is enabled and press OK.

4.Malware Removal 

Check for malware. If you observe any unusual ad displays, unusual page redirect, pop-up ads etc, then check chrome toolbar or extensions and remove it.

Android : Fix screen Flickering due to rain / water damage in Android , iPphone , Replacement Warranty Claim

Water damage in Android , iPhone

Water damage to smartphones would happen anytime for anyone. It would be useful to know the do's and dont's , if your Android / iPhone smartphone is water damaged.

Dont's

• Do not connect with charger. I insist this point, because it would spoil the phone completely.
• Do not keep it on. Switch off the device immediately.
• Do not use microwave oven or hair dryer to dry the device.

To fix Screen Flickering :

1. After water damage, if the screen is blinking or flickering , then immediately you have to switch off the mobile phone.
2. Remove the battery , SIM card, sd memory card from your mobile phone.
3. Take a soft cloth and dry the water in the battery, visible portions of the phone etc.
4. Keep the phone under fan or medium sunlight for 2 hours .
5. Next is the crucial step. It is to remove the small screws of the phone and disassemble the panel and screen.
6. In practical, an individual won't have screw drivers for such small screws. In such case, I recommend to take the phone to the nearest mobile service center. The service guys are experts in such activities.
7. Remember, you should not switch on the phone in the mean time.
8. After dissembling the panel and screen parts, use some cotton sponge buds to remove the water traces in the circuits, speaker port, charger port, mic.
9. Handle it very softly.
10. Let the parts dry for another 7 to 8 hours completely under fan.

• Now, assemble the screen panel with back panel. No need to tighten the screws.
• Insert the battery.
• Switch on the mobile phone.

• Now, ensure that your phone is working normal. Keep it for five minutes and observe whether any over heating occurs.
• If the phone works normal, switch off the phone and tighten the screws, insert sim card and memory card.
• Charge the phone, by keeping the phone in switch off state.

Observe whether heating occurs. If the phone is heated, immediately disconnect the charger.
Otherwise, your phone is normal.

Replacement warranty for water damage:

• Replacement warranty is not applicable for water damage. 
• Your phone and battery has color changing paper sticked in white color.
• It will change the color to pink, if the sticker is dipped with water. So, if turns pink, then the manufacturer will consider that as water damage and reject the warranty claim.
• If the color remains white and phone is still not fixed, you can try for replacement claim.

Punjab National Bank - PNB | Missed call Number for checking Balance enquiry in PNB

To check balance in your savings or current account in Punjab National Bank, missed call option is introduced.

Steps to Know your Balance in Punjab National Bank (PNB):

1. Give a missed call to the number 1800 180 2222 from your registered mobile number . To register your mobile number to your branch of Punjab National bank , you can do it directly in your branch or otherwise you can also register it through online banking account.
2. After giving a missed call, within 5 seconds you will receive an SMS stating the balance like "Avl Bal as of 10-03-2015 08:33:20 A/c-XXXX6598 : 4,542.18 -Canara Bank"

You can use this facility whenever you can . But don't use this option very frequently as some banks may indirectly cost you in some other ways for such facilities .

Other ways to check balance of Punjab National Bank account :

• Go to any ATM center nearby and insert your Punjab National Bank debit card, Enter your PIN and choose the option check balance in the screen. Now your balance will be shown in the screen. After seeing the balance, cancel or End the screen and ensure it is logged of before coming out
• If you have online internet banking account in Punjab National Bank , just go to official Canara internet personal banking website and login with your userid and password to know your account summary including balance, deposits etc.
• If you have android Smartphones, then Install PNB m-banking application app from Google Play store. Register for one time and you can manage your PNB bank account from your phone itself.

FEA : Finite element Analyis topology, shape optimization, adaptive analysis - Basics

Intelligent Tools

Finite element modeling requires some necessary decisions like selecting

• Element type,
• Mesh density
• Applying Constrains, Restrains and loads 

Current generation Pre processing tools has several capabilities that intelligently guide us through the simulation process, and help us to get accurate / correct results.

Adaptive Analysis

One of such major intelligent tool is Adaptive analysis capability.
Adaptive analysis includes some primary decision parameters like number of elements required to accurately capture the desired performance measure.

1. To capture displacements or Eigen values (resonant frequencies), generally a relatively coarse mesh will suffice.
2. To study the stress results generally requires more elements and more attention to having elements in high stress regions.

Finite element mathematical formulations generally assume limited variation of stress across any one element. Adaptive analysis allows proper element density to be set automatically.

Simulation offers r (node position), h (element refinement and remeshing), and p-element adaptivity. A p-element tetrahedron has been implemented for linear statics analysis. The p-element implementation takes full advantage of the automatic meshing capability and geometry-based loads and boundary conditions. The combined r,h,p adaptive approach now available for solids leads to the most rapid solution convergence on problems with highest geometric complexity.

Optimization

All processors like Hyperworks - Optistruct , NX Nastran, Solidworks  etc come up with optimization strategy which help us to design an cost effective, strength sufficient design .

Generally the Optimization module will provide the ability for analysis to directly guide design. It can help us rank possible design changes and understand the required magnitude of changes to achieve a particular goal.

• Optimization allows you to effectively improve complex structures with interacting loads that cannot be handled with manual methods.
• The geometry-based optimization capabilities work directly with the Modeler geometry. Allowable geometry changes are defined by selecting dimensions and entering variations in a form.

Design goals, as well as other constraints on deflection, stress, or natural frequency, are also entered through forms. As the design is updated through optimization iterations, the FE model (mesh, loads, and restraints) is updated automatically. Geometry updates maintain original design intent through the variational geometry constraint network defined during geometry construction. Modified versions of geometry are maintained through the data management capability.