Week 1 Stress Concentration on a Plate with hole

Objective :-

• To Perform a static analysis on two models of a plate with holes. 
• To select best design with considering analysis and manufcturing of plate.

Stress Concentration :- 

      A stress concentration is defined as high localized stress, compared to the average stress of the body, and is typically found in a region that has an abrupt geometric change or discontinuity.  The body tends to fail at the location of a high-stress concentration or stress riser.

      Various methodologies are developed to get the best advantages from the material to produce an optimized product. Stress calculation becomes a vital part of this process to design a product that won't break or deform. Geometrical discontinuities such as notches, holes should be considered as they make the component weaker. These geometrical discontinuities in the component lead to stress concentration in the localized area.

Methods to reduce stress concentration :-

Make radii in a load path as large as possible.

• Limit the ratio of the large feature to the small feature.
•  Add stress-reducing holes at the end of slits, sharp angles, or cracks to relieve high-stress concentrations.
• Refer to stress concentration charts to understand when you are in a region of diminishing returns concerning radius size.

What is stress concentration factor?

It is defined as the ratio of highest stress in the body to the reference stress. It is denoted by K_t.

Mathematically,

Where
σ_max = Highest stress or maximum stress
σ_ref = Reference stress

Procedure-

Ansys-wrokbench setup

1.Open Ansys-workbench and select static structural and then click on Engineering data to select material.  

2. From engineering data select structural steel.

Open space-claim and create CAD

• Now close Engineering Data tab,and create in space-claim.

•  Create rectangle using rectagle command from tool bar and give dimension for both side.
• Then create hole at the center using circle tool from tool bar

Case-1  

Case 2 :- 

 Open Ansys Mechanical and perform deck-setup

• After updating the model,open it in Ansys-mechanical to by selecting edit.

• After opening Ansys-mechanical go for mesh first.
• Right click on mesh and click on generate mesh 
• mesh size is 5 mm

Case-1

Case 2 :- 

Applying Boundary conditions :-

• Since in this case one side have to be fixed and pull force from another side.
• For fixing one side Right click on static tructure>Insert>Fixed support.

Request for solution results:

• Right click on solution > insert > deformation > total.
• Similarly request for von-mises stress and strain value.

Solve the model:

Right click on solution > solve

• It will take few minuts to solve the model and running the simulation we can   results.

[Note- Similarly request for solution and solve the model for 2nd case

Solution Analysis:

a).Total deformation

Case-1 Total deformation

Case-2 Total deformation

• From the above deformation results we can conclude that using multiple hole will result in increase of deformation after applying same load which acted on same plate with less number of holes.
• So from maximum deformation criteria case-1 is better than case-2.

b).Equivalent stress

Case-1 Equivalent stress

 

Case-2 Equivalent stress

Result comparison:

Sr.No.		Max. deformation(mm)	Max. stress(Mpa)
1	Case-1	0.00027481	0.60996
2	Case-2	0.000297	0.58218

 Conclusion:

Being a Design :

• Being a design  one should go with case-2 cause which helps in reducing stress concentration.
• And this helps in improving the components life without compromising its functionality.
• In further iteration larger dia holes holes can be replaced by smaller dia holes which give more relief from stress concentration.

Being a Manufacturing :

• Being a manufacturing  one should go with case-1 because it consume less time and cost to manufacture.
• Since in case-2 there are additional holes which cause increase in overall labour cost,material and time to manufature this component.