Verification of Weld Joints
- Objective: - To simulate three different weldments for three different weld materials under a given load.
- Model Details: - Following model is given for the simulation,
In the geometry we can see that, a vertical and a horizontal plate is wleded together along with two ribs. For the meshing part, as the load is applied on the horizontal plate on the rectangular cut in it, we reduce the mesh size on that plate. After refining the mesh to maximum extent possible, we arrive at mesh as shown below,
Here, I have applied \'Body Sizing\' to Vertical Plate (with circular hole) and the two ribs with 7.5mm element size, and another body sizing to horizontal plate (with rectangular plate) with 5mm element size.
Mesh Details:
Number of Elements (Hex-20) :- 5186
Number of Nodes :- 31863
Average Element Quality :- 0.8798
Except the 5 contacts between the \'big Plate\', \'small plate\' and two ribs, all other contacts are kept as \'bonded\'. The remaining 5 contacts are changed to \'frictional\' with friction coefficient as 0.2.
The material for the weldments is to be changed for the simulation, and following three cases are to be considered,
Case-1 :- Stainless Steel for all the geometries. For Stainless Steel material, its properties are,
Young\'s Modulus = 193 GPa
Yield Strength = 207 MPa
UTS = 586 MPa
Case-2 :- Same as case-1, except weldments are of material Aluminium Alloy (high strength, wrought). For Aluminium Alloy material, its properties are,
Young\'s Modulus = 73.8 GPa
Yield Strength = 363 MPa
UTS = 449 MPa
Case-3 :- Plates are of SS, ribs are of copper and weldments are of Bronze, cast. For Copper material, its properties are,
Young\'s Modulus = 110 GPa
Yield Strength = 280 MPa
UTS = 430 MPa
and for Bronze material, its properties are,
Young\'s Modulus = 80 GPa
Yield Strength = 144 MPa
UTS = 267 MPa
- Loads and Constraints: - As can be seen from the figure below, the model is fixed on the 5 circles of the vertical plate. A load of 15000 N is applied on the rectangular cut surfaces of the horizontal plate.
In \'Analysis Settings\', \'Large Deflection\' is switched ON, and the solution is solved for single time step of 1 sec.
- Results: - For the results, we will compare the Directional Deformation, Equivalent Strain and Equivalent Stress generated in the three cases.
We will first list the results for the three cases separately and then compare them,
Case-1 (SS weldments) :-
Max. Equivalent Stress = 358.28 MPa
Max. Equivalent Elastic Strain = 0.0020041 mm/mm
Directional Deformation (Y-axis) = 0.33558 mm
Below from left to right are figure for Equivalent Stress, Equivalent Elastic Strain and Directional Deformation respectively,
Case-2 (Aluminium Alloy Weldments) :-
Max. Equivalent Stress = 364.04 MPa
Max. Equivalent Elastic Strain = 0.0035196 mm/mm
Directional Deformation (Y-axis) = 0.35084 mm
Below from left to right are figure for Equivalent Stress, Equivalent Elastic Strain and Directional Deformation respectively,
Case-3 (Bronze Weldments) :-
Max. Equivalent Stress = 371.17 MPa
Max. Equivalent Elastic Strain = 0.0034431 mm/mm
Directional Deformation (Y-axis) = 0.38974 mm
Below from left to right are figure for Equivalent Stress, Equivalent Elastic Strain and Directional Deformation respectively,
In Case-2 and 3, as the max. Equivalent Elastic Strain is in the weldments, the model is flipped upside down for better visibility of \'Max\' tag.
- Conclusion: -
From the material data we can see that, Young\'s Modulus of Bronze and Aluminium Alloy is very low compared to that of SS. And so as we expect, Case-2 and Case-3 have larger Directional Deformation than Case-1. Additionally in Case-3, ribs are of Copper which also have lower Young\'s Modulus, while in Case-2 ribs are of SS. This is evident from the images below, which compares Directional Deformations of Ribs alone for the 3 cases. Case-1 and 2 have almost same \'Directional Deformation\', whereas due to copper ribs, \'Directional Deformation\' is much higher in Case-3
Also the Equivalent Elastic Strain is higher for Case-2 and 3 than for Case-1, this is also attributed to the lower Young\'s Modulus values of Aluminium Alloy, Bronze and Copper. For Case-1 as the material is same for all the geometries, its max. value is observed at sharp corner of the rectangular cut where external load is applied. In Case-2 and 3 however, as the weldments material is easily deformable compared to SS (due to lower Young\'s Modulus value) max. Equivalent Elastic Strain is observed in Weldments.
The Equivalent Stress magnitude in the images above shows stress for all the geometries with increase from Case-1 to Case-3, and in all the cases it is observed at the sharp corner of rectangular cut where external load is applied, the Equivalent Stress in maximum. However, this stress is high, mainly due to sharp edge, and its variation for the three cases is less than 4%. This stress is expected to be similar, since we are not changing the Plate material, also we can see that the equivalent elastic strain is same for all the cases at this maxima point (using probe). What we should focus on is the Max. Equivalent Stress developed in the weldments shown in the figures below,
So from the images above showing Equivalent Stress of weldments only, we can see the max. stress point is same for all the cases. It is the point where vertical shear and vertical components of bending stress add up. And this stress is highest for the SS weldments, while it is lowest for the Aluminium Alloy weldments.
We then see the Safety Factor images for the weldments only, and we can see from the images below, Aluminium Alloy has the highest min. safety factor,
Safety factor is the ratio of actual stress to limiting value of stress (like yield or ultimate). For Aluminium Alloy, the Equivalent Stress generated is lowest and the yield strength is highest. So, this increase its safety factor (almost twice that of SS). We can notice that, even though SS has highest equivalent stress among the three cases, it safety factor is better than broze because of higher yield strength and UTS.