Use of Fea Siemens Nx 7.5
Section 2
Stress Concentration Analysis Problem
Targets: * Describe the steps involved in creating the preliminary FE model and why it is necessary. * Show the development of the final FE model including vague step-by-step instructions. * Describe the application of the final FE model and how it can be beneficial in its purpose.
Brief (Provided In Assessment 1)
A uniform Steel flat bar (material Modulus of Elasticity 200 GN/m2, Poisson’s Ratio 0.3) of width W 400 mm and a length of 4000 mm is restrained as appropriate at one end and under an axial tensile load of 500 KN applied to the other end face. It has been initially designed with a thickness of 50 mm. This gives a hand calculated stress value of 25 MN/m2, which is 1/8 of the material’s Yield Stress, of 200 MN/m2, giving a factor of safety of eight, which is deemed to too conservative.
The flat bar now requires stepped down in size from W to h, forming a shoulder with fillet, at the middle of the bar along its length. For a given radius of fillet, determine the (new) minimum thickness of t capable of withstanding the same tensile force with the factor of safety of four using finite element analysis. Assume Von Mises failure criterion applies, i.e. the maximum Von Mises (un-averaged) stress should not exceed 50 MN/m2.
Your final thickness must be an integer millimetre value to use standard size material.
Brief Assessment
The problem is that with a wall thickness of 50 mm the maximum stress at the radius point will be too high and is in too much risk of distorting or failing. The factor of eight is too high and needs to be reduced to a factor of four.
Brief Proposal
There are two main changeable features in this arrangement, which include the radius and the general thickness. It is assumed that changing the thickness will have a more direct effect on the results and in this scenario that is the only factor which will change. However realistically both these factors would
Stress Concentration Analysis Problem
Targets: * Describe the steps involved in creating the preliminary FE model and why it is necessary. * Show the development of the final FE model including vague step-by-step instructions. * Describe the application of the final FE model and how it can be beneficial in its purpose.
Brief (Provided In Assessment 1)
A uniform Steel flat bar (material Modulus of Elasticity 200 GN/m2, Poisson’s Ratio 0.3) of width W 400 mm and a length of 4000 mm is restrained as appropriate at one end and under an axial tensile load of 500 KN applied to the other end face. It has been initially designed with a thickness of 50 mm. This gives a hand calculated stress value of 25 MN/m2, which is 1/8 of the material’s Yield Stress, of 200 MN/m2, giving a factor of safety of eight, which is deemed to too conservative.
The flat bar now requires stepped down in size from W to h, forming a shoulder with fillet, at the middle of the bar along its length. For a given radius of fillet, determine the (new) minimum thickness of t capable of withstanding the same tensile force with the factor of safety of four using finite element analysis. Assume Von Mises failure criterion applies, i.e. the maximum Von Mises (un-averaged) stress should not exceed 50 MN/m2.
Your final thickness must be an integer millimetre value to use standard size material.
Brief Assessment
The problem is that with a wall thickness of 50 mm the maximum stress at the radius point will be too high and is in too much risk of distorting or failing. The factor of eight is too high and needs to be reduced to a factor of four.
Brief Proposal
There are two main changeable features in this arrangement, which include the radius and the general thickness. It is assumed that changing the thickness will have a more direct effect on the results and in this scenario that is the only factor which will change. However realistically both these factors would
References: Figure 5 Stress Concentration Factors-2013. (Online) http://www.mae.ncsu.edu/eischen/courses/mae316/docs/Appendix_C.pdf Figure 6 Stress Concentration-Aaron Klapheck.-2011-2013. (Online) http://www.aaronklapheck.com/Downloads/Engr112_Handouts/ENGR112%20Solutions/02-07ChapGere%5b1%5d.pdf Calculation Hibbeler, R.C. (2011). 4.9 Residual Stress. In: Disanno, S Mechanics of Materials. Boston: Pearson Prentice Hall. p164-168.