Finite Element Analysis of Thermal Stress and Thermal Deformation in Typical Part during SLM

Round 1

Reviewer 1 Report

My comments to this paper are listed as follows,

Where did you apply Eqs. (4) and (5) in your model?

The expression of Eq. (11) is not correct.

Does your mechanical simulation include plastic strain or just based on elastic model. If you considered the plastic strain, please discussed more in detail.

In section 2.5, you name this section as boundary conditions. I think this is your initial condition instead of boundary condition.

What is your boundary condition in your thermal and mechanical model? Did you consider the convection or radiation in your model or not?

In Fig.3 you mentioned cooling fin, how you consider the effect of these cooling fin in your model?

I think this paper is lack of originality and the model developed here is not something very new. Only one case study was carried out by using the model.

 

Author Response

Thank you very much for the comments and suggestions. We have attached an attachment about the changes.

Author Response File: Author Response.docx

Reviewer 2 Report

Thermal induced deformation, as well as cracking due to high residual stresses account for numerous problems in PBF technologies. Thus, placing the study in an area of high demand and need for additional research.

While the topic is of high interest, the work does need substantial improvements to meet the standards for a publication. Foremost the use of the English language needs to be improved in both, grammar and wording. Examples would be condensation on page 2, which probably should be consolidation. Likewise, the phrase SLM melting does not make sense, since the “M” already stands for melting.

Another formal point is to use appropriate keywords. Keywords which are in the title shouldn’t be used in the keyword section. It’s advised to list either synonyms or additional details in keywords, which will enhance the visibility of the article and improve the effectiveness of search engines.

 

In addition to the formal remarks, the content as such needs to be improved as well. Foremost the use of appropriate words. An example would be the correct use of sintering and melting. In the common language sintering and melting are often confused as far as 3D printing applications are concerned. However, there is a clear definition of what sintering and melting is. I’d advise you to have a look at the explanations provided in recent review articles about various AM techniques and the agreed nomenclature outlined in the according standard.

L. Hitzler, M. Merkel, W. Hall, A. Öchsner, A Review of Metal Fabricated with Laser- and Powder-Bed Based Additive Manufacturing Techniques: Process, Nomenclature, Materials, Achievable Properties, and its Utilization in the Medical Sector, Adv. Eng. Mater. 20(5) (2018) 1700658.

T. DebRoy, H.L. Wei, J.S. Zuback, T. Mukherjee, J.W. Elmer, J.O. Milewski, A.M. Beese, A. Wilson-Heid, A. De, W. Zhang, Additive manufacturing of metallic components – Process, structure and properties, Prog. Mater. Sci. 92 (2018) 112-224.

ISO/ASME International, ISO/ASTM 52900, Additive Manufacturing-General Principles-Terminology

The mentioned review addresses the thermal envelope too, and it is worth mentioning that, unlike what’s stated in your manuscript, the heat conductivity in the powder bed is magnitudes lower than via the solidified material. The highest fractions are transferred via the solid connection, and for very high temperatures also via radiation.

 

Regarding the choice of the material parameters, please note that the mechanical properties of printed 316L are by no means isotropic, especially not when only a single layer is concerned. It is understandable that for a first simulation it may be viable to use an isotropic material, but at least point out that this is a simplification and does not reflect the reality.

See anisotropy of 316L in terms of inclination angle and chosen irradiation strategy.

L. Hitzler, J. Hirsch, B. Heine, M. Merkel, W. Hall, A. Öchsner, On the Anisotropic Mechanical Properties of Selective Laser Melted Stainless Steel, Materials 10(10) (2017) 1136.

L. Hitzler, J. Hirsch, J. Tomas, M. Merkel, W. Hall, A. Öchsner, In-plane Anisotropy of Selective Laser Melted Stainless Steel: The Importance of the Rotation Angle Increment and the Limitation Window, P. I. Mech. Eng. L: J. Mat. ONLINE FIRST (2018).

For understanding of the differences to conventionally processed material, see the explanations of how and why a metastabile microstructure is formed during SLM:

Metastabile microstructures resulting of SLM:

K.G. Prashanth, J. Eckert, Formation of metastable cellular microstructures in selective laser melted alloys, J. Alloys Compd. 707 (2017) 27-34.

 

An additional remark on the chosen material characteristics for the simulation is to use a temperature dependent yield strength for 316L, since pre-stressed areas in layers underneath the current built will experience temperatures high enough to allow for plastic deformation due to lowered yield strength and correspondingly a relaxation of residual stresses. Please explain why this has been neglected and comment on the suitability of your approach.

 

Lastly a few remarks on the included figures:

Fig. 6: on substrate versus after removal? -> diagram legend should match description

Depicted units in Fig. 10b? – for better comparison and for consistency it is advised to change the bar chart in 10b to two xy diagrams (like all the others) comparing the simulation results with the experimental data, once for the on substrate case and once for the removed case.

 

Author Response

Dear Reviewer,

Thank you very much for the comments and suggestions. We have attached an attachment about the response.

Authors

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

All my concerns were well addressed. I suggest acceptance.

Reviewer 2 Report

Implemented changes in the amended manuscript are reasonable and addressed the comments.

Present form is recommended for publication.