Dynamic Lifecycle Cost Modeling for Adaptable Design Optimization of Additively Remanufactured Aeroengine Components

Round 1

Reviewer 1 Report

The authors propose to create an LCC model for parts repaired with AM and demonstrate the use of the LCC model with a case study consisting of turbine repair.

The literature gap presented by the authors is very convincing. Although LCC models of some sort have undoubtedly been used by companies repairing their own turbines with DED, I am not aware of an LCC model that has been made public.

The LCC model has been developed expressly for the application presented by the authors and therefore I wonder if it has certain limitations for other uses. The authors make it clear already in the title of the article that the LCC model is for aircraft engine components, but the article could benefit from a short speculation of how the model could be used for other types of components repaired with AM.

The literature review of research concerning AM costs is exceptionally well constructed.

The use of English in the article is excellent and it is presented in a very clear manner.

 

Detailed comments:

 

Additive manufacturing consists of a variety of technologies (current standard terminology lists 7 distinct categories). While it is clear to readers familiar with the field that "Additive manufacturing" here refers to directed energy deposition and/or metal powder bed fusion, readers who are less familiar might be misled. The issue is resolved at the beginning of page 7, but it could be beneficial to explain which AM technologies authors are referring to at the very beginning of the article.

The significance of P1 and P2 are possible to interpret from the text preceding figures 1-3 but it would increase comprehension if P1 and P2 were mentioned in the text. Also, the figures could perhaps be unified into one figure for clearer comparison.

 

In equation 3, variable and fixed costs are presented. It could be beneficial to know at this stage what costs the authors consider as fixed costs for repair by AM. Additionally, the variable costs are "per cycle", the meaning of which is not entirely clear to me.

In equation 4, it is unclear to me why W_TRS is used instead of W_total.

In equation 8, the values of alpha, beta, and gamma are indeed specified in table 1, but their definitions are not.

 

I am unsure if I understand the "replace" component of the model correctly. Is the entire TRS replaced at certain points? If so, why is it not instead repaired with AM?

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

This appears to be a good paper on a topic of high interest. My major problem is the review time for a paper like this is too short. It has a lot of assumptions and formulae that need to be analyzed closely. There just isn't enough time to do that.

That said, there's a lot to like about the paper. I think the authors show that AM deposited stiffener decreases LCC. I think maybe they could reduce the complexity of their analysis. I question that historical fuel costs can be used to predict future fuel costs. I don't know what the 173 in their repair costs represent. I also wonder whether changing some of these assumptions might change their conclusion.

So I like the paper. I believe AM can help LCC. I just wish this was presented in a simpler fashion, but maybe that's not possible.

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

The addressed topic of dynamic lifecycle cost modeling for adaptable design optimization is very interesting and may have impact on how mechanical systems are designed in the future. The focus is on additive manufacturing but it can be generalized to any other manufacturing process and their impact on the overall cost. As the life of product depends on many factors and its residual life can have significant impact on the safety one can only be very cautious in terms of the applicability of the approach. It is certainly interesting as a concept and deserves study with hope that it will have long term benefits as other issues are taken into consideration.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf