Design of an Additive Manufactured Steel Piston for a High Performance Engine: Developing of a Numerical Methodology Based on Topology Optimization Techniques

Abstract

Reviewer: #1The authors thank the referee for his careful, constructive review and for his suggestions. The paper has been amended according to the reviewer's suggestions, and the authors feel that the present version is better and clearer. The points raised by the reviewer are separately examined in the following.Overall a good publication, with good science, and a novel topic.1) From a combustion perspective, examining piston @TDC in the combustion stroke would not represent peak pressure conditions. Normally maximum pressure should be circa 5-10deg ATDC, depending on speed/load. Regardless, I do not suggest you alter the publication, merely take this into account in further work.Actually the maximum chamber pressure (12 crank angle degrees after TDC) has been used. The authors decided to neglect the corresponding conrod tilting in order to not include in this load case the piston/liner contact interaction. The following sentence has been added at page 3 of the text: "Actually, these values have been recorded at the instant of maximum combustion pressure, which is located approximately 12 crank angle degrees after top dead centre. The connecting rod should be lightly tilted, but the authors preferred to keep it perfectly vertical to not complicate the model with the piston-liner contact interaction. Thrust forces related to the piston-liner interaction are then considered in a different specific optimization load case."2) For the 1D model validation, the model of the spark plug pressure sensor would be helpful. Also note for future reference you may have had superior correlation if you used a pressure sampling rate of 0.5 to 0.2 CAD; 1.0 CAD is acceptable but considered bordering on too low resolution to be meaningfully accurate.The authors perfectly agree with this reviewer. Indeed, the 1° crank angle (re)sapling has been adopted only for load estimation in the mechanical analysis. A finer resolution has been adopted in 1-D cfd analysis which are out of the scope of the present contribution. The following sentence has been modified in the text at page 3: "Both the acceleration and the gas pressure were resampled in 1° crankshaft angle steps for the structural analysis, and the corresponding values were employed for the different piston positions considered."3) You propose the peak temperature of the piston was simulated to be 280C, in my experience this is very high, and may be beyond the material capability of a stock Al piston. Without any information to correlate this as reasonable it puts the validation of the model into question: If the engine could not sustain the temperature the CFD is claiming, then the model may not be representative."Actually, an experimental campaign in order to validate the thermal model has not been performed for the specific engine under investigation. Nevertheless, the methodology employed Reviewer 1Click here to download Manuscript Rep1.docx

Technological Feasibility of Lattice Materials by Laser-Based Powder Bed Fusion of A357.0

“…3 Using as little material as possible is particularly important in automotive and aerospace industries, where any mass saving, also minimal, brings about a sensible reduction in cost and often an increase in performance. [4][5][6] For this reason, attempts have been made to scale the lattice optimization approach to the design of macroscale structures such as the piston of an internal combustion engine 7 or even the automotive chassis. 8 However, lattice materials have many other applications, such as heat exchangers, energy absorbers, biomedical devices, and thermal and acoustic insulators.…”

Synergy between topology optimization and additive manufacturing in the automotive field

“…The elements with intermediate density were thus penalized to achieve a well-comprehensible loading path solution. 28 The selected design space was subjected to three optimizations, each of which considered one of the three loadcases, that is, cornering, bumping and braking. The redesign was performed by critically analyzing the results of each loading condition on the TO results, emphasizing thus the influence of the three loading conditions on the final design.…”

“…In this contribution, a methodology similar to the one presented by Barbieri et al 27,28 and Mantovani et al 29 was applied to determine the optimal material distribution for an upright to be produced in aluminum alloy by laser-powder bed fusion (L-PBF). 30 L-PBF discloses extreme freedom in geometry, which also enables the production of the complicated shapes resulting from TO.…”

Titanium alloy piston thermo-mechanical coupling simulation and multi-objective optimization design

“…Because the piston analysis involves a variety of physical fields and needs to meet multiple performance objectives, Patel et al 26 carried out a multi-objective optimization design and obtained the optimal solution. Barbieri et al 27 replaced the piston materials, optimized the piston design under three loading conditions by using the topological optimization method, and corrected and verified the geometry of the piston design. Bhuiyan et al 28 carried out the finite element analysis of the piston and optimized the piston groove structure.…”