High Precision Micro-Grinding of Advanced Materials
Doctoral thesis, 2021

The aim of this thesis is to advance a fundamental understanding of process mechanics and surface integrity in micro-grinding of advanced materials, such as additively and conventionally manufactured titanium and engineering ceramic. Grinding forces and specific grinding energy were chosen as the two most important indicators to investigate the process. The surface integrity was evaluated using X-ray diffraction measurements to quantify residual stresses, surface roughness measurements, SEM microscopy, and confocal images. At the first stage, the influence of different micro-grinding and dressing parameters and different tool specifications was examined. Then, via process modelling, the outcome of the micro-grinding process at different chip thicknesses and aggressiveness numbers was studied. Additionally, a hybrid laser-assisted micro-grinding process was developed to improve the process efficiency.

The results show that the flow stress of the material did not change with the changing of cutting speed and cutting strain rate. Moreover, it was observed that the depth of cut and grinding feed rate had the same (neutral) effect on the resultant grinding forces. Therefore, the efficiency of titanium micro-grinding could be highly influenced by changing the topography of the micro-grinding tool through different dressing parameters. However, using higher chip thicknesses resulted in a more efficient process in terms of cutting/chip-formation. The lowest specific energy, obtained in the single grain tests, was 11.5 J/mm3 for both-types of titanium materials. In contrast, a much higher minimum specific energy in real micro-grinding process with several (bonded) grains was observed – showing a higher amount of ploughing and rubbing/friction in the micro-grinding process. The build-up direction of additively-manufactured titanium, at low chip thickness, affected the process efficiency. In larger chip thicknesses, almost the same specific energy was measured independent of the material manufacturing method. The results of the XRD analysis showed that contrary to the specific grinding energy, the residual stresses of the ground surface changed by varying the cutting speed and feed-rate-to-depth-of-cut ratio, vw/ae. Higher cutting speeds resulted in lower compressive residual stress, and higher feed-rate-to-depth-of-cut ratios resulted in higher compressive stresses. This can be attributed to higher temperatures in the chip-formation process compared to the plastic deformation in micro-grinding at higher cutting speeds and lower vw/ae ratios, which was proved via SEM micrographs. A more efficient micro-grinding process was achieved via the Laser-Assisted Micro-Grinding (LAMG) process of a Si3N4 workpiece, where the values of the specific grinding energy, as well as the tool deflection by the LAMG process, were much lower than the Conventional Micro-Grinding (CMG) process.

Modeling

Micro-grinding

Process efficiency

Titanium

Additive manufacturing

Ceramic

Surface integrity

Laser-assisted micro-grinding

Online via Zoom
Opponent: Jan C. Aurich, Prof. Dr.-Ing, University of Kaiserslautern, Germany

Author

Mohammadali Kadivar

Chalmers, Industrial and Materials Science, Materials and manufacture

The effect of dressing parameters on micro-grinding of titanium alloy

Precision Engineering,; Vol. 51(2018)p. 176-185

Journal article

Modeling of the micro-grinding process considering the grinding tool topography

International Journal of Abrasive Technology,; Vol. 8(2017)p. 157-170

Journal article

Laser-assisted micro-grinding of Si3N4

Precision Engineering,; Vol. 60(2019)p. 394-404

Journal article

Performance of micro-grinding pins with different bonding while micro-grinding Si3N4

International Journal of Abrasive Technology,; Vol. 10(2020)p. 16-31

Journal article

Modeling of micro-grinding forces considering dressing parameters and tool deflection

Precision Engineering,; Vol. 67(2021)p. 269-281

Journal article

The role of specific energy in micro-grinding of titanium alloy

Precision Engineering,; Vol. 72(2021)p. 172-183

Journal article

Micro-grinding is considered a promising method to produce high-quality parts. However, fundamental investigations into the application of micro-grinding are essential to further develop and understand the technology and meet industrial requirements.

A fundamental investigation was carried out to explore the aspects of grindability (machinability) for advanced materials produced by distinct manufacturing methods, like additive manufacturing and conventional method, from the perspective of grinding forces, specific energy, and surface integrity. This study aimed to understand the effects of process parameters, i.e., cutting speed, the ratio of feed rate to depth of cut, different lubrication conditions and grinding tool topography and its specification on grindability of titanium and silicon nitride (Si3N4). The specific grinding energy is used as a major indicator of grindability in this study. Moreover, in order to achieve a highly precise and effective micro-grinding process, the surface integrity was analyzed in addition to the specific grinding energy.

The research provides a closer look in the micro-grinding process via experimental investigation and modeling studies to find the interaction mechanisms in micro-grinding of ductile and brittle materials for an accurate and efficient process. The present thesis is planned for both academic and industry parties. Researchers can obtain inspiration from the literature analysis through various scientific disciplines, and the effect of fundamental process parameters like chip thickness in process efficiency. Industrial experts can reflect on the role of process parameters in micro-grinding of advanced materials to produce accurate micro-parts without or with minimum surface and subsurface damages.

Subject Categories

Mechanical Engineering

Production Engineering, Human Work Science and Ergonomics

Areas of Advance

Production

ISBN

978-91-7905-457-1

Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 4924

Publisher

Chalmers University of Technology

Online via Zoom

Online

Opponent: Jan C. Aurich, Prof. Dr.-Ing, University of Kaiserslautern, Germany

More information

Latest update

5/6/2021 2