Mohamed Elbestawi

Bio: Mohamed Elbestawi is an academic researcher from McMaster University. The author has contributed to research in topics: Machining & Tool wear. The author has an hindex of 50, co-authored 210 publications receiving 7200 citations. Previous affiliations of Mohamed Elbestawi include McMaster-Carr & University of Waterloo.

Lattice Structures and Functionally Graded Materials Applications in Additive Manufacturing of Orthopedic Implants: A Review

Abstract: A major advantage of additive manufacturing (AM) technologies is the ability to print customized products, which makes these technologies well suited for the orthopedic implants industry. Another advantage is the design freedom provided by AM technologies to enhance the performance of orthopedic implants. This paper presents a state-of-the-art overview of the use of AM technologies to produce orthopedic implants from lattice structures and functionally graded materials. It discusses how both techniques can improve the implants’ performance significantly, from a mechanical and biological point of view. The characterization of lattice structures and the most recent finite element analysis models are explored. Additionally, recent case studies that use functionally graded materials in biomedical implants are surveyed. Finally, this paper reviews the challenges faced by these two applications and suggests future research directions required to improve their use in orthopedic implants.

Modelling the effects of tool-edge radius on residual stresses when orthogonal cutting AISI 316L

Abstract: Tool-edge geometry has significant effects on the cutting process, as it affects cutting forces, stresses, temperatures, deformation zone, and surface integrity. An Arbitrary-Lagrangian–Eulerian (A.L.E.) finite element model is presented here to simulate the effects of cutting-edge radius on residual stresses (R.S.) when orthogonal dry cutting austenitic stainless steel AISI 316L with continuous chip formation. Four radii were simulated starting with a sharp edge, with a finite radius, and up to a value equal to the uncut chip thickness. Residual stress profiles started with surface tensile stresses then turned to be compressive at about 140 μm from the surface; the same trend was found experimentally. Larger edge radius induced higher R.S. in both the tensile and compressive regions, while it had almost no effect on the thickness of tensile layer and pushed the maximum compressive stresses deeper into the workpiece. A stagnation zone was clearly observed when using non-sharp tools and its size increased with edge radius. The distance between the stagnation-zone tip and the machined surface increased with edge radius, which explained the increase in material plastic deformation, and compressive R.S. when using larger edge radius. Workpiece temperatures increased with edge radius; this is attributed to the increase in friction heat generation as the contact area between the tool edge and workpiece increases. Consequently, higher tensile R.S. were induced in the near-surface layer. The low thermal conductivity of AISI 316L restricted the effect of friction heat to the near-surface layer; therefore, the thickness of tensile layer was not affected.

Effect of coolant strategy on tool performance, chip morphology and surface quality during high-speed machining of A356 aluminum alloy

Abstract: This paper describes the results of application of different coolant strategies to high-speed milling of aluminum alloy A356 for automotive industry. The paper investigates the effect of flood coolant, dry cutting, and minimum quantity of lubricant (MQL) technologies on tool wear, surface roughness and cutting forces. The cutting speed range was up to 5225 m/min. The feed rate used was up to 20 m/min. The result of MQL application is compared with dry milling and milling with flood coolant application. It was found that the MQL technology could be a viable alternative to the flood coolant application. The adhesive tool wear mechanism and adhesion activated surface quality deterioration are revealed and the role of lubricant in their reduction is defined.

From the basic mechanics of orthogonal metal cutting toward the identification of the constitutive equation

Abstract: This paper proposes a methodology to identify the material coefficients of constitutive equation within the practical range of stress, strain, strain rate, and temperature encountered in metal cutting. This methodology is based on analytical modeling of the orthogonal cutting process in conjunction with orthogonal cutting experiments. The basic mechanics governing the primary shear zone have been re-evaluated for continuous chip formation process. The stress, strain, strain rate and temperature fields have been theoretically derived leading to the expressions of the effective stress, strain, strain rate, and temperature on the main shear plane. Orthogonal cutting experiments with different cutting conditions provide an evaluation of theses physical quantities. Applying the least-square approximation techniques to the resulting values yields an estimation of the material coefficients of the constitutive equation. This methodology has been applied for different materials. The good agreement between the resulting models and those obtained using the compressive split Hopkinson bar (CSHB), where available, demonstrates the effectiveness of this methodology.

Tool condition monitoring in drilling using vibration signature analysis

Abstract: This paper presents a study on monitoring tool wear and failure in drilling using vibration signature analysis techniques. Discriminant features, which are sensitive to drill wear and breakage, were developed in both time and frequency domains. These features were found to be relatively insensitive to cutting conditions, and sensor location. In the time domain, a monitoring feature based on calculating the kurtosis value of both the transverse and thrust vibrations, was found to be rather effective for on-line detection of drill breakage. On the other hand, in the frequency domain, a cepstrum ratio, derived from the spectra of the vibrations monitored in both directions, was also found effective in detecting breakage events. The effect of different types of wear on the vibration power spectra, in both the transverse and the thrust directions, was also investigated. A signature feature, namely the instantaneous ratio of the absolute mean value (RAMV i ), was developed in this study and used as a threshold for controlled capture of the vibration signal. The ability of the monitoring features to detect drill wear and breakage was verified experimentally. The drilling tests were performed using 3 and 6 mm diameter high speed steel twist drills, and cast iron workpieces. The results confirmed the effectiveness and robustness of the proposed monitoring features.

Machining induced surface integrity in titanium and nickel alloys: A review

Abstract: Titanium and nickel alloys represent a significant metal portion of the aircraft structural and engine components. When these critical structural components in aerospace industry are manufactured with the objective to reach high reliability levels, surface integrity is one of the most relevant parameters used for evaluating the quality of finish machined surfaces. The residual stresses and surface alteration (white etch layer and depth of work hardening) induced by machining of titanium alloys and nickel-based alloys are very critical due to safety and sustainability concerns. This review paper provides an overview of machining induced surface integrity in titanium and nickel alloys. There are many different types of surface integrity problems reported in literature, and among these, residual stresses, white layer and work hardening layers, as well as microstructural alterations can be studied in order to improve surface qualities of end products. Many parameters affect the surface quality of workpieces, and cutting speed, feed rate, depth of cut, tool geometry and preparation, tool wear, and workpiece properties are among the most important ones worth to investigate. Experimental and empirical studies as well as analytical and Finite Element modeling based approaches are offered in order to better understand machining induced surface integrity. In the current state-of-the-art however, a comprehensive and systematic modeling approach based on the process physics and applicable to the industrial processes is still missing. It is concluded that further modeling studies are needed to create predictive physics-based models that is in good agreement with reliable experiments, while explaining the effects of many parameters, for machining of titanium alloys and nickel-based alloys.

Sustainable manufacturing: Modeling and optimization challenges at the product, process and system levels

Abstract: Achieving sustainability in manufacturing requires a holistic view spanning not just the product, and the manufacturing processes involved in its fabrication, but also the entire supply chain, including the manufacturing systems across multiple product life-cycles. This requires improved models, metrics for sustainability evaluation, and optimization techniques at the product, process, and system levels. This paper presents an overview of recent trends and new concepts in the development of sustainable products, processes and systems. In particular, recent trends in developing improved sustainability scoring methods for products and processes, and predictive models and optimization techniques for sustainable manufacturing processes, focusing on dry, near-dry and cryogenic machining as examples, are presented.