Papers by Dimitrios Manolakos
Machines, 2022
This paper recommends an alternative designing process for a superior road racing bicycle frame m... more This paper recommends an alternative designing process for a superior road racing bicycle frame manufactured from composite materials that is much faster than typically used design processes. The main design goal is for the rider to be faster under the same riding conditions and with the same effort made. This performance gain is the result of a combined structural and aerodynamic optimization process used during the design process along with the selection of the materials. As the needs of the rider are the focus of this design proposal, the optimization can be carried out only after they are understood. The main difference in this approach compared to the typically used methodology is that, instead of analyzing the frame as a whole from the beginning of the design process and the CFD and CAE iterations, we examine each candidate part of the frame separately. After evaluating the parts’ performances, we select those that performed better to create a single frame. This final frame de...
Journal of the American Ceramic Society, 1989
Numerical analysis of surface grinding: Comparison between 2D and 3D modelling
Experimental investigation of the collapse modes and energy absorption characteristics of composite tubes
International Journal of Crashworthiness, 2009
... crush load efficiency is equal to 1.43 for the tubes made of aluminium alloy and changes from... more ... crush load efficiency is equal to 1.43 for the tubes made of aluminium alloy and changes from 1.12 and 1.18 for the composite tubes, showing a behaviour that is close to an ideal absorber.Energy absorption characteristics of tubes with M46J and T1000 carbon fibres. ...
Precision Engineering, 2011
Electrical discharge phenomena in EDM occur in a very short time period and in a very narrow spac... more Electrical discharge phenomena in EDM occur in a very short time period and in a very narrow space, thus making both observation and theoretical analysis extremely difficult. For this reason, the material removal mechanism in EDM has yet to be understood clearly. In this paper, the forming process of discharge craters in three dimensions was simulated, and material removal mechanism in EDM was analyzed using Molecular Dynamics (MD). It was found that material removal mechanism in EDM can be explained in two ways; one by vaporization and the other by the bubble explosion of superheated metals. It was also found that the metal removal efficiency is 0.02-0.05, leaving most of the melted pool resolidified. In addition, the influence of power density on the removal process was investigated, and the results showed that as the power density increases, the diameter and depth of the melted area increase, as does the metal removal efficiency. In this study, the forming mechanism of the bulge around discharge craters was also analyzed, and it was found that bulge is formed due to two mechanisms. The first is the shearing flow of the molten material caused by the extremely high pressure in the superheated material, and the second is the accumulation of the ejected material on the bulge formed by the first forming mechanism. It was also found that existence of micro pores in the workpiece material increases the depth of the discharge crater and melted area, thereby increasing the machining surface roughness. Simulation of the distribution of removed materials in the gap showed that some part of the removed material becomes debris ejected from the gap, while another part settles on the surface of the opposite electrode, and the last part returns to the surface of the electrode from which it was ejected.
Solid State Phenomena, 2017
People from all around the globe get their knees injured every day either because of severe sport... more People from all around the globe get their knees injured every day either because of severe sport accidents or because of simple misstepping. Their lives are about to change drastically and dramatically. The pain and the limitation of their movements becomes an obstacle and treatment with painkillers only postpones the problem. In these cases, medical doctors suggest Total Knee Replacement surgery, in which a knee implant replaces the damaged parts of the human injured knee in order to recover partially or fully the normal motion of the knee and therefore the everyday activities of the person in need. In over 95% of the patients who underwent a Total Knee Replacement surgery, the pain was overcome in sort amount of time, a high percentage of the kinematics of the knee were brought back to normal, and the patients were able to continue their lives. In this paper, the main purpose is to study the knee mechanics, to deconstruct the kinematics and dynamics of this complex system, to develop a new, ambitious knee implant design for severe accidents, perform simulation tests and evaluate it by the rules of the Axiomatic Design Method.
Effect of Natural Aging of 6xxx Series Extrusions on the Energy Absorbance Capacity
Materials Science Forum, 2016
In this study the influence of natural aging in energy absorbance capacity of 6xxx series extrude... more In this study the influence of natural aging in energy absorbance capacity of 6xxx series extruded profiles after artificial aging is examined by means of optical and scanning electron microscopy, quasi-static compression and tensile tests. Mobile quenched-in vacancies are found to play an important role in aging kinetics and formation of precipitate free zones (PFZs) which govern both the observed fracture modes and the resulting strength of the material signifying their important effect when maximum energy absorbance is desired. It is shown that fracture toughness of naturally aged samples is equivalent or higher compared to that of directly aged samples due to restriction of intergranular cracking.
Molecular Dynamics Study of Abrasive Grain Morphology and Orientation in Nanometric Grinding
Key Engineering Materials, 2016
A simulation of the material removal by a single abrasive grain in nanometric grinding is present... more A simulation of the material removal by a single abrasive grain in nanometric grinding is presented in this paper. Molecular Dynamics method is used for modeling the diamond grain and the copper workpiece. The Morse potential function is used to simulate the interactions between the atoms involved in the procedure. The abrasive grain follows a trajectory with decreasing depth of cut within the workpiece to simulate the interaction of the grain with the workpiece. The influence of the grain shape, being either square or rectangular, and of the orientation of the grain, where the grain has rake angle 10o, -10o and-20o, are studied. From the analysis it is apparent that both grain morphology and orientation play a significant role on chip formation, grinding forces and temperatures. With the appropriate modifications, the proposed model can be used for the simulation of various nanomachining processes and operations, in which continuum mechanics cannot be applied or experimental techni...
Mechanics of Materials, 2016
In order to perform an in-depth analysis of the failure mechanism of woven para-aramid fabrics, t... more In order to perform an in-depth analysis of the failure mechanism of woven para-aramid fabrics, the width of the specimens in this study is expressed in terms of the so-called "transverse inter-yarn nodal number". This is the number of unit cell nodes on the transverse direction, which determine the width of the specimen. This paper reveals that the latter number is closely correlated with the weaving strength and the failure mechanism mode of the afore-mentioned fabrics under tensile loading. It was found that there are two possible failure mechanisms for woven para-aramid fabrics, an inter-yarn debonding (break of the unit cell nodal bonds and abruption of the fibers) and a fracture (break of the fibers) mode, whose presence in the failure mode depends on the transverse inter-yarn nodal number. In practice, there is a critical inter-yarn nodal number for each fabric, after which a transition from debonding to fracture mechanism occurs. The afore-mentioned critical inter-yarn nodal number plays an important role on the strength of the fabric.
International Journal of Manufacturing, Materials, and Mechanical Engineering, 2016
In order to manufacture parts with dimensions of nanometres, high–technology equipment is require... more In order to manufacture parts with dimensions of nanometres, high–technology equipment is required. There is a demand to study nano-metric cutting mechanisms and phenomena appearing in this level. However, experiments are difficult to be realized, so computational methods are employed. Nano-scale cutting involves workpiece deformation in only a few atomic layers from the workpiece surface; at this scale the continuum theory cannot be used, so methods like finite elements are not sufficient. Molecular Dynamics is a method increasingly used for the simulation of nano-cutting. However, the computational cost required is quite high. In an effort to reduce the time of the analysis, high or extremely high cutting speeds are used in the models. In this paper an analysis is presented where cutting speed is studied and its influence on the chip morphology and workpiece surface is investigated, for nano-cutting modelling of Cu with diamond tools. The results indicate that cutting speed influe...
Design, Numerical Analysis and Manufacturing of Artificial Hip Joint Implants
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Forces Measurement in Turning of Femoral Heads from
Journal of Manufacturing Technology Research
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On the influence of processing conditions on surface roughness for milling titanium alloys with HSS tools
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Manufacturing processes of shape memory alloys
Materials Forming and Machining, 2016
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The effect of the heat source profile in the thermal modeling of surface grinding
Development of a Computer Software for Metal Forming Processes
In this paper a computer software is presented that allows the engineer to decide whether a metal... more In this paper a computer software is presented that allows the engineer to decide whether a metal forming process can be applied reliably and without any failure for a specific task. In particular cold bulk metal forming processes and bending are considered. The aid is offered from the proposed program through the calculation of certain parameters, like the reliability ratio, several material properties and the friction coefficient and their proper values which allow for the reliable, without failure use of these processes. Thus, it is shown to the engineer, whether a particular forming process is suitable or not for the manufacturing of a product. It is also possible that the proper parameters or a more appropriate process is selected with the aid of the proposed software. The program’s interface is developed with the use of Microsoft Visual Basic so that it is more user-friendly, in comparison to the calculation program which is developed with Fortran. An overview of the program a...
3D Modeling of Precision High Speed Turning and Milling for the Prediction of Chip Morphology using FEM
In this paper high speed turning and milling models are considered and chip formation and cutting... more In this paper high speed turning and milling models are considered and chip formation and cutting forces are investigated. For the simulation the Finite Element Modeling software Third Wave Systems AdvantEdge is employed and the cutting forces results as well as the morphology of the chip are compared with the results of experiments conducted with CNC machine tools. For the experimental work the principles for design of experiment were used in order to minimize the required amount of experiments and obtain useful results at the same time. All parameters and cutting conditions were chosen to be close to the common industrial ones, with the material of the workpiece being C45 steel and the tools being coated carbides. Although published work on FEM simulations on high speed machining exist, this paper provides validated 3D models that cover the cases of precision high speed turning and high speed milling. The validation of the numerical data with the experimental ones show a good agre...
Multiscale modelling of wear by combined use of numerical and statistical methods
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Design, Numerical Analysis and Manufacture of Radial Pump Impellers with Various Blade Geometries
International Review of Mechanical Engineering (IREME), 2015
ABSTRACT Impeller blade geometry plays a dominant role on the velocity profile of the fluid flowi... more ABSTRACT Impeller blade geometry plays a dominant role on the velocity profile of the fluid flowing through the pump. Although blades’ design is based on fluid dynamics considerations, it is sometimes limited by the available manufacturing methods, due to the required complexity in the geometry. In the present paper, the evolution of the velocity field in the blade passages of two anew designed radial pump impellers with different curvature and outlet blade angle is examined in order to verify their optimum design and characteristics. The numerical solution of the discrete three-dimensional, incompressible Navier-Stokes equations over a structured grid is accomplished with a commercial CFD finite-volume code. For each impeller, pressure and relative velocity distributions are presented and analyzed. The flow patterns in the blade passages are monitored and the mechanisms that dominate the flow field in the different regions of the impeller geometry are discussed. Furthermore, the new impellers that were tested numerically are manufactured in a CNC Milling Centre under the operation of sculptured surfaces; thus the feasibility of manufacturing the improved geometries is exhibited.
Composites Part B: Engineering, 2017
To cite this article: Junaidi, E. et al. (2019). Effect of electrophoretically deposited graphene... more To cite this article: Junaidi, E. et al. (2019). Effect of electrophoretically deposited graphene nanoplatelets on flexural properties of graphene nanoplatelets/carbon fabric/epoxy hybrid laminated composites.
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Papers by Dimitrios Manolakos