K.-D. Bouzakis

Aristotle University of Thessaloniki | AUTH · School of Mechanical Engineering

The softening of cemented carbide at the elevated temperature of MTCVD processes results in significant reduction of their strength, and thus, high coating deformation during cutting. In this way, at interrupted cutting loads, as during turning cast iron, the cutting performance of MTCVD coated cemented carbide inserts degrades due to premature coa...

Micro-crystalline diamond (MCD) coatings were deposited on cemented carbide inserts at different temperatures using hot filament chemical vapor deposition technique. For investigating the effect of the developed diamond crystallinity on the fatigue strength and wear behaviour of the prepared MCD coated inserts, inclined impact tests and milling inv...

PVD coatings were deposited at various bias voltages on cemented carbide inserts. The coating's mechanical properties, fatigue and adhesion were determined via FEM-supported evaluation of nanoindentation, perpendicular and inclined impact test results. The coated inserts were applied in milling hardened and normalized steel. For explaining the wear...

The potential of coated cutting inserts to withstand effectively cutting loads depends among others on the coating's mechanical properties and adhesion. These data are strongly affected by the applied PVD process parameters, even if the coatings comprise the same chemical composition. Hereupon, one significant parameter is the bias voltage during t...

The evolution of the coating deposition technologies led, among others, to the production of nano-structured coatings. Such coatings are often deposited on cutting tools since they contribute to an impressive enhancement of the coated tool life. Hereupon, attention has to be given for avoiding a rapid crack propagation due to a potential coating br...

The effective application of laser machining for manufacturing the cutting edge roundness of cemented carbide inserts was investigated in a cooperative work of the Scientific Technical Committee (STC) “Cutting” of the International Academy for Production Engineering (CIRP). Machining with diverse laser beam pulsing duration and feed velocity as wel...

This paper analyzes the dynamical behavior of a six-bar linkage used in mechanical presses for metal forming such as deep drawing. In the under study mechanism, a four-bar linkage is connected to a slider through an articulated binary link. The motion of the six-bar linkage is studied by kinematic analysis developing an analytical method. Furthermo...

Roll tensioning is a common method for increasing locally the superficial strength of thin circular saws and in this way their dynamic stability. Through roll tensioning, residual stresses are induced into the disc material leading to a significant enhancement of its dynamic stiffness. In this paper, a FEM-methodology is proposed for determining th...

Coated cemented carbide inserts with diverse compressive residual stresses in the film structure were manufactured applying different substrate bias voltages. Moreover, a portion of the coated specimens was annealed for eliminating compressive residual stresses. Residual stress measurements, nanoindentations, nano- and inclined-impact tests, as wel...

The cutting performance of PVD coated tools can be significantly improved by applying optimized PVD processes, film architectures, as well as appropriate pre-and post-treatments of the substrates and coated surfaces respectively. Substrate pre-treatments aim, among others, at improving the coating adhesion. In this way, lower coating loads develop...

The paper aims at clarifying whether thick HPPMS (High Power Pulsed Magnetron Sputtering) PVD coatings can be used more effectively in cutting processes compared to thin ones. In this context, nano-structured multilayer HPPMS PVD coatings with diverse thickness were deposited on cemented carbide inserts of the same specifications. The deposition of...

The stereo geometry and the colors of the Parthenon west frieze carved blocks exhibited in the Acropolis Museum of Athens (AMA) were captured by laser scanning. Considering the large size and weight of the frieze blocks fixed in permanent positions, a portable laser scanner supported by convenient software was used. This technique is flexible in fa...

Tool coatings gain increasing importance in production industry. In machining coatings allow for tools which possess high toughness and high hardness at the same time. Therefore, they provide a significant increase in productivity and tool life. Coatings can be applied to reduce adhesion and abrasion, for thermal insulation and to increase chemical...

The effect of PVD coating's residual stresses on their mechanical properties, brittleness and adhesion is presented. Coated cemented carbide inserts possessing diverse residual stress distributions in the film structure were manufactured applying different substrate bias voltages. As a consequence, compressive residual stresses are developed in the...

This article deals with the wear mechanisms of variously adherent nano-composite or multi-layer diamond coated tools in milling. The adhesion and residual stresses of these films on cemented-carbide inserts were characterized via inclined impact tests at diverse temperatures. The obtained results were evaluated through FEM-supported mathematical me...

Methods for inspecting coating mechanical properties and adhesion on final products, considering quantitative criteria are of high importance. In this paper, relevant characteristic examples for determining the adhesion of a MoN and a TiC PVD coating deposited on steel substrate are introduced. The mechanical properties of the coatings and their st...

The interface fatigue strength of coated tools with nano-crystalline diamond (NCD) coatings affects their milling performance. Depending on the developed cutting loads and temperatures, the repetitive impacts on the tool deteriorate progressively the coating-substrate interface strength, thus influencing the effective NCD film adhesion. Aiming at a...

The determination of the temperature dependent interface fatigue strength of Nano-Crystalline Diamond (NCD) coatings facilitates a thorough understanding of the NCD coated cutting tools wear mechanisms. In the present paper, the fatigue strength of the interface region between a NCD film and its hardmetal substrate was investigated by inclined impa...

During the Future Advanced Rotorcraft Drive System (FARDS) program, the Aviation Development Directorate (ADD), Aviation Applied Technology Directorate (AATD), Bell Helicopter Textron Inc., University of Toledo and the Aristotle University of Thessaloniki worked together to perform bearing coating tests. The mechanical properties of the DLC coating...

Nano-impact test is a reliable method for assessing the brittleness of PVD coatings with mono- or multi-layer structures. For the analytical description of this test, an axis-symmetrical Finite Element Method (FEM) model was developed using the LS-DYNA software. This software was adequate to simulate the progressive superficial coating fracture ind...

This paper analyses the dynamical behaviour of a six-bar linkage used in mechanical presses for metal forming. In the under study mechanism, a four-bar linkage is connected to a slider-crank four-bar linkage by a double joint. The motion of the six-bar linkage is studied by kinematic analysis developing an analytical method. Furthermore, using an i...

The cutting performance of coated tools can be significantly improved by tailoring the compound film-interface-substrate properties to specific application requirements. In the paper, examples highlight such innovative procedures, facilitating the adaption of cutting conditions to the film properties. The fatigue strength of PVD-films at high strai...

The effect of brittleness and fatigue of mono- and multi-layer PVD films on coated tools cutting performance is introduced. Cemented carbide inserts were coated to the same overall film thickness with various numbers of layers. Nanoindentations were conducted to evaluate the hardness of the diverse coating structures. The film brittleness and fatig...

The effect of two different treatments of cemented carbide substrates, prior to the deposition of a nanocrystalline diamond (NCD) coating, on the film interface fatigue strength was investigated at ambient and elevated temperatures. The first substrate treatment of the cemented carbide substrate was a selective chemical Co-etching and the second on...

The investigation of archaeological findings often requires the precise recording of their solid geometry and internal structure. This paper presents innovative methods for modeling archaeological findings with complex geometry without any physical contact with the object of avoiding the risk of corruption of the object. More specific shows the rec...

This paper presents the investigation of in scale production of Parthenon frieze stones by rapid prototyping methods. Various rapid prototyping methods were considered and the most economic one was selected. Additionally, the incomplete relief surfaces of the Parthenon frieze stones were fixed and solid models were created. All sixteen stones of th...

This paper describes the construction of 3D-solid model of an antique anathem, a battleship discovered in Erechthion of Acropolis of Athens. The anathem was scanned by 3D-laser scanning methods. The point cloud acquired was further used for creating the 3D surface model of the battleship. In order to create a 3D- solid model this surface was divide...

In this paper the determination of the bulk geometry of Parthenon West Frieze stones is presented by evaluating laser scanning measurements of their surfaces. Moreover based on existing measurements of the West Frieze vertical curvature, the effect of the curvature on the architraves and stone geometry was estimated. Considering these data, a corre...

The knowledge of coated tool wear mechanisms in milling is crucial for explaining film failure and adjusting appropriately the cutting conditions. In the described research, coated cemented carbide inserts were applied in up-and down-milling stainless steel for monitoring the tool wear at repetitive cutting loads of various magnitudes and durations...

The cutting edges of coated tools are commonly treated in separate production steps during tool manufacturing. Various methods can be employed, focusing on the cutting edge strengthening by its rounding or by more complicated geometries including chamfer and optimized tool wedge radius and angles. The efficiency of diverse cutting edge preparations...

Coated cemented carbide inserts were applied in up-and down-milling stainless steel for monitoring the tool wear at repetitive cutting loads of various magnitudes and durations. Via impact tests with adjustable force signal characteristics, the applied loads can simulate the developed ones in milling when the cutting edge penetrates the workpiece....

The fatigue strength of the cutting edge affects dominantly the tool life, especially in the interrupted material removal processes. The cutting edge fatigue of uncoated and coated tools can be effectively assessed by the repetitive impact test. Cemented carbide inserts of various grain size, surface roughness, coating and heat treatment were inves...

The coated tool wear evolution in milling at constant cutting conditions can be described analytically based among other factors on the cutting edge entry impact duration. A tool wear predictive mathematical model for milling parts of complicated geometry was created employing this methodology and a commercial CAM system. Parameters of the develope...

The inclined impact test is an efficient method for characterizing the fatigue strength of interfaces of nanocrystalline diamond coatings (NCD). During this test, an oscillating oblique load induces repetitive shear stresses into the region between film and its substrate. Inclined impact tests were conducted on NCD coated specimens with a thickness...

The paper investigates the effect of Si content on TiAlSiN, TiSiN and TiAIN/TiSiN films mechanical strength, brittleness, fatigue and adhesion. The films used were deposited on cemented carbide inserts by employing cathodic arc evaporation. For determining coating strength properties, nanoindentations were carried out. Based on the data acquired an...

The optimum design of a cam mechanism is a time consuming task, due to the numerous alternatives considerations. In the present work, the problem of design parameters optimization of a cam mechanism with translating flatface follower is investigated from a multi-objective point of view. The design parameters, just like the cam base circle radius, t...

The mechanical behaviour of nanocomposite materials with multiwall carbon nanotube (MWCNT) reinforcements is investigated in the present paper. Epoxy nanocomposites with different weight percentages of carbon nanotubes have been characterized following tensile tests and nanoindentations. The objective of this work was to investigate the efficiency...

In the described investigations, nano-impact tests were conducted on PVD films with graded mechanical properties. The properties gradation was induced by micro-blasting at different pressures for constant duration. Micro-blasting improves the film mechanical properties due to the induced residual compressive stresses into the coating structure. The...

The grain size of coated cemented carbide tools may significantly affect the tool life by influencing either the coating adhesion to the substrate or the coating growth during deposition. In the present study three variously grained cemented carbides were coated with two different PVD films. Various pre- and post-treatments were applied, while thei...

The knowledge of coated tool wear mechanisms in milling is central for explaining the film failure and selecting the appropriate cutting strategy and conditions. The described tool wear investigations in up and down milling were carried out at various cutting conditions, by coated cemented carbide inserts fixed on tool holders of different diameter...

The knowledge of coated tool wear mechanisms in milling is crucial for explaining film failure and adjusting appropriately the cutting conditions. In the described research, coated cemented carbide inserts were applied in up- and down-milling stainless steel for monitoring the tool wear at repetitive cutting loads of various magnitudes and duration...

The knowledge of coated tool wear mechanisms in milling is pivotal for explaining the film failure and selecting the appropriate cutting strategy and conditions. In this paper, tool wear experiments were carried out in milling of four different steels using coated cemented carbide inserts. The variable stress, strain and strain rate fields develope...

Significant tool life improvements are attained by the application of harder and more wear-resistant materials and coating systems. In this context, the tools’ cutting edges affect directly the overall tool performance. In this paper, by impact tests at the cutting edge vicinity, a quick assessment of the cutting edge fatigue behavior of coated and...

Nanoindentation is an effective technique for determining mechanical properties of bulk materials and thin films. Prevailing measurement uncertainties in nanoindentations by Vickers or Berkovich diamond pyramids are commonly caused by manufacturing imperfections of the indenter's side angles and tip sharpness. Moreover, the tip geometry changes ove...

In the described investigations, nano-impact tests were conducted on PVD film surfaces previously subjected to micro-blasting at different pressures for constant duration. Micro-blasting improves the film mechanical properties due to the induced residual compressive stresses into the coating structure. The film mechanical properties as well as the...

Milling operations are associated with significant tool impact loads. In the present investigations, coated carbide inserts were employed in down and up milling hardened steel, at appropriate cutting conditions and tool diameters, for attaining various cutting edge entry impact durations (CEEID). The unexpected tool life improvement in up milling,...

Physical vapor deposition (PVD) coated surfaces are often subjected to repetitive impact loads. In such cases, the strain rate’s effect on the coating fatigue failure is pivotal. This effect was investigated via a novel impact tester which facilitates the modulation of the applied impact force versus the time through an adjustable piezoelectric act...

The knowledge of coated tool wear mechanisms in milling is crucial for explaining film failure and adjusting appropriately the cutting conditions. In the described research, coated cemented carbide inserts were applied in up-and down-milling stainless steel for monitoring the tool wear at repetitive cutting loads of various magnitudes and durations...

In the present paper an evolution of a hybrid optimization method is described to find the geometric design parameters and the joint angles when some end-effector poses are prescribed. The problem is solved by minimizing the sum of the deviation squares between the prescribed poses and the real poses of the considered end-effector. The evolution of...

Rheological properties of aluminum are among others required in FEM supported calculations of thixo-forming processes. In the present paper, an analytical–experimental method is introduced to acquire such properties as a function of temperature and flow velocity. This method is based on isothermal compressive tests’ results evaluation at various te...

Coated tools are almost always applied in cutting processes. As significant conditions for improving the coated tools’ performance, enhanced film adhesion and mechanical properties are also required. To meet these requirements, appropriate substrate and film- treatments can be employed. Furthermore, since impact loads with variable duration at vari...

Nanoindentation is usually applied on thin films at ambient temperatures for hardness determination. Recently, instruments for conducting nanoindentation at elevated temperatures have been developed facilitating measurements up to 700 °C. Both indenter and specimen, if necessary, are heated in an inert atmosphere to avoid film oxidations. In the de...

The die and mold industry registers nowadays a significant growth due to current developments among others in the sectors of energy and aerospace. The manufacturing procedure of dies and molds primarily includes milling operations, which are commonly linked to complicated chip geometry and contact conditions between tool and workpiece. Therefore, t...

The cutting performance of coated tools can be significantly improved by tailoring the coatings properties to application of specific requirements. For achieving this target, optimised PVD processes as well as appropriate substrate pre- and posttreatments of the coated surfaces have to be employed. To check the effectiveness of all these methods, i...

Milling operations for manufacturing dies and molds are commonly linked to complicated chip geometry and contact conditions between tool and workpiece. these parameters render the optimisation of the cutting conditions and the de- scription of the tool wear difficult. In the described experiments, coated cemented carbide inserts fixed on a milling...

aBsTracT conventional ball valves are based on elastomeric sealing technologies which exhibit restricted wear resistance in the presence of network impurities while re-quiring high operating torques. in the described investigations, the elastomeric sealing of a 2-inch floating ball valve was replaced by a metal-to-metal seating for attaining specif...

Tests of physical vapour deposition (PVD) coatings performed in the past at NASA Glenn Research Center (GRC) in real fluid film bearing environment revealed inconsistencies in coating behaviour. Currently, a new lot of bearings with an improved diamond-like carbon (DLC) coating was tested. The oil-off tests revealed an improved coating performance...

The development of various coatings on cutting tools has met wide approval and has emerged as the major method of improving tool cutting performance. On the one hand, this positive result has been attained by applying enhanced coating materials and deposition methods, and on the other, through the employment of cemented carbide substrates with elev...

In the present paper an optimisation algorithm is described to find out the geometric design parameters of an open loop spatial robot with 3 revolute joints in the presence of geometric restrictions of the links. The design variables include the base position, the geometry of the links and the joint angles of the robot and are calculated so that th...

The performance of physical vapour deposition (PVD) films depends on the operational mechanical and thermal loads of coated tools or components. To withstand these loads, sufficient film strength properties, at ambient and elevated temperatures are required. The present paper deals with the mechanical properties and the impact resistance of cemente...

The eternal goal increasing the productivity in gear manufacturing can be obtained, among others, by efficient process planning systems. Gear manufacturing is associated with complicated generating kinematics, chip formation and tool wear mechanisms. In the present paper the number of cuts per coated tool tooth in a generating position, up to the f...

In order to determine the bond strength between adhesive and adherent it is important the knowledge of the mechanical properties of the particular epoxy resin. The increasing use of such adhesives at the level of industrial applications requires the control of their chemical and physical properties where improved adhesion strength occurs, retaining...

The Heracles General Cement Co used Finite Elements Method (FEM) to detect the reasons for vibrations in the region of the two pinion girth gear housing basements at its Halkis plant. Based on these computational results, a redesign of the driving pinions housing basements was conducted, achieving a mill operation at a low vibration level, which wa...

The applied grains’ material in micro-blasting of Physical Vapour Deposition (PVD) films and the process conditions affect significantly the coated tools’ cutting performance. Through micro-blasting, compressive stresses are induced into the film, thus increasing the coating hardness, but its brittleness too. Simultaneously, abrasion phenomena are...

Coated tools with PVD-films of almost the same mechanical properties may perform differently. This effect can be attributed to the film adhesion. For highlighting this phenomenon, the adhesion of coatings with practically identical mechanical properties deposited on cemented carbide and powder metallurgical high speed steel inserts was quantified b...

Velocity is probably the most important parameter in manufacturing, influencing performance, cost, productivity, energy and resources efficiency as well as safety and environmental issues. This paper presents basic phenomena as well as other important effects which are linked to velocity as a process parameter. In addition, applications, for exampl...

If the film of a coated part deforms plastically due to operational loads, residual stresses (RS) develop in the coating after the load removal. In this way, the film mechanical properties change induced by endogenous reasons, i.e. by the coating crystalline structure plastic deformation. Moreover, if only the substrate deforms plastically, the coa...

Nano-impact test on PVD coatings is an efficient method for investigating film failure mechanisms. During this test, the coating is subjected to repetitive impacts by a diamond indenter, inducing high local deformations and stresses into the film material, which may lead to coating failure.In the paper, coated specimens with a TiAlN PVD film were i...

Precision glass molding is a technology for the medium to large scale production of complex optical components with high surface quality and form accuracy. However, the process is only economically viable if a long lifetime of the molding tools can be guaranteed. This can be achieved by using protective coatings on the optical surfaces of the moldi...

The die and mold industry registers nowadays a significant growth, due to current developments among others in the sectors of energy and aerospace. The manufacturing procedure of dies and molds primarily includes milling operations, which are commonly linked to complicated chip geometry and contact conditions between tool and workpiece. Therefore,...

The surface response of metals subjected to cyclic loading depends on various parameters such as material properties, temperature, load data, etc.. For determining strain rate based material properties, an impact tester was developed, facilitating the impact force modulation concerning its signal pattern. This device consists of a high rigidity bas...

For investigating the effect of strain rate on the surface response and film fatigue fracture of coated specimens subjected to cyclic impact loads, an impact tester was developed, facilitating the impact force modulation concerning its signal pattern. This device consists of a high rigidity base, a linear drive supported by appropriate electronic e...

Milling operations for manufacturing dies and molds are commonly linked to complicated chip geometry and contact conditions between tool and workpiece. These parameters render the optimization of the cutting conditions and the description of the tool wear difficult. In the described experiments, coated cemented carbide inserts fixed on a milling cu...

The cutting performance of coated tools can be significantly improved by tailoring the coatings properties to application specific requirements. For achieving this target, optimized PVD processes as well as appropriate substrate pre-and post-treatments of the coated surfaces have to be employed. To check the effectiveness of all these methods, inno...

Nanoindentation is an effective technique to determine mechanical properties of bulk materials and thin films. The prevailing measurement uncertainties in nanoindentation are induced by manufacturing inaccuracies of the indenter tip. Vickers indenters are not ideally pyramidal since their tips are always not exactly sharp and the tip geometry chang...

The effective conduct of thixo-forming, presumes homogeneously heated thixotropic material billets. During heating of cylindrical aluminium parts up to their semi-solid state, the material undergoes a superficial heating, electromagnetically induced by a surrounding helical induction coil. Numerous analytical-heuristic methods have been developed f...

The mechanical properties of aluminum alloys with globular microstructure were determined by FEM based analytical evaluation of compression test results at semi-solid material state. The stress - strain - strain rate curves at thixo temperatures were determined via a comparison of the measured compression force versus time to the FEM calculated one...

Aircraft aluminum alloy 2024 T3 specimens have been subjected to constant amplitude fatigue loading at R=0.1. During fatigue, an appreciable increase of the surface hardness of the material at the meso-scale can be observed and captured by means of nanoindentations. Surface hardness increases with increasing fatigue stress amplitude and advancing n...

Precision glass molding is the technology of choice for the production of complex-shaped optical components. Protective coatings can significantly extend the lifetime of the molding tools, but the coating properties have to be exactly customized for the individual application conditions, or else an improvement in the tool performance cannot be guar...

Growing cost reduction trends in machining applications has led to a significant increase of cutting speeds and process temperatures. In this way, oxidation and diffusion mechanisms in the contact area between chip and tool become substantial, affecting the tool performance.In this paper, diffusion and oxidation interactions at 800 °C among various...

Rheological properties of aluminium versus the temperature and flow velocity required in the FEM supported simulation of thixo-forming, were determined by evaluating isothermal compressive tests' results at various temperatures by a developed analytical method. Moreover, based on these data, thixo-forming process parameters were optimized among oth...

A method for investigating the forming technique of ancient ceramic vessels is presented. The recording, analysis, and comparison of the vessels' metrical properties by means of computer tomography, three-dimensional laser scanning, and solid-modeling software enables the identification of the applied manufacturing methods. A finite elements method...

Micro-blasting on PVD coated tools is an effective technology for improving their cutting performance. Through micro-blasting, compressive stresses are induced into the film, thus increasing the coating hardness, but its brittleness too. Simultaneously, abrasion phenomena are activated, which may lead to roughness augmentation, film thickness decre...

The lumbar spine is origin of the most frequent complains among all human body parts, since almost 80% of the population will at some point in life exhibit back related pathologies which in their majority will not require invasive surgery. Regardless the cause or the development of the problem, the in-depth investigation of its cause is of the upmo...

In the present paper an optimization algorithm to find out the geometric design parameters of an open loop spatial robot with three revolute joints is described. The design variables include the base position, the geometry of the links and the joint angles of the robot and are calculated so that the manipulator will be able to place its end-effecto...

The paper presents a method for the forward displacement analysis of 3-RRP and 3-PRP planar parallel manipulators including the RP-RP-RP third-class Assur group. The aim of this analysis is to find all possible configurations of the parallel planar mechanism for one given set of input joints values. The proposed method leads to a non-linear system...

The optimization of already known mechanical constructions and devices has always been a challenge for the engineers. Due to the fracture toughness and strict tolerance specification during the assembly process of constructions and systems, the utilization of the new adhesive in the mechanical devices is highly recommended. A very promising categor...

Ball bearings are perhaps the most widely used machine elements and a lot of important and expensive mechanic systems are based on them. Thus, it is necessary to establish a method to detect faults in order to keep the systems running properly. Fault identification of rolling element bearingsemploying condition monitoring techniques has been the su...

High Power Pulsed Magnetron Sputtering (HPPMS) techniques jointly with the deposition of a graded Cr/CrN-nanointerlayer on cutting inserts can increase the film adhesion and consequently the tool life. These improvements depend on the roughness of the employed cemented carbide substrates. The investigations described in the present paper intend to...

The performance of PVD films depends on the operational mechanical and thermal loads of coated tools or components. To withstand these loads, sufficient film strength properties, at ambient and elevated temperatures are required. The present paper deals with the mechanical properties and the impact resistance of a TiAlN coating at temperatures up t...

Based on analytical and experimental test methods, an evaluation of coated tools efficiency in milling Ti6Al4V with coated cemented carbide inserts is introduced. The stress-strain curves and the fatigue critical loads of the investigated coating were determined at various temperatures by nanoindentations and impact tests respectively, employing FE...