Pedro José Arrazola

• Senior Lecturer
• Machining Laboratory Head at Mondragon University

Broaching is a key manufacturing process that directly influences the surface integrity of critical components, impacting their functional performance in sectors such as aeronautics, automotive, and energy. Such components are subjected to severe conditions, including high thermomechanical loads, fatigue, and corrosion. For this reason, the develop...

Carbon fibre reinforced polymer/titanium stacks (CFRP/Ti6Al4V) are employed in aeronautics due to their excellent weight-to-strength ratio and corrosion properties. However, these same material properties present challenges for hole making which cannot be solved using conventional water-based metalworking fluids (MWFs), as they cause degradation of...

Additive Manufacturing (AM) is gaining importance as an alternative and complementary technology to conventional manufacturing processes. Among AM technologies, the Atomic Diffusion Additive Manufacturing (ADAM) technology is a novel extrusion-based process involving metallic filaments. In this work, the widely used 17-4 PH stainless steel filament...

Fatigue properties of parts are of particular concern for safety-critical structures. It is well-known that discontinuities in shape or non-uniformities in materials are frequently a potential nucleus of fatigue failure. This is especially crucial for the Ti6Al4V alloy, which presents high susceptibility to the notch effect. This study investigates...

Broaching is widely used for the manufacturing of complex geometries which requires high dimensional accuracy and surface finishing (e.g., fir tree, dovetail). A software development for force prediction in complex shape broaching is presented. The software automatically extracts the local uncut chip section along each tooth of the tool and based o...

Nowadays, numerical models are one of the most widely used techniques to predict material performance subjected to different manufacturing processes. However, to obtain accurate predictions, these models require reliable input data from thermomechanical tests. Nevertheless, during the test performance the material is self-heated due to a phenomenon...

Automotive transmission components are subjected to cyclic loads and, thus, must have a reliable fatigue performance. Since fatigue cracks nucleate at the surface, it is necessary to guarantee that its surface integrity accomplishes the required specifications. Typically, those components are finished by wet grinding after carburising heat treatmen...

Chatter is a harmful self-excited vibration that commonly occurs during milling processes. Data-driven chatter detection and prediction is critical to achieve high surface quality and process efficiency. Most existing chatter detection approaches are based on external sensors, such as accelerometers and microphones, which require installation of ex...

In the quest for decreasing fuel consumption and resulting gas emissions in the aeronautic sector, lightweight materials such as Carbon Fiber Reinforced Polymers (CFRPs) and Ti-6Al-4V alloys are being used. These materials, with excellent weight-to-strength ratios, are widely used for structural applications in aircraft manufacturing. To date, seve...

A known problem of additive manufactured parts is their poor surface quality, which influences product performance. There are different surface treatments to improve surface quality: blasting is commonly employed to improve mechanical properties and reduce surface roughness, and electropolishing to clean shot peened surfaces and improve the surface...

Nanocrystalline structured variants of commercially available alloys have shown potential for boosting the mechanical properties of these materials, leading to a reduction in waste and thereby retaining feasible supply chains. One approach towards achieving these nanostructures resides in frictional treatments on manufactured parts, leading to diff...

The reliability of the pertinent parameters set of Johnson-Cook constitutive model is highly linked with the friction condition at the tool-chip-workpiece interface. In the present work, a study on the influence of Coulomb’s friction coefficient on the observables such as forces, chip thickness and chip curvature by FE simulation of orthogonal cutt...

The application of artificial intelligence and increasing high-speed computational performance is still not fully explored in the field of numerical modeling and simulation of machining processes. The efficiency of the numerical model to predict the observables depends on various inputs. The most important and challenging inputs are the material be...

Drag finishing is one of the mass finishing processes that enhances surface roughness on complex and rough parts produced by additive manufacturing. This paper proposes a model to simulate abrasive media flowing around the part at a macroscopic scale based on an original rheological model inspired by civil engineering techniques. The correlation be...

Although drilling of FRP - metal stacks is the most widely used machining operation for these materials, it remains challenging in many aspects (tool wear, vibrations, delamination, poor surface finish, etc). In this context, this paper presents an analysis of drilled AISI 304-GFRP stacks using a 6 axis Stäubli TX200 robot, which is a technology in...

Transmission shafts used in the automotive sector must have a good tribological performance, and therefore an enhanced surface integrity. This paper aims to study the effect of eco-friendly innovative finishing operations (belt finishing, cryogenic grinding and dry grinding) on the surface integrity and tribological performance of steel grade 27MnC...

This paper reports on the state of the art in the experimental and numerical investigations of cutting and machining processes. The contributions on the above-mentioned processes and published on the Proceedings of the European Scientific Association for material FORMing (ESAFORM) Conferences are highlighted. In particular, this literature review i...

Critical aero-engine components such as turbine discs must withstand severe cyclic stresses, which can eventually lead to low cycle fatigue (LCF) failures. These components are made of difficult-to-cut alloys and machining conditions that are employed in the last stage of the manufacturing chain must be correctly defined to avoid the generation of...

Surface topography irregularities generated by broaching are analysed. Experimental tests were carried out on three workpiece materials: AISI 1045, Ti-6Al-4V, and Inconel 718, varying the cutting speed, rise per tooth, and rake angle. The experimental results combined with numerical simulation demonstrate that surface topography irregularities resu...

Although much research has been carried out in the field of the milling of GFRP (Glass Fibre Reinforced Polymer) composites, the complexity of the process is such that it is still not mastered in many industrial cases. The current work is aimed at studying the influence of three different geometries of PCD (PolyCrystalline Diamond) and cemented tun...

Some industrial applications require structured surfaces with high roughness values to ensure their functionality (Ra > 1 µm, Rmax < 30 µm). In order to obtain these structured surfaces with high roughness values, face milling operation is commonly used in aluminium components employed in the automotive and aeronautical sectors. Polycrystalline dia...

Nanocrystalline variants of commercially available alloys have shown the potential of boosting the mechanical properties retaining a feasible supply chain. One approach to achieve these nanostructures reside in frictional treatments on parts, leading to differential refinement in surface and bulk. In this work the machining method is considered as...

In the last few years, the industry requires to know in real-time the condition of their assets. Acoustic Emission (AE) technique has been widely used to understand the real-time condition of manufacturing processes such as the degree of tool wear or tool breakage. Traditionally, to fulfil that goal, the information extracted from the signal sensor...

Aerostructures withstand cyclic mechanical loads and therefore, their design must fulfil surface integrity and fatigue strength requirements. This paper studies the effect of pneumatic machine hammer peening on surface integrity of 7050-T7451 aluminium alloy. Specimens were hammer peened using two different stepover distances (0.07 and 0.35 mm) and...

Lightweight materials like Carbon Fiber Reinforced Polymers (CFRPs) present certain challenges, mainly regarding the resultant surface integrity of the holes. Different techniques such as optimized tool geometries, machining techniques and cooling/lubricating techniques have been tested for improving surface integrity on CFRPs. Unfortunately using...

Drilling is a continuous cutting process where two or more cutting edges remove the material, to obtain the desired feature. During the chip evacuation, it generally rubs against the generated surface. Thus, the roughness obtained differs from other machining processes such as turning or milling. Therefore, surface roughness can be different from t...

This paper addresses problems of predicting chip formation in high strain machining conditions. A complete physical model of chip formation requires both plasticity and chip/tool friction models. Friction models are commonly partly phenomenological, with friction coefficients measured from the conditions in which the models are applied. This paper'...

Tool condition monitoring have an important role in machining processes to reduce defective component and ensure quality requirements. Stopping the process before the tool breaks or an excessive tool wear is reached can avoid costs resulting from that undesirable situation. This research work presents the results obtained in drilling process monito...

Inconel 718 is a widely used alloy in the aeronautic sector due to its excellent mechanical and corrosion wear resistance under high temperature conditions. However, its good mechanical properties can be a double edge sword in terms of manufacturing, especially in those processes based in mechanical principles, such as machining or forming. Conside...

The new architecture of high velocity aircraft engines includes labyrinth-honeycomb interstate seals to improve the engine's stability. To increase these engines capacity a commonly used strategy is to reduce the clearance between the blades and the sealing system. However, this reduction causes non-desired contacts (rubbing) between the rotating a...

Additive Manufacturing (AM) has become the new paradigm of design and production strategies. While structural and functional materials are the most implemented ones, it is also possible to manufacture parts using precious metals, being copper one of the most interesting. Among AM technologies, the novel Atomic Diffusion Additive Manufacturing (ADAM...

Replacement of pollutant fluids with eco-friendly strategies in machining operations significantly contributes to protecting the environment, diminishing global warming, and ensuring a healthier workplace for employees. This study compares cryogenic coolants with conventional coolants in cylindrical plunge grinding using a Cubic Boron Nitride (CBN)...

To improve surface roughness of components without altering geometrical dimensions, polishing operations are commonly used. These operations may be time-consuming and expensive. Thus, the prediction of polished surface quality is a key issue to reduce the cost of these operations. Resulting surface quality of polishing operations is the outcome of...

Despite the prevalence of machining, tools and cutting conditions are often chosen based on empirical databases, which are hard to be made, and they are only valid in the range of conditions tested to develop it. Predictive numerical models have thus emerged as a promising approach. To function correctly, they require accurate data related to appro...

Drag finishing is one of the mass finishing processes that enhances surface roughness on complex parts due to the mechanical action of abrasive media. Due to the complexity of the process, industrial practice is based on experience. This paper proposes a model simulating abrasive media flowing around a part during a drag finishing operation at a ma...

Prediction of cutting forces in finishing conditions is becoming essential for the automotive industry, in order to achieve the desired surface integrity and keep controlled phenomena as chatter, especially in workpieces with small thickness walls manufactured by die casting. For predictions, orthogonal to oblique models are widely used, which requ...

Prediction of cutting forces in finishing conditions is becoming essential for the automotive industry, in order to achieve the desired surface integrity and keep controlled phenomena as chatter, especially in workpieces with small thickness walls manufactured by die casting. For predictions, orthogonal to oblique models are widely used, which requ...

One of the biggest issues of the mechanical cylindrical joints is related to premature wear appearing. Application of bioinspiration principles in an engineering context taking advantage of smart solutions offered by nature in terms of kinematic joints could be a way of solving those problems. This work is focussed on joints of one degrees of freed...

The constitutive model and its pertinent set of parameters are important input data in finite element modeling to define the behavior of Ti6Al4V during machining process. The present work focusses on comparing different constitutive models and the parameters sets available in literatures and investigating the quality of the predictions when varying...

Industrial transformation is taking advantage of the benefits of Information and Communication Technologies (ICT) to evolve into a more decision-making environment in manufacturing. Efficiency, agility, innovation, quality and costs savings are the goals of this transformation in one of the most employed manufacturing processes as is the case of ma...

Finite element modeling of machining aims for guidance in the choice of the cutting parameters and for the comprehension of the involved phenomena. The modeling of the behavior of the machined material is a key parameter to develop a realistic model. It is nowadays still extremely difficult to acquire experimental data on the material flow stress d...

Drag finishing is a widely used superfinishing technique in the industry to polish parts under the action of abrasive media combined with an active surrounding liquid. However, the understanding of this process is not complete. It is known that pyramidal abrasive media are more prone to rapidly improving the surface roughness compared to spherical...

Increased stability in machining processes is highly desired by all machining industries when vibrations and specially chatter occur. This phenomenon is defined as a self-excited vibration that occurs due to the regeneration of waviness of the workpiece surface. In machining industry, the trend is to rely on the trial and error method or mere exper...

The highly used Ti6Al4V alloy is a well know hard-to-machine material. The modelling of orthogonal cutting process of Ti6Al4V attract the interest of many researchers as it often generates serrated chips. The purpose of this paper is to show the significant influence of cutting speed on chip formation during orthogonal cutting of Ti6Al4V along with...

Composites materials and especially FRP are increasingly employed in many fields of applications (transport, aerospace, …) due to the current trend of improving global energy performances of new designs notably by mass saving. However the use of metallic materials such as aluminum and titanium alloys is still necessary in many cases and a lot of st...

A novel methodology to map the friction and normal stress distribution on the rake face using Partially Restricted Contact Length Tools in orthogonal cutting tests is proposed. The influence of cutting speed, feed and coatings on tool-chip friction when machining AISI 1045 is analysed. The results demonstrate that the new methodology can replace th...

Finite Element Modelling used to predict machining outcomes needs to be supplied with the appropriate material thermomechanical properties which are obtained by specific testing devices and methodologies. However, these tests are usually not representative of the extreme conditions achieved in machining processes and the obtained material law may n...

The cutting forces generated in machining are responsible for the tool deflection, part distortion, and features as chatter; therefore, their accurate estimation is fundamental to defining stable and safe working conditions to increase workpiece accuracy and productivity. Turn-milling is a conventional milling operation while the workpiece is simul...

High-precision metal cutting is increasingly relevant in advanced applications. Such precision normally requires a cutting feed in the micron or even sub-micron dimension scale, which raises questions about applicability of concepts developed in industrial scale machining. To address this challenge, we have developed a device to perform linear cutt...

Employing cutting fluids in machining processes, especially for difficult-to-cut materials, improves machinability through prolonged tool life, improves surface integrity and chip evacuation. However, like oil and water-based cutting fluids are hazardous to the environment and workers' health, alternative solutions are required. Liquid Nitrogen (LN...

A pertinent set of parameters is equally important as a constitutive model that describes the material behavior in modeling and finite element simulation of the machining process. The purpose of this study is to show the influence of the parameters on constitutive models by comparing and investigating three constitutive laws. The first is the origi...

Tribofinishing is one of the most popular polishing process in industry. The action of small abrasive media around parts enables to reduce significantly surface roughness and at the same time, to induce compressive residual stresses in the external surface layer. However, few scientific investigations have been made about this process. Whereas most...

This paper presents a novel indirect cryogenic cooling system, employing liquid nitrogen (LN2) as a coolant for machining the difficult-to-cut ASTM F-1537 cobalt-chromium (CoCr) alloy. The prototype differs from the already existing indirect cooling systems by using a modified cutting insert that allows a larger volume of cryogenic fluid to flow un...

Within the framework of industry 4.0, the aim is to develop collaborative human-machine environments in order to achieve greater adaptability to the variability of cutting processes by making efficient use of available resources. For this, the use of the existing information in the data obtained from the cutting processes is fundamental. The contro...

This study generated novel behavioural data for three engineering steels undergoing a turning process. The materials were hardened 410, PH13-8Mo and 300 M, two stainless steels and one high strength steel respectively. A primary aim was obtaining low machined surface roughness. A surface finish investigation compared tool geometries and tool materi...

Machining operations affect the properties of the final surface layer, and these can impact on its functional performance, particularly on fatigue behaviour. Among the properties of the machined surface, surface topography is one major parameter affecting fatigue behaviour. The literature review has demonstrated that stress concentration factors Kt...

Tribofinishing techniques are superfinishing processes that enable surface roughness improvement due to the mechanical action of abrasive media. A wide variety of kinematics can be employed and these abrasive media can have various trajectories and speeds when impacting the treated surface (normal, oblique, tangential, etc.). This work focuses on t...

Accurate and fast prediction of cutting forces is important in high-performance cutting in the aerospace industry. Gamma titanium aluminide (γ-TiAl) is a material of choice for aerospace and automotive applications due to its superior thermo-mechanical properties. Nevertheless, it is a difficult to machine material. This article presents the predic...

Broaching is a unique machining process with high accuracy and surface quality, which is employed in mass and batch production for the manufacture of components with highly complex geometries. It involves the use of multiple-edged complex tools in which the cutting edges are arranged with an offset also known as “rise per tooth” that determines the...

In machining of Ti-6Al-4V, it is commonly reported the appearance of segmented chip produced by adiabatic shearing (at high cutting speeds) and lack of ductility (at low cutting speeds). Moreover, machining is a manufacturing process that is based on applying external energy to the workpiece to produce a separation of a material layer. Thus, to ana...

Ferrite–Pearlite (FP) steels are used in many automotive components. However, their machinability in low cutting speed processes appears to be highly dependent on their metallurgical state. An experimental approach combining broaching and tribological tests under machining-like conditions was developed to determine the key FP features driving machi...

The most important challenges when machining difficult-to-cut alloys used in critical applications consist mainly in increasing tool life as well as improving the component surface integrity. In particular, the nickel based alloys exhibit very low thermal conductivity inducing higher cutting temperature and thereby rapid tool wear. In this context,...

Surface integrity induced by machining process affects strongly the performance of functional products, for instance, the fatigue life as well as the resistance to stress corrosion cracking. Consequently, it is relevant to evaluate the induced properties on and beneath the machined surface to ensure the good performance of the mechanical components...

Machining processes are subjected to machining vibrations and specially to chatter. This self-excited vibration determines the productivity of the processes. Over the years, many studies have been developed analysing the influence of the tool and machine structure on chatter. However, not many studies have been carried out on the workpiece material...

In machining of Ti-6Al-4V, it is commonly reported the appearance of segmented chip produced by adiabatic shearing (at high cutting speeds) and lack of ductility (at low cutting speeds). Moreover, machining is a manufacturing process that is based on applying external energy to the workpiece to produce a separation of a material layer. Thus, to ana...

Surface integrity directly affects the mechanical behavior of the workpiece, which is especially relevant on fatigue behavior. To characterize the quality of the machined surface, aspects such as material damage, roughness or residual stress are considered. Measurement of the material damage of the surface is characterized in some cases as surface...

This directory (http://hdl.handle.net/20.500.11984/1477) contains the raw data acquired by Mondragon Unibertsitatea during the execution of drilling tests. These data were used to obtain the results presented in the article "The capacity of statistical features extracted from multiple signals to predict tool wear in the drilling process" published...

Chatter vibrations produced during turning of slender parts cause poor workpiece surface finishing and premature tool wear. In this paper, mode coupling in flexible workpiece metal cutting without tailstock is analysed in the state-space domain. The proposed mode coupling model considers mode rotation with the workpiece. Closed form equations are o...

During the machining of Ti-6Al-4V the changing deformation mechanisms produce a complex microstructure of segmented chips, which directly influenced tool-wear and process stability. Numerical simulation could give an insight into the physical phenomena involved in chip segmentation, but its accuracy is directly related to the reliability of the inp...

Before machining - one of its final production step - workpiece have embedded residual stresses due to the manufacturing processes. On large and complex aluminium aeronautical parts, up to 90% of the raw material volume is removed by machining. During this operation, the mechanical equilibrium of the part is in constant evolution due to the redistr...

Machining is a quite relevant process on industry. However, despite its industrial importance, many parameters of the process are still chosen through empirical testing which is traduced in high time-consuming and costs. Based on that, an alternative approach to empirical methods is needed. Any other approach (numerical, analytical) needs a previou...

Titanium alloys such as Ti6Al4V are widely used and are well known as hard-to-machine material. The material behavior that is described by the constitutive equation plays a pivotal role in modeling and simulation of machining process. The Johnson–Cook material model is widely used for analysis of material flow stress, especially for those materials...

Nickel-based superalloys are widely exploited in turbojets components which are subjected to intense thermal and mechanical loadings during their operation. In fact, they exhibit excellent mechanical properties over a wide range of temperature and high corrosion and creep resistance. However, these materials induce several problems related to the s...

Chip segmentation is a common phenomenon that occurs during the high and low speed machining of Ti64. At low cutting speed the lack of ductility is the responsible for the segmentation of the chip, while for high cutting speeds the adiabatic shearing is the predominant phenomenon. However, that segmentation is commonly only linked to worsening of t...

Robotic machining is starting to feature in the industry thanks to its high flexibility, adaptability, large workspace and low cost. In fact, many studies have already confirmed that robotic machining can be a real cost saving and flexible alternative to large scale conventional CNC machines, due to the aforesaid advantages. However, robotic machin...