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Metal cutting processes contribute significant share of the added value of industrial products. The need for machining has grown exponentially with increasing demands for quality and accuracy, and despite of more than a century of research in the field, there are no reliable and accurate models that describe all the physical phenomena needed to optimize the machining processes. The scientific community has begun to explore hybrid methods instead of expanding the capabilities of individual modelling schemes, which has been more efficient than efficacious direction. Following this trend, we propose a hybrid finite element — machine learning method (FEML) for modelling metal cutting. The advantages of the FEML method are reduced need for experimental data, reduced computational time and improved prediction accuracy. This paper describes the FEML model, which uses a Coupled Eulerian Lagrangian (CEL) formulation and deep neural networks (DNN) from the TensorFlow Python library. The machining experiments include forces, chip morphology and surface roughness. The experimental data was divided into training dataset and validation dataset to confirm the model predictions outside the experimental data range. The hybrid FEML model outperformed the DNN and FEM models independently, by reducing the computational time, improving the average prediction error from 23% to 13% and reduced the need for experimental data by half. [Display omitted] • A Novel Hybrid FEML model based on Deep Neural Networks (DDN) and Finite Element Method (FEM) is proposed for predicting metal cutting process outcomes. • Hybrid FEML model outperforms DNN and FEM models independently regarding prediction accuracy, computational time and need for experimental data. • FEM model with CEL formulation has advantages in 3D machining simulations over ALE methods because CEL does not require remeshing. [ABSTRACT FROM AUTHOR]

Most metal turning processes utilize cutting fluids. Despite extensive experimental and analytical studies, the mechanisms of chip formation under consideration of a cutting fluid are still not entirely understood. Due to fluid-structure interaction, simulating wet cutting processes for an extended duration has not been feasible. The primary objective of this study is to utilize a simulation approach to provide additional information about the wet chip formation process in contrast to measurement methods, with a view to drawing conclusions. As methodology the Finite-Pointset-Method (FPM) is employed to simulate the chip formation process for dry, flood and specifically high-pressure cooling conditions during machining of carbon steel C45 as well as nickel-based alloy Inconel 718. Due to the increased relative velocity between workpiece and cutting fluid with the use of high-pressure cooling compared to flood cooling, numerical stability issues are present. Initially, the modeling approach to handle high-pressure cooling conditions is described and validated by an impact test. Subsequently the cutting simulation model is presented in detail and verified by measurements. The simulation results of stress, temperature and plastic strain rate fields are used to elucidate the observed discrepancies between various cutting fluid strategies in detail. These findings suggest explanations for the high efficiency of high-pressure cooling such as a decline of hydrostatic stresses or activation of ductile damaging. [ABSTRACT FROM AUTHOR]

Turning difficulties have been reported in stroke persons, but studies have indicated that fall history might not significantly affect turning performance. Fear of falling (FOF) is common after a fall, although it can occur in individuals without a fall history. Could FOF have an impact on turning performance among chronic stroke patients? This cross-sectional study recruited 97 stroke persons. They were instructed to perform 180° and 360° turns, and their performance was represented by angular velocity. FOF was evaluated using the Falls Efficacy Scale-International (FES-I). Falls that occurred 12 months prior to the study assessment were recorded. A higher FES-I score was significantly correlated with a decline in angular velocity in all turning tasks after adjustment for demographic data. The correlation remained significant after controlling for falls history. Participants with a high level of FOF exhibited significantly slower angular velocities during all turning tasks compared with those with a low level of FOF. Participants with a moderate level of FOF had a significantly slower angular velocity than did those with a low level of FOF during the 360° turn to the paretic side only. A higher level of FOF, regardless of fall history, was significantly associated with a reduced angular velocity during turning. A high level of FOF affected turning performance in all tasks. Turning performance may not be affected by fall experience. Anxiety about falling may have a greater effect on turning performance than does fall history. • Fear of falling may have a greater effect than does fall history on turning. • Turning performance may not be affected by fall history. • Assessing fear of falling might be helpful for understanding the motor control during turning. [ABSTRACT FROM AUTHOR]

Carbon fibre-reinforced polymer (CFRP) is being widely used due to its low specific weight and outstanding mechanical properties. However, using identical machining parameters on unidirectional CFRP can lead to different results depending on the fibre orientation. Recently, a process-independent model describing the engagement conditions in oblique cutting of unidirectional CFRP has been developed, introducing the spatial angles θ 0 and φ 0. Since the engagement conditions of milling and drilling are complex, analogy experiments are conducted in turning with variation of the setting κ r and inclination angles λ s. In this study, process forces and surface roughness were measured as a function of the complete range of fibre cutting angle θ. [ABSTRACT FROM AUTHOR]

Finish turning is one of the key operations governing the residual stress of functional surfaces. The residual stress state is determined by the cutting conditions and the selected cutting tool system (macro geometry, cutting edge preparation, tool substrate, multi-layer coating...). However, this initial configuration evolves over time due to tool wear. Therefore, it seems fundamental to reproduce the wear process of the tool in order to understand the evolution of thermo-mechanical loadings applied to the machined surface. This work presents a numerical methodology for predicting the wear-induced residual stress drift in longitudinal turning. The complete 3D cutting tool is discretized into elementary 2D sections. A finite element based procedure is developed to calculate, considering each local tool geometry, the local loads withstood by the machined material. The latter are merged to generate equivalent 3D thermomechanical loadings implemented in a second macroscopic model able to calculate the residual stress state under different wear levels. Experimental cutting tests with artificially worn tools have confirmed that good agreement can be achieved. [ABSTRACT FROM AUTHOR]

High performance powder-based Ni-based superalloys exhibit exceptional in-service properties at elevated temperature, however this leads to reduced machinability and the potential for significant machining induced damage. Field assisted sintering technology (FAST) is capable of consolidating powder rapidly and efficiently, allowing for precise control of the microstructure via the dissolution of strengthening phases. In this study, subsolvus and supersolvus dwell temperatures were utilised to produce fine and coarse grain forms of an advanced Ni-based disk alloy. Surface integrity and machining forces were then evaluated after single point turning for a range of surface speeds. Higher cutting forces and lower depths of subsurface damage were generated when machining the fine grain (subsolvus) material when compared to the coarser grained (supersolvus) material. For both material conditions tested, higher surface speeds led to a reduced depth of subsurface deformation due to increased local temperatures, promoting workpiece softening. In addition, at higher cutting speeds the deformation of near surface γ' precipitates were observed to be greater. These results demonstrate that the FAST process can be utilised to control microstructure, and as a result, tailor the machinability of Ni-based superalloy material. [ABSTRACT FROM AUTHOR]

Carbon fibre-reinforced polymer (CFRP) is favored for its high strength to weight ratio, outstanding direction dependent mechanical properties and the high potential for load adapted design. However, machining unidirectional CFRP is challenging due to its anisotropic behavior, resulting in variable surface quality under identical machining parameters with different fibre orientations. Recently, a universal, process-independent model describing the engagement conditions in oblique cutting of unidirectional CFRPs has been developed, introducing the spatial fibre cutting angle θ 0 and the spatial engagement angle ϕ 0. Milling and drilling are mostly used for machining CFRP. Since the engagement conditions are rather complex, first analogy experiments are conducted in turning with variation of the setting and inclination angles. In this study, continuous surface profiles were recorded as a function of the spatial fibre cutting angle. Phenomenological and continuous wavelet analyses can be used to describe the surface profiles as a function of the spatial engagement conditions and to accurately predict them and the surface roughness using an inverse wavelet transformation. Experimental investigations with a side milling process of CFRP validate the prediction approach and show a good agreement between the experimental and predicted surface profiles. [ABSTRACT FROM AUTHOR]

Over the last years two factors have deeply affected research in Manufacturing: the growing interest around Additive Manufacturing (AM) processes and the need to reduce the anthropogenic environmental impact. As result, a large papers concerning the environmental impact performance of AM compared to conventional processes have been published. Specifically, very complex models accounting for the impact of each life cycle stage of AMed components have been released. Results revealed that AM, at present, guarantees energy savings only within some domains, and the potential saving depends on several factors: product complexity, eco-properties of the material, energy intensity of the material deposition, light-weighting enabled by AM approaches and extent of the use phase. Above all, the result of the comparative analysis depends both on the considered factors and on the selected system boundaries. The already proposed models are very complex and many inventory data are needed, this could make them unapplicable at industrial level. In the presented paper, simplified models are proposed and the performances of these are quantified with varying the analyzed scenario (considered factors and selected system boundary). Results revealed that, for given scenarios, simplified models characterized by low computational effort, can provide reliable results. Guidelines for the implementation of different models with varying the system boundary are provided for the cumulative energy comparison of Electron Beam Melting and conventional turning for the production of titanium alloys components. [ABSTRACT FROM AUTHOR]

Quantifying inter-limb differences in kinematics and kinetics during change of direction is proposed as a means of monitoring rehabilitation following anterior cruciate ligament reconstruction (ACLR). Velocity and centre of mass (CoM) deflection angle are fundamental task descriptors that influence kinematics and kinetics during change of direction. Inter-limb differences in approach velocity and CoM deflection angle have been identified following ACLR and may contribute to the presence of inter-limb differences in kinematics and kinetics during change of direction. The aim of this study was to quantify the proportion of variance in kinematic and kinetic inter-limb differences attributable to inter-limb differences in approach velocity and centre of mass deflection angle during a change of direction task. A cohort of 192 patients (male, 23.8 ± 3.6 years, 6.3 ± 0.4 months post primary ACLR) completed a pre-planned 90° change of direction task on both their operated and non-operated limb. Inter-limb differences in approach velocity and CoM deflection angle were calculated alongside lower-extremity kinematic and kinetic variables. The relationship between inter-limb differences in task-level variables and inter-limb differences in kinematic and kinetic variables was examined using linear regression models. Kinematic and kinetic inter-limb differences were adjusted for inter-limb differences in approach velocity and CoM deflection angle. Adjusted and unadjusted inter-limb differences were submitted to one sample t-tests. Inter-limb differences in approach velocity and centre of mass deflection angle explained 3 – 60% of the variance in kinematic and kinetic inter-limb differences. Statistical inferences remained consistent between adjusted and unadjusted conditions with the exception of hip flexion angle. Inter-limb differences in task-level features explain a large proportion of the variance in inter-limb differences in several kinematic and kinetic variables. Accounting for this variation reduced the magnitude of kinematic and kinetic inter-limb differences comparable to those previously observed in normative cohorts. • ACLR patients alter CoD technique via changes to velocity and angle. • Asymmetries contribute to inter-limb differences in biomechanical variables. • Task level asymmetries important to consider following ACLR. [ABSTRACT FROM AUTHOR]

Diamond turning of microstructured surfaces based on slow slide servo or fast tool servo technologies suffers from either low machining efficiency or low surface accuracy, due to the highly mixed low-frequency and high-frequency tool trajectory. This work proposes a new parallel tool servo (PTS) turning technology, in which the original tool path is filtered according to an optimal cut-off frequency and then decomposed into independent trajectories separately for a slow slide and a fast stage in parallel. This approach is experimentally validated and compared with existing single-mode servo technologies, with significantly enhanced cutting performance, thus offering a novel perspective for ultra-precision machining. [ABSTRACT FROM AUTHOR]

In turning thin-walled parts, machining errors and deviations from the aspired workpiece shape occur due to influences of the workpiece clamping and elastic deformations of the workpiece caused by clamping forces. This paper introduces a newly designed sensor integrated chuck jaw for turning applications, which allows for an on-line monitoring of the actual clamping forces and an in-process prediction of shape deviations of the machined parts. The design and characteristics of the sensory jaw are described and its monitoring capability is validated in turning experiments. Correlations of sensor data with workpiece shape deviations and models for error prediction are analyzed. [ABSTRACT FROM AUTHOR]

Evaluating surface frequency components in the fabrication process is critical for controlling the machined surface quality. The presence of anisotropic ripples on diamond-turned surfaces makes this challenging. A multiscale frequency evaluation method, referred to as Surface Intrinsic Mode Decomposition (SIMD), is proposed for evaluating on-machine surface measurement (OMSM) data. It decomposes continuous surface probing profiles, incorporating both temporal and spatial frequency information. In comparison to the conventional power spectral density (PSD) analysis method, the approach enriches frequency details over a wider range, which contributes to a more comprehensive understanding of surface quality and helps to identify mid-spatial frequency (MSF) errors. [ABSTRACT FROM AUTHOR]

Individuals with peripheral vestibulopathy are known to have difficulty with volitional head turns. This leads to differences in head and body turning kinematics, compared to those without vestibular dysfunction. Multiple sclerosis (MS), a neuro-inflammatory disease affecting the central nervous system, can cause vestibular dysfunction (dizziness, unsteadiness, gaze instability). However, head and trunk turning kinematics in people with MS (PwMS) have not been assessed. Will PwMS, demonstrate head and body kinematics alterations similar to individuals with a peripheral dysfunction compared to vestibular healthy individuals? Eleven individuals with a recent vestibular schwannoma resection (VSR), fourteen PwMS, and 10 healthy control (HC) participants were fitted with head and trunk worn inertial measurement units (IMUs) and performed walking and turning tasks. Head and trunk peak turning speed and amplitude were extracted. Regression models controlling for gait speed were fit per outcome with post hoc corrections applied to significant models. Yaw plane head turn speed and amplitude were significantly less in the VSR group compared to HC. Pitch plane head turn amplitude was significantly smaller in PwMS compared to HC (p = 0.04), however pitch plane speed did not differ between the groups. There was no difference between PwMS and the VSR group in yaw or pitch plane speed and amplitude. Both PwMS and the VSR group turned significantly slower than HC during the 180d body turn as measured at the head and trunk (head speed model p = 0.009 and <0.001; trunk speed model p < 0.001 for both groups) however the MS and VSR groups did not differ from each other. Turning kinematics while walking in PwMS are altered compared to HC and are similar to individuals with unilateral vestibular hypofunction. Centrally mediated vestibular dysfunction in PwMS may alter movement kinematics and should be considered during examination and treatment. • People with MS have turning kinematics similar to people with vestibular loss (78). • Turning kinematics differ in people with multiple sclerosis compared to controls (81). • Centrally mediated vestibular dysfunction may alter movement kinematics (71). [ABSTRACT FROM AUTHOR]

A double inserts turning with two inserts mounted on a tool shank is proposed to control regenerative chatter vibration in turning of workpieces with low rigidity. In the presenting turning, the forward and the backward inserts are placed with a position offset in the feed direction; and those inserts are also clamped with a height offset each other in the cutter height direction. A part of the waved surface formed in the preceding cut by the forward insert is concurrently removed by the backward insert placed at a higher position than the rotation center of the workpiece. The regenerative effect, then, is controlled to suppress the chatter vibration by cutting the outer modulation with a time delay. This paper describes the principle of the double inserts turning for control of chatter vibration based on phase difference of the outer and the inner modulations. An analytical model, then, is presented to associate the regenerative effect with the offset parameters of the inserts. The cutting tests were conducted to verify the double inserts turning of a slender workpiece with the offset parameters of the inserts obtained by the analytical simulation. The chatter vibration is controlled effectively by adjusting the offset parameters of the inserts corresponding to the turning parameters. • A novel turning operation is proposed to control regenerative chatter vibration in double inserts cutting by two inserts. • Regenerative effect can be controlled by cutting a part of the outer modulation with phase difference by using two inserts. • An analytical model is presented to determine the offset parameters of the inserts for control of the chatter vibration. • The double inserts cutting may be simply applied to normal turning operations without any additional equipment. [ABSTRACT FROM AUTHOR]

Movement and locomotion are controlled by large neuronal circuits like the cortex-basal ganglia (BG)-thalamus loop. Besides the inhibitory thalamic output, the BG directly control movement via specialized connections with the brainstem. Whether other parallel loops with similar logic exist is presently unclear. Here, we demonstrate that the secondary motor and cingulate cortices (M2/Cg) target and strongly control the activity of glycine transporter 2-positive (GlyT2+) cells in the pontine reticular formation (PRF). In turn, PRF/GlyT2+ cells project to and powerfully inhibit the intralaminar/parafascicular nuclei of the thalamus (IL/Pf). M2/Cg cells co-innervate PRF/GlyT2+ cells and the IL/Pf. Thalamus-projecting PRF/GlyT2+ cells target ipsilateral subcortical regions distinct from BG targets. Activation of the thalamus-projecting PRF/GlyT2+ cells leads to contralateral turning. These results demonstrate that the PRF is part of a cortico-subcortical loop that regulates motor activity parallel to BG circuits. The cortico-PRF-thalamus loop can control turning synergistically with the BG loops via distinct descending pathways. [Display omitted] • Motor cortex targets thalamic-projecting PRF/GlyT2+ cells and control their activity • PRF/GlyT2+ cells inhibit the ipsilateral IL/Pf in the thalamus and also target the medulla • Activation of IL/Pf-projecting PRF/GlyT2+ cells induces contralateral turning • Ipsilateral PRF inhibition and contralateral excitation act synergistically on turning Bősz et al. reveal a cortico-brainstem-thalamic circuit that controls motor activity. Glycinergic PRF neurons (GlyT2+) receive motor cortical inputs, which also target the thalamus and the basal ganglia, forming a regulatory loop. In turn, GlyT2+ PRF neurons inhibit the ipsilateral thalamus and medulla and drive contralateral turning. [ABSTRACT FROM AUTHOR]

• A concept of the parallel multidirectional turning is proposed. • An analytical model for the parallel multidirectional turning is established. • Effects of process parameters on forces, temperature, power, and machining error are analyzed. Slender shafts have wide application on the aerospace, automotive and medical devices. However, they are prone to bending deformation during cutting process due to their low rigidity, resulting in poor machining accuracy and efficiency. A parallel multidirectional cutting (PMC) method is proposed using two tools to simultaneously cut the workpiece in forward or reverse directions contributing to overcome the problem of large deflections of these shafts. The main concept and PMC shared and unshared cutting modes are elucidated. An analytical model for PMC is established including chip geometry model, cutting force model and workpiece deflection feedback model. Given tool geometry, feed and depth of cut, chip load is accurately calculated using cutting edge discretization. The Johnson-Cook constitutive model is used to determine shear stress and shear force on the primary shear plane, and therefore the three-dimensional cutting force is obtained. The force condition of the workpiece is analysed under two clamping methods and the deformation of the workpiece is calculated and feed back into the model. On this basis, the influencing mechanism of cutting force, cutting power, cutting temperature and machining error of PMC is explored under different cutting modes, machined shaft geometry, tool parameters and cutting parameters. The smaller-the-better characteristic of Taguchi's method and signal-to-noise ratio are used to analyse the effect of cutting parameters on the PMC performance. Furthermore, an experimental validation is conducted to verify the cutting power, temperature, and diameter errors obtained by the proposed model, and the result shows a strong correlation with simulation predictions. The proposed method significantly improves machining precision and efficiency, with promising applications in high-precision manufacturing industries such as aerospace and medical device production. [Display omitted] [ABSTRACT FROM AUTHOR]

Turning movements are frequently encountered during daily life and require more frontal and transverse hip mobility than straight walking. Thus, analysis of turning might be an insightful addition in the evaluation of conservative treatment approaches for hip osteoarthritis patients. The study objective was to quantify the effects of mild-to-moderate symptomatic hip osteoarthritis on lower-body turning biomechanics and evaluate the effects of hip bracing in this cohort. Biomechanical analysis of 90° step and spin turns in 21 persons with hip osteoarthritis and 21 healthy controls (case-control-study) and intervention study on the effects of hip bracing in hip osteoarthritis participants. Hip and knee kinematics and dynamics were compared using independent sample t -tests or one-way repeated measure ANOVAs. Persons with hip osteoarthritis have reduced peak hip extension and sagittal and transverse hip range of motion during turning. During the spin turn reduced hip adduction and frontal hip range of motion were found. Bracing increased the movement velocity at turn initiation and limited the transverse hip range of motion during both turns but increased knee peak adduction and internal rotation moments during spin turns. Persons with hip osteoarthritis present altered hip kinematics during 90° spin turns in all movement planes. Their inclusion during clinical movement analysis might facilitate the detection of mobility deficits at an early disease stage. Bracing led to higher movement velocity at turn initiation without increasing load at the hip joint and reduced transverse hip range of motion, avoiding the painful reaching of range of motion endpoints. • Mild-to-moderate hip osteoarthritis alters hip kinematics during 90° turns. • Hip dynamics during turning are not affected by mild-to-moderate hip osteoarthritis. • Hip bracing increases movement velocity and reduces transverse hip range of motion. • 90° turns are useful to assess frontal and transverse hip mobility. [ABSTRACT FROM AUTHOR]

This study aims to elucidate the biomechanical characteristics of turning in daily life by analyzing the three-step process of approach, turn, and departure phases. The research involved ten healthy young individuals performing straight walking and 90° turns, categorized into Side-Step (SS) and Cross-Step (CS) turns. Using a 17-camera motion capture system and force plates, the study measured joint angles, moments, and center of mass (COM) variations. The results indicated that turning involves rotational movements of the lower limbs across three phases, with distinct biomechanical roles for each step. From the perspective of COM control, instability increased at the departure foot in SS, while in CS, stability was maintained at both the approach and departure foot. This study emphasized the importance of rotational movements and rotational forces in the lower limb joints during turning. It also revealed that the center of mass is controlled across three steps. These findings highlight the need for a comprehensive analysis of turning and add a new perspective to gait analysis during turning. [ABSTRACT FROM AUTHOR]

Tool wear is one of the most challenging issues in manufacturing. In cutting processes, tool-life testing procedures are defined by ISO standards. These standards give the guidelines to perform tool-life testing in terms of workpiece material, tool geometry, tool material, cutting fluid, tool wear assessment, and tool-life evaluation. For determining the useful tool-life, the standards recommend running several tool-life tests at constant cutting speed till reaching a specified value of tool wear, as defined by the selected tool-life criterion. But, in industrial applications, the approach is different. The same tool is often used to make different geometrical features on the same component using different process parameters, depending on the desired geometry and surface quality. Therefore, it is possible to state that the tool accumulates wear over the working time under different cutting conditions. In other words, the tool is subjected to cumulative tool wear. This paper aims to deepen the knowledge about cumulative tool wear, which means the tool wear generated by a combination of different process parameters. An innovative experimental procedure is proposed to determine the useful tool-life when machining a part with the same tool at different process parameters. Cumulative tool flank wear tests were performed on AISI 1045 samples by changing the cutting speed, keeping the other cutting parameters constant. The experimental cumulative flank wear evolution was compared with the theoretical one. Four different machining cycles were tested to simulate different industrial cases. The comparison revealed a good agreement between the prediction and the experimental data. • Cumulative tool wear related to the change of cutting speed is investigated. • Tool wear tests were conducted by performing turning on AISI1045 bars. • A novel procedure to predict the cumulative tool wear is experimentally validated. [ABSTRACT FROM AUTHOR]

Turning gait is considered as a challenging motor task. However, only few existing studies reported turning biomechanics from the aspect of foot plantar pressure. This study aimed to investigate turning biomechanics by studying foot plantar pressure characteristics Twelve young male participants were involved in this experimental study. They were instructed to perform turning tasks with different turning angles (i.e., 30°, 60°, and 90°). Foot plantar pressure was quantified by the force time integral (FTI) underneath seven plantar sub-areas. Analysis was carried out for different turning strategies (spin turns versus step turns), separately. The results showed that for small-angle spin turns, plantar pressure patterns changed at the early stage of the approaching step, suggesting a preparatory action for the increased lower limb range of motion in the transverse plane during turning; for step turns, an imbalance weight bearing mechanism was adopted when making large-angle turns to compensate for the centripetal force during turning. The findings provide improved knowledge about turning biomechanics. They have practical implications for motion planning of lower-limb assistive devices for those with difficulties in turning. • Characteristics of foot plantar pressure (FPP) during turning were investigated. • FPP patterns changed early in the approaching step for small-angle spin turns. • An imbalance weight bearing mechanism was adopted in large-angle step turns. • The findings have practical implications for motion planning of assistive devices. [ABSTRACT FROM AUTHOR]

A new model of cutting force formation in turning is investigated. In this model, the cutting area is shaped as a result of displacements of the undeformed blade points projections at the cutting plane. Extreme kinematics cases of turning are compared. In a cylinder turning, the feed rate fluctuates perpendicular to the plane of rotation, and the cutting force excursion depends on the ratio of the rotation to vibration frequencies. Contrary to this, in a facing, the feed rate varies in the plane of rotation, and the cutting force is not modulated. The theoretical results accord well with experimental data. [ABSTRACT FROM AUTHOR]

In recent years, the rise in computation and modelling capabilities has enabled first chip formation simulations for wet cutting processes. Currently, chip formation simulations are limited to a small simulation domain around the cutting edge. Hence, vague assumptions of inflow boundary conditions of the cooling lubricant must be made. In this paper, a procedure is shown to determine the boundary conditions of the free fluid jet for different cooling lubricant strategies by combination of Particle Image Velocimetry (PIV) and meshfree fluid simulations. As a result, usual assumptions of cooling lubricant boundary conditions are evaluated and deviations are identified. [ABSTRACT FROM AUTHOR]

Machining processes of Ni-based alloys typically lead to very high wear rates and significant heat generation, even when small material removal rates are considered. Despite the increasing usage of PCBN tools in the machining of Ni-based superalloys, further research is required in order to better understand the associated benefits. In this work, the machinability of Inconel 718 in two different delivered strength conditions has been evaluated using PCBN tools through instrumented turning operations. Tool-life has been explored and linked to cutting force evolution. Numerical simulation of the turning operations has revealed important towards tool wear modelling. [ABSTRACT FROM AUTHOR]

The prediction of cutting forces is a major topic in predesigning turning operations. An efficient method to predict cutting forces are machining simulations taking mechanistic force models into account. However, their accuracy highly depends on the model parameters, whose calibration requires numerous time- and cost-consuming experiments. In order to calibrate model parameters with low experimental effort, this study presents a Bayesian Makrov Chain Monte Carlo (MCMC) method. Force model parameters are conditioned to only few measurements of turning experiments and lead to accurate results of machining simulations. Due to low experimental effort, this approach is of major interest for industrial applications. [ABSTRACT FROM AUTHOR]

The wear behaviour of cutting tools can be significantly improved by a load-optimized design of the cutting edge microgeometry. Thereby, the knowledge of local mechanical stresses is necessary. The experimental-based modelling of mechanical stresses in the continuous cut was already investigated in previous work. In this paper, this method is adapted to the interrupted cut by considering contact lengths, process forces and process temperatures during tool entry and exit. The identified mechanical stresses and temperatures are used for a tool material specific cutting edge microgeometry design. [ABSTRACT FROM AUTHOR]

The growing trend towards industry 4.0 requires in-process identification of the surface properties. The non-destructive highspeed-3MA-testing can be used to characterize surface layers of ferrous materials during turning processes. However, in-process measurements will result in higher workpiece temperatures and thus would interfere with the micromagnetic properties of the workpiece. In the presented study, workpiece surface temperatures will be experimentally determined when turning AISI 4140. Further on, workpieces will be heated up to the respective temperatures, which will then be measured with the 3MA-sensor as they rotate. The effect of temperature will be modelled and used for compensating the associated errors. [ABSTRACT FROM AUTHOR]

The objective of this paper is to model the residual stress generation mechanisms induced during the finish turning of a fillet radius on a 15-5PH steel shaft. The model, based on the 3D thermo-mechanical equivalent loading method, is used to predict the continuous variation of residual stresses resulting from the continuous variation of the machined sections in the fillet radius. Finally, experimental tests are carried out to compare the numerical results with the residual stress measurements made by X-ray diffraction in some positions. [ABSTRACT FROM AUTHOR]

Machining processes are characterized by thermal loads generated during the shearing and friction work of the cutting process. For the in-process temperature measurement by a tool-workpiece thermocouple a consideration of the change in temperature of the cold junction at the specimen rear side is vital for the accuracy of the measurement. Thus, a macroscale thermodynamic simulation model implemented in COMSOL Multiphysics is used to model the heat distribution within the specimen during turning of the aluminum alloy EN AW-2017. The thermal input conditions are derived from experimental tests. For the assumption of the relative measurement error the simulated cold junction temperature is compared to the in-process temperature measured by a tool-workpiece thermocouple. The model shows that the machining time is the most important factor for heating of the cold junction. On the one hand, for low cutting speeds the measurement error in relation to the measured temperature is significantly high which discloses the need for a temperature compensation in this parameter range. On the other hand, for high cutting speeds and thus short machining times, the cold junction is not subjected to a significant increase in temperature. Consequently, the model validates the applicability of the temperature measurement based on a tool-workpiece thermocouple for dry machining of aluminum alloys with high cutting speeds. [ABSTRACT FROM AUTHOR]

Many industrial machining operations are carried out under wet machining conditions. Modelling and simulating fluid-structure-interactions and conjugate heat transfer are still a challenge nowadays. In this paper, temperature dependent heat transfer coefficients (HTC) h(T) are experimentally estimated for wet machining-like conditions in a jet cooling experiment. The transient temperature is thereby used to solve an Inverse Heat Transfer Problem for HTC function estimation. Determined HTC are applied as input in related jet cooling simulation using the Finite-Pointset-Method (FPM) to validate the modeling approach. Additionally, wet cutting simulations numerically highlight the influence of determined HTC h(T) on turning. [ABSTRACT FROM AUTHOR]

A numerically developed residual stress distribution model during turning Ti6Al4V alloy with an Internally Cooled Tool (ICT) has been validated experimentally. The effect of inlet coolant pressure on cutting forces and temperature has been predicted. The predicted and measured values for forces and temperature lies in 10-20%. The residual stress at the surface and subsurface layer has been validated with XRD technique. It is found to be well suited in predicting the trend for residual stress of Ti6Al4V with ICT. Maximum residual stress in cutting direction is -308 MPa and -319 MPa for laminar and turbulent flow respectively. [ABSTRACT FROM AUTHOR]

In the general turning process, solutions for attaining the tool-workpiece relative position such as in-situ touch probes, external devices mounted with air/electric micrometers, and cameras are either indirect or cost/space-consuming. In this paper, a novel direct contact detection method based on the internal data of the machine tool servo and the self-identification strategy of the rotational center as an application of the detection method are proposed. The former method compares the internal data of the non-contact and contact motions, and then precisely identifies the contact position by processing it backwardly. The latter method makes multiple contacts on the pre-machined surface of the workpiece with a redundant-axis movement, and the rotational center identification is realized using the coordinates of contacts achieved by the former method. The effectiveness of the proposed methods is verified experimentally. • Proposal of a direct tool-workpiece contact detection method based on internal servo data of machine tools. • Spindle torque signal of noncontact motion is subtracted from that of contact motion, and then processed backwardly. • Proposed contact detection method shows good accuracy and repeatability, e.g.,repeatability of 1.18 μ m. • Proposal of a rotational center self-identification strategy using redundant-axis movement. • Rotational center is identified without additional equipment with good accuracy, e.g., diameter error of 11 μ m. [ABSTRACT FROM AUTHOR]

Cutting temperature is important in single point diamond turning. However, the challenge of measuring temperature in single point diamond turning is locating a sensor at the cutting edge during machining. This paper presents a tool system having a capability of measuring cutting temperature in diamond turning by the tool itself without any additional temperature sensors. A diamond tool was doped with boron via high temperature and high pressure treatment, by which the tool becomes a P-type semiconductor and thus have a thermal-sensitive characteristic for indicating the cutting temperature at the cutting edge zone during diamond turning processes. [ABSTRACT FROM AUTHOR]

Recently, the application of low frequency vibration has been attempted in the turning process. The tool is vibrated in the feed direction by numerical control to break up long continuous chips that adversely affect the surface quality and tool wear, etc., by generating a duration of cutting edge leaving workpiece. In order to achieve higher machining efficiency in vibration cutting, however, it is necessary to focus on chatter stability. When chattering occurs, a higher frequency chatter vibration is superimposed on the low-frequency tool vibration caused by the feed motion of the servo drive. However, the chatter amplitude decreases due to system damping, because the cutting force does not act in the air-cutting section of vibration cutting. In addition, tool displacement is regenerated not only before one spindle rotation, but also before two or more rotations in vibration cutting. Therefore, the application of low frequency vibration has an important influence on the chatter stability. The purpose of this study is to reveal the detailed effects of vibration conditions on the stability limit, and identify the vibration conditions that achieve high chatter stability. We consider the effect of the air-cutting and multi-rotation delayed regeneration described above, in which chatter displacement occurring more than two spindle rotations before is regenerated, and analyze regenerative chatter vibration during vibration cutting in the frequency domain. In this study, the phase difference φ of tool motion in vibration cutting is focused as an important vibration condition parameter that affects the stability limit. In the conventional condition (φ = π), the air-cutting ratio is limited to a relatively low value, and only the dynamic displacements before one and two spindle revolutions are regenerated. On the other hand, setting φ appropriately under the condition φ ≠ π , the air-cutting ratio is increased. Furthermore, the dynamic displacement is regenerated not only before one and two spindle rotations but also before three or more spindle rotations. These results indicate that proper setting of the phase difference φ is effective in suppressing regenerative chatter vibration due to the effects of both the air-cutting phenomenon and multi-rotation delay. Finally, cutting experiments show that the phase difference φ specified by the analysis was effective in suppressing chatter vibration. In summary, the application of low frequency vibration with an appropriately set phase difference φ is an effective strategy for suppressing chatter vibration without reducing the material removal rate in the turning process. [Display omitted] • We performed chatter stability analysis in low frequency vibration cutting. • Chatter stability is affected by vibration cutting parameters. • Phase difference φ and amplitude ratio A / F heavily impact chatter stability. • Using the specific φ depending on A / F is an effective chatter-suppression strategy. [ABSTRACT FROM AUTHOR]

Recently surface textured tools have gained much attention as sustainable machining techniques in enhancing the tribological characteristics at tool and workpiece interfaces. However, minimal research is conducted to inspect the influence of bio-inspired textured tool cutting performances. Therefore in the current investigation, the influence of variation in the rake and flank faced bio-inspired crescent textured tool parameters such as radius, edge distance, depth, and center distance on the cutting performance of difficult to machine martensitic AISI 420 steel has been examined. The turning operation has been conducted at a constant depth (a p) = 0.3 mm, cutting speed (v c) = 315 m/min and feed (f z) = 0.14 mm/rev. The bio-inspired crescent-shaped textured tool indicated a reduction in feed force, tangential force, chip-tool contact area, flank wear and chip reduction coefficient compared to the conventional tool. The built-up edges, chipping, and abrasion are common tool wear mechanisms noticed on the tool surface. It is noticed that out of different texture parameters, center distance of the crescent textured tool played a vital role in improving the machining performance with minimum feed force, tangential force, contact area, flank wear, and chip reduction coefficient of 49 N, 118 N, 7.96 E + 05 µm2, 103 µm and 1.695 is observed using the textured tool of center distance of 80 µm. These research findings are significant for increasing the bio-inspired textured tool applications with superior tribological characteristics. [Display omitted] • Bio-inspired crescent textured tool performed superior compared to conventional tool. • Texture parameters plays vital role in improving machining performances. • BUE, abrasion, and chipping are common tool wear mechanisms observed. • Textured tool showed lower chip reduction coefficient. [ABSTRACT FROM AUTHOR]

• A new four-legged piezoelectric robot, inspired by human butterfly motion, achieves multi-directional movement. • A parallel piezoelectric twin-chip configuration enhances driving force and flexibility. • The robot's piezoelectric legs use varying excitation voltages for precise turning control. • A dynamic model optimizes the robot's structure, improving motion and control accuracy. Piezoelectric micro-robots have gained considerable attention in rescue and medical applications due to their rapid response times and high positioning accuracy. In this paper, inspired by the human butterfly locomotion pattern, we propose a novel resonant four-legged piezoelectric micro-robot designed to achieve fast and efficient movement in complex and confined spaces. The robot utilizes the parallel piezoelectric bimorph as the driving unit, and its leg structure mimics the butterfly motion. By employing asymmetric driving forces, the robot can achieve multi-directional movement. A dynamic model of the robot is developed, and the stress and motion characteristics are analyzed. The finite element method (FEM) is applied to optimize the structural parameters and determine the robot's optimal operating frequency. Finally, the prototype of the piezoelectric robot is constructed, and its performance is evaluated. The results show that, under an excitation voltage of 80 V, the robot achieves a maximum speed of 66.1 mm/s, can carry a load of up to 100 g, and withstand a maximum drag force of 15.3 mN. The robot demonstrates sub-micron resolution, excellent environmental adaptability, and precise rotational capabilities, making it suitable for tasks such as exploration, mapping, and sampling in constrained environments. [ABSTRACT FROM AUTHOR]

Compacted Graphite Iron (CGI) represents a unique combination of the characteristics of grey and spheroidal cast irons, sparking significant interest over the past two decades, particularly as a favoured material in several automotive industry applications, including engine components and heavy-duty vehicle parts. Despite its growing prominence, the full potential of CGI remains underutilised, primarily due to its lower productivity rate compared to grey cast iron. This paper comprehensively reviews existing research on CGI machining, emphasising the challenges and exploring opportunities for development in this field. A detailed comparison between the machining of compacted graphite iron, grey cast iron and spheroidal graphite cast iron is provided, highlighting the unique characteristics associated with CGI. The influence of microstructure and chemical composition on machining processes is thoroughly examined and deliberated. Moreover, this review delves into the effects of various process variables on CGI machining, including cutting tools, lubrication, and cooling methods. The paper concludes by discussing potential future trends and innovations in CGI machining, offering a prospective outlook on how these developments could bridge the productivity and literature gap and enhance the utilisation of CGI in industrial applications. [Display omitted] • CGI machining must be more efficient to meet market demands and increase CGI use. • Focused research isolating variables is crucial for improving CGI machining. • Understanding CGI and tool interactions is key to enhancing CGI machining. • Clarifying how impurities and trace elements in CGI affect CGI machining is needed. • Advanced lubrication and cooling methods can boost sustainable CGI machining. [ABSTRACT FROM AUTHOR]

Improving mobility – specifically walking – is an important treatment goal of total knee arthroplasty. Objective indicators for mobility, however, are lacking in clinical evaluations. This study aimed to compare real-world gait and turning between individuals scheduled for total knee arthroplasty and healthy controls, using continuous monitoring with inertial measurement units. Real-world gait and turning data were collected for 5–7 days in individuals scheduled for total knee arthroplasty (n = 34) and healthy controls (n = 32) using inertial measurement units on the feet and lower back. Gait and turning parameters were compared between groups using a linear regression model. Data was further analyzed by stratification of gait bouts based on bout length, and turns based on turning angle and turning direction. Dominant real-world gait speed was 0.21 m/s lower in individuals scheduled for total knee arthroplasty compared to healthy controls. Stride time was 0.05 s higher in individuals scheduled for total knee arthroplasty. Step time asymmetry was not different between the groups. Regarding walking activity, individuals scheduled for total knee arthroplasty walked 72 strides/h less than healthy controls, and maximum bout length was 316 strides shorter. Irrespective of the size of the turn, turning velocity was lower in individuals scheduled for total knee arthroplasty. Individuals scheduled for total knee arthroplasty showed specific walking and turning limitations in the real-world. Parameters derived from inertial measurement units reflected a rich profile of real-world mobility measures indicative of walking limitation of individuals scheduled for total knee arthroplasty, which may provide a relevant outcome dimension for future studies. • Improving mobility is an important goal of total knee arthroplasty. • We compared mobility of those scheduled for knee arthroplasty to healthy controls. • Pre-arthroplasty individuals walked and turned slower than healthy peers. • Furthermore, they had shorter gait bouts, and walked less during daily life. • Real-world mobility may be a relevant outcome dimension for this group. [ABSTRACT FROM AUTHOR]

Geometric deviations of mechanical products are specified by tolerancing in the design stage for a functional purpose. In order to verify the impact of geometric deviations on functional surfaces while considering the manufacturing process, form defects have been considered in tolerance analysis in recent years. As a digital representation of geometrical defects in mechanical parts and assemblies, Skin Model Shapes enables the rapid and comprehensive generation of non-ideal shapes from either measurement or via data augmentation using simulation approaches. This paper presents a novel method for form defects modeling using Generative Adversarial Networks (GAN). The form defects of cylindrical surfaces considering machining process are represented and used for training a Wasserstein GAN. The pre-trained network is able to generate realistic form defects for cylindrical Skin Model Shapes rapidly and automatically without explicitly formulated representations. Manufacturing errors in turning process are considered in this approach and the generated samples from WGAN can be re-used for generating new cylindrical surfaces with a mapping strategy considering specification. A case study of a cylindricity specification is used in the paper to illustrate the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

A cutting force computational model based on the form-shaping function theory is developed. In the precision machining, small deviations of the geometrical form of the cutting tool and its total run-out can result in significant variation of the instantaneous tool-and-workpiece contact area and depth-of-cut compared to their nominal values. This produces corresponding changes in the instantaneous cutting power and cutting force. As application examples, the surface grinding and precision turning are considered. In the latter case, the machined profile deviations are reduced thanks to the amplitude modulation of the force variations, which depends upon a ratio of rotation to vibration frequencies. The model is verified using the known experimental data. [ABSTRACT FROM AUTHOR]

Insufficient coating adhesion limits reproducibility regarding tool lifetime as well as workpiece quality during the application of CVD-diamond coated cutting tools. Depending on the combination of tungsten carbide substrate material, coating thickness as well as coating morphology, individual residual stress conditions exist within CVD-diamond coated cutting tool specifications. The application of these tools is accompanied by coating delamination as primary cutting tool failure. The tool lifetime of the respective cutting tool composition depends on the corresponding residual stress condition until crack development within the CVD-diamond coating initiates tool failure. During external cylindrical turning of hypereutectic aluminium silicon alloy AlSi17Cu4Mg-T6 the residual stress condition of a CVD-diamond coated cutting tool is assessed along the cutting edge, the rake face as well as flank face throughout the respective tool lifetime. Consequently, the progression of the residual stress condition until cutting tool failure regarding coating delamination is observed. During the tool lifetime of the investigated CVD-diamond cutting tools, compressive residual stress ∆σ R,c shifts to tensile residual stress ∆σ R , t underneath the cutting edge corner. The approximated residual stress difference of ∆σ R ≈ 5 GPa indicates stress peak relaxation processes, such as crack initiation, within the CVD-diamond coating. [ABSTRACT FROM AUTHOR]

Machining titanium alloys such as Ti-6Al-4V results in a high thermomechanical load on cutting tools and consequently short tool lifes. With respect to a necessary reduction of the resulting cutting tool temperatures, ultrashort pulse (USP) laser fabricated micro-textured rake faces offer direct supply of cooling lubricant into the cutting zone and lead to a reduced heat induction. As a result, micro-textured CVD diamond thick film cutting tools are also capable of machining high-performance materials due to reduced contact temperatures. In the scope of the research, the resulting temperature distribution for micro-textured rake faces will be compared under both dry and wet process conditions. Measurements show a reduction of the resulting cutting tool temperatures of Δ ϑt = 27.9 % using micro-textured cutting tools compared to non-textured cutting tools. A validated simulation provides valuable information about the contact temperatures enabling a specific development of the micro-texture geometry. As a result, a reduction of the contact temperature between chip and rake face by Δ ϑ T = 24.7 % was possible. [ABSTRACT FROM AUTHOR]

Finish turning is one of the key operations governing the residual stress of functional surfaces. The residual stress state is determined by the cutting conditions and the selected cutting tool system (macro geometry, cutting edge preparation, tool substrate, multi-layer coating...). However, this initial configuration evolves over time due to tool wear. Therefore, it seems very instructive to reproduce the wear process of the tool in order to understand the evolution of thermo-mechanical loadings applied to the machined surface. Flank wear is a parameter which can be difficult to fully control, and it is complex to reproduce experimentally. In this work, a simple, controlled and repeatable method of producing a known flank wear state is introduced and the impact of the flank wear on the surface integrity is assessed. This involves two parts, first reproducing a given flank wear state and second, evaluating experimentally the residual stress induced by the flank wear state on the workpiece. Carbide tools are used to turn 15-5PH steel under dry conditions. It is shown that the method produces consistent results. The effect of flank wear on residual stress is most notable and can generate data to validate numerical modelling. Areas for improving the method are also discussed. [ABSTRACT FROM AUTHOR]

Residual stresses in the surface layer have a significant impact on the fatigue resistance of machined surfaces. This paper investigates the influence of lubrication mode (flood cooling ⇔ micro quantity lubrication) and of cutting fluid composition (emulsion ⇔ vegetable oil) on the generation of residual stresses in finish turning. First an experimental campaign quantifies the sensitivity of both parameters when turning an austenitic stainless steel 316L, then a numerical model provides some physical explanations on the results. It is shown that the application of a cutting fluid for this application does not influence significantly the residual stress generation. [ABSTRACT FROM AUTHOR]

Finishing of sprayed coatings is required for applications in tribological systems. The mostly hard and wear-resistant coatings cause increased tool wear in machining. Functional coating materials with hardening capacity during machining represent an alternative approach that reduces tool wear and ensures sufficient wear resistance. The research objective is to analyze the hardening potentials of coatings while machining. For the investigations specimens of the steel X120Mn12 are manufactured by spark-plasma sintering and thermal spraying, respectively. Finishing is performed by face turning using tools characterized by different rake angles and by diamond smoothing under varying smoothing force. The geometrical properties and the hardness of the surface are determined. After tribological tests the specimens wear depth is measured. The tool rake angle and the smoothing force affect the surface hardness and the depth of the hardened layer. Additionally, specimens manufacturing process influences the resulting surface properties and the wear resistance. Purposive hardening of coatings by finishing is analyzed for the first time. The results enhance the knowledge about machining of coatings and contribute to an enlargement of their field of application. [ABSTRACT FROM AUTHOR]

The generation of heat during chip removal can affect the residual-stress state and thus the performance of machined parts. For this reason, the aim of this study is to determine and modify the process temperatures in turning of the aluminum alloy EN AW-2017. Therefore, the influence of dry machining, cold-air cooling (CAC), flood lubrication (FL), and minimum quantity lubrication (MQL) is investigated by measuring the temperature with a tool–workpiece thermocouple. In regard to the correlation between the cutting power and the temperature, the cutting speed is varied in the range of 50 m/min to 550 m/min while the depth of cut and the feed are kept constant. The results show that the contact area between the tool and the workpiece has to be considered for the evaluation of the measured temperature as it represents an average value over the tool–workpiece interface area. Since there is only a slight decrease of the process forces with increasing cutting speed, the modification of the surface properties has to be mainly influenced by the change of temperatures. Thus, process cooling entails a reduction of tensile residual stresses as a consequence of a decrease of the cutting temperature. Furthermore, the surface roughness values (Ra, Rz) are smaller when applying cooling lubricant. In contrast for low cutting speeds, the intensified built-up edge (BUE) formation leads to compressive residual stresses but deteriorates the surface quality. Hence, the combination of an effective cooling strategy and the temperature measurement allows for the generation and monitoring of advantageous surface properties during machining. [ABSTRACT FROM AUTHOR]