Rapid Wear Research Articles

The Abrasive Water Jet Cutting Process of Carbon-Fiber-Reinforced Polylactic Acid Samples Obtained by Additive Manufacturing: A Comparative Analysis

Carbon-fiber-reinforced polymer (CFRP) composites are widely used across industries due to their enhanced strength and stiffness properties. Fused deposition modeling (FDM) enables the cost-effective production of polymer samples, such as carbon-fiber-reinforced PLA (CFR-PLA). However, CFRP’s hardness and anisotropic nature present significant challenges in conventional machining, including rapid tool wear and thermal sensitivity. Consequently, abrasive water jet machining (AWJM) has proven to be an effective alternative for machining CFRP materials, offering benefits such as reduced tool wear, minimized thermal damage, and improved cutting quality. This study focuses on a comparative analysis of the effects of AWJM parameters on PLA and CFR-PLA samples, specifically to evaluate the influence of carbon fiber reinforcement on machining performance. The findings highlight the critical role of reinforcements in machining behavior. The results suggest that optimizing cutting parameters significantly reduces taper formation and improves machining accuracy. In particular, adjustments to process parameters resulted in lower taper angles and reduced surface roughness in the cutting zones of the CFR-PLA samples.

Evaluating productivity characteristics of laser engineered net shaping titanium alloy

Advances in Additive Manufacturing (AM) technologies have made it possible to reduce the design and prototyping costs to a minimum especially for a low-productivity material like titanium. Titanium alloys are commonly and widely used alloys in the aerospace and biomedical sector due to their advantageous material properties. This paper is an evaluation study of factors affecting the productivity characteristics of Laser Engineered Net Shaping (LENS) titanium alloy (Ti-6Al-4 V) using face milling. Some of the productivity challenges associated with titanium such as rapid tool wear, poor surface finish, and high-power consumption are explored in this paper. All materials processed using AM face the same critical problem that the manufactured part requires a post machining since AM produces relatively poor surface finish. Machining trials are conducted using the combinations of machining parameters such as spindle speed of 800 and 1600 rev/min; feed rate of 50 and 100 mm/min; and a constant depth of cut of 1 mm, respectively. Titanium being a poor thermal conductivity material, the effect of coolant was investigated using wet/dry machining. Data related to the productivity factors and material behavior under a milling trial was recorded and analyzed. The obtained data from the trials include productivity factors such as Metal Removal Rate (MRR), power consumed, and the surface finish for each plate/trial. The power consumed in dry milling was observed to be lower than that in wet milling which is contrary to the observations from conventional wet milling. The paper concludes the trends observed for LENS titanium are opposed to the trends in conventional machining such as increasing cutting speed will result in lower cutting force and power consumed.

Study on the influence of sediment erosion of Francis turbine runner under different water heads

Abstract The average measured sediment concentration of the river section where Wanjiazhai Hydropower Station is located over the years is 5.7kg/m 3, The maximum measured sediment concentration reaches 37.6kg/m 3, The erosion of the flow components of hydraulic turbines caused by sand containing water flow is becoming increasingly severe, coupled with the frequent impact of load changes during peak shaving operation, the problems exposed during the operation of hydraulic turbines are becoming more prominent, which affects the stable operation of the units. This article uses numerical simulation and experimental testing to study the sediment wear characteristics and hydraulic performance of the water turbine at Wanjiazhai Hydropower Station. Research has revealed the effects of working head on impeller wear. The increase in working head will exacerbate the impact wear on the main channel wall of the unit. The surface of water turbine blades is the main wear area, and the high-speed impact of particles causes an increase in the wall wear rate. The probability of particles coming into contact with the wall at the outlet increases, resulting in rapid wear at this point. The increase in head will intensify the wear intensity of the unit surface, and the flow velocity in the gap indicates that the local high-speed jet in the gap is the main cause of gap wear. Therefore, in order to ensure the efficient anti-wear performance of the water turbine, multiple factors need to be comprehensively considered to cope with sediment wear of the water turbine, including regular cleaning, optimized structural design, use of wear-resistant materials, replacement of worn parts, and optimization of operating parameters. These measures help to reduce the damage of sediment wear to water turbines and extend their service life.

Performance evaluation of machine learning algorithms in predicting machining responses of superalloys

This study explores the application of machine learning algorithms—gene expression programming (GEP), adaptive neuro-fuzzy inference system (ANFIS), and artificial neural networks (ANN)—to predict machining responses during the milling of Inconel 690, a superalloy known for its exceptional mechanical properties and oxidation resistance. Machining Inconel 690 presents significant challenges due to its toughness and work-hardening tendencies, which can lead to rapid tool wear and poor surface finish. Traditional optimization methods often rely on empirical models and trial-and-error approaches, which are time-consuming and costly. In contrast, machine learning techniques can effectively model complex, nonlinear relationships between machining parameters and performance outcomes, such as surface roughness, cutting force, and cutting temperature. This study employs statistical metrics, including Root mean square error (RMSE), coefficient of determination (R2), and mean absolute percentage error (MAPE), to determine the predictive performance of the models. The results show that the GEP model achieved an R2 ranging from 0.944 572 to 0.992 999, with an RMSE between 0.015 527% and 0.694 523% and a MAPE ranging from 1.452 397% to 4.947 892%. ANFIS and ANN also demonstrated strong predictive capabilities, although GEP outperformed them. The importance of this study lies in its demonstration of advanced AI techniques as effective tools for optimizing machining processes, ultimately contributing to improved efficiency and quality in manufacturing superalloys.

Magnetic and ultrasonic vibration dual-field assisted ultra-precision diamond cutting of high-entropy alloys

Despite the remarkable achievements in single-energy field-assisted diamond cutting technology, its performance remains unsatisfactory for processing high-entropy alloys (HEAs), targeted for next-generation large-scale industrial applications due to their exceptional properties. The challenge lies in overcoming the limitations of current single-energy field-assisted processing to achieve ultra-precision manufacturing of these advanced materials. This study proposes a multi-energy field-assisted ultra-precision machining technology, the magnetic and ultrasonic vibration dual-field assisted diamond cutting (MUVFDC), to address the current challenges. The phenomenological aspects of the dual-field coupling effect on HEAs are explored and investigated through comprehensive characterization of the workpiece material, ranging from macroscopic surface morphology to microscopic structural features. These analyses are performed based on experimental results from four different processing technologies: non-energy field, magnetic field, ultrasonic vibration field, and dual-field assisted machining. Research results demonstrate that MUVFDC technology effectively combines the advantages of a vibration field, which enhances cutting stability, and a magnetic field, which improves the machinability of materials. Additionally, this coupling technology addresses the challenges associated with single-energy field machining: it mitigates the difficulty of controlling surface scratches caused by tiny hard particles in a vibration field and suppresses the rapid tool wear encountered in a magnetic field. Furthermore, the gradient evolution of the subsurface microstructure reveals that the vibration field suppresses the severe matrix deformation induced by magnetic excitation. Simultaneously, the magnetic field reduces the size inhomogeneity of recrystallized grains caused by intermittent cutting. Overall, MUVFDC technology enhances surface quality, suppresses tool wear, smooths chip morphology, and reduces subsurface damage compared to single-energy field or non-energy-assisted machining. This work breaks through the performance limitations of traditional single-energy field-assisted processing and advances the understanding of the dual-field coupling effects in HEAs machining. It also presents a promising processing technology for the future ultra-precision manufacturing of advanced materials.

Wear behavior of white alumina and seeded gel abrasive wheels in ultrasonic vibration-assisted grinding of nickel-based single-crystal alloy

This study investigated the tool wear behavior of white alumina (WA) and seeded gel (SG) abrasive wheels in the ultrasonic vibration-assisted creep feed grinding (UVACFG) of nickel-based single-crystal alloy. The abrasive wheel wear characteristics were examined, and their effects on the grinding force, temperature, and surface quality were evaluated. Finally, the wheel wear mechanism in the UVACFG was discussed by analyzing the intermittent cutting behavior and wear patterns of a single grain. Experimental results indicated that the workpiece material adhesion and pore-clogging were the main wear patterns of abrasive wheels without ultrasonic vibration. In contrast, these were adequately mitigated after introducing ultrasonic vibration, and the main wear pattern for both wheels became the grain fracture. The WA wheel in the UVACFG experienced reduced radial wear by around 60.7 % in the initial wear state, 40.2 % in the stable wear state, and 25.3 % in the rapid wear stage, respectively, compared to the conventional grinding (CG). The intermittent cutting behavior of SG grains caused by high-frequency vibration promoted the micro-fracture capacity and ensured the coolant entered the grinding zone sufficiently, which reduced the grinding force and temperature by up to 63.2 % and 46.7 %, respectively, and meanwhile introduced the defects of high bulges and slight plastic deformation on the workpiece surface.

Components of the development of methods for calibrating rollers for rolling channels based on changed non-uniformsty of deformation

Introduction. In metallurgy, the final stage of production is metal processing in rolling shops. The main component of the development of technologies for rolling graded profiles is the calibration of rolls. 90% of the steel that is smelted is processed by rolling. Rolling mill calibration methods are constantly being improved. Calibration methods are used in which there is a significant uneven deformation of the profile elements, which leads to rapid wear of the rolls and an increase in costs. Formulation of the problem. It is necessary to develop a method of calibrating rolls in the production of channels based on the reduction of deformation unevenness. Goal. The purpose of the article is to analyze the methods of calibrating rolls for the production of channels with an indication of their advantages and disadvantages and to justify the application of the components of the developed method of calibrating rolls based on the reduction of unevenness of deformation. The results. The analysis of various methods of calibrating channel rolls showed that the smallest unevenness of deformation is present in the method of rolling by the bending method. The greatest uniformity of deformation along the width of the profile is achieved, the wear of the rolls is reduced in connection with ensuring a minimum difference in the diameters of the rolls in the gauge, and energy costs are reduced. To reduce the uneven deformation of the metal, it is suggested to use a rectangular blank or strip. Scientific novelty. For the first time, the methods of calibrating rolls for channel rolling were analyzed in detail. To reduce uneven deformation of shelves and flanges in the center of deformation in the gauge, it is proposed to use the bending calibration method. It is proposed to use strips as a blank for the first time. Practical meaning. The application of channel rolling technology based on the developed method of calibrating rolls with reduced unevenness of deformation in the first passes allows to reduce the cost of products and give an economic effect

Wire-cut electrical discharge machining of duplex stainless steel: a study

ABSTRACT In this study, the duplex stainless steel is machined using a wire-cut electrical discharge machining process to overcome the issues of poor finishing, lower dimensional accuracy, and rapid wear of cutting tools in conventional machining processes. The higher rate of material removal and superior finish on the machine surface is dependent on kerf loss, which is expressed as the mean kerf width assessed at certain locations. Nevertheless, this approach is typically not effective in explicating the intricacies of true kerf loss due to the random selection of distinctive points. This work proposes an area-based measuring approach to quantify the kerf loss by taking into account any imperfections on the kerf wall. At the pulse on time of 20 μs and current of 3 A, the machining appears not stable. The pulse on time, current, and voltage of 12 µs, 1 A, and 80 V proved suitable for obtaining excellent dimensional precision.

In-situ tool wear condition monitoring during the end milling process based on dynamic mode and abnormal evaluation

Rapid tool wear conditions during the manufacturing process are crucial for the enhancement of product quality. As an extension of our recent works, in this research, a generic in-situ tool wear condition monitoring during the end milling process based on dynamic mode and abnormal evaluation is proposed. With the engagement of dynamic mode decomposition, the real-time response of the sensing physical quantity during the end milling process can be predicted. Besides, by constructing the graph structure of the time series and calculating the difference between the predicted signal and the real-time signal, the anomaly can be acquired. Meanwhile, the tool wear state during the end milling process can be successfully evaluated. The proposed method is validated in milling tool wear experiments and received positive results (the mean relative error is recorded as 0.0507). The research, therefore, paves a new way to realize the in-situ tool wear condition monitoring.

Tribological Behaviour of Short Carbon Fiber Reinforced Polyethersulfone Composites with PTW Filler

In various applications like bearings, gear pairs, and brake pads, understanding how polymer composites interact with harder counterparts during sliding motions is crucial. A challenge arises from the heat generated during sliding friction, which has the potential to raise the contact temperature. This temperature increase, if it exceeds the material's glass transition temperature, can compromise the thermal stability of the composites, leading to rapid material wear. In the present investigation, dry sliding wear test was performed on 25 wt. % of short carbon fiber (SCF) reinforced polyethersulfone (PES) composites filled with 2.5 and 5.0 wt. % of potassium titanate whisker (PTW) using pin-on-disc tribometer. Wear test was planned and executed according to the experiment design formulations obtained by central composite design method. Contact temperature at the interface between composite pin and steel disc was monitored with an infrared thermal camera. Wear resistance was found to increase with the addition of fibers and fillers. PTW filled composites exhibited minimum wear with maximum coefficient of friction. Morphology studies were carried out on worn surfaces of the composites using scanning electron microscope to identify and describe the mechanism of wear involved. This investigation sheds light on the intricate behavior of polymer composites during sliding interactions.

Investigation of tool wear and energy consumption in machining Ti6Al4V alloy with uncoated tools

This research studies the energy consumption and wear mechanism of carbide cutting tools in dry machining of Ti6Al4V alloy. In the first phase of experiments, full factorial design experiments were employed to study the tool wear rate (R) and specific cutting energy (SCE) with respect to the machining conditions (cutting speed and feed rate). Results showed that machining responses such as tool wear and energy consumption are affected by cutting conditions, thus requiring investigation to understand the wear mechanisms. Therefore, in the second phase, additional experiments were performed to investigate the tool-workpiece interactions at the cutting conditions reported to have low, moderate, and high tool wear. It was revealed that strong adhesion and material transfer between the tool and workpiece caused high wear. Electron dispersive X-ray spectroscopy (EDX) analysis of worn tools showed that the transfer of tungsten (W) and cobalt (Co) to the workpiece and titanium to the tool surface is the primary cause of tool deterioration. As a result, diffusion and dissolution have degraded cutting performance and weakened the tool edge, leading to rapid wear. Furthermore, worn tools resulted in relatively higher energy consumption per unit volume of material removed at the tooltip. The degradation of cutting performance and weakening of the tool edge results in rapid wear and higher energy consumption. The study suggests that minimizing tool wear is crucial for energy reduction, improved sustainability, and cleaner production goals in dry machining of titanium-based alloys.

Different Shades of Green: An Analysis of the Occupational Health and Safety Risks Faced by Wind Farm Workers

The growth of the wind power sector has been marked by environmental, economic, and political drivers. Its starring role is also visible in the emergence of the so-called “green jobs”. Notwithstanding, its evolution ought not to compromise issues related to occupational risks. This exploratory study examines psychosocial risks in the operation and maintenance of onshore wind turbines in a leading Portuguese company. We conducted interviews with main stakeholders (human resources, OHS professionals, and team leaders); developed an “activity diary” for the operation and maintenance technicians to describe their activity and perceived impacts on health, complemented with collective interviews; and applied the Work and Health Survey. The results revealed the following particular risks and health impacts: working under adverse weather conditions, working at heights and in confined spaces, spending long work hours inside of the nacelles to achieve an optimum balance between favourable wind slots to intervene and avoiding additional trips up and down the wind turbines without lifts (70–120 m), and the feeling of early ageing. At a time when these workers are striving for recognition of their profession as a “rapid wear profession”, it is a pivotal moment to discuss these results to guarantee sustainable conditions for future generations of workers.

Requirements for vibroacoustic methods of the quality assessment of vehicles traction electric motors

The progression and refinement of traction electric motors play a pivotal role in the enhancement of vehicles. With constant advancements in power efficiency, diagnostic tools, and reliability, electric traction motors are becoming more economical in terms of operational costs. This article underscores the significance of methods used in assessing the technical proficiency of traction electric motors, coupled with their testing techniques. The vibration characteristics of these motors serve as a prime criterion in assessing their quality throughout their lifecycle – from design and manufacturing to operation. A groundbreaking proposition made in this article is the evaluation of electric traction motors’ health based on their vibration acceleration within an expansive frequency range of 5 Hz to 10 kHz. This contrasts the conventional approach which focuses on vibration speed in a restricted frequency spectrum up to 1000 Hz, as outlined by current standards. Such permissible vibration classes are essential in ensuring the high-quality design, technical finesse, and dependability of traction electric motors. Exceeding these vibration thresholds can result in rapid wear and tear, diminishing the motor’s reliability and lifespan. Hence, motors that surpass these permissible vibrations are not advised for vehicular use. Additionally, the article sheds light on requisite equipment controls for accurately gauging vibrations and noise levels in electric motors. Delving deeper into the nuances, the methods for mounting vibration transducers and electric motors on testing platforms are elucidated. These methods are pivotal in obliterating any hindrances that could impede the precise measurement of vibrations induced by an electric motor.

Optimizing Retention Bunkers in Copper Mines with Numerical Methods and Gradient Descent

This study examines the optimization of ore receiving bins in underground copper mines, targeting the reduction of rapid wear and tear on bin components. The investigation identifies the primary wear contributors as the force exerted by the accumulated ore and the velocity at which ore particles move. By altering design and operational parameters, the objective is to decrease wear at key points such as transfer areas, thereby improving the efficiency and service life of retention bunkers. A Discrete Element Method (DEM) model of the bin was created and validated against actual mining conditions to study the impact of material flow on wear. The optimization approach used a constrained gradient descent algorithm to minimize factors like particle velocity and pressure force, while maintaining the efficiency of the bin. The findings provide valuable insights for the future design enhancements, potentially improving the operational performance of retention bunkers in the mining industry.

Ultrasonic vibration cutting of advanced aerospace materials: a critical review of in-service functional performance

PurposeUnconventional machining processes, particularly ultrasonic vibration cutting (UVC), can overcome such technical bottlenecks. However, the precise mechanism through which UVC affects the in-service functional performance of advanced aerospace materials remains obscure. This limits their industrial application and requires a deeper understanding.Design/methodology/approachThe surface integrity and in-service functional performance of advanced aerospace materials are important guarantees for safety and stability in the aerospace industry. For advanced aerospace materials, which are difficult-to-machine, conventional machining processes cannot meet the requirements of high in-service functional performance owing to rapid tool wear, low processing efficiency and high cutting forces and temperatures in the cutting area during machining.FindingsTo address this literature gap, this study is focused on the quantitative evaluation of the in-service functional performance (fatigue performance, wear resistance and corrosion resistance) of advanced aerospace materials. First, the characteristics and usage background of advanced aerospace materials are elaborated in detail. Second, the improved effect of UVC on in-service functional performance is summarized. We have also explored the unique advantages of UVC during the processing of advanced aerospace materials. Finally, in response to some of the limitations of UVC, future development directions are proposed, including improvements in ultrasound systems, upgrades in ultrasound processing objects and theoretical breakthroughs in in-service functional performance.Originality/valueThis study provides insights into the optimization of machining processes to improve the in-service functional performance of advanced aviation materials, particularly the use of UVC and its unique process advantages.

Enhancement of Wear Resistance of High-Load Pressing Screw in Smokeless Charcoal Production by Using Genetic Algorithm and Discrete Element Method

During the production of smokeless charcoal, the pressing screw of the sawdust compressor is exposed to the effects of friction and elevated temperature, resulting in rapid wear. This phenomenon not only diminishes productivity but also exerts adverse influences on the final product's quality. Consequently, the pursuit of research endeavors aiming at prolonging the lifespan of the pressing screw holds significant importance, not only in reducing production costs but also in enhancing the product's overall quality. This paper adopts an innovative approach by integrating theoretical calculations, numerical simulations with practical experiments to ascertain the optimal profile for the pressing screw. This methodology employs Genetic Algorithm and Discrete Element Method (DEM) simulations in conjunction with the EDEM software to simulate the working process and provide the optimal profile of the pressing screw. The analysis and simulation results indicate a substantial enhancement in the wear resistance of the pressing screw while ensuring the efficient movement of discrete materials during the pressing process. The results of this study not only indicate the main wear locations on the pressing screw but also suggest the optimal profile, providing a basis and control for wear assessment. Furthermore, the results of this research not only identifies the principal areas that are susceptible to wear on the pressing screw but also proposes optimal profile, threreby establish a solid foundation and methodology for wear assessment. These results will be pragmatically implemented in smokeless charcoal production factories, concurrently pave the way for further research and applications in this field.

The development and research of a novel biodegradable technology for the regeneration of microdamages and regulation of the elasticity of delicate fabrics during laundry washing cycles

The synthetic textiles are most responsible for non-biodegradable microplastic release during laundry washing cycles. European directives try to promote and encourage the use of natural textiles, such as delicate fabrics, as a new ecological approach. Delicate fabrics aren’t resistant to multiple microdamages by commercial products with proteases, rapid wear, loss of elasticity and fabric strength, and colour fading due to protein structure of these fibers. The aim of this research was to evaluate the beneficial effects of transglutaminase (TGase) in household products for the regeneration of microdamages and regulation of the elasticity of delicate fabrics during laundry washing cycles. In the present study, the effects of TGase on silk and wool were investigated by modern methods: scanning electron microscopy (SEM) and deformation-strength technique using Shimadzu AG 10kNX. SEM showed that the bonds formed by TGase exhibited high resistance of fibers before and after protease application. TGase in laundry washing gel provided the restoration of silk and wool fibers up to 85% after 10 washing cycles. The elasticity of delicate fibers was increased by 16% after 1 wash cycle. The strength of silk and wool was improved by 2 and 5 times, respectively, with decrease in fiber elongation. Thus, TGase can be promising compound to provide the deep regeneration of microdamages and increase longevity of delicate fabrics.

Cutting Performance and Tool Wear of AlCrN- and TiAlN-Coated Carbide Tools during Milling of Tantalum–Tungsten Alloy

Tantalum–tungsten alloys have been widely used in different industrial sectors—for example, in chemical, medical, aerospace, and military equipment. However, they are usually difficult to cut because of the large cutting force, rapid tool wear, and poor surface finish during machining. This paper presents the machining performance and cutting tool wear of AlCrN/TiAlN-coated carbide tools during the milling process of Ta-2.5W. The effects of cutting parameters on the cutting forces and surface roughness of AlCrN/TiAlN-coated carbide tools were obtained and analyzed. The results show that the wear resistance of AlCrN-coated tools is better than that of TiAlN-coated tools, and that the main wear mechanisms of both cutting tools are crater wear, adhesive wear, and diffusion wear. Compared to TiAlN-coated tools, AlCrN-coated tools reduced the cutting forces by 1% to 15% and decreased the surface roughness by 6% to 20%. A cutting speed within the range of 80–120 m/min can ensure a low cutting force while maintaining good surface roughness, which is more conducive to machining Ta-2.5W.

Quality enhancement of micro-milled channels with automated laser assistance

AbstractMicrochannels are utilised on material surfaces of a body, allowing coolant to pass through them and enabling heat dissipation by increased contact area. Fabrication of metal surface microchannels is primarily achieved by employing a micro-milling process, which has drawbacks such as excessive cutting forces, top burrs, tool wear, and lower tool life. Alternatively, it is also realised by using Laser micro milling, which has problems associated with lower quality of surface finish, un-desired taper, heat-affected zone, and spatters. The existing literature, after due review of the current state of the art, has brought out gaps needing attention. These gaps are limited capability to reduce surface roughness, unaddressed burr width, and irregular bottom surface morphology, which affect microchannel quality. These gaps motivate this research work to improve and sustain the microchannel quality. To achieve the goals, this research work performs the fabrication of microchannels by micro-milling with automated laser assistance being achieved in two ways (a) sequentially, (b) non-sequentially, termed as LASMM and LPCMM, which are novel for the scientific community. The effects of micro milling parameters, spindle speed and feed on the quality were analysed while machining commercially pure titanium (cp-Ti). Results show that laser assistance to micro-milling provides a lower generation of undesired forces and lesser top burrs compared to micro-milling alone. In sequential laser assistance, the channels have a mean down burr width ~ 58% lower and a maximum down burr width ~ 38% lower than the channels done non-sequentially. In the case of up-burr width, a mean value ~ 60% lower and a maximum value ~ 73% lower is achieved in channels done non-sequentially as compared to those done sequentially. In the case of surface roughness, channels done sequentially have a maximum Sa value of 1.508 µm, a maximum Sq value of 1.912 µm whereas non-sequentially, they show a maximum Sa value of 3.495 µm, maximum Sq value of 4.59 µm. Steady tool wear is observed sequentially, whereas in non-sequential, rapid tool wear occurs after 500 mm of cutting length.

Model-free finite frequency H∞ control for active chatter suppression in turning

Regenerative chatter is an extremely harmful phenomenon in machining, which generally results in overcut and rapid tool wear. This paper presents the design, analysis, and verification of a novel model-free finite frequency band (MFFFB) H∞ control algorithm, which is dedicated to chatter suppression of turning process. The proposed MFFFB H∞ controller is established by utilizing the reinforcement Q-learning along with the generalized Kalman-Yakubovich-Popov (GKYP) lemma. Unlike available entire frequency domain (EFD) H∞ controllers, the proposed approach facilitates a less conservative implementation since the H∞ performance index is only designed for the concerned frequency band which implies the limited energies of the actuator are mainly focused on this band, and users can specify optimized frequency band according to the actual turning conditions. Furthermore, it permits the construction of H∞ controller without any knowledge of the dynamic model of turning process, only the data measured from the system state and input are required. Besides, an iterative solution algorithm for H∞ control on the basis of policy iteration is presented, which decreases the burden on manual parameter adjustment and capable of achieving the optimal solution. Simulation and experiment results demonstrate that the proposed MFFFB H∞ controller generates significant improvement in chatter-free region compared with EFD H∞ controller and conventional FFB H∞ controller.