Journal of Manufacturing and Materials Processing — Open Access Journal

In this paper, a new method was introduced for feature extraction and fault diagnosis in bearings based on wavelet packet decomposition and analysis of the energy in different frequency bands. This method decomposes a signal into different frequency bands using different types of wavelets and performs multi-resolution analysis to extract different features of the signals by choosing energy levels in different frequency bands. The support vector machines (SVM) technique was used for faults classifications. Daubechies, biorthogonal, coiflet, symlet, Meyer, and reverse Meyer wavelets were used for feature extraction. The most appropriate decomposition level and frequency band were selected by analyzing the variation in the signal’s energy level. The proposed approach was applied to the fault diagnosis of rolling bearings, and testing results showed that the proposed approach can reliably identify different fault categories and their severities. Moreover, the effectiveness of the proposed feature selection and fault diagnosis method was significant based on the similarity between the wavelet packet and the signal, and effectively reduced the influence of the signal noise on the classification results. Full article

In the following work, we propose a metallurgical approach to the chip formation process. We focus on a turning application of high strength steel in which chips are produced by adiabatic shear bands that generate cutting force signals with high frequency components. A spectral analysis of these signals is applied and highlights peaks above 4 kHz depending on the cutting conditions. A microscopic analysis on the chip sections provided data on chip breaking and serration mechanisms. Shear band spacing and excitation frequency of the whole cutting system were calculated and gave a good correlation with cutting forces spectra. Full article

In this fundamental work, a series of experiments were performed to define the optimal amount of dispersant and solid content for feedstock with and without ceramic fibers (Nextel 610). Based on these fixed conditions, investigations were carried out to discover the effects of binder system, fiber sizing, and increasing fiber content on mixing and viscosity. In addition, the effects of kneading temperature and time, fiber sizing, and different binder systems on fiber length were investigated using a measuring mixer, high-pressure capillary rheometer, and microscopy. Stearic acid, as a dispersant, modified the particle surface and improved the rheological properties. Moreover, increasing the solid content in the feedstocks led to an exponential growth of final torque and relative viscosity, because of the increasing friction between particles. Paraffin wax (PW)- and polyethylene glycol (PEG)-based feedstocks showed different mixing behaviors and rheological results with increasing fiber, whereas PEG-based feedstocks had higher final torques and kneading energies without fibers, whilst PEG feedstocks displayed lower viscosities. Consequently, during kneading, the amount of fiber has been predominating over fiber length, and the effect of the binder, the kneading temperature, and time did not cause significant changes. Full article

In this study, AA5754 sheet samples joined by using a friction stir spot welding method using different rotational speed parameters has been analyzed experimentally. During the experiments, rotational speed of the tool was changed while other process parameters and the tool geometry were kept constant. The effect of tool rotational speed on the hardness values, macrostructure, and tensile properties of joints has been investigated and the results of the experiments show the best tensile shear strength and hardness values are obtained for the tool rotation speed of 1850 rpm. According to the macroscopic investigation, all of the fractured samples failed by nugget pullout and the fractured samples have only a single type fracture pattern. Full article

This paper describes the collection of a large dataset (6930 measurements) on dimensional error in the fused deposition modeling (FDM) additive manufacturing process for full-density parts. Three different print orientations were studied, as well as seven raster angles ($0^{\circ }$, ${15}^{\circ }$, ${30}^{\circ }$, ${45}^{\circ }$, ${60}^{\circ }$, ${75}^{\circ }$, and ${90}^{\circ }$) for the rectilinear infill pattern. All measurements were replicated ten times on ten different samples to ensure a comprehensive dataset. Eleven polymer materials were considered: acrylonitrile butadiene styrene (ABS), polylactic acid (PLA), high-temperature PLA, wood-composite PLA, carbon-fiber-composite PLA, copper-composite PLA, aluminum-composite PLA, high-impact polystyrene (HIPS), polyethylene terephthalate glycol-enhanced (PETG), polycarbonate, and synthetic polyamide (nylon). The samples were ASTM-standard impact-testing samples, since this geometry allows the measurement of error on three different scales; the nominal dimensions were $3.25$ mm thick, $63.5$ mm long, and $12.7$ mm wide. This dataset is intended to give engineers and product designers a basis for judging the accuracy and repeatability of the FDM process for use in manufacturing of end-user products. Full article

In minimum quantity lubrication (MQL), an aerosol containing a minimum amount of the cutting fluid is delivered to the tool/workpiece interface during the metal cutting operation. The fluid lubrication by the fluid and the cooling by the compressed air in the aerosol improves the cutting process, while the low consumption rate in MQL provides less cleanup and reduces the associated cost. In this paper, molybdenum disulfide (MoS₂) and hexagonal boron nitride (hBN) nanoparticles were added to the aerosol for providing a third functionality to the MQL, which is solid lubrication at the interface. Both orbital drilling and tribological testing using a four-ball tester were studied to examine the effectiveness of solid lubrication in MQL. In orbital drilling of titanium with tungsten carbide tools, MQL with nanofluids containing MoS₂ nanoparticles resulted in less transfer film buildup on the tool. In four-ball testing, MQL with nanofluids with MoS₂ and hBN nanoparticles yielded lower surface temperatures and less variation of frictional torques in titanium. Full article

Titanium and its alloys are often used for corrosion protection because they are able to offer high chemical resistance against various corrosive media. In this paper, shrouded plasma spray technology was applied to produce titanium coatings. A solid shroud with an external shrouding gas was used to plasma spray titanium powder feedstock with aim of reducing the oxide content in the as-sprayed coatings. The titanium coatings were assessed by optical microscope, scanning electron microscopy, X-ray diffraction, LECO combustion method and Vickers microhardness testing. The results showed that the presence of the shroud and the external shrouding gas led to a dense microstructure with a low porosity in the plasma-sprayed titanium coatings. The oxygen and nitrogen contents in the titanium coating were kept at a low level due to the shielding effect of the shroud attachment and the external shrouding gas. The dominant phase in the shrouded titanium coatings was mainly composed of α-Ti phase, which was very similar to the titanium feedstock powders. The shrouded plasma-sprayed titanium coatings had a Vickers microhardness of 404.2 ± 103.2 HV. Full article

The potential of adaptronic applications has been proven in many conceptual studies. A broad use in high-efficiency branches is often hindered by the absence of an appropriate assembly method. Especially for piezoceramic foil transducers, the application on structural parts can be simplified using a semi-finished part that includes the transducer. The part is then shaped in a final forming operation. The purpose of the present study is the investigation of process limits in automated process chains for producing semi-finished parts. An adhesive is used in the process, which is only locally cured. This bi-conditioned state is achieved using cooling and heating elements. The process limits are mainly affected by the choice of temperature and curing time between adhesive application and forming operation. Several tests with a rotational rheometer were carried out to investigate the curing behavior. An appropriate process window was identified varying processing time and temperature. The results were then used to build a model of the curing behavior. A mathematical approach had to be used to find the best configuration because no sharp border exists between the two adhesive conditions of liquid and solid state. The process parameters were proven with runs inside and outside of the process limits. Full article

In the one-step manufacturing process for fiber metal laminate parts, the so-called in situ hybridization process, the fabrics are interacting with metal blanks. During deep drawing, the liquid matrix is injected between the metal sheets through the woven fiber layers. The metal blanks can be in contact with dry or with infiltrated fibers. The formability of the blanks is influenced by the variation of the starting time of injection. The reason for that is that, due to high contact forces, the fibers are able to deform the metal surface locally, so that movement and the strain of the blanks is inhibited. To investigate the influence of different fibers on the formability of metals, Nakazima tests are performed. In these tests, two metal blanks are formed with an interlayer of fibers. The results are compared with the formability of two blanks without any interlayer. It is shown that in with fibers between sheets, the formability decreases compared to the formability of two metal blanks without interlayers. Based on a simplified numerical model for different types of fibers, the interactions of the fibers with the metal blank are analyzed. It could be shown that the friction due to contact has more influence than the friction due to the form fit caused by the imprints. Full article

It was found that the ultrasonic spot welding may serve as an efficient method to join relative large thin-walled parts made of fiber-reinforced thermoplastics. In this study, a new control method for the ultrasonic spot-welding process was investigated. It was found that, when welding fiber-reinforced thermoplastic laminates without energy directors, overheating and decomposition of the polymer at the weld spot occurred. The occurrence of the overheating took place at unpredictable times during welding. It was observed that the time trace of the consumed power curve by the welder follows a similar pattern as the time trace of the temperature in the weld spot center. Based on this observation, a control system was developed. The time derivative of the welder power was monitored in real time and, as soon as it exceeded a critical value, the ultrasonic vibration amplitude was actively adjusted through a microcontroller. The controlling of the ultrasonic welding process forced the temperature in the weld spot to remain in an adequate range throughout the welding duration for the polymer diffusion to occur. The results of the controlled welding process were evaluated by means of weld temperature measurements, computed tomography scans, and microscopic analysis of the weld spot fracture surfaces. Full article

The absorptivity of laser radiation of metals is investigated in several studies. Therefore, absorption coefficients depending on temperature or roughness are known. However, many processes use iterative processing strategies, such as additive manufacturing, laser beam bending, or laser-assisted incremental forming. Simulations of these processes often use literature data for absorption coefficients and do not consider the variation of absorptivity during the process. In this study, the influences of multiple laser beam processing on absorptivity are investigated for stainless steel sheets. Absorption and roughness measurements are compared before and after heating treatments with the laser beam or in an oven. It is shown that an increasing amount of laser heating cycles correlates with higher absorptivity and higher roughness values. However, this increase of roughness is not considered to be sufficient for enhanced absorptivity. On the one hand, similar changes of absorptivity were detected when heating steel sheets in an oven. These oven-heated specimens do not show extensive roughness changes. On the other hand, the same amount of laser heating cycles with additional cool down time after each cycle results in a negligible absorptivity change. Therefore, the variation of the absorptivity is attributed to oxidation. Full article

The most accepted method for determining friction conditions in metal forming is the ring compression test (RCT). At high temperatures, extraction of the friction coefficient, μ, commonly requires numerical analysis due to the coupling between the mechanical and thermal fields. In the current study, compression tests of cylindrical specimens and RCT experiments were conducted on commercially pure aluminium (Al1050) at several temperatures, loading rates, and lubrication conditions. The experiments were used in conjunction with a coupled thermo-mechanical finite element analysis to study the dependence of the friction coefficient on those parameters. It is demonstrated that due to the coupling between friction conditions and material flow stress, both μ and flow stress data should be determined from the cylinder and ring specimens simultaneously and not subsequently. The computed friction conditions are validated using a novel method based on identification of the plastic flow neutral radius. It is shown that, due to heat loss mechanisms, the experimental system preparation stage must be incorporated in the computational analysis. The study also addresses the limitation of the RCT in the presence of high friction conditions. The computational models are finally used to examine the thermo-mechanical fields, which develop during the different processes, with an emphasis on the effect of friction conditions, which were then correlated to the resulting microstructure in the RCTs. Full article

Many manufacturing sectors require high surface finishing. After machining operations such as milling or drilling, undesirable burrs or insufficient edge finishing may be generated. For decades, many finishing processes have been on a handmade basis; this fact is accentuated when dealing with complex geometries especially for high value-added parts. In recent years, there has been a tendency towards trying to automate these kinds of processes as far as possible, with repeatability and time/money savings being the main purposes. Based on this idea, the aim of this work was to check new tools and strategies for finishing aeronautical parts, especially critical engine parts made from Inconel 718, a very ductile nickel alloy. Automating the edge finishing of chamfered holes is a complicated but very important goal. In this paper, flexible abrasive tools were used for this purpose. A complete study of different abrasive possibilities was carried out, mainly focusing on roughness analysis and the final edge results obtained. Full article

This paper focuses on the non-destructive dielectric measurement for low-loss planar materials with a thickness of less than 3 mm using a large coaxial probe with an outer diameter of 48 mm. The aperture probe calibration procedure required only to make a measurement of the half-space air and three offset shorts. The reflection coefficient for the thin material is measured using a Keysight E5071C network analyzer from 0.3 MHz to 650 MHz and then converted to a relative dielectric constant, ε_r and tangent loss, tan δ via closed form capacitance model and lift-off calibration process. Average measurement error of dielectric constant, Δε_r is less than 6% from 1 MHz to 400 MHz and the resolution of loss tangent, tan δ measurement is capable of achieving 10⁻³. Full article

Currently, because of stricter environmental standards and highly competitive markets, machining operations, as the main part of the manufacturing cycle, need to be rigorously optimized. In order to simultaneously maximize the production quality and minimize the environmental issues related to the grinding process, this research study evaluates the performance of minimum quantity lubrication (MQL) grinding using water-based nanofluids in the presence of horizontal ultrasonic vibrations (UV). In spite of the positive impacts of MQL using nanofluids and UV which are extensively reported in the literature, there is only a handful of studies on concurrent utilization of these two techniques. To this end, for this paper, five kinds of water-based nanofluids including multiwall carbon nanotube (MWCNT), graphite, Al₂O₃, graphene oxide (GO) nanoparticles, and hybrid Al₂O₃/graphite were employed as MQL coolants, and the workpiece was oscillated along the feed direction with 21.9 kHz frequency and 10 µm amplitude. Machining forces, specific energy, and surface quality were measured for determining the process efficiency. As specified by experimental results, the variation in the material removal nature made by ultrasonic vibrations resulted in a drastic reduction of the grinding normal force and surface roughness. In addition, the type of nanoparticles dispersed in water had a strong effect on the grinding tangential force. Hybrid Al₂O₃/graphite nanofluid through two different kinds of lubrication mechanisms—third body and slider layers—generated better lubrication than the other coolants, thereby having the lowest grinding forces and specific energy (40.13 J/mm³). It was also found that chemically exfoliating the graphene layers via oxidation and then purification prior to dispersion in water promoted their effectiveness. In conclusion, UV assisted MQL grinding increases operation efficiency by facilitating the material removal and reducing the use of coolants, frictional losses, and energy consumption in the grinding zone. Improvements up to 52%, 47%, and 61%, respectively, can be achieved in grinding normal force, specific energy, and surface roughness compared with conventional dry grinding. Full article

Injection molding has been increasing for decades its share in the production of polymer components, in comparison to other manufacturing processes, as it can assure a cost-efficient production while maintaining short cycle times. In any production line, the stability of the process and the quality of the produced components is ensured by frequently performed metrological controls, which require a significant amount of effort and resources. To avoid the expensive effect of an out of tolerance production, an alternative method to intensive metrology efforts to process stability and part quality monitoring is presented in this article. The proposed method is based on the extraction of process and product fingerprints from the process regulating signals and the replication quality of dedicated features positioned on the injection molded component, respectively. The features used for this purpose are placed on the runner of the moldings and are similar or equal to those actually in the part, in order to assess the quality of the produced plastic parts. For the purpose of studying the method’s viability, a study case based on the production of polymer microfluidic systems for bio-analytics medical applications was selected. A statistically designed experiment was utilized in order to assess the sensitivity of the polymer biochip’s micro features (μ-pillars) replication fidelity with respect to the experimental treatments. The main effects of the process parameters revealed that the effects of process variation were dependent on the position of the μ-pillars. Results showed that a number of process fingerprints follow the same trends as the replication fidelity of the on-part μ-pillars. Instead, only one of the two on-runner μ-pillar position measurands can effectively serve as product fingerprints. Thus, the method can be the foundation for the development of a fast part quality monitoring system with the potential to decrease the use of off-line, time-consuming detailed metrology for part and tool approval, provided that the fingerprints are specifically designed and selected. Full article

Keyhole laser welding experiments with 1.5 mm thick aluminum sheets (EN AW-6082) were carried out with transversal beam oscillation and wire feeding. A circular cavity, which was named buttonhole, formed directly behind the laser spot at certain oscillation frequencies. The welding states “no buttonhole”, “unstable buttonhole”, and “stable buttonhole” were distinguished. The melt pool dynamics were experimentally analyzed and correlated with the resulting roughness and waviness of the seam surfaces. Criteria for stable buttonhole welding were derived. On the basis of the cavity radii relations, it is shown that capillary pressure conditions can explain the movement of the buttonhole with the process. Full article

Remanufacturing is a viable option to extend the useful life of an end-of-use product or its parts, ensuring sustainable competitive advantages under the current global economic climate. Challenges typical to remanufacturing still persist, despite its many benefits. According to the European Remanufacturing Network, a key challenge is the lack of accurate, timely and consistent product knowledge as highlighted in a 2015 survey of 188 European remanufacturers. With more data being produced by electric and hybrid vehicles, this adds to the information complexity challenge already experienced in remanufacturing. Therefore, it is difficult to implement real-time and accurate remanufacturing for the shop floor; there are no papers that focus on this within an electric and hybrid vehicle environment. To address this problem, this paper attempts to: (1) identify the required parameters/variables needed for fuel cell remanufacturing by means of interviews; (2) rank the variables by Pareto analysis; (3) develop a casual loop diagram for the identified parameters/variables to visualise their impact on remanufacturing; and (4) model a simple stock and flow diagram to simulate and understand data and information-driven schemes in remanufacturing. Full article