J. Manuf. Mater. Process., Volume 7, Issue 2 (April 2023) – 29 articles

This paper describes a hybrid manufacturing approach for silicon carbide (SiC) freeform surfaces using binder jet additive manufacturing (BJAM) to print the preform and machining to obtain the design geometry. Although additive manufacturing (AM) techniques such as BJAM allow for the fabrication of complex geometries, additional machining or grinding is often required to achieve the desired surface finish and shape. Hybrid manufacturing has been shown to provide an effective solution. However, hybrid manufacturing also has its own challenges, depending on the combination of processes. For example, when the subtractive and additive manufacturing steps are performed sequentially on separate systems, it is necessary to define a common coordinate system for part transfer. This can be difficult because AM preforms do not inherently contain features that can serve as datums. Additionally, it is important to confirm that the intended final geometry is contained within the AM preform. The approach described here addresses these challenges by using structured light scanning to create a stock model for machining. Results show that a freeform surface was machined with approximately 70 µm of maximum deviation from that which was planned. Full article

Including the inherent temporal variability in a production system in planning and control processes can ensure the fulfillment of the production schedule and increase key performance indicators. This benefits the sustainable and efficient use of the system. The current lack of consideration of this inherent temporal variability in production planning leads to optimistic estimates and calculations of planned values that cannot be met. To complete this information, the inherent temporal variability in a production system is investigated using a systematic approach. This approach detects, identifies, and quantifies inherent temporal variability and is applied to a data base created via an automated, event-driven procedure. The approach is tested in a smart factory laboratory. The results to date on improving production planning and control are promising as key performance indicators have been increased. There is still a need for action to ensure the fulfillment of the production schedule. Concluding, work on this topic has just begun, as can be seen from the discussion section. More data need to be collected and aggregated for future research. This publication is intended to motivate researchers to address this issue and better manage the existing uncertainty in production through the use of data. Full article

This work deals with the experimental investigation and multi-objective optimization of mean kerf angle (A) and mean surface roughness (Ra) in laser cutting (LC) fused filament fabrication (FFF) 3D-printed (3DP), 4 mm-thick polylactic acid (PLA) plates by considering laser feed (F) and power (P) as the independent control parameters. A CO₂ laser apparatus was employed to conduct machining experiments on 27 rectangular workpieces. An experimental design approach was adopted to establish the runs according to full-combinatorial design with three repetitions, resulting in 27 independent experiments. A customized response surface experiment was formulated to proceed with regression equations to predict the responses and examine the solution domain continuously. After examining the impact of F and P on mean A and mean Ra, two reliable prediction models were generated to model the process. Furthermore, since LC is a highly intricate, non-conventional machining process and its control variables affect the responses in a nonlinear manner, A and Ra were also predicted using an artificial neural network (NN), while its resulting performance was compared to the predictive regression models. Finally, the regression models served as objective functions for optimizing the responses with an intelligent algorithm adopted from the literature. Full article

This study provides a comprehensive analysis of the one-shot drilling (CFRP) strategy for machining CFRP materials in the assembly of aircraft components, focusing on key factors such as tool wear, hole delamination, and the evolution of machining forces. The research uses adapted parts of the tail-cone structure of a commercial aircraft as workpieces and employs large-diameter cutting tools to perform drilling operations, with results that can be readily applied to the industry. The study selects cutting conditions by analyzing the effect of cutting parameters on tool life in drilled holes and accumulated cutting time, with the end-of-life criterion based on the extension of the wear suffered by the main cutting edge of the first step. The results show that all tested cutting conditions achieve a similar value of tool life expressed in terms of holes drilled, with differences smaller than 7%. However, one of the cutting conditions analyzed completes the same number of holes within 40% less time. Therefore, considering productivity criteria, it will be interesting to evaluate the use of high values for the cutting parameters. Overall, this research provides valuable insights for improving the efficiency and effectiveness of CFRP machining in aircraft manufacturing. Full article

This paper proposes a genetic algorithm approach to solve the identical parallel machines problem with tooling constraints in job shop flexible manufacturing systems (JS-FMSs) with the consideration of tool wear. The approach takes into account the residual useful life of tools and allocates a set of jobs with specific processing times and tooling requirements on identical parallel machines. Two metrics are introduced to evaluate the scheduling decisions and optimize the scheduling process, with the competitive goal of maximizing tool utilization and minimizing production makespan. The proposed approach searches for a set of optimal solutions on the Pareto front that offers the best possible balance between these two objectives, achieving optimal local performance in terms of both makespan and tool utilization. The approach is implemented with a customized genetic algorithm and validated on a real case study from a company operating in the aerospace sector, which confirms its effectiveness in increasing tool utilization and reducing the makespan. The results show that the proposed approach has significant practical implications for the manufacturing industry, particularly in the production of high-value materials such as those in the aerospace sector that require costly tools. This paper contributes to the operational research community by providing advanced scheduling algorithms that can optimize both the makespan and the tool utilization concurrently, improving production efficiency and maintaining competitiveness in the manufacturing industry. Full article

Computer-aided manufacturing (CAM) techniques for hybrid manufacturing have led to new application areas in the manufacturing industry. In the tooling industry, cooling channels are used to enable specific heating and cooling cycles to improve the performance of the process. These internal cooling channels have been designed with limited manufacturing processes in mind, so, until recently, they were often straight in shape for cross-drilling operations and manufactured from a cast billet. To show a novel application of this common technology, a tool with integrated conformal cooling channels was manufactured using hybrid manufacturing (blown-powder DED and CNC machining) techniques. The computer-aided manufacturing strategy used, and the lessons learned are presented and discussed to enable future work in this industrial application space. Full article

Electrical resistivity was used in this test methodology to estimate the relative precipitate density in AA7075. Various electrical test parameters were explored to determine the difference between pulsed and DC-type currents. No difference between these test conditions could be distinguished. Furthermore, an electroplastic effect was not needed to explain these results and the effects are likely to be caused by purely joule heating. Full article

The paper presents the microstructural characterization of the chip roots in high-speed steels and ceramic Ti₃SiC₂. The process of chip formation and the obtaining of adequate samples were carried out using the quick-stop method. The tests were carried out during the milling process; the “quick stop” method was carried out in order to obtain samples of the chip roots. This method was developed in-house by the authors. The chip roots were microscopically studied by means of a light microscope (LM) and a scanning electron microscope (SEM). Before the actual analysis, preparation was performed based on the standard metallographic technique. The analysis of the high-speed steels samples showed that, for the used cutting conditions, a discontinuous chip with a built-up edge (BUE) was formed. During the processing of the Ti₃SiC₂ ceramic, a significant difference was manifested in the chip formation process and a powder-like chip was produced. After utilizing a careful cutting process, a chip pattern was observed, from which it is evident that chip breakage during ceramic processing occurs without prior plastic deformation. In addition, the cutting force F_c was also measured during the milling process of the high-speed steels and the ceramic, and it was correlated with the cutting speed, feed per tooth and depth of cut. Full article

The processes of metal additive manufacturing (AM) are no longer confined to rapid prototyping applications and are seeing increasing use in many fields for the production of tools and finished products. The ability to design parts with practically zero waste, high precision, complex geometry, and on-demand fabrication are among the advantages of this manufacturing approach. One of the drawbacks of this technique is the productivity rate, as the parts are made layer by layer, which also increases the production cost. Moreover, even the working space is limited, especially for the powder bed fusion technique. In view of these disadvantages and in order to guarantee the profitability of this process, it should be oriented to the production of complex components that have a limited volume with a design adapted to additive manufacturing. One solution with which to circumvent these drawbacks is to combine the 3D printing process with conventional manufacturing processes. When designing products, one may choose to use additive manufacturing to create locally complex parts and assemble them with parts produced by conventional processes. On the other hand, and due to the limited AM printing chamber space, it may be necessary to print large parts in multiple smaller parts and then assemble them. In order to investigate the weldability of stainless steel 316L parts produced by laser powder bed fusion (L-PBF), the mechanical behavior of different welding assemblies is tested. Five configurations are studied: non-welded AM specimens, two AM parts welded together, one AM part and one laser cut part welded together, two laser-cut parts welded together, and non-welded laser cut specimens. Welding is performed using the Pulsed Gas Metal Arc Welding process (GMAW-P). Specimen strength is assessed through static and fatigue tests. The results demonstrate that 316L AM parts are weldable, and the tensile and fatigue properties of L-PBF 316L welded components and welded laser cut components are comparable. GMAW-P welding led to lower fatigue results for AM components than for other configurations, but the difference is not important. It was observed that welding defects may have a direct impact on mechanical properties. Full article

Incremental forming (IF) is an advanced manufacturing process in which a forming tool locally deforms sheet material into a desired geometry through successive passes at incremental depths. An inherent benefit to the IF process is its formability improvement over conventional stamping; however, further enhancements will enable the forming of increasingly complex geometries. To progress the IF process towards heavy industrial use, the modeling of such processes must be further developed. Single point incremental forming (SPIF) of AA2024-T3 was modeled herein utilizing explicit formulations. The model geometry featured a nominally rectangular-shaped clamping region. A friction factor was experimentally determined and utilized within the model, which is a novel addition to this work. Formability was determined and forming limit diagrams were composed. It was found that the present model shows greater formability and underestimates plastic strain compared to experimental testing. The generation of forming limit diagrams for this material processed by IF is also a novel addition to this field. Full article

Additive manufacturing (AM) technologies for metallic materials allow for the manufacturing of high-performance components optimised in weight, geometry, and mechanical properties. However, several post-processing operations are needed after production, including removing parts from the build platform. This operation is essential and must be performed rapidly, precisely, and with a good surface finishing. This work presents an experimental investigation of the wire electric discharge machining (W-EDM) process of Ti6Al4V specimens produced by AM technologies. The influence of cutting parameters is analysed compared to the material produced by conventional technology. Models of cutting speed and surface roughness obtained by a W-EDM are inferred from the collected data. Remarkably, the results show that the manufacturing process used to produce the components plays a crucial role in defining the final surface roughness and the most significant parameters affecting the machining performance. Full article

In this study, monocrystalline silicon was ablated by a single 1030 nm femtosecond laser pulse. Variable laser fluence (0.16–3.06 J/cm²) was used, and two ablation thresholds (0.8 and 1.67 J/cm²) were determined experimentally. A two-temperature model was established based on the dynamic optical model, the carrier density model, and the phase explosion model for comparison with experimental results. The melting (0.25 J/cm²) and vaporization (0.80 J/cm²) thresholds were determined when the lattice temperature reached melting and boiling points, so as to overcome the latent heat. Finally, the ablation depth was calculated using the phase explosion model, and the ablation threshold was 1.5 J/cm². The comparisons show that the proposed model can predict the ablation depth obtained by a single femtosecond laser pulse. Full article

This work characterises the structure and mechanical properties, such as adhesion, of two different chemical vapour deposition (CVD) coatings deposited onto silicon aluminium oxynitride (Si₃N₄ + Al₂O₃ + Y₂O₃) round (RNGN) milling cutter tooling inserts. These inserts are often known by the trade abbreviation “SiAlON”. Wear was produced on the inserts using unidirectional sliding (pin-on-disc type) and scratch testing. Two coatings were investigated: a multilayer CVD coating (Coating A) with a composition of TiN + TiCN + Al₂O₃ and a bilayer coating (Coating B) with a composition of Al₂O₃ + TiN. Microstructural analysis was conducted after wear testing and Coating B demonstrated high stability when subjected to high alternating shear and tensile stresses, high abrasion resistance and very high adhesion to the SiAlON ceramic insert substrate when compared to Coating A. Coating A demonstrated a low capacity to distribute alternating shear and tensile stresses during the pin-on-disc and scratch testing, which led to failure. The scratch and pin-on-disc results from this study correlate highly with completed machining insert wear analysis that has used Coating A and Coating B SiAlON inserts to machine aged Inconel 718. Full article

The suitability of the direct energy deposition process of exothermic powders Fe-Ti in joining dissimilar metals to produce small parts of a complete shape for various applications is considered. The procedure of the direct energy deposition of commercial pure iron and titanium in various proportions and the modes of the process are described. Optical microscopy and SEM with EDX analysis, X-ray analysis, and microhardness measurements of laser-fabricated intermetallics are applied. Intermetallic compounds of FeTi, Fe₂Ti, eutectoids, complex titanium oxides and nitrides, and iron carbides are found. Interlayer and trans-layer cracks and pores are observed. A microhardness growth from 150 HV to 900 HV was obtained for all samples due to the precipitation of brittle intermetallic phases in the gradient Fe-Ti system during the DED. The dispersion of microhardness values becomes significant in Ti-rich areas; there, pores and cracks are found. The revealed structure features are considered in relation to published results and explained. Increased concentrations of Ti to Ti + Fe = 3:1 on the Fe- and Fe + Ti -substrate with concentrations of Ti + Fe = 1:1 and Ti + Fe = 1:3 lead to increasing hardness and its distribution, but also increases in residual microstress. Recommendations are given to reduce the power during the direct energy deposition of titanium layers and to apply Fe-substrate, which can reduce residual stress, pores, and cracks. Full article

A vibration-damping steel panel is used for lightweight vehicles to block any noise subjected to the passenger cabin replacing heavy fiber-based insulators. Conventional weld joining methods often encounter problems due to the presence of viscoelastic compounds reducing the joint quality and making the joining process unproductive. In this work, we present experimental results that show the self-piercing riveting (SPR) process can be used to produce high-quality joints between vibration-damping steel and (i) commonly used steel alloy (SPFC590DP), (ii) carbon-fiber-reinforced-plastic (CFRP) panels. Various die shapes are used to investigate the resulting interlock width and bottom thickness of the joints and tensile shear load tests were performed to evaluate the joining strength. The results show that high-quality joints between vibration-damping steel and the steel alloy are possible for all the dye types and panel configurations, used in this study, producing up to 6.2 kN of tensile shear load. High-quality joints were also possible with CFRP producing up to 4.0 kN, however, acceptable joints were formed only when the CFRP panels were on top during the riveting process due to severe cracking. Full article

Additively manufactured thin-walled structures through selective laser melting (SLM) are of great interest in achieving carbon-neutral industrial manufacturing. However, residual stresses and warpages as well as recoater crashes often occur in SLM, leading to the build failure of parts, especially for large-scale and lightweight geometries. The challenge in this work consists of investigating how the recoater affects the warpage and (sometimes) causes the failure of different thin-walled Ti6Al4V parts (wall thickness of 1.0 mm). All these parts are printed on the same platform using a commercial SLM machine. After the loose powder removal and before the cutting operation, a 3D-scanner is used to obtain the actual warpage of each component. Next, an in-house coupled thermo-mechanical finite element model suitable for the numerical simulation of the SLM process is enhanced to consider the recoater effects. This numerical framework is calibrated to predict the thin-walled warpage as measured by the 3D-scanner. The combination of numerical predictions with experimental observations facilitates a comprehensive understanding of the mechanical behavior of different thin-walled components as well as the failure mechanism due to the recoater. The findings show that the use of a higher laser energy input causes larger residual stresses and warpage responsible for the recoater crashes. Finally, potential solutions to mitigate the warpage and the recoater crashes in the SLM of lightweight structures are assessed using the validated model. Full article

Additive manufacturing of material systems sensitive to heat degradation represents an essential prerequisite for the integration of novel functionalized material systems in medical applications, such as the hybrid processing of high-performance thermoplastics and gelling polymers. For enabling an inherent process stability under non-isothermal conditions at reduced ambient temperatures in laser-based additive manufacturing, maintaining a homogeneous layer formation is of vital significance. To minimize crystallization-induced deflections of formed layers while avoiding support structures, the temporal and spatial discretization of the melting process is combined with the subsequent quenching of the polymer melt due to thermal conduction. Based on implementing superposed, phase-shifted fractal curves as the underlying exposure structure, the locally limited temporal and spatial discretization of the exposure process promotes a mesoscale compensation of crystallization shrinkage and thermal distortion, enabling the essential homogeneous layer formation. For improving the understanding of local parameter-dependent thermal intra-layer interactions under non-isothermal processing conditions, geometric boundary conditions of distinct exposure vectors and the underlying laser power are varied. Applying polypropylene as a model material, a significant influence of the spatial distance of fractal exposure structures on the thermal superposition of distinct exposure vectors can be derived, implicitly influencing temporal and temperature-dependent characteristics of the material crystallization and the emerging thermal material exposure. Furthermore, the formation of sub-focus structures can be observed, contributing to the spatial discretization of the layer formation, representing a decisive factor that influences the structure formation and mesoscopic part properties in non-isothermal powder bed fusion of polymers. Consequently, the presented approach represents a foundation for the support-free, accelerated non-isothermal additive manufacturing of both polymers and metals, demonstrating a novel methodology for the mesoscale compensation of thermal shrinkage. Full article

The damage layer produced during the Niobium sheets and cavity fabrication processes is one of the main reasons why cavities have to undergo an extensive surface preparation process to recover optimal superconducting properties. Today, this includes the use of lengthy, costly, and dangerous conventional polishing techniques as buffered chemical polishing (BCP), or electro-polishing (EP). We propose to avoid or at least significantly reduce the use of acids. We developed a novel method based on metallographic polishing of Nb sheets, consisting of 2–3 steps. We demonstrate that this surface processing procedure could be transferred to large dimensions and an industrialized scale thanks to the limited number of steps and its compatibility with standard lapping polishing devices. Full article

The roughness origin of machined surfaces is caused by the following physical causes: the copying of the shape and the roughness of the cutting part of the tool into the workpiece, the existence of vibration of the tool, and the existence of the build-up edge (BUE) on the cutting edge. The current work aims to analyze the vibration amplitude of tools. The roughness of the machined surfaces was observed on hardened steel workpieces. Internal turning technology was used, and we used several different boring bars (steel; carbide; tuned mass damper—TMD; impact damper—ID) and an internal turning operation using CBN inserts. We revealed the tool’s slenderness coefficient (TSC) values for stable cutting operations. For the steel holder, the value is TSC ≤ 4.25; for the carbide holder, the value is TSC ≤ 5.5; for the TMD holder, the value is 4.5 ≤ TSC ≤ 7.75; and for the ID holder, the value is TSC ≤ 8. The surface’s roughness was practically unchanged within the limits of stable machining. However, if the tools exceed the presented stable limits, vibration and roughness parameters deteriorate significantly; an example parameter (Ra) deteriorated from 0.350 μm to 1.832 μm. Full article

Consistent high volumetric performance of machine tools is an essential requirement for high-quality machining. Periodic machine tool calibration ensures said performance and allows for timely corrective actions preventing scrap or rework. Reducing the duration of the calibration process decreases associated cost through non-productive downtime and allows for data acquisition in thermal real-time. The authors enhance an indirect calibration method based on measuring points within the machine volume using a laser tracker by removing the necessity for standstill. To circumvent requiring high fidelity space and time synchronization between metrology system and machine tool, only deviations perpendicular to the path are considered. To do so, the 3D laser tracker data are rotationally transformed such that one axis aligns with the motion direction and can subsequently be omitted as input data for the system of equations solving for geometric errors. Due to the absence of unique measurement-point-to-machine-point mapping, data alignment between nominal path and measurement data is proposed as an iterative alignment process of points to path. The method is tested simulatively and experimentally. It demonstrated conformity to the simulation as well as to the pre-existing calibration method based on laser trackers and shows good agreement with the direct calibration device API XD Laser. Full article

A hybrid approach based on laser texturing and surface coating for the combined modification of surface topography and chemistry has been proposed to provide a versatile approach for the development of functional surfaces. The experimental procedure comprised nanosecond pulsed laser texturing of AISI 304 stainless steel substrates followed by the deposition of thin (<1 µm) coatings with two different technologies, sol–gel deposition and PE-CVD, with the aim of independently modifying the surface topography and chemical composition. Laser texturing with different scanning strategies achieved a variety of surface morphologies with an arithmetic mean height (S_a) in the range 0.2–6.4 µm. Coatings were then deposited on laser-textured substrates to quantify the deposition effectiveness and the influence of the coating type and parameters on the resulting surface topography and chemistry. Sol–gel deposition was found to be more effective with a polymeric interlayer, improving adhesion between the coating and the textured surface; however, this also led to an increase in Sa of approximately 0.5 µm. Conversely, PE-CVD was effective in modifying the surface chemistry while inducing no measurable differences in surface morphology, effectively decoupling the texturing and coating processes. Analysis of the surface chemistry showed a higher concentration of silicon for PE-CVD than sol–gel deposition and therefore a more pronounced effect on the surface chemical composition. Full article

The technology of additive manufacturing (AM) has transformed the fields of machinery, aerospace, and electronics. Adopting cost-effective, precise, and rapid procedures in AM is one of the major concerns of today’s industry. Stereolithography is a promising AM technique that is thought to meet these requirements. However, the fact that materials printed with stereolithography do not have good mechanical properties limits their application, such as in biomedicine and aerospace. Previous studies have shown the shortcomings of stereolithography printers. This research focuses on enhancing the mechanical characteristics of the polymer resin used in stereolithography (SLA)-like liquid crystal display (LCD) 3D printers by fabricating a new AM composite material with carbon fibers. For this reason, chopped carbon fibers (0.1 mm size) at amounts of 0.25 wt% and 0.5 wt% have been used with Acrylonitrile butadiene styrene (ABS)-like photopolymer transparent resin during the printing process, and three different print layer thicknesses were tested. For the design of the experiment (DoE), Q-DAS software was used to analyze the resulting data. A tensile-testing machine was utilized to determine the ultimate strength using the ASTM D638 standard. The results show an increase in the ultimate strength by adding carbon fiber to some extent, but after a certain percentage of carbon fiber added, the strength drops off. Full article

The synthesis of advanced materials at high pressures has been an area of growing research interest for several decades. This article is the third in a three-part series that reviews Laser Materials Processing Within Diamond Anvil Cells (L-DACs). Part III focuses on the practice of Laser Reactive Synthesis Within Diamond Anvil Cells (LRS-DAC). During LRS-DAC processing, chemicals are precompressed within diamond anvil cells, then microscale chemical reactions are induced by focused laser beams. The method is distinguished from the well-known Laser-Heated Diamond Anvil Cell (LH-DAC) technique (see Part I) through the existence of chemical precursors (reactants), end-products, and quantifiable changes in chemical composition upon reaction. LRS-DAC processing provides at least three new degrees of freedom in the search for advanced materials (beyond adjusting static pressures and temperatures), namely: laser-excitation/cleavage of chemical bonds, time-dependent reaction kinetics via pulsed lasers, and pressure-dependent chemical kinetics. All of these broaden the synthetic phase space considerably. Through LRS-DAC experimentation, it is possible to obtain increased understanding of high-pressure chemical kinetics—and even the nature of chemical bonding itself. Here, LRS-DAC experimental methods are reviewed, along with the underlying chemistry/physics of high-pressure microchemical reactions. A chronology of key events influencing the development of LRS-DAC systems is provided, together with a summary of novel materials synthesised, and unusual chemical reactions observed. Current gaps in knowledge and emerging opportunities for further research are also suggested. Full article

During the pulsed laser ablation of metals, as well as other materials, the development of a plasma plume close to the ablated surface leads to the emission of radio frequency energy. In this paper, we describe a process for analysing the received radio frequency power (RFP) for an aluminium (Al) surface ablation process in atmosphere using picosecond laser pulses at a wavelength of 1064 nm. The analysis of the RFP was carried out on two sets of experiments, where two parameters of the laser (repetition rate of laser (RRL) and power of laser (PL)) were varied while other parameters remained constant. In addition to the RFP measurement during the laser processing, the spatter area (SA), which is defined in this paper, and the depth of the ablated hole were measured post-process using a 3D microscope. It was observed that there is a direct relationship between (RFP)² and SA. Accordingly, an appropriate RF calibration was performed, which leads to the definition of a quantity called the RF regulation % (RFR%). By comparing the RFR and PL/RRL variations, to which the laser beam fluence is proportional in these experiments, a diagnostic process (i.e., flowchart) for real-time depth evaluation was proposed and experimentally confirmed. This diagnostic process can indicate if the depth of the laser ablated crater is less than or exceeds a predetermined depth, which in this study was set to 15 µm. It is also demonstrated that the SA variation can be estimated in real-time by analysing the received RF power and, secondly, the depth of ablation can be measured in real time using a combination of information from the received RF power and laser parameters. Full article

A distinctive characteristic of the powder bed fusion with electron beam (PBF-EB) process is the sintering of the powder particles. For certain metallic materials, this is crucial for the success of the subsequent step, the melting, and, generally, the whole process. Despite the sintering mechanisms that occur during the PBF-EB process being similar to well-known powder metallurgy, the neck growth rates are significantly different. Therefore, specific analyses are needed to understand the influence of the PBF-EB process conditions on neck growth and neck growth rate. Additionally, some aspects, such as the rigid body motion of the particles during the sintering process, are still challenging to analyze. This work systematically investigated the effects of different particle diameters and particle diameter ratios. Additionally, the impact of the rigid body motion of the particles in the sintering was analyzed. This work demonstrated that the sintering results significantly depended on the EB-PBF process conditions. Full article

Cryogenic rolling is one of the essential severe plastic deformation processes to manufacture high-strength aluminum sheets with excellent formability limits. The present work characterizes the formability of AA6061 for cryogenic rolling before and after artificial aging. Nakajima method based on ISO standard is used to measure formability. Samples are aged in the range of 100 °C to 150 °C. Artificial aging at 150 °C is found to be the optimum temperature for achieving a good combination of strength and formability. Over the course of artificial aging, strength improved up to 40%, where the original value of 250 MPa for cryo-rolled condition increased to 350 MPa after 50 h of aging at 150 °C, and the formability of the cryo-rolled sample improved especially for multi-axial forming condition. Full article

Large cylindrical worm gear set of ISO type I are manufactured using endmill tools on universal CNC machine tools. This manufacturing method requires neither special gear-generating machines nor special tools. The tooth flank forms of ISO type I cylindrical worm gears are involute helicoids as a standard. The targeted theoretical tooth flanks of the worm and the mating worm wheel are determined based on a tooth contact analysis (TCA) of such worm gear set. The cutting conditions of the worm are determined after the offset distance between the worm axis, and the central axis of the endmill tool is calculated. Afterward, the worm is manufactured by controlling only two axes on machine tools using a swarf milling method by use of the side of the endmill tool under the determined conditions. Meanwhile, the targeted theoretical tooth flanks of the mating worm wheel are modeled in 3-dimensional computer-aided design software, and the worm wheel is manufactured by a swarf milling method in a computer-aided manufacturing process. The comparison of experimental and analytical tooth contact patterns indicates almost no difference between the two tooth contact patterns. Full article

Several physics-based models have been utilized in material design for the simulation and prediction of material properties. In this study, several machine-learning (ML) approaches were used to construct a prediction model to analyze the influence of equal-channel angular pressing (ECAP) parameters on the microstructural, corrosion and mechanical behavior of the biodegradable magnesium alloy ZK30. The ML approaches employed were linear regression, the Gaussian process, and support vector regression. For the optimization of the alloy’s performance, experiments were conducted on ZK30 billets using different ECAP routes, channel angles, and number of passes. The adopted ML model is an adequate predictive model which agreed with the experimental results. ECAP die angles had an insignificant effect on grain refinement, compared to the route type. ECAP via four passes of route Bc (rotating the sample 90° on its longitudinal axis after each pass in the same direction) was the most effective condition producing homogenous ultrafine grain distribution of 1.92 µm. Processing via 4-Bc and 90° die angle produced the highest hardness (97-HV) coupled with the highest tensile strength (344 MPa). The optimum corrosion rate of 0.140 mils penetration per year (mpy) and the optimum corrosion resistance of 1101 Ω·cm² resulted from processing through 1-pass using the 120°-die. Grain refinement resulted in reducing the corrosion rates and increased corrosion resistance, which agreed with the ML findings. Full article

Alloyed carbon steels used in ground engaging tools (GETs), such as shovel-teeth, can withstand high working loads, but their wear resistance is inadequate for abrasive operations in the mining industry. Different approaches to engineer protective surfaces on GETs for improving wear resistance have been developed over the years, but the effectiveness of the applied abrasive resistance layer has been limited by the maximum thickness that can be realized reliably. Considering wear requirements for GETs to reach end-of-life without requiring unscheduled maintenance for after-failure repairs, a minimum thickness of 25 mm has been postulated for the abrasive resistance surface layer, which is roughly four times greater than the thickness of overlays currently manufacturable by weld deposition technologies. Thus, in this study, a novel approach for conceiving thick abrasive surface protection layers—that are unlimited in thickness—on GETs is presented. The method involves applying solid-state linear friction welding and was demonstrated to be feasible for joining abrasive-resistant CPM 15V tool steel to an alloyed carbon steel (extracted from a shovel-tooth). After welding, the integrity of the joints was examined microscopically using optical and scanning electron microscopy to understand the microstructural characteristics, as well as through microhardness and tensile testing to evaluate the performance. A high frequency welding condition was identified that provided integral bonding (i.e., without voids and cracking) at the interface between the CPM 15V tool steel and alloyed carbon shovel-tooth steel. In the as-welded condition, the measured hardness profiles across the joints showed minor softening of both base materials in the heat-affected zone just adjacent to the weld center; this was attributed to over aging of the tempered martensite structures of CPM 15V tool steel and alloyed carbon shovel-tooth steel. The maximum tensile strength of the joint (553 MPa) provides evidence for the viability of linear friction welding technology for joining protective surface materials on GETs. Full article