J. Manuf. Mater. Process., Volume 1, Issue 2 (December 2017) – 12 articles

The laser powder bed fusion (L-PBF) technology was adapted for use with non-spherical low-cost water-atomized iron powders. A simplified numerical and experimental modeling approach was applied to determine—in a first approximation—the operation window for the selected powder in terms of laser power, scanning speed, hatching space, and layer thickness. The operation window, delimited by a build rate ranging from 4 to 25 cm³/h, and a volumetric energy density ranging from 50 to 190 J/mm³, was subsequently optimized to improve the density, the mechanical properties, and the surface roughness of the manufactured specimens. Standard L-PBF-built specimens were subjected to microstructural (porosity, grain size) and metrological (accuracy, shrinkage, minimum wall thickness, surface roughness) analyses and mechanical testing (three-point bending and tensile tests). The results of the microstructural, metrological and mechanical characterizations of the L-PBF-built specimens subjected to stress relieve annealing and hot isostatic pressing were then compared with those obtained with conventional pressing-sintering technology. Finally, by using an energy density of 70 J/mm³ and a build rate of 9 cm³/h, it was possible to manufacture 99.8%-dense specimens with an ultimate strength of 330 MPa and an elongation to failure of 30%, despite the relatively poor circularity of the powder used. Full article

The purpose of this paper is to develop a theoretical derivation on aligning discontinuous carbon fiber with an applied electric field, and prove the theory with experiment. A principle with regard to the occurrence of carbon fiber alignment is presented after an introduction of the electromechanical quantities of dielectrics. Based on this principle, an estimation of the polarizability tensor is employed to calculate the required electric field to achieve fiber alignment in liquid solution (e.g., water, resin, etc.). Individual carbon fiber is modeled as a polarizable dielectric cylinder in liquid resin and its motion under direct current (DC) electrical field is decomposed into a polarization effect and rotation effect. A value of 20.12 V/mm is required to align short carbon fibers (0.15 mm) long in liquid resin and is experimentally validated. Finally, an expression to include weight percentage as a means of controlling pearl-chain formation is derived to change the composite’s electrical conductivity. Full article

Dual-phase high carbon steel is widely used in mining and in chemical industry applications in highly abrasive environments due to its excellent hardness and abrasion resistance. In recent years, the use of less expensive but more corrosive solutions in industrial processes has become more common. As a result, detailed understanding of the corrosion behaviour of dual-phase high carbon steel is needed; an issue that has, to date, been little-studied. This study investigates in detail the corrosion behaviour of dual-phase high carbon steel in a sodium chloride solution at different times, at the macro- and nano-scale, using various techniques. Using scanning electron microscopy (SEM) and 3D laser-scanning confocal microscopy, the corrosion behaviour of this important industrial steel was investigated at the micro-scale, then by using atomic force microscopy (AFM) it was further investigated at the nano-scale. The results reveal preferential corrosion attack on the retained austenitic phase, rather than the martensite phase, which is due to the carbon partitioning between martensite and austenite in this grade of steel. Full article

Rotary ultrasonic machining (RUM) is a nontraditional and cost-effective machining method for hard and brittle materials, such as ceramics, optical glass, composite materials, and so on. RUM is a hybrid process that combines the material removal mechanisms of diamond abrasive grinding and ultrasonic machining. In RUM, a rotating cutting tool with metal-bonded diamond abrasive particles is ultrasonically vibrated in the axial direction while the tool spindle is fed toward the workpiece at a constant feedrate to remove material. It has been reported that continuous rotary ultrasonic machining has been successfully used to drill holes in K9 glass. Intermittent rotary ultrasonic machining is a newly introduced ultrasonic machining process, which uses a slotted cutting tool instead of a common metal bonded diamond cutting tool as used in continuous rotary ultrasonic machining. There has been no reported study to compare the effects of intermittent RUM and continuous RUM when machining K9 glass. This paper, for the first time, presents an experimental investigation to compare intermittent RUM and continuous RUM when machining K9 glass from the perspectives of cutting force, surface roughness, and chipping size. Full article

The core technique of electric storage water heaters is the manufacture of the tanks, and the welding technique is the key technology of the tank manufacture. A company producing water heaters received feedback from its after-sales that a large quantity of water leakage from the tanks was found in the market. A follow-up on the manufacturing site by the researchers showed that the position of the water leakage defects mostly happens in the welds of the tanks. Series of experiments were conducted to investigate the mechanical properties, residual stress, and diffusible hydrogen content of the longitudinal weld of the tank. Results of the mechanical properties showed that both the micro-hardness and the tensile strength of the welds are higher than the base metal. There are higher residual compressive stresses in the weld center and the adjacent-weld zone. Vertical residual compressive stress decreases first and then increases (149 MPa–28 MPa–134 MPa) from the weld ends to the middle, whilst the transversal stress decreases continuously (332 MPa~240 MPa) from the weld center to the heat affected zone. After enameling, the longitudinal welds’ peak micro-hardness of coarse grained region reduces by 30.9 HV1, and the average micro-hardness of the HAZ reduces by 5 HV1. The average vertical residual compressive stress difference of the same test points reduces from 270.6 MPa to 20.4 MPa. It proves that enameling can improve the mechanical property of the longitudinal welds. Full article

In the present study, the mesostructure of a fused deposition modeling (FDM) processed part is considered for the investigation of its mechanical behavior. The layers of FDM printed part behave as a unidirectional fiber reinforced laminae, which are treated as an orthotropic material. The finite element (FE) procedure to find elastic moduli of a layer of the FDM processed part is presented. The mesostructure of the part that would be obtained from the process is replicated in FE models in order to find stiffness matrix of a layer. Two distinctive architectures of mesostructure are considered in the study to predict the mechanical behavior of the parts. Also, influences of layer thickness, road shape and air gap on the elastic properties of a material are investigated. Further, the parts fabricated with FDM process are treated as laminate structures. From the numerical results, it is seen that the elastic moduli are governed by mesostructures. Our laminate results are validated with experimental to demonstrate the use of classical laminate theory (CLT) for FDM parts. The elastic moduli (E₁, E₂, G₁₂, ν₁₂) of a layer used in the analysis are calculated from FE simulations. This study establishes relationship between mesostructure and macro mechanical properties of the part. Full article

The need to manufacture a copy of a mechanical part typically arises when a single replacement part is necessary and is out of stock or out of production altogether. For parts with intricate details and associated accuracy requirements, investment casting may be preferred to machining, for size and detail reasons, or 3D printing, for material reasons. This work applies the digital manufacturing paradigm to one-off vacuum-aided rapid investment casting focusing on the process chain rather than on engineering issues. 3D laser scanning, digital model construction by surface fitting, casting model making by exploiting additive manufacturing, material investigation using scanning electron microscopy, casting simulation exploring process parameter scenarios, as well as the corresponding implementation on a vacuum casting machine are the pertinent interlinked steps and techniques. The added value of this work is that for each process link the important steps and the potential pitfalls are analyzed in detail using as an example a cylinder liner from a model car engine. Quality of the result was quite acceptable, the main benefit of the streamlined approach being that “right-first-time” parts can be achieved. Full article

Tube forming is a manufacturing process in which a circular tube is deformed into various shapes. This paper details a novel process in which tubular steel was formed into a square tube using a Reuleaux triangle tool. This triangular section tool translates on its section and rotates on its longitudinal axis to prepare a square geometry. It is hypothesized that the sliding action increases the formability of the part. After comparison with the square tool tube flaring, which only longitudinally translates to form a square tube, it is found that only 11% of the force is required to achieve the shape. Full article

Cloud Manufacturing (CM) is the concept of using manufacturing resources in a service-oriented way over the Internet. Recent developments in Additive Manufacturing (AM) are making it possible to utilise resources ad-hoc as replacements for traditional manufacturing resources in case of spontaneous problems in the established manufacturing processes. In order to be of use in these scenarios, the AM resources must adhere to a strict principle of transparency and service composition in adherence to the Cloud Computing (CC) paradigm. With this review, we provide an overview of CM, AM and relevant domains as well as presenting the historical development of scientific research in these fields, from 2002 to 2016. Part of this work is also a meta-review on the domain to further detail its development and structure. Full article

The main aim of this work was to evaluate the influence and optimize the factors of the TIG-MIG/MAG hybrid welding process on the geometry of the weld bead. An experimental design using the Taguchi methodology (robust design method) was used to conduct the experiments. The experiments were carried out according to an orthogonal matrix with 27 experiments, with three replicates each, totaling 81 test specimens. The factors (MIG/MAG shielding gas type, MIG/MAG voltage, MIG/MAG wire feed, gas flow rate of TIG, electric current intensity of TIG and welding speed) were varied with three levels each. Penetration, heat-affected zone (HAZ), bead width and bead height were the response variables analyzed. The results showed that the penetration was significantly influenced by the MIG/MAG wire feed, MIG/MAG shielding gas type, MIG/MAG voltage and welding speed. The HAZ has been influenced by MIG/MAG voltage, MIG/MAG shielding gas type, welding speed and electric current intensity of TIG. All factors had effects on the width, except the MIG/MAG wire feed. The bead height was significantly influenced by the MIG/MAG wire feed and by the electric current intensity of TIG. Optimizing the process was performed, so that for each output variable, the values of the factors that should be used were indicated, and the optimization was confirmed by welding test specimens. Full article

A major advantage of additive manufacturing (AM) technologies is the ability to print customized products, which makes these technologies well suited for the orthopedic implants industry. Another advantage is the design freedom provided by AM technologies to enhance the performance of orthopedic implants. This paper presents a state-of-the-art overview of the use of AM technologies to produce orthopedic implants from lattice structures and functionally graded materials. It discusses how both techniques can improve the implants’ performance significantly, from a mechanical and biological point of view. The characterization of lattice structures and the most recent finite element analysis models are explored. Additionally, recent case studies that use functionally graded materials in biomedical implants are surveyed. Finally, this paper reviews the challenges faced by these two applications and suggests future research directions required to improve their use in orthopedic implants. Full article

Punching processes are widely used for producing automobile parts, mechanical components, and other parts. To produce highly accurate parts, it is important to estimate the ratio of the sheared surface to the cut surface. Many researchers have applied the finite-element method (FEM) to analyze the ratio of the sheared surface to the fracture surface on cut surfaces by using ductile fracture criteria. However, it is difficult to determine the fracture criteria on the cut surface by tensile tests or bending tests because the punching process involves many complicated steps. In this study, FEM was applied to the punching process to determine the values of critical fracture criteria (C) by using the ductile fracture criteria proposed by Cockcroft and Latham, Oyane, and Ayada. The ductile fracture criteria were compared with the boundary between the shear surface and the fracture surfaces using experiments performed with a simple punching system. The values of the ductile fracture criteria for the fracture initiation of the formed cut surface were predicted under various clearances between the punch and the die with various punch diameters. The influence of stress triaxiality and the effect of punch diameter on the sheared surface length are also discussed. Full article