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In order to capitalize on the cost-effectiveness of additive manufacturing (AM), it is critical to understand how to build components with consistency and high quality. Directed energy deposition (DED) is an AM method for creating parts layer by layer through the use of a moving heat source and powder material inserted into the melt pool generated on the substrate. DED, like most AM processes, is highly complex due to the rapid thermal gradients experienced during processing. These thermal gradients are determined by a variety of processing parameters, which include laser power, powder feed rate, travel speed, layer height hatch spacing, etc. A lot of effort has been carried out in the additive manufacturing community to understand what these critical parameters are and how they influence the thermal gradients. Despite all these efforts, AM industries rely on a trial-and-error-based approach to find the right set of parameters to produce a quality part. This is time-consuming and not a cost-effective use of AM technology. The aim of our research is to reduce the amount of experimental data in combination with numerical analysis to optimize this relationship. Physics-based two-dimensional melt-pool modeling and experimental results from an OPTOMEC 850M LENS will be utilized to investigate the effects of processing parameters on melt-pool geometry, and the results from this study will provide key processing guidelines to achieve desirable clad geometry and powder efficiency for the DED method. [ABSTRACT FROM AUTHOR]

Rapid innovations in manufacturing process technology, information technology, and systems technology have led to simultaneous concerns about labor displacements and skills shortages. To address these concerns, the key challenges for educating and training the current and future workforce should be identified and the specific activities leading to the design of new manufacturing career pathways should be defined. Thus, the objective of this article is to define and prioritize the necessary activities and short- to long-term outcomes that will aid in developing high-skill career pathways that will positively impact children and families, students and teachers, and future workers. Expert perspectives from industry and academia have been analysed through two lenses: education (primary/secondary, technical, and university levels) and policy/innovation. The nominal group technique (NGT) is applied in this research to capture these perspectives, which enabled the generation of ideas followed by discussion and ranking by the experts. This approach encourages participation and avoids the associated drawbacks of typical group interactions. As a result, prioritized activities, short-term outcomes, and policy ideas to introduce children and families, students and teachers, and future workers to careers in advanced manufacturing are presented for each lens of focus. In addition, inputs from experts were captured to discuss desired medium- to long-term outcomes. In conclusion, this article summarizes the key findings from the study. [ABSTRACT FROM AUTHOR]

Inflammation and implant loosening are major concerns when using titanium implants for hard tissue engineering applications. Surface modification is one of the promising tools to enhance tissue-material integration in metallic implants. Here, we used anodization technique to modify the surface of commercially pure titanium (CP-Ti) and titanium alloy (Ti-6Al-4V) samples. Our results show that electrolyte composition, anodization time and voltage dictated the formation of well-organized nanotubes. Although electrolyte containing HF in water resulted in nanotube formation on Ti, the presence of NH4F and ethylene glycol was necessary for successful nanotube formation on Ti-6Al-4V. Upon examination of the interaction of bone marrow stromal cells (BMSCs) with the modified samples, we found that Ti-6Al-4V without nanotubes induced cell proliferation and cluster of differentiation 40 ligand (CD40L) expression which facilitates B-cell activation to promote early bone healing. However, the expression of glioma associated protein 2 (GLI2), which regulates CD40L, was reduced in Ti-6Al-4V and the presence of nanotubes further reduced its expression. The inflammatory cytokine interleukin-6 (IL-6) expression was reduced by nanotube presence on Ti. These results suggest that Ti-6Al-4V with nanotubes may be suitable implants because they have no effect on BMSC growth and inflammation. [ABSTRACT FROM AUTHOR]

Purpose The paper aims to highlight the importance of having an optical method that can accurately measure the surface finish of 3D printed parts and the influence this has on the total volume of the build.Design/methodology/approach The paper describes the application of digital moiré to the determination of the surface finish of 3D printed parts.Findings This study shows that surface roughness plays an important role in the volumetric analysis. There was an increase of 7 per cent from the total volume of the original CAD drawing; in total, there was 19 per cent more material deposited.Research limitations/implications This methodology provides a robust tool for future research in the area of geometrical verification and optimization in addition to the potential use for residual stress determination.Practical implications This study shows that process optimization can be carried out more efficiently, and it is possible to determine the efficiency of an AM process by directly correlating the processing parameters and accurately comparing the prescribed CAD dimensions/volume to that of the as built part.Social implications By reducing the amount of waste through process optimization, this leads to a reduced consumption of energy which can have a major impact on the environment.Originality/value This paper fulfills the need for high accuracy volumetric measurement of 3D printed components. [ABSTRACT FROM AUTHOR]

This article details the failure analysis of an aluminum bronze bushing that is utilized in a crimping machine. The crimping mechanism has an indenter (made of tool steel) that is guided by the aluminum bronze bushing that began to fail after 50,000 cycles or approximately 2 weeks of production operation. Typical run times prior to these failures were on the order of months. These failures were causing users to conduct excessive maintenance (i.e., swapping out aluminum bronze bushings). Initial concerns with quality of material were raised; however, after a detailed analysis of the entire system it was clear that there were several issues at play that were not previously considered. As a result this study focused on identifying appropriate materials and design changes of the indenter and bushing to reduce the wear and thus increase life. [ABSTRACT FROM AUTHOR]

Improvements in the properties of aluminum alloys have made them more popular for structural applications. Using the different heat treatments that are available, aluminum alloys can have a wide variation in properties for different types of applications. The appropriate heat treatments of these alloys are vital in providing the properties needed for their particular applications. Moreover, understanding the effects of heat treatments that may cause distortion to a part is critical. Most of the work carried out in this field is in the form of pre- and post-treatment analysis of a part. In this study, in-situ measurements of the distortions that a heat-treated part undergoes when subjected to rapid heating to temperatures near melting followed by slow cooling were carried out. A numerical model was built to simulate the experiment and the results are compared. This study will provide much-needed insight into the complex occurrences that aluminum parts undergo during heat treatment. [ABSTRACT FROM AUTHOR]

The general goal of the study is to connect theoretical predictions of continuum mechanics with actual experimental observations that support these predictions. The representative volume element (RVE) bridges the theoretical concept of continuum with the actual discontinuous structure of matter. This paper presents an experimental verification of the RVE concept. Foundations of continuum kinematics as well as mathematical functions relating displacement vectorial fields to the recording of these fields by a light sensor in the form of gray-level scalar fields are reviewed. The Eulerian derivative field tensors are related to the deformation of the continuum: the Euler–Almansi tensor is extracted, and its properties are discussed. The compatibility between the Euler–Almansi tensor and the Cauchy stress tensor is analyzed. In order to verify the concept of the RVE, a multiscale analysis of an Al–SiC composite material is carried out. Furthermore, it is proven that the Euler–Almansi strain tensor and the Cauchy stress tensor are conjugate in the Hill–Mandel sense by solving an identification problem of the constitutive model of urethane rubber. [ABSTRACT FROM AUTHOR]

Macroscopic behavior of materials depends on interactions of atoms and molecules at nanometer/sub-nanometer scale. Experimental mechanics (EM) can be used for assessing relationships between the macro world and the atomic realm. Theoretical models developed at nanometric and sub-nanometric scales may be verified using EM techniques with the final goal of deriving comprehensive but manageable models. Recently, the authors have carried out studies on EM determination of displacements and their derivatives at the macro and microscopic scales. Here, these techniques were applied to the analysis of high-resolution transmission electron microscopy patterns of a crystalline array containing dislocations. Utilizing atomic positions as carriers of information and comparing undeformed and deformed configurations of observed area, displacements and their derivatives, as well as stresses, have been obtained in the Eulerian description of deformed crystal. Two approaches are introduced. The first establishes an analogy between the basic crystalline structure and a 120° strain gage rosette. The other relies on the fact that, if displacement information along three directions is available, it is possible to reconstruct the displacement field; all necessary equations are provided in the paper. Remarkably, the validity of the Cauchy-Born conjecture is proven to be correct within the range of observed deformations. [ABSTRACT FROM AUTHOR]