Additive Manufacturing Research and Applications

This Special Issue book covers a wide scope in the research field of 3D-printing, including: the use of 3D printing in system design; AM with binding jetting; powder manufacturing technologies in 3D printing; fatigue performance of additively manufactured metals, such as the Ti-6Al-4V alloy; 3D-printing methods with metallic powder and a laser-based 3D printer; 3D-printed custom-made implants; laser-directed energy deposition (LDED) process of TiC-TMC coatings; Wire Arc Additive Manufacturing; cranial implant fabrication without supports in electron beam melting (EBM) additive manufacturing; the influence of material properties and characteristics in laser powder bed fusion; Design For Additive Manufacturing (DFAM); porosity evaluation of additively manufactured parts; fabrication of coatings by laser additive manufacturing; laser powder bed fusion additive manufacturing; plasma metal deposition (PMD); as-metal-arc (GMA) additive manufacturing process; and spreading process maps for powder-bed additive manufacturing derived from physics model-based machine learning

Characterization of Laser-Cladded AISI 420 Martensitic Stainless Steel for Additive Manufacturing Applications

Laser cladding is an additive manufacturing (AM) process that uses lasers to melt and deposit metallic powders in layer by layer to coat a substrate or to build three dimensional object. However, the AM industry encounters problems in handling residual stresses in the cladded parts or coating that lead to high hardness and distortion. Also, anisotropic properties developed in the laser-cladded AM parts are a challenge to use them as a functional component. This study aims to understand those problems with the laser-cladding AM process using AISI 420 martensitic stainless steel (MSS) powder in a coaxial direct powder deposition method. Primarily, this study focuses on the effect of process parameters, microstructural evolution, and associated residual stress development in the single bead of laser-cladded 420 MSS. Subsequently, the study was expanded to analyze the mechanical behavior of additive manufactured 3D samples using systematic approaches with X-ray diffraction, scanning and transmission electron microscopy (SEM/TEM), electron backscattered diffraction (EBSD) and MTS mechanical testing frame. This study revealed that laser speed has the most significant effect on the microhardness, while the powder feed rate has the most significant effect on the bead geometry. A detailed TEM study discovered various morphologies of martensitic phases that explained the reason behind the development of residual stress throughout the three zones, such as bead zone (BZ), dilution zone (DZ), and heat affected zone (HAZ) in a single bead clad. A high profile tensile residual stress (310–486 MPa) was observed in the upper BZ, while compressive stress (420–1000 MPa) was seen in the rest of the BZ and the DZ. This laser-cladded stainless steel vi showed a ~16% increase in yield strength (YS ~ 521 MPa), ~ 63% increase in tensile strength (TS ~ 1774 MPa), and a ~ 22% increase in ductility in terms of percentage of area reduction when compared with a similar 420 commercial grade MSS (YS - 483 MPa, TS - 1087 MPa), in the rolling direction with pre-hardened condition. The study showed that a post-cladding heat treatment at 565 °C for an hour reduced the tensile residual stress substantially in a single bead clad. A similar heat treatment also improved the fracture mode of 3D AM sample from brittle to ductile fracture and changed the anisotropic properties of the as-cladded sample in the transverse direction. This indicated that for design purposes, a simple post-cladding heat treatment (at 565 °C for an hour) is very important to minimize the anisotropy in the mechanical properties of as-cladded transverse sample. Also, it showed that a parts building technique with 30° angle to the base improved the ultimate tensile strength and partially eliminated the directionality issue. These findings could be important information for the designers with respect to “design for AM strategies.” It is expected that the above findings will be useful for the laser-based additive manufacturing application of AISI 420 martensitic stainless steel in designing functional components. However, the ratio of the yield strength vs. tensile strength of as-cladded AM sample needs to be improved to use this AM alloy in potential automotive applications

INTER-ENG 2020

These proceedings contain research papers that were accepted for presentation at the 14th International Conference Inter-Eng 2020 ,Interdisciplinarity in Engineering, which was held on 8–9 October 2020, in Târgu Mureș, Romania. It is a leading international professional and scientific forum for engineers and scientists to present research works, contributions, and recent developments, as well as current practices in engineering, which is falling into a tradition of important scientific events occurring at Faculty of Engineering and Information Technology in the George Emil Palade University of Medicine, Pharmacy Science, and Technology of Târgu Mures, Romania. The Inter-Eng conference started from the observation that in the 21st century, the era of high technology, without new approaches in research, we cannot speak of a harmonious society. The theme of the conference, proposing a new approach related to Industry 4.0, was the development of a new generation of smart factories based on the manufacturing and assembly process digitalization, related to advanced manufacturing technology, lean manufacturing, sustainable manufacturing, additive manufacturing, and manufacturing tools and equipment. The conference slogan was “Europe’s future is digital: a broad vision of the Industry 4.0 concept beyond direct manufacturing in the company”

Time Localization of Abrupt Changes in Cutting Process using Hilbert Huang Transform

Cutting process is extremely dynamical process influenced by different phenomena such as chip formation, dynamical responses and condition of machining system elements. Different phenomena in cutting zone have signatures in different frequency bands in signal acquired during process monitoring. The time localization of signal’s frequency content is very important. An emerging technique for simultaneous analysis of the signal in time and frequency domain that can be used for time localization of frequency is Hilbert Huang Transform (HHT). It is based on empirical mode decomposition (EMD) of the signal into intrinsic mode functions (IMFs) as simple oscillatory modes. IMFs obtained using EMD can be processed using Hilbert Transform and instantaneous frequency of the signal can be computed. This paper gives a methodology for time localization of cutting process stop during intermittent turning. Cutting process stop leads to abrupt changes in acquired signal correlated to certain frequency band. The frequency band related to abrupt changes is localized in time using HHT. The potentials and limitations of HHT application in machining process monitoring are shown

Enabling and Understanding Failure of Engineering Structures Using the Technique of Cohesive Elements

In this paper, we describe a cohesive zone model for the prediction of failure of engineering solids and/or structures. A damage evolution law is incorporated into a three-dimensional, exponential cohesive law to account for material degradation under the influence of cyclic loading. This cohesive zone model is implemented in the finite element software ABAQUS through a user defined subroutine. The irreversibility of the cohesive zone model is first verified and subsequently applied for studying cyclic crack growth in specimens experiencing different modes of fracture and/or failure. The crack growth behavior to include both crack initiation and crack propagation becomes a natural outcome of the numerical simulation. Numerical examples suggest that the irreversible cohesive zone model can serve as an efficient tool to predict fatigue crack growth. Key issues such as crack path deviation, convergence and mesh dependency are also discussed