Finite Element Modeling and Validation of Metal Deposition in Wire Arc Additive Manufacturing

Wire arc additive manufacturing allows the production of metallic parts by depositing beads of weld metal using arc-welding technologies. This low-cost additive manufacturing technology has the ability to manufacture large-scale parts at a high deposition rate. However, the quality of the obtained parts is greatly affected by the various thermal phenomena present during the manufacturing process. Numerical simulation remains an effective tool for studying such phenomena. In this work, a new finite element technique is proposed in order to model metal deposition in WAAM process. This technique allows to gradually construct the mesh representing the deposited regions along the deposition path. The heat source model proposed by Goldak is adapted and combined with the proposed metal deposition technique taking into account the energy distribution between filler material and the molten pool. The effectiveness of the proposed method is validated by series of experiments, of which an example is detailed in this paper.

Analysis of Warpage Induced by Thick Copper Metal on Semiconductor Device

Electrochemical deposited (ECD) thick film copper on silicon substrate is one of the most challenging technological brick for semiconductor industry representing a relevant improvement from the state of art because of its excellent electrical and thermal conductivity compared with traditional compound such as aluminum. The main technological factor that makes challenging the industrial implementation of thick copper layer is the severe wafer warpage induced by Cu annealing process, which negatively impacts the wafer manufacturability. The aim of presented work is the understanding of warpage variation during annealing process of ECD thick (~20 µm) copper layer. Warpage has been experimental characterized at different temperature by means of Phase-Shift Moiré principle, according to different annealing profiles. A linear Finite Element Model (FEM) has been developed to predict the geometrically stress-curvature relation, comparing results with analytical models.

Investigating Students’ Perception on the Outcomes of Technical Drawing University Courses

This paper presents the results of a survey carried out with students enrolled in the first two years of the BS in Engineering at three Italian university locations. The study is part of a wider range of methods, tools and aids for the improvement of teaching and learning of technical drawing at university level developed by the University of Brescia, Udine, and Cassino and Southern Lazio. In particular, this work analyses the results of questionnaires related to the basic technical drawing outcomes, taking inspiration from previous research work in this field. What emerges is a positive picture that shows students’ interest in 3D CAD modeling topics such as part or assembly construction, but also their interest in more traditional subjects like sketching and dimensioning.

Customization of Kayak Paddle Grips by Using Reverse Engineering, Computer Aided Design and Additive Manufacturing Tools

In this paper, due to the importance of maintaining a secure grip with the control hand in kayaking, a simple three phase process is presented for the massive development of personalized grips which allow the improvement of this handgrip. This process consists of obtaining the 3D geometry of the paddler's handgrip by using Reverse Engineering (RE) tools, designing the grip from the obtained 3D geometry by using Computer Aided Design (CAD) tools and manufacturing the grip by using Additive Manufacturing (AM) tools. Therefore, this paper shows that the RE, CAD and AM tools available today allow the customization of products for many applications.

Multicriteria Decision Making Methods in Engineering Design: An Application on Medical Devices

The design of medical devices is challenging, due to strict geometry specifications and criteria belonging to several disciplines. The aim of this paper is to provide a design methodology which seems to lack in the literature of design of biomedical devices. In particular, the case study proposed in this paper concerns with the design of Bone-Biopsy (BB) needle devices. Following the design process of Pahl and Beitz, a functional analysis is carried out, to point out the interfaces between parts of existing BB needles. A morphology matrix is used to generate alternatives for the cannula holder, the core part of the product. Generated alternatives have been ranked and scored by means of the Pugh’s Controlled Convergence method according to the decision makers' opinions. In this work, the design peculiarities related to the BB needles which have been pointed out could be extended for guiding the design of other biomedical devices.

Thread Couplings Stress Analysis by Radial Basis Functions Mesh Morphing

Traditional analytical methods are approximate and need to be validated when it comes to predict the tensional behavior of thread coupling. Numerical finite element simulations help engineers come up with the optimum design, although the latter depends on the constraints and load conditions of the thread couplings which are often variable during the system functioning. The present work illustrates a new method based on Radial Basis Functions Mesh Morphing formulation to optimize the stress concentration in thread couplings which is subject to variable loads and constraints. In particular, thread root and fillet under-head drawings for metric ISO thread, which are the most commonly used thread connection, are optimized with Radial Basis Functions Mesh Morphing. In metric ISO threaded connection, the root shape and the fillet under the head are circular, and from shape optimization for minimum stress concentration it is well known that the circular shape becomes seldom optimal. The study is carried out to enhance the stress concentration factor with a simple geometric parameterization using two design variables. Radial Basis Functions Mesh Morphing formulation, performed with a simple geometric parameterization, has allowed to obtain a stress reduction of up to 12%; some similarities are found in the optimized designs leading to the proposal of a new standard. The reductions in the stress are achieved by rather simple changes made to the cutting tool.

Generation of Entrepreneurship Environments for New Product Development

The economic environment demands companies to be able of innovating and presenting new products and technologies. However, current industrial environments are composed of big established companies, small or medium family businesses and regional clusters. This business map does not comply with the dynamism required for detecting needs and proposals in form of new products that meet the current customer requirements. The creation of start-ups in the field of engineering is considered as a possibility to cover a growing market in designing high technological products. However, despite the importance and economic impact of the start-ups for less industrialized environments the courses in the engineering field do not include activities that contextualize theoretical knowledge and entrepreneurship. The paper presents the results of creating an entrepreneurial environment focused on the student as entrepreneurial unit. In this context, a series of new activities based on new design proposals have been developed on the basis of new technical solutions for industrial companies. The new designs have been presented as minimum viable products. The technical knowledge required for making the new designs has been complemented with entrepreneurial training. The results show an increase in students' willingness to create small companies based in new products as an employment option at the end of their studies.

Cold Working Process on Hard Metal Stacked Assembly

Designed for aeronautical and automotive applications, the split sleeve cold expansion process is used to improve the fatigue life of bolted metallic parts. Although its application has been well tested on aluminum assemblies, hard metal applications are still being studied. This paper presents experimental results of double bolt joint assemblies under double shear fatigue tests after stacked split sleeve cold expansion. The behaviors of two sizes of assemblies with different degrees of expansion are investigated. S-N curves are the main indicators of this study but thermal aspects are also investigated to observe fretting in the specimens as bolts are preloaded. Bolt tension is a major parameter in assembly regarding fatigue life. Interference between those two phenomena is at the heart of this paper. The first results show that stacked cold expansion has a negative effect on mechanical performances, as it deteriorates the fatigue life of the assembly. However, an examination of these results provides a coherent explanation for the loss of performance that occurs.

Comfort Driven Redesign: The Case of Library Chairs

University students spend most of their time in a sitting position. Prolonged sitting on ill-fitted furniture and the resulting lousy posture is making students having different musculoskeletal disorders and is strictly related to students learning outcomes. This study aims to improve postural comfort of chairs placed inside the Science & Technology Library at the University of Salerno. A previous study about these library chairs showed that the lumbar area was the most suffering part while perceived (dis)comfort was dependent on time. Based on this, an ergonomic redesign and, consequently, manufacturing of the chair has been done. A perceived-comfort comparison between the library chair and the redesigned one has been performed. A statistical sample of 28 healthy students performed a 20-min experiment two times, alternatively on the library chair and the redesigned one. The 20-min experiment was divided into two 10-min tasks (“Reading & Writing” and “Laptop use”) to simulate a study day. The participants’ postures were acquired non-invasively using cameras and processed by Kinovea; questionnaires were used to rate the perceived subjective (dis)comfort. A procedure for improving an existing product through a comfort-driven redesign is proposed. Results showed the redesigned library chair lead on increasing postural comfort (particularly in the lumbar area) thanks to the new design and modifications.

Causality Learning Approach for Supervision in the Context of Industry 4.0

In order to have a full control on their processes, companies need to ensure real time monitoring and supervision using Key Performance Indicators (KPI). KPIs serve as a powerful tool to inform about the process flow status and objectives’ achievement. Although, experts are consulted to analyze, interpret, and explain KPIs’ values in order to extensively identify all influencing factors; this does not seem completely guaranteed if they only rely on their experience. In this paper, the authors propose a generic causality learning approach for monitoring and supervision. A causality analysis of KPIs’ values is hence presented, in addition to a prioritization of their influencing factors in order to provide a decision support. A KPI prediction is also suggested so that actions can be anticipated.