1,720,974 research outputs found
Modelling and fatigue assessment of steel rollers with failure occurring at the weld root based on the local strain energy
No full textAbstractWeldments geometry with failures occurring at the weld toe or at the weld root cannot, by its nature, be precisely defined. Parameters such as bead shape and toe or root radius vary from joint to joint even in well-controlled manufacturing operations. The worst case configuration can be achieved by modelling as a sharp, zero radius, notch both the toe and the weld root. The intensity of asymptotic stress distributions obeying Williams’ solution are quantified by means of the Notch Stress Intensity Factors (NSIFs). For steel welded joints with failures originated from the weld roots, where the lack of penetration zone is treated as a crack-like notch, units for NSIFs are the same as conventional SIF used in LEFM. The different dimensionality of NSIFs for different notch opening angles does not allow a direct comparison of failures occurring at the weld toe or at the weld root. In order to overcome the problem related to the variability of the V-notch opening angle, a simple scalar quantity, i.e. the value of the strain energy density averaged in the structural volume surrounding the notch tip, has been introduced. This energy is given in closed form on the basis of the relevant NSIFs for modes I, II and III. The radius RC of the averaging zone is carefully identified with reference to conventional arc welding processes being equal to 0.28 mm for welded joints made of steel.The local-energy based criterion is applied here to steel welded rollers produced by Rulmeca subjected to prevailing mode I (with failures at the weld root). The aim of the paper is firstly to describe the employed methodology for the fatigue assessment and secondly to show the first synthesis of fatigue data by means of local SED for a specific geometry
On the fatigue properties of a third generation aluminium-steel butt weld made by Hybrid Metal Extrusion & Bonding (HYB)
No full textThe present investigation is concerned with the high-cycle axial fatigue behaviour of a third generation Al-steel butt weld made by Hybrid Metal Extrusion & Bonding (HYB). In this particular weld, metallurgical bonding is achieved by a combination of microscale mechanical interlocking and intermetallic compound (IMC) formation, where the IMC layer is in the sub-micrometre range (<1μm). During high-cycle axial fatigue testing this microstructure provides a high intrinsic resistance against interfacial cracking. In the as-welded condition, fatigue fracture typically initiates at the weld toe on the aluminium side of the joint due to the unfavourable effect of having a geometrical stress riser localised inside the soft heat-affected zone. Since the interfacial bond strength is not a limiting factor, the fatigue properties of the Al-steel HYB butt weld are seen to fully match those of corresponding Al-Al weldments produced by gas metal arc welding, laser beam welding and friction stir welding. © 2021 Elsevier Lt
Investigating Maturity of Lean Culture in Product Development Teams
No full textNowadays, many companies attempt to expand the lean concept from manufacturing to Product Development (PD). However, there are very few practical examples reporting how lean can be successfully applied outside the manufacturing floor. The benefits of lean can only be realized in PD once the concept is scaled to the business environment where it is employed. In this paper, we use a maturity framework for identifying gaps between current lean culture capabilities and those deemed necessary for competitive PD practices in the future. The general objective is to identify differences between companies as to how they assess capability gaps relating to lean within their operational context. A lean assessment framework using a continuous descriptive five-level maturity grid method has been used in the PD environments of nine companies. Focus has been placed on assessing characteristics associated with a lean culture in PD. The results show significant differences between the companies as to how they assess the gap between their current lean cultural capabilities and those deemed necessary in the future. Overall, the use of simple and visual communication means in PD activities is identified to provide the larger capability gap among the companies studied. In the other end of the scale, showing the smaller gap, we identified the perceived role of digital tools and technology in PD
Different approaches for fatigue assessment of butt-welded joints
No full textThe main aim of this work is the fatigue strength assessment of butt joints with weld reinforcement, typically used in steel works and especially in shipbuilding applications. A sensitivity analysis has been carried out by varying different geometrical parameters of the welded joints. Moreover, two different approaches for fatigue strength estimates were applied, namely the Effective Notch Stress Approach, which is nowadays widely used and it is supported by comprehensive literature and the Strain Energy Density approach. Analyses were carried out using two different finite element codes: Ansys® and Adina®. The application of different software allowed verifying the quality of obtained results, disclosing certain essential aspects related to the extrapolation of values from integration points of finite elements
Analytical modelling of residual stress in additive manufacturing
No full textA physics-based analytical model to assess residual stresses in additive manufacturing made of metallic materials is presented and validated experimentally. The model takes into consideration the typical multi-pass aspect of additive manufacturing. First, the thermal signature of the process is assessed by predicting the temperature for the problem of a moving heat source, then, the thermally induced stresses in a homogenous semi-infinite medium are determined. Taking the thermal stresses as input, the residual stresses are calculated analytically to obtain the distribution across the depth. Good agreement is obtained between the analytical prediction and X-ray measurements made on Selective Laser Melted 316L Stainless Steel. In addition, the analytical approach enables in-depth interpretations of results with basis in the true mechanisms of the process. Thus, the present model appears as a promising tool for optimization of process parameters in additive manufacturing, which in turn will improve the understanding of process parameters and their effect on properties of the final product. © 2016 Wiley Publishing Ltd
Formation of fully equiaxed grain microstructure in additively manufactured AlCoCrFeNiTi0.5 high entropy alloy
No full textIn this work, the non-equiatomic high entropy alloy AlCoCrFeNiTi0.5 was additively manufactured via the laser engineered net shaping (LENSTM) process. Contrary to the columnar grain microstructure commonly observed in previously reported alloys, the as-deposited AlCoCrFeNiTi0.5 specimens exhibit a fully equiaxed grain microstructure in a wide range of temperature gradients G (85 to 1005 K/mm) and solidification velocities V (5 to 20 mm/s). The main microstructural characteristics were found to be B2-structured proeutectic dendrites delineated by lamellar or rod-like B2/A2 eutectic structures. The formation of this microstructural feature can be discussed with the aid of Scheil's solidification model. The proeutectic B2-structured dendrites were frequently found to be fragmented, which may provide profuse effective nucleation sites, and hence promote equiaxed grain formation. Furthermore, we estimated the volume fraction φ values of equiaxed crystals at solidification front for various G - V combinations established in this paper, which can provide a theoretical basis for our experimental findings. The current work provides guidelines for producing fully equiaxed alloys by the additive manufacturing (AM) process
Additive manufacturing of fine-grained and dislocation-populated CrMnFeCoNi high entropy alloy by laser engineered net shaping
No full textThe equiatomic CrMnFeCoNi high entropy alloy is additively manufactured by the laser engineered net shaping (LENSTM) process, and the solidification conditions, phase formation, as-deposited microstructures, and tensile behavior are investigated. The LENSTM-deposited CrMnFeCoNi alloy exhibits a single-phase disordered face centered cubic (FCC) structure, as evidenced by X-ray diffraction (XRD), and rationalized by Scheil's solidification simulation. Furthermore, microstructures at multiple length scales, i.e. columnar grains, solidification substructures, and dislocation substructures, are formed. The tensile deformation process is mainly accommodated by dislocation activities with the assistance of deformation twinning. The tensile yield strength of the LENSTM-deposited CrMnFeCoNi alloy is comparable to that of finer-grained wrought-annealed counterparts, due to the additional initial-dislocation strengthening. However, the uniform tensile elongation, by contrast, is lowered, which is attributed to the increased dynamic dislocation recovery rate and hence the weakened work hardening capability of the LENSTM-deposited CrMnFeCoNi. This study demonstrates the capability of the LENSTM process for manufacturing the CrMnFeCoNi alloy, with high performance, for engineering applications. © 2019 Elsevier B.V
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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