Conventionally manufactured cold work tool steel is often used in sheet metal forming as die material. Due to the forging process, the as-cast network structure of carbides is broken into elongated particles. Depending on the tool cross-section, the orientation and shape of carbides in the active tool surface is different. In the present research, the influence of tool steel hard phase orientation and shape on galling was investigated. D2 type tool steel was cut in three different orientations and tested in lubricated sliding conditions against AISI 304 austenitic stainless steel. Tests were performed using a Slider-On-Flat-Surface and galling was detected by changes in friction and post-test microscopy. The lubricant was Castrol FST8 using 5 g/m2 sheet material. Results showed a strong correlation between sliding distance to galling and tool steel hard phase orientation and shape at low loads, whereas high load contact resulted in early galling in all cases. Material transfer was observed mainly to the tool steel matrix. The worst performance was observed for specimens cut so that the tool steel hard phase, M7C3 carbides in the D2 steel, were oriented along the sliding direction, which resulted in longer open tool matrix areas contacting the sheet material.
EN 1.4301 (austenitic), EN 1.4509 (ferritic), EN 1.4162 (duplex) and EN 1.4310 C1000 (metastable austenitic) stainless steels were tested in lubricated sliding against an ingot cast EN X153WCrMoV12 and powder metallurgy nitrogen alloyed Uddeholm Vancron 40 tool steels to reveal critical to galling contact pressure, Pcr. The calculated Pcr were higher for steels with higher strength. At P>Pcr, due to plastic flow of sheet material, the tool is damaged substantially and wear-induced matrix damage causes rapid galling initiation. At P<Pcr, galling was not observed. The powder metallurgy tool steel was more resistant to galling against all tested stainless steels. Better performance was associated with fine and homogeneously distributed hard phases preventing intensive wear of the tool steel matrix.
By using the Additive Manufacturing (AM) method it is possible to manufacture components with thin-walled sections and complex geometry. However, it is not clear when the surface becomes the strength limiting factor on thin-walled sections in the components or if the thickness of the components is reduced. Also, the microstructure of AM produced specimens may be heterogeneous and it is not clear how the build direction influence the strength of thin section components. In the present study, the influence of component thickness, surface roughness and build direction on the strength of AM produced components were investigated. Test specimens were manufactured using EOS M290 3D-printer and EN 1.2709 maraging steel powder. To investigate when the part thickness, surface and built orientation becomes the strength limiting factors tensile testing using thin samples built in both horizontal and vertical build orientation with thicknesses ranging from 0.2 mm to 4 mm was performed. Results on strength limiting factors are discussed.
In this work, generative design optimization and characterization of triple periodic lattice structures in AlSi10Mg are considered. Structures with Gyroid, Schwarz-D and G-prime lattices are designed optimally by utilizing a generative design optimization approach. The approach is based on topology optimization, support vector machines (SVM), radial basis function networks (RBFN), morphing operations, design of experiments and metamodels. Firstly, topology optimization solutions are generated which are represented using SVM, secondly, sizing solutions obtained by setting the SIMP parameter equal to one are represented with RBFN. Thirdly, graded lattice structures using the RBFN are morphed together with the SVM to final conceptual designs. Fourthly, design of experiments of the conceptual designs are performed using non-linear finite element analyses (FEA) and, finally, metamodel-based design optimization is conducted using convex combinations of Kriging, RBFN, polynomial chaos expansion and support vector regression models. In order to validate the optimal designs, new tensile test specimens that include the periodic lattice structures are suggested. The specimens with all three lattices are manufactured in AlSi10Mg using direct metal laser sintering with an EOS M290 machine. Tensile tests of these specimens are then performed and validated using nonlinear FEA. The test specimens are also characterized with respect to geometry and defects by means of computed tomography, optical microscopy and scanning electron microscopy. The study demonstrates the high potential of using the proposed generative design optimization approach with triple periodic lattice structures for producing robust lightweight designs using additive manufacturing. In order to demonstrate the industrial relevance the established GE engine bracket is studied in the paper and discussed at the conference.
Omställningstiden i ytmonteringslinan Panasonic på Stoneridge Electronics AB ansågs vara en bidragande orsak till att maskinernas fulla kapacitet inte kunde utnyttjas. Syftet med det här examensarbetet var därför att analysera omställningssituationen och med analysen som grund reducera omställningstiden med hjälp av SMED-metoden samt ta fram förbättringsförslag gällande arbetet i övrigt.
Förutom SMED har tidsmätningar, observationer samt litteraturstudier legat till grund för reduceringen av omställningstid samt förbättringsförslagen som innebär bl.a. sekventiell omställning av conveyersystemet i ytmonteringslinan samt tydligare instruktioner och mer visuell styrning, enligt teorin om Lean.
Ett fortsatt arbete i form av uppdatering av arbetsinstruktioner och själva utförandet av omställningen är exempel på typen av ständiga förbättringar som företaget redan idag jobbar aktivt med.
Windows in a package is a common way to promote the product. The possibility to predict the collapse load for these types of cartonboard packages is considered. It is shown that reliable estimates of the collapse loads can be obtained by a very simple approach. This approach is a straightforward generalization of the proposal by Ristinmaa et al. (2012): for a side that contains a window, one simply removes the strip of the package side in the loading direction that contains the window. The calculation procedure is described in detail. As a test of the calculation procedure, comparisons are made with experimentally obtained collapse loads for packages containing windows with different sizes and locations.
Wire drawing is a manufacturing process in which metal rods or wires are drawn through a single or a series of dies, reducing the wire cross-section and enhancing the mechanical properties of the wire. The tribological conditions in wire drawing are quite extreme and high friction between the wire and the die results in an increased die temperature. Previous studies have shown that by reducing the die temperature the lifetime of the die increases and thus efficient cooling of the die is of high importance.
Additive manufacturing enables fabrication of tools with advanced conformal cooling channels with high cooling efficiency. This technique may, therefore, be of high importance in the design of the cooling system of drawing dies. In the present study, the effect of conformal cooling design of die holder on the die temperature, and thus die performance, was investigated. A die holder was manufactured by means of laser powder bed fusion (LPBF) in an EOS M290 machine using atomized corrosion resistant steel (Corrax). The cooling efficiency of the manufactured tool holder was evaluated in an industrial wire drawing process and further analysed using FEM modelling. This study shows promising results on improved cooling efficiency for die holder designed and manufactured by additive manufacturing.
During the past years, large efforts have been made at Volvo Cars to establish a scientific and systematic approach to selection of die materials, hardening methods and surface treatments/coatings. These efforts were initiated, since both new higher strength sheet materials and new die materials with better performance were introduced. Both these higher strength sheet materials and higher performance die materials needed to be industrialized.
Volvo cars transferred to a so-called Dry Presshop several years ago. This means that only the rust protection oil applied by the material supplier to the sheet prior to delivery is allowed as the stamping lubricant. No additional lubricant can be accepted. This transfer is done with regard to environmental improvement and a lean production philosophy. "Trouble-shooting" (reduction of abrasive and adhesive die wear) by using additional lubrication is therefore not possible anymore.
In this investigation 1.20 and 1.95 mm thick uncoated and hot-dip galvanized sheets of DP600, DP800 and DP1000 were tested. The wear behaviour of the die materials Sverker 21 (D2), Calmax, Sleipner, Weartec, Vanadis 6 and Vancron 40 were studied. Uncoated, plasma-nitrided, PVD-coated (CrN and TiAlN) versions of dies made in the above-mentioned materials were tested.
The tests were carried out both in laboratory in a U-bend test equipment and in real stamping production. Based on the results obtained in laboratory and production tests, guidelines were established for selection of die materials and surface treatments in stamping of DP600, DP800 and DP1000. These guidelines are described in the present paper.
The amount of residual lignin and hemicelluloses in softwood fibers was systematically varied by SO2-ethanol–water fractionation for integrated biorefinery with nanomaterial and biofuel production. On the basis of their low energy demand in mechanical processing, the fibers were deconstructed to lignocellulose nanofibrils (LCNF) and used as substrate for bioconversion. The effect of LCNF composition on saccharification via multicomponent enzymes was investigated at different loadings. LCNF digestibility was compared with the enzyme activity measured with a quartz crystal microbalance. LCNF hydrolysis rate gradually decreased with lignin and hemicellulose concentration, both of which limited enzyme accessibility. Enzyme inhibition resulted from non-productive binding of proteins onto lignin. Near complete LCNF hydrolysis was achieved, even at high lignin and hemicellulose content. Sugar yields for LCNF were higher than those for precursor SEW fibers, highlighting the benefits of high surface area in LCNF.
For certain materials science scenarios arising in rubber technology, one-dimensional moving boundary problems with kinetic boundary conditions are capable of unveiling the large-time behavior of the diffusants penetration front, giving a direct estimate on the service life of the material. Driven by our interest in estimating how a finite number of diffusant molecules penetrate through a dense rubber, we propose a random walk algorithm to approximate numerically both the concentration profile and the location of the sharp penetration front. The proposed scheme decouples the target evolution system in two steps: (i) the ordinary differential equation corresponding to the evaluation of the speed of the moving boundary is solved via an explicit Euler method, and (ii) the associated diffusion problem is solved by a random walk method. To verify the correctness of our random walk algorithm we compare the resulting approximations to computational results based on a suitable finite element approach with a controlled convergence rate. Our numerical results recover well penetration depth measurements of a controlled experiment designed specifically for this setting.
This paper describes the open Novamag database that has been developed for the design of novel Rare-Earth free/lean permanent magnets. Its main features as software technologies, friendly graphical user interface, advanced search mode, plotting tool and available data are explained in detail. Following the philosophy and standards of Materials Genome Initiative, it contains significant results of novel magnetic phases with high magnetocrystalline anisotropy obtained by three computational high-throughput screening approaches based on a crystal structure prediction method using an Adaptive Genetic Algorithm, tetragonally distortion of cubic phases and tuning known phases by doping. Additionally, it also includes theoretical and experimental data about fundamental magnetic material properties such as magnetic moments, magnetocrystalline anisotropy energy, exchange parameters, Curie temperature, domain wall width, exchange stiffness, coercivity and maximum energy product, that can be used in the study and design of new promising high-performance Rare-Earth free/lean permanent magnets. The results therein contained might provide some insights into the ongoing debate about the theoretical performance limits beyond Rare-Earth based magnets. Finally, some general strategies are discussed to design possible experimental routes for exploring most promising theoretical novel materials found in the database.
In light weight structures the joining of composite materials and of composites to metals are key technologies. A manufacturing method associated with joining is the drilling of holes. The hole creation in CRFP through drilling is associated with several defects related to the process, both on the entry and exit sides of the hole and also with dimensional and surface roughness issues of the hole wall. The detection of damage due to the process is not trivial. Especially interesting is non-destructive methods.
In this work X-ray computed tomography is used to determine defects due to drilling of holes in a CFRP composite using twist drills with different geometrical features at different drilling parameters. The results can be used to establish relationship between different geometrical features of drills in combination with cutting parameters and resulting surface integrity of holes.
A keen interest towards technological implications of spin-orbit driven magnetization dynamics requests a proper theoretical description, especially in the context of a microscopic framework, to be developed. Indeed, magnetization dynamics is so far approached within Landau-Lifshitz-Gilbert equation which characterizes torques on magnetization on purely phenomenological grounds. Particularly, spin-orbit coupling does not respect spin conservation, leading thus to angular momentum transfer to lattice and damping as a result. This mechanism is accounted by the Gilbert damping torque which describes relaxation of the magnetization to equilibrium. In this study we work out a microscopic Kubo-Streda formula for the components of the Gilbert damping tensor and apply the elaborated formalism to a two-dimensional Rashba ferromagnet in the weak disorder limit. We show that an exact analytical expression corresponding to the Gilbert damping parameter manifests linear dependence on the scattering rate and retains the constant value up to room temperature when no vibrational degrees of freedom are present in the system. We argue that the methodology developed in this paper can be safely applied to bilayers made of non- and ferromagnetic metals, e.g., CoPt.
The aim of this study was to employ an experimental protocol for in vivo evaluation of sols of 5 wt.% poly(ethylene glycol) (PEG) in phosphate-buffered saline as artificial vitreous substitutes. A 20 gauge pars plana vitrectomy and posterior vitreous detachment were performed in the right eye of eight pigmented rabbits. Approximately 1 ml of the viscoelastic PEG sols was then injected into the vitreous space of six eyes. PEG with an average molecular weight of 300,000 and 400,000 g mol(-1) was used in two and four eyes, respectively. Two eyes received balanced salt solution and served as controls. Full-field electroretinography was carried out and intra-ocular pressure (IOP, palpation) measured pre- and post-operatively at regular intervals up to 41 days. The rabbits were killed and the eyes examined by retinal photography, gross macroscopic examination and histology. The viscoelastic sols were successfully injected and remained translucent throughout the post-operative period, with some inferior formation of precipitates. None of the eyes displayed IOP elevation post-operatively, but in three of the PEG sol injected eyes transient hypotony was noted. One eye sustained retinal detachment during surgery and another two in the post-operative period. ERG recordings confirmed preservation of retinal function in three out of four eyes injected with 400,000 g mol(-1) PEG. Histological examination revealed up-regulation of glial acidic fibrillary protein in Müller cells in PEG sol injected eyes, but normal overall morphology in eyes with attached retinas. The viscosity of the sol was not retained throughout the post-operative period, indicating the demand for polymer cross-linking to increase residence time. The results provide promising preliminary results on the use of PEG hydrogels as a vitreous substitute.
Applications like geometric reverse engineering, robot vision and automatic inspection require sets of points to be measured from the surfaces of objects and then processed by segmentation and fitting algorithms to establish shape parameters of interest. In industrial applications where speed, reliability and automatic operation is of interest a measuring system based on a laser profile scanner mounted on an industrial robot can be of interest. In earlier publications we have presented such a system and also a segmentation algorithm for planar surfaces using 2D profile data in combination with robot poses. Due to the data reduction offered by this approach the segmentation algorithm computes faster than algorithms based on 3D point sets alone. Encouraged by the results we have now developed a segmentation algorithm for two different quadric surfaces also based on 2D profiles in combination with robot poses. This paper presents the new algorithm together with test results and also an interesting observation that points to future work.
Standards may be arrived at through various coordination mechanisms, including cooperation, coopetition, or competition. This article explores how technological uncertainty affects the coordination mechanism for standardization. The article is based on the Community Innovation Survey, a sizeable firm-level survey representative of the Luxembourgish economy. The econometric analysis finds evidence that firms facing technological uncertainty will choose for standardization through competition and coopetition.
Calculation of Box Compression Resistance (BCR) is a challenging task and here the possibility of an engineering approach is considered. The strive has been towards obtaining a simple and general predictive tool with as few parameters as possible and still obtaining an accurate estimate of the BCR. The model proposed is based on the concept of dividing the package into panels and corner panels. With these remarkably few structural elements it is possible to obtain simple explicit formulas where the only material parameters are given by standard tests in terms of short span compression test and bending resistance. The BCR for different packages is then obtained by a simply summation of the load from the panels and corner panels. A validation against experimental data indicates that, despite its remarkably simplicity, the predictions are very accurate for a wide range of package types, package dimensions, board qualities and loading directions.
Oxidation of Alloy 718 manufactured by electron beam melting (EBM) process has been undertaken in ambient air at 650, 700, and 800 degrees C for up to 168 h. At 800 degrees C, a continuous external chromia oxide enriched in (Cr, Ti, Mn, Ni) and an internal oxide that was branched structure of alumina formed, whereas at 650 and 700 degrees C, a continuous, thin and protective chromia layer was detected. The oxidation kinetics of the exposed EBM Alloy 718 followed the parabolic rate law with an effective activation energy of similar to 248 +/- 22 kJ/mol in good agreement with values in the literature for conventionally processed chromia-forming Ni-based superalloys. The oxide scale formed on the surface perpendicular to the build direction was slightly thicker, and more adherent compared to the scale formed on the surface along the build direction, attributed to the varied grain texture in the two directions of the EBM-manufactured specimens. The increased oxygen diffusion and high Cr depletion found on the surface along the build direction were attributed to the fine grains and formation of vacancies/voids along this grain orientation.
In this work, we present experimental and theoretical results on SmFe12-xVx (x = 0.5 - 2.0) alloys with the ThMn12 (1:12) structure as possible candidates for rare earth-lean permanent magnets. The compound with x = 2 has been previously reported to have a Curie temperature of 330 degrees C, saturation magnetization of about 80 Am-2/kg, and anisotropy field around 9 T. We have synthesized the SmFe11V compound with a nearly pure 1:12 phase; the x = 0.5 compound couldn't be synthesized. The relative stability of the x = 1, 2 compounds was addressed theoretically by enthalpy calculations from first principles. The newly synthesized SmFe11V compound has a Curie temperature of 361 degrees C and saturation magnetization of 115 Am-2/kg (1.12 T). The anisotropy field has been obtained in magnetically-oriented fine powders, and is around 11 T. These parameters make SmFe11V a good candidate for a new kind of high energy, rare earth-lean permanent magnets.
Originating from image recognition, methods of machine learning allow for effective feature extraction and dimensionality reduction in multidimensional datasets, thereby providing an extraordinary tool to deal with classical and quantum models in many-body physics. In this study, we employ a specific unsupervised machine learning technique-self-organizing maps-to create a low-dimensional representation of microscopic states, relevant for macroscopic phase identification and detecting phase transitions. We explore the properties of spin Hamiltonians of two archetype model systems: a two-dimensional Heisenberg ferromagnet and a three-dimensional crystal, Fe in the body-centered-cubic structure. The method of self-organizing maps, which is known to conserve connectivity of the initial dataset, is compared to the cumulant method theory and is shown to be as accurate while being computationally more efficient in determining a phase transition temperature. We argue that the method proposed here can be applied to explore a broad class of second-order phase-transition systems, not only magnetic systems but also, for example, order-disorder transitions in alloys.
The fourth Metal Additive Manufacturing Conference (MAMC 2019), organised by the Austrian Society for Metallurgy and Materials (ASMET), took place in Örebro, Sweden, from November 25–27, 2019. The event, which attracted an international audience, covered a broad range of metal AM technologies and considered the technical challenges that need to be overcome to make the industry more economically competitive with conventional manufacturing. Prof Dr Jürgen Stampfl, Prof Nader Asnafi, Dr Bruno Hribernik, and Dr Gerhard Hackl review the event for Metal AM magazine.
Selective laser melting (SLM) is frequently used additive manufacturing technique capable of producing various complex parts including thin-wall sections. However the surface roughness is a limiting factor in thin sections produced by SLM process when strength is the main criterion. In this study, the influence of build orientation, thickness and roughness on the resulting mechanical properties of as-built test samples was investigated. Various thin sheets of EN 1.2709 maraging steel built in horizontal and vertical orientations produced by SLM were investigated using in-situ micro-tensile testing in a scanning electron microscope. The mechanical strength and deformation mechanisms were analyzed and explained based on thickness and build orientation. Increased ductility was observed in thicker samples as well as in the horizontal build samples. The results illustrate the potential of the in-situ test technique and aspects important to consider in design guidelines for thin AM structures.
An essential property of magnetic devices is the relaxation rate in magnetic switching, which depends strongly on the damping in the magnetization dynamics. It was recently measured that damping depends on the magnetic texture and, consequently, is a nonlocal quantity. The damping enters the Landau-Lifshitz-Gilbert equation as the phenomenological Gilbert damping parameter a, which does not, in a straightforward formulation, account for nonlocality. Efforts were spent recently to obtain Gilbert damping from first principles for magnons of wave vector q. However, to the best of our knowledge, there is no report about real-space nonlocal Gilbert damping aij. Here, a torque-torque correlation model based on a tight-binding approach is applied to the bulk elemental itinerant magnets and it predicts significant off-site Gilbert damping contributions, which could be also negative. Supported by atomistic magnetization dynamics simulations, we reveal the importance of the nonlocal Gilbert damping in atomistic magnetization dynamics. This study gives a deeper understanding of the dynamics of the magnetic moments and dissipation processes in real magnetic materials. Ways of manipulating nonlocal damping are explored, either by temperature, materials doping, or strain.
In this study, the methods used to harden trim dies were at the focus. Laser surface-hardening was compared to induction- and through-hardening for small and medium-size series production. The sheet materials used were 1.2 mm thick uncoated Docol 600DP (DP600) and 1.95 mm thick uncoated Docol 600DL (DP600). The die materials tested were Fermo, Carmo and Sleipner.
This investigation showed that the optimum laser-hardening parameters must be established for each trim die material. The trim die in laser-hardened Sleipner exhibits the smallest wear. The dimensional changes after laser hardening are very small. The burr height is very small, regardless of how the trim die is hardened. In this study, two sets of production trim dies were manufactured and set up. This production trim dies are used in the manufacture of V70 B-pillar Left and Right. Laser hardening resulted in a lead time reduction by 5 labour days. However, the Tool & Die unit at Volvo Cars estimates that the lead time reduction obtained with laser hardening should be around 10 days under normal conditions. The cost analysis conducted by the Tool & Die unit at Volvo Cars shows that the manufacturing costs are reduced by 6%, if laser-hardening is selected. These production trim dies are and will be monitored continuously. As this paper is being written, these dies have been subject to 270,000 strokes without exhibiting any problems.
The electronic structure, magnetic properties, and phase formation of hexagonal ferromagnetic Fe3Sn-based alloys have been studied from first principles and by experiment. The pristine Fe3Sn compound is known to fulfill all the requirements for a good permanent magnet, except for the magnetocrystalline anisotropy energy (MAE). The latter is large, but planar, i.e., the easy magnetization axis is not along the hexagonal c direction, whereas a good permanent magnet requires the MAE to be uniaxial. Here we consider Fe3Sn0.75M0.25, where M = Si, P, Ga, Ge, As, Se, In, Sb, Te, Pb, and Bi, and show how different dopants affect the MAE and can alter it from planar to uniaxial. The stability of the doped Fe3Sn phases is elucidated theoretically via the calculations of their formation enthalpies. A micromagnetic model is developed to estimate the energy density product (BH)(max) and coercive field mu H-0(c) of a potential magnet made of Fe3Sn0.75M0.25, the most promising candidate from theoretical studies. The phase stability and magnetic properties of the Fe3Sn compound doped with Sb and Mn have been checked experimentally on the samples synthesised using the reactive crucible melting technique as well as by solid state reaction. The Fe3Sn-Sb compound is found to be stable when alloyed with Mn. It is shown that even small structural changes, such as a change of the c/a ratio or volume, that can be induced by, e.g., alloying with Mn, can influence anisotropy and reverse it from planar to uniaxial and back.
A high-throughput and data-mining search for rare-earth-free permanent magnets is reported for materials containing a 3d and p-element of the Periodic Table. Three of the most promising compounds, Fe 2 C, Mn2MoB4 , and Mn2WB4, were investigated in detail by ab initio electronic structure theory coupled to atomistic spin-dynamics. For these systems doping protocols were also investigated and, in particular, (Fe0.75X0.25)(2) C (X = Mn, Cr, V, and Ti), Mn2XB4 (X = Mo and W) along with Mn 2 (X0.5Y0.5)B-4 (X,Y = Mo, W, Ta, Cr) are suggested here as promising candidates for applications as permanent magnets. [GRAPHICS] IMPACT STATEMENT Several promising high-performance rare-earth-free permanent magnets have been found as a result of an ab initio high-throughput search. Alteration proposed to improve their stability and magnetic properties.