1,721,033 research outputs found
A Review of FEM Codes Accuracy for Reliable Extrusion Process Analysis: ICEB Extrusion Benchmark Conference
No full textThe paper presents an overview on the 2015 and 2017 editions of the ICEB
benchmark conferences, with a focus on experimental trials results and on the comparison of the accuracy of the different finite element method (FEM) codes in predicting critical process outputs. Indeed, benchmark experiments are designed with the aim to focus the attention on a particular phenomenon and to check the ability of FEM codes for its prediction. Profile lengths, process load, die deflections, die and profile temperatures were accurately recorded during the extrusion trials (conducted in laboratory or industrial environment) and were used as benchmarking parameters for FEM comparison. On the profiles, locations of seam and charge
welds and grain size distribution were metallurgically analyzed and required as benchmarking parameters as well. Moreover, computational times, simulation set-up times, as well as information on the required hardware were compared for the proposed case studies. A detailed discussion of all the output parameters is realized, in order to illustrate the evolution of the potentialities, and limits, of each code in the recent year
An Empirical Statistical Model for Laser Cladding of Aluminium Bronze on S235JR Pipe
No full textCoaxial laser cladding of aluminium bronze on S235JR pipe is experimentally investigated in order to create an empirical statistical model. Crack-free coating of aluminium bronze was achieved without the use of intermediate layers. The microhardness HV0.3 was also found to be greater than typical for the same material. The effect of processing parameters (laser power, scan speed, hatch distance) on the geometrical characteristics of coating (consisting of three clad tracks) has been analysed and predicted in response to geometrical features (height, width, dilution, and density) by employing regression analysis. The validity of statistical models was confirmed with the correlation coefficient and analysis of residuals. For each studied geometrical characteristic, a correlation has been established that contains a combined parameter. These correlations can be utilised for selecting suitable processing parameters for the coating of aluminium bronze
Fabrication of Thin Walls with and without Close Loop Control as a Function of Scan Strategy Via Direct Energy Deposition
Full text linkDirect Energy Deposition (DED) is a technique used to fabricate metallic parts and is a subcategory of metal additive manufacturing. Despite of its vast advantages over traditional manufacturing the deployment at industrial level is still limited due to underlaying concerns of process stability and repeatability. In-situ monitor- ing, therefore, is indispensable while depositing via DED. The present experiment is a step towards enhancing our current understanding of the DED when coupled with a closed loop control system to control melt pool width for deposition of thin- walled structures, and as a function of scan strategy. 316L stainless steel powder was deposited on S235JR substrate. A total of 6 iterations are reported, out of many performed, of which 3 were without the closed loop control. Also, to understand the effect of scan strategy as a function of laser power. Two different scan strategies were employed for understanding of the issue i.e., unidirectional, and bidirectional. Apart from the geometrical consistency of the wall, microhardness, density calcula- tions and microstructure were investigated. The geometric consistency was found to be almost perfect with the bidirectional scan strategy. In case of unidirectional scan strategy, the wall shows a negative slope along the other extreme regardless of the closed loop control system. Dilution zone shows the hardness greater than both the substrate and the wall. The specimens fabricated without the use of closed loop con- trol were found to be denser than their counterparts. This was found to be true also in case of manual reduction of power during each layer
Modeling of Nitrogen Cooling in the Extrusion of Aluminum Alloys
No full textThe extrusion process with liquid nitrogen cooled dies is widely adopted in
industrial practice. Cooling channels are usually realized on the backer face in contact with the die and their design is mainly based on die maker experience. However, many parameters can be included in a die optimization, such as the number and the position of inlets/outlets, as well as the nitrogen channel position, shape, and dimensions. Trial-and-error approach is time and cost consuming, thus suggesting a great interest in numerical simulations to be carried out at the die
design stage. In the present work, a model for the simulation of the nitrogen-cooled extrusion process is innovatively presented and validated. A simplified 1D model of the channel is integrated in a 3D Finite Element (FE) simulation of the extrusion process by means of COMSOL code. Two experimental campaigns specifically carried out to monitor the efficiency of nitrogen cooling in industrial plants have been simulated and results compared in terms of die and profile temperatures, as well as in terms of extrusion load, in cooled and uncooled conditions
Comparing Hot-Work Tool Steels for Extrusion Die Performance
No full textHot-work tool steels are usually the selected materials for high-load and high-
temperature applications such as forging, casting and extrusion dies. In this framework, each cast/forged part or each extruded billet represents for the tool a mechanical load cycle, thus leading to the fatigue-working regime. In addition, the high thermal loads are also involved for the creep phenomenon that synergistically and detrimentally act with fatigue, reducing the tool lifetime. In the present work, three hot-work tool steels commonly used to manufacture extrusion dies have
been selected and compared in terms of dynamic performance under the creep-fatigue regime. An innovative experimental setup was used to test the steels by means of specimens that replicate the mandrel of a porthole die on a small scale. The H11 and the H13 have been compared at different levels of temperature and load by evaluating the specimen deflection over time, clearly highlighting the relative optimal working windows. An analytical model developed by the authors was also used to predict the H11 specimen lifetime at further load/temperature levels in order to perform a comparison with previous performed experiments on the super clean hot-work tool steel TQ1
ICEB2017-Benchmark Settings
No full textAim of the benchmark at ICEB conference is to examine FEM codes capabilities and users’ knowledge in
the simulation of extrusion trials which were carried out and monitored by conference organizers. The comparison of the
“blind” simulations by the participants with the experimental results allows users to check if their simulation settings are
generally adequate to replicate the problem and software house to verify the sensitivity of their solving methods. It is very
important for us to remind that, due to the complexity of this matter, it would be useless to consider the benchmark as a
contest: it is, instead, an opportunity to fix some points about the everyday simulation practice, each participant with his
own particular interest. In this direction no winner will be awarded at the end of the conference because a clear
comparison of code’s capabilities will visibly emerge.
.Also for the 2017 edition, at the end of the benchmark session, a comparison of all codes outputs
with experimental results will be performed by the conference organizers. During such presentation
the results of all the participants will be compared over experimental trials on the basis of results
submitted at beginning June2017.
EVOLUTION OF THE CHARGE WELDS: TOWARDS A NOVEL ANALYTICAL FORMULATION
No full textCharge welds are, together with the seam welds, defects generated during the
continuous extrusion of metallic materials. However, while the seam welds can
exhibit the same resistance of the basic material if proper levels of pressure, contact time and temperature
are applied, charge welds are always contained parts of the profile with lower mechanical
properties. Indeed, at the end of each process stroke, the back end of the old billet material
that completely fill the die starts to interact with the front side of the new billet loaded into the
press that is usually contaminated by oxides, dust or lubricant thus producing a transition zone
that extends to a variable length. It comes then clear that the length of the profile marked by
the charge welds need to be scrapped and an accurate prediction and reduction of this portion
become mandatory, not only for the final user of the profile, in order to avoid in-service
product failures, but also for extruders and die makers to increase process efficiency.
In this context, aim of the present work was to compare the experimental -numerical investigations
performed by the authors in terms of charge welds extensions with the predictions of
the analytical models nowadays reported in literature. The final global aim work was
to assess the applicability of these models in the everyday industrial practice
QUALITY ASSESSMENT AND OPTIMIZATION OF AN INDUSTRIAL EXTRUDED PROFILE
No full textThe extrusion process is an economic maunfacturing method used to produce profiles with a constant section. However, even when simple components are considered, many process and product issues can emerge such as low mechanical properties or distorsions of the exit profile, die premature failure and/or low production rates. These problems are related to the complex nature of the process that has to guarantee, at the same time, proper conditions for a good welding (in case of hollow profiles), absence of profile distorsions, an acceptable die stress and as much as possible fast extrusion. In addition, all these conditions have to be reached in the short extrusion time of each single billet and can emerge to be conflicting one each other’s. Usually, the optimization of the extrusion process is performed
by the operators on the basis of consolidated experience and empirical rules. However, in this way, it is extremely difficult to control all the process and geometrical parameters involved and then to control the final outputs. This explains the number of works in literature aimed to develop numerical and analytical models for the extrusion process optimization. In this context, the authors recently presented a novel procedure for the multi-goal optimization of extrusion dies based on meta-models that was preliminary validated on the experimental results available for a simple round tube profile. In this work, two additional test cases are presented with the aim to extended the validation cases of the proposed procedure to a more complex industrial profil
Grain evolution analysis and experimental validation in the extrusion of 6XXX alloys by use of a lagrangian FE code
No full textThe grain size and shape evolution of 6XXX aluminum alloys during hot metal forming processes are investigated by experimental observations and numerical analysis. A unified model is developed to simulate the grain evolution during deformation and subsequent static recrystallization. First, an experimental set reproducing a small scale direct extrusion was realized in order to identify the grain deformation modes and the empirical equations that model the evolution. The equations were then linked with modified formulations of static recrystallization available in literature and then implemented in the lagrangian FE code Deform through user-routines. The developed model innovatively computes all the phases of the phenomena by considering not only the static recrystallization but also the previous deformation phase. Effects of geometric dynamic recrystallization, influence of subgrain size, the dislocation densities distribution and the stored energy on subsequent grain static recrystallization were considered. Then, a reduced scale backward extrusion experiment was performed at different Zener-Hollomon levels, in order to check the model after deformation and after a fully static recrystallization. The model properly predicts both the deformed state of the grains (immediate quenching) and the fully recrystallized state but still miss to predict abnormal grain growth
Advanced modeling of die cooling with liquid nitrogen
No full textThe profile temperature monitoring during aluminum extrusion is a an important information performed in order to avoid profile defects such as burn and crack, or an incorrect tempering, or to preserve the die life and to increase the process productivity. In the last decade die cooling systems through liquid nitrogen have been installed on several extrusion plants. However, a comprehensive and systematic assessment of the liquid nitrogen die cooling effect on process parameters is still missing in literature. In this context, aim of the present work is to develop an advanced numerical finite element model of the extrusion that accounts for liquid nitrogen cooling. The numerical model is then validated over ICEB 2011 Industrial Benchmark experimental trials, where the cooling efficiency in a multi-hollow industrial profile was evaluated. The results of the simulations have been compared to experimental investigation both in cooled and uncooled conditions. The assessment showed a good experimental-numerical agreement in terms of temperature map and extrusion load, thus suggesting the reliability of the novel modelling to support the process optimization
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