1,721,008 research outputs found
The extrusion process towards Industry 4.0:a multi-objective simulation approach
Full text linkThe extrusion of aluminum alloys is a prcess able to manufacture high tolerances and high mechanical properties profiles. However, the main drawback of the process is that many objective functions need to be satisfied at the same time and many of these are potentially conflicting one each other. Example of conflicting objective functions are thre requirement fro high seam welds quality (in hollow profiles), an extended die lifetime and an high productivity. In order to solve the problem, the authors developed a comprehesive mutli-objective optimization of the extrusion process base on meta-models. The proposed procedure has been validated against two industrial profiles of a different complexity and a thrid case in now under investigation. Preliminary experimental analyses of the third case are presented
Mechanical performance of hybrid metal-composite joints reinforced with additive-manufactured stainless steel pins: a comparative study of pin geometry and fabric architecture
No full textThe design of robust hybrid joints between metal and composite parts is critical in multi-material structural applications. This study investigates the mechanical performance of single-lap joints reinforced with additively manufactured stainless steel pins featuring two geometries—spike (Type S) and ball-head (Type B)—embedded in unidirectional (UD) and twill (TW) carbon fiber-reinforced polymer (CFRP) laminates. Under quasi-static shear loading, ball-head pins increased peak load by up to 44% and failure energy by up to 66% compared to spike pins, with the Type B TW configuration achieving the highest energy dissipation. Microscopy revealed that fiber architecture and pin geometry jointly influenced failure mechanisms: TW laminates promoted distributed damage and bridging, while UD laminates exhibited localized fiber fracture and matrix splitting. These findings demonstrate that additive pinning strategies can be tailored to enhance strength and toughness in hybrid joints, and provide insight for the future design of durable metal–composite interfaces in aerospace and automotive applications
Enhancing the Robustness of Hybrid Metal-Composite Connections Through 3D Printed Micro Penetrative Anchors
Full text linkThis work proposes a novel solution for manufacturing hybrid metal-composite joints, in which different pin shapes are evaluated for their capability to penetrate long carbon fiber epoxy composites successfully and for the mechanical behavior determined by each configuration. On the metal side, pins are manufactured by Laser Powder Bed Fusion (LPBF), downsizing the currently adopted solutions and, at the same time, developing new blocking features aimed at enhancing the mechanical properties of the joint. The different configurations were evaluated in two distinct experiments: the first to evaluate the induced defects in the composite substrate and the second to characterize the mechanical behavior of the joint. It emerges that smaller pins produce much less damage and misalignments in the composite structure with respect to the conventional pin solution, whereas the new “blocking features” configurations consistently increase maximum pullout load and energy with respect to the conventional pin solution, with the same level of fiber damage
Prediction of melt geometry in laser cutting
No full textIn this paper, an analytical model for the evaluation of the melt film geometry in laser cutting of steels is developed. Using as basis, a previous model for kerf geometry estimation developed by the authors, with both reactive and non-reactive process gases, the film thickness and velocity were determined as a function of the kerf depth in the cutting plate. Two criteria were then adopted to predict the quality of the laser cutting operation: the first is based on a minimum acceptable value of the ejection speed of the melt from the bottom of the kerf, the second on the occlusion of the kerf itself due to an excess of molten material in the boundary layer at the kerf width. These criteria determined a feasibility region in the domain of the process and material variables, such as cutting speed, assistant gas pressure, laser beam power and material characteristics. These factors may be successfully used to build a process-planning tool for parameters optimisation and setting, in order to achieve a satisfactory process quality. The model response is in excellent agreement with the feasibility regions reported from experimental data by various authors and demonstrates a relationship between the occurrence of dross adhesion and the two different mechanisms predicted for such a phenomenon were: unsatisfactory ejection speed of the melt film from the bottom of the kerf and occlusion of the kerf. © 2002 Elsevier Science B.V. All rights reserved
Predicting buckling resistance of two three-dimensional lattice architectures
Full text linkLattice structures are an important class of architected cellular solids and structures with high potential for multifunctional and lightweight applications. Novel technologies such as additive manufacturing have vastly extended the design freedom to develop such architectures. In this work, a reliable theoretical model for optimizing unit cell design against buckling is developed for two different cell architectures: pyramidal and tetrahedral. The model's accuracy was evaluated through extensive finite element analysis and compared to existing methods available in the literature
Prediction of mechanical properties in spheroidal cast iron by neural networks
No full textAn artificial neural network-based system is proposed to predict mechanical properties in spheroidal cast iron. Several castings of various compositions and modules were produced, starting from different inoculation temperatures and with different cooling times. The mechanical properties were then evaluated by means of tension tests. Process parameters and mechanical properties were then used as a training set for an artificial neural network. Different neural structures were tested, from the simple perceptron up to the multilayer perceptron with two hidden layers, and evaluated by means of a validation set. The results have shown excellent predictive capability of the neural networks as regards maximum tensile strength, when the variation range of strength does not exceed 100 MPa
Rapid EDM electrodes manufacturing by metallization of rapid Prototypes.
No full textThe development of Rapid Prototyping techniques opens new perspectives for Rapid
Tooling. The combination of RP and Metal Spraying has been already proofed to be
successful in producing directly moulds for low melting point materials. The attempt to
move this technique to the production of steel dies has generally failed.
A research aimed to the investigation of indirect rapid tooling techniques has been started.
The purpose is to obtain an EDM electrode from a prototype and then using it to
manufacture the steel die by EDM. Rapid Prototyping process considered in the
investigation is Laminated Object Manufacture (LOM).
In first attempt a metallic coating has been applied to the prototype by thermal spraying. In
this case the distortion of the prototype can be minimised and delamination can be
eliminated by a proper choice of growing direction of the LOM prototype combined with a
proper set-up of spraying process including inclination of nozzle, thickness of the layers
and cooling. Considering the geometry of the coated prototype this method led to
unsatisfactory results. The main reasons is the fact that thickness of the coating can not be
controlled and, therefore the resulting geometry of the electrode is different from the initial
geometry.
An alternative technique has been proposed which in principle can produce a sound
electrode combining metal spraying with metal casting. In this approach the LOM object is
a copy of the die instead of the manufactured part. A first layer of metal is applied to the
LOM object by thermal spraying and then is filled by metal casting. A sound electrode is
therefore obtained a used to manufacture the steel die.
In this preliminary work simple geometry electrodes have been considered and tested in
EDM process. Material Removal Rate and wear of electrodes obtained with different
materials and techniques (metal spraying, metal casting) have been evaluated and
compared with those of conventional machined electrodes
Prediction and validation of grain shape evolution by 3D FEM simulations of a real industrial profile
No full textThe simulation of microstructural evolution during the extrusion of an AA6063 industrial profile with the commercial Qform VX code is presented and discussed. The description of the grain shape evolution model through specifically developed user-routine is initially presented, then the experimental setup is described in details. Predicted numerical results are compared and discussed with respect to experimental data: relevant outputs like load-stroke diagram, profile speed and thermal distribution in the profile well match with the experimental data. The prediction of the final grain size obtained by the code with air quenching conditions is then compared to experimental measurements. A discussion on potentials and limits of the proposed model is finally presented
New Possibilities in the Fabrication of Hybrid Components with Big Dimensions by Means of Selective Laser Melting (SLM)
No full textAbstractThe application of laser technology to welding of dissimilar AISI316 stainless steel components manufactured with selective laser melting (SLM) and traditional methods has been investigated. The role of laser parameters on weld bead formation has been studied experimentally, with particular attention placed on effects occurring at the interface between the two parts. In order to assess weld bead characteristics, standardised tensile tests were carried out on suitable specimens and the fracture zone was analysed. The results highlighted the possibility of exploiting suitable process parameters to appropriately shape the heat affected and fusion zones in order to maximise the mechanical performance of the component and minimise interactions between the two parent metals in the weld bead
Efficiency of conformal cooling channels inserts for extrusion dies
Full text linkDuring aluminum extrusion process, critical temperatures can be reached both in the profile and in the tooling set due to the high pre-heating temperatures and to the work spent in overcoming friction at the workpiece/tool interfaces and in deforming the billet that is converted into heat. By considering that especially the rising of temperature in the profile can represents a critical aspect of the process strongly limiting the maximum achievable extrusion speed, liquid nitrogen die cooling is becoming a consolidated industrial practice in order to increase the process productivity. If cooling channels are traditionally manufactured by subtractive technologies on a third plate (the backer), a more flexible and efficient solution is offered by the selective laser melting (SLM) technology. SLM allows the design of free-form channels with the opportunity to efficiently remove the heat as near as possible to the bearing zones where the highest temperatures are reached. In the present work, the design approach and the manufacturing parameters of an SLM printed H13 die insert for the extrusion of a 10 mm round bar are presented. In addition, the extrusion process is simulated by means of the COMSOL code accounting for the nitrogen cooling effect. Experimental extrusion trials have been furthermore performed with ZM21 magnesium and 6063 aluminum alloys to assess the potentiality of the conformal cooling channel design and to validate the developed numerical model. As main result, a good experimental numerical matching has been achieved with peak errors of 7.5% and 14% in terms of temperature and extrusion load respectively
- …
