F. Lambiase

Finite Element Analysis of Material Flow in Mechanical Clinching with Extensible Dies

An investigation of the material flow during the clinching process with extensible dies is carried out. Clinched joints were produced under different forming loads to evaluate the evolution of the joints’ profile experimentally. Tensile-shear tests were conducted to evaluate the influence of the forming load on mechanical strength of the clinched joint. Since the joints’ strength depends on the joints’ profile, which in turn depends on the punch-die cavity volume, an analysis of the forces acting on the extensible dies was carried out. A finite element model was developed and validated by comparing the predicted and measured material flow and quality criteria (e.g., neck thickness and undercut). Therefore, the FE model was utilized to analyze the evolution of contact forces acting on the die sectors during the joining process. Furthermore, the main causes of the asymmetry in the cross section of such joints have been studied. It turned out that the axial asymmetry due to material flow within the gap between consecutive die sectors increases with the punch force and the sheet thickness.

From the experimental simulation to integrated non-destructive analysis by means of optical and infrared techniques: results compared

In this work the possibility of modeling manufacturing ceramic products is analyzed through the application of transient thermography, holographic interferometry and digital speckle photography, in order to identify the subsurface defects characteristics. This integrated method could be used to understand the nature of heterogeneous materials (such as plastic, sponge simulating a void, wood, aluminum) potentially contained within ceramic materials, as well as to predict crack formation due to them. The paper presents the analysis of green ceramic tile containing defects of different types and sizes located at different depths. The finite element method is used for solving the problem of transient heat transfer occurring in experimental conditions. Unknown parameters of the numerical model (such as convective heat transfer coefficients and sample surface emissivity) were adjusted to obtain numerical simulation results as close as possible to those obtained experimentally. Similarities and differences between experimental and simulated data are analyzed and discussed. Possibilities for improving the results and further developments are proposed.

An Analytical Model for Evaluation of Bending Angle in Laser Forming of Metal Sheets

In this study, an analytical model is developed to evaluate the bending angle in laser forming of metal sheets. The model is based on the assumption of elastic-bending theory without taking into account plastic deformation during heating and cooling phases. A thermal field is first established, then the thermal component of deformation is calculated and it is used in the strain balance to evaluate the bending angle. The basic idea is that it is possible to use a two-layer model whereas the heated layer thickness depends on the effective temperature distribution along the sheet thickness. A comprehensive experimental study is carried out and the main process parameters, i.e., laser power, scanning speed, sheet thickness, were varied among several levels to evaluate the accuracy of the developed model. Model predictions were confirmed by experimental measurements especially on materials with low conductivity. The established analytical model has demonstrated to provide a great insight into the process parameters effects onto the deformation mechanism within pure temperature gradient mechanism and bucking to temperature gradient transition conditions.

Automated Procedure for Roll Pass Design

The aim of this work has been to develop an automatic roll pass design method, capable of minimizing the number of roll passes. The adoption of artificial intelligence technologies, particularly expert systems, and a hybrid model for the surface profile evaluation of rolled bars, has allowed us to model the search for the minimal sequence with a tree path search. This approach permitted a geometrical optimization of roll passes while allowing automation of the roll pass design process. Moreover, the heuristic nature of the inferential engine contributes a great deal toward reducing search time, thus allowing such a system to be employed for industrial purposes. Finally, this new approach was compared with other recently developed automatic systems to validate and measure possible improvements among them.

Dimensional analysis in steel rod rolling for different types of grooves

Sequence design for shape-rolling processes consists of roll pass and profile design, i.e., transforming the billet into a final shape. For the prediction of the mean effective strain of the workpiece during rod rolling, an analytical model by Shinokura and Takai was used. They verified the formula by applying it to a variety of rod-rolling geometries (oval-square, oval-round, square diamond, and diamond-diamond). Today, on the other hand, the finite element (FE) techniques allow analysis of rolling processes in such a way as to simplify the work of design engineers. In this study, a round-oval pass and a round-flat oval pass are analyzed for steel rod rolling. In particular, the analysis of the spread, the surface profile, and cross-sectional area of the workpiece were conducted during rolling. Experimental data such as the maximum spread and the radius are compared with the results of the analytical model and FE analysis.

Experimental and Finite Element Investigation of Roll Drawing Process

In this research, the wire drawing process with flat roller dies is investigated. A prototypal apparatus is developed to conduct experimental tests on such a process and analyze the influence of main roll drawing parameters (e.g., incoming wire diameter, forming rolls diameter, thickness reduction, and friction conditions) on geometrical characteristics of flattened wires. A finite element model (FEM) is developed to simulate the deformation of the wire during the process. Within the entire range of experiments, a good agreement between experimental data and numerical results is found which allows validating the FE model. A further observation from the experimental program and numerical simulations is that a complicated dependence of the lateral spread of wire and width of contact area on process parameters exists during wire drawing with roller dies.

Experimental Investigation of Parameters Effect on Laser Forming Productiveness

In the present study the deformation behaviour of thin steel sheets processed by using laser forming has been investigated as well as the temperature distribution along the sheet thickness. A campaign of experimental tests has been carried out on stainless steel AISI 304 in order to evaluate the influence of the main process parameters, such as laser power, scanning speed and sheet thickness on the bending angle and temperature of upper and lower surfaces. In addition, in order to prevent oxidation, the optimal interval duration between two consecutive scans has been assessed. A productivity index has been also introduced in order to evaluate the effectiveness of different process parameters configuration.

Numerical and Experimental Investigation of Process Parameters Effect of Low Carbon Steel Wire Produced with Roll Drawing Process

The effect of roll drawing process parameters on geometrical characteristics of flat roll draw wires is analyzed. Low carbon steel wires AISI 1010 are used in the experimental tests to assess the final geometry, mainly characterized by the width of flat wires, varying among several experimental levels the main process parameters i.e., initial wire dimensions, height reduction and lubrication conditions. Design of experiment technique was used to define the experimental plan and statistical techniques, such as analysis of mean (ANOM) and variance (AVOVA), were used to evaluate the effective influence of previous cited process parameters on final geometry of wire. A finite element model is developed to investigate a further process parameter i.e. the working rolls dimensions. In order to validate the finite element model, a campaign of experimental tests was conducted and the geometrical predictions of FE model were compared with experimental mea-surements with particular attention to final wire width, width of contact area and wire elongation. A linear regression analysis was performed and an empirical formulation to forecast the lateral spread of wire according to the main process parameters was developed.

An integrated approach to the analysis of automotive assembly activities using digital manufacturing tools

Current trends towards products customisation, increase of quality and reduction on delivery time are radically changing the products/processes design approach. Automotive companies, which continuously face product variant soaring, require new methods development for products/equipment design, manufacturing system planning and process simulation. This paper studies the stages needed to develop an integrated Digital Factory (DF) analysis to increase system performances and resources productivity. A three-step concurrent approach, namely activities balancing, task ergonomic improvement and devices redesign, carried out within 3D virtual environments is referred to an automotive case to demonstrate the advantages of DF over conventional analysis techniques. Finally, a costs analysis is reported to prove the economical feasibility of the advances suggested by such methodology.

Single point incremental forming: Formability of PC sheets

Recent research on Single Point Incremental Forming of polymers has slightly covered the possibility of expanding the materials capability window of this flexible forming process beyond metals, by demonstrating the workability of thermoplastic polymers at room temperature. Given the different behaviour of polymers compared to metals, different aspects need to be deepened to better understand the behaviour of these materials when incrementally formed. Thus, the aim of the work is to investigate the formability of incrementally formed polycarbonate thin sheets. To this end, an experimental investigation at room temperature was conducted involving formability tests; varying wall angle cone and pyramid frusta were manufactured by processing polycarbonate sheets with different thicknesses and using tools with different diameters, in order to draw conclusions on the formability of polymer sheets through the evaluation of the forming angles and the observation of the failure mechanisms.Recent research on Single Point Incremental Forming of polymers has slightly covered the possibility of expanding the materials capability window of this flexible forming process beyond metals, by demonstrating the workability of thermoplastic polymers at room temperature. Given the different behaviour of polymers compared to metals, different aspects need to be deepened to better understand the behaviour of these materials when incrementally formed. Thus, the aim of the work is to investigate the formability of incrementally formed polycarbonate thin sheets. To this end, an experimental investigation at room temperature was conducted involving formability tests; varying wall angle cone and pyramid frusta were manufactured by processing polycarbonate sheets with different thicknesses and using tools with different diameters, in order to draw conclusions on the formability of polymer sheets through the evaluation of the forming angles and the observation of the failure mechanisms.