F. Capece Minutolo

Negative and positive incremental forming: Comparison by geometrical, experimental, and FEM considerations

ABSTRACT This study compares negative incremental forming (NIF) and positive incremental forming (PIF) processes by geometrical considerations, finite element method (FEM) analyses, and experimental evaluations. Conical frusta were manufactured starting from AA5052H19 aluminum alloy sheets using both techniques. The processes were also simulated with LS-DYNA software and a close correlation between the experimental and numerical results was observed. The analysis of forming forces, forming limit diagrams (FLDs), and sheets thinning highlights that the PIF technique allows one to reach higher formability and geometrical accuracy. Finally, the differences in terms of surface quality were also discussed.

Forces analysis in sheet incremental forming and comparison of experimental and simulation results

Publisher Summary This chapter characterizes innovative techniques, such as hydroforming and incremental forming by the possibility to be easily adapted to realize a small production lot with low tools cost. The chapter discusses grooves in sheets, which have been realized by means of the incremental forming technology. It presents the forces analysis in relation to the tool path and its diameter. FEM simulations are achieved with the purpose to carry out a comparison between the forces values experimentally pointed out and the ones by FEM. FE analysis also allows the individualization of the points where failure conditions take place by simple evaluation of the reach stress values. Therefore, the FE method can be used to determine the tool path in the design phase of the process cycle.

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.

Formability Evaluation of Grade 1 Titanium Sheets Depending on the Temperature by FE Analyses

Nowadays, the need of developing high flexible forming processes matches with the need of weight reduction. In this light, the incremental forming of titanium alloys sheets can guarantee both these aspects by combining the flexibility of the process, particularly suggested for small batches and customized parts, with the good properties of titanium alloys, in particular for aerospace applications.The aim of this work was to obtain information useful to enhance the general knowledge of the hot incremental forming processes of grade 1 titanium sheets at different temperatures.First, both tensile and straight groove tests were carried out by varying the test temperature; in this phase, information regarding both the forming forces and the wear phenomena due to the tool-sheet contact was acquired.Successively, on the basis of the mechanical characterization of the sheets previously carried out, explicit analyses, effectuated by a non-linear FE code, allowed to determine the formability curves of the sheets for the different temperatures.

Specific pressure in steel rod rolling with grooves

In the design of roll stands for use in grooved steel rod rolling, the contact pressure between the rolls and the incoming workpiece is very important. This value can be estimated with the help of a number of analytical and semiempirical models described in the published scientific and technical literature. In this study, the possibility of using numerical simulation in determining the contact pressure during the rolling of a round bar with oval grooves is analyzed. The results of the numerical analyses are then compared with those of two other modified analytical models.

Wear behaviour of epoxy resin filled with hard powders

The development of high performance materials based on epoxy resin finds a growing number of applications in which high wear resistance is required. One major drawback in many of these applications is the relatively poor wear resistance of the epoxy resin. Therefore, in order to investigate on the possibility of increasing wear resistance of thermoset polymers filled with hard powders, sliding tests are carried out by means of a pin on disc apparatus. In particular, composite resins, constituted by an epoxy resin filled with different contents and sizes of Silicon Carbide powder, are analyzed; the wear resistance, in terms of volume loss, is measured for different abrasive counterfaces and loads.

Influence of Eta-Phase on Wear Behavior of WC-Co Carbides

Cemented carbides, also known as Widia, are hard metals produced by sintering process and widely used in mechanical machining. They show high cutting capacity and good wear resistance; consequently, they result to be excellent materials for manufacturing cutting tools and sandblast nozzles. In this work, the wear resistance of WC-Co carbides containing Eta-phase, a secondary phase present in the hard metals when a carbon content deficiency occurs, is analyzed. Different mixtures of carbide are prepared and sintered, with different weight percentages of carbon, in order to form Eta-phase and then analyze how the carbon content influences the wear resistance of the material. This characterization is carried out by abrasive wear tests. The test parameters are chosen considering the working conditions of sandblast nozzles. Additional information is gathered through microscopic observations and the evaluation of hardness and microhardness of the different mixtures. The analyses highlight that there is a limit of carbon content below which bad sintering occurs. Considering the mixtures without these sintering problems, they show a wear resistance depending on the size and distribution of the Eta-phase; moreover, the one with high carbon content deficiency shows the best performance.

Validation of a FEM Model for the Simulation of the Cold Roll Forming Process

Cold roll forming is a process for plastic deformation, which allows realizing profiles, with a defined section and established length, from the plastic deformation of a metal sheet. The sheet is induced to cross several stands of rolls, arranged along the same axis of advancing. The rolls induce plastic deformation in the sheet and then lead it to the desired geometric configuration. In order to control the geometric parameters of the plate during the profiling, it was created a FEM model to simulate the final stage of the technological process, developed by an industrial production line of a company located in Naples (Italy), that sells tubes with several cross sections. In this phase, the semi-finished product, having a circular cross section, is forced to cross through four stands of rolls. In this way, it changes the geometric condition of the cross section from circular to square. The model was carried out using a non-linear calculation code, which allows analyzing the parameters of interest in the different process steps. The results, obtained numerically, were compared with the experimental ones through the measurement of five specimens, obtained directly from technological process. The values of percentage deviation, regarding the external dimension and the thickness, for each step of advancement, do not exceed the 3% of error. Then, the analysis results denote the capability to simulate the cold roll forming process using finite element method.

Optimization of a hydroforming process to realize asymmetrical aeronautical components by FE analysis

Publisher Summary Hydroforming process is an effective method for manufacturing complicated parts. Hydroforming allows overcoming some of the limitations of conventional deep drawing, increasing the draw ratio and minimizing the thickness reduction of the formed parts. Among the advantages introduced by hydroforming, there are a great flexibility and a remarkable reduction of tooling costs. This process is quite sensitive to the characteristics of the pressure growth laws and the friction between the sheet and the elements of the tooling. This chapter discusses a numerical simulation that has been carried out using the explicit finite element code LS-DYNA with the purpose to optimize a hydroforming process related to the achievement of an asymmetrical aeronautical component. In particular, the number of the steps of the manufacturing cycle actually used to produce the component has been reduced considering the FEM results.