Guido Berti

A combined DFMA and TRIZ approach to the simplification of product structure

Abstract In order to tackle the problem of part count reduction more effectively, an approach that combines the design for manufacture and assembly (DFMA) method with the theory of inventive problem solving (TRIZ) is presented in this paper. This new approach was developed by merging the common characteristics and connecting the complementary aspects of the two methods, which were then applied to the redesign of a satellite antenna.

Experimental evaluation and FE simulation of thermal conditions at tool surface during cooling and deformation phases in hot forging operations

Abstract In hot and warm forging operations, surface layers of tools at the tool-workpiece interface are not only exposed to high mechanical stresses but also to severe temperature cycles, which often lead to loss of strength and hardness and thermal fatigue failure as well. This paper offers an approach for determining heat transfer conditions at the surface of punches and dies during both the deformation and the cooling-lubrication phases of forging cycles. The approach is based on temperature readings inside the tool, FE simulation and inverse analysis. An application case is illustrated where operating conditions reproduce hot forging of turbine airfoil sections.

Application of empirical modelling in multi-layers membrane manufacturing

Abstract Multistructured membranes based on ultrafine fibers of polymethylmethacrylate-co-methacrylic acid (PMMA-co-MAA) and TiO2 nanoparticles have been obtained by electrohydrodynamic (EHD) technologies, for active filter media manufacturing. Process optimization of the nanofibers based layers has been investigated by response surface methodology (RSM) in order to predict the domain of the parameters where the smallest fiber diameter can be achieved. A quantitative relationship between electrospinning parameters and the responses (mean diameter and standard deviation) was established and then the final multi-layers structure of nanofibers and nanoparticles has been achieved for a controlled and robust process. The nanostructured membranes have been characterized by SEM imaging, EDAX, TGA analysis and water vapour permeability and their photocatalytic activity has been tested on VOCs degradation.

Enhancing performances of SHPB for determination of flow curves

Abstract A compression test on a Split Hopkinson Pressure Bar (SHPB) is the most common testing method adopted to determine material flow curves in a quite wide range of high strain rates. However, in most ordinary SHPB applications material rheology can only be investigated up to a rather low strain. Furthermore, several phenomena, including friction at interfaces and radial and axial inertia, are potential sources of inaccuracy for flow stress data. The paper presents the main design-guidelines followed when developing a high-performance SHPB system for the determination of accurate flow curves. The results from hot compression tests carried out on Aluminium- and Nickel-alloys prove that with the developed system most of the limitations of ordinary-SHPBs are overcome and system performances significantly improve.

Tool Cost Estimating at the Early Stages of Cold Forging Process Design

Identifying the most appropriate sequence of cold forging operations for a new part requires a number of technological and economical evaluations concerning loads, mechanical properties of the forged component, its producibility on the machines as well as costs for equipment and associate tooling. This paper presents a methodology for estimating initial and maintenance costs for cold forging tools. This methodology is for use of planners at the early stages of process design, when the sequence of forging operations and equipment are decided and before details of the tooling system are available.

Wear in Hot and Warm Forging: Design and Validation of an New Laboratory Test

Abstract A simulative wear test for hot and warm forging tools is presented which has been developed by the Authors with the twofold purpose of (i) verifying the applicability of wear micro-mechanical models in simulation of hot and warm bulk metal forming operations using FEM codes and (ii) evaluating wear parameters by an inverse numerical technique. In its simple configuration, the test embodies many of the tribosytems encountered in industrial forging operations and relevant tool wear and failure mechanisms, such as abrasion, thermal fatigue as well as permanent deformation of tool surface. The paper focuses on the design of the test configuration and the description of testing and measuring apparatuses, including those for temperatures and heat transfer coefficient determination. Validation of the test through test runs and determination of wear profile on tools end the paper.

A virtual prototyping environment for a robust design of an injection moulding process

Abstract This paper proposes a new approach that enables a robust optimisation of the injection moulding process, based on the integration of numerical simulations, Response Surface Methodology and stochastic simulations in a type of integrated environment known as a virtual prototyping environment (VPE). The principal aim of the proposed approach is to include in the numerical setup of injection moulding the effects of fluctuations of process parameters. To clarify the proposed methodology, the paper details its application to the injection moulding process for the production of an engine cover. The moulded part presents some critical tolerances on different dimensions because of sealing and assembly requirements and the application of the VPE makes it possible to perform a robust setup taking into account the process fluctuations. The numerical prediction was confirmed by real production measurements on small pre-production runs performed adopting the moulding window explored in the virtual setup.

A fractional derivative model for single-link mechanism vibration

A model for a flexible pinned-free link is defined, which is based on a set of linear uncoupled equations and which is even valid for large rotations. A stress-strain relationship based on fractional derivatives is used to define the material properties. Experimental findings and numerical results are compared.SommarioViene definito un modello matematico lineare per lo studio della dinamica di un meccanismo a membro unico deformabile. Tale modello é costituito da equazioni disaccoppiate che rappresentano sia il moto del corpo rigido di riferimento sia i contributi modali alla vibrazione. La relazione tensione deformazione del materiale considerato é definita a mezzo di derivoidi. I risultati ottenuti numericamente sono confrontati con registrazioni sperimentali.

Hydrostatic Microextrusion of Steel and Copper

The paper presents an experimental investigation based on hydrostatic micro extrusion of billets in low carbon steel and commercially pure copper, and the relevant results. The starting billets have a diameter of 0.3 mm and are 5 mm long; a high pressure generator consisting of a manually operated piston screw pump is used to pressurize the fluid up to 4200 bar, the screw pump is connected through a 3‐way distribution block to the extrusion die and to a strain gauge high pressure sensor. The sensor has a full scale of 5000 bar and the extrusion pressure is acquired at a sampling rate of 2 kHz by means of an acquisition program written in the LabVIEW environment. Tests have been conducted at room temperature and a lubricant for wire drawing (Chemetall Gardolube DO 338) acts both as the pressurizing fluid and lubricant too. In addition, billets were graphite coated. Different fluid pressures and process durations have been adopted, resulting in different extrusion lengths. The required extrusion pressure is...

Micro Wire-Drawing: Experiments And Modelling

In the paper, the authors propose to adopt the micro wire‐drawing as a key for investigating models of micro forming processes. The reasons of this choice arose in the fact that this process can be considered a quasi‐stationary process where tribological conditions at the interface between the material and the die can be assumed to be constant during the whole deformation. Two different materials have been investigated: i) a low‐carbon steel and, ii) a nonferrous metal (copper). The micro hardness and tensile tests performed on each drawn wire show a thin hardened layer (more evident then in macro wires) on the external surface of the wire and hardening decreases rapidly from the surface layer to the center. For the copper wire this effect is reduced and traditional material constitutive model seems to be adequate to predict experimentation. For the low‐carbon steel a modified constitutive material model has been proposed and implemented in a FE code giving a better agreement with the experiments.