Domingo Morales-Palma

University of Seville | US · Department of Mechanical Engineering and Manufacturing

Recently, the research interest of hole-flanging has turned from conventional press-working to SPIF as a viable process for small- and medium-sized batches. Both technologies have been studied separately using different approaches and, therefore, most studies cannot be easily compared. Besides, some studies that measured the formability in SPIF usi...

Hole flanges are commonly manufactured in mass production by conventional press-working. In an industrial context, the process limits are usually evaluated by means of the Limiting Forming Ratio (LFR), which defines the maximum attainable diameter of the flange related to the initial pre-cut hole. Nevertheless, the LFR does not provide enough infor...

Traditionally the fracture in sheet metal forming is characterized by the fracture forming limit (FFL) curve typically obtained by using conventional Nakajima tests. This curve is implicitly assumed a material property. Single point incremental forming (SPIF) is a novel and flexible forming process characterized by the ability to suppress local nec...

Flanging is a forming process that is commonly used in many high technology industrial applications such as the manufacturing of thin-walled aircraft structures as wing ribs that are formed using rubber-pad forming during the last forming stages with the aim of increasing the stiffness of the component edges. In addition, the performance of hole-fl...

Models for Manufacturing is a new approach proposed by the authors to apply Model-based Systems Engineering concepts to Manufacturing. The methodology under development is supported by a 3-layer framework (referred to as Data Base and Interfaces, Ontology and Software Tools layers) and simple and easy-to-use software tools. This work presents a pre...

The Forming Limit Curve (FLC) shows the limit combinations of principal strains on the sheet surface that can be successfully achieved before necking appears. Above the FLC, Atkins in 1996 proposed the existence of an unstable region where localized necking develops before reaching at the Fracture Forming Limit (FFL). Only the methodology for the e...

Reconfigurable Manufacturing Systems (RMS) have gained prominence in the Aerospace Industry in recent years for several reasons. These include drastic changes in production capacity due to post-COVID19 and new environmental regulations to adapt to remain competitive; however, the current RMS design has not changed. Ontology-based engineering system...

An analytical model of the cold wire drawing process is used to implement an optimization procedure. The optimization aims to minimize the number of passes required to achieve a given reduction while maintaining a safe value of the drawing stress in each step. The number of passes and the sequence of intermediate diameters are the output of the opt...

Models for Manufacturing (MfM) is a methodology currently under development with a novel approach to applying Ontology-Based Engineering concepts to manufacturing. MfM is based in a 3-Layer Model (3LM) framework: a Data layer that collects all the information, e.g. in databases, an Ontology layer for ontological definition containing the domain know...

In recent years, manufacturing companies have become more flexible and reconfigurable to adapt to new manufacturing paradigms and market demands. Simulation technology, which is one of the enablers of Industry 4.0, is usually used to evaluate the performance of manufacturing lines to predict their response against some manufacturing scenario. The c...

Manufacturing ontologies in the aerospace industry have been an active research topic during the last decade, as a mean for tool agnostic modeling and simulations activities supporting the product development process. This work reviews Models for Manufacturing (MfM) methodology, proposed by the authors to support ontologies generation in this field...

Model-Based System Engineering (MBSE) supports the conceptualization of systems, proposes independence between knowledge conceptualization and tools, and fosters reusability and interoperability. There are several research works oriented to define ontologies in the manufacturing domain, but only a few consider their use in an Ontology-based Enginee...

New aerospace product developments need to be done following economic and environmental drivers like costs reduction, secure a short time-to-market, reduce total carbon footprint, among others. Aerospace manufacturing systems must quickly adapt to new products or driver changes, reusing existing industrial resources with enough flexibility to be ad...

Today, aerospace products need to be developed following economic and environmental drivers. Aerospace production systems must adapt to novel products that reuse current industrial resources to accommodate new scenarios. Reconfigurable Production Systems (RPS) or Reconfigurable Manufacturing Systems (RMS) is the answer. This paper aims to perform a...

This study presents a numerical analysis of the tube expansion process by conventional tube-end forming versus single point incremental forming (SPIF) using DEFORM. The work includes the assessment of the strain paths within the principal strain space of these processes with respect to the formability limits as well as their evaluation within the e...

Models for Manufacturing (MfM) is a novel approach proposed by the authors to apply Ontology-Based Engineering (OBE) concepts to Manufacturing. The methodology is based in a 3-Layers Model (3LM) framework and supported by any modelling tools easy-to-use. The Ontology layer comprises the ontological definition holding the knowledge of the domain. Th...

Nowadays, industrial production is required to reduce industrialization times and development costs for new products while maintaining high quality standards. In this context, the development of new flexible manufacturing technologies has gained relevance in the last few years. The use of Fused Deposition Modelling (FDM) additive technique has been...

The necking criteria based on the maximum force principle, such as the Swift and Hill necking models, have been extensively used in the past to study sheet formability. Many extensions or modifications of these criteria have been proposed to improve necking predictions under only stretching conditions. Recently, the authors proposed two approaches...

Recently, hole-flanging by single-stage incremental forming (SPIF) has been proposed as a suitable process to perform hole flanges for small- and medium-sized batches with high flexibility in shape. However, this incremental forming has many differences compared with the conventional press working operation in terms of strain and thickness distribu...

The strain-based forming limit curve is the traditional tool to assess the formability of metal sheets. However, its application should be restricted to proportional loading processes under uniform strain conditions. Several works have focused on overcoming this limitation to characterize the safe process windows in industrial stretch-bend forming...

Recently, the research interest in hole-flanging for small and medium-sized batches has turned from conventional press-working to SPIF due to the advantages of incremental forming, such as flexibility and cost of tools. Both technologies have been studied separately using different approaches and, therefore, most studies cannot be easily compared....

During the conceptual design phase of an aerospace assembly line, the Design Solutions that will meet the functional and industrial requirements are defined. As a result it is possible to define an early conceptual design of the assembly line and its basic parameters. Assembly Line Balancing (ALB) comprises ordering of tasks among stations to satis...

The evaluation of the enhanced formability in incremental sheet forming processes (ISF), and especially in its simplest variant single point incremental forming (SPIF), has been intensively studied within the sheet metal forming community for the last decade. In general, the formability limit in SPIF is defined by means of the fracture forming limi...

Model-Based System Engineering (MBSE) provides a conceptualization of systems and proposes the independence between knowledge conceptualization and tools, reusability and interoperability. In the scope of manufacturing there are several research works oriented to define ontologies, but only a few consider a framework to manage the whole lifecycle o...

Industrial sheet metal forming processes with certain complexity involve intrinsically non-linear strain paths, abrupt changes in the local strain ratio (β) due to successive stages during the manufacturing operation and/or the existence of strain/stress gradients through the sheet thickness due to the simultaneous action of stretching and bending....

A systematic methodology for determining the formability limits of thin-walled tubes based on strain analysis has been recently presented by the authors with the aim of evaluating formability and failure within the principal strain space, analogously to the conventional procedures used in sheet metal. This methodology for establishing the formabili...

Single point incremental forming (SPIF) has been demonstrated to accomplish current trends and requirements in industry. Recent studies have applied this technology to hole-flanging by performing different forming strategies using one or multiple stages. In this work, an optimization procedure is proposed to balance fabrication time and thickness d...

To enhance multidisciplinary design and simulation of complex systems, MBSE (Model Based Systems Engineering) is a methodology where computer aided graphical modeling authoring tools are used to specify functions and behaviors of the systems. Simulation tools bring about a system behavioral abstraction required for the design of complex products. M...

Single Point Incremental Forming (SPIF) is a novel and flexible forming technology that has been used in the last few years to obtain a variety of customized sheet parts. One of the most valuable advantages of this process is its ability to suppress the localized necking of the sheet, allowing a stable plastic deformation up to the ductile fracture...

Incremental sheet forming is a novel technology that has significant benefits compared to conventional forming. However, it is a time-consuming process that is usually carried out in several forming stages to homogenize deformation and avoid material failure. In hole-flanging operations by SPIF, a single-stage strategy might provide functional flan...

This paper analyses the flangeability of AA2024-T3 sheets using single point incremental forming (SPIF). With this purpose, a series of process parameters is considered including flange length and width, tool radius and spindle speed. An initial experimental campaign is carried out for the evaluation of the limiting strain states of the flanges wit...

This paper presents recent research experiences developed with the aim of manufacturing cranial prostheses in polymeric sheet using Incremental Sheet Forming (ISF) technologies. With this purpose, different approaches have been carried out in Single-Point Incremental Forming (SPIF) and Two-Point Incremental Forming (TPIF) in order to produce custom...

A drawback of the hole-flanging process by single-stage SPIF is the non-uniform thickness obtained along the flange. Multi-stage strategies have been used to improve it, however they increase notably the manufacturing time. This work presents a preliminary study of the tool paths for a hole-flanging process by SPIF in two stages. An intermediate ge...

The use of Single-Point Incremental Forming (SPIF) technology in hole flanging operations using multi-stages strategies have been widely studied in the last few years. However, these strategies are very time-consuming, limiting its industrial application. In a very recent work of the authors, the capability of SPIF process to successfully perform h...

Single Point Incremental Forming (SPIF) is a flexible and economic manufacturing process with a strong potential for manufacturing small and medium batches of highly customized parts. Formability and failure in SPIF have been intensively discussed in recent years, especially because this process allows stable plastic deformation well above the conv...

The maximum force criteria and their derivatives, the Swift and Hill criteria, have been extensively used in the past to study sheet formability. Many extensions or modifications of these criteria have been proposed to improve necking predictions under only stretching conditions. This work analyses the maximum force principle under stretch-bending...

This paper presents the latest developments in a digital documentation project related to manufacturing processes on machine tools. The project is supported by engineering students doing their bachelor/master thesis within this field. Different virtual models have been developed by using CATIA V5, such as conventional and CNC machines, several part...

The aim of this paper is to analyze the use of Finite Element Analysis (FEA) in the teaching-learning strategy of metal forming processes. To this end, students are proposed to use the commercial package DEFORM-3D® for the development of their bachelor and master theses within the research line on incremental sheet forming processes. The student ac...

Purpose This paper proposes a functional methodology to produce cranial prostheses in polymeric sheet. Within the scope of rapid prototyping technologies, the Single-Point Incremental Forming (SPIF) process is used in order to demonstrate its capabilities to perform customised medical parts. Design/methodology/approach The methodology starts pro...

Recent studies show the capability of single-point incremental forming to successfully perform hole-flanging operations using multi-stage strategies. However, multi-stage strategies are time-consuming and, according to the geometrical and surface constraints of the part, the number of stages for obtaining a fully functional piece should be minimize...

This work aims to generate the digital documentation related to a number of manufacturing processes on different machine tools. The project is developed with the contribution of engineering students doing their final thesis within this field. Different machine tools and machining and incremental forming processes have been virtualized by using the...

This work presents a novel teaching experience in the framework of final master and bachelor theses within the research line on incremental sheet forming processes. This forming process involves a series of competences dealing with manufacturing technology at a wide multidisciplinary level. This paper analyses these different manufacturing topics a...

Forming limit diagrams (FLD's) are used to evaluate the workability of metal sheets. FLD's provide the failure locus at which plastic instability occurs and localized necking develops (commonly designated as the forming limit curve - FLC), and the failure loci at the onset of fracture by tension (FFL) or by in-plane shear (SFFL). The interest of me...

Recent studies show the capability of single-point incremental forming to perform successfully hole-flanging operations using multi-stage strategies. The aim of this work is to investigate the ability of the SPIF process to perform hole-flanges in a single stage, contributing to a better understanding of the formability of the sheet in this demandi...

Forming limit diagrams (FLDs) are currently the most useful and used tool for evaluating the workability of metal sheets. FLDs provide the failure locus at the onset of necking (commonly designated as the forming limit curve [FLC]) and at the onset of fracture in the principal strain space.The FLC is usually determined by means of Nakazima and Marc...

In this paper the formability of AA2024-T3 metal sheets is experimentally analyzed. For this purpose, a series of Stretch- Bending and Incremental Sheet Forming (ISF) tests are carried out. The former tests allow determine the formability limits through the evaluation of necking and fracture using the optical deformation measurement system ARAMIS®...

Strain gradients have a beneficial effect on the initiation of necking and ductile fracture in metal sheets. Thus, the use of classical failure criteria, assuming a uniform stress distribution across the thickness, is highly questionable for the study of sheet formability. This work suggests a new approach to describe the mechanism of failure under...

This work presents a project of teaching innovation on the subject Technology of Manufacturing that has been developed for the last five years. The objective is to stimulate students for training through a self-evaluation system based on e-learning tools, in agreement with the guidelines of the European Higher Education Area (EHEA). The system incl...

The aim of this contribution is to promote the use of FEM based numerical simulations for teaching the fundamentals of manufacturing processes. In particular, it focuses on metal forming processes, which by their mathematical modelling complexity can only be tackled in a very elementary way using traditional methods. This enables an active teaching...

In this paper, the capability of some of the mechanisms involved in incremental sheet forming (ISF) processes to postpone fracture of the metal sheet is analyzed. A finite element (FE) model of an incremental forming operation and a conventional stretch-bending operation is performed. The local evolution of the straining and the distribution of hyd...

The presence of a strain gradient through thickness increases the strain level on the surface needed to attain failure. Some recent works analyse the ability of Concave-Side Rule to predict the initiation of necking, based on the stress/strain level in certain material volume located at the inner side of the sheet. According to this model, an accur...

Recent works analyse the capability of the concept of the Concave-Side Rule (for necking) and Convex-Side Rule (for fracture) to predict the initiation of failure of a sheet under stress/strain gradients. A natural improvement of these rules has been suggested by the present authors by recognising that necking or fracture should be controlled by th...

In this paper a FE model is carried out in order to analyse the capability of some of the mechanisms involved in incremental sheet forming (ISF) processes to postpone fracture of the metal sheet. Two different processes are simulated using the finite element method: an incremental forming operation and a stretch-bending operation. The local evoluti...

The forming limit curve (FLC) at necking is one of the most widely used tools for assessing the formability of a metal sheet. Several methodologies have been proposed for predicting the onset of necking and estimating the forming limits. However, these criteria are mainly focused on specific situations in which a uniform strain profile through the...

Stress/strain gradients have a clearly beneficial effect on the initiation of necking and ductile fracture in metal sheets. Thus, the use of classical failure criteria, assuming a uniform stress distribution across the thickness, is highly questionable for the study of sheet formability. The present work analyses the strain/stress evolution in a sh...

The stress/strain gradient has a clear stabilizing effect in the initiation of necking and subsequent failure of metal sheets. In situations where bending due to mild or small forming radius are present, the influence of these gradients cannot be neglected by using the mean strain through the specimen thickness as a representative strain. Therefore...

The standard ISO 12004-2 has recently established a methodology for estimating limit strains in Marciniak and Nakajima tests, that is, situations in which the strain gradient through the sheet thickness does not play an important role. This method, known as a ``position-dependent method,'' is based on the analysis of the major strain profile just b...

A study of the strain/stress gradient effect in the formability of stretch-bend metal sheets is presented. Depending on the severity of these gradients, two independent kinds of failure can be defined: Necking- and Fracture- controlled Failure. In a previous work the authors assumed that the former failure mode takes place when the inner fibre neck...

The 2024-T3 aluminum alloy is extensively used for making aircraft parts. This alloy has a relatively low ductility at room temperature, and is generally heat-treated before forming. The present study experimentally and numerically analyzes the formability of AA2024-T3 sheets subjected to biaxial stretching. The aim of this study is to provide an a...

The fundamental objective of our work is the definition of a schema for knowledge bases that integrates knowledge about the design of a family of products with that of its process of manufacture and other activities of the products life cycle. Our approach to design knowledge management follows three general principles. First, the description of al...