Surface texture of stamping tools affects the performance of the tool, tool life, and surface quality of the stamped product. In this work, punch samples were machined after heat treatment by milling and turning strategies in super finish processes and part of the punches were submitted either to plasma nitriding or nitrocarburizing treatment before the experiments using hot stamping of washers, which were made in two stages. Based on roughness results, for non-treated punches, most of the milled punches presented more intense surface damage than turned punches after hot stamping process, possibly due to the marks left by machining processes, affecting mechanical obstacles to wear evolution and lubricant retention on punch surface. For nitrided punches, surface damage was less intense than it was on non-treated punches. Parallel contours strategy and turning upward strategy presented less intense surface damage after the hot stamping process. For nitrocarburized punches, surface damage was less intense than it was to non-treated punches, mainly for milling strategies. SEM images of nitrided and nitrocarburized punches suggested alveolar corrosion occurrence during hot stamping process for circular upward strategy.

The surfaces of molds and dies need to present a good quality because their roughness profiles are transferred to either cast or formed products. Dies and molds are frequently made of complex surfaces, and consequently, an adequate milling strategy is important to result in a proper workpiece surface. To evaluate the adequacy of a surface to be used as forming tool involves the use of roughness parameters like Sa, Ssk, Sku, Sp and Sv. These parameters influence some surface properties like wear resistance and lubrication capacity. In this work, different tool paths of milling and turning processes were chosen to machine a typical spherical surface used as die (punch) of hot stamping, in order to analyze the surface parameters Sa, Ssk, Sku, Sp and Sv of hardened steel samples. The used milling strategies were circular (upward and downward), radial (upward and downward), parallel contours and spiral (upward). Punches machined by all strategies were submitted to thermochemical treatments, plasma nitriding and nitrocarburizing Tenifer® process. The cited roughness parameters were measured in both moments, before and after the thermochemical treatments. There was similarity between milled and turned results, and thermochemical treatments presented significant influence on measured surface parameters. Machining marks were smoothed by thermochemical treatments which altered surface parameters. Thermochemical treatments effects were affected by the combination of machining marks and micro-burrs from machining processes. All tests resulted in Sku parameter either close or above 3. At 45° position of the workpiece, plasma nitriding tended to decrease roughness Sa, Sp and Sv values and present positive values of parameter Ssk. Nitrocarburizing process tended to increase roughness Sa, Sp and Sv values and present negative values of parameter Ssk, while not treated samples presented positive and negative Ssk values, depending on the machining strategy.

A simple and widely used additive manufacturing technique for polymeric materials is fused filament fabrication (FFF). In the semi-solid state, metallic materials may show rheological features comparable to those of polymers. Thus, they can be processed accordingly. The use of biodegradable Mg-based materials is an interesting approach to avoid removal surgeries and release of toxic corrosion products and wear debris. Therefore, in this study, the FFF technique was applied using a biodegradable Mg-Zn alloy in the semi-solid state. Some preliminary compositions were investigated through thermodynamic simulations to verify their compatibility with the process. Among them, Mg-38Zn was selected to be experimentally evaluated. Metallic filaments were produced via hot extrusion, which also aided in obtaining a globular microstructure in the semi-solid state. FFF was performed at 420 °C without any obstruction at the nozzle channel, which allowed the production of sound parts with acceptable welding between the deposited layers. This indicated that this technique (termed as “3D thixo-printing”) provides a promising additive manufacturing route to produce biodegradable Mg-based implants.

The present paper presents an experimental investigation of the mechanical behavior of HSLA350/440 and DP350/600 through uniaxial tensile tests, covering temperatures from 30 degrees C to 800 degrees C, and strain rates from 0.035 s(-1) to 1.35 s(-1) encompassing several conditions for the motor vehicle parts manufacturing process. Experimental data were analyzed and tensile flow curves were plotted. Yield strength (YS), ultimate tensile strength (UTS), and total elongation (EL) were determined. A severe reduction of formability was found at 600 degrees C for both materials. At 800 degrees C, the UTS was dramatically reduced to around 100 MPa for both materials. No benefit was detected for HSLA350/440 in hot working. On the other hand, the EL of DP350/600 had a straight increase at 800 degrees C according to the strain rate. The Hensel-Spittel coefficients were calibrated for experimental data to represent the materials in a finite element (FE) code in order to predict the springback. Experimental deep drawing operations were performed, and the results showed good agreement with the simulations. As a result, the calibrated Hensel-Spittel constitutive equation can predict the mechanical behavior of HSLA350/440 and DP350/600 through simulations in a wide range of temperatures and strain rates.

Present work examines and validates the novel numerical scheme to calculate the velocity, stress, strain, pressure and strain rate fields of metal plastic flow in direct extrusion processes by employing the finite volume method, FVM. Traditionally, the classical methods such as the upper-bound, slab, slip-line and more recently the Finite Element Method have been largely applied in metal extrusion analysis. However, recently the FVM has been applied and published by the authors for analysis of metal plastic flow, concluding that direct extrusion of metals could be mathematically modelled by the plastic flow formulation similar to an incompressible non-linear viscous fluid. Tannehill et al. suggested that viscous fluid flow can be numerically simulated by FVM, obeying the mass, momentum and energy conservation equations and boundary conditions. Hence, the governing equations of metal plastic flow in Euler approach were discretized by FVM, using the Explicit MacCormack Method in structured, fixed and collocated mesh. SIMPLE method was applied to attain the necessary pressure-velocity coupling. These new numerical scheme was applied to the analysis of direct hot extrusion process of Al 6351 and Al 6060 aluminium alloys. The velocity and other variables fields achieved fast convergence and a good agreement with experimental results from visioplasticity tests by the grid stripe pattern technique and Forge 2008 software. The MacCormack Method applied to metal extrusion revealed consistent results without the need of artificial viscosity as required by the compressible fluid flow simulation approaches. Therefore, present numerical results confirm that FVM with MacCormack method together with Euler formulation approach and SIMPLE method can be applied satisfactory in the solution of metal forming processes.

Forjamento é um dos processos mais utilizados em conformação mecânica, sendo muito estudado em busca de melhorias do processo produtivo.Nesse contexto há o desenvolvimento do forjamento

Computational numerical simulation has been largely applied in the design and analysis of metal forming processes.Extrusion is one of the main forming processes largely applied in the manufacturing of metallic products or parts.Historically, the Finite Element Method (FEM) has been applied for decades in metal extrusion analysis.However, recently in the academy, there is a trend to use the Finite Volume Method (FVM), because literature suggests that metal flow by extrusion can be analyzed by the flow formulation.Thus, metal flow can be modelled as an incompressible viscous fluid.The MacCormack Method is commonly used to simulate compressible fluid flow by the FVM.However, metal extrusion does not present state equations to calculate the pressure, and therefore, a velocity-pressure coupling method is necessary to obtain consistent velocity and pressure fields.This work proposes a new numerical scheme to obtain information about metal flow in the extrusion process along the steady state.The governing equations were discretized by FVM, using the Explicit MacCormack Method to structured and collocated mesh.The SIMPLE Method was applied to attain pressure-velocity coupling.This new numerical scheme was applied to analyze forward extrusion of lead.The metal extrusion velocity fields were calculated with a fast convergence and presented a good agreement with analytical and experimental results obtained from literature.

Hot stamping has been widely studied and increasingly applied in the automotive industry. This process is characterized by its ability to stamp high strength steels, yielding products with high mechanical strength, thus reducing the weight of stamped components and therefore the vehicles weight. It also demands less energy because steel sheets can be heated by induction, more efficient than electric furnaces. With controlled thinning, it is possible to manufacture thinner stamped parts with high mechanical strength, therefore it is necessary to know the formability limits to prevent failure and achieve the largest possible thickness reduction. In this work the hot formability of DIN 27MnCrB5 steel sheets 4 mm thick, under thinning conditibns was evaluated by numerical simulation with the finite element (FEM) software Forge2008. Tensile tests were carried out at 500, 600, 700, and 800 degrees C and with strain rates from 0.1 to 4 s(-1). With the results of tensile tests, it was possible to calculate Hensel-Spittel coefficients to model the steel sheet and simulate the hot Nakazima test to evaluate the highest dome which could be formed without failure risks caused by sheet thinning. Simulation results obtained with specimens 200 mm long and 125, 150 or 200 mm wide that were stamped at 930 degrees C, showed the radial position and dome height associated to plastic instability as well provided the thickness distribution along the specimen. The numerical results were compared to experimental tests and showed a good agreement in terms of failure initiation and localization. As a result, a new numerical and experimental strategy was elaborated to define the hot formability based on the plastic instability and necking localization as a function of stamping temperature and blank dimensions. This strategy proved to be useful to define the safe formability region and therefore the larger thickness reduction that can be done during hot stamping to reduce vehicular components weight and to avoid cracks and failures usually observed in components like clutch covers. (C) 2015 Elsevier B.V. All rights reserved.

Hot stamping of high strength steels has been continuously developed in the automotive industry to improve mechanical properties and surface quality of stamped components. One of the main challenges faced by researchers and technicians is to improve stamping dies lifetime by reducing the wear caused by high pressures and temperatures present during the process. This paper analyzes the laser texturing of hot stamping dies and discusses how different surfaces textures influence the lubrication and wear mechanisms. To this purpose, experimental tests and numerical simulation were carried out to define the die region to be texturized and to characterize the textured surface topography before and after hot stamping tests with a 3D surface profilometer and scanning electron microscopy. Results showed that laser texturing influences the lubrication at the interface die-hot sheet and improves die lifetime. In this work, the best texture presented dimples with the highest diameter, depth, and spacing, with the surface topography and dimples morphology practically preserved after the hot stamping tests.

Physical simulation of friction stir welding (FSW) by means of hot torsion tests was performed on UNS S32205 duplex stainless steel. A thermomechanical simulator Gleeble 3800® with a custom-built liquid nitrogen cooling system was employed to reproduce the thermal cycle measured during FSW and carry out the torsion tests. Microstructures were compared by means of light optical microscopy and electron backscatter diffraction. True strain and strain rate were calculated by numerical simulation of the torsion tests. Thermomechanically affected zone (TMAZ) was reproduced at peak temperature of 1303 K (1030 °C), rotational speeds of 52.4 rad s−1 (500 rpm) and 74.5 rad s−1 (750 rpm), and 0.5 to 0.75 revolutions, which represent strain rate between 10 and 16 s−1 and true strain between 0.5 and 0.8. Strong grain refinement, similar to the one observed in the stir zone (SZ), was attained at peak temperature of 1403 K (1130 °C), rotational speed of 74.5 rad s−1 (750 rpm), and 1.2 revolution, which represent strain rate of 19 s−1 and true strain of 1.3. Continuous dynamic recrystallization in ferrite and dynamic recrystallization in austenite were observed in the TMAZ simulation. At higher temperature, dynamic recovery of austenite was also observed.

Nowadays, the finite element method is still the first choice of researchers in metal extrusion analysis. However, recent published papers have also supported that metal plastic flow can be modelled by the flow formulation, employing the finite volume method. In this work, the numerical scheme presented by Martins et al. [16] based on finite volume method together with the explicit MacCormack numerical method, was used to analyse aluminum axisymmetric direct extrusion in a 90° die. A structured, fixed and collocated mesh and numerical convergence based on the SIMPLE method were employed to attain pressure-velocity coupling. The main goal of present numerical scheme was to obtain the axial and radial velocities and pressure distributions. From these results, it was possible to obtain and identify the dead zone inside the billet deformation region in direct extrusion of aluminum in a 90° die. The field variables results shown in present work had good agreement when compared with those from literature.

One of the methods used for metal forming is forging, a process in which the raw material is plastically deformed in generalized intermittent cycles. The main purpose of this project is the determination of a sequence of movements of hydraulic actuators used in a multidirectional press that allows obtaining forged products with complex geometry and low production of flash. To do this, a programming of logical control for the hydraulic circuit that performs a technique called incremental forging is being developed.

A novel numerical approach to calculate strain rate, stress and velocity fields of axisymmetric hot extrusion process is presented and discussed. Traditionally, metal forming analysis has been performed by upper-bound, slab, slip-line and Finite Element (FEM) methods. However, Finite Volume Method (FVM) has been recently developed for metal plastic flow analysis. Hence, metal extrusion was modelled by flow formulation. Governing equations were discretized by FVM, using Explicit MacCormack Method in structured and collocated mesh. SIMPLE method was applied to attain necessary pressure-velocity coupling. This scheme was applied to hot extrusion of aluminium alloy 6351. Numerical results of velocity field from present FVM produced consistent and good agreement with FEM results, employing FORGE 2008. Present results also suggest that MacCormack and SIMPLE methods can be applied in the solution of metal forming processes.

The following research project has as main objective the conception and construction of an equipment for incremental sheet metal forming using a hydraulic system, which will allow to substitute the most common process with CNCs machines, that shows some limitations for not being specific designed for this process.The new system is hydraulic, controlled by a Programmable Logic Controller, responsible to insure its movement's accuracy.

Microalloyed steels are gaining increasing importance as substitutions for carbon steels because they possess higher mechanical properties, such as strength and toughness after hot forging, without a need for post-deformation heat treatment. To increase machinability, sulfur is added to microalloyed steels to facilitate chip removal, increase productivity, and enhance the life of cutting tools. Otherwise, the sulfide particles that benefit machinability may cause a significant loss in hot workability. Therefore, it is important to understand the effect of initial grain size, phase constituents, and inclusion content on flow stresses during hot working in order to establish ideal processing conditions, which prevent the formation of defects and simultaneously improve mechanical properties. The aim of the current study is to construct processing maps to evaluate the hot workability of microalloyed steels DIN 38MnSiVS5 and 0.39C1.47Mn in order to define the constitutive behavior of both steels under hot working and identify the safe regions for metalworking. The processing maps for both steels showed a region of instability at temperatures between 1100 and 1150 °C and the highest strain rates (namely, 10.0 and 30.0 s−1) that should be avoided. Cracks were found in the sample of 0.39C1.47Mn steel and voids were found in the central region in the DIN 38MnSiVS5 steel. These defects might be caused by MnS inclusions and are probably the cause of instability. Therefore, it can be concluded that a higher sulfur content has a negative effect on workability, and might be the cause of instability under some processing conditions.

Hot forging is a metal forming process widely used in the industry. Among the many advantages are the possibility of severe plastic deformation and the improvement of mechanical properties, leading to the continued development of forging for industrial applications. The conventional hot forging of complex geometry components is performed in several steps, what is favorable to initiate, or propagate defects formed in the early steps due to the deformation path. In order to obtain products in a single processing step, this research aimed the development of an innovative multi-directional forging process. The finite element method was used to simulate the manufacturing of a 38MnSiVS5 steel connecting rod to preview the distributions of temperature, equivalent strain and von Mises stress in the forged product, as well as the formation of defects. Billets with the same volume and different lengths and widths were simulated to achieve the best material flow, which avoids fold and other forging defects, and leads to the complete flashless filling of the die. The simulation results made possible to know the proper billet geometry and the best friction condition for the proposed process.

Resumo. O processo de conformacao denominado Laminacao Transversal com Cunha, tambem conhecida como Cross Wedge Rolling, tem se destacado na industria pela sua flexibilidade, produtividade e economia de material, porem pode apresentar o problema do defeito interno que inviabiliza a utilizacao dos seus produtos. Esse estudo tende a demonstrar atraves de simulacoes por metodos numericos do processo de laminacao transversal com cunha, como as falhas internas de um material – vazios e inclusoes – vem a evoluirem para defeitos de grandes proporcoes, assim se desenvolveu diferentes modelos de elementos finitos no software comercial Abaqus ® versao 6.9-2. Foram simulados modelos bidimensionais com vazios internos de diferentes tamanhos e disposicoes. Posteriormente, foram simulados modelos com inclusoes circulares, quadraticas e triangulares, a fim de avaliar o que essas caracteristicas influenciam no processo. E por fim, foi simulado um modelo utilizando o recurso de caracterizacao de porosidade do aco, gerando uma representacao dos locais de nucleacao e coalescencia de poros. Os modelos com vazios apresentaram elevados valores de tensao junto a suas circunferencias, sendo que esses vazios tenderam a fechar durante a deformacao, ja os modelos com inclusoes apresentaram tambem altos valores de tensao ao seu redor com uma tendencia a formacao de fissuras e o modelo com propriedades de porosidade confirmou que ha a tendencia de nucleacao e coalescencia de vazios na regiao central do tarugo.

Ti alloys are frequently used in the manufacture of femoral stems for total hip arthroplasty. Although low elastic modulus stems minimize bone stress shielding, they also may produce micromotions at the bone/implant interface, leading to excessive interfacial mechanical stress at the proximal region. This phenomenon may lead to the growth of fibrous tissues and, eventually, implant failure. To address both restrictions simultaneously, stems with adjustable rigidity may be used. Considering that the rigidity of beta Ti alloys can be controlled by heat treatments, this paper introduces a new concept for a femoral stem with a graded elastic modulus using metastable beta Ti alloy. The combination of solution heat treatment, waterquenching, and aging heat treatments allows the mechanical behavior of the metastable beta Ti alloys to be tailored and, in particular, be used to construct a graded elastic modulus femoral hip stem. The results obtained revealed that it is feasible to design biomedical implants from metastable beta Ti alloys with hybrid mechanical behavior. The specific mechanical behavior is obtained by focusing only on heat treatments. A stem with an elastic modulus varying from 65 GPa to 110 GPa was obtained. (C) 2014 Elsevier Ltd. All rights reserved.

The laminar incompressible fluid flow by computational numerical simulation often appears in numerical analysis in academic and industrial activities. In order to solve this kind of flow, it is necessary to determine the velocity and pressure fields which are the variables of Navier-Stockes equations (11,15,21). However, to solve the equations of fluid flow with losses there is no simple equation to carry out velocity and pressure coupling, hence, it is necessary to use a coupling method to obtain velocity and pressure fields consistent (1,2,3). This work deals with the presentation of a numerical method to calculate velocity and pressure fields to computational numerical simulation of laminar fluid incompressible flow with losses. The Navier-Stockes equations were discretized by the Finite Volume Method (11,15,21), using explicit MacCormack Method (21) in co-localized and structured mesh (11,15,21), where velocity and pressure coupling was made by SIMPLE method (11,21). The MacCormack method is a two-steps method (predictor-corrector) of second-order accuracy in both space and time and this method is commonly utilized in the resolution of compressible fluids prob- lems (21). The numerical results of velocity fields were obtained for bi-dimensional case and it was compared with analytical results for parallel plates.