ANÁLISE EXPERIMENTAL DE ESTAMPABILIDADE DA CHAPA DE AÇO ASTM A653 DURANTE O PROCESSO DE ESTAMPAGEM INCREMENTAL POR PONTO ÚNICO E AVALIAÇÃO DA RUGOSIDADE IMPRESSA NA SUPERFÍCIE CONFORMADA

This study aims to evaluate the behavior of ASTM A653 CS-A G90 steel in the process of Incremental Sheet Forming – ISF, based on the following parameters: diameter of the tool (Dt in mm) and the vertical step size between consecutive contours (∆z in mm). The experiments were based on a variation of the ISF process, called Single Point Incremental Forming - SPIF. In this study, seventeen tests were conducted using a punching tool with diameters (Dt ) of 5, 6 and 8 mm and vertical steps (∆z) of 0.4, 0.6 and 0.8 mm, intending to evaluate the true strain to the ISF process and the surface finishing measured by roughness parameter (Rz). Whereas, for the execution of practical testing, the resources used were a CNCmachining center with three axes, tools for incremental forming and a sheet-press device. As a result, greater depths were achieved using an incremental step of 0.4 mm. In additional tests, it came to attention that the diameter of the tool was also an important parameter when it is desired to increase the formability and greater depths are obtained when using small diameters. It can be observed yet, there is a tendency to increase the roughness parameter Rz when using greater vertical steps ∆z

Study of Friction and Wear Effects in Aluminum Parts Manufactured via Single Point Incremental Forming Process Using Petroleum and Vegetable Oil-Based Lubricants

This paper focuses on studying how mineral oil, sunflower, soybean, and corn lubricants influence friction and wear effects during the manufacturing of aluminum parts via the single point incremental forming (SPIF) process. To identify how friction, surface roughness, and wear change during the SPIF of aluminum parts, Stribeck curves were plotted as a function of the SPIF process parameters such as vertical step size, wall angle, and tool tip semi-spherical diameter. Furthermore, lubricant effects on the surface of the formed parts are examined by energy dispersive spectroscopy (EDS) and scanning electron microscope (SEM) images, the Alicona optical 3D measurement system, and Fourier-transform infrared spectroscopy (FTIR). Results show that during the SPIF process of the metallic specimens, soybean and corn oils attained the highest friction, along forces, roughness, and wear values. Based on the surface roughness measurements, it can be observed that soybean oil produces the worst surface roughness finish in the direction perpendicular to the tool passes (Ra =1.45 μm) considering a vertical step size of 0.25 mm with a 5 mm tool tip diameter. These findings are confirmed through plotting SPIFed Stribeck curves for the soybean and corn oils that show small hydrodynamic span regime changes for an increasing sample step-size forming process. This article elucidates the effects caused by mineral and vegetable oils on the surface of aluminum parts produced as a function of Single Point Incremental Sheet Forming process parameters.

Surface Finish Analysis in Single Point Incremental Sheet Forming of Rib-Stiffened 2024-T3 and 7075-T6 Alclad Aluminium Alloy Panels

The article presents the results of the analysis of the interactions between the single point incremental forming (SPIF) process parameters and the main roughness parameters of stiffened ribs fabricated in Alclad aluminium alloy panels. EN AW-7075-T6 and EN AW-2024-T3 Alclad aluminium alloy sheets were used as the research material. Panels with longitudinal ribs were produced with different values of incremental vertical step size and tool rotational speed. Alclad is formed of high-purity aluminium surface layers metallurgically bonded to aluminium alloy core material. The quality of the surface roughness and unbroken Alclad are key problems in SPIF of Alclad sheets destined for aerospace applications. The interactions between the SPIF process parameters and the main roughness parameters of the stiffened ribs were determined. The influence of forming parameters on average roughness Sa and the 10-point peak–valley surface roughness Sz was determined using artificial neural networks. The greater the value of the incremental vertical step size, the more prominent the ridges found in the inner surface of stiffened ribs, especially in the case of both Alclad aluminium alloy sheets. The predictive models of ANNs for the Sa and the Sz were characterised by performance measures with R2 values lying between 0.657 and 0.979. A different character of change in surface roughness was found for sheets covered with and not covered with a soft layer of technically pure aluminium. In the case of Alclad sheets, increasing the value of the incremental vertical step size increases the value of the surface roughness parameters Sa and Sz. In the case of the sheets not covered by Alclad, reduction of the tool rotational speed increases the Sz parameter and decreases the Sa parameter. An obvious increase in the Sz parameter was observed with an increase in the incremental vertical step size.

Patterns of recent deformation of the western Maracaibo block, northern Colombia and western Venezuela, based on integration of geomorphic indices with regional geology

The Maracaibo block is a triangular, continental tectonic terrane that includes two isolated Andean ranges of northern Colombia and western Venezuela: the Sierra de Santa Marta Massif (SSMM; maximum elevation 5700 m) in the west and the Perija Range (PR; 3600 m) to the east. The Cesar-Rancheria Basin (CRB) is an intermontane basin that separates the two ranges. To establish patterns of recent deformation of this elevated region and to infer its tectonic mechanism, we have integrated the following results: (1) analysis of 350 stream profiles and calculations of geomorphic indices, including stream length-gradient (SL) index, ratio of valley-floor width to valley height (VF), and hypsometry curves for 20 watersheds in both ranges and (2) interpretation of three seismic reflection profiles within the CRB and adjacent areas. We determine that the northeastern part of the SSMM is tectonically quiescent based on its concave stream profiles, low geomorphic indices, and few vertical-step knickpoints. In comparison, we find that the central, southern, and eastern parts of the SSMM show tectonic uplift and recent fault control based on slope-break knickpoints and values in steepness and geomorphic indices with possible additional controls from lithologies of varying erosional resistance. Correlation among steepness, SL indices, slope-break knickpoints, and topographic elevations of the SSMM and central PR all indicate recent deformation of these areas. We use seismic reflection profiles from the eastern part of the CRB to confirm the existence of late Quaternary faulting and folding in these geomorphologically active areas. We think that active, southeastward shallow (approximately 10°–15°) subduction of the Caribbean plate along the base of the South American continental crust focuses recent deformation within the southern and eastern SSMM. The central PR and eastern CRB are also controlled by active strike-slip faults.

On the Connection Between Step Approximations and Depth-Averaged Models for Wave Scattering by Variable Bathymetry

Summary Two popular and computationally inexpensive class of methods for approximating the propagation of surface waves over two-dimensional variable bathymetry are ‘step approximations’ and ‘depth-averaged models’. In the former, the bathymetry is discretised into short sections of constant depth connected by vertical steps. Scattering across the bathymetry is calculated from the product of $2 \times 2$ transfer matrices whose entries encode scattering properties at each vertical step taken in isolation from all others. In the latter, a separable depth dependence is assumed in the underlying velocity field and a vertical averaging process is implemented leading to a second-order ordinary differential equation (ODE). In this article, the step approximation is revisited and shown to be equivalent to an ODE describing a depth-averaged model in the limit of zero-step length. The ODE depends on how the solution to the canonical vertical step problem is approximated. If a shallow water approximation is used, then the well-known linear shallow water equation results. If a plane-wave variational approximation is used, then a new variant of the mild-slope equations is recovered.

Quantum Mechanical Reflection and Transmission Coefficients for a Particle through a OneDimensional Vertical Step Potential

In this paper, we illustrate an application of the Laplace transformation for finding the quantum mechanical Reflection and Transmission coefficients for a particle through a one-dimensional vertical step potential. Quantum mechanics is one of the branches of physics in which the physical problems are solved by algebraic and analytic methods. By applying the Laplace transformation, we can find the quantum mechanical Reflection and Transmission coefficients for a particle through a one-dimensional vertical step potential. Generally, the Laplace transformation has been applied in different areas of science and engineering and makes it easier to solve the problems inengineering applications. It is a mathematical tool which has been put to use for solving the differential equations without finding their general solutions. It has applications in nearly all science and engineering disciplines like analysis of electrical circuits, heat and mass transfer, fluid dynamics, nuclear physics, process controls, quantum mechanical problems,etc.