Microhardness Profile and Residual Stresses Evaluation in a Shot Peened SAE 5160H Steel

Shot peening (SP) is a surface cold hardening process used on metals to enhance life under cyclic stress. In this case, SP was applied to SAE5160H samples of steel quenched tempered in oil at 460 °C used for leaf springs. This study shows the residual surface stresses measured through X-ray diffraction (XRD) and the microhardness variation through the perpendicular-to-the-peened surface using a combination of metallographic preparation and Vickers microhardness (HVN). This combination of techniques makes possible measuring the SP effect in perpendicular-to-the-treated surface. A residual stress of -365.8 ± 78 MPa measured by XRD and a maximum microhardness of 525± at 92.7 HVN on the surface were obtained for the SP material. Alternatively, an average of 54.2 ± 54.3 MPa residual stress measured by XRD and 433 ± 39.5 HVN were obtained for the As-it-is samples. In addition, corrosion electrochemical potential tests showed that SP increases the corrosion potential, which makes this process undesirable if the SP component is exposed to aggressive environments. Moreover, the As-it-is samples presented not statistically significant HVN difference in the measured points. The combination of experimental techniques allows estimating hardness change in perpendicular-to-the treated surface separated by as little as 10 µm but with a simpler specimen preparation than other techniques such as XRD or strain gauges. Such a combination can be an alternative for estimating residual stresses through depth

Diseño óptimo de resortes tipo ballesta para la suspensión de un vehículo comercial considerando las condiciones dinámicas.

Los resortes tipo ballesta son tradicionales y ampliamente utilizados en vehículos terrestres, estos deben su vigencia a la capacidad de carga, bajos costos de manufactura y mantenimiento. Para dar un valor agregado a este tipo de suspensión se simula su comportamiento estático y dinámico así como el de otros componentes relacionados con el fin de observar los efectos de la precarga no-lineal, las grandes deflexiones, materiales compuestos y el torque de sujeción. El vehículo de pruebas es un camión de carga con transmisión 6x6. El comportamiento dinámico del vehículo es simulado mediante el método MBS+FEM en un entorno transitorio no-lineal implícito a través del solver APDL de ANSYS. La simulación es parametrizada para realizar un Diseño de Experimentos (DOE) y determinar las características óptimas que debe tener el resorte, dependiendo también de la carga que se transporta. Posteriormente se analiza el resorte en detalle teniendo en cuenta las cargas resultantes aplicando el método de conteo Rainflow con el fin de predecir la fatiga de este elemento. Como resultado se obtiene una metodología de diseño que integra condiciones globales y locales para asegurar el óptimo rendimiento del producto.Abstract. Leaf spring suspensions are traditional and widely used in terrestrial vehicles; these owe their vigency to high load capacity, low manufacturing cost and maintenance. To give more value added to this type of suspension, simulate the static and dynamic behavior likewise another related components in order to observe the non-linear preload effects, large deflections, composites materials and bolt tightening. The test vehicle is a commercial truck with 6x6 transmissions. Dynamic behavior of vehicle is simulated through MBS+FEM method on implicit no-linear transient environment with ANSYS APDL solver. Simulation is parametrized in order to carry out a Design of Experiment (DOE) and determine the optimum characteristics that spring should have. Depends also of the vehicle payload. After that analyze the spring in high level of detail taking in count the resultant forces acting on it, apply Rainflow Counting Method, the objective is to predict durability of this element. As a result obtain a design methodology that integrates the global and local conditions to assurance the optimum performance of the product.Maestrí

Estudio del Comportamiento Bajo Carga de un Chasis para Transporte de Pasajeros por Medio de la Tecnologia de Elementos Finitos en la Empresa Equitel Cumandes S.A.

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