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In this study, a novel method for determining stresses in the torsion problems of laminated composite trimetallic and bimetallic bars was developed and evaluated via experimental and numerical analyses. The objective of this method is to transform a real transversal section of a model for a laminated composite bar into a hypothetical virtual section that is homogenous and isotropic. An analogy with the transformed-section method for solving composite beams under flexion was conducted. The shear stresses (maximum on external surfaces and interfaces) in laminated composite bars were undergoing torsion. Isotropic symmetric and asymmetric laminated composite bars were examined analytically, and the results of their respective experimental and numerical tests were analyzed. The proposed method exhibits differences between 2 % and 12 % compared with the experimental results and between 2 % and 10 % compared with the results obtained using the finite element method.

This article introduces a new kinematic modeling method used to analyze coupled rigid multibody movements. The method was applied to the study of a 5R planar parallel mechanism’s kinematics and consists of analyzing two fixed configurations of the mechanism to systematize the rotational relationships between the two structures. Mathematical models were developed using complex numbers. The inverse kinematic problem was modeled as a system of eight nonlinear equations and eight unknowns, which was solved with Newton-Raphson’s method. Subsequently, with the inverse problem model, a numerical database related to the mechanism configurations, including singular positions, was generated to train a multilayer neural network. The Levenberg-Marquardt algorithm was used for network training. Finally, an interpolated linear path was used to understand the efficiency of the trained network.

This paper presents a methodological scheme to obtain the maximum benefit in occupational health by attending to psychosocial risk factors in a company. This scheme is based on selecting an optimal subset of psychosocial risk factors, considering the departments’ budget in a company as problem constraints. This methodology can be summarized in three steps: First, psychosocial risk factors in the company are identified and weighted, applying several instruments recommended by business regulations. Next, a mathematical model is built using the identified psychosocial risk factors information and the company budget for risk factors attention. This model represents the psychosocial risk optimization problem as a Multidimensional Knapsack Problem (MKP). Finally, since Multidimensional Knapsack Problem is NP-hard, one simulated annealing algorithm is applied to find a near-optimal subset of factors maximizing the psychosocial risk care level. This subset is according to the budgets assigned for each of the company’s departments. The proposed methodology is detailed using a case of study, and thirty instances of the Multidimensional Knapsack Problem are tested, and the results are interpreted under psychosocial risk problems to evaluate the simulated annealing algorithm’s performance (efficiency and efficacy) in solving these optimization problems. This evaluation shows that the proposed methodology can be used for the attention of psychosocial risk factors in real companies’ cases.

Cuando un elemento estructural es fabricado con un material compuesto laminado (MCL) y se somete a cambios de temperatura, se generan esfuerzos termicos intralaminares. Los esfuerzos termicos intralaminares se presentan debido a las diferencias en los coeficientes de expansion termica y a las propiedades elasticas de las capas que componen al MCL. Es posible que una combinacion de esfuerzos intralaminares y esfuerzos mecanicos puedan producir fallas por separacion en las capas de los MCL (delaminacion). En este articulo se presenta un modelo analitico con el cual se calculan esfuerzos termicos globales e intralaminares producidos por cambios de temperatura inducidos en MCL metalicos, simetricos y sin restricciones en las fronteras. El modelo es alimentado por datos de deformacion obtenidos por galgas extensometricas colocadas en la frontera del MCL. El modelo puede ser utilizado en la determinacion de esfuerzos intralaminares y globales considerando restricciones o cargas en la frontera, solo si el problema es de esfuerzos planos. El modelo fue desarrollado haciendo una analogia al modelo analitico desarrollado en [1], el cual consiste en calcular esfuerzos intralaminares y globales que se generan por la diferencia entre las constantes elasticas de los materiales que componen un MCL sometido a tension simple. El modelo propuesto se fundamenta en la teoria de la elasticidad lineal, en la teoria clasica de laminas y en el principio de superposicion. Con el modelo y mediante un arreglo de pruebas experimentales, se pueden calcular los coeficientes de expansion termica (CET) de cada una de las capas. Finalmente, se realizaron pruebas experimentales de validacion las cuales mostraron que el modelo propuesto es confiable y consistente. Palabras clave: Esfuerzo Termico, Esfuerzo Intralaminar, Coeficiente de Expansion Termica, Materiales Compuestos.

This paper presents Acosta’s (Acosta et al., 2016) constitutive analytical model, which is used for the mechanical analysis of intralaminar and global stresses in symmetrical laminated composite materials subject to axial load. The model is composed of both a laminated constitutive model and a constitutive model for each layer. The model and its method of analysis were used to obtain the elastic properties of the core of a symmetric metal sandwich plate and the properties of a non-symmetric bimetallic material. The model is fed with information from strain gages, which register deformations at the boundary of the compounds analyzed under axial load. The results obtained showed that the proposed method is simple and reliable. Keywords: Elastic properties, Laminated compounds, Sandwich material, Intralaminar stress

The origin of an automotive structural mechanical failure can be originated by diverse causes, due for example to the structural geometry, the materials of manufacture, the processes of manufacture and the mechanical loads, that appear during the time of service for the that were designed, among other causes. The determination of the mechanical causes that provoke such failures is not a simple task, so it is recommended to apply systematic methods that allow identifying and characterizing them efficiently. Currently, there are experimental and computational tools, which can be used of an integral way to assess failures, locate them and give them a practical solution. In this article an efficient method is presented, which was used to identify and quantify the causes that originated mechanical structural failures (generated by cracks) in a bus. Through a numerical method, was searched for and found the solution to the problem, which was implemented and evaluated. The method integrates experimental and numerical tools for the analysis of stresses and deformations (photoelasticity and electrical extensometry) required for the study of failures. Static tests (torsion and flexion) and braking, curving and travel tests were carried out, with the purpose of obtaining data of stresses and strains that would allow evaluating the mechanical conditions of the bus. The load conditions of the tests were a Gross Vehicle Weight (PBV) and PBV + 20%. To carry out the road tests, only the information of the edges and potholes was considered, since they turned out to be the events that caused the highest levels of stress. The study was carried out on a prototype bus, which did not present structural mechanical failures. The case study presented in this paper refers to finding the causes and the solution to a problem of a failure by a fissure located on the floor of a bus. Finally, the results obtained show the efficiency of the proposed analysis method as well as the integration of the experimental and numerical tools used, in a systematic and integral way identifying the causes that originated a failure in the structure of the bus. Keywords: Mechanical failures, experimental methods, numerical methods for stress analysis, automotive structures.

The failures, unexpected and catastrophic, are presented in large mechanical systems, specifically, in the electric power generation. The development of new methodologies of analysis and research to evaluate and calculate useful life must be proposed. In this work, an analytical-experimental novel methodology was developed using laws of similarity and models at the scale of prototypes, parts or mechanical components of any system. The methodology developed in the dynamic study of steam turbine blades was applied to calculate their stresses, deformations and the prediction of their useful life in mechanical fatigue conditions. The analytic-experimental and numerical results showed a relative error of less than 3,16% for both models. The new methodology was validated with these results. The use of scale models with the application of similarity laws will be of help in the analysis of failures where due to the size or high costs, real systems cannot be analyzed. Keywords: scale models, experimental analysis, deformations, similarity laws, useful life, mechanical fatigue

Background and Purpose: The challenges imposed by today’s societies, which demand products and services of quality and of greater technological complexity, require the formation of highly trained human resources, which confront the various problems that arise in industries. Reverse engineering and the direct design are applied to solve problems in companies and universities. These methods, in combination with active methodologies, provide tools that potentiate the teaching of engineering. This article presents a proposal for the definition of reverse engineering and its application, together with the direct design method, in the development of novel procedures oriented toward the teaching of engineering.

Los materiales compuestos laminados, utilizados comunmente en la industria automotriz y aeroespacial, presentan esfuerzos interlaminares e intralaminares en las capas que los constituyen cuando son sometidos a cargas externas. Estos esfuerzos son maximos en los bordes laterales causando separacion de las capas en los compuestos laminados. En este trabajo, el desarrollo de un modelo analitico con el que se evaluaron experimentalmente materiales compuestos laminados cargados axialmente es presentado. Mediante la obtencion de las deformaciones en las fronteras de forma experimental, se pueden determinan los valores de los esfuerzos intralaminares. El modelo esta integrado por: a) Un modelo constitutivo laminado y b) Modelos constitutivos para cada capa. Para su evaluacion, se obtuvieron experimentalmente las deformaciones en las fronteras y los esfuerzos intralaminares, en probetas con capas metalicas y probetas con capas ortotropicas, ambas sometidas a cargas axiales. Se instrumentaron con galgas extensometricas algunos puntos especificos localizados en las fronteras de los compuestos y se realizaron pruebas a tension simple. Los resultados obtenidos muestran que el modelo obtenido es confiable y representativo, y se pueden determinar los esfuerzos intralaminares y globales. Palabras clave: Materiales compuestos laminados, Esfuerzos Intralaminares, Metodos Experimentales, Carga Axial.

In the present chapter, we have developed mathematical modeling and analysis by finite element (FEA) process of turning with chip detachment; the study incorporated the dynamic and structural cutting orthogonal and oblique mathematical models in three dimensions (3D) and with incorporating thermal mesh structural static fluid for your simulation in FEA software. Validation is performed on an experimental basis by record temperatures and mediated the release of chip in the process of turning with octagonal and oblique cut. With the simulation are determined variables important to optimize; these are orthogonal and oblique cutting: cutting speed, cutting depth, and angle cutting, presenting a variation of 4–8% with respect to the experimental values. In this process, it was determined that cutting temperature presents a value means of 132 °C and a maximum of 147 °C and a minimum of 115–14 °C cutting angle and a forward speed of a 0.1466 speed m/s temperature-optimized cutting. In the process of chip detachment are decisive values for temperature, speed, depth, and angle of cut according to a previous simulation incorporating the models mentioned above.

En este artículo se presenta un código en el software ATP que permite simular y reproducir las señales transitorias de tensión debidas a la conexión de un banco de capacitores en la barra de una subestación de potencia de 85 kV. De una manera simple y resumida se muestra cómo calcular y representar la información fundamental de campo para el proceso de modelado y simulación en el software, para que el lector pueda llevar a cabo simulaciones de la red sin invertir tiempo adicional en cuestiones relacionadas con interpretación de manuales de usuario.

Los esfuerzos residuales son cargas internas que se producen en elementos y estructuras mecanicas como resultado de los procesos de manufactura con los que se fabrican. Estos esfuerzos reducen la capacidad de carga de los elementos estructurales en aquellos casos en que son relevantes y se suman a los esfuerzos que se generan por la aplicacion de solicitaciones mecanicas. La vida util de una estructura puede ser mucho mas corta de lo esperando si en la etapa de diseno los esfuerzos residuales no fueron considerados. Uno de los procesos de fabricacion que se usa con mucha frecuencia en las aplicaciones industriales y que genera altos esfuerzos residuales, es la union por soldadura. En este articulo se presenta una metodologia sistematica experimental para medir y analizar los niveles de esfuerzos residuales que se producen en la union por soldadura de arco electrico en placas de acero inoxidable AISI 347 de 3 pulgadas de espesor. Para conocer el estado de esfuerzos residuales fueron analizados cuatro puntos de interes cercanos a las soldaduras, los cuales fueron instrumentados con extensometros electricos de resistencia variable, y se utilizo la tecnica del barreno ciego para el estudio de los esfuerzos residuales. Los resultados experimentales mostraron que algunos puntos alcanzaron niveles mayores al esfuerzo de cedencia del material de la placa analizada.