Carolina Álvarez-Caldas

Educational software to design shafts and analyze them by FEM

In this article, an educational computer application to dimension shafts is presented. Safety factors according to several classic theories can be obtained by indicating shaft dimensions and particular discontinuities, as grooves or holes. Specifying the desired security factor, necessary dimensions can be calculated. One of the advantages of the educational software developed is that text files created by it can be directly imported to the FEM software ANSYS so as to analyze stress distribution of the shaft.

Head injury criterion: the best way to evaluate head damage?

During the design and construction of a new car model, there are a lot of important aspects that have to be taken into account. The cars designers look for a beautiful appearance, for a car as light as possible, try to reduce the manufacture costs and times and, of course, want to guarantee that their car is as safe as it can be. There are several criteria that allow to quantify the safety of a car. One of them, the Head Injury Criterion (also known as HIC) gives a measure of the damage that the head can suffer in case of collision. This paper presents a review of some works related to this criterion. It will be proved that the HIC has several limitations that allow to say that this criterion is clearly improvable.

Material parameters in a simulation of metal sheet stamping

Abstract The paper presents a methodology to tackle the problem of new materials, such as high-strength steels, used in industrial manufacturing. This methodology, which uses the finite element method (FEM), is based on two main ideas: determining the material properties as accurately as possible and automating the FEM simulation as much as possible. The main tool to solve these problems is an application designed to assist die stamp designers. Such an application can be used by anyone, even with no knowledge about finite elements, and does not need user participation. This fact makes the program very powerful and allows a procedure to be defined to obtain the values of the properties of an unknown material, which combines finite element simulations with real experimental results. The paper presents the developed application as well as the procedure used to determine the material properties. By combining both aspects, it is possible to simulate any stamping process, allowing the designer to obtain much information in the earlier stages of design. This paper fulfils an identified need in the manufacturing industry. In fact, the proposed application is currently being used by a manufacturer of automotive components.

Structural Validation of Railway Bogies and Wagons Using Finite Elements Tools

Abstract This article aims to contribute an integrated solution for the design and test of railway bogies, so that the demands of each new design can be validated by computing. Nowadays, official approval regulations demand experimental tests on real prototypes. Three different kinds of tests are required. Trying to substitute these tests by simulations on a finite element method (FEM) model, two main troubles appear. (1) Strain gauges used in experimental tests must be substituted by a FEM entity that provides similar results as long as official standard regulations can be applied to them. (2) Current FEM codes present several problems simulating fatigue phenomenon. In this article, a new type of finite element, called virtual strain gauge, is proposed. Results obtained by this element can be treated as experimental results, as long as they are much similar to strain gauges results than other typical FEM ones. Fatigue testing may be reduced when greater experience is acquired with virtual strain gauges. However, it will always play a key role in final test with real prototypes, pinpointing errors in materials, manufacture, and welding. This work concludes that, using virtual strain gauges, experimental tests can be drastically reduced by replacing them with FEM simulations. An example of an MSP railway bogie is analysed to illustrate theoretical results.

Is the Virtual Homologation for Pedestrian Protection Viable

One out of five deceased in traffic accidents is a pedestrian. In addition, pedestrians represent the 20 % of the hospitalized injured people. The deadliness rate of a pedestrian crash is significantly greater than for the rest of accidents. Thus, pedestrian crash is one of the more lethal traffic accidents and, consequently, pedestrians are the most vulnerable road users. Vehicle’s design can influence immensely in the risk of seriousness of the accident. Regulations are the legal instruments in order to establish if a vehicle achieves the minimum safety requirements. Nevertheless, homologation implies costly and destructive tests. This problem could be solved by simulation techniques. Analyzing the viability of a virtual homologation is the main goal of this article. After studying pedestrian crash biomechanics, virtual tests will be performed using Finite Element software (Ls-Dyna) to assess the influence of the design of vehicle and the effect of a safety system (active bonnet). Comparison between virtual tests results and real tests allows deducing if the virtual homologation for pedestrian protection is viable.

Analysis of Dynamic Systems Using Bond Graph and SIMULINK

The aim of this paper is presents an educational application, developed in MATLAB, which allows the engineering students to learn easily and quickly about dynamic systems behaviour through Bond Graph method. This application uses the SIMULINK library of MATLAB, which has proven to be an excellent choice in order to implement and solve the dynamic equations involved. Based on block diagram of SIMULINK, the different “bonds” of Bond Graph can be integrated as SIMULINK blocks in order to generate the dynamic model. As an example, a simple model are analysed through this application.

Material Characterization for FEM Simulation of Sheet Metal Stamping Processes

Sheet metal forming is an important technology in manufacturing, especially in the automotive industry. Today, engineering simulation tools based on the finite elements method are employed regularly in the design of stamping dies for sheet metal parts. However, a bad material model choice or the use of nonaccurate enough parameters can lead to imprecise simulation results. This work uses ANSYS LS-DYNA software to analyze several material models and the influence of their parameter values in FEM simulation results. The main tool to solve these problems is an application designed to assist die stamp designers. The program allows a procedure to be defined to obtain the values of the properties of an unknown material, which combines finite element simulations with real experimental results. Results obtained for the simulation of a real automotive part are analyzed and compared with the real experimental results. Parameters involved in each material model have been identified, and their influence in final results has been quantified. This is very useful to fit material properties in other simulations. This paper fulfils an identified need in the manufacturing industry. In fact, the proposed application is currently being used by a manufacturer of automotive components.

Characterization of the Noise Emissions of a Passenger Vehicle

One of the main sources of noise pollution in cities is vehicle traffic. In this paper a characterization of the noise emission of a passenger vehicle has been carried out. With this aim a representative driving route for noise emission has been defined in order to study the influence of the driver typology and vehicle type. Therefore, this investigation has been developed in three phases: Firstly, usual driving in an urban area like Madrid has been characterized with a specific driving route. In addition, several vehicle models with great presence in the existing fleet of cars have been selected. Several drivers have covered the driving route at different times of the day and previous parameters have been measured in each test in order to determine average values of behavior. Secondly, the type of vehicles and drivers influence in noise emissions has been deeply analyzed. To achieve this aim a sample of vehicles has been instrumented to obtain physical measurements of the variables that can influence the noise emission level. Positions, velocities, accelerations (longitudinal and lateral) and time have been analyzed using a GPS sensor. Parameters such as, engine speed, engine load, throttle position and engine temperature have been studied through the vehicle CAN BUS and a set of microphones has measured the emitted noise in several points of the vehicle. In order to study the ecological and safety impact in urban and interurban roads by means of the measurement of noise emissions the analysis of the driver behaviour is of paramount importance. To conclude, the previous data has been analyzed and noise equivalent levels have been identified with different test configurations.Copyright

Analysis of Dynamic Systems Using Bond Graph Method Through SIMULINK

The dynamic systems analysis, very common in engineering studies, is relatively simple when the steady state behaviour is analyzed, or when the system has few degrees of freedom. However, for complex systems, the problem can be highly complicated and the classic way to establish the behaviour equations becomes inadequate. In most of the cases, the main concern of engineering students is to establish the mathematical model that represents the dynamic behaviour of the system and how the different parameters influence the system behaviour, because the equations that represent the dynamic of the system are usually partial differential equations, whose solutions require deep mathematical knowledge that in most cases is not available for the students. The Bond Graph technique (Blundell, 1982) is extraordinarily useful to overcome these difficulties. Bond Graph is a simple and effective method to set out the differential equations of any dynamic system independently of the physical field analyzed. Bond Graph provides a common model for a wide range of systems ranging from the usual Electric, Mechanics, Hydraulic, Thermals, etc., or combinations of them. Depcik et al. (2004) compare different software and language options, which are available to build models of dynamic systems. They establish that MATLABTM and SimulinkTM might be the best choice if the teacher wishes to collaborate with students because engineering students are typically familiar with MATLAB. Some commercial software allow working directly with Bond Graph concepts as CAMP-G, TUTSIM, BONDLAB, which allow drawing the flow lines of the Bond Graph method. However, in order to the students understand the physical and mathematical concepts involved on the dynamic system, the block diagram used in Simulink allows a better compression of physical behaviour of the system. Simulink forms the core environment for Model-Based Design for creating accurate, mathematical models of physical system behaviour. The graphical block-diagram lets the user drag-and-drop predefined modelling elements, connect them together and create models of dynamic systems. These dynamic systems can be continuous-time, multi-rate, discrete-time, or virtually any combination of the three. In this chapter, we present an application, developed in Simulink library, which allows the engineering students to learn easily and quickly about dynamic systems behaviour through Bond Graph method.

Expert System for Simulation of Metal Sheet Stamping: How Automation Can Help Improving Models and Manufacturing Techniques

Nowadays, competitiveness is one of the major determining factors in global markets, forcing product developers to improve their products quality and to reduce development times. Automotive industry is a clear example of this trend and sheet metal forming, as one of the most important manufacturing processes in car manufacturing industry (Samuel, 2004), is very affected by this situation. Stamping of automotive components is a critical activity characterized by short lead times and constant technological modifications in order to improve quality and reduce manufacturing costs. The sheet metal forming process, in theory, can be viewed as relatively straightforward operation where a sheet of material is plastically deformed into a desired shape. In practice, however, variations in blank dimensions, material properties and environmental conditions make the predictability and reproducibility of a sheet metal forming process difficult (Narasimhan & Lovell, 1999). Because of this, sheet metal forming results on a process that is heavily experience based and involves trial-and error loops. The less the experience on the part geometry and material is, the more these loops are repeated. In the innovative process design procedure, however, the trial-and error loops are reduced by means of computer simulations. Virtual manufacturing of automotive stamped components by means of finite element computer analysis is a powerful tool that is capable of helping engineers to solve different technological tasks (Makinouchi, 1996, Silva, et al., 2004). The forming analyses of sheet metals are performed repeatedly in the design feasibility studies of production tooling and stamping dies (Taylor, et al., 1995). With these analyses, the formability of the sheet material part can be calculated, but it is also possible to estimate the deformed geometry of stamped parts. However, FEA (Finite Element Analysis) procedure is very time-consuming and relies much on the users’ experience. So, under the needs of reduction on design time, reduction on development cost, and reduction on parts weight (so called ‘3-reduction strategy’), there is an urgent need for more efficient and accurate method in order to improve the current design situation (Wei & Yuying, 2008).