Inverse parameter identification of elastic and inelastic constitutive material models

Formulating the complete description of a material behavior includes finding the numerical values of parameters involved in its constitutive equations [I]. Traditionally, this is based on running some experimental tests and manipulating their results in order to extract the values of these parameters [2]. This chapter presents an alternative approach, based on inverse problems, which will provide a numerical method for determining accurate material parameters. This numerical tool combines an optimization algorithm with a finite element solver giving the material response to arbitrary loading. Two numerical examples are used to demonstrate the effectiveness of the developed identification techniqu

Numerical simulation of green compacts

In the compaction process of metal powders into rigid dies, one of the most common problems is the part cracking during either the compaction stage or its ejection from die. Therefore, the finite simulation method is considered as design tool for powder metallurgy parts as well as for compaction tooling as this method allows the prediction of any kind of stresses and density distributions of the pressed compact prior to the actual tooling manufacturing activity. For this analysis, ANSYS LS-DYNA is used to facilitate the study of Geological Cap material mode

Predicting density distribution in Green compacts using finite element simulations

Finite element simulation of the rigid die compaction of metal powders can significantly help designers avoid some of the typical problems they face such as the high density gradients within compacted parts and related cracking. In this paper, the modeling of an axisymmetric flanged part using finite element packages ABAQUS and LS-DYNA has been investigated. A material constitutive model of the Cap type, that allows the use of variable elasticity as well as a density dependent Cap aspect ratio, has been implemented into the finite element code ABAQUS whereas the geological Cap model in its conventional form was implemented in the finite element code LS-DYNA. The effect of density distribution in the part was analyzed through the plastic strain that was generated. The results obtained from the two softwares were compared to the experimental density map and a good agreement has been noted

Development of an adaptive headlamp system

The highest fatal traffic accident rate occurs on curved roads at nighttime. In most cases, the late recognition of objects in the traffic zone plays a key role. These facts point to the importance of the role of automobile forward-lighting systems. In order to provide enhanced nighttime safety measures, this work aims to design and build a prototype of steerable headlights by adapting a conventional static headlamp with a very close eye on cost and reliability. Components that are easily available in the market and suitable for developing a steerable headlight system were tested. Different kinds of tests were done on critical parts of the system in order to determine its accuracy, its response time, and the system impact. Finally, the results acquired from these various tests will be discussed. Any findings and changes that should be made are discussed and may be useful for future development

Detection of foreign bodies in canned foods using ultrasonic testing

Foreign bodies in packaged foods may pose both a safety risk and a risk of perceived degradation of quality. When food products are manufactured or packaged, small foreign objects might end up in the product. It is naturally desirable for the food industry that all foreign bodies are detected and removed before they reach customers. In this study, the ultrasonic method was used to detect the foreign bodies in canned foods. In order to establish a technical concept for the detection of foreign bodies in canned foods, an experimental investigation was carried out using pulse-echo ultrasonic testing. A number of simulated foreign object pieces were deliberately put inside the canned food and the results were analyzed. The approach demonstrates that ultrasound has potential for application in many industrial food packaging environments where foreign objects need to be detected. Indeed, detection up to 4 millimeter foreign body size has been done for rock and metal foreign bodies

General framework for inverse identification of consecutive parameters

The study of inelastic behavior of materials generally follows two steps: (1) the formulation of the mathematical model representing the governing physical effects and (2) the identification of the material's constants. The latter is traditionally achieved through experimental measurements. In this direct identification process, the problem of interpretation of experimental tests requires the assumption of homogeneity of deformation and therefore the use of an approximation metho

Effect of flow patterns on two-phase flow rate in vertical pipes

During two-phase gas-liquid flow in pipelines, the fluids may take up different flow patterns. The exact nature of the flow pattern varies according to conduit size and geometry, fluids’ properties, and each phase’s velocity. When the conduit size and fluid properties are constant, then any changes in individual flow rates will result in changes to the flow regime. Predicting the flow patterns within a pipe is essential as it is a critical parameter that determines the pressure gradient and liquid holdup in the conduit. This paper presents the results in predicting the multiphase flow patterns and their effects on flow measurements in vertical pipes. The study was conducted on vertical upward multiphase flow using well and reservoir properties. OLGA dynamic simulator was used to predict flow pattern in a vertical pipeline for 35 oil wells using electrical submersible pumps (ESP) with external pipe diameters of 3.5 inch. The predicted oil flow rates of 35 ESP oil wells were compared with measured flow rates and a good agreement was observed. Indeed, the results indicated that the variation of the flow pattern had insignificant impact and it was insensitive to the accuracy of the flow rate values of the ESP oil wells where the average overall flow rates accuracy was lower than +/-10%. Additionally, simulation results demonstrated a promising model performance and showed the magnitude of possible variation between the oil rates measured with different methods

Design and modeling of silicon MEMS accelerometer

In developing Micro Electro Mechanical Systems (MEMS), Finite Element Analysis (FEA) is usually relied upon to study these micro-structures in determining stress, deformation, resonance, temperature distribution, electromagnetic interference, and electrical properties. With this kind of approach, the performance of the devices can be easily expanded, as well as reducing the time and cost of MEMS production. This paper focuses on the modeling of silicon MEMS accelerometer in an attempt to design a surface micro-machined accelerometer that satisfies certain pre-determined specifications

Enhancing magnetic particle testing of automotive parts

The principle disadvantage in magnetic particle inspection, as generally practiced today, is the combination of variable human judgment and interpretation, and variations in the critical components' characteristics which are: magnetic particle liquid sensitivity, ultraviolet intensity variations, and magnetic field variations at the surface of the test piece. In high speed inspection systems, these variables can reduce the reliability of magnetic particle inspection flaw detection to only about 70% [I]. What is needed is an online, heavy duty, high speed parts inspection with online documentation and almost perfect flaw detect ability within calibrated equipment, if possible, by using modem electronic systems. Currently, the automated MT systems are still in their first stages and are developed on individual researchers' basis [2]. Also, the few current systetns in the market which can automatically perform magnetic particle testing are extremely expensive. Hence, the need to provide a reasonable automated MT system with a comparable performance for inspecting surface defects in ferromagnetic materials automotive component

Signal analysis of vibration measurements for condition monitoring of bearings

Rotating machinery is a common class of machinery in industry. The root cause of faults in rotating machinery is often faulty rolling element bearings. These rolling element bearings wear out easily due to the metal-metal contacts and create faults in the outer race, inner race, or balls. This study compares several techniques used for monitoring bearing condition. These techniques are based on the processing of vibrational data in the time-domain, frequency-domain, or time-frequency-domain. It was found that the discrete wavelet transform which is based on time-frequency analysis produces the best results