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The utilization of Laser welding process has increased during last years in several areas of industry, due to many benefits that can be achieved with this technology, such as: flexibility, productivity and quality. Thus, the optimization of Laser welding processes has been considered as a “green field” to be explored by Laser manufacturers, automation companies and process/project engineers. Nowadays there are few researches that provide a roadmap for Laser welding processes improvement that approaches both the aspects and characteristics applied to evaluate the Laser weld application performance. Therefore, this paper has per its main purpose through an exploratory study to provide parameters toward continuous improvement of Laser welding process considering both types of Lasers: Laser spot weld and Laser seam weld of stainless steel joints, thus this work may be considered as theoretical and practical reference to be applied by people involved with Laser welding applications.

The fundamental relationship between semi-solid processing and microstructure and their effect on the flow characteristics of semi-solid metals have been studied for several years. However, how the process related microstructure influences fatigue properties has not been given the same attention. This study examines the influence of process-related microstructure on the fatigue properties of semi-solid formed A357 alloys. High-solid-fraction (62% solid) and low-solid-fraction (31% and 36% solid) semi-solid formed A357 was tested in axial fatigue with a stress ratio (R) equal to -1. The high solid fraction (HSF) material had better fatigue properties than the low solid fraction (LSF) material. This is attributed to the fatigue crack initiation mechanisms, as related to the fatigue crack initiation features and the strengths of the materials.

There are an increasing number of applications for resonant micromachines. Accelerometers, angular rate sensors, voltage controlled oscillators, pressure and chemical sensors have been demonstrated using this technology. Several of these devices are employed in vehicles. Vibrating devices have been made from silicon, quartz, GaAs, nickel and aluminum. Resonant microsystems are in constant motion and so present new challenges in the area of reliability for vehicular applications. The impact of temperature extremes, cyclic fatigue, stiction, thermal and mechanical shock on resonant device performance is covered.

This paper presents a simplified thermal model for round catalytic converters in steady state operation. Using this model, the analytic solution for the temperature distribution in the monolithic substrate is obtained. This analytic solution in the substrate is, then, combined with those in the intumescent mat [1] and the metal shell to obtain the temperature profile in the radial direction of the converter except for three unknown temperatures at the three material interfaces, which can be solved using an Excel application program. This analytical temperature solution facilitates the studies of the effects of various design parameters such as the exhaust gas temperature, exhaust gas flow rate, substrate cell geometry, converter dimensions, and ambient temperature and flow, etc.

Lithium-based battery technology offers performance advantages over traditional battery technologies at the cost of increased monitoring and controls overhead. Multiple-cell Lead-Acid battery packs can be equalized by a controlled overcharge, eliminating the need to periodically adjust individual cells to match the rest of the pack. Lithium-based based batteries cannot be equalized by an overcharge, so alternative methods are required. This paper discusses several cell-balancing methodologies. Active cell balancing methods remove charge from one or more high cells and deliver the charge to one or more low cells. Dissipative techniques find the high cells in the pack, and remove excess energy through a resistive element until their charges match the low cells. This paper presents the theory of charge balancing techniques and the advantages and disadvantages of the presented methods.

Hybrid electric vehicles have the potential to reduce air pollution and improve fuel economy without sacrificing the present conveniences of long range and available infrastructure that conventional vehicles offer. Hybrid vehicles are generally classified as series or parallel hybrids. A series hybrid vehicle is essentially an electric vehicle with an on-board source of power for charging the batteries. In a parallel hybrid vehicle, the engine and the electric motor can be used to drive the vehicle simultaneously. There are various possible configurations of parallel hybrid vehicles depending on the role of the electric motor/generator and the engine. In this paper, a comparative study of the drivetrains of five different hybrid vehicles is presented. The underlying design architectures are examined, with analysis as to the tradeoffs and advantages represented in these architectures.

Performance of two types of NOx adsorber catalysts, one based on Ba and the other based on Ba with alkali metals, was compared fresh and after thermal aging. Incorporation of sodium(Na), potassium(K) and cesium(Cs) into NOx adsorber washcoat containing barium significantly increases the NOx conversions in the temperature range of 350-600°C over that of the alkali metal free NOx adsorber catalysts. NOx performance benefit and HC performance penalty were observed on both engine dynamometer and vehicle tests for the “Ba+alkali metals” NOx adsorber catalysts. “Ba+alkali metals” NOx adsorber catalysts also demonstrate superior sulfur resistance with better NOx performance after repeated sulfur poisonings and desulfations over the “Ba based” NOx adsorber catalysts.

The development of an analytical model for multilayer stack subjected to temperature change is demonstrated here. Thin continuous layers of materials bonded together deform as a plate due to their differing coefficients of thermal expansion upon subjecting the bonded materials to the change in temperature. Applications of such structures can be found in the electronics industry (the study of warpage issues in printed circuit boards) or in the aerospace industry as (the study of laminated thin sheets used as skin structures for load bearing members such as wings and fuselage). In automotive electronics, critical high-power packages (IGBT, Power FETs) include several layers of widely differing materials (aluminum, solder, copper, ceramics) subjected to wide temperature cyclic ranges. Modeling of such structures by using three-dimensional finite element methods is usually time consuming and may not exactly predict the inter-laminar strains.

In vehicular mobility context, it is extremely important for the environmental sustainability that the available energy will be used as efficiently as possible, both in the use of internal combustion engines (ICE) as powertrain, as well in the application of Hybrid and Electric Vehicle Motors (HEV/EV). In this comparison, ICE has a lower efficiency when compared to electric motors, wasting much of the potential energy of the fuel in form of heat and noise. On the other hand, the electric vehicles face limitation in autonomy and recharge time, demanding for a more efficient use of energy stored in batteries. This study aims to present emerging technologies for reuse of energy within the automotive context, originally known as “Energy Harvesting” and “Renewable Energies”.

Fuel cells show great promise in generating electrical power for a variety of uses. In the automotive realm, one focus has been on the use of fuel cells for primary vehicle propulsion. Another emerging application is the fuel cell as the primary provider of electrical power to the vehicle, augmenting or replacing the traditional alternator, while producing higher power levels. The advantage of the fuel cell in this role is that the fuel cell operation is de-coupled from that of the engine. High power levels can be achieved independent of engine speed and power can be produced without the engine running. This paper examines the application of a fuel cell auxiliary power unit (APU) to a dual-voltage 42V/14V automotive electrical system meeting the evolving 42V PowerNet specifications. An architecture for this electrical system is presented, followed by a sizing analysis to properly match the fuel cell stack to the voltage of the PowerNet and to a 42V battery pack.

The automotive industry is moving to a higher voltage for the electrical system. This change will occur because the total electrical power required by the vehicles will increase to a level where the current requirements at 14 volts will be impractical. Some of the new loads will change the duty cycle of the battery. The most notable change is the proposed start/stop mode of vehicle operation where the engine is stopped and restarted frequently to avoid prolonged operation at idle. An additional feature would be to use an electric motor to assist in acceleration and/or to actually launch the vehicle. This paper addresses the changes in battery requirements brought on by these new features. A means of analysis for choosing the appropriate battery technology is presented. We also propose a life test to establish a benchmark for current battery technology when it is used in a new duty cycle.

In the catalytic converter, the thermal conductivity of the insulation material (intumescent mat) placed between the ceramic catalyst and the metal shell is strongly dependent on the temperature, resulting in the solving of non-linear heat conduction equations. In this paper, the analytic solution for the steady heat flow in a cylinder with temperature dependent conductivity is given. Using this analytic solution for the mat and including convection and radiation at the converter skin, an analytical expression for calculating converter skin temperature is obtained. This expression can be easily incorporated in a Fortran code to calculate the temperatures.

Long repetitive braking, such as one which occurs during a mountain descent, will result in a brake fluid temperature rise and may cause brake fluid vaporization. This may be a concern particularly for passenger cars equipped with aluminum calipers and with a limited air flow to the wheel brake systems. This paper describes the computer modeling techniques to predict the brake fluid temperature rise as well as other brake component temperatures during braking and heat soaking. Numerical results are compared to the measured vehicle data and the effects of relevant brake system parameters on the fluid temperature are investigated. The techniques developed in this study will help brake engineers to build a safer brake system and reduce the extensive vehicle tests currently required.

The most popular aluminum alloys for semi-solid automotive components are A356 and A357. The density of rheocast semi-solid A357 is higher than die cast A357 and allows for both T5 and T6 heat treatment. The mechanical properties of rheocast semi-solid A357 was found to be more dependent upon the heat treat schedule and casting soundness than by the solid content of the semi-solid slurry or the globule shape.

Lead-free solders for electronics have been actively pursued since the early 1990's here and abroad for environmental, legislative, and competitive reasons. The National Center for Manufacturing Sciences (NCMS-US)1, the International Tin Research Institute (ITRI-UK)2, Swedish Institute of Production Engineering Research (IVF-Sweden)3, Japan Institute of Electronics Packaging (JIEP Japan)4, Improved Design Life and Environmentally Aware Manufacture of Electronics Assemblies by Lead-free Soldering (IDEALS-Europe)5, and, more recently, the National Electronics Manufacturing Initiative (NEMI-US)6 have been aggressively seeking lead-free solutions The automotive industry has some unique requirements that demand extensive testing of new materials and processes prior to implementation. The specific steps taken at Delphi Automotive Systems with lead-free solder will be described along with the lessons learned along the way.

Bond wires are used in automotive electronic modules to carry current from external harness to components where flexibility under thermal cyclic loading is very essential between PCB (Printed Circuit Board) and connectors. They are very thin wires (few μm) made up of gold, aluminum or copper and have to undergo mechanical reliability to withstand extreme mechanical and thermal loads during different vehicle operation scenarios. Thermal reliability of bond wire is to make sure that it can withstand prescribed electric current under given boundary conditions without fusing thereby retaining electronic module's functionality. While carrying current, bond wire by virtue of its nature resists electric current flow and generates heat also called as joule heating. Joule heating is proportional to current flow and electrical resistance and if not handled properly can lead to thermal run away conditions.

A double dielectric barrier discharge reactor driven by an alternating voltage is a relatively simple approach to promote oxidation of NO to NO2 for subsequent reduction in a catalyst bed. The chemical performance of such a non-thermal plasma reactor is determined by its current and electric field behavior in the gap, and by the fraction of the current carried by electrons, because the key reactants which initiate the NO oxidation and accompanying chemical changes are produced there, mostly by electron impact. We have tried to determine by models and experiments the bounds on performance of double dielectric barrier reactors and guidelines for optimization. Models reported here predict chemical results from time-resolved applied voltage and series sense capacitor data.

CFD analysis was performed using the FLUENT software to design the thermal system for a hybrid vehicle battery pack. The battery pack contained multiple modular battery elements, called bricks, and the inlet and outlet bus bars that electrically connected the bricks into a series string. The simulated thermal system was comprised of the vehicle cabin, seat cavity, inlet plenum, battery pack, a downstream centrifugal fan, and the vehicle trunk. The fan was modeled using a multiple reference frame approach. A full system analysis was done for airflow and thermal performance optimization to ensure the most uniform cell temperatures under all operating conditions. The mesh for the full system was about 13 million cells run on a 6-node HP cluster. A baseline design was first analyzed for fluid-thermal performance. Subsequently, multiple design iterations were run to create uniform airflow among all the individual bricks while minimizing parasitic pressure drop.