Search Results

Protection of surfaces is a critical factor in determining the extended service life of a structure in polluted and aggressive environments. In particular, a rapid growth of the technology for the protecting coating of cold rolled steel is experienced, for the use in transport, electric housewares, building and industrial plants. Numerous changes have taken place in the production of zinc coatings on steel in order to improve the corrosion resistance using zinc alloy platings. Our research group collected from the international production a number of selected galvanized steel samples, including electrodeposited zinc alloys, multilayer coatings, hot dip galvanized steels. On the selected materials we established and analyzed morphology, composition, crystal structure, impurity content and distribution, using many surface microanalysis techniques.

In order to reduce the volume of waste in general and of shredder waste from the disposal of scrap cars, the German Federal Government has prepared a draft regulation, which will be implemented unless the automotive industry and the distributors of imported cars take action on their own to achieve these objectives. The regulation provides that the car manufacturers are fully responsible for the environmentally controlled disposal of scrap cars. The return of scrap cars to the work industry must be free of change for the last owner. A nation-wide network for the return of scrap cars must be implemented by end of 1993. To reduce the amount of shredder waste the automotive industry is expected to practice recycling on non-metallic materials. Facilities required for thermal treatment of residues, which cannot be recycled, are to be installed on account of the originator, i.e. the automotive industry.

Processes involving use of reactive polymers received recently considerable attention also for producing components suitable for automotive structural applications. In particular polyurethane structural RIM technology seems to be the route of choice in terms of productivity, reliability and physico- mechanical performances in order to fit the automotive industry needs in the production of parts requiring superior load bearing properties. In this frame the development of long pot life snap-cure resins, fast and effective reinforcement preforming techniques as well as the development of computerized provisional processing methodologies are of paramount importance in view of industrialization of the technology. In this paper a description of the work carried out by Enichem Montedipe and Montedison is given. In particular a new family of PU systems, based on special isocyanate variants, is reported.

The socio-economic system is coming to the conclusion that the environment will no longer tolerate and absorb all of man's interventions, and that natural resources no longer constitute a cheap and inexhaustible source of wealth. In this scenario of the limits of nature and ever-increasing environmental costs, we are faced with the problem of recovering and reusing the materials which go into the manufacture of an automobile. The replacement of metal materials with polymer materials leads to a reduction in the re-usable waste, and to an increase in the amount of waste with no economic value, or even with a negative economic value. The use of the non-ferrous and non-aluminous materials in an automobile is beyond the capabilities of new techniques for scrapping automobiles, which means that at the end of their lives, the automobiles must be disassembled, sorted on the basis of the constitute materials, recovered and recycled.

Shape memory materials undergo temperature-induced martensitic phase transformations that involve reversible dimensional changes. In performing these changes in shape, the shape-memory material is able to do work against external constraints, and this is the basis for shape-memory low-temperature heat engines. The transformation temperatures on heating and cooling are often not very different (little hysteresis) and are well defined and reproducible. Furthermore, these temperatures can be adjusted by varying the composition of the shape memory alloy. Internal combustion engines dissipate approximately two-thirds of the fuel energy as heat to the exhaust and coolant systems. A low-temperature heat engine could convert a fraction of this heat energy to useful work. This paper discusses the conceptual basis for the application of shape memory heat engines to internal combustion engine powered vehicles. Metallurgical and thermodynamic factors are discussed, as well as engine efficiency.

The paper describes recent developments in the use of stainless steel to make the parts of buses which are most liable to corrosion. Sheet metal is used for the outer panelling, and square and rectangular tubes for the body. The types of steel used and their fabrication are analyzed. Finally, a brief description is given of the stainless steels used to make car exhaust systems.

The main use of FRC in automobiles, with the exception of a few specialized low volume vehicles, has been until now in semistructural parts. One of the most promising process in development today, that may play major role in future structural composite fabrication, is based on SRIM technology. The rapid and extensive introduction of this process goes also through the development of deeper theoretical knowledge of the process and the development of computer simulation to aid mold design and choice of proper processing parameters. To contribute SRIM advancement, a preliminary model has been developed for viscosity changes, extent of the reaction and temperature rises, associated with the mold filling stage, as well as a simple software to evaluate the pressure drop through different combinations of reinforcements.

Mold designers and foundrymen spend a lot of time in developing molds without knowing exactly the phenomena which take place inside. Simulor, which has been used in an industrial environment for two years, offers the solution to make foundrymen understand what happens during the filling of the mold and the solidification of the part. Based on navier-stokes and heat transfer equations, simulor provides speed distribution and metal front evolution in the cavity and thermal map in the mold and the part. Some examples with different metals (cast iron, aluminum alloy) cast with various processes (sand or die casting, low pressure or gravity casting) will be given. This new tool will given foundrymen the opportunity to test the mold before having it machined and will also allow reduction in development delays.

Particulate reinforced aluminum composite is described and properties shown. Application of this material to specific components are discussed, and it is shown that significant progress has been achieved on the road to commercial automotive introduction.

In order to improve the design of drawn parts and to reduce the number of trial and error tests, Renault has undertaken the development and the validation of various finite element procedures and codes. This paper describes the function of each software and its level of integration into the design process. One of them is already an operational tool used be planners whilst the others are still in the validation phase. Selected examples show typical applications of the computer programs on automotive parts.

Indirect squeeze casting technology is one of the most attractive fabrication techniques of near net shape components constituted by aluminum matrix composite (AMC) materials. AMCs reinforced with both continuous and discontinuous ceramic elements have been mainly produced by infiltration of porous preforms. Nevertheless, a further promising production route offered by this technique is given by the possibility to employ ingots of pre-reinforced aluminum alloys containing ceramic particles (silicon carbide or alumina); ingots are remelted and, under suitable operative conditions, high quality composite castings of simple and complex shape are produced by squeeze casting. The present paper describes the results of an extensive experimental work carried out by Alures-Centro Tecnico Porcessi on a pilot plant scale employing a vertical squeeze casting machine with a clamping force of 315 tons.

In this paper the socio-economic and technical problems of the handling of car wrecks are discussed. The recovery of metals as a goal for shredder operations will increasingly be supplemented with the recovery of other materials such as polymers. In order to deal economically and technically with polymer materials, it is necessary to know in advance which type of wreck handling will be used. Also optimization of shredder operations allow less freedom to incorporate a variety of materials when compared with selective dismantling or disassemble of cars. It is argued that various technical solutions have to be accompanied by increased cooperation along the firms that are connected to the handling of car wrecks. Cooperation between the scrap context and designers is essential, in order to optimize dismantling practices according to criteria of environmentally preferred solutions.

This paper describes the experimental activity carried out at Aerospace Engineering Department of Politecnico di Milano about energy absorption capability of glass-epoxy RTM specimens, representative of automotive crash front structure sub-components. After the analysis of some automotive crashworthiness aspects, especially relevant to the structural adoption of composite materials, the specimen used and the technological route to produce them are described. Then experimental arrangements, test procedure and measurement technique, relevant to static and crash test are presented. Finally test results, reported in the form of numerical values, diagrams and high-velocity films are shown and critically commented.

Compression molding of thermoplastic sheets, consolidated or non- consolidated, reinforced with glass fibers (GMT, GRT) is applied as an economic production process in the automotive industry. The aim of this work is to evaluate how the physical and mechanical strength characteristics depend on the presence or absence of ribs and how component performance may be changed by modifying the molding parameters, altering the content and orientation of the reinforcement fibers in the ribbed areas. For this purpose, two statistical designs will be considered, the first carried out on a box type component without ribs, the second on the same component with a set of internal ribs. Two different materials with a PP matrix will be tested, a GMT reinforced with continuous random glass fibers and a 12 mm random glass fibers composite.

Ceramic composite materials have been intensively studied during the last years. Particles and whisker reinforcement have shown the simultaneous advantage to allow the preparation of composite materials by conventional processing and to lead, when under optimum conditions, to dramatic toughening and strengthening. Since wear resistance of brittle material have been shown to be related to both hardness and toughness, composite materials with improved were resistance have been developed for cutting tools or bearing applications. However the mechanism responsible for toughening is of major important for wear resistance effectiveness. We have therefore reviewed the main mechanisms before presenting some examples of composites materials for wear resistance applications.

Semi-liquid forming process, applied to pressure die-casting, permits to obtain low cost components with high qualitative characteristics and adequate mechanical performances. The technology is based on the employment of material with globular microstructure (flow-cast alloys) obtained subjecting a metal alloy at the time of solidification to an elevated shear rate. Such microstructure permits the accomplishment of conventional forming processes at temperatures in solidification range. The particular fluid-dynamic properties of the semi-liquid slurry and the lower injection temperature allow to obtain casting with improved soundness, without need of impregnation, and to extend die life. The present work describes the Weber (Magneti Marelli) activity of the process industrialization and some applications for the manufacture of automotive components.

The paper review some recent efforts, made by the aluminum industry, towards the development of new advanced alloys for aerospace applications; unconventional production technologies and MMC occupy an outstanding position in this context. Raid solidification processes are currently used for obtaining advanced alloys and, among them, the powder metallurgy route is one of the most commonly applied, since it has reached a considerable level of maturity. Experimental results of PM materials are shown and discussed in order to appreciate the potentialities of this class of materials and some recent further progress is shown: the spray deposition approach (osprey process). After having described the main features of the osprey process, some results obtained at the Department of Aerospace Engineering of Pisa about the development of high strength Al-alloy and MMC obtained by means of the osprey process are shown.

The following paper describes the experimental activity regarding the setting-up and characterization of a car engine bracket in Al-Si12Cu2FeZn-F alloy produced by the new technology squeeze casting. LExperimentation was carried out at the Alures squeeze casting pilot plant. Static and dynamic characterization (fatigue resistance on test samples and the component itself) was carried out at Teksid and Fiat Auto. Characterization test have demonstrated the considerable advantages offered by the new technology compared with conventional production processes.

The replacement with plastic of an important component, formerly in steel, in the timing drive of a heavily duty diesel engine has been studied and realized. The substituted part is the toothed coupling connecting the injection pump to the timing drive. Torque that stresses the coupling has been measured with laboratory tests. The tooth stresses have been calculated with FEM analysis. Finally, fatigue tests have been carried out directly on the engine at different loadings. The test results are consistent with the predicted behavior of this component.

As a result of the rapid expansion of liquid molding in closed mold, fiberglass mat performers have rapidly changed in order to meet the high production requirements. The reasons for this interest in RTM and SRIM can be found in the considerable benefits offered by this technology which include: 1) ability to produce very large parts (weights up to 70 kg are currently being prototyped); 2) continuous and homogeneous reinforcement or even predetermined distribution of the reinforcement in the mold; 3) the ability to produce structures using cores of various types; and 4) the ability to use large inserts, even if they are metallic. The creation and development of this technology has been possible thanks to the introduction of very low viscosity reactive polymers. These materials permits very fast impregnation of the reinforcement in the closed model, thereby decreasing the cure time and the overall cycle time.