Herausforderungen & Wichtigkeit der Korrosionsprüfung an automobilen Abgassystemanlagen

Standard corrosion test methods are largely known in the automotive supplier industry and are among the common tests. Different tests, like salt spray testing as well as combined-alternating tests in climatic chambers, are commonly used to evaluate the corrosion behavior of stainless steels. Corrosion effects like uniform and pitting corrosion can be simulated and quantified, and thus base materials can be separated according to their corrosion performance. Still, the correlation to reality and the behavior in the field are still an open question. Respecting the wide range of exhaust applications, especially the influence of temperature, the technical requirements have been greatly increased in the last years and the corrosion effects are difficult to replicate. In addition, the target lifetime for exhaust systems are increasing more and more.Within the scope of a project group at FAURECIA CLEAN MOBILITY, a concept has been developed with the target to combine the common corrosion testing with application oriented component tests. The objective is to cover the time-temperature influence on the corrosion behavior of a component in one test. A testing device has been developed which combines all the technical requirements in one test under elevated temperature influence to make estimations about lifetime, design, and material selections.     

The development of novel auxetic woven structure for impact applications

Nowadays, the auxetic materials, auxetic reinforcement as well as auxetic composite are under the great attention of scientific research due to having excellent mechanical properties. In the current research work, the impact resistance of composite was improved by modifying the four layer through the thickness woven structure, that was used as reinforcement. A comparison was made between the standard four layer through the thickness and modified four layer through the thickness woven structure in terms of auxeticity and penetration. The modified four layer through the thickness woven structure showed auxetic behavior in both warp and weft direction having less penetration resistance as compared to standard sample. The four layer through the thickness non-auxetic woven structures and modified auxetic four layer thorough the thickness woven structures were used as reinforcements to develop composite for impact resistance comparison. The result showed that impact resistance of auxetic composite was 6.7% greater as compared to the non-auxetic composite. It was concluded that the greater value of impact resistance was due to the auxetic behavior of modified four layer through the thickness woven structure.     

Multi-response optimization of mechanical and comfort properties of bi-stretch woven fabrics using grey relational analysis in Taguchi method

The present paper envisages the multi-response optimization of certain factors like elastane linear density, fabric thread density and weave float on some mechanical, (i.e. stretch %, recovery %) and comfort (i.e. air permeability) properties of bi-stretch woven fabrics, under L₁₈ orthogonal array in Taguchi design. Fabric samples were produced using elastane core-spun cotton yarns both in the warp and weft. The elastane linear density, fabric thread density and weave float size were used as predictor variables, while fabric air permeability, stretch and recovery were taken as response variables. Two different elastane linear densities, i.e. 44 dtex and 78 dtex, 3 different thread densities and 3 different weave designs, i.e. 1/1 plain, 2/2 z-twill and 3/3 z-twill were used. The results have been analysed using grey relational analysis for the identification of an optimum level of process factors. Furthermore, using analysis of variance method, significant contributions of predictor variables were determined.     

Development and characterization of jute/polypropylene composite by using comingled nonwoven structures

High melt viscosity of thermoplastic matrices hinders the impregnation of fibers and their consolidation during fabrication of composites. In the present study, matrix (polypropylene) and reinforcement (jute) fibers were comingled at fiber to fiber level (fiber to matrix ratio of 30, 40, 50 and 60%) while making their nonwoven fabrics using dry laid process. Thermoforming process, in which polypropylene fibers are used and then melted for the development of composite plates. The results showed that the composite samples with 0.30 fiber volume fraction have higher mechanical properties (flexural, impact energy), while samples with 0.40 fiber volume fraction have higher tensile properties (tensile strength and modulus) due to good impregnation of fiber and better fiber-matrix interface. The composite having 0.30 fiber volume fraction has lowest value of moisture regain and diffusion coefficients than the other samples. Voids present in the microscopic images also confirmed the weak interface, when the fiber volume fraction increased up to 0.60.     

Effect of As,Cu and Sb impurities on performance of Pb‐Ca‐Sn grids of lead‐acid batteries

The performance of Pb‐Ca‐Sn grids of lead‐acid batteries made from recycled lead in 4 M H₂SO₄ in the absence and presence of traces of Cu, As and Sb, as potential impurities in the recycling process at 0.1% level, is investigated by electrochemical methods. The study includes the effect of each impurity and impurities combined on the alloy corrodibility, the efficiency of PbO₂ formation, the rate of the self‐discharge and the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER). The results show that individual impurity enhances the corrosion resistance but increases the anode corrosion and the self‐discharge rate. Impurities play opposite effects on hydrogen evolution reaction and oxygen evolution reaction either individually or combined. Concerning water loss problem, the harmful effect of individual impurity on increasing oxygen evolution reaction is compensated by their suppression of hydrogen evolution reaction. The impurities combined suppress effectively both hydrogen evolution reaction and oxygen evolution reaction relative to alloy without any impurity. Sb has the highest harmful effects on oxygen evolution reaction and the self‐discharge but it is the best in the suppression of hydrogen evolution reaction. The impurities combined relatively improve the general corrosion resistance, the anode corrosion resistance and the self‐discharge. The study supports higher tolerance levels of Cu, As and Sb in Pb‐Ca‐Sn grids, especially when present combined, than the recommended levels in the industry standards.     

Exponential localization of moving end mirror in optomechanics

We discuss the dynamics of moving end mirror of an optomechanical system that consists of a Fabry-Perot cavity loaded with dilute condensate and driven by a single-mode optical field. It is shown that quantum mechanical phenomenon of dynamical localization occurs both in position and momentum space for moving end mirror in the system. The parametric dependencies of dynamical localization are discussed. We also provide a set of parameters which makes this phenomenon experimentally feasible.     

Synthesis and Characterization of Anionic Polymeric Surfactants Based on Sulfonated Styrene

A novel series of three anionic polymeric surfactants was prepared by polymerization of sulfonated styrene and allyl esters of long chain fatty acid chlorides (decanoyl, lauroyl and palmitoyl chloride). The unique structural features of these surfactants were confirmed by different spectroscopic tools (IR and H-NMR). The surface properties of these compounds such as surface tension, interfacial tension, emulsion stability, wetting power, foam height, solubilization and dispersant properties in disperse dye systems were determined and evaluated. A comparative study was done between the chemical structures and surface properties of these compounds. Biodegradability and stability to hydrolysis in acidic and alkaline medium were also determined and evaluated.