Quality and Process Control of Nd: YAG - Laser Welding Using fuzzy Pattern Recognition Techniques for Multisensor Systems
Quality monitoring is necessary for a stable manufacturing, especially in the case of laser welding processes. During the project a system was developed which allows the analysis of in process data by fuzzy pattern recognition methods. This resulted in improved prediction of seam irregularities as compared with conventional methods. The work was carried out in the framework of the MAINE cooperative project funded by the Free State of Saxony.
Inspection and supervision by means of hierarchical fuzzy classifiers
Abstract The well-tried method of fuzzy classification is extended to hierarchical class structures to allow combinations of databased and rule-based class representations. An appropriate design method is suggested, the relationships to system theory and fuzzy logic are shown and software features and application examples are described. The main application fields are diagnostics and supervision of technical processes. Model design is based on disjunctive aggregation of atomic classes, obtained by fuzzification of vectors in the feature space (learning samples). Membership functions of all fuzzy sets are described by an uniform multidimensional parametric concept. Rule-based components are an appropriate formal tool to represent multimodal class models and to integrate explicit expert knowledge. Class models can be seen as components of several types of systems (e.g. fuzzy controller) which transform measured data into discrete fuzzy sets. For this reason the initiation of further development of new fuzzy methods is expected. Two application cases with use of a class structure and its effect are studied.
Experimental investigation of the geotechnical properties and microstructure of lime-stabilized saline soils under freeze-thaw cycling
Abstract The Song-Nen Plain in northeastern China holds one of the three largest expanses of soda saline-alkali soil in the world. Due to its disadvantageous geotechnical properties, the saline soil in this area is unable to meet the needs of construction projects. This study evaluates the stabilizing effect of adding lime to such soils. Specifically, it investigates how the physicochemical and mechanical properties and microstructure of soda saline-alkali soil are altered by lime and how these changes are affected by both freeze-thaw cycling and the duration of curing. The results reveal that adding lime to saline soil transforms clay particles into sand and silt particles and causes the pore size distribution (PSD) to become bimodal, with small-pore and macropore populations. An increase in lime content leads to an increase in the unconfined compressive strength (UCS) but a gradual decrease in both the cation exchange capacity (CEC) and plastic index. Freeze-thaw cycles break up coarse particles and aggregate finer particles, increasing the diameter of macropores and decreasing the USC; however, the effect on specimens with >9% lime is negligible. It is further shown that the geotechnical properties of the soil change immediately after the addition of lime, indicating that the cation exchange reaction takes place very quickly. Furthermore, the pozzolanic reaction leads to an increase in the percentage of sand-sized particles and a decrease in porosity after 28 days of curing. Overall, these results indicate that it is feasible to use lime to improve the engineering properties of soda saline-alkali soil in this area.