A built-in cost-effective diagnostic system is being developed to monitor fatigue crack growth in aircraft structures. The proposed system consists of a SMART layer with an embedded network of distributed piezoelectric sensors/actuators, a diagnostic unit, and software. The layer is surface-mounted on the critical area where crack initiation and growth are suspected. Using the software, pre-selected diagnostic signals from a designated piezoelectric actuator to its neighboring sensors are generated by the diagnostic unit. The corresponding sensor signals are recorded and compared to a baseline reference, which was previously recorded. Based on the changes in the sensor signals, the software interprets the crack growth condition at the time of measurement. The results of this technique have been verified by experiments.

An electrochemical short-time test, which is based on potentiodynamic oxide formation on the substrate, was employed to determine the unprotected metal surface of phosphate layers selectively. The decrease of free metal area and, consequently, the increase of coverage during phosphating were followed by potentiodynamic current and capacity measurements. Using a model system consisting of mild steel with various pretreatments and a low zinc immersion phosphating process, fundamental stages of the phosphate layer formation are discussed. The proposed method enables the determination of tnucl and tfinal as important parameters of the phosphating process and the optimal treatment time at (A/A0)min. It is therefore well-suited for the quality control of phosphate coatings.

This work is concerned with basic studies on the flotative separation of three minerals: apatite, hornblende, and magnetite. Two anionic surfactants that differed in the solubility of their calcium salts were chosen as collectors (oleate and alkylsulphosuccinate). The flotation behavior of the minerals was characterized by determing adsorption isotherms and zeta-potentials, and by carrying out microflotation tests. It was shown that both collectors are adsorbed on all mineral surfaces, but at different equilibrium concentrations. As the concentration range of the onset of adsorption on apatite is lower than that on hornblende and magnetite, apatite can be separated from a mineral mixture or a respective ore. Calcium ions are often present in the flotation pulp and influence the adsorption behavior of the collectors. Due to the slight solubility of the calcium-containing minerals, apatite and hornblende, precipitation of calcium oelate occurs, as well as adsorption of oleate when a certain concentration is reached. Higher calcium ion concentrations induce more precipitation and make oleate less effective as a collector. Because of the higher solubility of the calcium alkylsulphosuccinate, precipitation does not occur in the considered concentration range. In contrast to oleate, the adsorption of alkylsulphsuccinate is shifted to lower equilibrium concentrations by calcium ions adsorbed on the mineral surface. This makes alkylsulphosuccinate a more effective collector in water with high calcium ion concentrations. The sequence of adsorption and hence, of flotation is not influenced by calcium ions, i.e., apatite, but not hornblende, can be separated from magnetitde.

In order to ensure the integrity of aircraft structures, the detection, monitoring and analysis of fatigue cracks still plays an important role today, and will do so in the foreseeable future. Meth- ods which involve the inspection of structures for cracks or flaws, without long term monitoring, are generally termed NDT techniques. At the same time, techniques exist which differ from NDT, and which monitor structures for cracks or flaws over a long period of time. One of these is called CVM, or Comparative Vacuum Monitoring. This technique provides a novel and excit- ing method for crack initiation detection, and long term monitoring of fatigue cracks in aircraft structures. CVM has the ability to monitor external surfaces of materials for crack initiation, propagation and corrosion. In addition, CVM sensors can also be embedded between components (e.g. lap joints) or within material compounds such as composite fibre. In this way, problems related to cracking, fatigue and corrosion can be detected when and where they are initiated. This tech- nique offers a quick and easy way to monitor "Hot Spot" areas and thus improve the operational efficiency of the aircraft. This presentation will briefly explain the principle of CVM technology and its current ability for crack detection on material surfaces and within lap joints. Furthermore, a few of the large array of standard CVM sensors will be shown, together with examples of laboratory tests, component tests and the first applications on a full scale fatigue test. The CVM technology can also be utilized for aircraft maintenance purposes. For this application a portable system has been developed which provides the technician with an instant status report of the monitored structure without wasting time for dismantling and reassembly of items restrict- ing access to the area of inspection.

The continued growth in air traffic has placed an increasing demand on the aerospace industry to manufacture aircraft at lower costs, while ensuring the products are efficient to operate, friendly to the environment and that the required level of safety is maintained. The primary objective of the aerospace industry is to offer products that not only meet the operating criteria in terms of payloads and range but also significantly reduce the Direct Operating Costs (DOCs) incurred by their customers, the airlines. The structure of today's commercial transport aircraft is designed considering the current and forthcoming air- worthiness regulations, the customers' requirements and manufacturing aspects. No health monitoring systems were considered for today's large transport aircraft. In the future Health Monitoring Systems will play a major rule in ensuring the structural integrity of aircraft structures. A bundle of SHM related technologies are needed to fulfill the requirements of the aircraft manufacturer and the operator. The presentation will give an overview about the activities on SHM and on the technologies under research and development within Airbus. It will start with the description of these technologies and will end with a statement about the requirements, which have to be fulfilled to use SHM systems in In-Service aircraft. An outlook on Upstream technologies in the field of SHM, like Nanotechnology and intelligent coatings, will finalize the presentation. Introduction: The continued growth in air traffic has placed an increasing demand on the aerospace industry to manufacture aircraft at lower costs, while ensuring the products are efficient to operate, friendly to the environment and that the required level of safety is maintained. The primary objective of the aerospace industry is to offer products that not only meet the operating criteria in terms of payloads and range but also significantly reduce the Direct Operating Costs (DOCs) incurred by their customers, the airlines. The structure of today's commercial transport aircraft is designed considering the current and forthcoming airworthiness regulations, the customers' requirements and manufacturing aspects. No health monitoring systems were considered for today's large transport aircraft. Loads monitoring systems with on-board evaluation to adjust the maintenance programs were evaluated in the past but were not introduced after cost / benefit trades were carried out. Reducing the structural weight and enhancing the customer's satisfaction by decreasing the maintenance cost are some of the key drivers to become competitive in the future. Using this technology permits new advanced metallic, integral fuselage design as well as optimized CFRP structures to ensure structural integrity. Maintenance aspects are increasingly significant in reducing the Direct Maintenance Costs (DMC) as most other DOCs such as fuel, airport fees, etc. have little potential for further reduction. Decreased maintenance costs will have a very positive effect, especially for airlines that are running into trouble with their costs. The biggest challenge is to find appropriate SHM technologies that can be used under in-service conditions. These technologies must prove that they are able to monitor the integrity of aircraft structures, while being reliable and durable. What is SHM? What is Structural Health Monitoring (SHM) from the point of view of an aircraft manufacturer? The basic approach is to make non-destructive testing technology to become an integral part of the aircraft structure itself. Different techniques can be used such as measuring loads and predicting actual fatigue life or sending waves being either of an acoustic, electromagnetic, thermal or any other physical nature through the structure for direct damage monitoring. Different implementations of these methods as well as sensors are available or are under development. It is therefore essential to know: • Which is the typical behaviour of different types of damage, what are the mechanisms and which physical principle is best for their detection? • Which of the different monitoring methods have the respective strength for monitoring aircraft components prone to damage?