Damage analysis

BE-1372 Magnetostrictive actuators for damage analysis and vibration control Pr. U. Lacce UnN. Napoli... 

The safety, availability and capacity of production plants are predetermined by the quality of the materials and the corrosion protection measures in the essential areas both are major considerations in the initial planning. Even today, damage to equipment and tanks is often assumed to be unavoidable and the damaged components are routinely replaced. By carrying out damage analysis, which points the way to knowledge of prevention of damage, the availability and life of plants can be increased considerably. This particularly applies to the use of anodic protection. 

The present paper aims to assess damage in UD GRP composites of various off-axis angles under axial loads. Damage analysis presented in this paper is drastically influenced by void content of the material and it assumes that there should be a direct relationship between the failure of composite material and its void content. 

Most textile companies do not have the personnel or equipment required for the clarification of complicated faults. On the other hand they do have the best insight into peripheral information required for damage analysis. However, when they hand over the fault to an institute or, more usually, to their suppliers of fibres, dyestuffs or auxiliaries for investigation they often only pass on part of this information. Analysis of the fault is then often regarded as technical customer service in order to promote and cement customer relationships. The intensity of... 

The last steps in this stain analysis demonstrate that comparative samples and information from peripheral areas of the case can be particularly useful aids in damage analysis. An archive with similar cases of damage can also be very useful here. If the archive is very extensive, retrieval of information on all damage cases according to different criteria should be possible, such as type of textile and fibre, damage manifestation, cause of damage, method and procedure leading to clarification and, if available, the source and client for the analysis. 

A very useful book, in which many typical cases of damage are described and illustrated, has been pubhshed by Mahal f In this book he has summarized his years of experience in damage analysis and his many publications in such a way that readers receive valuable stimulation for their own work. Further books which may be of assistance in damage analysis include those from Hearle et al., Agster, Stratmann, Greaves and Saville and from the Textile Institute. "... 

Most of the articles on damage analysis published in journals are not recent."" This is also true of company brochures on this topic. In the selection mentioned here, the last article is cited if it is part of a series of articles. Citations for previous articles in the series can be obtained there. 

The subject of preliminary examination is as varied as a later part of this section, namely miscellaneous methods. There may also be no clear-cut separation between the two. Preliminary examination is composed of simple tests, carried out in a short time and with little effort, which give the first clues in damage analysis. 

Rapid methods of separating fibre blends for damage analysis... 

Cut or ground cross-sections of fibres, yams and fabrics are of interest for fibre identification, in fault analysis in primary and secondary spinning and in checking the penetration of dyes into fibres, filaments, yams and fabrics. These methods are also used to investigate hollow and multicomponent fibres, the build-up, adhesion and evenness of coating layers and the analysis of other textile composites. AU of this can be useful for damage analysis. Grieve has written a review on cross-section preparation methods for fibres. 

This shows that IRS is a particularly powerful method for damage analysis. With this method fibres, coatings and other deposits, textile auxiliaries and substances causing stains can be identified. Chemical damage to fibres can also be detected by means of specific structural changes. All states of matter can be investigated with IR spectroscopy. Thus in damage analysis the composition of mostly liquid extraction residues is of particular interest. As well as qualitative IRS, quantitative applications are also available, where on the basis of the Lambert-Beer law the determination of the concentration of dissolved substances, the blend ratio in fibre mixtures or estimation of the comonomer content in copolymers is possible. 

Thermomechanical analysis (TMA) investigates the changes in the dimensions of a sample as a function of the temperature, for example shrinkage or extension of fibres." It is easier to work here with filaments than with staple fibres. Fibre composites and other materials are also analysed by dynamic loading. This dynamic mechanical analysis (DMA) enables, for example, the glass temperature of elastomers to be determined exactly. But in textile damage analysis TMA is seldom used. 

In conclusion the most important advantages and disadvantages of thermoanaly tic methods, both in general and in textile damage analysis, can be summarized ... 

There are a large number and variety of methods which can be used for damage analysis of textiles and these methods can naturally also be combined. It is economic restraint which most affects the imagination of the damage analyst. In other words, any method can be considered for damage analysis if it is or could be useful, does not cost too much and does not take too long. 

In addition to the important methods of damage analysis described above three further methods will be briefly described here. 

Imprint techniques have been a proven and important method in damage analysis of textiles for a long period of time. It is often advantageous not to investigate the original object under the microscope but rather the negative imprint of its surface ... 

There are two different widely used imprint methods in damage analysis, namely imprints on gelatine-coated plates and on thermoplastic films, usually polypropylene or polystyrene. In Table 8.7 the most important advantages of these complementary imprint methods are compared. 

In order to give an idea of the other methods which are used for damage analysis the following examples are listed ... 

The extensive subject of damage analysis of textiles can be divided into typical cases of damage depending on the stage of processing or the technology of yam and fabric production such as ... 

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