Failure Analysis and Life Assessment of Coating: The Use of Mixed Mode Stress Intensity Factors in Coating and Other Sur
- PDF / 568,732 Bytes
- 8 Pages / 595.276 x 790.866 pts Page_size
- 30 Downloads / 196 Views
TECHNICAL ARTICLE—PEER-REVIEWED
Failure Analysis and Life Assessment of Coating: The Use of Mixed Mode Stress Intensity Factors in Coating and Other Surface Engineering Life Assessment Yunan Prawoto • Barry Dillon
Submitted: 9 October 2011 / in revised form: 15 November 2011 / Published online: 8 December 2011 ASM International 2011
Abstract Unlike metals, where failure analysis and life assessment methods are quite established, the failure analysis and life assessment of coatings are often underrated and disregarded. This research encourages failure analysts to realize and avail the opportunity provided by an alternative approach. The authors use energy density mechanics concepts to develop a new parameter in coating blistering. A mixed mode stress intensity factor is used as a basis for the derivation. This new parameter will be useful for the researchers and practitioners engaged in coating life assessment. It is recommended that the assessor combines field-determined adhesion strength values and blister evaluation, together with laboratory-derived strain energy density data, to quantitatively predict remaining coating life. This approach also provides a tool in failure analysis.
assessment of the coating is often underrated and disregarded. The progress of the research on this subject has also been rather sluggish so far compared to that of metal being protected beneath the coating. This research begins with the existing advanced techniques of life assessment of metal structures [1–3, 5, 6], already in use in various applications ranging from power plant to implant devices, and adapts them to coatings. Failure analysts have a long way to go in even understanding the details and surface engineering aspects of coatings. Figure 1 [7] shows blistering problems with which all of us might, directly or indirectly, relate to.
Keywords Failure analysis Coating degradation Energy density mechanics Life assessment Mixed mode Stress intensity factor
A large variety of outdoor and laboratory equipment and procedures have been used for decades [8–11]. Outdoor exposures are certainly reliable and offer a good representation of the actual service life. The data collected during such exposures provide bases for the selection of particular coatings for specific applications and also provide an insight into how new coatings could be formulated. However, outdoor exposure is slow. Even with outdoor exposure sites located at places where solar insulation and/ or humidity are maximized, the acceleration factor is only of the order of twice, compared to more temperate climes. Greater acceleration can be achieved outdoors by concentration of the suns rays, or indoors by a variety of methods, such as salt-spray testing. Standardized methods (e.g., ASTM) for acceleration testing exist [11]. As early as the 1990s, the prohesion test, cycling between salt immersion, salt fog, and dry off were supplemented with alternate UV in the standard [10]. An alternate cycle of UV and continuous condensation were proposed in 1991 [12,
Data Loading...
