tailieunhanh - New trends and developments in automotive industry Part 11

Các chuyên ngành cơ bản của cơ khí bao gồm: động học, tĩnh học, sức bền vật liệu, truyền nhiệt, động lực dòng chảy, cơ học vật rắn, điều khiển học, khí động học, thủy lực, chuyển động học và các ứng dụng nhiệt động lực học. Các kỹ sư cơ khí cũng đòi hỏi phải có kiến thức và năng lực áp dụng những khái niệm trong môi trường kỹ thuật điện và hóa học. Với một mức độ nhỏ, cơ khí còn trở thành kỹ thuật phân tử - một mục tiêu viễn cảnh của nó là tạo. | 290 New Trends and Developments in Automotive Industry coating surface contains different areas having different cross-linking densities. Theses parts of coatings have a lower elastic behavior and therefore are able to restore the stress. In addition the lower cross-linking density of some parts of clear coat may be attributed to a lower curing degree. Therefore it may be expected that these parts of coating have a more polarity than other parts due to the presence of unreacted functional groups. This may cause a stronger interaction of gums polar groups to clear coat surface at these areas. Based upon the above explanations the stress inserted to the clear coat can affect some parts of the coating more intensively than the other parts. Therefore stress can be propagated from the weak points. In this way the applied stress may be dissipated by the crack formation Ramezanzadeh et al. 2010c . Effect of basecoat pigmentation on gum attack It was previously demonstrated that Ramezanzadeh et al. 2010c Yari et al. 2009a basecoat pigmentation can considerably influence the mechanical properties of an automotive clear coat. This behavior was attributed to the curing degree and post reactions occurred. Therefore according to these results outdoor weathering conditions may well affect the clear coat properties based on the type of basecoat. Biological resistance of an automotive clear coat can also be expected to show different behavior depending on the basecoat pigmentation type. To show how basecoat pigmentation affect coating behavior against gum attack the effect of gum on fully coated and free films of the clear coats applied over silver and black basecoat are shown in Figure 24 Ramezanzadeh et al. 2010c . Fig. 24. Effect of basecoat pigmentation on their biological performance in the case of gum attack on A1 and A2 full coated and B1 and B2 free films Ramezanzadeh et al. 2010c . Effects of Environmental Conditions on Degradation of Automotive Coatings 291 It