Investigation of reason for cracking in the attachment clamps for cooling element

The assignment handed out by Cementa in Skövde is to investigate why crack formation and propagation emerge in the fixed attachment clamps and propose solutions against it. The fixed attachments are part of the cooling element suspension, used in the cement production to cool the material coming out of the oven. There is also an attachment clamp for the cooling elements with a clearance around the cooling elements which allows some movement in all directions. Since Cementa has not performed any former research for this case, a thorough literature study is conducted. Material properties, manufacturing, fracture types and fracture mechanisms are subjects examined in the literature study. Hypotheses are formed using the gathered information and are tested by calculations and analyses. The two main hypotheses formed are: Stresses greater than the tensile strength for the steel causes crack formation. Fatigue causes crack formation. The methods used to investigate the hypotheses are calculations by hand and FE-analysis. The results from calculations and analyses shows that the clearance in the movable attachment had great influence on the stresses obtained in the fixed attachment and is the probable cause for crack formation and propagation. The most likely fracture mechanism is fatigue and corrosion, bad welds and thermal tension could be contributing factors for crack formation.