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For the corrosion protection of natural gas transmission pipelines, two methods are used, cathodic protection and a coating technique. In the case of cathodic protection, defects are embrittled by hydrogen occurring at crack tips or surfaces of materials. It is, however, very important to evaluate whether cracks in the embrittled area can grow or not, especially in weld metal. In this work, on the basis of elastic plastic fracture mechanics, we performed CTOD testing under various test conditions, such as potential and current density. The CTOD of the base steel and weld metal showed a strong dependence on the test conditions. The CTOD decreased with increasing cathodic potential and current density. The morphology of the fracture surface showed quasicleavage. Cathodic overprotection results in hydrogen embrittlement at the crack tip.

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Purpose:To establish management protocol for mandibular angle fracture, we describe pertinent factors including cause, impacted third molar and recent treatment tendency.Methods:We examined the records of 62 patients who had unilateral mandibular angle fracture. Sixty patients who had open reduction surgery were examined at postoperative weeks 1, 4, 8, 12, and 28.Results:Left mandibular angle fracture is frequent in younger males. Presence of the mandibular third molar can increase fracture risk. Because of attached muscle, favorable fractures occurred primarily in the mandibular angle area.Conclusion:Extracting the mandibular third molar can prevent angle fractures, and open reduction with only one plate adaptation is generally the proper treatment method for mandibular angle fracture.

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