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Fracture Behaviour of Pipe Grade Polyolefins
Fiedler, Lubomír ; Hutař, Pavel (referee) ; Kučera, Jaroslav (referee) ; Vlach, Bohumil (advisor)
The thesis deals with the study of the fracture behaviour of the pipe grades of high density polyethylene (HDPE). Detailed study of current state of knowledge was performed in the first part. The focus was put on those types of polymers used for pipeline applications, the limit states of the plastic pipes, and the key parameters affecting the fracture behaviour of plastic pipes’ materials. The methods used for testing the plastic pipes and native pipeline materials were summarized. In the second part of this work, the relationship between the processing conditions, internal structure and fracture behaviour of the native types of HDPE pipe grades was evaluated. Than, the correlation between short-term alternative tests and the standardized accelerated full notch creep test (FNCT) was studied. An experimental basis for numerical model for evaluation of the fracture behaviour of multilayer pipes was established. Two types of non-homogeneous specimens for evaluating the resistance of multilayer pipes against slow crack growth (SCG) were suggested. This evaluation was based on the parameters of linear elastic fracture mechanics (LEFM) and elasto-plastic fracture mechanics (EPFM).
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Fracture Behaviour of Pipe Grade Polyolefins
Fiedler, Lubomír ; Hutař, Pavel (referee) ; Kučera, Jaroslav (referee) ; Vlach, Bohumil (advisor)
The thesis deals with the study of the fracture behaviour of the pipe grades of high density polyethylene (HDPE). Detailed study of current state of knowledge was performed in the first part. The focus was put on those types of polymers used for pipeline applications, the limit states of the plastic pipes, and the key parameters affecting the fracture behaviour of plastic pipes’ materials. The methods used for testing the plastic pipes and native pipeline materials were summarized. In the second part of this work, the relationship between the processing conditions, internal structure and fracture behaviour of the native types of HDPE pipe grades was evaluated. Than, the correlation between short-term alternative tests and the standardized accelerated full notch creep test (FNCT) was studied. An experimental basis for numerical model for evaluation of the fracture behaviour of multilayer pipes was established. Two types of non-homogeneous specimens for evaluating the resistance of multilayer pipes against slow crack growth (SCG) were suggested. This evaluation was based on the parameters of linear elastic fracture mechanics (LEFM) and elasto-plastic fracture mechanics (EPFM).
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Fracture mechanics parameters of bi-material body
Šestáková, Lucie
Multilayer pipes consisting of different materials are frequently used in praxis because of partial improvement of the properties of pipe systems. To estimate their service life the basic fracture parameters have to be determined. In this work finite element calculations are applied in order to estimate the stress intensity factor K and T-stress values. Transferability of the fracture mechanics parameters obtained from two proposed C-type specimens to pipe systems was discussed using a constraint-based two-parameter fracture mechanics approach.
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