Larson Miller Parameter for the Prediction of the Creep Life of Unweld and Welded P91 Steel

For structural components that operate at elevated temperatures, martensitic P91 steel is preferable. It is widely used in steam generators in the fossil-fired thermal and nuclear power generation sectors due to its creep endurance and corrosion resistance. Several creep laws, such as Monkman-Grant, Theta project, Wilshire and Sinh model, Omega technique, and the Larson Miller Parameter (LMP),   have been developed over time to predict and failure of materials susceptible to the creep phenomenon. However, only the Omega Law and Larson-Miller Parameter are the only two methods approved in API 579-1. In this work, the creep test for welded and unwelded P91were conducted at temperatures of 600°C under stresses of 165, 175 MPa, and 190 MPa. In comparison to the welded specimens, the unwelded specimens displayed a continuously more substantial development of creep strain with time, resulting in a higher steady-state creep rate and a shorter rupture life. The increased magnitude of creep-rupture data has been observed to impact the dependability of creep life. Because of more significant changes in service temperature and stress conditions, the dependability of P91 steel has deteriorated, as well as an increase in creep life. The rupture life has been predicted using the LMP method, which utilizes the constant C parameter. At the same stress, the predicted creep life for weld material shows a higher value than that of the parent material, which is consistent with the experimental result

Larson Miller Parameter for the Prediction of the Creep Life of Unweld and Welded P91 Steel

For structural components that operate at elevated temperatures, martensitic P91 steel is preferable. It is widely used in steam generators in the fossil-fired thermal and nuclear power generation sectors due to its creep endurance and corrosion resistance. Several creep laws, such as Monkman-Grant, Theta project, Wilshire and Sinh model, Omega technique, and the Larson Miller Parameter (LMP),   have been developed over time to predict and failure of materials susceptible to the creep phenomenon. However, only the Omega Law and Larson-Miller Parameter are the only two methods approved in API 579-1. In this work, the creep test for welded and unwelded P91were conducted at temperatures of 600°C under stresses of 165, 175 MPa, and 190 MPa. In comparison to the welded specimens, the unwelded specimens displayed a continuously more substantial development of creep strain with time, resulting in a higher steady-state creep rate and a shorter rupture life. The increased magnitude of creep-rupture data has been observed to impact the dependability of creep life. Because of more significant changes in service temperature and stress conditions, the dependability of P91 steel has deteriorated, as well as an increase in creep life. The rupture life has been predicted using the LMP method, which utilizes the constant C parameter. At the same stress, the predicted creep life for weld material shows a higher value than that of the parent material, which is consistent with the experimental result

Cholesterol metabolism: A review of how ageing disrupts the biological mechanisms responsible for its regulation

Cholesterol plays a vital role in the human body as a precursor of steroid hormones and bile acids, in addition to providing structure to cell membranes. Whole body cholesterol metabolism is maintained by a highly coordinated balancing act between cholesterol ingestion, synthesis, absorption, and excretion. The aim of this review is to discuss how ageing interacts with these processes. Firstly, we will present an overview of cholesterol metabolism. Following this, we discuss how the biological mechanisms which underpin cholesterol metabolism are effected by ageing. Included in this discussion are lipoprotein dynamics, cholesterol absorption/synthesis and the enterohepatic circulation/synthesis of bile acids. Moreover, we discuss the role of oxidative stress in the pathological progression of atherosclerosis and also discuss how cholesterol biosynthesis is effected by both the mammalian target of rapamycin and sirtuin pathways. Next, we examine how diet and alterations to the gut microbiome can be used to mitigate the impact ageing has on cholesterol metabolism. We conclude by discussing how mathematical models of cholesterol metabolism can be used to identify therapeutic interventions