The fundamental problem of an elastic-plastic body subjected to incremental loading is reviewed using a compact internal variable approach based on work carried out at the University of Cape Town in which a quadratic ...The fundamental problem of an elastic-plastic body subjected to incremental loading is reviewed using a compact internal variable approach based on work carried out at the University of Cape Town in which a quadratic functional was developed for the free energy using Taylor series. Now the departure from that approach is the focus on developing the Liapunov function for the nonlinear differential equations of motion. Static and dynamic equations of motion are derived and shown to meet the requirements of the Liapunov function. As a consequence, time integration parameters that are used in the discrete formulations are easily obtained based on the same requirements. The resulting generalized Newton-Raphson scheme is stable in the sense of Liapunov＇s direct method.展开更多
It is well known that static seals are usually designed to be used once. In this paper, we discuss the reusability of a type of static seal called the spring energized metal C ring, which is required to be reused 4-5 ...It is well known that static seals are usually designed to be used once. In this paper, we discuss the reusability of a type of static seal called the spring energized metal C ring, which is required to be reused 4-5 times without maintenance during the lifetime of the pump. A theoretical analysis based on the nonlinear finite element method and an experimental investigation of the reusability of the C ring are carried out. The effects of the elastic modulus of the ring material, the ring wall thickness, the amount of assembly interference between the spring and the C ring, the operating temperature and the compression ratio are discussed. The parameter S, which denotes the reaction force difference percentage, is determined to measure the reusability of the C ring. The results show that the ring wall thickness plays an important role in the reusability. Although the normal force of a thick wall decreases after the ring is reused eight times, the value is still higher than the first normal force of a thin wall. In contrast, the elastic modulus of the material has the lowest impact. Here, a pre-compression ratio of 18.2% not only produces a larger first normal force but also leads to a smaller reduction in the normal force when the ring is reused. A simulated experiment is carried out to investigate the influence of the coating of the C ring on its reusability. The results show that when plastic deformation occurs on the contact surface, the contact state of the C ring coating becomes a major factor that affects the seal performance. Aging treatment at high temperatures （250℃） reduces gized metal C ring, which leads to the deterioration in the reusability the binding force of the silver coating on the spring ener of the ring.展开更多
文摘The fundamental problem of an elastic-plastic body subjected to incremental loading is reviewed using a compact internal variable approach based on work carried out at the University of Cape Town in which a quadratic functional was developed for the free energy using Taylor series. Now the departure from that approach is the focus on developing the Liapunov function for the nonlinear differential equations of motion. Static and dynamic equations of motion are derived and shown to meet the requirements of the Liapunov function. As a consequence, time integration parameters that are used in the discrete formulations are easily obtained based on the same requirements. The resulting generalized Newton-Raphson scheme is stable in the sense of Liapunov＇s direct method.
基金supported by the National Key S&T Special Project(Grant No.2012ZX06901-022)
文摘It is well known that static seals are usually designed to be used once. In this paper, we discuss the reusability of a type of static seal called the spring energized metal C ring, which is required to be reused 4-5 times without maintenance during the lifetime of the pump. A theoretical analysis based on the nonlinear finite element method and an experimental investigation of the reusability of the C ring are carried out. The effects of the elastic modulus of the ring material, the ring wall thickness, the amount of assembly interference between the spring and the C ring, the operating temperature and the compression ratio are discussed. The parameter S, which denotes the reaction force difference percentage, is determined to measure the reusability of the C ring. The results show that the ring wall thickness plays an important role in the reusability. Although the normal force of a thick wall decreases after the ring is reused eight times, the value is still higher than the first normal force of a thin wall. In contrast, the elastic modulus of the material has the lowest impact. Here, a pre-compression ratio of 18.2% not only produces a larger first normal force but also leads to a smaller reduction in the normal force when the ring is reused. A simulated experiment is carried out to investigate the influence of the coating of the C ring on its reusability. The results show that when plastic deformation occurs on the contact surface, the contact state of the C ring coating becomes a major factor that affects the seal performance. Aging treatment at high temperatures （250℃） reduces gized metal C ring, which leads to the deterioration in the reusability the binding force of the silver coating on the spring ener of the ring.
