Author: P. ShahinianPublisher:
ISBN:
Category :
Languages : en
Pages : 7
Book Description
Effects of Stress Ratio and Hold-Time on Fatigue Crack Growth in Alloy 718
Author: P. ShahinianOverload Effects in Sustained-Load Crack Growth in Inconel 718
Author: T. NicholasPublisher:
ISBN:
Category : Crack growth
Languages : en
Pages : 11
Book Description
Crack-growth-rate experiments were conducted on compact tension (CT) specimens of Inconel 718 in air at 649°C. The loading spectrum consisted of a single 1 Hz cycle at R = 0.1, where R is the ratio of minimum to maximum stress-intensity factors, and a hold time which was applied at various levels of the fatigue cycle. The ratio of the hold-time amplitude to the maximum amplitude of the fatigue cycle, Rin, was kept at 1.0, 0.9, 0.8, or 0.5. Hold times were varied from 0 to 200 s. Tests were performed under computer-controlled constant-K conditions using values of the maximum of the fatigue cycle of 40 and 50 MPa m1/2. Data show that for Rin = 1.0, a linear summation model works well, while at Rin = 0.9 there is a measurable retardation effect on the crack growth during the hold time. For values of Rin less than or equal to 0.8, the sustained-load crack growth is almost completely retarded. A simple retardation model is proposed which can fit the experimental data and is based on the concept of an overload plastic zone being produced by the fatigue cycles. It is concluded that hold times do not contribute to crack growth in this material unless their amplitude is at or near the maximum amplitude of the adjacent fatigue cycles.
Report of NRL Progress
Author: Naval Research Laboratory (U.S.)Publisher:
ISBN:
Category : Naval research
Languages : en
Pages : 628
Book Description
Mechanical Behaviour of Materials at High Temperature
Author: C. Moura BrancoPublisher: Springer Science & Business Media
ISBN: 9780792341130
Category : Science
Languages : en
Pages : 758
Book Description
This volume contains the edited version of lectures and selected research contributions presented at the NATO ADVANCED STUDY INSTITUTE on MECHANICAL BEHA VI OUR OF MATERIALS AT HIGH TEMPERATURE, held in Sesimbra, Portugal, 12th-22nd September 1995, and organized by 1ST-Lisbon Institute of Technology, PortugaL The Institute was attended by 88 participants, including 15 lecturers from 17 countries including five CP countries. The lecturers were leading scientists and technologists from universities, research institutions and industry. The students were mainly young PhD students and junior academic or research staff with postgraduate qualifications (MSc or PhD). Fourteen students were from the five CP countries. The students presented research papers or posters during the Institute reporting the current progress of their research projects. A total of thirty three lectures, ten research papers and fifty posters were presented. This book does not contain the poster presentations and seven research papers were selected for publication. All the sessions were very active and quite extensive discussions on scientific aspects took place during the Institute. The Advanced Study Institute provided a forum for interaction among scientists and engineers from different areas of research, and young researchers.
Advances in Fatigue Lifetime Predictive Techniques
Author: Michael R. MitchellPublisher: ASTM International
ISBN: 0803114230
Category : Fracture mechanics
Languages : en
Pages : 495
Book Description
Twenty-seven papers from fatigue researchers and practitioners review in detail recent progress in the development of methods to predict fatigue performance of materials and structures and to assess the extent to which these new methods are finding their way into practice. The papers, from the ASTM
Hold-Time Effects in Elevated Temperature Fatigue Crack Propagation
Author: T. NicholasPublisher:
ISBN:
Category : Creep/fatigue interactions
Languages : en
Pages : 14
Book Description
An experimental investigation was conducted to evaluate the effects of hold times on the fatigue crack growth rate of Inconel 718 at 649°C using compact tension specimens. Tests were run under computer-controlled constant K conditions using compliance to determine crack length. Hold times ranging from 5 to 50 s were applied at maximum, minimum, and intermediate load levels. The data show that the hold times at maximum load were the most damaging in terms of crack growth rate. Hold times greater than 5 s led to purely time-dependent crack growth behavior which was predictable from sustained load data using K as a correlating parameter. Hold times at minimum or intermediate load levels had little or no effect on crack growth rate. A linear cumulative damage model based solely on fatigue and sustained load data was found to be adequate for spectrum loading so long as the hold times were at maximum load.
Applied Mechanics Reviews
Author: Paper
Author: Publisher:
ISBN:
Category : Mechanical engineering
Languages : en
Pages : 774
Book Description
Fatigue-crack Propagation Behavior of Inconel 718
Author: Publisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
The techniques of linear-elastic fracture mechanics were used to characterize the effect of several variables (temperature, environment, cyclic frequency, stress ratio, and heat-treatment variations) upon the fatigue-crack growth behavior of Inconel 718 base metal and weldments. Relevant crack growth data on this alloy from other laboratories is also presented. (33 fig, 39 references) (auth).
Effect of Heat Treatment on Fatigue Crack Propagation and Deformation Mode in Alloy 718 at Elevated Temperatures
Author: H. H. SmithPublisher:
ISBN:
Category :
Languages : en
Pages : 39
Book Description
Alloy 718 is a commercial, wrought nickel-base alloy widely utilized in moderate temperature structural applications and has been proposed for use in advanced nuclear systems. In such applications, Alloy 718 will experience the combined effects of cyclic and static loading and sustained elevated temperatures. However, when used in structures requiring welds, Alloy 718 exhibits reduced weld ductility and strain age cracking when given conventional post-weld duplex age heat treatments. A modified heat treatment has been previously proposed to obviate these problems and thereby improve structural reliability. The effect of conventional and modified heat treatments and combined cyclic and static loading (hold time) on crack propagation and deformation mode in two heats of Alloy 718 plate material was investigated at 427 and 593 deg C. The fatigue results show that, in general, the resistance of Alloy 718 to crack propagation at these temperatures was not adversely affected by the modified heat treatment and, under most conditions, was found to be improved in comparison with the conventional heat treatment. Scanning electron microscopy (SEM) examination of the fracture surfaces of the fatigue specimens revealed that the failure mode was dependent on test temperature and heat treatment. The material given the conventional heat treatment exhibited transgranular failure modes at both test temperatures. On the other hand, the modified heat treatment produced transgranular fractures at 427 deg C and intergranular or a mixed failure mode at 593 deg C.