Technology & Engineering
Fracture Temperature
Fracture temperature refers to the temperature at which a material becomes susceptible to fracturing or breaking under stress. It is a critical parameter in materials science and engineering, as it helps determine the safe operating temperature range for various components and structures. Understanding the fracture temperature of materials is essential for ensuring the reliability and safety of engineering systems.
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3 Key excerpts on "Fracture Temperature"
eBook - PDF- H. Liebowitz(Author)
- 2014(Publication Date)
- Academic Press(Publisher)
Examine the internal structure of the material with existing tools; e.g., electron fractography, field ion mi-croscopy, electron diffraction, etc. 3. Induce a crack into the material that simulates the macrocrack of the theoretical model. Repeat 1 and 2 on these specimens 4. Repeat 1, 2, and 3 at the required temperature. If such a program produced reliable results, the program could be extended to include various strain rates, fatigue cycling, and sustained load conditions at the same temperatures. 106 W. E. WITZELL AND N. R. ADSIT VII. Summary The study of fracture variation with temperature is a very complex subject. To date, the area has hardly been touched. Some theories have been expounded, but experimental verification of such theories has been minimal. Not the least impediment to progress is the extreme difficulty and expense in performance of sufficient tests for experimental accuracy. While experimentation has been conducted for many years at elevated tempera-tures, the subject of fracture at these temperatures has been neglected. Perhaps this neglect has been justified, since fracture (by definition) is a somewhat nebulous (and noncritical) characteristic as temperature increases. At the other end of the scale, experimentation has exploded in recent years due to the widespread usage of cryogenic fluids as rocket fuels and oxidizers. At these temperatures, fracture and fracture toughness become extremely important. When the operating temperature of the structure is below some transition temperature (e.g., NDT or FATT), catastrophic failure results. A more tenuous problem arises when the engineering material selected or developed has a poorly defined transition. Added to the hazard of cryogenic application is the innocent fact that most materials become much stronger as the temperature approaches absolute zero. The influence of temperature on brittleness is not a new concept, of course.
- Ronald Huston, Harold Josephs(Authors)
- 2008(Publication Date)
- CRC Press(Publisher)
The complexity of the design process is also increased due to requirements of fracture control. It is generally recognized that the metallurgical phenomenon of a fracture toughness transition with temperature is exhibited by a number of low-and medium-yield-strength steels. This transition results from the interactions among temperature, strain rate, microstructure, and the state of stress. One of the more perplexing aspects of this behavior is that the customary elongation property of the material appears to have virtually no relation to the degree of fracture toughness. For example, a well-known mild steel such as the ASTM Grade A36, having an elongation greater than 20%, exhibits brittle behavior not only at lower, but also at room temperatures. It appears, therefore, that it may be advisable to characterize the materials with respect to their brittle tendencies before selecting the method of stress analysis. Traditional mechanical properties, in the form of yield point, ultimate strength, elongation, and elastic constants, must be supplemented with the thermomechanical data. The response of a stressed component, particularly at lower working temperatures, may be impossible to predict without a knowledge of fracture mechanics and the material ’ s toughness. The application aspects of fracture mechanics given in this chapter are treated in an elementary fashion. The aim of the presentation is simply to alert designers to some potential problem areas and to indicate the nature of modern trends in stress analysis and fracture control. It points to the necessity of characterizing the material ’ s behavior under stress in terms of new parameters. 27.2 PRACTICAL ASPECTS OF FRACTURE MECHANICS Fracture mechanics has been studied and documented as early as 1920 [2]. Since then, it has received considerable attention from many analysts with a focus on high-strength metals.
eBook - PDF- John Tien(Author)
- 2012(Publication Date)
- Academic Press(Publisher)
218 Victor F. Zackay and Earl R. Parker In a provocative study, Averbach (1968) derives quantitative relation-ships between the macroscopic and the microscopic variables of frac-ture of simple solids. Pellini and his co-workers have been pioneers in the transition temperature aspect of fracture. Recent papers by Pellini (1968), Puzak and Lange (1969), and Loss and Pellini (1969) are repre-sentative of their work. For a detailed and comprehensive review of the entire field of fracture the series of volumes edited by Liebowitz (1968) is invaluable. Lastly, the Proceedings of the Second Tewksbury Sympo-sium, edited by Osborn et al. (1969), is a thoughtful review of the progress made in applying what is currently known about fracture to the design of useful engineering structures. Much of the foregoing dis-cussion was based on the review papers of this symposium and on the discussion of the evolution of modern fracture mechanics by Knott (1973). III. D E S I G N I N G FOR T O U G H N E S S In the ensuing discussion, examples of both the transition tempera-ture and the fracture mechanics approaches to the design against brittle fracture are presented. The relationships between the macroscopic and microscopic viewpoints are stressed. In each case, the objective is to achieve, through compositional and microstructural control, improved combinations of strength, ductility, and toughness. A. The Transition Temperature Approach Metals or alloys with the bcc structure can fail either by shear or by cleavage. It is now well established that the propensity of bcc metals to fail by cleavage is influenced by a host of compositional and structural variables. The temperature of transition from a high-energy shear frac-ture to a low-energy cleavage fracture, for a given type of test, is a con-venient measure of the influence of these variables. Some of the com-positional and structural variables known to decrease the transition temperature in bcc iron-base alloys are 1.
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