Search Results for fracture control

This article discusses the various options for controlling fatigue and fractures in welded steel structures, with illustrations. It describes the factors that influence them the most. The article details some of the leading codes and standards for designing against failure mechanisms. Codes are presented for fitness-for-service and standards for fatigue and fracture control.

This article discusses the fracture and fatigue properties of powder metallurgy (P/M) materials depending on the microstructure. It describes the effects of porosity on the P/M processes relevant to fatigue and fracture resistance. The article details the factors determining fatigue and fracture resistance of P/M materials. It reviews the methods employed to improve fatigue and fracture resistance, including carbonitriding, surface strengthening and sealing treatments, shot-peening, case hardening, repressing and resintering, coining, sizing, and postsintering heat treatments. Safety factors for P/M materials are also detailed.

Fracture control is a systematic process to prevent fracture during operation that depends on the criticality of the component, the economic consequences of the structures being out of service, and the damage that would be caused by a fracture failure. This article describes the key principles of fracture control and reviews the concepts of damage tolerance analysis. It further presents practical guidelines to obtain useful and reasonable answers from damage tolerance analysis. The article concludes with information on fracture mechanics and fatigue design.

Workability in forging depends on a variety of material, process-variable, and die-design features. A number of test techniques have been developed for gaging forgeability depending on alloy type, microstructure, die geometry, and process variables. This article summarizes some common workability tests and illustrates their application in practical forging situations. Workability tests for open-die forging of cast structures, hot and cold open-die forging of recrystallized structures, fracture-controlled defect formation, establishing effects of process variables and secondary tensile stresses on forgeability, and flow-localization-controlled failure are some common tests. The workability test used for closed-die forging is also summarized.

This article discusses the equipment design, procedures, experimental considerations, and interpretation of the torsion tests used to establish workability. It describes the application of torsion testing to obtain flow-stress data and to gage fracture-controlled workability and flow-localization-controlled failure. The article discusses the torsion test used to establish the processing parameters that are required to produce the desired microstructures.

This article describes the basis of operating stress maps based on failure assessment diagrams, which are used to assess potential fracture in the whole range of conditions from brittle to fully plastic behavior. It discusses the factors influencing the process of constructing an operating stress map based on the principles used in constructing a residual strength diagram. These include plane strain fracture toughness, net section yield, and empiricism. The article details the fatigue crack growth behavior based on stress-corrosion cracking rates and corrosion fatigue factor. It summarizes the linear elastic fracture mechanics (LEFM) concepts for explaining the application of LEFM in damage tolerance analysis. The article exemplifies operating stress maps in a variety of applications.

This article describes the test methods of fracture toughness, namely, linear-elastic and nonlinear fracture toughness testing methods. Linear-elastic fracture toughness testing includes slow and rapid loading, crack initiation, and crack arrest method. Nonlinear testing comprises J IC testing, J-R curve evaluation, and crack tip opening displacement (CTOD) method. Other methods used include the combined J standard method, the common fracture toughness test, transition fracture toughness testing, and the weldment fracture testing method.

This article provides information on life assessment strategies and conceptually illustrates the interplay of nondestructive evaluation (NDE) and fracture mechanics in the damage tolerant approach. It presents information on probability of detection (POD) and probability of false alarm (PFA). The article describes the damage tolerance approach to life management of cyclic-limited engine components and lists the commonly used nondestructive evaluation methods. It concludes with an illustration on the role of NDE, as quantified by POD, in fully probabilistic life management.

Critical structural components must be fabricated from steels that exhibit adequate low-temperature fracture toughness because of the serious consequences of failure due to brittle fracture. This article reviews fracture resistance assessment procedures for welded joints and includes discussions on fatigue crack growth and fracture toughness. It presents the fracture toughness requirements specified by different design codes, summarizes the specifications for offshore structural steels provided by international standards organizations, and discusses the applications of these specifications. The article also focuses on advances made in steel technology and the impact of these advances on the fracture toughness of steel.

This article illustrates the role that fracture mechanics can play in failure analysis. It describes the important failure criteria as relations between design and materials factors, which are used to correlate fracture mechanics analysis to the observations of a failure analysis. Descriptions include an indication of how the factors are typically evaluated. The article also provides information on subcritical fracture mechanics. Finally, a group of failure analysis examples explain how fracture mechanics parameters can be determined and how they may be fitted into an overall failure investigation.