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Coke drums are critical equipment in the petroleum industry. The failure modes of coke drums include excessive bulging deformation and fatigue cracking. The elastic-plastic behavior of a coke drum, subjected to both thermal and mechanical loadings, is analyzed for a complete cycle of operation. The effects of multiple operational cycles and localized hot/cold spots are also investigated. It is found that yielding of the clad layer starts at the very early stage in an operating cycle and permanent deformation is caused in the first operating cycle. Plastic shakedown occurs in the clad layer under combined operating thermal and mechanical loadings. It is also found that both hot and cold spots will cause bulging of the shell and the cold spot can cause more severe deformation than the hot spot. [ABSTRACT FROM AUTHOR]

A periodic array of cracks in a functionally graded coating bonded to a homogeneous substrate is considered. The medium is subjected to transient or static mechanical loads. The problem is formulated in terms of a singular integral equation with the crack face displacement as the unknown variable. In addition to the time-varied stresses and stress intensity factors for various parameters of the problem, the effect of periodic cracking on the relaxation of the transient stress on the coating surface is discussed. Also included is the influence of the material gradient (material nonhomogeneity) on the crack tip intensity factors and stresses. Solutions for a single graded layer and a graded coating bonded to an infinite substrate are given. [ABSTRACT FROM AUTHOR]

Two failure modes were observed in tensile test specimens machined from TMCP steel pipe. Longitudinal centerline cracks were formed after necking followed by the conventional cup and cone transverse failure. The formation of the longitudinal cracks was attributed to sulfur segregation and grain growth at the centerline. This gave rise to concerns that TMCP steels might exhibit low through-thickness ductility that could lead to lamellar tear failures in highly constrained joints or joints with through-thickness loadings such as in the case of tubular joints and lifting tugs. It also gave rise to a concern regarding the potential of hydrogen-induced cracking in TMCP steel vessels, pipelines, and cathodically protected tubular joints. The results of through-thickness tensile tests showed that this TMCP steel has good through-thickness ductility in spite of the presence of high sulfur segregation at the centerline. However the results of slow strain tests on a hydrogen charged through-thickness tensile specimen showed some deterioration in ductility. In addition, the fracture of the specimen was characterized by the presence of multiple circumferential cracks that are characteristic of hydrogen embrittled materials. [ABSTRACT FROM AUTHOR]

Presents a study that examined a plate weakened by doubly distributed cracks. Discussion on multiple crack problems in plane elasticity; Details of the calculated nondimensional stress intensity factors; Advantages of the application of the eigenfunction expansion variational method in solving the cracked cell problem.

Presents a study that examined a piezoelectric material strip containing an embedded crack or an edge crack perpendicular to its boundaries. Background on the temperature distribution of the material; Examination of thermal stresses in the uncracked medium; Details on the formulation of a perturbation problem.

Presents information on a study on the effect of welding heat input on cracking sensitivity of the IN738, a precipitation hardened nickel base superalloy. Discussion on the optimization of laser cladding process for IN738; Experimental procedures; Results of the study.

Presents the plane elasticity solution for the crack problem of a layered medium. Elastic property between the dissimilar homogenous surface layer and the substrate; Employment of the stiffness matrix approach; Variations of stress intensity factors as functions of geometric and material parameters of the layered medium.

Presents a study which investigated the effects of matrix cracking with irregular fracture fronts as observed in fiber reinforced ceramic composites. Methodology used to carry out the study; Difference between small crack-size matrix and large crack-size matrix cracking; Results and conclusion of the study.

High Cr ferritic heat resisting steels have been widely used for boiler components in ultrasupercritical thermal power plants operated at about 600°C. In the welded joint of these steels, type-IV crack initates in the fine-grained heat affected zone during long-term use at high temperatures and their creep strength decreases. In this paper, creep properties and creep crack growth (CCG) properties of P92 welds are presented. The CCG tests are carried out using cross-welded compact tension C(T) specimens at several temperatures. The crack front was located within the fine-grained HAZ region to simulate type-IV cracking. Finite element analysis was conducted to simulate multiaxiality in welded joints and to compare experimental results. The constitutive behavior for these materials is described by a power-law creep model. C* and Q* parameters are used to evaluate CCG rate of P92 welds for comparison. C* parameters can characterize approximately 20% of the total life of CCG in P92 welds, and Q* parameters can characterize approximately 80% of the total life. Q* parameter is one of the useful parameters to predict CCG life in P92 welds. [ABSTRACT FROM AUTHOR]

Plastic constraint correction using the equivalent CTOD concept has been studied in the International Standardization of Fracture Toughness Evaluation Procedure for Fracture Assessment of Steel Structures project. This project was carried out over a 3-year period with the foundation of the Japanese Ministry of Economy, Trade, and Industry, and the results were summarized in a draft standard "Method of constraint loss correction of CTOD fracture toughness for fracture assessment of steel component." Equivalent CTOD ratio β is proposed in terms of the constraint loss correction between the fracture performance of steel structures and fracture toughness tests using the Weibull stress as the driving force of the brittle fracture. This paper provides the application procedure of equivalent CTOD ratio to the fracture assessment of structural components. Equivalent CTOD ratio was taken in the failure assessment diagram, and discussed the applicability by comparison with large scale test results of structural component such as edge surface crack panel, center through-wall crack panel, and other geometries. [ABSTRACT FROM AUTHOR]

Experimental and analytical investigations into crack tip opening displacement (CTOD) were conducted to demonstrate the relationship between BS7448-CTOD and ASTM E1290-CTOD. The CTOD test results showed that ASTM-CTOD was occasionally much lower than BS-CTOD both in single edge notch bend specimens and in compact tension (C(T)) specimens for low-strength structural steels, and this tended to be more remarkable in C(T) specimens. In addition, the analytical results of simplified elastic-plastic fracture parameter calculation using the Electric Power Research Institute scheme demonstrated that the ratio of ASTM-CTOD to BS-CTOD was not constant but varied according to CTOD changes. Material factors such as the yield stress, the strain hardening exponent, specimen size and configurations influenced the CTOD ratio, and low strain hardening exponents in the Ramberg-Osgood relation and C(T) specimen configuration significantly decreased the CTOD ratio. An equation that transforms BS-CTOD into ASTM-CTOD is proposed in this study. This equation gives a good estimate of ASTM-CTOD from BS-CTOD. [ABSTRACT FROM AUTHOR]