The use of parabolic variations and the direct determination of stress intensity factors using the BIE method

Two advances in the numerical techniques of utilizing the BIE method are presented. The boundary unknowns are represented by parabolas over each interval which are integrated in closed form. These integrals are listed for easy use. For problems involving crack tip singularities, these singularities are included in the boundary integrals so that the stress intensity factor becomes just one more unknown in the set of boundary unknowns thus avoiding the uncertainties of plotting and extrapolating techniques. The method is applied to the problems of a notched beam in tension and bending, with excellent results

Solution of elastoplastic torsion problem by boundary integral method

The boundary integral method was applied to the elastoplastic analysis of the torsion of prismatic bars, and the results are compared with those obtained by the finite difference method. Although fewer unknowns were used, very good accuracy was obtained with the boundary integral method. Both simply and multiply connected bodies can be handled with equal ease

Welded transition joints of 9 Cr-1 Mo alloy steel/316SS for short life /100 hours maximum/ application

Welding parameters and elevated temperature aging and strength characteristics of transition joints between chromium molybdenum alloy steel and stainless stee

Effect of crack curvature on stress intensity factors for ASTM standard compact tension specimens

The stress intensity factors (SIF) are calculated using the method of lines for the compact tension specimen in tensile and shear loading for curved crack fronts. For the purely elastic case, it was found that as the crack front curvature increases, the SIF value at the center of the specimen decreases while increasing at the surface. For the higher values of crack front curvatures, the maximum value of the SIF occurs at an interior point located adjacent to the surface. A thickness average SIF was computed for parabolically applied shear loading. These results were used to assess the requirements of ASTM standards E399-71 and E399-81 on the shape of crack fronts. The SIF is assumed to reflect the average stress environment near the crack edge

Responding to Agency Avoidance of OIRA

Concerns have recently been raised that US federal agencies may sometimes avoid regulatory review by the White House Office of Information and Regulatory Affairs (OIRA). In this article, we assess the seriousness of such potential avoidance, and we recommend a framework for evaluating potential responses. After summarizing the system of presidential regulatory oversight through OIRA review, we analyze the incentives for agencies to cooperate with or avoid OIRA. We identify a wider array of agency avoidance tactics than has past scholarship, and a wider array of corresponding response options available to OIRA, the President, Congress, and the courts. We argue that, because the relationship between agencies and OIRA involves ongoing repeat player interactions, some of these avoidance tactics are less likely to occur (or to succeed) than has previously been alleged, and others are more likely; the difference depends significantly on how easy it is for OIRA to detect avoidance, and for OIRA, the courts, and others to respond. Further, we note that in this repeat player relationship, responses to agency avoidance tactics may induce further strategic moves and countermoves. Thus we further argue that the optimal response may not always be to try to eliminate the avoidance behavior; some avoidance may be worth tolerating where the benefits of trying to reduce agency avoidance would not justify the costs of response options and countermoves. We therefore conclude that responses to agency avoidance should be evaluated in a way similar to what OIRA asks of agencies evaluating proposed regulations: by weighing the pros and cons of alternative response options (including no action)

Three-dimensional elastic stress and displacement analysis of finite geometry solids containing cracks

The line method of analysis is applied to the Navier-Cauchy equations of elastic equilibrium to calculate the displacement distributions in various bodies containing cracks. The application of this method to these equations leads to coupled sets of simultaneous ordinary differential equations whose solutions are obtained along sets of lines in a discretized region. When decoupling the equations and their boundary conditions is not possible, the use of a successive approximation procedure permits the analytical solution of the resulting ordinary differential equations. The results obtained show a considerable potential for using this method in the three-dimensional analysis of finite geometry solids and suggest a possible extension of this technique to nonlinear material behavior

Stress analysis and stress intensity factors for finite geometry solids containing rectangular surface cracks

The line method of analysis is applied to the Navier-Cauchy equations of elastic equilibrium to calculate the displacement field in a finite geometry bar containing a variable depth rectangular surface crack under extensionally applied uniform loading. The application of this method to these equations leads to coupled sets of simultaneous ordinary differential equations whose solutions are obtained along sets of lines in a discretized region. Using the obtained displacement field, normal stresses and the stress intensity factor variation along the crack periphery are calculated for different crack depth to bar thickness ratios. Crack opening displacements and stress intensity factors are also obtained for a through-thickness, center cracked bar with variable thickness. The reported results show a considerable potential for using this method in calculating stress intensity factors for commonly encountered surface crack geometries in finite solids

Application of boundary integral equations to elastoplastic problems

The application of boundary integral equations to elastoplastic problems is reviewed. Details of the analysis as applied to torsion problems and to plane problems is discussed. Results are presented for the elastoplastic torsion of a square cross section bar and for the plane problem of notched beams. A comparison of different formulations as well as comparisons with experimental results are presented

A SIMPLIFIED METHOD OF DETERMINING THE ELASTIC STATE OF THERMAL STRESS IN A THIN, FLAT PLATE OF FINITE DIMENSIONS

Elastic state determination of thermal stress in thin, flat plate of finite dimension