Showing papers in "Journal of Pressure Vessel Technology-transactions of The Asme in 1992"

Limit Loads of Mechanical Components and Structures Using the GLOSS R-Node Method

Abstract: A method for determining plastic collapse loads of mechanical components and structures on the basis of two linear elastic finite element analysis is presented in this paper. The r-nodes, which are essentially statically determinate locations, are obtained by GLOSS analysis. The plastic collapse loads are determined for statically determinate and indeterminate components and structures by using the single-bar and the multibar models, respectively. The paper also attempts to unify the concepts of load-control, limit load, reference stress and stress-classification. The GLOSS R-Node method is applied to several component configurations of practical interest.

An Improved Flange Bolt-Up Procedure Using Experimentally Determined Elastic Interaction Coefficients

Abstract: Uniform bolt stress (±2 percent) was obtained in a one-pass, tension-controlled, bolt-up procedure. This was done by experimentally determining elastic interaction coefficients. The coefficients were then used to solve for the required initial bolt loads that gave the desired final stresses. The procedure worked on two similar pairs of 16-in. class 300 flanges. Each flange set had different interaction, apparently due to surface gaps and misalignment. The procedure was repeated several times with a flat sheet gasket and without a gasket. The procedure and experimental results are described in detail.

Failure Mechanisms in Nuclear Power Plant Piping Systems

Abstract: Article de synthese sur les mecanismes de rupture des tuyauteries des centrales nucleaires afin de modifier les sections III et XI du code de calcul ASME concernant la conception des recipients sous pression et des chaudieres.

Flaw Assessment Procedure for High-Temperature Reactor Components

Abstract: In this paper, an interim high-temperature flaw assessment procedure is described. This is a result of a collaborative effort between Electric Power Research Institute in the US, Central Research Institute of Electric Power Industry in Japan, and Nuclear Electric plc in the UK. The procedure addresses pre-existing defects subject to creep-fatigue loading conditions. Laws employed to calculate the crack growth per cycle are defined in terms of fracture mechanics parameters and constants related to the component material. The crack growth laws may be integrated to calculate the remaining life of a component or to predict the amount of crack extension in a given period. Fatigue and creep crack growth per cycle are calculated separately, and the total crack extension is taken as the simple sum of the two contributions. An interaction between the tow propagation modes is accounted for in the material properties in the separate calculations.

Static Analysis of Buttress Threads Using the Finite Element Method

Abstract: The finite element method has been used to investigate the stress field in threaded end closures of thick-walled high pressure vessels. A set of elastic analyses of vessels with 5, 8, 11, 15, 20 and 25 standard Buttress threads was used to propose a method for predicting the load distribution along the length of the thread. Root stress index factors in the region of the first three active threads are also included. The results of the present work contribute to the development of the new division of the ASME Pressure Vessel Code which is related to thick-walled high pressure vessels.

Nondestructive Evaluation of Adhesively Bonded Joints in Graphite/Epoxy Composites Using Acousto-Ultrasonics

Abstract: This paper is concerned with the use of the acousto-ultrasonic technique to evaluate nondestructively the mechanical performance of composite bonded joints. In this context, acousto-ultrasonic measurements followed by destructive shear tests were performed on single lap joint specimens made from graphite/epoxy adherends joined with FM 300 film adhesive. The results indicate a good correlation between acousto-ultransonic wave propagation characteristics and the shear strength of the bonded joints under different testing conditions. These correlations suggest that an estimation of the joint strength can be made by using acousto-ultrasonics provided that the measurement system is calibrated for variations of the material and geometry of the specimen.

Elastic-Plastic Fracture of Circumferential Through-Wall Cracked Pipe Welds Subject to Bending

Abstract: A methodology is proposed to carry out elastic-plastic fracture analysis of through-wall cracked ductile pipe weldments subjected to pure bending loads. It is based on deformation theory of plasticity, constitutive law characterized by Ramberg-Osgood model, and an equivalence criteria incorporating reduced thickness analogy for simulating system compliance due to the presence of a crack in weld metal. Closed-form solutions are obtained in terms of elementary functions for approximate evaluation of energy release rate and center crack opening displacement. The method utilizes material properties of both base and weld metals which are not considered in the current estimation methods. It is general and can be applied in the complete range between elastic and fully plastic conditions. Numerical examples are presented to illustrate the proposed technique. Comparisons of results with reference solutions from finite element method indicate satisfactory prediction of foregoing fracture parameters.

On the Use of the Hole-Drilling Technique for Residual Stress Measurements in Thin Plates

Abstract: The strain gage blind hole-drilling technique may be used to determine residual stresses at and below the surface of components. In this paper, the hole-drilling analysis methodology for thick plates is reviewed, and experimental data are used to evaluate the methodology and to assess its applicability to thin plates. Data on the effects of gage pattern, surface preparation, hole spacing, hole eccentricity, and stress level are also presented.

Galerkin Finite Element Displacement Formulation of Coupled Thermoelasticity Spherical Problems

Abstract: When the time rate of change of the thermomechanical forces in a continuum is high enough to produce stress wave, the solution must be sought through the simultaneous consideration of the first law of thermodynamics and the equations of thermoelasticity. The general finite element formulation of coupled thermoelasticity along with a general discussion for inclusion of mechanical and thermal boundary conditions is presented. The case is then considered for a spherical symmetry and the governing coupled thermoelastic equations are reduced for a thick sphere. Based on the Galerkin method, a Kantrovich approximation is applied to the displacement and temperature field and the finite element formulation of the problem is obtained.

Heavy-Section Steel Technology Program: Fracture Issues (Survey Paper)

Abstract: Large-scale fracture mechanics tests have resulted in the identification of a number of fracture technology issues. Identification of additional issues has come from the reactor vessel materials irradiation test program and from reactor operating experience. This paper provides a review of fracture issues with an emphasis on their potential impact on a reactor vessel pressurized thermal shock (PTS) analysis. Mixed mode crack propagation emerges as a major issue, due in large measure to the poor performance of existing models for the prediction of ductile tearing. Rectification of ductile tearing technology deficiencies may require extending the technology to include a more complete treatment of stress state and loading history effects. The effect of cladding on vessel fracture remains uncertain to the point that it is not possible to determine at this time if the net effect will be positive or negative. Enhanced fracture toughness for shallow flaws has been demonstrated for low-strength structural steels. Demonstration of a similar effect in reactor pressure vessel steels could have a significant beneficial effect on the probabilistic analysis of reactor vessel fracture. Further development of existing fracture mechanics models and concepts is required to meet the special requirements for fracture evaluation of circumferential flaws inmore » the welds of ring-forged vessels. Fracture technology advances required to address the issues discussed in this paper are the major objective for the ongoing Heavy Section Steel Technology (HSST) program at ORNL.« less

Multiple Stability Boundaries of Tubes in a Normal Triangular Cylinder Array

Abstract: This paper reports on experiments using a normal triangular cylinder array with a pitch-to-diameter ratio of 1.25 in air-cross-flow. The array consists of 18 tubes, in which 9 freely suspended tubes are linear iso-viscoelastically mounted. This unique tube mounting enables the linear damping of 9 cylinders (4, 3 and 2 cylinders in the first, second, and third cylinder row, respectively) to be continuously varied over a wide mass-damping parameter range of 10 < μδ/(ρd2 ) < 80. The experimentally observed phenomenon are correlated with nonlinear vibration theory terminology in order to improve the characterization of the excitation mechanisms. Experimental results are presented showing three stability boundaries for one flexibly mounted tube in an otherwise fixed array, as was predicted by Lever and Weaver’s “wavy wall channel model.” Flow visualization, for that arrangement, shows that their model describes the actual fluid flow past the tube reasonably well. Furthermore, multiple stability boundaries for small groups of flexibly mounted cylinders in an otherwise fixed cylinder array have, for the first time, been measured.

Effect of Composite Damage on the Fatigue Behavior of the Metal-Lined Hoop-Wrapped Cylinders

Abstract: Effects of an axial defect in the composite of hoop-wrapped steel and aluminum cylinders on the hoop stress as well as on the bulging of the liners were investigated through the numerical and experimental stress analysis. Comparison with the experimental results (reported in reference [5]) suggests that relative fatigue performance of the cylinders, containing damages to the composite wrapping, can be assessed without conducting prototype tests.

Study on the Vibrational Characteristics of a Tube Array Caused by Two-Phase Flow—Part 1: Random Vibration

Abstract: This paper presents the experimental results on turbulent buffeting forces generated both by air-water flow and by steam-water two-phase flow for the extreme pressure conditions up to 5.8 MPa and temperatures reaching 272oC, the explanation of the mechanism producing these forces, and a method for evaluating tube response caused by two-phase flow. The main source of the buffeting forces in slug or froth two-phase flow is recognized to be the impact forces caused by the intermittently rising water slugs. The slug speed and the fluid forces acting on a tube are estimated, together with an estimation of the period of the occurrence of the rising water slug. The accuracy of this estimation method is proved by comparing the theoretical response with the measured one.

Fatigue and Creep-Fatigue Life Evaluation of U-Shaped Bellows

Abstract: For the reliable operation of bellows under cyclic loadings at high temperatures, a rational evaluation method of life of bellows would be needed. Authors investigated simplified analysis methods for fatigue and creep-fatigue life prediction of U-shaped bellows considering inelasticity as well as various geometrical nonuniformity such as thickness and shape of convolutions. A conservative evaluation method of the strain range is developed, introducing three strain range amplification factors for nominal elastic strain range. Creep and relaxation behaviors of bellows are studied. Consequently, a new evaluation method of creep damage fractions is proposed which depends upon the relation between primary and secondary stresses. Fatigue and creep-fatigue tests are conducted and the validity of the present methods is discussed.