bluuebunny/crossref_metadata_2025 huggingface dataset:
An Analysis of the Errors Involved in Component Pick Up and Registration for Automated Printed Circuit Board Assembly
Authors: Radhakrishnan T. , Hegde S. M.
Published: March 2013

In the high-speed, automated assembly of printed circuit boards, sufficient accuracy of the assembler system is required to enable proper component insertion without jamming. An important intermediate step in the assembly process, particularly with a general-purpose (flexible) assembler, is the registration of a component. The various error sources contributing to component mis-registration are identified and mathematical relationships between them are developed in this study. Using these relationships in a computer program, appropriate sizes and tolerances for the critical system parameters can be determined for successful component registration and assembly.
Building Layered Models to Support Engineering Decision Making: A Machine Learning Approach
Authors: Lu S. C.-Y. , Tcheng D. K.
Published: March 2013

This paper presents a new model building methodology which, given a detailed mechanistic model of a task, can optimally produce a set of models with layered abstraction according to the user’s specified modeling objectives. These layered models can be used to evaluate decisions made at different levels of abstraction during a typical problem-solving process such as engineering design and planning. In our research, the model building process is viewed as a learning activity and inductive machine learning techniques from AI are combined with traditional optimization methods to form our prototype model building system called AIMS (Adaptive and Interactive Modeling System). The layered analysis models built by AIMS offer several distinctive advantages over those traditional analysis models which can only provide evaluations at very detailed stages of decision making. These advantages include: early evaluation to avoid costly iterations, fast execution for interactive applications, more comprehensibility for human inspection, and deep roots in domain physics for higher accuracy. Case study results of building layered models for a process design task of an intermittent cutting process are presented as a demonstration of the potential use of our system. We also explain this model building research in the context of the knowledge processing technology as a new foundation for advanced engineering automation.
Stick-Slip Vibration of Drill Strings
Authors: Lin Yao-Qun , Wang Yu-Hwa
Published: March 2013

The stick-slip vibration is introduced as a new mechanism to explain the large amplitude torsional oscillation of the drill strings in oil and gas well drillings. A record of field data is identified and simulated according to the new mechanism. The analytical results derived from the numerical simulation agree with the field data with 95.6 percent accuracy. The physical phenomenon of the stick-slip vibration of drill string is explained by initiating a phase trace in the phase plane. The beating phenomenon in drilling is interpreted in terms of stick-slip vibration. The effects of viscous damping, rotary speed and natural frequency on the stick-slip vibration are discussed.
A Transfer Function Description of Sheet Metal Forming for Process Control
Authors: Webb R. D. , Hardt D. E.
Published: March 2013

Three-dimensional forming of sheet metal parts is typically accomplished using one or two shaped tools (dies) that impart the necessary complex curvature and induce sufficient in-plane strain for part strength and shape stability. This research proposes a method of applying closed-loop process control concepts to sheet forming in a manner that automatically converges upon the appropriate tooling design. The problem of controlling complex deformation is reduced to a system identification problem where the die-part transformation is developed as a spatial frequency domain transfer function. This transfer function is simply the ratio of the measured change in spatial frequency content of the part and the die. It is then shown that such a transfer function can be used to implement closed-loop process control via rapid die redesign. Axisymmetric forming experiments are presented that establish the appropriateness of the linear transfer function description (via a test of superposition) and demonstrate the convergence properties of the proposed control method.
A Mathematical Model for Thermal Analysis of Thin Strip Casting of Low Carbon Steel
Authors: Kim Y. , Farouk B. , Keverian J.
Published: March 2013

A thermal analysis of thin strip steel casting has been conducted for planar flow casting. For a given strip thickness, the interface heat transfer coefficient, hi, has the most significant influence on average cooling rate ξavg (C/sec) and local solidification time tf. As a result, hi affects the as-cast structure and its properties. However, other factors such as melt superheat and initial substrate temperature have distinct but smaller effects on ξavg and tf. In addition, a decreasing hi makes initial isotherm movement slower and increases the delay time needed for the formation of certain types of segregation. Owing to a variation of local solidification time tf (because of cooling from one side only) there is a likely gradient of micro-structure across the thickness resulting in property variation through the steel strip thickness.
A New Process of Cold Butt Welding
Authors: Tabata T. , Masaki S.
Published: March 2013

An experimental set-up for cold butt welding is developed. Before conventional upsetting of two specimens to be bonded, surfaces of the specimens are shaved off by an edge to bring out the virgin metal which is essential to cold pressure welding. Since the bulk deformation to form the virgin surfaces is smaller compared with the conventional process without using the edge, complete bonding is accomplished with a small strain in upsetting of the specimens. This result leads the following advantages of the present process. (1) Waste of the material which is used as a flash is reduced. (2) The upsetting load, i.e., the bonding load is lower.
Computer-Aided Simultaneous Engineering for Components Manufactured in Small and Medium Lot-Sizes
Authors: Subramanyam S. , Lu S. C.-Y.
Published: March 2013

This paper presents a methodology for the simultaneous product and process design of components manufactured in small and medium lot-sizes. A key aspect of this methodology is to ensure that such components are manufacturable for the lowest possible cost in specially designed manufacturing facilities such as manufacturing cells. A computer-based design environment is proposed to cooperatively assist product designers in performing this task. The design environment is based on the model-based reasoning concept. Explicit product and manufacturing facility models are presented to support the reasoning process. These models are based on a combination of feature-based, geometric and process performance models. The reasoning mechanism is based on the Multiple Cooperative Knowledge Sources (MCKS) paradigm with explicit separation of domain and control knowledge. Domain knowledge sources deal with the product and process refinement activities while control knowledge sources deal with managing the concurrency between these two activities. The framework of the design environment is described in detail and justifications are provided for the modeling and reasoning mechanisms chosen. Preliminary results obtained from an implementation of the design environment for the simultaneous product and process design of Bearing Cages are presented. The paper concludes by summarizing the main contributions of this research and presents directions for future research work.
Computer Aided Measurement, by a Stylus, of Surfaces with Double Contour
Authors: Pasquino R.
Published: March 2013

This paper deals with computer aided measurements by a “stylus” of doubly contoured surfaces. The main result consists in the proposal of suitable algorithms, to be implemented on a personal computer, to efficiently correct the measurement errors involved by the geometry of the stylus.
Dispersion-Strengthened Alloys by the Mixalloying Process
Authors: Chu C. N. , Saka N. , Oktay S. T. , Suh N. P.
Published: March 2013

Ceramic particle-dispersed metal-matrix alloys were produced by the Mixalloying Process. In this process, two liquid metal jets were impinged into a mixing head and intimately mixed by turbulence. Liquid copper solution with dilute boron and liquid copper solution with dilute zirconium were impinged and submicron size zirconium diboride particles were produced in liquid copper. The copper-zirconium diboride mixture was solidified in a water cooled mold. Addition of excessive zirconium enhanced boride particle dispersion. Because of particle strengthening, the room temperature microhardness was twice that of annealed copper, and the hardness was retained up to 1173 K in one hour annealing treatments. Experimental result on copper-aluminum oxide alloy is also reported.
Flow Visualization of Cavitating, High-Speed, Submerged Water Jets
Authors: Szymczak M. , Tavoularis S. , Fahim A. , Vijay M. M.
Published: March 2013

Instrumentation and procedures have been developed for the visualization of high-speed, submerged water jets of the type used in cleaning, cutting, and drilling applications. As examples of these techniques, cavitation characteristics of jets produced by two plain conical nozzles as well as by a similar nozzle equipped with a transverse pin are presented. The results can be used to identify the regions of cavity inception, transport, and collapse. A semi-empirical expression relating the extent of the cavitation region to the cavitation index and the nozzle diameter is also presented.
Cutting Performance of a Cemented Carbide Drill with Three Cutting Edges
Authors: Ema S. , Marui E.
Published: March 2013

In this paper, an investigation of the cutting performance of a cemented carbide drill with three cutting edges is reported. Drilling tests were performed in which the eccentricity, straightness, cylindricity, and roundness of machined holes were measured using the least squares technique. Surface roughness was also measured. The investigation showed that the cemented carbide drill with three cutting edges is more effective than a conventional drill with two cutting edges, except for cylindricity.
Bearing Nonlinearity and Stability Analysis in High Speed Machining
Authors: Shin Y. C.
Published: March 2013

Elimination of chatter is an important problem for the successful implementation of high speed machining. Chatter is often related to the dynamic characteristics of the spindle system. The current study addresses the dynamic characteristics of angular contact bearings, which are the most commonly used type for high speed spindles, with respect to the speed change at high speeds, and reveals a very important fact on how the stiffness changes with respect to the speed change. It also illustrates how this characteristic is related to the system stability. Both analytical and experimental results show that there is a substantial change in stability zones in the high speed range and that the speed varying dynamic characteristics of a spindle must be properly taken into consideration in order to select a stable machining speed in high speed machining.
Experimental Measurement of Fluid Flow Through the Grinding Zone
Authors: Engineer F. , Guo C. , Malkin S.
Published: March 2013

An experimental test rig was developed to measure the amount of grinding fluid which flows through the grinding zone in straight plunge grinding. Proportional relationships were generally obtained between the flow rate from the nozzle and the useful flow rate of fluid passing through the grinding zone. The percentage of applied fluid passing through the grinding zone was found to depend mainly on the bulk porosity of the grinding wheel and the nozzle position. Wheel dressing has only a secondary influence, which is attributed to its influence on the surface porosity of the wheel. The workspeed and wheel depth of cut have virtually no influence.
A Study of Wheel Wear in Electrochemical Surface Grinding
Authors: Ilhan R. E. , Sathyanarayanan G. , Storer R. H. , Phillips R. E.
Published: March 2013

Major advances in Electrochemical Grinding (ECG) technology depends on new and improved abrasive grain materials. As these new grain materials are developed, proper investigations are necessary to understand the basic behavior of the process by considering significant ECG parameters. This paper presents the ECG study that was conducted to compare both commercially available (standard aluminum oxide and silicon carbide) and newly developed (sintered ceramic grain of aluminum oxide and pure white aluminum oxide) abrasive grain materials. An analysis of the effects of operating variables (such as abrasive grain material, grit concentration, grit size, feed rate, and electrolyte flow rate) on various responses is also included. The responses considered are current, spindle load, wheel wear, and G-ratio. The effects of operating variables and their interactions were determined using a 24(4) randomized factorial experimental design. The tests were conducted on 304 Stainless Steel materials. The total volume of metal removed was obtained from the geometry of the groove cut by the ECG. Statistical analysis for reach response was performed to interpret the data. It was found that there is a remarkable difference in the mean value of each response as the feed rate is switched from low to high level. Current, spindle load, and wheel wear increase and G-ratio decreases significantly as the feed rate is increased. The wheel wear at low feed rate is not significantly affected by any of the operating variables. However, the wheel wear at high feed rate is significantly affected by all the process parameters that were utilized in this study. It was observed that wheel wear is mainly caused by the breakdown of abrasive grains during the cut and to a great extent affected by the attrition resistance and the friability of the grit material. The ECG process conditions that led to short-circuiting and anodic passivity were also observed to increase the wheel wear.
A Procedure for Determination of the Strain Distribution During Simulation of Metal Forming Using Model Material Techniques
Authors: Biner S. B.
Published: March 2013

In this study, a simple and computationally efficient procedure is introduced for determination of the strain distribution during the simulations of forming processes using model material techniques. Forward-backward extrusion process is analyzed by using FEM and the model material techniques. The strain fields obtained from both methods compared favorably with each other. The advantages and the limitations of the techniques are elucidated together with suggested recommendations.
Hydrostatic Ironing—Analysis and Experiments
Authors: Tirosh J. , Iddan D. , Silviano M.
Published: March 2013

The classical ironing process by which walls of cups (or cans, etc.) are thinned is hereby replaced by a new fluid-pressure assisted process. This “hydrostatic ironing process” has the advantage of providing, under some restrictions, an unlimited amount of wall-thickness reduction. The analysis offered here is intended to explain why and how this can be achieved and to provide guidelines for designing such a process. Essentially, the analysis relates the governing variables of the process (geometrical variables, material variables, operating speed, and various friction parameters) with the applied fluid pressure via lower and upper bounds solutions. Based on these solutions, the technological advantages (and limitations) of this process are shown. Some generality is obtained by allowing the material to behave, not only as ideally perfect, but also as visco-plastic (to simulate warm temperature conditions) and as a power-law hardening material. The dynamic response to high speeds is predicted, showing that operating at high speeds is not recommended if the fluid pressure source is limited in its power. The two bounds of the solution, presented here, are relatively close to each other and coincide at small die angles. They provide, subsequently, a useful engineering tool for predetermining the operating fluid pressure for a given situation. The solutions match satisfactorily preliminary tests generated by a semi-industrial hydrostatic ironing machine with fluid pressure drive of 600 MPa. Presently, the process proves its capabilities by ironing wall-thickness of steel cups to 60 percent of its initial thickness, at relatively slow speeds (few centimeters per second).
Threshold Stress Criterion in New Wheel/Rail Interaction for Limiting Rail Damage Under Heavy Axle Loads
Authors: Kumar S. , Singh S. P.
Published: March 2013

This paper presents a qualitative discussion of the effects of increasing new (initial) wheel-rail contact stresses on the degree of damage to the rail due to heavy axle loads. The importance and need of heavy axle loads and its relationship to rail damage as a result of the increasing wheel-rail contact stresses is discussed. Various mechanisms of energy absorption/losses due to free rolling and modes of rail damage are presented. These modes include surface and internal damage due to wear, contact shear, plasticity, fatigue, shelling, crack formation, etc. The concept of threshold stress observed in free rolling friction much earlier by Drutowski is discussed and analyzed. It is believed by the authors that the threshold stress is s material property. This concept of threshold stress, based on sharply increased rates of wear in free rolling contact, is then presented and analyzed. Considerations of increased plasticity-region development, due to increasing contact stresses and their relationship to increased rates of wear seen in experiments, is utilized to determine an upper bound of contact stresses for new wheel and rail under heavy axle load conditions. It is indicated that new wheel-rail profiles, which will achieve contact stresses below the threshold stress, will enable the U.S. railroads to carry heavy axle loads without serious future damage to the rails. It is concluded that a satisfactory solution for maintaining rail integrity under heavy axle loads is possible with proper design accompanied with laboratory experimentation for the new steels as they may be used in the rails.
Measurement of Grinding Temperature of Ceramics Using Infrared Radiation Pyrometer with Optical Fiber
Authors: Ueda T. , Yamada K. , Sugita T.
Published: March 2013

The grinding temperature in the surface layer of a ceramic workpiece was measured using an IRP (infrared radiation pyrometer) connected by means of an optical fiber. Two types of optical fiber were employed: fluoride fiber and chalcogenide fiber. Si3N4, SiC, and Al2O3 were used as the work materials. The output waves of I.R.P. of Si3N4 and Al2O3 appear as curves with many peaks which are related to the infrared energy emitted from the cutting grains, but that of SiC shows no peaks at all. The highest grinding temperature was obtained in the case of Si3N4 whose grinding power is the largest of these three materials. The temperature distribution in the surface layer of the ceramics was much different from that of the steel.
Simulation of Square-to-Oval Single Pass Rolling Using a Computationally Effective Finite and Slab Element Method
Authors: Kim N. , Lee S. M. , Shin W. , Shivpuri R.
Published: March 2013

This paper presents details of a quasi three-dimensional finite element formulation for shape rolling, TASKS. This formulation uses a mix of two-dimensional finite element and slab element techniques to solve a generalized plane strain problem. Consequently, quasi steady state metal forming problems such as rolling of shapes can be analyzed with minimal computational effort. To verify the capability of the formulation square-to-round single pass rolling is simulated by TASKS and results compared with a fully three-dimensional simulation reported in literature. The results indicate reasonable agreement in roll forces, torques, and effective strain distributions during rolling. However, due to the generalized plane strain assumptions, nonhomogenieties in the rolling direction cannot be simulated. The large computational economy realized via TASKS gives this formulation the power to analyze roll pass designs with reasonable computational resources.
Improved Analysis of the Workpiece Accuracy in Turning, Based on the Emerging Diameter
Authors: Kops L. , Gould M. , Mizrach M.
Published: March 2013

Improved formulation of a workpiece deflection, accounting for the progressively increasing compliance due to the reduced diameter which emerges during turning, was developed and used to evaluate the deflection and its effect on machining error through computer simulation. The results demonstrate that when considering the moving step in diameters, the effect of depth of cut becomes more pronounced for slenderness L/D>6, It was revealed that the maximum deflection occurs either at the tailstock for lower slenderness or at approximately 0.6L from the spindle for higher slenderness. As the new formulation ensures more accurate prediction of the machining error, a nondimensional procedure generalizing the results is provided for practical applications.
Precision Grinding of Ultra-Thin Quartz Wafers
Authors: Bifano T. G. , Hosler J. B.
Published: March 2013

For bulk acoustic wave quartz resonators, the central resonant frequency is inversely proportional to the wafer thickness. The tolerance of the resonant frequency is directly proportional to the total thickness variation of the quartz wafer. To increase the operating frequency while preserving a high tolerance on frequency, thinner quartz wafers with better thickness tolerances are needed. This paper describes the design and implementation of a precision grinding apparatus capable of producing ultra-thin quartz wafers to better thickness tolerances than previously achieved. A distributed-stress fixturing method that permits machining of ultra-thin, brittle substrates is described. The machine’s precision has been achieved through a high stiffness structural loop and real-time position feedback control. Optical interferometry is used in a new technique to measure thickness variation over the entire wafer. This research will enable production of quartz crystal oscillators with higher frequencies and better quality for the resonator industry.
The Development of Free Machining Sintered Metals Including Nonmetallic Materials
Authors: Yamaguchi K. , Nakamoto T. , Mizuno T. , Daido S.
Published: March 2013

This paper deals with the lubricating action of nonmetallic inclusions in metal cutting. The purpose of this study is to find the most effective inclusions for metal cutting, and to develop free machining sintered metals including nonmetallic materials. The most effective additives are glass, boron nitride, and talc. By the addition of 3 percent glass to the iron, tool life could be increased 60 times.
Response Time Considerations for Optimal Warehouse Layout Design
Authors: Pandit R. , Palekar U. S.
Published: March 2013

We present a queueing theoretic model of a rectangular warehouse with multivehicle material handling system to study the effect of warehouse design on the response time. The response time of the material handling system is shown to decrease with districting of the warehouse into service zones. An iterative procedure is presented for districting and optimal locations of input/output points. The effect of the rate of arrival of calls on optimal door location is shown to be significant.
A Feasibility Space Approach for Automated Tolerancing
Authors: Turner J. U.
Published: March 2013

This paper develops a mathematical theory of tolerances in which tolerance specifications are interpreted as constraints that define a feasible region of a Cartesian space of model variations. Specific examples demonstrate the application of the feasibility space approach to the mathematical interpretation of tolerances of location, orientation, and form. We conclude with the description of an approach to worst-case tolerance analysis, using the feasibility space approach.
Tribological Aspects of Metal Cutting
Authors: Kramer B. M.
Published: March 2013

The machining of metals presents a unique tribological situation in which atomically clean, metallic surfaces are cleaved from the interior of the workpiece and maintained in a condition of nearly 100 percent real area of contact with the tool surface during sliding. The conditions of high pressure, high temperature, and essentially uncontaminated contact during sliding create a highly ideal tribological system for analysis. As compared to conventional sliding wear, the analysis of which is complicated by multiple passes of the counterface materials and various forms of contamination and surface reaction, the predictive modeling of tool wear has achieved somewhat greater, if still modest, success. Current models of cutting tool wear are assessed with regard to their usefulness in developing quantitative analytical methods for designing new tool materials and for selecting optimum tool materials under variations in cutting conditions. Approaches which predict the relative wear resistances of potential tool materials from the physical and chemical properties of the tool-work-piece system, without recourse to calibration tests for each system, are emphasized.
Control of Dynamic Responses of Towerlike Offshore Structures in
Waves
Authors: Yoshida K. , Suzuki H. , Oka N.
Published: March 2013

This paper presents a preliminary attempt to control the dynamic response of a towerlike offshore structure subjected to regular waves. The structures are modeled in two ways. One is a vertical rigid pipe supported at the lower end by a pin joint. The other is a vertical flexible pipe fixed at the lower end. The formulation of the optimal control shows that the control consists of a feedback control and a feedforward control based on the disturbance. In this research, two types of feedforward control are employed apart from the optimality. One is to compensate the entire wave forces acting on the structure. The other is on-off control to compensate the principal Fourier component of the wave forces by using the three states of the thruster, forward, stop and backward. The displacement and deformation of the structures were measured by an ultrasonic measurement system. The surface elevation was measured by a capacitance-type wave height meter. These data were sampled and processed by a 16-bit microprocessor, and the thrust was applied by a propeller-type thruster. The performance of the control was satisfactory, and the responses of the controlled structure were reduced to about 30 percent of those of the uncontrolled system.
Time Series Generation and Transformation—The Role of
Phase
Authors: Jefferys E. R.
Published: March 2013

Random signals with some desired power spectrum may be generated by a variety of methods, including summation of sinusoids, convolution of white noise with a kernel function or integration of a differential equation driven by white noise. These continuous models of the spectrum have discrete time equivalents, the moving average (MA) and autoregressive moving average (ARMA), respectively. This paper relates the various techniques and discusses a problem which appears in all of them. Each method involves an amplitude function, the square root of the desired power spectrum and some phase behavior which is unknown and must therefore be assumed. Results from the time series literature presented here provide a rational basis for the choice of phase. In the convolution method, the resulting kernel function is the shortest possible, consistent with the given spectrum and hence minimizes the computational cost of the subsequent signal generation. The corresponding differential equation is the simplest possible, consistent with the form of the amplitude curve. No properties of the time series are affected by the assumed phase spectrum, but phase is critical to the synthesis of correlated signals such as velocity at different points in a random wave field. The results are illustrated by a nondimensional fourth-order differential equation model of the Pierson-Moskowitz spectrum.
Random Response of Offshore Towers With Pile-Soil-Pile
Interaction
Authors: Novak M. , Mitwally H.
Published: March 2013

Dynamic pile-soil-pile interaction is analyzed using dynamic interaction factors. For pile groups, complex stiffness matrices are formulated in closed form for excitation in all vibration modes and introduced into the analysis of an offshore tower. The effects of dynamic pile-soil-pile interaction on tower response to random wave forces are demonstrated. Temporal as well as spatial randomness of wave forces are considered.
Operational Risk Evaluation of an Ice Feature Impact
Authors: Dunwoody A. B.
Published: March 2013

The risk of impact by a particular ice feature in the vicinity of an offshore structure or stationary vessel is of concern during operations. A general method is presented for calculating the risk of an impact in terms of the joint probability distribution of the forecast positions and velocities of the ice feature. A simple stochastic model of the motion of an ice feature is introduced for which the joint probability distribution of ice feature position and velocity can be determined as a function of time. The risk of an impact is presented for this model of the motion of an ice feature. Predictions of the distributions of the time until impact and the drift speed upon impact are also presented and discussed. Predictions are compared against results of a Monte Carlo simulation.
Feeling Free Despite LBZ
Authors: de Koning A. C. , Harston J. D. , Nayler K. D. , Ohm R. K.
Published: March 2013

It is sometimes argued that the occurrence of local brittle zones (LBZs) is a new phenomenon relevant only to modern low-carbon steels, while others claim that such LBZs are also present in the heat-affected zones of the C-Mn steels of the late sixties/seventies. In order to elucidate on this matter, both an “old” normalized (N) steel (1970s) and two modern low-carbon types of steel, normalized (N) and controlled rolled-accelerated cooled (CONRAC) have been investigated and compared with each other. In addition, consideration has been given to the correlation between the level of heat input during welding and the occurrence of local brittle zones. This has led in practice to a restriction of the heat input to 3.5 kJ/mm maximum for the modern low-carbon normalized steel investigated, which was used in recent projects. Furthermore, the engineering significance of LBZs is considered in the light of design aspects. It is concluded that there is little reason for concern with respect to a detrimental effect of LBZs in tubular connections of offshore structures, which is supported by a satisfactory performance of the latter to date.
Catchment Regions of Multiple Dynamic Responses in Nonlinear Problems
of Offshore Mechanics
Authors: Virgin L. N. , Bishop S. R.
Published: March 2013

Consideration of nonlinear effects in the dynamic analysis of offshore structures leads to complex phenomena even for relatively simple deterministic mathematical models. Nonlinearity in the stiffness or restoring force of a structure can be conveniently incorporated into a differential equation of motion, which can then be solved either analytically, using perturbation techniques, or numerically for various parameter ranges and forcing conditions. A particular feature of nonlinear dynamics is the appearance of multiple, competing steady-state oscillations which depend crucially on initial conditions. These coexisting stable solutions can be thought of as attractors for transient motion. A central question is therefore: How does the final long-term behavior of a dynamical system depend on the starting conditions? This paper concentrates on the computation of the domains of attraction or catchment regions using numerical techniques based on Poincare mapping ideas. The three specific examples illustrated are the roll motion of a ship, the oscillations of an articulated column and the surge response of a moored semi-submersible. This work may be considered an extension of previous work by the same authors.
Experimental Evaluation of Damping in a Steel Tubular Member of an
Offshore Platform Jacket in Air
Authors: Mason A. B. , Ullmann R. R.
Published: March 2013

Pluck tests were performed on a major diagonal member of an offshore platform jacket in the fabrication yard to develop data for assessment of structural damping. The initial displacements were varied in order to investigate dependence of damping on amplitude. The response histories were typically composed of six or seven vibrational modes having closely spaced frequencies in the 3.4–4.2-Hz range. System identification was accomplished using an output error approach. Response histories reconstructed from the system parameters identified by this method exhibit excellent fidelity to the corresponding recorded data traces. The analysis results support the assumption of linear system behavior and lead to a suggested value of 0.002 for the critical damping ratio.
Approximation of B-Spline Geometries With Lower Degree
Representations
Authors: Patrikalakis N. M. , Bardis L. , Kriezis G. A.
Published: March 2013

Exchange of data between geometric modeling systems of different inherent capabilities frequently requires approximate conversion of high degree, piecewise, polynomial curves and surface patches to lower degree representations. The objective of this work is to provide reliable methods for the approximation of high-order B-spline curves and surface patches by low-order B-spline representations. Our method guarantees a prespecified accuracy at all isoparametric points of the curve and patch, a critical feature for accurate exchange of data.
The Significance of Local Brittle Zones to the Integrity of Large
Welded Structures
Authors: Bateson P. H. , Webster S. E.
Published: March 2013

An extensive group-sponsored research program has been carried out within the UK, which, supplemented by additional work by British Steel, was designed to study the structural significance of local brittle zones. Charpy impact, CTOD and wide plate tests have been examined in order to compare and contrast their fracture behavior under similar conditions. In order to permit this comparison, two welding conditions were studied giving nominally 30 and 10 percent of coarse-grained HAZ through the thickness of a 50-mm-thick plate. The high percentage of coarse grain condition was tested in the as-welded and PWHT state and the low percentage condition as-welded only. It was shown that low toughness (<0.1 mm CTOD) measurements could be obtained using both through thickness and surface-notched test pieces over a temperature range of −30 to +10°C. Similar minimum toughness values were obtained for all the test conditions studied, but the frequency of occurrence varied. Twenty-two wide plate tests were carried out and nine fractured, four in the as-welded condition (two each for the two welding variables studied) and five in the PWHT condition. A further plate initiated a fracture from a bevel weld procedure which arrested in the parent plate. It is postulated that the requirement for an extreme combination of stress level, defect size and coarse-grained microstructure at the crack tip plus the potential for crack arrest is the reason for the absence of fractures in offshore structures.
Reliability Analysis of a Mono-Tower Platform
Authors: Kirkegaard P. H. , Enevoldsen I. , So̸rensen J. D. , Brincker R.
Published: March 2013

In this paper, a reliability analysis of a Mono-tower platform is presented. The failure modes considered are yielding in the tube cross sections and fatigue failure in the butt welds. The fatigue failure mode is investigated with a fatigue model, where the fatigue strength is expressed through SN relations. In determining the cumulative fatigue damage, Palmgren-Miner’s rule is applied. Element reliability, as well as systems reliability, is estimated using first-order reliability methods (FORM). The sensitivity of the systems reliability to various parameters is investigated. It is shown that the fatigue limit state is a significant failure mode for the Mono-tower platform. Further, it is shown for the fatigue failure mode that the largest contributions to the overall uncertainty are due to the damping ratio, the inertia coefficient, the stress concentration factor, the model uncertainties, and the parameters describing the fatigue strength.
Theoretical and Experimental Prediction of the Response of Compliant
Risers
Authors: Patrikalakis N. M. , Maekawa T. , Kriezis G. A. , Gursoy H. N.
Published: March 2013

The general three-dimensional linearized dynamic equations of a compliant riser, idealized as a rotationally nonuniform rod, around a nonlinear static configuration in the presence of general current and monochromatic wave excitation are formulated. Nonlinear forces such as quadratic drag are harmonically linearized by minimizing the mean square error between the linear approximation and the nonlinear force. The theory is implemented in a computer program which allows analysis of a variety of compliant riser configurations. Numerical examples for catenary risers are included. Comparisons of our theoretical predictions with experimental results obtained from a 1.5-m catenary compliant riser model excited monochromatically at the top parallel to a constant current are also presented to evaluate our ability to predict the response of compliant riser systems.
The Influence of Shape on Iceberg Wave-Induced Velocity
Statistics
Authors: Lever J. H. , Sen D. , Attwood D.
Published: March 2013

The motion response of small icebergs in waves has been the subject of recent investigation to provide information for the design of offshore structures resistant to glacial ice impact. Since sea state and iceberg size are random variables, probabilistic formulations have been developed for use in risk analysis-based design procedures. The present work discusses the influence of iceberg shape on its motion response in waves. Wave tank tests were conducted which show that model shape has a significant effect on wave-induced ice motion. For all models tested, however, response spectra in an irregular sea could be accurately estimated using the linear superposition of measured responses in regular waves and the measured wave energy spectra. This was true in spite of obvious nonlinear behavior exhibited in high model seas. The observed differences in wave-induced motion for differently shaped models with similar masses and characteristic lengths suggest that iceberg shape should also be treated as a random variable in probabilistic formulations. In this way, wave-induced ice motion may be represented as a function of sea state, iceberg mass or characteristic length, and iceberg shape, all random variables. An earlier risk analysis formulation is extended to incorporate the influence of randomly varying iceberg shape on ice/structure impact velocity statistics.
Three-Dimensional Ductile Constitutive Equation for
Ice
Authors: Santaoja K.
Published: March 2013

In the present paper the constitutive equation for polycrystalline materials, such as ice at wide temperature and strain rate range, is studied. The following deformation mechanisms of the material are examined: instantaneous linear elasticity, viscoelasticity, and viscoplasticity. The uniaxial material model is based on the theory proposed by Sinha. The delayed elastic strain is predicted by the modification introduced by Ashby and Duval to the equation of Sinha. A multiaxial theory to represent the reponse of isotropic polycrystalline material is developed. The multiaxial material model, called the SADS-model, coincides in case of uniaxial tension with the Ashby and Duval modification of the equations proposed by Sinha.
Random Wave-Induced Pore Pressure Accumulation in Marine Soils
Authors: Tsai Y.-T. , McDougal W. G.
Published: March 2013

Random wave-induced pore pressure is examined using linear superposition, Miner’s method and a single representative wave. Solutions are developed for deep and shallow soils. A deep soil has a higher liquefaction potential than a shallow soil for the same wave conditions. Linear superposition, Miner’s method and using the rms wave height are in general agreement for the deep soil. The significant wave overestimates the liquefaction potential and should not be used. There was poor agreement among the methods for a shallow soil.
An Analysis of a Crack in Weld by Using Near-Field as Well as Far-Field Crack Parameters
Authors: Nakagaki M. , Marschall C. W. , Brust F. W.
Published: March 2013

A study of ductile crack growth characteristics in stainless steel welds is reported in this paper. A hybrid-type analysis of combined experimental, analytical, and predictive procedures on the subject is addressed. The study focuses on the effects of a stress/strain interaction phenomenon occurring between the crack tip and the weld-base material interface. Clear dependence of the crack initiation fracture characteristics on the weld size relative to the specimen size was found. Also, fracture toughness of a tungsten inert gas weld is shown to be comparable to that for the base stainless steel metal, whereas that of a submerged arc weld is shown to be significantly lower than the base metal. Because of the stress/strain nonproportionality associated with a local unloading due to crack growth in a ductile material, the use of a crack-tip parameter such as ΔTP* or Jˆ-integral was emphasized. On the other hand, prediction of a crack instability was attempted using a less rigorous J-estimation scheme procedure.
The Effect of Geometry on the Local Stresses in Threaded Tether Connections
Authors: Newport A. , Glinka G.
Published: March 2013

The effect of changing an element of thread geometry of the complete coupling on the maximum local stress occurring in a threaded tether connection is investigated using a previously validated analog-numerical technique. Results are presented for changes in tooth fillet radius, pitch, wall thickness and the number of engaged teeth.
Modeling of Size Effect in Ice Mechanics Using Fractal Concepts
Authors: Bhat S. U.
Published: March 2013

Nominal failure pressure of ice decreases as the size of the contact area increases, over a wide range of scales. In this paper, the new and emerging concepts of fractals have been introduced to the problem of modeling this ice mechanics phenomenon. Models have been developed to explore effects of progressive failure with local load redistribution and uneven contact geometry. Unlike the nonsimultaneous failure models proposed to date for ice mechanics, the present progressive failure models show size effect in both mean and extreme ice failure pressures. While the present progressive failure models assume uniform contact, a separate fractal model of uneven contact geometry has also been proposed. This model provides a qualitative explanation for the size effect over the full range of scales.
Recent Topics in Constitutive Modeling of Cyclic Plasticity and Viscoplasticity
Authors: Ohno Nobutada
Published: March 2013

This article is concerned with a review of the literature on recent topics in constitutive modeling of cyclic plasticity and viscoplasticity of metallic materials. The subjects dealt with are: (1) multiaxial behavior such as hardening and flow of materials under nonproportional loading, (2) inelastic behavior at elevated temperature especially under plasticity–creep interaction conditions, (3) hardening behavior under thermomechanical loading, (4) ratcheting behavior under uniaxial and multiaxial cyclic loads, and (5) similarities between models. The literature published in the last five years is mainly reviewed.
Theoretical Study of Crack-Tip Singularity Fields in China
Authors: Hwang K. C. , Yu S. W. , Yang W.
Published: March 2013

Crack-tip singularity studies play a dominant role in various aspects concerning fracture and fracture mechanics. Significant advances have been made by Chinese scholars engaged in this field. A systematic, but by no means conclusive, review is attempted here to outline their major progress and to guide the international reader to obtain an access to a portion of fracture research data contributed from Chinese literature. Theoretical framework on crack-tip singularity expansion, classification of the governing differential equations, and the contiguity conditions crucial to the asymptotic assembly are discussed briefly at the beginning part of the review. Attention is then focused on various particular cases in stationary cracks, quasistatically growing cracks, and dynamically propagating cracks. A great number of solutions concerning the above-mentioned crack status with respect to different nonlinear material prescriptions are reviewed. Preliminary studies of the three-dimensional effect on crack-tip singularity fields (most have been pursued for elastic material) as well as the interplay of damage during the process of crack separation have also been carried out actively in China. Some typical results are cited here to give insights into research in these two aspects. The applications of crack-tip singularity study are highlighted by the establishment of theoretical resistance curves based on singularity field calculations. Experimental verifications of those theoretically derived curves as well as their employment in structure integrity assessment are described.
Progress in Gas-Side Fouling of Heat-Transfer Surfaces
Authors: Marner W. J.
Published: March 2013

The purpose of this paper is to present a review of recent developments in gas-side fouling, which may be defined as the deposition of an insulating layer of material onto a heat-transfer surface in the presence of a dirty gas stream. Four major topics are covered in the review: (a) Recent reviews involving various aspects of gas-side fouling, (b) Gas-side fouling mechanisms with special emphasis on transport to the surface, (c) Analytical studies including deposition, heat transfer, and pressure drop models, and (d) Experimental studies including gas-side fouling measuring devices and experimental results. Although the review focuses on work carried out during the past 10–15 years, a number of earlier contributions to the gas-side fouling literature are also included. Gas-side fouling is an extremely complex, multifaceted phenomenon and although considerable progress in this area has been made through the years, it is clear that much work remains to be done.
Modeling, Control, and Design of Flexible Structures: A Survey
Authors: Rao S. S. , Pan T. S. , Venkayya V. B.
Published: March 2013

Large structures used in space applications, are made flexible to reduce the high cost of lifting mass to orbit. These highly flexible structures will inevitably be vulnerable to dynamic excitations caused by the slewing/pointing maneuvers, thermal transients, operations of on-board coolers and generators, etc. Thus the aspects of modeling and control become extremely important for the safe and effective operation of large flexible structures (LFS’s). The theoretical, computational, and practical methodologies developed during the last decade along with the latest trends in this area are described. The research work addressing the aspects of model reduction, passive and active control, hierarchical/decentralized control, integrated structural and control design, optimal design, and sensor/actuator location selection problem for large flexible structures is discussed.
Engineering Analysis via Symbolic Computation — A Breakthrough
Authors: Beltzer Abraham I.
Published: March 2013

Since the early fifties, when the first codes for symbolic manipulations became available, their development and use have evolved into a scientific discipline. Besides the indisputable gain in efforts and higher reliability, the well-known methods of engineering analysis may acquire new dimensions, when performed via symbolic computation. There is a habitual aspect too. These days it may be more convenient for a researcher to work with a keyboard than with a pencil. The paper presents an overview of the main software available for symbolic computation and its applications to engineering analysis from the user’s viewpoint.