An Examination of a Proposed Method for Evaluating Nonlinear Effects in Fracture Assessment

1976 ◽  
Vol 98 (1) ◽  
pp. 40-45
Author(s):  
N. J. I. Adams ◽  
H. G. Munro
Keyword(s):  
Simple Model ◽  
Correction Factor ◽  
Nonlinear Behavior ◽  
Nonlinear Effects ◽  
Compact Tension ◽  
Experimental Results ◽  
Specimen Length ◽  
Center Crack ◽  
Fracture Assessment ◽  
Specific Material

A proposal put forward by Liebowitz and Eftis suggests a method of accounting for nonlinear behavior observed in fracture. A simple model analysis of a center crack sheet and supporting experimental results, indicate that the corrected toughness based on load point displacement will not be single valued for a specific material. It is established that both the correction factor and deviation from linearity due to cracktip yielding vary with specimen length. Additionally, tests on compact tension specimens indicate that difficulties exist when trying to correlate corrected toughness values from one specimen configuration to another.

Tool Design for ECM: Correction Factor Method

1988 ◽  
Vol 110 (2) ◽  
pp. 111-118 ◽  
Author(s):  
M. S. Reddy ◽  
V. K. Jain ◽  
G. K. Lal
Keyword(s):  
Simple Model ◽  
Correction Factor ◽  
Electrochemical Machining ◽  
Tool Design ◽  
Experimental Results ◽  
Tolerance Limits ◽  
Plane Parallel ◽  
Electrochemical Drilling ◽  
Tool Shape ◽  
Good Agreement

A simple model for tool (cathode) design for plane parallel electrochemical machining and electrochemical drilling has been proposed. Assuming the initial tool shape to be complementary to required work shape, the desirable and predicted anode profiles have been compared and the error between them has been evaluated. Using this error, the correction factor has been calculated to modify the tool shape. This procedure is repeated till the designed tool can produce an anode profile within the prescribed tolerance limits. Using this technique, tools for tapered, flat, exponential, parabolic, and nonstandard work shapes have been designed. Bare tools have been designed for straight and tapered sided holes. Comparison between analytical and experimental results shows a good agreement between them.

scholarly journals TSUNAMI GENERATION AND PROPAGATION

1972 ◽  
Vol 1 (13) ◽  
pp. 146
Author(s):  
Joseph L. Hammack ◽  
Frederic Raichlen
Keyword(s):  
Linear Theory ◽  
Source Region ◽  
Three Dimensional ◽  
Frequency Dispersion ◽  
Nonlinear Effects ◽  
Its Region ◽  
Experimental Results ◽  
Specific Class ◽  
Two Dimensional ◽  
Three Dimensional Models

A linear theory is presented for waves generated by an arbitrary bed deformation {in space and time) for a two-dimensional and a three -dimensional fluid domain of uniform depth. The resulting wave profile near the source is computed for both the two and three-dimensional models for a specific class of bed deformations; experimental results are presented for the two-dimensional model. The growth of nonlinear effects during wave propagation in an ocean of uniform depth and the corresponding limitations of the linear theory are investigated. A strategy is presented for determining wave behavior at large distances from the source where linear and nonlinear effects are of equal magnitude. The strategy is based on a matching technique which employs the linear theory in its region of applicability and an equation similar to that of Korteweg and deVries (KdV) in the region where nonlinearities are equal in magnitude to frequency dispersion. Comparison of the theoretical computations with the experimental results indicates that an equation of the KdV type is the proper model of wave behavior at large distances from the source region.

Experimental Assessment of the Performance of CECO Wave Energy Converter in Irregular Waves

2018 ◽  
Author(s):  
Claudio A. Rodríguez ◽  
F. Taveira-Pinto ◽  
P. Rosa-Santos
Keyword(s):  
Wave Energy ◽  
Transfer Functions ◽  
Nonlinear Effects ◽  
Model Tests ◽  
Experimental Results ◽  
Irregular Waves ◽  
Scale Model ◽  
Experimental Assessment ◽  
Simplified Approach ◽  
Wave Basin

A new concept of wave energy device (CECO) has been proposed and developed at the Hydraulics, Water Resources and Environment Division of the Faculty of Engineering of the University of Porto (FEUP). In a first stage, the proof of concept was performed through physical model tests at the wave basin (Rosa-Santos et al., 2015). These experimental results demonstrated the feasibility of the concept to harness wave energy and provided a preliminary assessment of its performance. Later, an extensive experimental campaign was conducted with an enhanced 1:20 scale model of CECO under regular and irregular long and short-crested waves (Marinheiro et al., 2015). An electric PTO system with adjustable damping levels was also installed on CECO as a mechanism of quantification of the WEC power. The results of regular waves tests have been used to validate a numerical model to gain insight into different potential configurations of CECO and its performance (López et al., 2017a,b). This paper presents the results and analyses of the model tests in irregular waves. A simplified approach based on spectral analyses of the WEC motions is presented as a means of experimental assessment of the damping level of the PTO mechanism and its effect on the WEC power absorption. Transfer functions are also computed to identify nonlinear effects associated to higher waves and to characterize the range of periods where wave absorption is maximized. Furthermore, based on the comparison of the present experimental results with those corresponding to a linear numerical potential model, some discussions are addressed regarding viscous and other nonlinear effects on CECO performance.

scholarly journals Modelling of ‘sub-atomic’ contrast resulting from back-bonding on Si(111)-7×7

2016 ◽  
Vol 7 ◽  
pp. 937-945 ◽  
Author(s):  
Adam Sweetman ◽  
Samuel P Jarvis ◽  
Mohammad A Rashid
Keyword(s):  
Simple Model ◽  
Experimental Results ◽  
Striking Similarity ◽  
Orbital Structure ◽  
Dangling Bond ◽  
Lennard Jones ◽  
Detailed Explanation ◽  
Afm Imaging ◽  
Back Bonding ◽  
Molecular Contrast

It has recently been shown that ‘sub-atomic’ contrast can be observed during NC-AFM imaging of the Si(111)-7×7 substrate with a passivated tip, resulting in triangular shaped atoms [Sweetman et al. Nano Lett. 2014, 14, 2265]. The symmetry of the features, and the well-established nature of the dangling bond structure of the silicon adatom means that in this instance the contrast cannot arise from the orbital structure of the atoms, and it was suggested by simple symmetry arguments that the contrast could only arise from the backbonding symmetry of the surface adatoms. However, no modelling of the system has been performed in order to understand the precise origin of the contrast. In this paper we provide a detailed explanation for ‘sub-atomic’ contrast observed on Si(111)-7×7 using a simple model based on Lennard-Jones potentials, coupled with a flexible tip, as proposed by Hapala et al. [Phys. Rev. B 2014, 90, 085421] in the context of interpreting sub-molecular contrast. Our results show a striking similarity to experimental results, and demonstrate how ‘sub-atomic’ contrast can arise from a flexible tip exploring an asymmetric potential created due to the positioning of the surrounding surface atoms.

Significance of Considering Nonlinear Effects in Predicting the Dynamic Behavior of Rotating Machinery

1995 ◽  
Vol 1 (4) ◽  
pp. 431-458 ◽  
Author(s):  
Sherif T. Noah ◽  
Padmanabhan Sundararajan
Keyword(s):  
High Performance ◽  
Degrees Of Freedom ◽  
Nonlinear Behavior ◽  
Nonlinear Effects ◽  
Rotating Machinery ◽  
Modeling And Analysis ◽  
Rotor Systems ◽  
Rotor Support ◽  
Complex Phenomena ◽  
New Generation

Limitations of the currently practiced linearized analysis of industrial rotating machinery are dis cussed. An appreciation of these limitations is particularly significant for the development of new generation, high performance machinery in which new materials, rotor supports, coupling components, and sophisticated control systems will be used. In the absence of adequate familiarity and experience with the new systems, vari ous complex phenomena associated with their nonlinearities, which may lead to malfunction or catastrophic failure, could be missed altogether. A uniform approach to accurate modeling and analysis of rotor-support systems will therefore be essential. The present paper provides an exposition of recently published studies in nonlinear rotordynamics and their relevance to the design, analysis, and monitoring of rotating machinery. This includes a brief discussion of available analytical/computational methods and the various techniques proposed, which seek reducing the order of rotor systems with large number of degrees of freedom. In ad dition, new results on the nonlinear behavior of fluid-film bearings are presented herein to further emphasize the importance of nonlinear effects.

Radiofrequency Heating of Rubber and Carbon Black Mixes

1968 ◽  
Vol 41 (5) ◽  
pp. 1219-1230
Author(s):  
N. H. Langton
Keyword(s):  
Simple Model ◽  
Carbon Black ◽  
Breakdown Voltage ◽  
Random Distribution ◽  
Reliable Data ◽  
Experimental Results ◽  
Dielectric Heating ◽  
Radiofrequency Heating ◽  
Uniform Array

Abstract In conclusion, the simple model of a uniform array of spherical conducting particles of negligible size, when modified for a random distribution, enables predictions as to the maximum permissible loading of carbon black in a rubber/black mix that can be heated by dielectric heating without breakdown. The theory agrees qualitatively with the results of Gehman's theory of random filler dispersions. It is not possible to compare values given by the theory with experimental results, because there is no reliable data giving breakdown voltage figures for rubber/black mixes of known dispersion. However predictions given by the theory agree qualitatively with experiments.

Fracture Assessment of Pipes Having Multiple Flaws Based on Ramberg–Osgood-Type Stress–Strain Relationships

2011 ◽  
Author(s):  
Hideo Machida ◽  
Tetsuya Hamanaka ◽  
Yoshiaki Takahashi ◽  
Katsumasa Miyazaki ◽  
Fuminori Iwamatsu ◽  
...  
Keyword(s):  
Flow Stress ◽  
Stress Concentration ◽  
Fracture Strength ◽  
Strain Curve ◽  
Assessment Method ◽  
Experimental Results ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Strain Relationship ◽  
Fracture Assessment

This paper describes a fracture assessment method for a pipe having multiple circumferential flaws. According to Fitness-for-Service (FFS) codes for nuclear facilities published by the Japanese Society of Mechanical Engineers (JSME), the fracture strength of a high-ductility pipe having a circumferential flaw is evaluated using the limit load assessment method assuming the elastic–perfectly-plastic stress–strain relationship. In this assessment, flow stress is used as a proportional stress. However, previous experimental results [1, 2, 3] show that a crack penetrates before the entire flawed pipe section reaches the flow stress. Therefore, stress concentration at a flaw was evaluated on the basis of the Dugdale model [4], and the fracture strength of the crack-ligament was evaluated. This model can predict test results with high accuracy when the ligament fracture strength is assumed to be tensile strength. Based on this examination, a fracture assessment method for pipes having multiple flaws was developed considering the stress concentration in the crack-ligament by using the realistic stress–strain relationship (Ramberg–Osgood-type stress–strain curve). The fracture strength of a multiple-flawed pipe estimated by the developed method was compared with previous experimental results. When the stress concentration in the crack-ligament was taken into consideration, the fracture strength estimated using the Ramberg–Osgood-type stress–strain curve was in good agreement with experimental results, confirming the validity of the proposed method.

Blockage Corrections for Blunt-Based Bodies of Revolution

1968 ◽  
Vol 72 (696) ◽  
pp. 1058 ◽  
Author(s):  
W. A. Mair
Keyword(s):  
Correction Factor ◽  
Experimental Results ◽  
Base Pressure ◽  
Alternative Methods ◽  
Wind Tunnels ◽  
Maximum Diameter ◽  
Bodies Of Revolution ◽  
Blockage Correction ◽  
Mach Numbers ◽  
Experimental Values

Calvert has considered alternative methods of estimating the blockage corrections for blunt-based bodies of revolution in closed wind tunnels at low Mach numbers. His models were all of maximum diameter 152 mm, with an ellipsoidal nose section 203 mm long followed by a cylindrical afterbody. The ratio of overall length L to maximum diameter d varied from about 1.5 to 5.5. For each model the base pressure was measured in wind tunnels of two different sizes, so that the blockage correction factor e for the smaller tunnel could be derived for each model from the experimental results. These experimental values of e were compared with alternative theoretical estimates, using the methods given by Evans, Maskell and Pank-hurst and Holder.

The nonlinear behavior of varicose disturbances in a simple model of the Gulf Stream

1991 ◽  
Vol 38 ◽  
pp. S591-S622 ◽  
Author(s):  
L.J. Pratt ◽  
J. Earles ◽  
P. Cornillon ◽  
J.-F. Cayula
Keyword(s):  
Simple Model ◽  
Gulf Stream ◽  
Nonlinear Behavior
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