A Comparison of the Strains Due to Edge Cracks and Cuts of Finite Width With Applications to Residual Stress Measurement

1993 ◽  
Vol 115 (2) ◽  
pp. 220-226 ◽  
Author(s):  
W. Cheng ◽  
I. Finnie
Keyword(s):  
Stress Measurement ◽  
Arbitrary Distribution ◽  
Finite Width ◽  
Stress Distributions ◽  
Power Functions ◽  
Third Order ◽  
Near Surface ◽  
Surface Residual Stresses ◽  
Edge Cracks ◽  
Loaded Crack

The strains on the surface near a loaded crack or cut are compared for cuts of different width to depth ratios. General solutions are obtained for an arbitrary distribution of normal and shear tractions on the faces of the crack or cut. Numerical results are presented for normal stress distributions which vary with distance from the surface as power functions of zero to third order. The results are useful for measurement of near surface residual stresses and should also be of value for crack compliance measurements of stress intensity factors.

Measurement of Near Surface Residual Stresses Using Electric Discharge Wire Machining

1994 ◽  
Vol 116 (1) ◽  
pp. 1-7 ◽  
Author(s):  
W. Cheng ◽  
I. Finnie ◽  
M. Gremaud ◽  
M. B. Prime
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Electric Discharge ◽  
Theoretical Approach ◽  
Stress Measurement ◽  
Stress Gradient ◽  
Experimental Results ◽  
Residual Stress Measurement ◽  
Near Surface ◽  
Surface Residual Stresses

In previous work it has been shown that near surface residual stresses may be deduced from surface strains produced by making a cut of progressively increasing depth. The process of electric discharge wire machining (EDWM), by providing very narrow cuts, greatly improves the ability of the method to resolve a stress gradient near the surface. However, the EDWM process may also introduce residual stresses. In the present work a model for estimating the influence of EDWM is presented, and a procedure for eliminating its effect on residual stress measurement is developed. Experimental results validate the theoretical approach.

The Compliance Method for Measurement of Near Surface Residual Stresses—Analytical Background

1994 ◽  
Vol 116 (4) ◽  
pp. 550-555 ◽  
Author(s):  
M. Gremaud ◽  
W. Cheng ◽  
I. Finnie ◽  
M. B. Prime
Keyword(s):  
Numerical Simulation ◽  
Residual Stresses ◽  
Random Errors ◽  
Residual Stress Field ◽  
Near Surface ◽  
Surface Residual Stresses ◽  
Zero Shift ◽  
Stress States ◽  
The Stability ◽  
Piecewise Functions

Introducing a thin cut from the surface of a part containing residual stresses produces a change in strain on the surface. When the strains are measured as a function of the depth of the cut, residual stresses near the surface can be estimated using the compliance method. In previous work, the unknown residual stress field was represented by a series of continuous polynomials. The present paper shows that for stress states with steep gradients, superior predictions are obtained by using “overlapping piecewise functions” to represent the stresses. The stability of the method under the influence of random errors and a zero shift is demonstrated by numerical simulation.

Evaluating Measured Tire Contact Stresses to Predict Pavement Response and Performance

2000 ◽  
Vol 1716 (1) ◽  
pp. 73-81 ◽  
Author(s):  
Reynaldo Roque ◽  
Leslie Ann Myers ◽  
Bjorn Birgisson
Keyword(s):  
Contact Stress ◽  
Contact Stresses ◽  
Embedded Sensors ◽  
Stress Distributions ◽  
Near Surface ◽  
Weak Bases ◽  
Truck Tires ◽  
Pavement Response ◽  
Pavement Structures ◽  
And Performance

Recent research has indicated that measured contact stress distributions under radial truck tires are highly complex. These stress distributions help to explain near-surface distresses that have become more prevalent since the inception of radial tires, indicating that realistic contact stresses must be considered when pavement response and performance are evaluated. However, because of the complexities involved in measuring contact stresses under tires, obtaining these measurements directly on real pavements is not possible. Consequently, contact stress measurements have been made on systems having rigid foundations with embedded sensors. Therefore, determining whether tire contact stresses measured on a rigid foundation are significantly different from contact stresses under the same tire on an actual pavement is critical. Finite element analyses conducted indicated that both vertical and lateral tire contact stresses measured on rigid foundations accurately represent the contact stresses for the same tire on typical asphalt pavement structures. Some minor differences were observed for thin (50-mm surface) pavements on weak bases, but the correspondence in terms of both distribution and magnitude was still very good. The conclusion was that contact stresses measured by devices with rigid foundations appear to be suitable for predicting response and performance of highway pavements.

Conditional likelihood and power: higher-order asymptotics

1992 ◽  
Vol 438 (1904) ◽  
pp. 433-446 ◽  
Keyword(s):  
Average Power ◽  
Nuisance Parameter ◽  
Second Order ◽  
Conditional Likelihood ◽  
Power Functions ◽  
Third Order ◽  
Contiguous Alternatives ◽  
Higher Order Asymptotics ◽  
Optimality Property ◽  
Lr Test

This paper considers, in the presence of a nuisance parameter, a very large class of tests that includes the conditional and the usual versions of the likelihood ratio (LR), Rao’s and Wald’s tests. Under contiguous alternatives and orthogonal parametrization, the power functions of the conditional and the usual versions of these tests have been compared and, in particular, it is seen that the power functions of the conditional versions, unlike those of the usual versions, are identical, up to the second-order, with the power functions of the corresponding tests with known nuisance parameter. An optimality property of the conditional LR test, in terms of second-order local maximinity, has been established. A test, optimal in the sense of third-order average power under contiguous alternatives, has been proposed. A weaker optimality property of Rao’s test, in terms of third-order average power, has also been indicated.

Measurement of Residual Stresses within a PWR Swaged Heater Tube

2011 ◽  
Vol 70 ◽  
pp. 279-284 ◽  
Author(s):  
D.M. Goudar ◽  
Ed J. Kingston ◽  
Mike C. Smith ◽  
Sayeed Hossain
Keyword(s):  
Residual Stress ◽  
Stress Distribution ◽  
Stress Measurement ◽  
Measurement Techniques ◽  
Residual Stress Distribution ◽  
Hole Drilling ◽  
Shear Stresses ◽  
Outer Diameter ◽  
Near Surface ◽  
Heater Tube

Frequent failures of the pressuriser heater tubes used in Pressurised Water Reactors (PWRs) have been found. Axial cracks initiating from the tube outer diameter have been detected in some tubes as well as the resulting electrical problems. Replacement of the heater tubes requires an undesirably prolonged plant shutdown. In order to better understand these failures a series of residual stress measurements were carried out to obtain the near surface and through-thickness residual stress profiles in a stainless steel pressuriser heater tube. Three different residual stress measurement techniques were employed namely, Deep-Hole Drilling (DHD), Incremental Centre Hole Drilling (ICHD) and Sachs’ Boring (SB) to measure the through thickness residual stress distribution in the heater tubes. Results showed that the hoop stresses measured using all three techniques were predominantly tensile at all locations, while the axial stresses were found to be tensile at the surface and both tensile and compressive as they reduce to small magnitudes within the tube. The magnitude of the in-plane shear stresses was small at all measurement depths at all locations. The various measurement methods were found to complement each other well. All the measurements revealed a characteristic profile for the through-thickness residual stress distribution.

A Model of Strongly Forced Wind Waves

2009 ◽  
Vol 39 (10) ◽  
pp. 2502-2522 ◽  
Author(s):  
Alexey V. Fedorov ◽  
W. Kendall Melville
Keyword(s):  
Wind Stress ◽  
Wave Breaking ◽  
Wind Waves ◽  
Surface Wind ◽  
Finite Width ◽  
Hydraulic Jumps ◽  
Turbulent Layer ◽  
Near Surface ◽  
Layer Interface ◽  
Forced Waves

Abstract A model of surface waves generated on deep water by strong winds is proposed. A two-layer approximation is adopted, in which a shallow turbulent layer overlies the lower, infinitely deep layer. The dynamics of the upper layer, which is directly exposed to the wind, are nonlinear and coupled to the linear dynamics in the deep fluid. The authors demonstrate that in such a system there exist steady wave solutions characterized by confined regions of wave breaking alternating with relatively long intervals where the wave profiles change monotonically. In the former regions the flow is decelerated; in the latter it is accelerated. The regions of breaking are akin to hydraulic jumps of finite width necessary to join the smooth “interior” flows and have periodic waves. In contrast to classical hydraulic jumps, the strongly forced waves lose both energy and momentum across the jumps. The flow in the upper layer is driven by the balance between the wind stress at the surface, the turbulent drag applied at the layer interface, and the wave drag induced at the layer interface by quasi-steady breaking waves. Propagating in the downwind direction, the strongly forced waves significantly modify the flow in both layers, lead to enhanced turbulence, and reduce the speed of the near-surface flow. According to this model, a large fraction of the work done by the surface wind stress on the ocean in high winds may go directly into wave breaking and surface turbulence.

scholarly journals Residual Stress Measurement of Shot-Peened Steel Rings by Barkhausen Noise, ESPI Hole-Drilling and X-Ray Diffraction

2014 ◽  
Vol 996 ◽  
pp. 380-385 ◽  
Author(s):  
Theo J. Rickert ◽  
James J. Thomas ◽  
Lasse Suominen
Keyword(s):  
Stress Measurement ◽  
Nondestructive Method ◽  
Fatigue Properties ◽  
Hole Drilling ◽  
Barkhausen Noise ◽  
Surface Zone ◽  
Near Surface ◽  
Generate Surface ◽  
Noise Measurements ◽  
Quantitative Stress

Shot-Peening is used to generate surface-near compressive residual stresses in final shape parts, usually to improve their fatigue properties. The success of the process can be checked in different ways. XRD and Hole-Drilling determine quantitative stress depth profiles in specific locations. Barkhausen noise measurements evaluate a near-surface zone in real-time and can cover large areas quickly. It is a fully nondestructive method. This study compares ESPI Hole-Drilling, which is a very fast technique, and XRD, which is very precise but slower, to Barkhausen Noise results for the case of three steel rings shot-peened with different intensities.

scholarly journals A numerical creep analysis on the interastion of twin parallel edge cracks in finite width plate under tension

2014 ◽  
Vol 18 (suppl.1) ◽  
pp. 159-168 ◽  
Author(s):  
Marko Katinic ◽  
Drazan Kozak ◽  
Mirko Pavisic ◽  
Pejo Konjatic
Keyword(s):  
Width Ratio ◽  
Multiple Cracks ◽  
Finite Width ◽  
Crack Interaction ◽  
Distance Ratio ◽  
Parallel Edge ◽  
Linear Elastic ◽  
Creep Analysis ◽  
Edge Cracks ◽  
Creep Regime

In many practical situations, high-temperature structures and components contain more than one crack. An interaction of such multiple cracks has significant influence on the service life of structures and components. In this paper, the interaction of two identical parallel edge cracks in a finite plate subjected to the remote tension is numerically analyzed. The results show that interaction effect of multiple cracks at creep regime is obviously greater than at linear elastic regime. The intensity of creep crack interaction increases with increasing creep exponent m. The crack intensity and the crack interaction limit at creep regime depend on crack distance ratio d/a, crack width ratio a/W and creep exponent m.

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