Data Reduction And Error Analysis For The Physical Sciences

Three Types of Interaction

http://doras.dcu.ie/17607/1/Review_of_residual_stresses-Final.pdf

Methods of measuring residual stresses in components

Our safety, comfort and peace of mind are heavily dependent upon our capability to prevent, predict or postpone the failure of components and structures on the basis of sound physical principles While the external loadings acting on a material or component are clearly important, There are other contributory factors including unfavourable materials microstructure, pre-existing defects and residual stresses Residual stresses can add to, or subtract from, the applied stresses and so when unexpected failure occurs it is often because residual stresses have combined critically with the applied stresses, or because together with the presence of undetected defects they have dangerously lowered the applied stress at which failure will occur Consequently it is important that the origins of residual stress are understood, opportunities for removing harmful or introducing beneficial residual stresses recognized, their evolution in-service predicted, their influence on failure processes understood and safe structural integrity assessments made, so as to either remove the part prior to failure, or to take corrective action to extend life This paper reviews the progress in these aspects in the light of the basic failure mechanisms

/pdf/residual-stress-and-its-role-in-failure-2ld6sd4vw6.pdf

Residual stress and its role in failure

As the COVID-19 pandemic upended the 2019–2020 school year, education systems scrambled to meet the needs of students and families with little available data on how school closures may impact learn...

https://journals.sagepub.com/doi/pdf/10.3102/0013189X20965918

Projecting the Potential Impact of COVID-19 School Closures on Academic Achievement.

Residual stress, stress relief, and inhomogeneity in aluminum plate

The high cycle fatigue performance of 7050-T7451 aluminum was investigated for untreated as-machined, laser peened, and shot peened conditions Constant amplitude, smooth (Kt = 1) fatigue tests were conducted in four-point bending at a stress ratio of R = 01 Results show that laser peening induces a layer of compressive residual stress more than three times deeper than for shot peening Both treatments significantly increase fatigue performance At a moderate level of stress, peened specimens outlast as-machined specimens, by a factor of 79 for laser peening and 29 for shot peening At higher stress, life improvements are lower, a factor of 33 for laser peening and 21 for shot peening At a 100,000-cycle lifetime, fatigue strength of laser peened specimens is 41% higher than as-machined specimens and the fatigue strength of shot peened specimens 30% higher than as-machined A form of pitting was noted on the laser peened surfaces and follow-on tests assessed the effects of the pitting on fatigue performance Results indicate that the pitting does not significantly influence fatigue performance

The Effects of Laser Peening and Shot Peening on High Cycle Fatigue in 7050-T7451 Aluminum Alloy

The effects of laser peening and shot peening on fretting fatigue in Ti–6Al–4V coupons

This article uses fixed effects models to estimate differences in contemporaneous and downstream academic outcomes for students who take courses virtually and face-to-face—both for initial attempts...

/pdf/online-learning-offline-outcomes-online-course-taking-and-s3slp9f796.pdf

Online Learning, Offline Outcomes: Online Course-Taking and High School Student Performance.

Measuring the spatial variation of residual stresses often requires the solution of an elastic inverse problem such as a Volterra equation. Using a maximum likelihood estimate (least squares fit), a series expansion for the spatial distribution of stress or underlying eigenstrain can be an effective solution. Measurement techniques that use a series expansion inverse include incremental slitting (crack compliance), incremental hole drilling, a modified Sach's method, and others. This paper presents a comprehensive uncertainty analysis and order selection methodology, with detailed development for the slitting method. For the uncertainties in the calculated stresses caused by errors in the measured data, an analytical formulation is presented which includes the usually ignored but important contribution of covariances between the fit parameters. Using Monte Carlo numerical simulations, it is additionally demonstrated that accurate uncertainty estimates require the estimation of model error, the ability of the chosen series expansion to fit the actual stress variation. An original method for estimating model error for a series expansion inverse solution is presented. Finally, it is demonstrated that an optimal order for the series expansion can usually be chosen by minimizing the estimated uncertainty in the calculated stresses.

/pdf/uncertainty-model-error-and-order-selection-for-series-1155pseua2.pdf

Michael R. Hill

Papers

Residual stress, stress relief, and inhomogeneity in aluminum plate

The Effects of Laser Peening and Shot Peening on High Cycle Fatigue in 7050-T7451 Aluminum Alloy

The effects of laser peening and shot peening on fretting fatigue in Ti–6Al–4V coupons

Online Learning, Offline Outcomes: Online Course-Taking and High School Student Performance.

Uncertainty, Model Error, and Order Selection for Series-Expanded, Residual-Stress Inverse Solutions