The acousto-ultrasonic approach

The nature and underlying rationale of the acousto-ultrasonic approach is reviewed, needed advanced signal analysis and evaluation methods suggested, and application potentials discussed. Acousto-ultrasonics is an NDE technique combining aspects of acoustic emission methodology with ultrasonic simulation of stress waves. This approach uses analysis of simulated stress waves for detecting and mapping variations of mechanical properties. Unlike most NDE, acousto-ultrasonics is less concerned with flaw detection than with the assessment of the collective effects of various flaws and material anomalies. Acousto-ultrasonics has been applied chiefly to laminated and filament-wound fiber reinforced composites. It has been used to assess the significant strength and toughness reducing effects that can be wrought by combinations of essentially minor flaws and diffuse flaw populations. Acousto-ultrasonics assesses integrated defect states and the resultant variations in properties such as tensile, shear, and flexural strengths and fracture resistance. Matrix cure state, porosity, fiber orientation, fiber volume fraction, fiber-matrix bonding, and interlaminar bond quality are underlying factors

Defect tolerance of friction stir welds in DH36 steel

Friction stir welding of steel is in the early stages of development. The aim to commercialise this process creates a trade-off between welding time, cost and quality of the joint produced. Therefore, it becomes critical to analyse the lower quality bound of steel friction stir welds in conventional square edge butt welding configuration. Work has been undertaken to evaluate the microstructure and fatigue performance of 6 mm thick DH36 steel plates friction stir welded with sub-optimal process conditions, resulting in the development of embedded and surface breaking flaws. The defective weldments were characterised to understand the nature of the flaws and a programme of mechanical testing was undertaken (including fatigue assessment) to determine the relationship between the flaw geometry, location and weld quality. A number of characteristic flaws were identified and seen to interact with the samples’ fatigue fracture mechanisms. Samples with wormholes at the weld root produced the lowest fatigue performance. Fracture from incomplete fusion paths at the retreating side of the welds’ top surface was seen to correspond to the highest recorded fatigue lives. The work provides an insight into the complex nature of characteristic flaws in steel friction stir welds and their interaction with fatigue behaviour

Reliability based analysis of contact problems

The Batdorf model is modified to include the reduction in shear due to the effect of compressive stresses on the crack face. This new formulation was used to obtain the probability of failure of ceramic components under contact stress conditions. The combined effect of the surface and volume flaws are included in the analysis. Due to the nature of the fracture of brittle materials under compressive loading, the component is modeled as a series system in order to establish bounds on the probability of failure

Why Originalism Won’t Die - Common Mistakes in Competing Theories of Judicial Interpretation

In the debate over proper judicial interpretation of the law, the doctrine of Originalism has been subjected to numerous seemingly fatal criticisms. Despite the exposure of flaws that would normally bury a theory, however, Originalism continues to attract tremendous support, seeming to many to be the most sensible theory on offer. This Article examines its resilient appeal (with a particular focus on Scalia’s Textualism). By surveying and identifying the fundamental weaknesses of three of the leading alternatives to Originalism (Popular Will theory, Dworkin’s value theory, and Judicial Minimalism), the Article demonstrates that the heart of Originalism’s appeal rests in its promise of objectivity. The Article also establishes, however, that Originalism suffers from a misguided conception of what objectivity is. All camps in this debate, in fact, suffer from serious misunderstandings of the nature of objectivity

Analysis of fracture damage in silica optical fibers

Microstructured optical fibres (with a periodic transverse microstructure) are of interest since they offer a simple alternative to controlling the index profile of optical waveguides. Although many types of optical fibres and cables have been developed to meet the needs of communications service providers for longterm performance and reliable operation, the brittle nature, aging and fatigue of these fibres, remains to be the key materials issues. The flaws on the surface of fibres caused by processing (drawing) or subsequent assembling make the situation more complex. In this work, experimental investigation and fracture mechanics analysis have been conducted to understand the fracture behavior of these newly developed optical fibres. The results are believed to be useful for design, fabrication and evaluation of optical fibres for a variety of applications

A comparison of single-cycle versus multiple-cycle proof testing strategies

An evaluation of single-cycle and multiple-cycle proof testing (MCPT) strategies for SSME components is described. Data for initial sizes and shapes of actual SSME hardware defects are analyzed statistically. Closed-form estimates of the J-integral for surface flaws are derived with a modified reference stress method. The results of load- and displacement-controlled stable crack growth tests on thin IN-718 plates with deep surface flaws are summarized. A J-resistance curve for the surface-cracked configuration is developed and compared with data from thick compact tension specimens. The potential for further crack growth during large unload/reload cycles is discussed, highlighting conflicting data in the literature. A simple model for ductile crack growth during MCPT based on the J-resistance curve is used to study the potential effects of key variables. The projected changes in the crack size distribution during MCPT depend on the interactions between several key parameters, including the number of proof cycles, the nature of the resistance curve, the initial crack size distribution, the component boundary conditions (load vs. displacement control), and the magnitude of the applied load or displacement. The relative advantages of single-cycle and multiple-cycle proof testing appear to be specific, therefore, to individual component geometry, material, and loading

Infertility problems and mental health symptoms in a community-based sample: depressive symptoms among infertile men, but not women

Most researchers agree that men’s and women’s experiences of infertility are fundamentally different, and impacts upon the nature of psychological distress encountered. However, design flaws, including non-random samples unrepresentative of the general population, compromise many existing studies. Data derived from a random general community sample provides prevalence of current infertility, and permits examination of longitudinal associations between mental health symptoms and infertility among 1,978 participants aged 28-32 years. In the previous 12-months, infertility was experienced by 2.1% and 5.4% partnered men and women. Infertility independently predicted depressive symptomatology in men, and anxiety symptoms among women. Gender differences were sustained, even controlling for prior depression and anxiety. Health professionals are encouraged to proactively enquire about affective symptoms experienced by both women and men with infertility problems