Treatment of residual stress in failure assessment procedure

The effect of residual stress on component failure has been investigated using the distributions from current failure assessment procedures, and a residual stress profile simple to apply with less conservatism has been proposed for the weld geometries of T plate and tubular T joint. The stress intensity factors SIFs in the two weld geometries under various types of loads have been calculated using the Green s function method. The Green s functions were determined not only for the T plate but also for the tubular T joint with the built in ends. The use of a linear bending stress profile, derived from an analysis of measured residual stress distributions in T plate and tubular T joints, has been examined. The profile was validated with experimentally measured residual stress distributions in two materials, a high strength and medium strength ferritic steel and two geometries, a T plate joint and a tubular T joint for crack lengths up to half the plate or pipe thickness. Whereas the recommended residual stress distributions are geometry and material specific, it is shown that a simplified linear bending profile provides a possible guideline, applicable to a range of materials and geometries, where detailed information on weld procedures or residual stress profiles are unavailabl

Effect of residual stress on high temperature deformation in a weld stainless steel

This paper considers the measurement of residual stresses induced by mechanical loading in a weld Type 347 stainless steel. The work is based in part on an ongoing Round Robin collaborative effort by the Versailles Agreement on Materials and Standards, Technical Working Area 31, VAMAS TWA 31 working on Crack Growth of Components Containing Residual Stresses . The specific objective of the work at Imperial College London and HMI, Berlin is to examine how residual stresses and prior straining and subsequent relaxation at high temperature contribute to creep crack initiation and growth for steels relevant to power plant applications. Tensile residual stresses have been introduced in the weld by pre compression and neutron diffraction measurements have been carried out before and after stress relaxation at 650 oC. Significant relaxation of the residual stresses has been observed, in agreement with earlier work on a stainless steel. Preliminary results suggest that the strains local to the crack drop by over 60 after 1000 h relaxation at 650 oC for the weld steel. The results have been compared with finite element studies of elastic plastic pre compression and stress relaxation due to cree

A novel manufacturing process and validated predictive model for high strength and low residual stresses in extra large 7xxx panels

A novel manufacturing process, enabling the production of high quality i.e. with low and controllable residual stress RS distributions and good mechanical properties T section 7xxx panels, has been established. This process provides a solution to residual stress induced distortion problems, which greatly concerns a range of industries, especially the aircraft industry. This process consists of three sequential steps water quenching WQ , cold rolling CR and constrained ageing CA . The effectiveness of this process was experimentally verified through applying this process to laboratory sized 7050 T section panels. The RS was measured by neutron diffraction and X ray techniques, in addition to deflections and hardness at each processing stage. An integrated Finite Element FE model, including all three steps, was developed to simulate this manufacturing process and predict both the RS and the final strength distributions. It has been concluded that this novel process can effectively reduce the residual stresses from 300 amp; 8239;MPa to within 100 amp; 8239;MPa and produce T section panels with required mechanical properties i.e. hardness 159 amp; 8239;HV10 . A cold rolling level of 1.5 was found most appropriate. The residual stress and yield strength distributions were accurately predicted by FE, providing a valuable prediction tool to process optimization for industrial application

Correction to Residual stress relaxation in HFMI amp; 8209;treated fillet welds after single overload peaks

The article Residual stress relaxation in HFMI treated fillet welds after single overload peaks, written by Jan Schubnell, Eva Carl, Majid Farajian, Stefanos Gkatzogiannis, Peter Knödel, Thomas Ummenhofer, Robert Wimpory and Hamdollah Eslami, was originally published Online First without Open Access. After publication in volume 64, issue 6, page 1107 1117 the author decided to opt for Open Choice and to make the article an Open Access publication. Therefore, the copyright of the article has been changed to The Author s 2020 and the article is forthwith distributed under the terms of the Creative Commons Attribution Attribution 4. 0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author s and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http creativecommons.org licenses by 4.

Residual Lattice Strain and Phase Distribution in Ti 6Al 4V Produced by Electron Beam Melting

Residual stress strain and microstructure used in additively manufactured material are strongly dependent on process parameter combination. With the aim to better understand and correlate process parameters used in electron beam melting EBM of Ti 6Al 4V with resulting phase distributions and residual stress strains, extensive experimental work has been performed. A large number of polycrystalline Ti 6Al 4V specimens were produced with different optimized EBM process parameter combinations. These specimens were post sequentially studied by using high energy X ray and neutron diffraction. In addition, visible light microscopy, scanning electron microscopy SEM and electron backscattered diffraction EBSD studies were performed and linked to the other findings. Results show that the influence of scan speed and offset focus on resulting residual strain in a fully dense sample was not significant. In contrast to some previous literature, a uniform and Ti phase distribution was found in all investigated specimens. Furthermore, no strong strain variations along the build direction with respect to the deposition were found. The magnitude of strain in and phase show some variations both in the build plane and along the build direction, which seemed to correlate with the size of the primary grains. However, no relation was found between measured residual strains in and phase. Large primary grains and texture appear to have a strong effect on X ray based stress results with relatively small beam size, therefore it is suggested to use a large beam for representative bulk measurements and also to consider the prior grain size in experimental planning, as well as for mathematical modellin

Knowledge acquisition and research evidence in autism:researcher and practitioner perspectives and engagement

Background: Government policy and national practice guidelines have created an increasing need for autism services to adopt an evidence-based practice approach. However, a gap continues to exist between research evidence and its application. This study investigated the difference between autism researchers and practitioners in their methods of acquiring knowledge. Methods: In a questionnaire study, 261 practitioners and 422 researchers reported on the methods they use and perceive to be beneficial for increasing research access and knowledge. They also reported on their level of engagement with members of the other professional community. Results: Researchers and practitioners reported different methods used to access information. Each group, however, had similar overall priorities regarding access to research information. While researchers endorsed the use of academic journals significantly more often than practitioners, both groups included academic journals in their top three choices. The groups differed in the levels of engagement they reported; researchers indicated they were more engaged with practitioners than vice versa. Conclusions: Comparison of researcher and practitioner preferences led to several recommendations to improve knowledge sharing and translation, including enhancing access to original research publications, facilitating informal networking opportunities and the development of proposals for the inclusion of practitioners throughout the research process

THE EFFECT OF RESIDUAL STRESS AND MICROSTRUCTURE ON DISTORTION IN THIN WELDED STEEL PLATES

ABSTRACT The current trend in ship construction is to reduce the thickness of the ship panels, in order to minimize weight and maximize vessel speed. The ship panels of interest consist of 4 mm thick butt welded plates. This reduction in panel thickness may lead to excessive plate distortion during welding, resulting in significant additional costs during assembly. A ferritic-pearlitic DH-36 steel is used, in which phase transformations during welding may affect the distortion and stress states observed. Two large plates, representative of ship panels, have been butt welded using a metal inert gas (MIG) process. The temperature histories have been recorded during welding and the resulting distortion profile has been obtained using digital photography. Neutron diffraction measurements have been performed to determine the residual stress state in the plates before welding, due to e.g. processing and laser cutting, and after butt welding of the plates. Reference matchsticks from the weld, heat affected zone (HAZ) and parent plate have been taken from similar locations in nominally identical plates and measured to obtain the strain/stress free lattice parameter, a 0 . A Rietveld analysis has been performed on the diffraction data. Post welding, hardness surveys have indicated the microstructural variation in the weld, parent plate and HAZ. Results from these on-going studies are presented which identify the key factors responsible for thin plate distortion

Measuring Reciprocity in High Functioning Children and Adolescents with Autism Spectrum Disorders

Few instruments have been developed that measure impairments in reciprocity, a defining feature of autism. We introduce a new test assessing the quality of reciprocal behaviour: the interactive drawing test (IDT). Children and adolescents (n = 49) with and without high functioning autism spectrum disorders (HFASD) were invited to collaborate with an experimenter in making a joint drawing. Within both groups the performance on collaborative reciprocity improved with age. However, compared to the control group, HFASD participants showed less collaborative and more basic reciprocal behaviour and preferred to draw their own objects. They were less tolerant of the experimenter’s input as well. Performance on the IDT was independent of estimated verbal IQ. Reciprocal behaviour in self-initiated objects corresponded with more parental reported autistic traits, while reciprocal behaviour in other-initiated objects corresponded with less autistic traits. The findings of this study suggest that IDT is a promising instrument to assess reciprocity