Slip Strips Research Articles

Study of the microstructure of metastable austenitic chromium manganese steel 14Kh15G9ND by optical and electron microscopy

Modern metallography being a complex of qualitative and quantitative methods is widely used to analyze the microstructure of metal alloys. We present the results of studying the microstructure of austenitic chromium-manganese steel 14Kh15G9ND by optical and electron microscopy. The method of etching and the reagent, the most suitable for this steel grade, which provide identification of the main structural and phase components (austenite, twins, slip strips) of the steel were selected using the existing techniques. The results of optical and scanning microscopy of the samples deformed with a different degree of cold plastic deformation were compared with each other. It is shown that electrochemical etching in an aqueous solution of chromium anhydride should be used for qualitative determination of the steel microstructure. Optimal parameters of the current density and voltage were also determined. The results obtained can be used for optical microscopy of chromium-manganese steels, as well as for a more complete study of the dislocation structures present in them using scanning microscopy.

Study of Tensile Deformation and Damage Law in Undermatching X80 Pipeline Steel Welded Joints

This study used a digital imaging technique (DIC) to obtain the strain distribution at various locations in undermatching X80 pipe girth-weld joints under uniaxial tensile loading. In addition, the microstructure characteristics and deformation patterns in different regions were analyzed by scanning electron microscopy (SEM). The results showed that there was strain heterogeneity between the various regions of the welded joint. Strain concentration existed only in the 12.8 mm base metal heat-affected zone (HAZ) and only in the elastic deformation stage. There was strain concentration in the weld metal (WM) and both sides of the HAZ close to the near-fracture stage, and the maximum deformation was in the WM. When εM = 12.2%, the KC was 6.27 and the KF was 1.73, and the KF was 113% and 152% of the KC and the KG, respectively. The large number of slip strips generated indicated serious damage in the WM near the fracture stage. In the elastic deformation stage, the strain concentration of the N1 HAZ was caused by the softened ferrite. The maximum deformation of the WM near the fracture stage was caused by the large grain size and the non-uniform martensite–austenite (M–A) islands, which may also lead to better local toughness of the cover weld and further affect the fracture mechanism of the welded joint.

Microstructure Characteristic and Fatigue Damage Behaviors of 2060 Al-Li Alloy Thin Plate

The microstructure characteristic, fatigue damage behaviours and evolution of microstructure during the fatigue testing of 2060 Al-Li alloy thin plate were studied by fatigue tester equipped with in-situ observation device, OM, EBSD, SEM and TEM. The results show that recrystallized grains with irregularity shape and large size are observed, the Goss and Cube texture are the mainly types, abundant of T1 with size of 50~60nm are found in grains. During axial loaded fatigue testing, a crack initiates from the edge of sample and extend into grain along the direction with maximum Schmid factor. When the crack reaches and crosses the first grain boundary, the extending direction deflects from 45° degree to perpendicular with loading direction, and propagates along this direction till the sample quickly fracture. A large size deformation region contains numerous slip strips around the crack tip during the initiation and extending process is observed. The dislocations cut across the T1 precipitates located in grains during deformation, and release the stress concentration on the crack tip. The fatigue crack extends across the grains with serrated shape can result from the big orientation difference of grains and easy screwed T1 precipitates.

Intelligent Transport System – RRUKA Special Issue ‐ Editorial

The Rail Research UK Association (RRUKA) was formed in 2010 with the aim of providing a forum in which industry and academia can come together to identify and deliver fundamental research which will benefit the whole railway system. There are currently 51 institutional members and over 300 RRUKA researchers who have the expertise and skills to develop new concepts to address long standing issues and explore emerging opportunities that the industry is keen to exploit. The association fulfils its objectives through a number of activities, including networking events, conferences, thematic workshops, and facilitating the delivery of academic research. This IET Intelligent Transport System Special Issue presents a selection of research papers presented at the third RRUKA annual conference held in London in 2014. The conference showcased the activities of the members, who presented their latest work both in the plenary speaking sessions, and also in the Blue Sky Village where industry and academic colleagues exchanged ideas and concepts for the next generation of cutting edge solutions. Mark Carne, Chief Executive of Network Rail, set out in his keynote to address the challenges facing the railway, and outlined the future vision of an entirely digitally- enabled railway system. In this future vision the railway system will fully embrace and adopt emerging digital technology in all aspects of its operation, delivering benefits for the passenger, operators, maintainers, and renewals and upgrades. The papers published in this issue cover a broad spectrum of research within the scope of ITS. System wide issues are addressed by the papers on: the whole-system life cost analysis method for railway infrastructure management; the geospatial safety risk model; and electromagnetic compatibility between rolling stock and the surrounding systems. Optimisation of the railway system and its operation is tackled in papers which address: the turnaround arrangements at terminal stations; delay management with minimal energy consumption; and the use of remote condition monitoring for improved wheelset management. The paper examining how passengers have dealt with the increased amount of counter-terrorism measures which are now implemented within stations, and also the paper which addressed how the system is coping with an aging passenger population, particular relating to slips trips and falls, provide relevant research into human factors. Some of the most interesting and creditable work that is undertaken by RRUKA members and supported by industry partners is published in this issue. We hope that you find the papers of value. More information on the association and how you can engage can be found on our website www.rruka.org.uk.

Changes in falls prevention policies in hospital in England and Wales

in 2007, the National Patient Safety Agency (NPSA) published 'Slips trips and falls in hospital' and 'Using bedrails safely and effectively'. this observational study aimed to identify changes in local policies in hospitals in England and Wales following these publications. policies in place during 2006 and 2009 were requested from 50 randomly selected acute hospital trusts and their content was categorised by a single reviewer using defined criteria. thirty-seven trusts responded. Trusts with an inpatient falls prevention policy increased from 65 to 100%, the use of unreferenced numerical falls risk assessments reduced from 50 to 19%, and trusts with a bedrail policy increased from 49 to 89%. It was concerning to find that by 2009 advice on clinical checks after a fall was available in only 51% of trusts, and only 46% of trust policies included specific guidance on avoiding bedrail entrapment gaps. the observed changes in policy content were likely to have been influenced not only by the NPSA publications but also by contemporaneous publications from the Royal College of Physicians' National Audit of Falls and Bone Health, and the Medicines and Healthcare products Regulatory Agency. Most areas of local policy indicated substantial improvement, but further improvements are required.

Circumstances of slips trips and falls among Hospital workers

A case follow-back study was conducted to better describe the circumstances experienced by hospital workers who had slipped, tripped and/or fallen (STF). One hundred 53 healthcare workers, who reported a...

One-dimensional resistive states in quasi-two-dimensional superconductors: Experiment and theory

We investigate competition between one- and two-dimensional topological excitations---phase slips and vortices---in the formation of resistive states in quasi-two-dimensional superconductors in a wide temperature range below the mean-field transition temperature ${T}_{C0}$. The widths $w=100\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$ of our ultrathin NbN samples are substantially larger than the Ginzburg-Landau coherence length $\ensuremath{\xi}=4\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$, and the fluctuation resistivity above ${T}_{C0}$ has a two-dimensional character. However, our data show that the resistivity below ${T}_{C0}$ is produced by one-dimensional excitations---thermally activated phase slip strips (PSSs) overlapping the sample cross section. We also determine the scaling phase diagram, which shows that even in wider samples the PSS contribution dominates over vortices in a substantial region of current and/or temperature variations. Measuring the resistivity within 7 orders of magnitude, we find that the quantum phase slips can only be essential below this level.

Effect of prestraining on the behavior of hydrogen in structural steel

We study the influence of cold working on the behavior of hydrogen in 0.25C-1Cr-1Mn-1Si-1Ni high-strength low-carbon low-alloy steel after various types of thermal treatment. The results of measuring the permeation of hydrogen are used to determine the lattice diffusion coefficient, the efficiency of trapping of hydrogen, and the formation of internal cracks for specimens deformed by shot peening, cyclic tension-compression, and uniform tension. The mode of deformation does not affect the value of the lattice diffusion coefficient for the bainite structure. All types of deformation increase the efficiency of traps corresponding to the deformation of the bainite lattice by cold working. The type of deformation specifies the morphology of internal hydrogen-induced cracks along the local slip strips in the metal.

Craniofacial Injuries From Slip, Trip, and Fall Accidents of Children

Slips, trips (STs), and falls are frequent events in childhood. As a child is likely to impact head-first in these events, craniofacial injuries are the most common trauma. We retrospectively surveyed our experience with pediatric craniofacial injuries and investigated the distributions of wound type and injury site, severity, and mechanism. A total of 750 children sustaining craniofacial injuries resulting from STs and falls were enrolled in this study. Facial and cranial areas were delimited by an imaginary line extending between the ears and across the eyebrows. Soft-tissue injuries were classified into laceration, contusion, and abrasion. The Glasgow Coma Scale was used to assess the severity of brain injury. Peak incidence of ST-type childhood craniofacial injury occurred at toddler age, whereas falls tended to occur when the children were younger than 1 year old; most of the patients were preschool. The home was the scene for 73% of the STs and 86% of the falls. Lacerations occurred more often in STs (67% vs. 25%), whereas contusions more often resulted from falls (64% vs. 27%). Most of the injuries were to the anterior head with a T-shaped distribution; however, over one third (37%) of the contusions were to the posterior area. Brain injury was absent or only mild in 98% of craniofacial injuries. Falls resulted in a significantly higher incidence of moderate-severe brain injury relative to STs. Childhood craniofacial injuries resulting from STs are more prevalent than are those that were sustained in falls; however, the latter is associated with greater trauma morbidity. The incidence of childhood craniofacial injury appears to be associated with the level of development irrespective of event type. The home is a potentially dangerous environment for children, especially during the preschool years. Padding the hard, acutely angled surfaces of housing structures and furniture around children's activity zones is an effective method of reducing the risk of childhood craniofacial trauma. Serious or fatal head injuries will rarely occur as the result of a fall from furniture or stairs at home.

In situ SEM and AFM observations of surface morphology of plasma nitrided layer of austenitic stainless steel

Surface morphology changes of the layer on austenitic stainless steel plasma nitrided for different times at low temperature (400–420°C) were studied by in situ SEM observation. The results show that nitriding does not modify the annealed twin, grain size and shape. However, when for a process time of 240 min, the strain in the nitrided layer (γN) resulting from supersaturating nitrogen can be great enough to initiate slip system activity so that a high slip band density appears on the layer surface. Obvious surface convex occurs in annealed twin band and matrix zones, which indicates that the greater slip amount has been produced in these zones. Local convex surface zones or differences in magnitude of the amount of slip in various zones can be attributed to the grain orientation relative to the direction of the compressive stress in the layer. The presence of slip bands and the occurrence of convex surface zones indicate that the planar compressive stress in the nitrided layer reaches the planar yield strength, so that a surface yield phenomenon occurs. Atomic probe microscopy was employed to study the surface topography. The mean microroughness value Ra was 19·851 nm over a 15 × 15 μm2 area of AFM image that included slip strips. The spacing between the slip strips was of the order 100 nm, and the slip step of order 10 nm.

Development of secondary plastic strips near tensile cracks in the plate

We suggest a method for the solution of the elastoplastic problem of biaxial tension-compression of a thin cracked plate under the assumption that plastic strains at each tip of the crack are localized along three slip lines. The plastic zone is simulated by three inclined slip strips at the tips of the crack. It is assumed that the material of the plate is absolutely elastoplastic and the yield criterion is satisfied along the slip lines. The strips lying on the continuation of the crack are simulated by segments of discontinuity of normal stresses, while the other strips are simulated by segments of discontinuity of tangential stresses Thus, the elastoplastic problem under consideration is reduced to the boundary-value problem of the linear theory of elasticity for a body weakened by branched cuts with unknown lengths and orientations of side branches. These parameters are determined in the process of numerical solution of the problem by the method of singular integral equations. Numerical results are presented for the semiinfinite plane with edge crack and under the conditions of uniform tension at infinity. We present numerical values of some parameters of nonlinear fracture mechanics, such as crack tip opening displacement and lengths and angles of inclination of plastic strips, for various combinations of the components of external load.

Formation of wavy slip bands in AgCl crystals at low temperatures

In the temperature range of approximately 110–130 K the transition of the planar slip to the wavy one occurs in AgCl crystals. The transition manifests itself by substantial shortening of originally long and straight slip traces on the top oriented surface of the samples. The wavy slip bands (in the bulk of the sample) are created by mutual association of the narrow, straight and long slip strips.