Railway wheel tread damage and axle bending stress – Instrumented wheelset measurements and numerical simulations

A combination of instrumented wheelset measurements and numerical simulations of axle bending stresses is used to investigate the consequences of evolving rolling contact fatigue (RCF) damage on a passenger train wheelset. In a field test campaign, stresses have been monitored using a wheelset with four strain gauges mounted on the axle, while the evolution of wheel tread damage (out-of-roundness) has been measured on regular occasions. The strain signals are post-processed in real time and stress variations are computed. Based on a convolution integral approach, the measured wheel out-of-roundness has been used as input to numerical simulations of vertical dynamic wheelset–track interaction and axle stresses. Simulated and measured axle stresses are compared for cases involving combinations of low or high levels of rail roughness and the measured levels of RCF damage. The study enhances the understanding of how wheel tread damage and track quality influence axle stress amplitudes

Mortality and pulmonary complications in patients undergoing surgery with perioperative SARS-CoV-2 infection: an international cohort study

Background: The impact of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) on postoperative recovery needs to be understood to inform clinical decision making during and after the COVID-19 pandemic. This study reports 30-day mortality and pulmonary complication rates in patients with perioperative SARS-CoV-2 infection. Methods: This international, multicentre, cohort study at 235 hospitals in 24 countries included all patients undergoing surgery who had SARS-CoV-2 infection confirmed within 7 days before or 30 days after surgery. The primary outcome measure was 30-day postoperative mortality and was assessed in all enrolled patients. The main secondary outcome measure was pulmonary complications, defined as pneumonia, acute respiratory distress syndrome, or unexpected postoperative ventilation. Findings: This analysis includes 1128 patients who had surgery between Jan 1 and March 31, 2020, of whom 835 (74·0%) had emergency surgery and 280 (24·8%) had elective surgery. SARS-CoV-2 infection was confirmed preoperatively in 294 (26·1%) patients. 30-day mortality was 23·8% (268 of 1128). Pulmonary complications occurred in 577 (51·2%) of 1128 patients; 30-day mortality in these patients was 38·0% (219 of 577), accounting for 81·7% (219 of 268) of all deaths. In adjusted analyses, 30-day mortality was associated with male sex (odds ratio 1·75 [95% CI 1·28–2·40], p\textless0·0001), age 70 years or older versus younger than 70 years (2·30 [1·65–3·22], p\textless0·0001), American Society of Anesthesiologists grades 3–5 versus grades 1–2 (2·35 [1·57–3·53], p\textless0·0001), malignant versus benign or obstetric diagnosis (1·55 [1·01–2·39], p=0·046), emergency versus elective surgery (1·67 [1·06–2·63], p=0·026), and major versus minor surgery (1·52 [1·01–2·31], p=0·047). Interpretation: Postoperative pulmonary complications occur in half of patients with perioperative SARS-CoV-2 infection and are associated with high mortality. Thresholds for surgery during the COVID-19 pandemic should be higher than during normal practice, particularly in men aged 70 years and older. Consideration should be given for postponing non-urgent procedures and promoting non-operative treatment to delay or avoid the need for surgery. Funding: National Institute for Health Research (NIHR), Association of Coloproctology of Great Britain and Ireland, Bowel and Cancer Research, Bowel Disease Research Foundation, Association of Upper Gastrointestinal Surgeons, British Association of Surgical Oncology, British Gynaecological Cancer Society, European Society of Coloproctology, NIHR Academy, Sarcoma UK, Vascular Society for Great Britain and Ireland, and Yorkshire Cancer Research

Fretting fatigue strength and non-propagation of surface cracks

Components behaviour under alternate loads combined with repeated relative surface motion is one of the open problems in the area of fatigue. The combination of the effects of abrasive and adhesive wear, caused by relative surface sliding and resulting in surface damage, and fatigue, caused by alternated loads in presence of high local stress intensity factors (i.e surface degradation by wear), is called "fretting fatigue". A presence of oxidation phenomenon can also be part of the fretting fatigue process. In the case of the railway wheelsets designed after 2003, there are no records of failures at press-fits because the design rules are based on shape of the transitions (D/d ≥ 1.2) that make the axle transition the most stressed point. However, it is important to analyze the acceptability of defects and micro-cracks at the press-fits in order to correctly interpret fatigue strength considering that micro-scars and micro-cracks are some times detected after fatigue tests for D/d = 1.2. In this paper we analyse the full-scale test results obtained on EA4T axles within the Euraxles project on the basis of detailed FE analyses and a new criterion for prediction non-propagation of cracks under RCF conditions. Predictions are compared with full-scale test experiments on axles with artificial micro-notches at the press-fit

Prediction of axle fatigue life based on field measurements

To facilitate the adoption of a condition-based maintenance approach for railway axles, more knowledge regarding operational loading is needed. In the present work, statistical distributions on axle stresses for revenue vehicles have been derived. To this end, raw strain spectra have been gathered during field measurements using an instrumented telemetry mounted on a powered axle running within the Swedish railway network. Strain spectra are transformed into bending stress spectra which are used to estimate the statistical distributions of axle stresses for different track sections. Both the derived stress spectra and the estimated statistical distributions are used as input to fatigue life analyses. In these analyses, W\uf6hler (stress–cycle) curves estimated for varying axle surface conditions (which can be related to different axle maintenance conditions) are used to predict axle lives. The proposed method allows to rapidly post-process data obtained during field tests, to quantify indications on the health status of track and of the wheelset from these, and to estimate resulting fatigue life. This would aid in asset management by enhanced status characterisation, improved inspection and maintenance planning, and enhanced possibilities to follow-up any non-conformities

Design of a novel, low impact bogie for a freight locomotive

This paper reports on the work being carried out in the Shift2Rail ‘DYNAFREIGHT’ project to develop a novel freight locomotive bogie which will reduce wheel and track wear and run with lower noise than current locomotive bogie designs. This is being achieved by developments in several areas including the use of advanced materials and manufacturing processes and the adoption of passive and mechatronic systems for radial steering of bogies, which will allow improved running performance compared to conventional bogies. In particular, significant reduction of wheel wear and damage, improved traction in curves and reduced resistance to motion in sharp curves will be achieved. The use of noise optimized wheelsets and noise absorbing structure in order to reduce the running gear related noise is also being considered. Monitoring of the most maintenance cost-intensive bogie elements is also being considered in order to contribute to lower life cycle costs and to improve the reliability and availability of the locomotive