IMPROVEMENT OF METHODS OF TECHNICAL DIAGNOSIS OF PASSENGER RAILWAY CARS

Extension of the service life of a particular passenger railway car can be considered fully justified only if it is justified by the results of scientific and experimental research and approved by the relevant administrative documents of Ukrzaliznytsia the service life limit for wagons of this type. The existing method of technical diagnostics of passenger railway cars does not allow to fully assess the probability of extension of the service life of the car, because it does not take into account the peculiarities of damage to structural elements during operation. In the article the sequence of research of stresses in elements of a frame of a body of the passenger car of construction of KVN on the basis of standard tests is considered. The task of the study is to determine the sequence of calculation of stresses in the frame elements of the passenger car body of KСР (Kryukiv Carriage Plant) with a service life exceeding 41 years from the date of manufacture to assess strength and fatigue resistance by technical diagnostics and standard tests. It is concluded that the condition of the load-bearing metal structures of cars after long operation does not approach the limit. The residual resource was set at one of the minimum calculated values. If the results of calculations show that the resource is exhausted, the residual service life is determined by the results of bench tests for fatigue. The obtained practical and theoretical results make it possible to extend the service life of cars beyond that set by the manufacturer.

Stochastic Time-Dependent Deterioration Models for Estimating Residual Service Life of Offshore Jacket-Type Platforms

This paper presents deterioration models for maintenance planning of offshore jacket platform based on two methods: i) stochastic Markov-chain based model and ii) stochastic-mechanistic deterioration models based on steel corrosion rates. Markov-chain models require the estimation of transition probability matrix (TPM), which is typically derived from the inspection data. The global structural health condition of the jacket is computed based on the condition of individual elements and their criticality in terms of failure consequence. The criticality factors are established based on nonlinear static redundancy analyses. This method can model deterioration when routine inspection records of jacket members are available. When there is scarcity of inspection records, stochastic-mechanistic deterioration modeling approach can be used. Monte-Carlo simulations with established corrosion wastage models are utilized to estimate the time-dependent deterioration of jacket legs, horizontal and diagonal bracings in splash and immersion zones. This method is proposed when there is scarcity of inspection records. The deterioration models are further utilized to predict the timing for Maintenance, Repair and Rehabilitation (MRR) actions, and estimate the residual service life of the jacket platform. This study demonstrates the application of the proposed deterioration modeling approaches with a case study of a typical 4-legged offshore jacket platform.

Minimality of SRPT Networks With Resource Sharing

A general multi-resource network with users requiring service from a number of shared resources simultaneously is considered. It is demonstrated that the Shortest Remaining Processing Time (SRPT) service protocol minimizes, in a suitable sense, the system resource idleness with respect to customers with residual service times not greater than any threshold value on every network route. Our arguments are pathwise, with no assumptions on the model stochastic primitives and the network topology.

Fatigue Models Based on Real Load Spectra and Corrected S-N Curve for Estimating the Residual Service Life of the Remanufactured Excavator Beam

To more accurately predict the residual fatigue cycles and estimate the service life of the remanufactured excavator, the fatigue models integrating the corrected S-N curve, the RFC algorithm, the FEA model, and the mechanism dynamic model are established depending on the real load spectra under experimental working conditions and the corrected S-N curve of the beam metal remanufactured with the welding process. Depending on the test data of the unidirectional stress history and the servo displacements of the major cylinders, the mechanism dynamic model was first established to illustrate the real load spectra applied on the pivots of the working beam. The load spectra are further used in the finite element analysis (FEA) model to obtain the stress contours of the beam relevant to the sampling time, which is the stress spectra at any nodes on the beam in theory. Subsequently, the rain flow counting (RFC) algorithm based on the dual parameters of the cyclic stress amplitude and mean is established to provide the frequency spectra in the longevity region on the beam. Furthermore, due to the fatigue property changes of the beam metal remanufactured with the welding process, its S-N curve is corrected based on the detail fatigue rating (DFR) method to compute the stress cycles at each stress level on the crisis nodes. Finally, the total stress cycles that can be burdened by the remanufactured beam is computed under the Miner’s linear fatigue cumulative criterion. The total number of stress cycles is eventually converted to the fatigue and service life depending on the proportion of the sampling time under relevant working conditions. The results show that integrated fatigue models provide a practical approach to enhancing the accuracy of the estimation on the residual service life of the remanufactured excavator beam. It is significant for improving the reliability and safety of the remanufactured excavator.

Residual service life estimation of bridges

<p>While concrete structures perform well in many situations, lack of durability has emerged as a significant issue for asset owners. A review of past bridge failures was done to identify the most probable causes of bridge failures. This study has tended to focus on current models used for estimating the time to deterioration of concrete bridges instigated by Chloride ingress and Fatigue. Subsequently, mathematical modelling of the best-suited deterioration model is done to arrive at the residual life of two existing bridges. This work has highlighted high variability in the parameters used to describe the durability related properties of in-situ aged concrete. A realistic residual life assessment can be achieved by correct evaluation of these parameters by periodic testing of bridge samples</p>

Residual service life of erbium-modified AM50 magnesium alloy under corrosion and stress environment

Magnesium alloy will decrease strength with corrosion in use, thus affecting their service life. Service life as a structural material under stress and corrosion is one focus of the magnesium alloy used as structural material, and how to improve the residual service life of magnesium alloy is an important scientific issue. The X-ray diffraction, scanning electron microscopy, and slow strain rate tensile (SSRT) tests are used to study the residual service life of erbium (Er) effect in the AM50 magnesium alloy in air, distilled water, and NaCl solution. The results show that after rare earth Er addition to the AM50, the white granular Al3Er intermetallic compound was formed. With Er content increasing, the quantity of Al3Er phase was increased and the volume of β-Mg17Al12 phase was decreased. The SSRT results show that residual service life ratio increased with the Er addition compare with no Er alloy in distilled water. However, in 3.5% NaCl solution, 0.5% Er alloy shows the best service life. Moreover, Er addition does not change the alloy fracture mode, which remains quasi-cleavage. The main cause of the decline in service life in magnesium alloys is the change in surface morphology owing to the pitting corrosion nucleation and growth, which affects the stress distribution of the sample. The mechanism of film cracking plays a major role in the fracture process with the Er increased to change the surface morphologies.

The relocation of a heritage bridge

<p>This paper describes the history of a heritage bridge in Amsterdam (The Netherlands) and the efforts made for the relocation of this bridge. Investigations were made to determine the structural integrity of the original elements and structural assessments were done to find the remaining capacity for future use. The Ultimate Limit State for the original elements was investigated. Lateral stability was checked and based on the historical use and the required future use the fatigue loads were calculated for the different cross sections and for critical connections. These calculations showed that a required residual service life of 30 years after relocation was technically possible for this bridge. Some pros and cons for the re-use of this bridge are also discussed.</p>