Evaluation of crack resistance of welded joints with soft interlayers

Introduction. Welded joints in large-sized metal structures (e.g., in the structures of ship hulls) subject to low-cycle fatigue are considered. The characteristic appearance of soft interlayers, which are significantly plastically deformed under working loads, was noted. Deformation of the metal structure with damage, especially in the form of cracks, reduces the strength and reliability of structural elements and joints. Pre-deformation negatively affects plasticity; therefore, much depends on the residual plasticity of the cracking material. At the same time, with a decrease in residual plasticity, such an important reliability indicator as the resistance of the material to crack propagation — the fracture toughness – decreases. The paper is devoted to the development of a model that includes analytical dependences for assessing the crack resistance of metal structures and their welded joints with soft interlayers according to the crack resistance limit for all crack sizes.Materials and Methods. The theory and methods of linear mechanics of materials destruction, structural-mechanical approach are used. The calculation results were analyzed and compared to the experimental data and other analytical solutions. The numerical experiment was performed for the ferrite-perlite steel grades of 10, 50, 22K, St3sp, etc., widely used in industry, as well as for alloy steels hardened to medium and high strength of 30KhGSA, 37KhN3A, etc. Results. Analytical dependences are obtained for calculating the relative crack resistance limit according to three main known mechanical characteristics of the state of the material of the soft interlayer of the welded joint.Discussion and Conclusions. The results obtained can be used to assess the crack resistance of pre-deformed structural elements and welded joints (including those with soft interlayers) operating under a transverse load. The results of experimental data and analytical calculations are shown in dimensionless form, which enables to obtain invariant results with respect to the fracture toughness limit.

Cultural values, entrepreneurial team structure and performance of SMEs

PurposeThe main objective of this study is to explain the relationship between members' cultural values on structure and performance of the entrepreneurial teams that located in Tehran.Design/methodology/approachData used in this study are collected by a questionnaire distributed among managers and other executive members of SMEs located in Tehran. One hundred and thirty-nine participants completed the questionnaires, and their responses were analyzed using partial least squares technique. Measures showed good convergent and discriminant validity. Furthermore, Cronbach's alpha, as reliability indicator for all measures, is at the acceptable level.FindingsResearch finding shows that all hypothesis supported in Iran contex. Entrepreneurial team members' cultural values have positive and significant effect on the entrepreneurial team structure. Entrepreneurial team members' cultural values have significant effect on the entrepreneurial team performance and also, the structure of the entrepreneurial team has a positive and significant effect on the entrepreneurial team performance.Originality/valueThese studies mostly focused on technical dimensions of entrepreneurial teams and overlooked the cultural values of their members.

RELIABILITY OF WATER TREATMENT FACILITIES ACCORDING TO OPERATING DATA

The centralized water supply system from the water source to the consumer includes 3 main complexes: water intake, water treatment and supply and distribution. The reliability of water supply in the area depends on the reliability of each of these complexes, which, in turn, consist of a number of structures. The paper develops the developed principle of assessing the reliability of water treatment plants (WPP) by quantitative indicators of the quality of treated water. The assessment of the reliability of the current WPP was performed to reflect its work, which implements the "black box" model. That is, some process parameters have one value at the input and other values at the output. The disadvantage of this method is that it is impossible to assess the reliability if the process does not occur. In addition, it is impossible to assess the reliability of the BOC for another set of individual structures. And the advantage is the sufficient simplicity of calculating the reliability indicator. Data on the purification of the Dnieper water at the Kremenchug WPP in terms of turbidity and chromaticity are used. Graphs of average variable indicators of turbidity and chromaticity of Dnieper water at the entrance of the WPP and graphs of exceedances of maximum permissible concentrations of treated water are constructed. The main indicator of reliability for municipal water supply facilities is the coefficient of readiness of KD, and the basic indicators of reliability are the average operating time for failure T and the average recovery time of the TR. The possibility of calculating the coefficients KD downtime and KR readiness in case of exceeding the MPC treated water is shown. After analyzing the graphs of water quality indicators, it was determined that the greatest turbidity and chromaticity of the Dnieper water is observed in the autumn.

Optimization Design of an Efficient Evacuator for Gun Barrels

Evacuators are key components of gun barrels, and their main function is to drain the gunpowder gas remaining in the gun bore from the muzzle by ejection. To design an efficient evacuator for the gun barrels, an optimization model with the mathematical expressions describing the working process of the evacuator was established. The four structural parameters that affect the efficiency of the evacuator, including the volume of the gas storage cylinder chamber, the distance of the nozzle from the muzzle end face, the cross-sectional area of the nozzles and the cross-sectional area of the valves, were optimized. The effective working time and reliability indicator of the optimized evacuator were improved. This work describes a framework for improving the design of highly efficient evacuators on gun barrels.

Calculation integral reliability indicator of the urban electric transport traction electrical equipment

When reliability requirements at the stage of developing complex technical systems are setting, the total number of individual and complex reliability indicators set in accordance with regulatory documents is within 5-7 units. This is done provided that they are recoverable, and also for them the requirements for durability and preservation are determined. All this determines the complexity of the procedure for their verification, confirmation and evaluation. Aim: Formation of a common (integral) indicator of reliability, which can characterize the basic reliability properties multitude of traction electrical equipment, as a complex technical system, subject to the compliance of individual indicators with the requirements specified in the terms of reference. Methods: It is proposed to use of T. Saati's hierarchy analysis method, which is widely used in solving various multicriteria problems. Conclusion: Using an integral indicator to determine the level of reliability allows getting a formalized result, expressed through the vectors of global priorities corresponding value, which makes it possible to get a quantitative assessment of the superiority for one of alternative traction electrical equipment.

Improving Reliability Estimation for Individual Numeric Predictions: A Machine Learning Approach

Numerical predictive modeling is widely used in different application domains. Although many modeling techniques have been proposed, and a number of different aggregate accuracy metrics exist for evaluating the overall performance of predictive models, other important aspects, such as the reliability (or confidence and uncertainty) of individual predictions, have been underexplored. We propose to use estimated absolute prediction error as the indicator of individual prediction reliability, which has the benefits of being intuitive and providing highly interpretable information to decision makers, as well as allowing for more precise evaluation of reliability estimation quality. As importantly, the proposed reliability indicator allows the reframing of reliability estimation itself as a canonical numeric prediction problem, which makes the proposed approach general-purpose (i.e., it can work in conjunction with any outcome prediction model), alleviates the need for distributional assumptions, and enables the use of advanced, state-of-the-art machine learning techniques to learn individual prediction reliability patterns directly from data. Extensive experimental results on multiple real-world data sets show that the proposed machine learning-based approach can significantly improve individual prediction reliability estimation as compared with a number of baselines from prior work, especially in more complex predictive scenarios.

Quantification of Water Sustainability in Upper Indus River Basin Through the Concept of Resilience, Reliability and Vulnerability (RRV)

<p>The sustainability index identifies a strategy that defend or improve the desired water management features of the basin in the future. The Upper Indus river basin is a high mountain region and consider third freshwater tower. The flow of the river consists of melting glaciers, snow, rainfall. Beyond the polar regions, the Upper Indus Basin has the largest area of glaciers in the world (22,000 km<sup>2</sup>).  About 220 million people depend on Indus Basin water for agriculture and drinking purpose. Under the changing climate, sustainability is becoming a challenge for the freshwater resources. The integration of climate variables with RRV indicators is a new approach to meet this challenge. In this study the sustainability of the upper Indus is quantified. The probabilistic concept of resilience, reliability and vulnerability is applied to rainfall variability and drought patterns. The monthly Standardized Precipitation-Evapotranspiration Index (SPEI) grided data (0.5<sup>o</sup> 0.5<sup>o</sup>) generated by climate research unit (CRU)version 4 has been used for study during the period 1901–2018. Based on the SPEI pattern, the SPEI of -0.5 was selected as the threshold (demand) to evaluate the sustainability. The results indicate the frequency of drought events in the western part of the basin is much higher than the eastern part. However, the frequency of drought events in the basin is high but the capability of the basin to resilient the droughts varies from 0.57 to 0.83. The value of reliability indicator varies from 0.8 to 0.86 and vulnerability of drought in the basin is in the range of 0.2 to 0.45. The average water sustainability index of the basin is 0.4 which lies in the category of a satisfactory<strong> </strong>state.The results of the conceptual framework of RRV can provide a more comprehensive basis for designing watershed health variables and drought management plans.</p><p> </p><p><strong>Keywords: Upper Indus Basin, Water sustainability, RRV concept, SPEI, Drought.</strong></p>

Development of the combined method for evaluating and controlling the reliability indicator «probability of failure-free switching» of a radio technical complex

The operation of a radio-technical complex based on a technical condition is represented by cycles. Each cycle implies control over a limiting state in order to make timely and informed decisions on managing the operation of a radio-technical complex. That should resolve the task of assessing and monitoring the indicators of fault-free operation with the required accuracy and reliability based on operational observations and, if necessary, special tests that could minimize the cost of special tests. Given the introduction for a radio-technical complex of the repeated application of a new indicator of fault-free operation «the probability of trouble-free switching», a combined method of its evaluation and control has been developed. This method is a set of known and developed criteria, models, methods, and schemes that determines the sequence of their application for joint evaluation and control of this indicator. The criteria for verifying the uniformity of data on the operational observations and special tests for the fault-free operation of a radio-technical complex have been defined, as well as the corresponding models for assessing the one-sided lower confidence boundaries of the indicator under consideration, and the methods to control it. The devised method makes it possible to derive estimates of the probability of trouble-free switching, as well as the magnitudes of the observed risks of decisions being made with acceptable accuracy and reliability. The results of modeling the devised combined method helped obtain the accuracy and reliability of its estimates and the observed risks of controls carried out. Recommendations have been compiled for applying the method to address the challenges of joint assessment and control of the probability of trouble-free switching of the considered complexes

An Empirical Assessment and Validation of Redundancy Metrics Using Defect Density as Reliability Indicator

Software metrics which are language-dependent are proposed as quantitative measures to assess internal quality factors for both method and class levels like cohesion and complexity. The external quality factors like reliability and maintainability are in general predicted using different metrics of internal attributes. Literature review shows a lack of software metrics which are proposed for reliability measurement and prediction. In this context, a suite of four semantic language-independent metrics was proposed by Mili et al. (2014) to assess program redundancy using Shannon entropy measure. The main objective of these metrics is to monitor program reliability. Despite their important purpose, they are manually computed and only theoretically validated. Therefore, this paper aims to assess the redundancy metrics and empirically validate them as significant reliability indicators. As software reliability is an external attribute that cannot be directly evaluated, we employ other measurable quality factors that represent direct reflections of this attribute. Among these factors, defect density is widely used to measure and predict software reliability based on software metrics. Therefore, a linear regression technique is used to show the usefulness of these metrics as significant indicators of software defect density. A quantitative model is then proposed to predict software defect density based on redundancy metrics in order to monitor software reliability.

Visualization and diagnostics of reliability of the object with changing the functioning conditions

The object of the scientific research is buildings (structures), which requiring the determination of a reliability indicator for their further operation in new operating conditions, the determination of additional loads in the form of (explosions, fires, vibration processes). The solution to such problems is relevant for buildings (structures), which are acquired (leased) by the owner, for their further operation in the new conditions of the technological process associated with the handling, storage, processing and production of fire and explosion hazardous substances (materials). It is important to determine the readiness of buildings (structures) for operation in the new conditions of functioning of the technological process of production, it is proposed to use deterministic, statistical and probabilistic approaches. It is proposed to use a simplified assessment of the safety margin of a building (structure) by yield strengths (for steel elements) and strength (for base materials, load-bearing walls, partitions and ceilings) corresponding to the maximum allowable values for their destruction. The innovative approach is described that allows us to solve the problems of assessing the strength reliability of structural elements of buildings (structures) to obtain guaranteed characteristics of a given margin of safety, its resistance to possible realized effects (explosions, fires, vibration processes)