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The purpose of this paper is to compare mechanical response of polypropylene in multi‐cycle tensile tests with strain‐controlled and mixed deformation programs and to develop constitutive equations that describe quantitatively the experimental data.

Multi‐cycle tensile tests are performed on isotactic polypropylene with strain‐controlled (oscillations between fixed maximum and minimum strains) and mixed (oscillations between a fixed maximum strain and the zero minimum stress) programs. A constitutive model is derived in cyclic viscoelasticity and viscoplasticity of semicrystalline polymers, and its parameters are found by fitting observations. The effect of damage accumulation of material parameters is analyzed numerically.

The model predicts accurately mechanical behavior of polypropylene in tests with numbers of cycles strongly exceeding those used to determine its parameters. In the regime of developed damage, material constants in the stress‐strain relations are independent of deformation program.

A novel constitutive model is derived in cyclic viscoelastoplasticity of semicrystalline polymers and comparison of its adjustable parameters is performed for different deformation programs.

The efficiency of fractional derivative and hereditary combined approach in modeling viscoelastic behavior of soft foams was successfully addressed in Elfarhani et al. (2016a). Since predictions obtained on flexible polyurethane foam (FPF) type A (density 28 kg m⁻³) were found very promoting, the purpose of this paper is to apply the approach basing on two other types of foams. Both soft polyurethane foams type B of density 42 kg m⁻³ and type C of density 50 kg m⁻³ were subjected to multi-cycles compressive tests.

The total foam response is assumed to be the sum of a non-linear elastic component and viscoelastic component. The elastic force is modeled by a seven-order polynomial function of displacement. The hereditary approach was applied during the loading half-cycles to simulate the short memory effects while the fractional derivative approach was applied during unloading cycles to simulate the long memory effects. An identification methodology based on the separation of the measurements of each component force was developed to avoid parameter admixture problems.

The proposed model reveals good reliability in predicting the responses of the two considered flexible foams. Predictions as measurements establish that residual responses were negligible compared to elastic and viscoelastic damping responses.

The development of a new combined model reveals good reliability in predicting the responses of the two polyurethane foams type A and B.

The purpose of this paper is to cover an experimental investigation of the impulse response of the foam-mass system (FMS) to unveil some of the foam dynamic behavior features needed to optimize the impact comfort of seat-occupant system. The equation of motion of the studied system is modeled as a sum of a linear elastic, pneumatic damping and viscoelastic residual forces. An identification methodology based on two separated calibration processes of the viscoelastic parameters was developed.

The viscoelastic damping force representing the foam short memory effects was modeled through the hereditary formulation. Its parameters were predicted from the free vibrational response of the FMS using iterative Prony method for autoregressive–moving–average model. However, the viscoelastic residual force resulting in the long memory effects of the material was modeled with fractional derivative term and its derivative order was predicted from previous cyclic compression standards.

The coefficients of the motion law were determined using closed form solution approach. The predictions obtained from the simulations of the impulse and cyclic tests are reasonably accurate. The physical interpretations as well as the mathematical correlations between the system parameters were discussed in details.

The prediction model combines hereditary and fractional derivative formulations resulting in short and long physical memory effects, respectively. Simulation of impulse and cyclic behavior yields good correlation with experimental findings.

THE QUADRICYCLE CONFIGURATION landing gear chosen by the aircraft designers consists of a single wheel steerable nose leg, a twin wheel main leg, and two fully castoring single wheel outrigger legs at the wing tips. All retract aft into very confined spaces. Two standards of gear, normal and high speed, were designed and developed to meet the initial and final maximum landing speed requirements.

The aim of this study is twofold. First, the research aims to identify Integrated Thinking (IT) stages of development. Second, the research aims to investigate how IT has reacted to the COVID-19 pandemic by accelerating integrated corporate social responsibility (CSR) practises.

The study employs a case study on an Italian multi-utility company, Iren Group. The research method uses triangulated data collected from semi-structured interviews and archival materials and it analyses data with a top-down and bottom-up coding procedure. This allows us to inductively develop a model of IT stages of development and CSR strategic postures as response patterns to the COVID-19 pandemic.

The research identifies the developmental paths of IT initiation, IT reactiveness and IT implementation responding to changes and challenges in times of crisis. Furthermore, the research provides stimuli for recovery to overcome periods of crisis through three main CSR strategic postures: stakeholder engagement, flexible proactiveness and democratic durability.

The research suggests that managers can adopt stakeholder engagement, flexible proactiveness and democratic durability as CSR strategic postures in order to integrate CSR practises into the company's DNA and overcome periods of crisis.

This is among the first studies that analyses how IT acts during a crisis in the multi-utility sector. There are three main stages of development, i.e. IT initiation, IT reactiveness and IT implementation, which are characterised by stakeholder engagement, flexible proactiveness and democratic durability.

Multi-cycle Learning Study and multi-cycle Lesson Study are the main collaborative action research approaches for teacher professional development in Hong Kong. The sustaining of these Lesson Study innovations may be inhibited by many challenges. The purpose of this paper is to identify the strategies school leaders utilized to overcome challenges and sustain Lesson Study innovations successfully in a Hong Kong primary school.

In-depth case study was adopted as the methodological approach to explore how Lesson Study was implemented to improve teaching and learning in the school and what leadership practices were enacted to sustain Lesson Study in the case school.

It was found that the leadership team under study had adopted positive peer leadership to successfully implement Lesson Study activities. The strategies of positive peer leadership will be discussed in detail.

The paper concludes with implications for sustaining school development and professional development with Lesson Study and a checklist of positive peer leadership practices for school leaders, teacher leaders and teacher trainers.

This paper will enrich the understanding of successful leadership practices for sustaining Lesson Study innovations in schools, on which few empirical studies have been conducted.

In this study, the authors consider the key decisions in the design of the green closed-loop supply chain (CSLC) network. These decisions include considering the optimal location of suppliers, production facilities, distribution, customers, recycling centers and disposal of non-recyclable goods. In the proposed model, the level of technology used in recycling and production centers is taken into account. Moreover, in this paper is the environmental impacts of production and distribution of products based on the eco-indicator 99 are considered.

In this study, the author consider the key decisions in the design of the green CLSC network. These decisions include considering the optimal location of suppliers, production facilities, distribution, customers, recycling centers and disposal of non-recyclable goods. In the proposed model, the level of technology used in recycling and production centers is taken into account. Moreover, the environmental impacts of production and distribution of products based on the eco-indicator 99 are considered.

The results indicate that the results obtained from the colonial competition algorithm have higher quality than the genetic algorithm. This quality of results includes relative percentage deviation and computational time of the algorithm and it is shown that the computational time of the colonial competition algorithm is significantly lower than the computational time of the genetic algorithm. Furthermore, the limit test and sensitivity analysis results show that the proposed model has sufficient accuracy.

Solid modeling of the green supply chain of the closed loop using the solid optimized method by Bertsimas and Sim. Development of models that considered environmental impacts to the closed loop supply chain. Considering the impact of the technology type in the manufacture of products and the recycling of waste that will reduce emissions of environmental pollutants. Another innovation of the model is the multi-cycle modeling of the closed loop of supply chain by considering the uncertainty and the fixed and variable cost of transport.

This paper aims to research the tribological features of AISI 1035 steel, boronized at various parameters.

The samples were boronized via box boronizing method. By using Ekabor 2 powders, boronizing was conducted at 840, 880, 920, 960 and 1,000°C for two, four and six hours. Wear resistance of boronized samples at determined parameters were analysed. Wear experiments were conducted under 40 N constant load at pin‐on‐disk experiment setup. Also, microstructures and microhardness values of boronized samples were analysed to determine the most suitable boronizing parameters against wearing.

As a result of this study, the following findings are reported: it was determined as the temperature increased, the thicker the boride layer obtained during the boronizing. In the case of longer boronizing time, the distinct columnar structure was clearer. Whenever applying higher temperature and longer boronizing time, wear decreased and hardness values increased. It was also determined that when boronizing was conducted at 900 and 1,000°C for at least four to six hours, better results were obtained. Furthermore, the increment in the boronizing temperature and longer duration caused an increase in hardness from the surface to inwards and thus a decrease in wear ratio.

In the present study, only 40 N is used for a wear load and that is the limitation of the research.

Boronizing of the parts using 900 and 1,000°C temperature and four to six hours time, the better results can be obtained. Wear resistance can be improved in the determined temperature interval for boronizing process. Therefore, the industrial firms can be gained huge economical profits.

The outcome of the study will be beneficial for the academicians and industrial firms working on wear process. The service life of the steel parts can be extended via boronizing of steels working on quarries.

The key purpose of conducting this review is to identify the issues that affect the structural integrity of pipeline structures. Heat affected zone (HAZ) has been identified as the weak zone in pipeline welds which is prone to have immature failures

In the present work, literature review is conducted on key issues related to the structural integrity of pipeline steel welds. Mechanical and microstructural transformations that take place during welding have been systematically reviewed in the present review paper.

Key findings of the present review underline the role of brittle microstructure phases, and hard secondary particles present in the matrix are responsible for intergranular and intragranular cracks.

The research limitations of the present review are new material characterization techniques that are not available in developing countries.

The practical limitations are new test methodologies and associated cost.

The fracture of pipelines significantly affects the surrounding ecology. The continuous spillage of oil pollutes the land and water of the surroundings.

The present review contains recent and past studies conducted on welded pipeline steel structures. The systematic analysis of studies conducted so far highlights various bottlenecks of the welding methods.

This study aims to introduce a novel technique which helped in quantifying the wear performance of a roller chain which was lubricated by using the palm oil-based hexagonal boron nitride (hBN) nanoparticles (nano-biolubricant).

The efficiency of the nano-biolubricant was evaluated by using a custom-made roller chain tribometer, at different resistance torque values at a constant speed and running time. Prior to the test, 2 different lubrication conditions were applied. The mass loss and elongation behaviour of a roller chain was selected as a degradation metric for monitoring the amount of the chain wear. The predominant wear mechanism of a roller chain was identified by surface morphological analysis.

Regardless of the lubrication conditions, the wear performance of the roller chain was significantly increased, at increasing resistance torque values. Higher wear was noted when the roller chain was lubricated using a nano-biolubricant, however, the wear curve showed a promising high chain life. The predominant wear mechanism involved is abrasive wear.

Although an increase in the elongation during running is based on the wear between the pins and roller, none of the earlier studies quantified the wear performance of a roller chain under differing lubrication conditions. Hence, for bridging the gap, this study described a new method for measuring the wear performance of the roller chain which was lubricated using the palm oil-based hBN nanoparticles or a nano-biolubricant.

The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-02-2020-0061/