Some Issues on Crystal Plasticity Models Formulation: Motion Decomposition and Constitutive Law Variants

In this paper, kinematic relations and constitutive laws in crystal plasticity are analyzed in the context of geometric nonlinearity description and fulfillment of thermodynamic requirements in the case of elastic deformation. We consider the most popular relations: in finite form, written in terms of the unloaded configuration, and in rate form, written in terms of the current configuration. The presence of a corotational derivative in the relations formulated in terms of the current configuration testifies to the fact that the model is based on the decomposition of motion into the deformation motion and the rigid motion of a moving coordinate system, and precisely the stress rate with respect to this coordinate system is associated with the strain rate. We also examine the relations of the mesolevel model with an explicit separation of a moving coordinate system and the elastic distortion of crystallites relative to it in the deformation gradient. These relations are compared with the above formulations, which makes it possible to determine how close they are. The results of the performed analytical calculations show the equivalence or similarity (in the sense of the response determined under the same influences) of the formulation and are supported by the results of numerical calculation. It is shown that the formulation based on the decomposition of motion with an explicit separation of the moving coordinate system motion provides a theoretical framework for the transition to a similar formulation in rate form written in terms of the current configuration. The formulation of this kind is preferable for the numerical solution of boundary value problems (in a case when the current configuration and, consequently, contact boundaries, are not known a priori) used to model the technological treatment processes.

A simple yet consistent constitutive law and mortar-based layer coupling schemes for thermomechanical macroscale simulations of metal additive manufacturing processes

This article proposes a coupled thermomechanical finite element model tailored to the macroscale simulation of metal additive manufacturing processes such as selective laser melting. A first focus lies on the derivation of a consistent constitutive law on basis of a Voigt-type spatial homogenization procedure across the relevant phases, powder, melt and solid. The proposed constitutive law accounts for the irreversibility of phase change and consistently represents thermally induced residual stresses. In particular, the incorporation of a reference strain term, formulated in rate form, allows to consistently enforce a stress-free configuration for newly solidifying material at melt temperature. Application to elementary test cases demonstrates the validity of the proposed constitutive law and allows for a comparison with analytical and reference solutions. Moreover, these elementary solidification scenarios give detailed insights and foster understanding of basic mechanisms of residual stress generation in melting and solidification problems with localized, moving heat sources. As a second methodological aspect, dual mortar mesh tying strategies are proposed for the coupling of successively applied powder layers. This approach allows for very flexible mesh generation for complex geometries. As compared to collocation-type coupling schemes, e.g., based on hanging nodes, these mortar methods enforce the coupling conditions between non-matching meshes in an $$L^2$$ L 2 -optimal manner. The combination of the proposed constitutive law and mortar mesh tying approach is validated on realistic three-dimensional examples, representing a first step towards part-scale predictions.

ADVANTAGES, DISADVANTAGES AND PROSPECTS OF IMPLEMENTING A PIECE-RATE FORM OF PAY AT THE INDUSTRIAL ENTERPRISE ENVIRONMENT

The paper considers the conditions of expediency of using the piece-rate form of pay in the modern industrial environment. The necessity to ensure implementation of the motivational and stimulating role of the pay system is noted, as both business efficiency and employee motivation depend on this choice. The extensive use of piece-rate form of pay at industrial enterprises is related to its proven advantages, the main of which is the obvious relationship between production output and wages. This stimulates to increase individual employee productivity rate and efficiency the production system as a whole. The reason for the piece-rate form of pay to be promising to consist in its flexibility and ability to transform depending on the specifics of production environment and conditions of labour organization. Emphasized that despite mentioned advantages, implementation of piece-rate form of pay has its own certain limitations and risks. Specifically, it does not natively support accounting for a quality parameters of production, may lead to violation of production process synchronicity requirement and omit compliance to the norms of material consumption. Is determined that while choosing forms and systems of pay, it should be clearly understood that the development of an effective such system for successful monetary motivation of employees at the enterprise environment is an extremely complex task and depends on multiple factors, even if we take into consideration industrial enterprises only.

Mitigation of Climate Change by Nitrogen Managements in Agriculture

Soil is one of the important sources of nitrous oxide (N2O), which is generally producing through soil microbial processes, such as nitrification and denitrification. Agricultural soils receive chemical and organic fertilizers to maintain or increase crop yield and soil fertility, but several factors are influencing N2O emissions, such as types and conditions of soil and fertilizer, and rate, form, and timing of application. Mitigation of N2O is a challenging topic for future earth by using inhibitors, controlled-release fertilizers, and other amendments, but the cost and side effects should be considered for feasibility.

Ignition Delay Time Correlation of C1 - C5 Natural Gas Blends for Intermediate and High Temperature Regime

New ignition delay time (IDT) data for stoichiometric natural gas (NG) blends composed of C1 – C5 n-alkanes with methane as the major component were recorded using a high pressure shock tube (ST) at reflected shock pressures (p5) and temperatures (T5) in the range 20 – 30 bar and 1000 – 1500 K, respectively. The good agreement of the new IDT experimental data with literature data shows the reliability of the new data at the conditions investigated. Comparisons of simulations using the NUI Galway mechanism (NUIGMech1.0) show very good agreement with the new experimental results and with the existing data available in the literature. Empirical IDT correlation equations have been developed through multiple linear regression analyses for these C1 – C5 n-alkane/air mixtures using constant volume IDT simulations in the pressure range pC = 10 – 50 bar, at temperatures TC = 950 – 2000 K and in the equivalence ratio (f) range 0.3 – 3.0. Moreover, a global correlation equation is developed using NUIGMech1.0, to predict the IDTs for these NG mixtures and other relevant data available in the literature. The correlation expression utilized in this study employs a traditional Arrhenius rate form including dependencies on the individual fuel fraction, TC, f and pc.

Ignition Delay Time Correlation of C1 – C5 Natural Gas Blends for Intermediate and High Temperature Regime

New ignition delay time (IDT) data for stoichiometric natural gas (NG) blends composed of C1 – C5 n-alkanes with methane as the major component were recorded using a high pressure shock tube (ST) at reflected shock pressures (p5) and temperatures (T5) in the range 20–30 bar and 1000–1500 K, respectively. The good agreement of the new IDT experimental data with literature data shows the reliability of the new data at the conditions investigated. Comparisons of simulations using the NUI Galway mechanism (NUIGMech1.0) show very good agreement with the new experimental results and with the existing data available in the literature. Empirical IDT correlation equations have been developed through multiple linear regression analyses for these C1 – C5 n-alkane/air mixtures using constant volume IDT simulations in the pressure range pC = 10–50 bar, at temperatures TC = 950–2000 K and in the equivalence ratio (φ) range 0.3–3.0. Moreover, a global correlation equation is developed using NUIGMech1.0, to predict the IDTs for these NG mixtures and other relevant data available in the literature. The correlation expression utilized in this study employs a traditional Arrhenius rate form including dependencies on the individual fuel fraction, TC, φ and pC.

Non-Rigid Rotating Motion Effect on Creep Behavior for Infinite Cylinders under Thermomechanical Loading

The effect of non-rigid motion on creep analysis for cylinders have been investigated. inner surface of the cylinder is exposed to a uniform heat flux and for cooling the outer surface of the cylinder an air steam is applied to it. The cylinder is subjected to a body force. That produced by rotating cylinder about its own axis. It is assumed the cylinder is not rigid. Therefore, using equations of equilibrium, stress–strain and kinematic equation, governed equation which includes redial displacement and creep strains, is obtained. The material creep constitutive model is defined by the Bailey-Norton time-dependent creep law. From a solution consisting of analytical solution and iteration method has been used to obtain history of stresses and deformations during creep evolution of rotating cylinders. Therefore, Prandtle-Ruess equation substituted in equilibrium equation in the rate form, the radial displacement rate is obtained for plane strain condition. To investigate the effect of non-rigidity, the non-rigidity parameter (ζ) is defined and its effect on the creep behavior of the structure is investigated. It was revealed that Considering the structure as rigid does neglect the amount of stresses and radial displacement. History of stresses and displacement during 20 years are studied and it is observed that the changes have not accrued in recent years. The effect of velocity is another parameter that is investigated its effect on structural behavior during the time. it was revealed that, velocity has significant effect on structural behavior which cause trend of variation behavior change from linear to polynomial curve.

How Reliably Can Examiners Make Form Quality (FQ) Judgments in the Absence of the Form Quality (FQ) Tables?

Form Quality (FQ) scores are well-validated measures of the accuracy of perceptive processes, of reality testing, and of the severity of psychological disturbance. Research studies reveal that inter-rater reliability of FQ scoring is good when visualized objects are available in the FQ tables. However, many visualized objects are not found in the FQ tables so that scoring must rely on one’s individual judgment. Thus, a major question remains unsolved: How reliably can examiners make FQ judgments in the absence of the FQ tables? To address this question, we used the Rorschach Performance Assessment System (R-PAS) method. We asked 21 graduate students from our research labs to rate Form Accuracy (FA) and FQ for 86 objects from a subset of four Rorschach card (I, III, VI, and VIII). The results clearly reveal that FQ judgments made by individual examiners without using the FQ tables are not reliable. When scoring FQ, one should carefully scrutinize the empirically supported FQ tables and base the FQ score on these rather than personal judgments.

Kinetics and Thermodynamics of Thermal Degradation of Different Starches and Estimation the OH Group and H2O Content on the Surface by TG/DTG-DTA

The main aim of this study is to estimate the kinetic and thermodynamic parameters of thermal decomposition of starches by the Coats–Redfern method. This procedure is a commonly used thermogravimetric analysis/difference thermal gravimetry/differental thermal analysis (TG/DTG-DTA) kinetic method for single rate form. The study also shows a proposed method for reactive hydroxyl groups content on the starch surface determination, and values were in range of 960.21–1078.76 mg OH per 1 g of starch. Thermal processing revealed the thermophysical properties of biomass for the kinetics of decomposition estimation. Activation energies reached the values in range of approximately 66.5–167 kJ·mol−1. This research also enables the determination of the temperature conditions required for becoming the desired form of material. Therefore, it is necessary to achieve the requested compact porous structure in an activation process, because in the native state, the polymer exhibits limited applications as a result of thermal decomposition, low shear stress, retrogradation, and syneresis, hence the low solubility in organic solvents. Thermodynamic parameters and reactive hydroxyl groups in this article review are innovative and have not yet been found in the literature.

Estimation of 13-valent Pneumococcal Conjugate Vaccine Efficiency in Infants within National Immunization Schedule

Background. Vaccination of infants with 13-valent pneumococcal conjugate vaccine (PCV) was implemented in national immunization schedule in 2014. In this regard epidemiological monitoring of routine immunization results with vaccination coverage and efficiency control is required. Objective. Our aim was to study correlation between pneumococcal disease routine immunization in infants and morbidity and mortality rates due to community-acquired pneumonia in children under 18 years of age and morbidity rate due to acute otitis media in children under 14 years of age. Methods. Morbidity (Form № 2, 2011–2017 yrs) and mortality (Form № 51S, 2009–2017 yrs) rates due to community-acquired pneumonia, morbidity rate (Form № 12, 2009–2017 yrs) due to acute otitis media, vaccination coverage rate (Form № 5, 2014–2017 yrs, and Form № 6, 2016–2017 yrs) were analysed according to the data of Forms of Federal Statistical Monitoring. Medical exemptions and refusals to vaccinate rates were estimated according to the data from doctors who was performing infants vaccination. Results. During PCV routine vaccination within national immunization schedule in Russian Federation the 35% reduction of mortality due to community-acquired pneumonia in children under 1 year of age as well as reduction of morbidity with acute otitis media have been established. Moreover, low percentage of etiology clear community-acquired pneumonias (29%) complicates the estimation of vaccination efficiency. It has been revealed that despite the high pneumococcal disease vaccination coverage rate of infants under 2 years of age (87%), considerable part of children (73%) are vaccinated untimely in most Russian Federation regions. 9.3% (3.4% due to medical exemptions) of children (among 1st year infants) remained unvaccinated due to medical exemptions and refusals to vaccinate in 2016, and 8% (3.4%) in 2017 respectively. Conclusion. Implementation of PCV routine immunisation for three years in a row leads to reduction of morbidity rate due to acute otitis media among children under 14 years of age and infant mortality rate due to community-acquired pneumonias. Though, the estimation of routine immunisation efficiency can be difficult due to such factors as untimely start of vaccination, medical exemptions and refusals to vaccinate and limited laboratory diagnostics of community-acquired pneumonias etiology.