Search results

This study aims to focus on numerical simulation investigations of phase transformation during cooling of 55SiMnMo steel, which is commonly applied to improve mechanical properties.

A mathematical model based on the finite element method (FEM) and the phase transformation kinetics model has been proposed to predict microstructure changes during continuous cooling of 55SiMnMo steel. This model can be employed to analyze the variation of austenite, special upper bainite and lump-like composite structure with cooling time at different cooling rates.

According to the continuous cooling experiments, when the cooling rate is lower than 0.1°C/s, the special upper bainite is the only transformation product which decreases with increasing cooling rate; when the cooling rate is above 0.5°C/s, the transformation products include special upper bainite and lump-like composite structure. Meanwhile, the results of continuous cooling experiment verified the correctness of this finite element model.

This model has a great value for proper controlling of the cooling process which can improve the quality of hollow drill steel and increase the service life of the final product.

A fundamental principle of materials engineering is that the microstructure of a material controls the properties. The phase transformation is an important phenomenon that determines the final microstructure. Recently, many analytical and numerical methods were used for modeling of phase transformation, but some limitations can be seen in relation to the choice of the shape of growing grains, introduction of varying grain growth rate and modeling of diffusion phenomena. There are also only few comprehensive studies that combine the final microstructure with the actual conditions of its formation. Therefore, the objective of the work is a development of a new hybrid model based on lattice Boltzmann method (LBM) and cellular automata (CA) for modeling of the diffusional phase transformations. The model has a modular structure and simulates three basic phenomena: carbon diffusion, heat flow and phase transformation. The purpose of this study is to develop a model of heat flow with consideration of enthalpy of transformation as one of the most important parts of the proposed new hybrid model. This is one of the stages in the development of the complex model, and the obtained results will be used in a combined solution of heat flow and carbon diffusion during the modeling of diffusion phase transformations.

Different values of overheating/overcooling affect different values in the enthalpy of transformation and thus the rate of transformation. CA and LBM are used in the hybrid model in part related to heat flow. LBM is used for modeling of heat flow, while CA is used for modeling of the microstructure evolution during the phase transformation.

The use of LBM and CA in one numerical solution creates completely new possibilities for modeling of phase transformations. CA and LBM in comparison with commonly used approaches significantly simplify interface and interaction between different parts of the model, which operates in a common domain. The CA can be used practically for all possible processes that consist of nucleation and grains growth. The advantages of the LBM method can be well used for the simulation of heat flow during the transformation, which is confirmed by numerical results.

The developed heat flow model will be combined with the carbon diffusion model at the next stage of work, and the new complex hybrid model at the final stage will provide new solutions in numerical simulation of phase transformations and will allow comprehensive modeling of the diffusional phase transformations in many processes. Heating, annealing and cooling can be considered.

The paper presents the developed model of heat flow (temperature module), which is one of the main parts of the new hybrid model devoted to modeling of phase transformation. The model takes into account the enthalpy of transformation, and the connection with the model of microstructure evolution was obtained.

Some functional properties of engineering materials, i.e. physical, mechanical and thermal ones, depend directly on the microstructure, which is a result of processes occurring in the material during the forming and thermomechanical processing. The proper microstructure can be obtained in many cases by the phase transformation. This phenomenon is one of the most important processes during hot forming and heat treatment. The purpose of this paper is to develop a new comprehensive hybrid model for modeling diffusion phase transformations. A problem has been divided into several tasks and is carried out on several stages. The purpose of this stage is a development of the structure of a hybrid model, development of an algorithm used in the diffusion module and one-dimensional heat flow and diffusion modeling. Generally, the processes of phase transformations are studied well enough but there are not many tools for their complex simulations. The problems of phase transformation simulation are related to the proper consideration of diffusion, movement of phase boundaries and kinetics of transformation. The proposed new model at the final stage of development will take into account the varying grain growth rate, different shape of growing grains and will allow for proper modeling of heat flow and carbon diffusion during the transformation in many processes, where heating, annealing and cooling can be considered (e.g. homogenizing and normalizing).

One of the most suitable methods for modeling of microstructure evolution during the phase transformation is cellular automata (CA), while lattice Boltzmann method (LBM) suits for modeling of diffusion and heat flow. Then, the proposed new hybrid model is based on CA and LBM methods and uses high performing parallel computations.

The first simulation results obtained for one-dimensional modeling confirm the correctness of interaction between LBM and CA in common numerical solution and the possibility of using these methods for modeling of phase transformations. The advantages of the LBM method can be used for the simulation of heat flow and diffusion during the transformation taking into account the results obtained from the simulations. LBM creates completely new possibilities for modeling of phase transformations in combination with CA.

The studies are focused on diffusion phase transformations in solid state in condition of low cooling rate (e.g. transformation of austenite into ferrite and pearlite) and during the heating and annealing (e.g. transformation of the ferrite-pearlite structure into austenite, the alignment of carbon concentration in austenite and growth of austenite grains) in carbon steels within a wide range of carbon content. The paper presents the comprehensive modeling system, which can operate with the technological processes with phase transformation during heating, annealing or cooling.

A brief review of the modeling of phase transformations and a description of the structure of a new CA and LBM hybrid model and its modules are presented in the paper. In the first stage of model implementation, the one-dimensional LBM model of diffusion and heat flow was developed. The examples of simulation results for several variants of modeling with different boundary conditions are shown.

Most successful companies have adopted some type of improvement methodology to achieve optimum performance, high quality, lower costs and productivity. Some of the structured methodologies employed indiscriminately are total quality management, quality control, agile, lean and Six Sigma which yield varied results. The purpose of this paper is to explore how to harness the power of an integrated system of quality tools and techniques to create operational excellence. An integrated framework involves matching quality tools and techniques to the multi-phases (input, transformation and output) of lean manufacturing or service ecosystem.

Current research of lean quality systems provides a conceptual understanding of core tools employed by manufacturing and service organizations. Interviewing domain experts from a series of manufacturing and service organizations highlighted a common challenge. The challenge was lean tools and methodologies were selected and employed arbitrarily for the different operational phases, which resulted in selective synergies of tools between operational phases. This limitation resulted in rework and duplication of quality efforts through the diverse phases of the transformation system. This study is based on the hypothesis that all phases of an operational system must be linked by common tools and methodologies which enables harnessing quality benefits and synergies throughout the entire operational system. The study methodology trailed through cooperative inquiry using a case study approach to design an integrated framework of tools that facilitates a common platform for manufacturing or service ecosystems.

This study suggests that quality systems in a complex competitive environment must consider an integrated iterative approach. An iterative development of lean quality tools for multiple phases produces an integrated quality system. Such systems employ blending and extending of lean quality tools to multiple phases of the transformation system to synthesize agile and versatile quality system.

A limitation of this study is that the research of integrated framework is based on repertory grid technique only; it should be supplemented by other methods. Second, the proposed framework does not consider the complexity added by the internal and external stakeholders as they interface with the integrated system at different points with reference to phases of the system.

One of the advantages of this method is its generality, instead of delivering a monolithic system at the culmination of long transformation process we rely on smaller quality sprints which are implemented sequentially at each stage or phase of the transformation system. The phenomena of incremental clustering of time-series of quality sprints for different phases results in true integration from end to end for a transformation system.

This study helps investigate the personal constructs that users and managers employ to interpret and select quality tools or methodologies for the different phases of lean transformational system.

This study aims to understand the impact of blending quality and business process improvement tools and methodologies to enhance outcomes. The basis of this study is “the power of multiplicity” through which a diverse collection of improvement paths is pooled into an integrated framework of quality tools for lean and efficient operations.

The purpose of this study is to assess the influence of Al and Ag addition on thermal, mechanical and shape memory properties of Cu-Al-Ag alloy.

The material is synthesized in a controlled atmosphere to minimize the reaction of alloying elements with the atmosphere. Cast samples were homogenized, then subjected to hot rolling and further betatized, followed by step quenching. Eight samples were chosen for study among which first four samples varied in Al content, and the next set of four samples varied in Ag composition.

The testing yielded a result that the increase in binary alloying element decreased transformation temperature range but increased entropy and elastic energy values. It also improved the shape memory effect and mechanical properties (UTS and hardness). An increase in ternary alloying element increased transformation temperature range, entropy and elastic energy values. The shape memory effect and mechanical properties are enhanced by the increase in ternary alloying element. The study revealed that compositional variation of Al should be limited to a range of 8 to 14 Wt.% and Ag from 2 to 8 Wt.%. Microstructural and diffraction studies identified the ß’1 martensite as a desirable phase for enhancing shape memory properties.

Numerous studies have been made in exploring the transformation temperature and phase formation for similar Cu-Al-Ag shape memory alloys, but their influence on shape memory effect was not extensively studied. In the present work, the influence of Al and Ag content on shape memory characteristics is carried out to increase the design choice for engineering applications of shape memory alloy. These materials exhibit mechanical and shape memory properties within operating ranges similar to other copper-based shape memory alloys.

The purpose of this study is to quantify the impact of the variation of microstructural features on macroscopic and microscopic fields. The application of multi-scale methods in the context of constitutive modeling of microheterogeneous materials requires the choice of a representative volume element (RVE) of the considered microstructure, which may be based on some idealized assumptions and/or on experimental observations. In any case, a realistic microstructure within the RVE is either computationally too expensive or not fully accessible by experimental measurement techniques, which introduces some uncertainty regarding the microstructural features.

In this paper, a systematical variation of microstructural parameters controlling the morphology of an RVE with an idealized microstructure is conducted and the impact on macroscopic quantities of interest as well as microstructural fields and their statistics is investigated. The study is carried out under macroscopically homogeneous deformation states using the direct micro-macro scale transition approach.

The variation of microstructural parameters, such as inclusion volume fraction, aspect ratio and orientation of the inclusion with respect to the overall loading, influences the macroscopic behavior, especially the micromechanical fields significantly.

The systematic assessment of the impact of microstructural parameters on both macroscopic quantities and statistics of the micromechanical fields allows for a quantitative comparison of different microstructure morphologies and a reliable identification of microstructural parameters that promote failure initialization in microheterogeneous materials.

Technology has disrupted many industries from the start of Industrialization era to the Industry 4.0 era. There has been an exponential growth in the technological front and people are talking about Industry 5.0. Digital transformation is a critical direction in which organizations will have to move toward in order to succeed in this competitive world. To make a smooth transition, firms must understand the basic building blocks of the digital transformation process and the key areas it touches upon namely customer experience, operational process and dynamic business models. Organizations will also have to identify the enablers of digital transformation which they can work on to smoothen the transformative process. Firms will also need the framework of digital transformation spelling out the roadmap for effective digital transformation. Firms on the urge to go for digital transformation will face numerous challenges in all the stages of implementation namely the initiation phase, the execution phase and the governance phase. A clear understanding of these challenges will help the firms to overcome or mitigate these challenges and be successful in their digital transformation process.

This paper aims to better control the mechanical properties and functional properties of NiTi alloy.

NiTi alloy samples with equal atomic ratio were formed by selective laser melting (SLM). X-ray diffraction (XRD), differential scanning calorimetry (DSC), scanning electron microscopy and tensile testing methods were used to study the effects of different laser power and scanning speed on the densification behavior, phase transformation characteristics and mechanical properties of NiTi alloy.

Compared with the laser power, the variation of the keyhole effect caused by the change of scanning speed is more intense, which has a greater effect on the densification behavior of SLM NiTi alloy. The effect of the laser power on the phase transition temperature is small. The increase of scanning speed weakens the burning degree of Ni element, so phase transition temperature decreases. The results of DSC test and tensile test show that the scanning velocity can significantly change the phase transition temperature, martensite twins reorientation and stress–strain behavior of SLM NiTi alloy.

This study provides a potential method to regulate the mechanical properties and functional properties of NiTi shape memory alloy in the future and NiTi alloys formed by SLM with good elongation were obtained because the Supercellular crystal structure formed during the nonequilibrium solidification of SLM and the superfine precipitates dispersed in the alloy prevented the dislocation formation.

Increasing global competition, free trade agreements, low cost foreign labor, and customer expectations are causing manufacturing enterprises to implement aggressive transformation plans. Should these transformations be incremental or enterprise‐wide? This paper aims to address the question by developing a Lean Enterprise Architecture (LEA) concept for an enterprise‐wide transformation.

The LEA is an architectural framework for enterprise reengineering in the design, construction, integration, and implementation of a lean enterprise using systems engineering methods. The architecture uses a multiphase approach structured on the transformation life cycle phases.

Viewing lean implementation across the entire enterprise minimizes the possibility of overlooking opportunities for further performance improvement. A silo view of lean implementation may allow gaps in performance to persist, with no one assuming responsibility for the entire enterprise. Employing the principles of the LEA will help improve enterprise‐wide quality, on‐time delivery, and customer satisfaction by eliminating waste in the entire organization and supply chain.

Applications and benefits are cited in the paper, but additional case studies are needed to benchmark the performance of the LEA against incremental lean implementations.

The LEA was created for the US military aerospace industry, but it is now being adopted in other commercial sectors for major transformation designs.

The LEA is the first known integration of lean thinking, enterprise architectures, and systems engineering principles in a design framework for the transformation of an enterprise.

Today's business environment emerges the need for organizations to continuously transform themselves, in order to maintain and reinforce their ability to compete successfully. The purpose of this paper is to present an analysis of the transformation process of supply chain in order to provide a modular structured management tool for planning, implementing and measure the effectiveness of supply chain transformation process (SCTP), in relation to overall organizational performance and business strategy.

The focal concepts upon which the overall approach is based are the strategic planning process, the human resources management techniques, the link between organizational structure and culture, the marketing integration and the importance of quality evaluation.

The success of such efforts depends on a number of correlated parameters, among which, those of top management commitment and behavioural issues of human resources are the most critical. The tool proposed in this paper for the transformation of the supply chain, provides a flexible sequence of project phases, linked together in a loop and continuously assessed against specific evaluation criteria, to assure the project quality and the continual transformation dynamics.

The pilot implementation of the tool to a big furniture organization led to the development of an integrated supply chain function, which would integrate planning, purchasing, production, warehousing distribution and transportation processes. The customer satisfaction rate had an increase of 25 percent, six months after the fulfilment of the transformation and three key suppliers reported a significant decrease of the duration of the overall purchasing process.

The paper presents a modular tool to facilitate the management of a SCTP as a project, taking under consideration the critical sensitivity factors of a transformation process.