Metallographic examination and reconstruction of the 6th century lombardic sword from Kyjov

ABSTRACT

A Lombardic cemetery dating to the late Migration Period was excavated at Kyjov (Czech Republic) in 2010, and inter alia a warrior’s grave no.881, which had never been looted, was uncovered there. The burial included a sword, which was subjected to a detailed conservation survey and then to metallographic examination. Further technological information was obtained by the production of a replica of the sword. The weapon can be characterized as a pattern-welded sword, with cutting edges and an inner core of steel. Construction and heat treatment of the sword are discussed in a broader context of 5th–7th century swords and sword-making. Experimental reconstruction of the sword shows that historical pattern-welded composites reveal a clear pattern after being exposed to controlled corrosion in vinegar vapor.     

Investigation of the relationships of process parameters,molten pool geometry and shear strength in laser transmission welding of polyethylene terephthalate and polypropylene

This study concerns the laser transmission welding (LTW) of polyethylene terephthalate (PET) and polypropylene (PP) which are widely used in the automotive, aerospace and medical industries. The relationships of process parameters, molten pool geometry (both width and depth) and shear strength (SS) in LTW process are systematically investigated through finite element method (FEM), response surface methodology (RSM) and experiments. Thereinto, the relationships between the molten pool depths to width (D/W) ratio and SS are firstly investigated. Firstly, a three-dimensional thermal model is developed to simulate the temperature field and molten pool geometry of the LTW process. The simulation results are confirmed by experiments. Then RSM is utilized to design the experiments and establish the mathematical relationships between the process parameters and molten pool geometry based on the simulation results. The interaction effects of the process parameters on the molten pool geometry are analyzed. Finally, the simulation results are further used for searching the relationships between the molten pool D/W ratio and the SS (from tensile experiments). The maximum value of the SS and the corresponding molten pool D/W ratio is found. The result reveals that the molten pool D/W ratio has a significant influence on the SS. Moreover, this finite element model can also play a commendable guiding role in the LTW experiments with acceptable accuracy.     

Influence of market orientation on performance: the moderating roles of customer participation breadth and depth in new product development

ABSTRACT

With a greater number of B2B firms integrating customers into the new product development (NPD) process, how to utilize customer involvement in NPD is an important decision because it may be a double-edged sword carrying both bright and dark sides. Utilizing a sample of 193 B2B firms across various industries, we validate previous research that suggests market orientation positively influences NPD performance and subsequently examine how this relationship may either be enhanced or diminished contingent upon how customers are utilized in the NPD process. The results show that the market orientation–NPD performance relationship is enhanced by having customers participate in a greater number of activities throughout NPD (customer participation breadth) and diminished when customers are involved at deeper levels (customer participation depth). This research suggests that the exact involvement of customers is a critical decision and has clear implications for the dialogues about customer involvement and management of customer relationships.     

线性成型装药的威力研究

论文从理论和试验两方面探讨了试验材料和手段对线性成形装药威力测试结果的影响,认为线性装药在射流形成过程中拉伸是二维的,这样射流切割刀容易断裂,威力相对减小;靶板尺寸和起爆方式都能够影响其威力测试结果.提出了在测试线性装药的威力时采用的靶板长和宽一般分别选择其装药长度和宽度的2倍左右为最佳.     

Experiment and simulation on the thermal instability of a heavily deformed Cu-Fe composite

The thermal instability of the Fe fibers in the heavily deformed Cu-12.8 wt.%Fe composites is investigated experimentally and numerically. The fiber evolution is characterized by a field emission scanning electron microscopy (FESEM). The results show that the dominant instability of the Fe fibers is the longitudinal boundary splitting which is determined by the greater cross sectional aspect ratio (width/thickness, w/t) and the larger ratio of boundary to interfacial energy (γ_B/γ_S). The longitudinal boundary splitting makes the ribbon-like Fe fibers evolve into a series of cylindrical fibers. Then the cylindrical Fe fibers undergo the instability process in terms of the breakup, growth and coarsening concurrently. The breakup times are accurately predicted by the Rayleigh perturbation model. The growth process primarily contributes to the higher increasing rate of the fiber radius during isothermal annealing at 700 °C than that calculated by the coarsening theory developed for cylindrical fibers, since the Cu-matrix of composites is highly supersaturated after casting/cold-working process.     

The RMVT- and PVD-based finite layer methods for the three-dimensional analysis of multilayered composite and FGM plates

The Reissner mixed variational theorem (RMVT)- and principle of virtual displacements (PVD)-based finite layer methods (FLMs) are developed for the three-dimensional (3D) analysis of simply-supported, multilayered composite and functionally graded material (FGM) plates subjected to mechanical loads. The material properties of the FGM layers are assumed to obey either an exponent-law exponentially varied with the thickness coordinate or the power-law distributions of the volume fractions of the constituents. In these formulations, the plate is divided into a number of finite layers, where the trigonometric functions and Lagrange polynomials are used to interpolate the in- and out-of-plane variations of the field variables of each individual layer, respectively. Because an h-refinement instead of a p-refinement process is adopted to yield the convergent solutions in this analysis, the layerwise either linear or parabolic function distribution through the thickness coordinate is assumed for the related field variables. The unified formulations of these two kinds of FLMs with freely-chosen orders for the in- and out-of-plane field variables are presented. The accuracy and convergence rate of a variety of RMVT- and PVD-based FLMs developed in this paper are assessed by comparing their solutions with the exact 3D solutions available in the literature.     

Analysis of the Current Noise Produced in Stationary Conditions in MgB2 Films at Different Stages of the Superconducting Transition

In previous papers (Mazzetti et al. in Phys. Rev. B 77:064516, 2008; Ponta et al. in Phys. Rev. B 79:134513, 2009) the mechanism of resistive transition of MgB₂ films has been investigated by the analysis of the non-stationary noise produced during the transition process. The developed model suggested that when the transition occurs very near to T _C at low bias current, a mixed state, consisting of normal and superconductive domains, takes place. A different model based on fluxoids dynamics, generated by the current and/or by an external field, is appropriate when the transition occurs at strong bias currents and temperatures much lower than T _C. The purpose of this paper is a further investigation of the transition process at low bias currents by analyzing the 1/f power spectra of the noise, taken in stationary conditions at different values of the specimen resistance. These spectra, when renormalized to represent the relative fluctuation of the specimen resistance, are practically coincident, a fact in agreement with the developed model.     

Systems engineering medicine: engineering the inflammation response to infectious and traumatic challenges

The complexity of the systemic inflammatory response and the lack of a treatment breakthrough in the treatment of pathogenic infection demand that advanced tools be brought to bear in the treatment of severe sepsis and trauma. Systems medicine, the translational science counterpart to basic science''s systems biology, is the interface at which these tools may be constructed. Rapid initial strides in improving sepsis treatment are possible through the use of phenomenological modelling and optimization tools for process understanding and device design. Higher impact, and more generalizable, treatment designs are based on mechanistic understanding developed through the use of physiologically based models, characterization of population variability, and the use of control-theoretic systems engineering concepts. In this review we introduce acute inflammation and sepsis as an example of just one area that is currently underserved by the systems medicine community, and, therefore, an area in which contributions of all types can be made.     

Systematic retrofit procedure for resource conservation network based on pinch analysis technique

Over the past two decades, various process integration tools have been developed for the synthesis of material resource conservation network (RCN), ranging from pinch analysis and mathematical programming techniques. Note, however, that most of these techniques were developed for grassroots design problems. In other words, the process plants are still at the design stage where the RCN does not exist yet. The grassroots design techniques are not directly applicable for existing process plants that are in operation. For the latter, some degrees of resource conservation may have been in place, though the RCNs of these process plants may not be designed systematically. Hence, this calls for the development of a systematic retrofit procedure in order to reduce both fresh resource and waste discharge flowrates for the process plants. In this work, a three-step procedure based on pinch analysis is proposed for the retrofit of existing RCNs, focusing on direct reuse/recycle scheme for single contaminant problems. A new analysis tool known as the load–flowrate diagram is proposed for the analysis of impurity load received by the material sinks. This tool helps to identify suitable sinks where unutilised sources may be recovered to. Besides, a revised nearest neighbour algorithm is proposed for the revamping of sink-source matches in the RCN. Several literature examples involving water and hydrogen networks are solved to elucidate the newly proposed procedure.     

High fidelity multidisciplinary design optimization of a wing using the interaction of low and high fidelity models

This paper presents an efficient metamodel building technique for solving collaborative optimization (CO) based on high fidelity models. The proposed method is based on a metamodeling concept, that is designed to simultaneously utilize computationally efficient (low fidelity) and expensive (high fidelity) models in an optimization process. A distinctive feature of the method is the utilization of interaction between low and high fidelity models in the construction of high quality metamodels both at the discipline level and system level of the CO. The low fidelity model is tuned in such a way that it approaches the same level of accuracy as the high fidelity model; but at the same time remains computational inexpensive. In this process, the tuned low fidelity models are used in the discipline level optimization process. In the system level, to handle the computational cost of the equality constraints in CO, model management strategy along with metamodeling technique are used. To determine the fidelity of metamodels, the predictive estimation of model fidelity method is applied. The developed method is demonstrated on a 2D Airfoil design problem, involving tightly coupled high fidelity structural and aerodynamic models. The results obtained show that the proposed method significantly reduces computational cost, and improves the convergence rate for solving the multidisciplinary optimization problem based on high fidelity models.     

The efficiency of mechanical concrete comminution

The paper reports about the comminution of cementitious composites in a laboratory jaw breaker. Six different concrete types, two mixtures of hardened cement paste, and one mortar sample are investigated. The efficiency of the breaking process is calculated based on a non-linear fracture approach. The efficiency η is the ratio between net energy delivered by the crusher and the fracture energy dissipated in the materials during the fragmentation process. Typical efficiency values between 0.03<η<0.19 are estimated. However, efficiency increases as the fracture energy of the material increases and brittleness decreases. Jaw breakers are efficient for low-brittle materials. It is suggested to use the approach developed in the paper for estimating the efficiency of rock comminution processes.     

The modelling of the freezing process in fine-grained porous media: Application to the frost heave estimation

The solution of the moving-boundary problem, related to heat- and mass-transfer processes in freezing, fine-grained, porous media under phase-transition conditions is presented. It is assumed that a freezing zone, characterized by a wide temperature range of phase transitions, is formed. Therefore a three-zone model is developed. The preservation of the term ∂L/∂t(L is the ice content) in the system of equations has made it possible to determine the ice distribution within the frozen and the freezing zones. For loamy soils the dependence of the freezing process on the characteristic parameters, the Stefan and Lewis numbers, was analyzed. It was found that increasing the enthalpy of phase transition, i.e., decreasing the Stefan number Ste, resulted in diminution of the frozen zone but, at the same time, the ice content within this zone increased. Intensification of the migration process, i.e., increasing the Lewis number Le, also led to diminution of the frozen zone, in which the ice content and, consequently, the total moisture (including ice) were increased. For large Lewis numbers the freezing zone was observed to decrease. When the water migration process is absent (Le = 0), the calculations, which were based on the described model show that in the course of freezing the redistribution takes place only between moisture and ice contents. The total moisture remains constant and equal to the initial water content. The theoretical conceptions and results derived from the analytical solution are in agreement with experimental findings. The presented model predicts the freezing process in porous media and satisfactorily reflects observed phenomena. The utilization of the considered problem solution to the prediction of the frost heave phenomenon in soils freezing processes shown that the calculated frost heave curve matches the experimental results very closely indicating that the model can well reproduce the frost heaving process associated with the freezing. Propagation of the freezing front in the test is predicted the experimental results with reasonable accuracy.     

Research and Measures on the Security of Internet of Things

With the development of intelligent perception,recognition technology and pervasive computing,Internet of things( IoT) is widely used,the security problem is also concerned by more and more researchers. IoT is a double-edged sword. On the one hand,it has great potential in simplifying the business process and provides an effective way for the enterprise to interact with the customers. But on the other hand,it also provides convenience for cyber crimes and hackers.First of all,Three layers logic architecture of IoT is introduced,and the security problems at each level and the key points of the research are expounded,and then the security requirements are analyzed. The main causes of security problems are summarized and analyzed: physical attack and the threat of equipment and malware,file attack and hacker attack. Finally,through the application of the existing technology in IoT environment,the exploration of new technology and the security of the hardware related to IoT,the security of the software and the security team,the future research direction of the security of IoT is pointed out.     

Prediction and optimization of friction welding parameters for super duplex stainless steel (UNS S32760) joints

Friction welding finds widespread industrial use as a mass production process for joining materials. Friction welding process allows welding of several materials that are extremely difficult to fusion weld. Friction welding process parameters play a significant role in making good quality joints. To produce a good quality joint it is important to set up proper welding process parameters. This can be done by employing optimization techniques. This paper presents a multi objective optimization method for optimizing the process parameters during friction welding process. The proposed method combines the response surface methodology (RSM) with an intelligent optimization algorithm, i.e. genetic algorithm (GA). Corrosion resistance and impact strength of friction welded super duplex stainless steel (SDSS) (UNS S32760) joints were investigated considering three process parameters: friction force (F), upset force (U) and burn off length (B). Mathematical models were developed and the responses were adequately predicted. Direct and interaction effects of process parameters on responses were studied by plotting graphs. Burn off length has high significance on corrosion current followed by upset force and friction force. In the case of impact strength, friction force has high significance followed by upset force and burn off length. Multi objective optimization for maximizing the impact strength and minimizing the corrosion current (maximizing corrosion resistance) was carried out using GA with the RSM model. The optimization procedure resulted in the creation of nondominated optimal points which can aid the process operator to fix the input control variables. The selection of a point from the Pareto front will always be a trade-off between the corrosion resistance and impact strength of the weld depending on the application.     

An approach to modeling time-dependent creep and residual stress relaxation around cold worked holes in aluminium alloys at room temperature

Creep behaviour of aluminium alloys is also observed at room temperature. As a result, a relaxation occurs of deliberately introduced beneficial residual stresses around fastener holes, before the relevant structural component is subjected to exploitation. Therefore, to adequately asses the life-time of the component with cold worked holes, it is necessary to quantify this relaxation. In this paper a combined iterative approach for building a time-dependent creep constitutive model of aluminium alloys at room temperature has been developed in order to be used in finite element (FE) simulations of the cold hole working process. The approach is based on an experimental study of the change in diameters of cold worked holes through mandrel cold working method and a subsequent series of FE simulations of the cold working process and of the following creep behaviour to determine the necessary equivalent stresses in the constitutive model. The obtained creep constitutive model has been founded on the power-law model. The model parameters A, n and m have been determined on the basis of a developed by the authors algorithm. The approach has been illustrated on D16T aluminium alloy widely used in the airspace industry. The material behaviour in the plastic field has been described by the nonlinear kinematic hardening model, obtained through a uniaxial tensile test. Both constitutive models have been used in FE simulations of the cold working processes and of subsequent residual stress relaxation around the cold worked open holes due to creep at room temperature. On the base of the FE results, mathematical models describing the residual stress relaxation have been obtained. Thus, the residual stresses are adequately evaluated immediately before introducing the structural component in operation.     

Thermal contact resistance estimation: influence of the pressure contact and the coating layer during a hot forming process

The Thermal Contact Resistance R _C Estimation constitutes an encountered problem to be resolved in any forming process. To fairly simulate a part cooling during a hot stamping process, an experimental device was designed and developed by the Laboratoire de Thermocinétique de Nantes—France in collaboration with ArcelorMittal R&;D Montataire—France. The object is to estimate the thermal contact resistance at the part/tool interface during the three stage of the hot stamping process. During hot stamping phases, different contact types occur at the part/tool interface. The forming phase is characterized by a dynamic contact due to the increasing effort applied by the punch. At the contact interfaces, thermal contact resistances R _C are estimated experimentally through a non-linear 1D inverse technique founded on sequential method of Beck. Experiments were carried out on hot stamping samples made of Usibor 1500P® and 22MnB5 galvanized steel. The range of prospected stamping pressure varies from 10 to 30?MPa. The analysis of the effort curves shows the same mechanical resistance law of the part during the forming phase, whatever the consign effort settled to reach the maximum stamping pressure. The R _C value estimated for the galvanized steel is 33% lower than the one estimated for Usibor 1500P®. It is due to a higher harmonic thermal conductivity of the coated material. Results have been established as correlation of type: R _C ?=?f(P) to be used for numerical simulation.     

Synthesis and characterization of hematite pigment obtained from a steel waste industry

Pigments that meet environmental and technology requirements are the focus of the research in the ceramic sector. This study focuses on the synthesis of ceramic pigment by encapsulation of hematite in crystalline and amorphous silica matrix. Iron oxide from a metal sheet rolling process was used as chromophore. A different content of hematite and silica was homogenized by conventional and high energy milling. The powders obtained after calcinations between 1050 and 1200 °C for 2 h were characterized by X-ray diffraction and SEM analysis. The pigments were applied to ceramic enamel and porcelain body. The effect of pigment was measured by comparing L*a*b* values of the heated samples. Results showed that the color developed is influenced by variables such as oxide content employed, conditions of milling and processing temperature. The results showed that the use of pigment developed does not interfere in microstructural characteristics of pigmented material. The best hue was obtained from samples with 15 wt% of chromophore, heated at 1200 °C in amorphous silica matrix.     

Fine-grained alloys by thermomechanical processing

Grain refinement during thermomechanical processing is conventionally achieved by discontinuous recrystallization. However, techniques involving severe deformation which increase the grain boundary area and can result in a micron-scale grain size by a process of continuous recrystallization have been developed. Various methods which are based on control of the deformation conditions and cooling rate during hot rolling of steels have utilised the α–γ phase transformation to produce micron-grained ferrite. Ultra-fine-grain structures exhibit interesting mechanical properties, and in certain cases a large amount of strengthening may be achieved with little or no reduction in ductility.     

The mechanism and kinetics of formation and decomposition of magnesium hydride

The formation and decomposition of magnesium hydride was studied in the temperature range 610–630 K and at pressures from the equilibrium value to 1.6 MPa. The formation of a chemisorbed hydrogen layer on the sample surface seems to be the first important step of the hydriding process. Further hydriding is developed due to nucleation and growth rather than the coating hydride layer growing. We demonstrate that the dehydriding rate can be decreased by treating a sample at p_eq; this phenomenon proves the model proposed.     

Fuzzy decision support for tools selection in the core front end activities of new product development

The innovation process may be divided into three main parts: the front end (FE), the new product development (NPD) process, and the commercialization. Every NPD process has a FE in which products and projects are defined. However, companies tend to begin the stages of FE without a clear definition or analysis of the process to go from Opportunity Identification to Concept Generation; as a result, the FE process is often aborted or forced to be restarted. Koen’s Model for the FE is composed of five phases. In each of the phases, several tools can be used by designers/managers in order to improve, structure, and organize their work. However, these tools tend to be selected and used in a heuristic manner. Additionally, some tools are more effective during certain phases of the FE than others. Using tools in the FE has a cost to the company, in terms of time, space needed, people involved, etc. Hence, an economic evaluation of the cost of tool usage is critical, and there is furthermore a need to characterize them in terms of their influence on the FE. This paper focuses on decision support for managers/designers in their process of assessing the cost of choosing/using tools in the core front end (CFE) activities identified by Koen, namely Opportunity Identification and Opportunity Analysis. This is achieved by first analyzing the influencing factors (firm context, industry context, macro-environment) along with data collection from managers followed by the automatic construction of fuzzy decision support models (FDSM) of the discovered relationships. The decision support focuses upon the estimated investment needed for the use of tools during the CFE. The generation of FDSMs is carried out automatically using a specialized genetic algorithm, applied to learning data obtained from five experienced managers, working for five different companies. The automatically constructed FDSMs accurately reproduced the managers’ estimations using the learning data sets and were very robust when validated with hidden data sets. The developed models can be easily used for quick financial assessments of tools by the person responsible for the early stage of product development within a design team. The type of assessment proposed in this paper would better suit product development teams in companies that are cost-focused and where the trade-offs between what (material), who (staff), and how long (time) to involve in CFE activities can vary a lot and hence largely influence their financial performances later on in the NPD process.