Improved extrapolation method for the fatigue damage of bus structural steel under service loading

Journal of Mechanical Science and Technology - This paper shows a technical study and analysis of the fatigue damage assessment of bus structural steel under service loading. Two bus prototypes...     

Experimental analysis of irregularities of metallic surfaces generated by abrasive waterjet

Experimental study of the surface quality produced by abrasive waterjet (AWJ) on metallic materials has been performed. The surface roughness/waviness was quantitatively evaluated by using the contactless optical measurement. In order to characterize the cut surface qualities, a single-parameter criterion has been proposed. Based on root mean square (RMS) roughness evaluation of the worst cut surface zone, the dimensionless statistical parameter C can be calculated as a basic quantity for AWJ surface cut characterization. As it was approved, besides its dependency on depth of AWJ trace, the value of C-parameter for the specific material is noticeably related also to the traverse speed of the cutting head. Such a relationship can be potentially used for adjusting the cutting speed of the machining process.     

Fracture behaviour and cleavage initiation in hypoeutectoid pearlitic steel

The paper reports on an investigation of the micromechanism of cleavage fracture in hypoeutectoid pearlitic R7T steel, commonly used for producing railway wheels. The steel possesses extensive Lüders deformation, which somewhat complicates finite element (FE) modelling and analyses of fracture behaviour. Standard Charpy V-notch specimens were used in order to analyse the fracture behaviour at quasistatic and impact loading. Finite element 3D calculations were performed and the elastic-plastic behaviour of notched bars up to the fracture was simulated. Detailed fractographic analysis was carried out on a number of Charpy V-notch specimens in order to investigate the origin site of cleavage fracture initiation and its distance from the notch root. The suitability of the three-criterion micromechanical model (Chen et al. Acta Materialia 51:1841–1855, 2003) for cleavage initiation was verified. The R7T steel under investigation exhibited a cleavage fracture stress of 1,837 MPa. Its independence on temperature evidenced the micromechanism of cleavage fracture to be microcrack propagation-controlled. For the investigated blunt-notched bend bars, an active volume exists ahead of the notch root in which pearlite colony-associated initiation sites are located. The cleavage fracture initiation of the steel is thus governed by the sites lying in the active volume. The active volume is determined by the values of three parameters. A plastic strain lying in interval from to (for the steel investigated from 0.033 to 0.108) is necessary to create a cleavage crack nucleus at any location within the active volume depending on the local pearlite properties. A stress triaxiality parameter ranging from h _min to h _max (from 0.93 to 1.39) is supposed to prevent the blunting process at the site of the cleavage nucleus. Once the main principal stress σ ₁ exceeds the local cleavage fracture stress σ _CFmin, an unstable global cleavage fracture occurs in a blunt-notched bar.     

Modified aluminosilicates as low-cost sorbents of As(III) from anoxic groundwater

The utilization of low-grade clay materials as selective sorbents represents one of the most effective possibilities of As removal from contaminated water reservoirs. The simple pre-treatment of these materials with Fe (Al, Mn) salts can significantly improve their sorption affinity to As oxyanions. The natural kaolin calcined at 550 degrees C (mostly metakaolin) and raw bentonite (mostly montmorillonite) pre-treated with Fe(II), Fe(III), Al(III) and Mn(II) salts were used to remove of As from the model anoxic groundwater with As(III) concentration about 0.5 and 10 mg L(-1). All the pre-treating methods were appropriate for bentonite; the efficiency of As(III) sorption varied from 92 to >99%, by the sorption capacity higher than 4.5 mg g(-1). In the case of metakaolin, Fe(II)- and Mn(II)-treatments proved the high sorption efficiency (>97%), while only <50% of As was removed after Fe(III) and Al(III) pre-treatment. The sorption capacities of treated metakaolin ranged from 0.1 to 2.0 mg g(-1).     

Indirect interference of two modes with different frequencies at the one-photon level

Abstract

The possibility of observing interference with two modes of different frequencies in a one-photon state by means of parametric up-conversion is studied. This phenomenon could be utilized for discernment between pure and mixed states. There is also a close connection to the question of the extent of indefiniteness of the photon's path.     

Comparison of Two-dimensional Fraunhofer Approximation and Two-dimensional Fresnel Approximation at Analysis of Surface Roughness by Angle Speckle Correlation II. Experimental Results

Abstract

In our previous paper, part I, analytical terms for normalized mean intensity and the contrast of mean-intensity Young's fringes in the Fourier plane of the photographic random surface roughness record have been derived in the case of the Fraunhofer and the Fresnel approximations. In this paper the experimental verification of these theoretical conclusions is presented. Terms for the mean light flux and the term for the contrast of mean-light-flux Young's fringes are added (in the case of the square irradiated area on the investigated surface). A discussion on the influence of the detector entrance slit is given.     

Human sources of landscape stewardship: the re‐emergence of private farming in the Czech Republic

Historically, an important role informing the Czech cultural landscape was played by the strong middle class of farmers. The period of collectivization which occurred progressively between 1950 and 1989 meant liquidation of the rural community. Whereas in 1950 there were 1,404,225 private farmers, this number had decreased to only 2,000 in 1988. This paper focuses on the problems of stewardship and responsibility towards landscape associated with this social group, which recently has started a new period of growth. The research uses a variety of qualitative and quantitative methods. Dialogues with interviewees have enabled us to interpret stewardship and responsibility into a coherent story about the relationship between people and landscape. Similarities and differences have been related to variables such as farmer's age and length of time in farming. The results show that patterns of stewardship and responsibility are not related to economic variables, but rather to common features of ‘timeless’ rural culture.     

FOPS: A new framework for the optimization with variable number of dimensions

A single‐ and multi‐objective optimization package is presented and described in detail. It contains an ensemble of local and global optimization routines. Procedures controlling variable number of dimensions are implemented as well, which is a rare feature among optimization oriented packages. The package is provided as a MATLAB toolbox. It excels in versatility and extensibility, which is demonstrated on a series of examples covering classical electromagnetism and antenna design. It is taken for granted that defining parameters of the optimization method can be set prior to the simulation run. However, its effective performance can be changed during the optimization run thanks to the full control feature. Moreover, it opens new possibilities in merging various algorithms into hybrids, performing complex dynamic programming tasks, or exploiting third party software. These advantages render the package as a perfect tool to deal with nowadays challenging engineering tasks.