Optimal configuration of blast furnace slag runner to reduce fluid flow stresses at wall using mathematical modelling

Abstract

A three-dimensional mathematical model was developed to predict the wall shear stresses due to flow of liquid slag in slag runner of 'G' blast furnace of Tata Steel under different conditions. The liquid slag flow in the slag runner was considered to be turbulent and incompressible. The model was developed for single phase, steady state and isothermal conditions. To this end, the Navier Stokes equations along with continuity and turbulence equations (standard k–? model) were simultaneously solved with appropriate boundary conditions at the associated physical boundaries of the calculation domain. Several configurations were numerically assessed with respect to reduced shear stresses on the wall of the slag runner to select the best one. Due to accelerating flow the operating heights of liquid slag (density 2800 kg m^–3 at 1500°C) within the slag runner for different configurations were estimated with the help of Bernoulli's and continuity equations and fixed before the computation. The different configurations comprised of three segments with different parameters of either elevation or radius of curvature. Relatively high shear stresses were numerically predicted at the joint area of second and third segments of the slag runner for all the configurations. The radius of curvature was found as the dominant factor to reduce the shear stress at the joint region.     

33—THE SNARLING OF HIGHLY TWISTED MONOFILAMENTS. PART II: CYLINDRICAL SNARLING

An account is given of an experimental investigation of the cylindrical snarling of highly twisted monofilaments.

The theory underlying cylindrical snarling is set out, and an expression is derived for calculating the critical twist level at which normal snarling will be replaced by cylindrical snarling. Experiments on rubber filaments are described, and it is shown that there is good agreement between the theoretical and experimental results. Further experiments, in which the specimen was allowed to contract freely or forced into other forms, are also described.

It is shown from these experiments that it is difficult to establish the true equilibrium behaviour, since the situation appears to be dominated by frictional effects or by direct barriers to relative movement.     

32—THE SNARLING OF HIGHLY TWISTED MONOFILAMENTS. PART I: THE LOAD–ELONGATION BEHAVIOUR WITH NORMAL SNARLING

An account is given of an experimental investigation of the normal snarling of highly twisted monofilaments, those used being vulcanized rubber and nylon.

An earlier theoretical analysis is corrected, and the experimental results show that, after this correction, the theory put forward for the mechanical properties of the snarling mechanism holds reasonably well for elastic filaments. Although, as would be expected, there are larger deviations from the theory for viscoelastic filaments, the theory still gives a good indication of the behaviour of these filaments under torsion.     

Densification behaviour of titanium alloy powder compacts at high temperature

Abstract

Densification behaviours of titanium alloy (Ti–6Al–4V) powder compacts were investigated under uniaxial compression at high temperature. The yield function and a strain hardening law proposed by Kim were implemented into a finite element program (Abaqus) to compare with experimental data of porous titanium alloy powder preforms under PM forging. Experimental data were compared with finite element calculations for the variations of relative density with the applied pressure. Deformed geometry and density distributions of titanium alloy powder compacts under PM forging were also compared with finite element calculations.     

Geometric Factors Impacting Adhesive Lap Joint Strength and Design

Too often adhesive thickness, adherend thickness and other geometric factors are not explicitly considered in adhesive joint design. This study includes experimental and computational research exploring the means of enhancing the engineering design process for adhesive lap joints to include such effects. It clearly demon-strated that both the cleavage stresses and the shear stresses, near the bond termini, play important roles in lap 'shear' joint failure. Finite Element and Fracture Mechanics analyses were used to examine the energy release rate applied to growth of cracks in adhesive lap joints. Lap joints with similar geometries to those analyzed were designed, fabricated and tested. In a separate set of experiments the bond termini were constrained in the direction normal to the uniaxial loading. If the strength of lap shear joints is dominated by the adhesive shear strength, then constraining the lateral motion of the bond termini should have little or no effect on the overall shear strength of the adhesive joint. This work clearly demonstrates that this is not the case. If cleavage stresses are important in lap joints then constraining the bond termini, in a direction normal to the bond area, should have a commensurate effect on the overall strength of the lap joint. None of the ASTM standardized 'lap shear tests' provide any insight into this premise. This paper also presents analyses and experimental results for lap joints to which several methods of lateral constraint were applied near the bond termini. The analytical and numerical methods described and used for explaining and predicting such effects might be a useful adhesive joint design tool.     

Experimental study of joint performance in spot friction welding of 6111-T4 aluminium alloy

Abstract

The effect of process parameters (cycle time, tool speed and axial force) on the specimen temperature measured 2 mm away from the weld in spot friction welding (SFW) of Al 6111-T4 is investigated. The temperatures were correlated to the lap shear load. Results revealed that, to achieve a good joint strength with the maximum lap shear load >2˙5 kN, temperatures should be greater than a threshold value, which is 350°C at a location close to the SFW joint in this study. By studying the specimen macrographs, two internal weld geometric features based on the cross-section area were identified and correlated to the shear and mixed failure modes of the lap shear tested specimens. A model was developed and validated using experimental data of the cross section area of SFW joint with either shear or mixed mode fracture. The model predicts that the SFW joint strength is maximised at the transition region between the shear and mixed mode fracture.     

Probabilistic modelling of fatigue crack initiation from pits and pit clusters in aluminium alloys

Abstract

A numerical model of crack initiation under high cycle fatigue loading from pits is investigated in this paper. A probability based pit growth model, which takes into account the influence of mechanical cyclic load and particle clusters present in alloys, is used for investigations. Critical pit sizes, calculated using linear elastic fracture mechanics principles, are used to determine the probability of crack initiation for different conditions. The results are critically compared to extract an insight on the parameters that control the pit growth behaviour and thereby the fatigue crack initiation.     

A Wireless Instructor System for Computer-Supported Collaborative Learning Requiring Immersive Presence (CSCLIP)

The Computer-Supported Collaborative Learning Requiring Immersive Presence (CSCLIP) concept has been established with the objective of extending and enhancing thee-learning experience of distance education, especially for classes that involve laboratory (lab) experiments. The CSCLIP concept defines immersive presence as an inherent requirement that enables cognitive, affective, and most importantly psychomotor learning objectives to integrate into designs and concepts for next generation e-learning systems (Sharda et~al., 2003). Within the CSCLIP architectural framework, the Wireless Instructor (WI) system has been conceptualized and developed as an essential device to effectively support teaching while roaming instructional features for both local and distance students. The WI system provides cost effective means to establish a real-time immersive presence for the distance learning (DL) student and his/her lab group peers. The technical design and system architecture to create a WI system are introduced in this paper. The objective of the WI system is to make the learning experience more vivid and interactive by enabling the DL students, as well as the local students that are not in the same room with the instructor(s) at the same time, to be able to flexibly interact with the instructor(s) in real-time. With this system the students can experience real-time or non-real-time virtual tours with the instructor(s), enabling the students to visit places that may not be easily accessible due to distance, limited space and/or time, cost, or possible danger. The WI system consists of two major sub-components. First is a wireless audio and video (AV) system, which transfers real-time AV signals to and from the instructor(s) to all students. Second is the wireless instructor locator & data assistant system. These two systems can be combined into one WI unit, but as the applied development technologies are somewhat distinct, their features and architectural designs will be described separately throughout this paper. Integration of the two systems will enable further capabilities.This revised version was published online in March 2005 with corrections to the cover dateThis project was funded by the U.S. Department of Education (DoE) award no. P116Z020042 project titled Telecommunications Virtual Laboratory Development.     

Thixotropy of Systems with Shear Thinning and Plastic Flow Behavior

The definition of the thixotropy is a decrease in viscosity with time in shear and a subsequent recovery of viscosity after the shear deformation is removed.We ...     

Dynamic characteristics of adhesive bonded high strength steel joints

Abstract

With an increase in the use of advanced high strength steels in vehicle architectures, materials joining issues have become increasingly important. Among the various joining methods, adhesive bonding is increasingly used in automobile manufacturing. Successful implementation of adhesive bonding to improve structural crashworthiness and reduce vehicle weight requires the knowledge of issues related not only to processing but also to joint performance. In this study, the impact strength of adhesive bonded high strength steel joints is evaluated with the split Hopkinson tension bar (SHTB) technique. The influences of loading speed and thickness of the steels on the shear strength of the joints were examined. Comparative quasi-static lap shear tests were also conducted on a tensile testing machine. Test results showed that strength and energy absorption of bonded steel joints increase with loading speed, and is greatly affected by the thickness of the steels. As the loading rates are increased to 1100 s^–1 (i.e. 20 m s^–1), bonded 0·75 mm thick DP600 steel shows a 152% increase in strength and an 83% increase in energy absorption when compared to its quasi-static values. Examination of the impact tested specimens showed the failure mode changes from coarse cohesive mode to fine cohesive mode with increasing loading speed. The results from this study will provide the information for a better understanding of impact failure mechanisms of adhesive bonded high strength steels.