Actuation curvature limits for a composite beam with embedded shape memory alloy wires

Shape memory alloy composites were manufactured using NiTi wires and woven glass fiber pre-impregnated fabrics. A closed form analytical model was developed to investigate the curvature achievable during actuation. The experimental results of actuation showed reasonable agreement with the model. Actuation temperatures were between ∼55 and 110 °C, curvatures of 0.25-0.5m-1 were obtained and the stresses in the wires were estimated to have reached 265MPa during actuation. An actuation curvature map was produced, which shows the actuation limits and approximate temperature-curvature curves for the general case of a composite containing shape memory alloy wires. © 2014 IOP Publishing Ltd.

A first step towards a simple in-line shape compensation routine for the roll forming of high strength steel

The roll forming process is increasingly used in the automotive industry for the manufacture of structural and crash components from Ultra High Strength Steel (UHSS). Due to the high strength of UHSS (<1GPa) even small and commonly observed material property variations from coil to coil can result in significant changes in material yield and through that affect the final shape of the roll formed component. This requires the re-adjustment of tooling to compensate for shape defects and maintain part geometry resulting in costly downtimes of equipment. This paper presents a first step towards an in-line shape compensation method that based on the monitoring of roll load and torque allows for the estimation of shape defects and the subsequent re-adjustment of tooling for compensation. For this the effect of material property variation on common shape defects observed in the roll forming process as well as measurable process parameters such as roll load and torque needs to be understood. The effect of yield strength and material hardening on roll load and torque as well as longitudinal bow is investigated via experimental trials and numerical analysis. A regression analysis combined with Analysis of Variance (ANOVA) techniques is employed to establish the relationships between the process and material parameters and to determine their percentage influence on longitudinal bow, roll load and torque. The study will show that the level of longitudinal bow, one of the major shape defects observed in roll forming, can be estimated by variations in roll load and torque.

Forming behaviour analysis and constitutive modelling of Ti-6Al-4V at room temperature.

 A constitutive model was proposed in this thesis and a promising approach for accurate prediction of forming behaviour of high strength titanium alloy sheet metal forming at room temperature is presented. Outcomes showed a potential solution of cold roll forming of this material for aerospace and automotive structural applications.

In-line shape compensation for roll forming through process parameter monitoring

Buddhika’s Phd topic is In-line shape compensation for roll forming through process parameter monitoring. It mainly discussed about defects monitoring and compensation in high strength steel roll forming for automotive applications.

A non-associated plasticity model with anisotropic and nonlinear kinematic hardening for simulation of sheet metal forming

A material model for more thorough analysis of plastic deformation of sheet materials is presented in this paper. This model considers the following aspects of plastic deformation behavior of sheet materials: (1) the anisotropy in yield stresses and in work hardening by using Hill's 1948 quadratic yield function and non-constant stress ratios which leads to different flow stress hardening in different directions, (2) the anisotropy in plastic strains by using a quadratic plastic potential function and non-associated flow rule, also based on Hill's 1948 model and r-values, and (3) the cyclic hardening phenomena such as the Bauschinger effect, permanent softening and transient behavior for reverse loading by using a coupled nonlinear kinematic hardening model. Plasticity fundamentals of the model were derived in a general framework and the model calibration procedure was presented for the plasticity formulations. Also, a generic numerical stress integration procedure was developed based on backward-Euler method, so-called multi-stage return mapping algorithm. The model was implemented in the framework of the finite element method to evaluate the simulation results of sheet metal forming processes. Different aspects of the model were verified for two sheet metals, namely DP600 steel and AA6022 aluminum alloy. Results show that the new model is able to accurately predict the sheet material behavior for both anisotropic hardening and cyclic hardening conditions. The drawing of channel sections and the subsequent springback were also simulated with this model for different drawbead configurations. Simulation results show that the current non-associated anisotropic hardening model is able to accurately predict the sidewall curl in the drawn channel sections.

The diversity and complexity of settings and arrangements forming the ‘experienced environments’ for doctoral candidates : some implications for doctoral education

A significant feature of contemporary doctoral education is the continuing trend for research and research education to migrate beyond discipline-based institutional teaching and research structures. The result is a more diverse array of settings and arrangements for doctoral education linked to an increasingly global research enterprise. Recognising the complexity of what is a distributed environment challenges some commonly held assumptions about doctoral education and its practice. Drawing on data gathered in an Australian study of PhD programme development in Australia carried out in 2006–2009, the article describes the fluid and complex arrangements forming the ‘experienced environments’ for doctoral candidates, an environment that can afford them varying opportunities and challenges for completing their candidacy. Some implications for doctoral education are discussed.

An extension of the flower pattern diagram for roll forming

The initial process design of a roll forming system is often based on the traditional ‘flower pattern diagram’. In this diagram, the cross sections of the strip at each roll stand are superimposed on a single plane; the diagram is a 2D representation of the 3D process. In the present work, the flower pattern is extended into three dimensions. To demonstrate the method, the forming path or trajectory of a point at the edge of the strip during forming a V-section is considered. The forming path is a surface curve that lies on a cylindrical surface having its axis along the machine axis. This surface is unwrapped to give its plane development and important features of the forming process can be determined and are readily interpreted from this plane curve. It is shown that at any stage in the process, the axial strain and the curvature of the sheet adjacent to the point are dependent on the slope of the trajectory in this plane projection. This new diagram, which apparently has not been used previously, provides a useful initial method of examining the roll forming process and optimising the flower pattern. The model is purely geometric, as is the original flower pattern approach, and does not include the effect of material behaviour. The concept is applied to several cases available in the literature. It shows that the lowest level of shape defect in the part is achieved when the trajectory of the strip edge follows the shortest line length between the start and finish of forming, leading to the least longitudinal strain introduced in the flange. This trend is in agreement with previous experimental observations, suggesting that the analytical model proposed may be applied for early process design and optimisation before time-consuming numerical analysis is performed.

Numerical modeling and analysis for forming process of dual-phase 980 steel exposed to infrared local heating

A recent experiment confirmed that the infrared (IR) local heating method drastically reduces springback of dual-phase (DP) 980 sheets. In the experiment, only the plastic deformation zone of the sheets was locally heated using condensed IR heating. The heated sheets were then deformed by V-bending or 2D-draw bending. Although the experimental observation proved the merit of using the IR local heating to reduce springback, numerical modeling has not been reported. Numerical modeling has been required to predict springback and improve the understanding of the forming process. This paper presents a numerical modeling for V-bending and 2D-draw bending of DP 980 sheets exposed to the IR local heating with the finite element method (FEM). For describing the thermo-mechanical behavior of the DP 980 sheet, a flow stress model which includes a function of temperature and effective plastic strain was newly implemented into Euler-backward stress integration method. The numerical analysis shows that the IR local heating reduces the level of stress in the deformation zone, although it heats only the limited areas, and then it reduces the springback. The simulation also provides a support that the local heating method has an advantage of shape accuracy over the method to heat the material as a whole in V-bending. The simulated results of the springback in both V-bending and 2D-draw bending also show good predictions.

Forests of the sea: predictive habitat modelling to assess the abundance of canopy forming kelp forests on temperate reefs

 Large brown seaweeds (kelps) form forests in temperate and boreal marine systems that serve as foundations to the structure and dynamics of communities. Mapping the distributions of these species is important to understanding the ecology of coastal environments, managing marine ecosystems (e.g., spatial planning), predicting consequences of climate change and the potential for carbon production. We demonstrate how combining seafloor mapping technologies (LiDAR and multibeam bathymetry) and models of wave energy to map the distribution and relative abundance of seaweed forests of Ecklonia radiata can provide complete coverage over hundreds of square kilometers. Using generalized linear mixed models (GLMMs), we associated observations of E. radiata abundance from video transects with environmental variables. These relationships were then used to predict the distribution of E. radiata across our 756.1km2 study area off the coast of Victoria, Australia. A reserved dataset was used to test the accuracy of these predictions. We found that the abundance distribution of E. radiata is strongly associated with depth, presence of rocky reef, curvature of the reef topography, and wave exposure. In addition, the GLMM methodology allowed us to adequately account for spatial autocorrelation in our sampling methods. The predictive distribution map created from the best GLMM predicted the abundance of E. radiata with an accuracy of 72%. The combination of LiDAR and multibeam bathymetry allowed us to model and predict E. radiata abundance distribution across its entire depth range for this study area. Using methods like those presented in this study, we can map the distribution of macroalgae species, which will give insight into ecological communities, biodiversity distribution, carbon uptake, and potential sequestration.

The influence of residual stress on a roll forming process

Roll forming is increasingly used in the automotive industry to form High Strength Steel (HSS) and Advanced High Strength Steel (AHSS) for structural components. Because of the large variety of applications of roll forming in the industry, Finite Element Analysis (FEA) is increasingly utilized for roll forming process design. Bending is the dominant deformation mode in roll forming and sheet materials used in the process are often temper rolled (skin passed), roller- or tension-levelled. These processes introduce residual stresses into the material, and recent studies have shown that those affect the material behaviour in bending. A thickness reduction rolling process available at Deakin that leads to material deformation similar to an industrial temper rolling operation was used in this study to introduce residual stresses into a dual phase, DP780, steel strip. The initial and thickness reduced strips were then used in a 5-stand experimental V-section roll forming set-up to identify the effect of residual stress on the final shape. The influence of residual stress and the effect of plastic deformation on the material behaviour in roll forming are separately determined in numerical simulation. The results show that the thickness reduction rolling process decreases the maximum bow height while the springback angle and end flare increase. Comparison with experimental results shows that using material data from the conventional tensile test in a numerical simulation does not allow for the accurate prediction of shape defects in a roll forming process if a residual stress profile exists in the material. On the other hand including the residual stress information leads to improved model accuracy.

Simmel, the police form and the limits of democratic policing

© 2015 The Author. I argue that the social theory of Georg Simmel can be used to illustrate certain limitations to the potential of democratic policing. Simmel makes a number of claims about trust, secrecy and accountability that are shown to have immediate relevance to my empirical case study of police-public consultation forums in Edinburgh, Scotland. Two particular aspects of the 'form' of the police-public relationship-the police's command of non-negotiable force and inequality in the reciprocity of information-play a key role in limiting some of the principal aspirations of democratic policing theory. There are permanent barriers to improving the democratic credentials of the police I argue, yet positive and progressive change is still achievable.