Hyperstereopsis in helmet-mounted NVDs : time to contact estimation

The side mounting of the night-vision sensors on some helmet-mounted systems creates a situation of hyperstereopsis in which the binocular cues available to the operator are exaggerated such that distances around the point of fixation are increased. For a moving surface approaching the observer, the increased apparent distance created by hyperstereopsis should result in greater apparent speed of approach towards the surface and so an operator will have the impression they have reached the surface before contact actually occurs. We simulated motion towards a surface with hyperstereopsis and compared judgements of time to contact with that under normal stereopsis as well as under binocular viewing without stereopsis. We simulated approach of a large, random-field textured and found that time to contact estimates were shorter under the hyperstereoscopic condition than those under normal stereo and no stereo, indicating that hyperstereopsis may cause observers to underestimate time to contact leading operators to undershoot the ground plane when landing.

Simulation of contact pressure in sheet metal trimming/blanking process

In the car body stamping process, trim/blank die cutting edges are subjected to very high tribological loads that result in loss of tool material from both the punch and die cutting edges. According to Archard’s wear model, normal contact force and sliding distance directly affects the wear. Therefore, knowledge of the acting forces on local contact areas has a pivotal role towards the prediction of tool wear. This paper presents a finite element modelling approach to determining the contact pressure distribution on the tool cutting edges during a trimming/blanking process. Characteristic areas on sheared edge profile, variation of punch force and high contact pressures affected areas have also been analysed.

Contact pressure evolution and its relation to wear in sheet metal forming

For a given sheet metal forming process, an accurate determination of the contact pressure distribution is an essential step towards the estimation of tool life. This investigation utilizes finite element (FE) analysis to model and explain the evolution and distribution of contact pressure over the die radius, throughout the duration of a channel forming process. It was found that a typical two-peak steady-state contact pressure response exists for the majority of the process. However, this was preceded by an initial transient response, characterized by extremely large and localized contact pressures, which were more than double the magnitude of the steady-state peak pressure. The validity of the predicted contact pressure behavior was assessed via detailed numerical analysis and by examining the wear response of an experimental stamping operation. The experimental results revealed that the high contact pressure zones of the transient response corresponded to a severe galling wear mechanism. Therefore, the transient response may be of primary significance to the tool wear response; thus questioning the applicability of traditional bending-under-tension wear tests for sheet metal stamping processes. Finally, a parametric study was conducted, examining the influence of the major process parameters on the steady-state and peak transient contact pressures, using the developed FE model. It was found that the bend ratio and the blank material ultimate tensile strength had the most influence on the peak contact pressures. The main process-related parameters, friction coefficient and blank holder force, were found to have only a minor influence.

Almost there : empirical insights into clinical method and ethics courses in climbing the hill towards lawyers' professionalism

Results of a study into the relationships between values and ethical behaviour for early-career legal practitioners - effect of gender, clinical experience and prior ethics education - implications for ethics education in tertiary institutions and after admission to legal practice.

Contact pressure prediction in sheet metal forming using finite element analysis

Tool wear has become a significant issue associated with the forming of high strength sheet steels in the automotive industry. In order to combat this problem, recent research has been devoted to utilizing the contact results obtained from current sheet metal forming software predictions, in order to develop/apply tool wear models or tool material selection criteria for use in the stamping plant. This investigation aims to determine whether a specialized sheet metal forming software package can correctly capture the complex contact conditions that occur during a typical sheet metal stamping process. The contact pressure at the die radius was compared to results obtained using a general-purpose finite element software package, for a simple channel-forming process. Although some qualitative similarities between the two predictions were observed, it was found that significant differences in the magnitude and distribution of the contact pressure exists. The reasons for the discrepancies in results are discussed with respect to the simplifications and assumptions adopted in the finite element model definitions, and with regards to other results available in the literature.

FEA simulation of contact and wear between non-metallic materials for accelerated new product development

The conventional approach ie laboratory life testing to examine the reliability of products takes long time and involves tremendous cost as samples are tested till failures. The accelerated life test (ALT) has recently been used as an alternative method. Although ALT reduces the cost of reliability testing through applying more severe environmental conditions than the normal ones, it is no longer sufficient as it does not describe the process of products’ failure explicitly and it is still highly dependent on physical testing. Consequently, novel practices need to be developed for better understanding of the products’ reliability. A novel Finite Element Analysis (FEA) model incorporating mathematical wear equations is developed in the current work and applied to polymer materials. Wear rate, a key parameter, is calculated by using a combinatorial formula that combines a conventional linear equation with a recently published exponential equation. The local wear is firstly calculated and then integrated over the sliding distance. The FEA simulation works in a loop and performs a series of simulation with updated surface geometries. The simulation is in good agreement with the physical testing result.

Contact pressure evolution at the die radius in sheet metal stamping

The contact conditions at the die radius are of primary importance to the wear response for many sheet metal forming processes. In particular, a detailed understanding of the contact pressure at the wearing interface is essential for the application of representative wear tests, the use of wear resistant materials and coatings, the development of suitable wear models, and for the ultimate goal of predicting tool life. However, there is a lack of information concerning the time-dependant nature of the contact pressure response in sheet metal stamping. This work provides a qualitative description of the evolution and distribution of contact pressure at the die radius for a typical channel forming process. Through an analysis of the deformation conditions, contact phenomena and underlying mechanics, it was identified that three distinct phases exist. Significantly, the initial and intermediate stages resulted in severe and localised contact conditions, with contact pressures significantly greater than the blank material yield strength. The final phase corresponds to a larger contact area, with steady and smaller contact pressures. The proposed contact pressure behaviour was compared to other results available in the literature and also discussed with respect to tool wear.

A post-contact Aboriginal mortuary tree from southwestern Victoria, Australia

Here we document the investigation of the first Australian Aboriginal mortuary tree found since the early 20th century and the first studied by archaeologists and Aboriginal traditional owners. In 2001, a landowner discovered Aboriginal skeletal remains inside a fallen, dead tree while evaluating the tree’s potential as firewood, leading to the investigation of the site. The tree was located near Moyston, in southwestern Victoria, in traditional Djab Wurrung country and held the partial skeletons of three Aboriginal individuals—two adults and a child. Clay pipe-stem wear on several teeth belonging to the two adults indicates that these remains were broadly contemporaneous secondary placements from the early post-contact period (ca. A.D. 1835–1845). Along with five additional mortuary trees within 30 km of the Moyston tree, this practice constitutes a previously unknown traditional mortuary pattern and contributes to our understanding of the complex mortuary behavior of the Aboriginal people of southwestern Victoria.

Fracturing the façade : exploring the impact of childhood sexual abuse

Examination of previous empirical literature illustrates how researchers have concentrated on documenting the impact of childhood sexual abuse (CSA) on the later psychological functioning of survivors, through comparisons with those who have not had such a history. Only more recently has there been a focus on assessing the relationship between aspects of the abuse and specific psychological difficulties. This thesis investigated the relationships between CSA characteristics and women’s later psychological adjustment. The role of attributions, coping methods, parenting competency and marital satisfaction were also investigated. Qualitative data on perception of benefit and general reflections of participants were used to explore participants’ self-esteem, locus of control, decisions relating to parenting, disclosure experiences, and attributions in relation to their abuse, including the search for meaning. Recruitment through newspapers and counselling services led to 118 women volunteering to complete a questionnaire evaluating the characteristics of their CSA and their current psychological adjustment. Of this group, 33 subsequently volunteered to participate in a telephone interview that explored in greater depth issues related to the long-term impact of their CSA. Both quantitative and qualitative analyses were conducted on the data. The women reported a high prevalence of dysfunction in their families of origin. Abuse had generally commenced by middle childhood, and lasted for a number of years and often involved a number of perpetrators. Perpetrators were most likely to be intrafamilial, with stepfathers being over-represented. Sexual activities generally involved physical contact, with participation often induced by the use of coercion. Participants demonstrated significant difficulties in psychological adjustment, but attributions regarding the abuse improved over time. Some concerns were expressed regarding parenting competency, and avoidant coping methods were favoured. In general, participants were satisfied with their current marital relationship. Significant associations were found between coping methods, attributional style, beliefs and various psychological adjustment measures. Participants, in general, demonstrated low self-esteem and displayed an external locus of control. As a consequence of their experience of CSA, many participants reported they had decided not to have children. For those who did have children, CSA was almost universally seen as having had an impact on their parenting. Disclosure of CSA was usually delayed for a number of years, with poor outcomes generally resulting from disclosure when it occurred. Women with current partners rated them as very caring and not controlling. Participants were generally still searching for meaning in their abuse, despite many having accepted it. Survivors outlined an extensive range of long-term effects of CSA, and nominated a number of strategies that would assist in reducing these effects. The results of the study indicated that there are a number of characteristics associated with CSA which signal a higher risk of difficulties in psychological adjustment. Concerns of survivors regarding parenting were confirmed according to those who undertook this role. Unfortunately, concerns expressed by survivors that disclosure of their CSA would have had negative consequences was usually the case when they did finally disclose. However, the accessing of social and family support appeared to have an important role in changing the attributions of survivors regarding their CSA. Furthermore, change of attributions in relation to abuse may provide the key to resilience in survivors against the negative impact of CSA on later psychological adjustment.