Crystallographic orientation dependence of nanoindentation hardness in austenitic phase of stainless steel

ABSTRACT

This paper presents the indentation hardness evolution in different in-plane directions of austenite grains whose {111} planes are parallel to the sample surface determined by nanoindentation tests and electron back scattering diffraction (EBSD) analysis. A scanning electron microscopy (SEM) image of the indentation surface around one of the indents indicated the activation of two sets of slip planes with respect to each of the three indenter surfaces for a Berkovich tip. The identification of the slip traces by EBSD data analysis is in accord with Schmid`s law. We therefore proposed a new approach for defining the orientation parameter to interpret the indentation hardness. The orientation parameter was shown to be the minimum value of the three maximum Schmid factors on the secondarily activated slip planes in three directions for a Berkovich tip. Indentation hardness increased with the decrease in the orientation parameter and was dependent on in-plane orientation.     

Vacancy loop formation by 'cascade collapse' in a-Fe: A molecular dynamics study of 50keV cascades

The finite-element method has been used to simulate the indentation process of a variety of isotropic elastic-plastic materials indented by a rigid conical indenter with a perfectly sharp tip and round tips of various radii. Analyses of the obtained loading curves showed that the load frame compliance Cf of the nanoindentation instrument and the tip roundness r of the indenter can be determined from the loading curve. In a real indentation experiment, the obtained raw load-depth data during the loading stage can be described by the second-order polynomial dependence of depth on the square root of load, from which the Cf and r values are determined. An experimental procedure has thus been proposed for Cf and r calibration using the loading curves of a hard and isotropic material. Nanoindentation experiments on fused silica demonstrate the reliability of the proposed technique for accurate and quick Cf and r calibration.     

Preference paradigm: provides better self-stimulation reward discrimination than a rate-dependent paradigm

To obtain a better understanding of how well the Y-maze preference test paradigm indexes electrical brain stimulation reward, the present experiment compared the abilities of this rate-independent paradigm and a rate-dependent paradigm to assess the rewarding effectiveness of brain stimulation. The rate-dependent paradigm used was an operant chamber. The results showed that over a wide range of stimulation parameters the rate-independent paradigm provided a better assessment of the rewarding effectiveness of the brain stimulation than did the rate-dependent paradigm.     

The chemical potential and the work function of a metal film on a dielectric substrate

The chemical potential and the work function of an aluminium metal film which is in the vacuum (1) and on a dielectric substrate (2) are obtained using the model of non-interacting electrons confined by an asymmetric rectangular potential well. For the first time, these two characteristics are calculated with correct taking into account the electroneutrality condition. As a result, the values of the chemical potential and the work function tend to their bulk values upon increasing the film thickness. The presence of a dielectric substrate leads to a small shift in the values of these characteristics.     

Changes of hardness and electronic work function of Zr41.2Ti13.8Cu12.5Ni10Be22.5 bulk metallic glass on annealing

The hardness and electronic work function (EWF) of a bulk metallic glass, namely Zr_41.2Ti_13.8Cu_12.5Ni₁₀Be_22.5, have been studied experimentally, with an emphasis on the effect of heat treatments. The glass was annealed at different time and temperatures, and its hardness and EWF measured using the Rockwell indentation technique and a scanning Kelvin probe system, respectively. It is found that the EWF decreases with annealing time and temperature, whereas the hardness increases. This study shows a close relationship between hardness and EWF, indicating that the EWF could be a sensitive parameter for characterising and investigating the mechanical behaviour of BMG at the electronic level.     

The effects of d-amphetamine on the temporal control of operant responding in rats during a preshock stimulus.

The operant behavior of six rats was maintained by a random-interval schedule of reinforcement. Three-minute periods of noise were superimposed on this behavior, each period ending with the delivery of an unavoidable shock. Overall rates of responding were generally lower during the periods of noise than in its absence (conditioned suppression). These suppressed response rates also exhibited temporal patterning, with responding becoming less frequent as each noise period progressed. The effects of d-amphetamine on this behavioral baseline were then assessed. In four animals the relative response rates during the noise and in its absence suggested that the drug produced a dose-related decrease in the amount of conditioned suppression. However, this effect was often due to a decrease in the rates of responding in the absence of the preshock stimulus, rather than to an increase in response rates during the stimulus. Temporal patterning in response rates during the preshock stimulus was abolished, an effect that was interpreted in terms of rate-dependent effect of d-amphetamine. This study thus extends rate-dependent analyses of the effects of amphetamines to the patterns of operant behavior that occur during a preshock stimulus, and which have been discussed in terms of the disrupting effects of anxiety on operant behavior.     

Dominant factors influencing the nanoindentation response of piezoelectric materials: a case study in relaxor ferroelectrics

The nanoindentation response of a piezoelectric material is, in general, influenced in a complex manner by its elastic, dielectric and piezoelectric properties. The present study is focused on obtaining a comprehensive understanding of the dominant material factors influencing the force–depth mechanical indentation response and the charge–depth electrical indentation response of piezoelectric materials. From a large number of three-dimensional finite element simulations of the indentation of simple and complex piezoelectric materials (such as PZT-5A and relaxor ferroelectrics), the following principal conclusions are obtained: (1) For indentations with both conducting and insulating indenters, the mechanical indentation stiffness is influenced more by the elastic properties, while the electrical indentation stiffness is influenced largely by the piezoelectric properties of the indented materials. (2) For longitudinal indentations using a conducting indenter, the elastic constants, C ₃₃ and C ₁₃, and piezoelectric constants, e₃₃ and e₁₅, are, respectively, the first and second most dominant material constants that influence the mechanical indentation stiffness and the electrical indentation stiffness. (3) For transverse indentations using a conducting indenter, the elastic constants, C ₁₁ and C ₁₂, are, respectively, the first and second most dominant material constants that influence the mechanical indentation stiffness. (4) In the indentation of relaxor ferroelectrics based on PMN-xPT and PZN-xPT, which exhibit a range of elastic, dielectric and piezoelectric properties, it is generally observed that materials with higher normal elastic and piezoelectric constants, i.e., C ₃₃ and e₃₃, respectively, exhibit higher mechanical and electrical indentation stiffnesses.     

A study of the restitution coefficient in elastic-plastic impact

The aim of this work is to provide useful quantitative support for theories of the restitution coefficient for normal impacts involving plastic deformation, especially in the region close to the threshold at which plastic deformation begins. The impacts were from spheres of 5 mm diameter of aluminium oxide (which deformed elastically), dropped on to thick plates of mild steel or aluminium alloy. Very accurate measurements of impact and rebound velocities were made for drop heights from 1.75 m down to 0.6 mm, covering a range of velocities down to the yield threshold. Most of these results are in the elastic-plastic velocity range over which the indentation pressure varies from its value at initial yield of about 1.1sigma_y to the value when full plasticity is established of about 2.8sigma_y. The variation in the restitution coefficient with velocity in this range closely fits the rebound model of Tabor, which allows the indentation pressure to vary through the Meyer index n. The fitted values of n take into account these elastic-plastic effects as well as work hardening, demonstrating that a power-law compliance relationship is a very good model for the increase in indentation pressure as plasticity develops. Full plasticity only becomes established at impact velocities which are of the order of 100 times the velocity at which initial yield takes place. Models which assume a constant indentation pressure (perfect plasticity) are not a good match for the data in the elastic-plastic regime.     

On the form of the relation between response rates in a multiple schedule

Three pigeons received training on multiple variable-interval schedules with brief alternating components, concurrently with a fixed-interval schedule of food reinforcement on a second key. Fixed-interval performance exhibited typical increases in rate within the interval, and was independent of multiple-schedule responding. Responding on the multiple-schedule key decreased as a function of proximity to reinforcement on the fixed-interval key. The overall relative rate of responding in one component of the multiple schedule roughly matched the overall relative rate of reinforcement. Within the fixed interval, response rate during one multiple-schedule component was a monotonic, negatively accelerated function of response rate during the other component. To a first approximation, the data were described by a power function, where the exponent depended on the relative rate of reinforcement obtained in the two components. The relative rate of responding in one component of the multiple schedule increased as a function of proximity to fixed-interval reinforcement, and often exceeded the overall obtained relative rate of reinforcement. The form of the function relating response rates is discussed in relation to findings on rate-dependent effects of drugs, chaining, and the relation between response rate and reinforcement rate in single-schedule conditions.     

Spontaneous blinks as a criterion of visual fatigue during prolonged work on visual display terminals

Visual fatigue caused by prolonged work viewing a Visual Display Terminals (VDT) and of work reading a hard-copy were assessed by electromyogram (EMG) waveform and electrooculogram (EOG) waveform in spontaneous blinks as objective criteria, and by questionnaire of subjective feeling, and by task performance. The duration and the amplitude of the EMG of the orbicularis ocular muscle on the right side and the EOG of the vertical direction to the eyelid were measured for 10 subjects who participated in a figure task consisting of the addition of single-digit numbers on a VDT work or a work with a hard-copy. The mean values of the duration and the amplitude of the EMG and the EOG were evaluated by the averaging of 10 waveforms of the spontaneous blinks for all subjects. The time lag from the EMG to the EOG in the process of the generation of spontaneous blinks was also analyzed. These five parameters were evaluated during the work time. The mean values for the duration of the EMG increased gradually during the work time, but the amplitude did not show significant difference between the prework and a work time. There was no significant change of the duration of the EOG, but the mean amplitude of the EOG decreased as the work time progressed, and the time lag significantly extended. The blinks frequency increased relatively when using a VDT. The rate of fluctuation for these parameters was higher during use of a VDT than use of a hard-copy. The time lag at five hours of VDT work was extended by 90% based on the value at the pre-work. The symptoms of general fatigue and fatigue of the eyes increased linearly during the VDT work for six hours. The results indicated a significant correlation between the objective parameters for the activity of the spontaneous blinks, i.e., duration and amplitude of EMG and EOG, and the time lag between EMG and EOG, and the subjective feeling was recognized in the time course of the task. These experimental results suggested that the parameters regarding the EMG and the EOG for the spontaneous blinks were effective indices for assessing visual fatigue during prolonged VDT work.     

Scaling relationships in indentation of power-law creep solids using self-similar indenters

We use dimensional analysis to derive scaling relationships for self-similar indenters indenting solids that exhibit power-law creep. We identify the parameter that represents the indentation strain rate. The scaling relationships are applied to several types of indentation creep experiment with constant displacement rate, constant loading rate or constant ratio of loading rate over load. The predictions compare favourably with experimental observations reported in the literature. Finally, a connection is found between creep and 'indentation-size effect' (i.e. changing hardness with indentation depth or load).     

Rereading Mircea Eliade's Youth Without Youth, a story of suspicion and camouflage

The article argues that Mircea Eliade's 1976 novella Youth Without Youth (which has been recently turned into a film by Francis Ford Coppola) offers an intriguing literary illustration of the concept of ‘camouflage’ so prominent in Eliade's scholarly writings. Youth Without Youth, revolving around the paradoxes of aging and of (biological) time, develops as a fantastic reverie, a mysterious gnostic parable under the appearances of a work of science fiction, and ultimately becomes a sort of rebus, made up of a large number of suggested enigmas within enigmas. It is, at the same time, an opportunity for the author to revisit phantasmatically a dramatic period of his life – the year 1938. Historical reality becomes fantastic, charged with symbols and riddles. The Eliadean dialectic between the sacred and the profane is interestingly doubled in this story by a dialectic between spying and hiding, surveillance and escape, suspicion and camouflage.     

Interview with Jonathan Asser

In this interview, Jonathan Asser recounts how working in prisons with violent male inmates was the inspiration behind ‘Starred Up’, his acclaimed film about a young man who enters adult prison for the first time. The film offers an insight into the innovative Shame/Violence Intervention (SVI) that Asser pioneered whilst working as a group therapist at HMP Wandsworth. Asser’s approach included getting members of his groups to acknowledge the shame they felt before these feelings became unbearable and escalated into violence. Drawing on the ideas of American psychiatrist James Gilligan, Asser found he was able to work with the most violent and institutionalised prisoners by developing a technique that relied on a particular use of his counter-transference. Asser also talks about the personal experiences that led him into working therapeutically with this client group.     

The Stranger to Time: What a Collector Stands for in a Hurried Society

City-dwellers who are threatened by the risk of natural or social disasters are in search of safer houses. Each attempt to satisfy their need for safety, however, turns into another version of the security problem; so much so that, escaping from risk itself turns into different (yet nevertheless more powerful) risks. The film 10 to 11 (2009) focuses on the socio-spatial conflict between a stranger and his neighbours who are anxious about a possible earthquake risk in Istanbul. Mithat, the protagonist of the film, is a stranger not only to place but essentially to time. He lives within time and understands place as an essential means loaded by temporal experiences and memories. This paper deals with the multiple dichotomies between time and memory, between risk and fear, between aesthetics and security, and between attachment and profit in the context of urban transformation. The stranger, who is analysed for the first time as a temporal being in this paper, is discussed using Zygmunt Bauman’s concepts of uncertainty and liquid modernity, Richard Sennett’s capitalism, Ulrich Beck’s risk society, Frank Furedi’s culture of fear, Stephen Bertman’s hurried culture, Elias Canetti’s death, Giorgio Agamben’s forgotten and gone, Svetlana Boym’s nostalgia, and Halbwachs, Assmann, Connerton, and Arendt’s memory, as well as around the temporal spaces of museums, bibliopoles, antique shops, and cemeteries.     

Sliding on carbon nanotube arrays

Adhesion, friction and wear of Single-Walled Nanotube (SWNT) and multi-walled nanotube arrays have been investigated. SWNT arrays exhibit lower adhesion and friction values on account of the lower van der Waals’ forces resulting from lower packing density and higher flexibility. Wear tests show that both arrays do not wear. Tip wear and friction force in the SWNT array are lower due to lower adhesion and higher flexibility of the SWNTs, which lead to less resistance to the motion of the tip.     

Volunteer work as a valuable leisure‐time activity: A day‐level study on volunteer work,non‐work experiences,and well‐being at work

In this 2‐week diary study, with 105 employees providing data on a total of 476 days, we examined relationships between the amount of time spent on volunteer work activities during leisure time, psychological non‐work experiences in the evening (i.e. recovery experiences of psychological detachment from work and mastery as well as need satisfaction), and work outcomes during the following working day (i.e. positive and negative affect, and active listening). Results confirmed the hypothesized positive relationships between the amount of time spent on volunteer work activities and psychological detachment from work, mastery experiences, and need satisfaction in the evening. Psychological detachment from work in the evening was positively related to active listening during the following working day. Need satisfaction in the evening was negatively related to negative affect and positively related to active listening during the following working day. The amount of time spent on volunteer work activities was negatively related to negative affect during the following working day. This relationship was mediated by need satisfaction in the evening.     

Effect on Restaurant Tipping of a Helpful Message Written on the Back of Customers' Checks

Research has shown that servers can increase their tip percentages by writing "Thank you" or by drawing a happy face on the backs of customers' checks. In the current study, a third approach of this type was tested. An experiment was conducted in which a female server either did or did not write a helpful message about an upcoming dinner special on the backs of checks before delivering them to customers. It was predicted that adding the helpful message would increase tip percentages because of reciprocity, in which customers would tend to respond to the server's "tip" with an increased tip of their own. Results were consistent with this prediction: Mean tip percentages increased from about 17% to 20%.     

Impact of a television film on attitudes toward mental illness

The possible impact of a prime time television film portraying a mentally ill killer was investigated. Groups of college students were shown the film with and without a film trailer reminding viewers that violence is not characteristic of mentally ill persons. A third group viewed a film not about mental illness. Postfilm responses to the Community Attitudes toward the Mentally Ill scale indicated that those who saw the target film expressed significantly less favorable attitudes toward mental illness and community care of mentally ill persons than did those who saw the control film, regardless of whether of not they received the trailer along with the target film. Results support concerns that media depictions add to mental illness stigma and also suggest that corrective information alone may be sufficient to counteract the stigmatizing impact of such audience-involving mass media portrayals.     

Is a change in work motivation related to a change in mental well-being?

The purpose of the study was to investigate the effect of changes on work motivation and the effect of the changes on future mental well-being. This prospective study comprised 577 employees who were followed up 18 months after a comprehensive baseline measurement. The response rate was 81% for the baseline and 72% for the follow-up. The results show that both negative and positive changes in work motivation over time (18 months) were related to exhaustion. A similar correlation was found between negative changes in work motivation and depression. The results show that employees with a decreased level of work motivation had a higher risk of experiencing more exhaustion and depression in the future. Thus, investing in activities to promote work motivation may be an effective means of preventing long-term sick leave for stress-related mental illness and of providing energy for successful career advancement.     

An explanation of the indentation size effect in ceramics

Abstract

A quantitative model is proposed to explain the indentation size effect (ISE) often observed in the hardness response of hard brittle materials, namely that hardness is observed to increase with decreasing indentation size. The model is based on a mixed elastic/plastic materials deformation response whereby plastic deformation occurs in a discrete manner progressively to relieve stresses created by elastic flexure of the surface at the edges of the indentation. During unloading of the indenter, recovery of the elastic increment of deformation, which precedes each new band of plastic deformation, results in the indentation appearing smaller than expected, particularly as the indentation sizes decrease to approach the scale of the plastic deformation band spacing. The model fits observed experimental data well and analysis of hardness/size data in this way is shown to allow both a bulk hardness value and a characteristic deformation band scale to be calculated for a given sample.