bluuebunny/crossref_metadata_2025 huggingface dataset:
The Value of Fingerprint Evidence in Detecting Crime
Authors: Bond John W.
Published: February 2009

Fingerprints are collected routinely from crime scenes for a wide range of offences and their timely identification is now seen as key to their success in the investigation and detection of crime. In this study, a logistical regression analysis of fingerprint identifications for the volume crime offences of residential burglary, commercial burglary and theft of motor vehicle in Northamptonshire, UK over a three-year period has revealed a number of predictors, other than timeliness, that influence greatly whether fingerprint identifications result in the detection of crime. The results indicate that a number of these predictors are of statistical significance and may be just as relevant in determining whether a fingerprint identification successfully detects the crime as the timeliness of the fingerprint identification. The most significant predictor was found to be investigating police officer accreditation, with fingerprint location and mobility also being relevant. Accreditation of the Crime Scene Examiner recovering the fingerprints and whether DNA material from the crime scene was also identified were found not to be significant. Consideration is given to where further emphasis is needed by the UK police service to maximise the opportunities to detect volume crime with fingerprints.
Kennedy and Unlawful Act Manslaughter: An Unorthodox Application of the Doctrine of Causation
Authors: Cherkassky Lisa
Published: February 2009

The decision of the House of Lords in R v Kennedy (No. 2)1 was welcomed by many academics as a return to the traditional application of causation. The victim in Kennedy was found to have broken the chain of causation between himself and his drug supplier when he self-injected with an already prepared syringe and produced his own death. However, on a careful examination of the law, can the rationale behind Kennedy be supported? This article explores Kennedy’s unconventional relationship with the doctrine of causation and casts a critical eye over the application of the doctrine in ‘fright and flight’ and ‘victim’ cases. There appears to be no correlation between the judgment in Kennedy and the well-established causal principles of foreseeability and novus actus interveniens in the criminal law. Will Kennedy end up being another Environment Agency v Empress Car Co. Ltd?2
Proposals for Reforming the Law of Self-Defence
Authors: Pichhadze Amir
Published: February 2009

The English law of self-defence has attracted significant attention following the controversial decision of the Court of Appeal in R v Martin. At the heart of the controversy is the determination of the reasonableness of a defendant's apprehension of the necessity to use a particular amount of force in self-defence. When comparing the defendant's apprehension and actions to those of a reasonable person in the same circumstances, what characteristics of the defendant must be attributable to the reasonable person in order for the test to be appropriate? This article argues that while the Court of Appeal's reluctance to allow a psychologically individualised standard of reasonableness may have been correct, the court should have reformulated the purely objective standard into a contextual objective standard. It is suggested that unless such reform is undertaken, the English law of self-defence will remain unduly constrained. Reform proposals by the Law Commission have made it clear that such reform is not on the horizon. As an alternative, the Law Commission proposed a reformulated defence of provocation. While this alternative is commendable, it does not remove the need to reform the objective standard of reasonableness in the law of self-defence.
The Self-Incrimination Privilege in Care Proceedings and the Criminal Trial and ‘Shall Not Be Admissible in Evidence’
Authors: Edwards Susan
Published: February 2009

This article considers the suspension of the self-incrimination privilege in care proceedings and the consequences for respondents and defendants implicated in civil and criminal trials relating to child abuse. This right against self-incrimination is differently applied in the civil and criminal forum. Where there are parallel civil and criminal proceedings and where different rules apply to the disclosure of fact, a respondent in a civil trial later facing criminal proceedings is at a disadvantage. This article explores the tension in the law with regard to a defendant's right to silence and the operation of the self-incrimination privilege with regard to documents and statements made by parties in civil and in criminal proceedings in cases arising from the physical and sexual abuse of children by family members or carers, and the law's overriding objective of child protection. It considers the several issues which arise when self-incriminatory statements are made in one set of proceedings and the use that can be made of these statements in the criminal investigation and at trial. It considers the duty of the criminal court to consider fairness in respect of admissibility of specific evidence (Police and Criminal Evidence Act 1984, s. 78) and also to consider the fairness of the trial as a whole (European Convention on Human Rights, Article 6). These sacrosanct principles and rules of evidence are examined in the context of their application in family/care proceedings and related criminal proceedings for offences of child abuse and the implications for the rights of respondents/defendants.
Legality and Reality: Some Lessons from the Pitcairn Islands
Authors: Wright Fran
Published: February 2009

This article considers the decision to prosecute a number of Pitcairn islanders for offences under the UK Sexual Offences Act 1956, and some aspects of the organisation of the prosecutions. The islanders complained that the prosecutions were an abuse of process because the content of the law was unascertainable and the legislation governing their trials was retrospective. The abuse of process claims were rejected. There was a mechanism by which islanders could ask the island officials and legal advisers for advice. It was predictable that non-consensual sexual intercourse would be a criminal offence. They were not prejudiced in any way by the late constitution of a criminal justice system. Although some of the decisions made in the Pitcairn case were questionable from a formalist point of view, most were fair in the peculiar circumstances of this small and remote island. The idea of the rule of law and of a fair trial cannot be divorced from the context in which criminal justice decisions are taken.
Patrol Officer Call for Service Workloads: An Urban and Small Town Comparison
Authors: Rhodes Trisha N. , Johnson Richard R.
Published: February 2009

Although small town agencies make up the majority of police departments in the USA, there is a surprising lack of information regarding how the workloads of small town and urban police officers differ. The widely held assumption that urban officers deal with higher workloads than small town officers has never been empirically tested. The present study involved a direct comparison of the average number of calls for service handled per patrol car per shift in three city and three small town municipal law enforcement agencies during a two-week period in 2006. The findings indicated that there was considerable variation across all six communities; however, the average number of calls handled by the urban officers was still significantly larger than the average number of calls handled by the small town officers.
Cyber-Stings: Policing Sex Offences on the Internet
Authors: Gillespie Alisdair A.
Published: February 2009

The use of proactive police tactics on the Internet has increased in recent years but little has been written about the propriety of such operations. This article considers the type of operations that occur and considers the propriety of such action, including examining the evidential rules relating to entrapment. It also examines how the media uses similar tactics in order to obtain news stories and yet questions can be raised as to whether this interferes with the workings of the criminal justice system.
Interviewing Children in Belgium: An Evaluation
Authors: Dommicent Jessica , Vanderhallen Miet , Bastiaens Marijke , De Wiest Hans , Van De Plas Marc , Vervaeke Geert
Published: February 2009

In Belgium, police officers are obliged to attend advanced training in interviewing children. Research suggests training is not sufficient to acquire and maintain skills, but follow-up is also required. The present study aims to examine the influence of the type of follow-up (individual follow-up, collective follow-up and no follow-up) on the overall quality of procedure in interviewing children.* Results show that police officers receiving individual follow-up perform significantly better in comparison with those who have received collective follow-up or no follow-up at all.
‘Crime Shouldn'T Pay’
Authors: Chiverton Ian , Waters Ian
Published: February 2009

This article focuses on the development and implementation of ‘proceeds of crime’ in policing and crime control, and places this against a backdrop of recent policing strategies and philosophies. It is argued that the latter may have reached their ceiling in terms of efficacy, and that much greater attention should now be turned towards targeting criminal asset recovery; this, it is hoped, will serve to reduce the ‘pull’ of much criminal activity (that is, financial and material gain). The article considers the impact of the Proceeds of Crime Act (2002), and work of the Metropolitan Police Service in tackling criminal assets. Whilst generally there are clear signs of progress, there is still much to be done in terms of interweaving a ‘proceeds of crime’ approach into mainstream policing.
Knowledge Management and Police Resources: Insights from Research
Authors: Martin Helen , Rogers Colin
Published: February 2009

Police services are constantly evolving in the need to manage demands upon their resources and fulfil obligations to consumers within a rapidly changing social and political landscape. The division of police labour, supported by dedicated IT and management structures, has been seen as one solution to this problem. This article considers the introduction of such a system, the Tasking Demand and Management Unit (TDMU), within a particular police force and considers its effects upon police officers and unsworn staff operating the system, including how it has influenced the perceptions of individuals operating at the front line of service delivery. It further considers the effects it has had in areas supporting the delivery of an effective, economic and efficient service, and informs policy makers and practitioners alike.
Conformal mapping of multiply connected Riemann domains by a variational approach
Authors: Hildebrandt Stefan , von der Mosel Heiko
Published: February 2009

We show with a new variational approach that any Riemannian metric on a multiply connected schlicht domain in ℝ2 can be represented by globally conformal parameters. This yields a “Riemannian version” of Koebe's mapping theorem.
Test strip handling in screening for drugs of abuse in the clinical toxicological setting1
Authors: Wilhelm Lars , Jenckel Stefan , Junker Ralf
Published: February 2009

Test strips for detecting narcotics are being used more frequently – ranging from clinical issues to forensically relevant cases. Analyses are not always done by staff trained in toxicology. Pharmacological and toxicological knowledge is necessary for the interpretation of the results as well as the technical understanding of the test system (e.g., cut-off values, cross reactivity). False negative results have to be considered possible when interpreting results. Suitable measures should be taken to rule out sample manipulation to the widest extent possible. To ensure the accuracy and reproducibility of analytical results, quality checks will have to be carried out. Analytical results will be reproducible only when backed up by the necessary documentation. Further diagnosis involving chromatographic methods should be carried out to differentiate and confirm positive findings. National and international rules and regulations regarding decision limits should be observed.
Measurement of Uniformity and Anisotropy in Granular Materials
Authors: Muhunthan B , Masad E , Assaad A
Published: February 2009

A new apparatus to conduct impregnation of granular materials has been developed to facilitate specimen preparation for microstructure observations. New experimental and analytical procedures have been presented to quantify the nonuniformity and anisotropy of granular materials. The nonuniformity of porosity distribution within a specimen was evaluated using imaging techniques. The anisotropy analysis consisted of the directional distribution of local porosity and orientation of solids and voids.

The procedures have been used to study the fabric of granular specimens prepared from Ottawa sand, silica sand, and spherical glass beads. The relation between directional porosity and the preferred orientation of granular particles and voids was found to be highly dependent on their angularity and elongation.
Explosive Induced Pore Pressure in a Sandfill Dam
Authors: Charlie WA , Lewis WA , Doehring DO
Published: February 2009

This paper reports on the potential performance of earthfill and tailings dams, and other saturated earthen structures, subjected to blast vibrations. Relationships between explosive-induced residual pore pressure increase and crest settlement versus peak particle velocity are presented. Eight explosive tests, conducted on a 2.25-m-high dam constructed of loose dilative sand, showed that significant increases in residual pore pressure (PPR > 0.1) occurred when peak particle velocity exceeded 0.015 m/s at shallow depths to 0.035 m/s at greater depths. Limited crest settlement occurred when the peak particle velocity exceeded 0.025 m/s. Results of this research, previous research, and the field behavior of full-scale earthfill and tailings dams indicate that peak particle velocity below 0.025 m/s and 0.10 m/s are reasonable thresholds to limit pore pressure buildup in full-size earthfill and tailings dams sensitive and not sensitive to vibrations, respectively.
Hydraulic Conductivity Testing of Geosynthetic Clay Liners (GCLs) Using the Constant Volume Method
Authors: Wang XD , Benson CH
Published: February 2009

Hydraulic conductivity tests were conducted using open and constant-volume permeation systems on specimens from a geosynthetic clay liner (GCL). Two constant volume (CV) systems were employed: the falling-head constant-volume (FHCV) system and the constant-head constant-volume (CHCV) system. A conventional burette system using pressurized air was employed for the open system (OS) tests. The test results show that hydraulic conductivity tests can be conducted 30 or more times faster with the FHCV and CHCV systems than with an open system. Typically the permeation portion of the FHCV and CHCV tests can be conducted in one-half day. Slightly lower hydraulic conductivities are measured with the CV systems due to the slightly higher effective stress applied during testing with these systems. The CHCV system has several advantages over the FHCV system, including minimizing initial transient behavior, constant applied effective stress during testing, and simpler calculations.
Capillary Flow in the Geotechnical Centrifuge
Authors: Lord AE
Published: February 2009

A “bundle of capillaries” approach is used to model unsaturated soils. Movement of fluid is approximated by employing a simple Poiseuille's capillary flow mathematical model. It is found that the centrifuge model flow time is 1/n2 times that for the pertinent prototype flow time. Here model acceleration = n × acceleration of gravity (i.e., a = ng). This result applies for: 1. Capillary rise at an arbitrary angle to the horizontal. 2. Horizontal capillary flow. 3. Downward capillary flow (infiltration) at an arbitrary angle. 4. Vertical drainage at an arbitrary angle.

This is the same centrifuge model scale factor as for advection, diffusion, and dispersion.
Clogging Phenomena of the Residual Soil-Geotextile Filter System
Authors: Lee I-M , Kim J-H , Reddi LN
Published: February 2009

Clogging tests on residual soil-geotextile filter systems were performed, and the permeability reduction due to clogging was evaluated. An extensive experimental program was performed using two typical weathered granite residual soils that were sampled at Shinnae-dong and Poi-dong areas in Seoul. Weathered granite residual soils, which are found in much of the Korean peninsula, pose unique challenges in terms of internal stability and filtration. Two separate simulation tests with weathered residual soils were performed: the cross-plane permittivity test (filtration) and the in-plane transmissivity test (drainage). Needle-punched non-woven geotextiles are selected since they are often used as drainage material in the field. The compatibility of residual soil-geotextile filter systems was investigated with emphasis on the clogging phenomenon. It was found that filter clogging was more significant in filtration than in drainage. The permeability reduction in the coarser Shinnae-dong soil-filter system was more serious than in the finer Poi-dong soil-filter system.
Influence of Procedural Variables on the Gradient Ratio Test
Authors: Fischer GR , Maré AD , Holtz RD
Published: February 2009

Ideally, filtration behavior of soil-geotextile systems as determined by the gradient ratio (GR) test (ASTM D 5101) should depend only on the soil and geotextile properties. In practice, however, test results can vary substantially with slight variations in test details and procedures. In addition, some optional procedures can have a significant effect on test results, while other required procedures appear to have little influence. A systematic study was performed to evaluate the effects of these procedures on GR test results. It was found that microfiltration of the in-flow water had a significant effect on filtration behavior. Chlorine algicide was effective in enhancing long-term filtration behavior, as was purging with CO2 and slow saturation of the system. Placement of the soil specimen also influenced GR values; they were found to be lower for compacted specimens than for loosely placed specimens. Presoaking geotextiles had no observable effect on filtration behavior, and disturbance of the GR device during the early stages of the test caused immediate and significant changes in permeability and GR.
Numerical Simulation of Water Movement in the Suction Equalization of a Thermal Conductivity Sensor
Authors: Shuai F , Fredlund DG , Samarasekera L
Published: February 2009

Laboratory and field measurements of soil suction using a thermal conductivity soil suction sensor involves installing the sensors into a soil mass. The sensors may be installed either in an initially wet or an initially dry state. In order to ensure a reliable suction measurement, it is important that the sensor reach suction equalization with the surrounding soil. The results of a numerical study have shown that, in most cases, the equalization time required for an initially dry sensor is less than the equalization time for an initially wet sensor. This difference is mainly due to the unsaturated zone that develops on the boundary of the initially wet sensor at the beginning of the drying process. The results of the numerical simulation have been substantiated by laboratory suction measurements.
Limiting Compression Curves
Authors: Sridharan A , Prakash K
Published: February 2009

Depending upon the initial water content of the soil sample, a family of compression curves is possible. Identification of characteristic limiting water contents for any fine grained soil system, along with the unique mechanisms controlling them, helps obtain the limiting compression curves. In the present note, it has been demonstrated that the compression curve obtained with its origin at the free swell limit of the soil represents the global upper bound compression curve, and that the compression curve obtained after the soil has reached equilibrium under cyclic consolidation represents the global lower bound compression curve. The compression curve obtained with its origin at the settling limit water content of the soil is the stress-free reference state curve as well as the upper bound compression curve for the homogeneous soil sample.
Sidewall Leakage in Hydraulic Conductivity Testing of Asphalt Concrete Specimens
Authors: Bowders JJ , Neupane D , Erik Loehr J
Published: February 2009

Asphalt specimens with irregular sidewalls can require special testing considerations when measuring hydraulic conductivity in a flexible wall permeameter. The hydraulic conductivity of laboratory prepared, dense asphalt concrete with high asphalt cement content (6–8.5% asphalt cement) was measured in the laboratory. Hydraulic conductivities were found to be excessive and were shown to be caused by sidewall leakage. Applying a thin layer of silicone vacuum grease to the sides of the asphalt specimens arrested the sidewall leakage, thereby permitting more accurate measurement of the hydraulic conductivity of the asphalt concrete.
Mechanical Properties of Cast Tin-Lead Solder
Authors: Rack HJ , Maurin JK
Published: February 2009

The tensile behavior of a near eutectic tin-lead solder has been determined as a function of various solidification parameters. The results indicate that at solidification rates observed in solder joints the solder alloy possesses superplastic properties similar to those previously observed in deformed and aged alloys.
Nonlinear Viscoelastic Properties of Bituminous Concretes
Authors: Sharma MG , Kim KS
Published: February 2009

Viscoelastic properties of bituminous concretes have been studied by observing creep behavior under a large range of compressive stress levels and temperatures. Effect of air void content on the creep properties has been observed. Results indicate that the test materials display linear viscoelastic properties only at low stress levels and temperatures. Master creep compliance curves corresponding to the linear range were obtained using the time-temperature shift hypothesis. The nonlinear creep behavior that is found to occur at higher stress levels and temperature has been characterized by the nonlinear viscoelasticity theory and the creep compliance functions based upon this theory were evaluated for the test materials. It is found that an increase in air void ratio leads to higher creep strains for a given stress level.
Preparation of Isotropically Consolidated Clay Samples with Random Fabrics
Authors: Edil TB , Krizek RJ
Published: February 2009

This paper describes equipment and procedures that can be employed to prepare clay samples with a highly random fabric and a known stress history. By appropriate choice of the clay mineral and proper control of pore fluid chemistry, high water content slurries can be consolidated isotropically to produce large size, relatively homogeneous samples for laboratory use in the study of fabric effects on clay behavior. The fabric of the resulting samples has been identified by the complementary use of scanning electron microscopy, optical microscopy, and X-ray diffractometry, and the isotropy in the mechanical response of specimens trimmed from the sample in perpendicular directions has been determined by consolidation tests, permeability tests, and consolidated-undrained triaxial compression tests. Comparisons in all cases have been made with analogous characteristics of specimens trimmed from anisotropically consolidated samples with a highly oriented fabric, and results have indicated that fabric effects can be significant in some cases.
Statistical Tolerance Limits for Censored Log-Normal Data
Authors: Little RE
Published: February 2009

A-basis and B-basis statistical tolerance limit computations are given for Type II failure censored log-normal data. The statistical tolerance limits are established by using factors given by Nelson and Schmee in conjunction with the best linear unbiased estimates for the normal distribution based on the coefficients tabulated by Sarhan and Greenberg. These tolerance limit computations complement analogous computations based on the Weibull distribution which have been illustrated in a recent tutorial paper by Little.
Evaluation of the Three-Component Model for Representing Wide-Range Fatigue Crack Growth Rate Data
Authors: Saxena A , Hudak SJ
Published: February 2009

The three-component model for representing wide-range fatigue crack growth rate (FCGR) behavior is evaluated by using a standard data set containing data at several load ratios on a 2219-T851 aluminum alloy. It is shown that this model can be used to model FCGR data accurately. The predicted fatigue lives for two geometries were obtained by integrating the fitted FCGR curves. These results compared well with the observed lives. Also, it was shown that the model has the flexibility to represent complex effects of load ratio over a wide range of load ratio and crack growth rate. This ability to interpolate easily between load ratios and to provide accurate fatigue life predictions makes the model an asset to design and reliability analyses.
The Effect of Interference on the Dimpled, Loaded-Hole Fatigue Strength of 2024-T3 Alclad® Aluminum Alloy
Authors: Kuc AP , Shewchuk J
Published: February 2009

The effect of interference fit on the fatigue strength of loaded holes is well known. Recently a new technique has been developed for increasing this strength in thin sheet material. The technique consists of dimpling the material centering about the region where the hole is to be made and thus introducing tensile plastic strain. The dimple is then flattened and the hole drilled, leaving the region around the hole under residual compressive stress. Experiments were carried out to obtain the combined effect of interference and dimpling in loaded-hole fatigue applications. In zero-totension fatigue tests on nominally 1.60-mm (0.063-in.) thick 2024-T3 Alclad® aluminum alloy specimens, combined optimum tapered-pin interference and dimpling gave a fatigue strength improvement factor of 4.0 while the dimpling technique increased the fatigue strength by a factor of 2.85 at 106 cycles to failure.
Statistical Tolerance Limits for Censored Weibull Data
Authors: Little RE
Published: February 2009

A-basis and B-basis statistical tolerance limits computations are given for Type II censored Weibull data. The statistical tolerance limits are established by using Mann and Fertig reliable life factors in conjunction with best linear unbiased estimates for the (smallest) extreme value distribution based on coefficients tabulated by White.
Strain-Dependent Differences in Several Reproductive Traits Are Not Accompanied by Early Postmating Transcriptome Changes in Female Drosophila melanogaster
Authors: McGraw Lisa A , Gibson Greg , Clark Andrew G , Wolfner Mariana F
Published: February 2009

Upon mating, Drosophila melanogaster females undergo numerous alterations in their behavior and reproductive physiology that are accompanied by small-magnitude transcript-level changes in up to 1700 genes. Many of these postmating transcriptome changes are the direct result of the sperm and seminal fluid proteins (Acps) that females receive from their mates. To begin to determine if the genetic background of the female's mate contributes to the previously described gene expression changes, we assessed whether interactions between the genotypes of two commonly used laboratory strains of D. melanogaster (Canton-S and Oregon R) influence the female's postmating transcriptome as well as several pre- and postcopulatory phenotypes. We find negligible differences in the female's transcriptome at 1–3 hr postmating regardless of the strain of the male with whom she mated. However, a male × female genotype interaction significantly influenced mate selection, and, in some cases, fecundity, fertility, and hatchability. Our data support previous work suggesting that many of the early postmating changes observed in D. melanogaster females are not caused by large modifications of transcript levels. Instead, early postmating phenotypes result from preexisting receptors or pathways that are already in place upon sexual maturity.
Alternative Induction of Meiotic Recombination From Single-Base Lesions of DNA Deaminases
Authors: Pauklin Siim , Burkert Julia S , Martin Julie , Osman Fekret , Weller Sandra , Boulton Simon J , Whitby Matthew C , Petersen-Mahrt Svend K
Published: February 2009

Meiotic recombination enhances genetic diversity as well as ensures proper segregation of homologous chromosomes, requiring Spo11-initiated double-strand breaks (DSBs). DNA deaminases act on regions of single-stranded DNA and deaminate cytosine to uracil (dU). In the immunoglobulin locus, this lesion will initiate point mutations, gene conversion, and DNA recombination. To begin to delineate the effect of induced base lesions on meiosis, we analyzed the effect of expressing DNA deaminases (activation-induced deaminase, AID, and APOBEC3C) in germ cells. We show that meiotic dU:dG lesions can partially rescue a spo11Δ phenotype in yeast and worm. In rec12 Schizosaccharomyces pombe, AID expression increased proper chromosome segregation, thereby enhancing spore viability, and induced low-frequency meiotic crossovers. Expression of AID in the germ cells of Caenorhabditis elegans spo-11 induced meiotic RAD-51 foci formation and chromosomal bivalency and segregation, as well as an increase in viability. RNAi experiments showed that this rescue was dependent on uracil DNA-glycosylase (Ung). Furthermore, unlike ionizing radiation-induced spo-11 rescue, AID expression did not induce large numbers of DSBs during the rescue. This suggests that the products of DNA deamination and base excision repair, such as uracil, an abasic site, or a single-stranded nick, are sufficient to initiate and alter meiotic recombination in uni- and multicellular organisms.
Characterization of the mechanical behavior of wear surfaces on single crystal nickel by nanomechanical techniques
Authors: Cordill M.J. , Moody N.R. , Prasad S.V. , Michael J.R. , Gerberich W.W.
Published: February 2009

In ductile metals, sliding contact induces plastic deformation resulting in subsurfaces, the mechanical properties of which are different from those of the bulk. This article describes a novel combination of nanomechanical test methods and analysis techniques to evaluate the mechanical behavior of the subsurfaces generated underneath a wear surface. In this methodology, nanoscratch techniques were first used to generate wear patterns as a function of load and number of cycles using a Hysitron TriboIndenter. Measurements were made on a (001) single crystal plane along two crystallographic directions, <001> and <011>. Nanoindentation was then used to measure mechanical properties in each wear pattern. The results on the (001) single crystal nickel plane showed that there was a strong increase in hardness with increasing applied load that was accompanied by a change in surface deformation. The amount of deformation underneath the wear patterns was examined from focused ion beam cross-sections of the wear patterns.
Some basic equations for the next generation of surface testers solving the problem of pileup, sink-in, and making area-function calibration obsolete
Authors: Schwarzer Norbert
Published: February 2009

In the present paper the formulas for the stiffnesses of a new and more general surface tester concept are given and discussed. The concept is based on the idea that the next generation of surface testers will provide the means to use all degrees of freedom of movement a probe on a sample surface could perform. Thus, in addition to the ordinary normal stiffness, lateral and tilting stiffness are measured, as well as twisting stiffness, and then used in the subsequent parameter determination of the investigated materials. It is shown in the paper that such a concept would not only solve classical problems such as “pileup” and “sink-in” completely, but it would also supersede the need of area-function calibration for the indenter tips and allow direct measurement of local intrinsic and residual stresses, anisotropy, and many other things, too.
Analysis of the tip roundness effects on the micro- and macroindentation response of elastic–plastic materials
Authors: Aida Rodríguez Pulecio Sara , Cristina Moré Farias María , Souza Roberto Martins
Published: February 2009

In this work, the effects of indenter tip roundness on the load–depth indentation curves were analyzed using finite element modeling. The tip roundness level was studied based on the ratio between tip radius and maximum penetration depth (R/hmax), which varied from 0.02 to 1. The proportional curvature constant (C), the exponent of depth during loading (α), the initial unloading slope (S), the correction factor (β), the level of piling-up or sinking-in (hc/hmax), and the ratio hmax/hf are shown to be strongly influenced by the ratio R/hmax. The hardness (H) was found to be independent of R/hmax in the range studied. The Oliver and Pharr method was successful in following the variation of hc/hmax with the ratio R/hmax through the variation of S with the ratio R/hmax. However, this work confirmed the differences between the hardness values calculated using the Oliver–Pharr method and those obtained directly from finite element calculations; differences which derive from the error in area calculation that occurs when given combinations of indented material properties are present. The ratio of plastic work to total work (Wp/Wt) was found to be independent of the ratio R/hmax, which demonstrates that the methods for the calculation of mechanical properties based on the indentation energy are potentially not susceptible to errors caused by tip roundness.
Fracture modes in curved brittle layers subject to concentrated cyclic loading in liquid environments
Authors: Kim Jae-Won , Thompson Van P. , Dianne Rekow E. , Jung Yeon-Gil , Zhang Yu
Published: February 2009

Damage response of brittle curved structures subject to cyclic Hertzian indentation was investigated. Specimens were fabricated by bisecting cylindrical quartz glass hollow tubes. The resulting hemicylindrical glass shells were bonded internally and at the edges to polymeric supporting structures and loaded axially in water on the outer circumference with a spherical tungsten carbide indenter. Critical loads and number of cycles to initiate and propagate near-contact cone cracks and far-field flexure radial cracks to failure were recorded. Flat quartz glass plates on polymer substrates were tested as a control group. Our findings showed that cone cracks form at lower loads, and can propagate through the quartz layer to the quartz/polymer interface at lower number of cycles, in the curved specimens relative to their flat counterparts. Flexural radial cracks require a higher load to initiate in the curved specimens relative to flat structures. These radial cracks can propagate rapidly to the margins, the flat edges of the bisecting plane, under cyclic loading at relatively low loads, owing to mechanical fatigue and a greater spatial range of tensile stresses in curved structures.
Spherical indentation for determining the phase transition properties of shape memory alloys
Authors: Qian Linmao , Zhang Shuang , Li Dongyang , Zhou Zhongrong
Published: February 2009

A spherical indentation method was developed to characterize the phase transition behaviors of shape memory alloys (SMAs). Based on deformation analysis, the measured indentation force-depth curves of SMAs can be converted to their nominal stress-strain curves. The predicted elastic modulus and phase transition stress of SMAs from spherical indentation agree well with those directly measured from tensile tests. This approach should be especially useful for characterizing the phase transition properties of SMA materials of small size or thin films.
In situ electrochemical nanoindentation of FeAl (100) single crystal: Hydrogen effect on dislocation nucleation
Authors: Barnoush Afrooz , Bies Christian , Vehoff Horst
Published: February 2009

The hydrogen effect on dislocation nucleation in FeAl single crystal with (100) surface orientation has been examined with the aid of a specifically designed nanoindentation setup for in situ electrochemical experiments. The effect of the electrochemical potential on the indent load–displacement curve, especially the unstable elastic-plastic transition (pop-in), was studied in detail. The observations showed a reduction in the pop-in load for both samples due to in situ hydrogen charging, which is reproducibly observed within sequential hydrogen charging and discharging. Clear evidence is provided that hydrogen atoms facilitate homogeneous dislocation nucleation.
The contributions of David Tabor to the science of indentation hardness
Authors: Hutchings Ian M.
Published: February 2009

Tabor’s book The Hardness of Metals, published in 1951, has had a major influence on the subject of indentation hardness and is by far the most widely cited source in this area. Although hardness testing was widely used for practical purposes in the first half of the 20th century, its use was generally based on little scientific understanding. The history of indentation hardness testing up to that point is reviewed, and Tabor’s contribution is appraised in this context.
The dynamic indentation behavior of steel at large depths of penetration
Authors: Sundararajan G. , Dikshit S.N.
Published: February 2009

The objective of the present study is to investigate the dynamic indentation behavior of steel plate material when impacted by ogive-shaped projectiles and in particular under indentation conditions involving large depths of penetration (i.e., depth of penetration greater than projectile radius). Toward the above purpose, dynamic indentation of steel plates of thickness 20, 40, and 80 mm have been carried out using projectiles of diameter 6.2 and 20 mm, and over a range of impact velocities so as to attain depths of penetration in the range 1.4 to 3.6 times the projectile radius. The results indicate that the dynamic hardness, the plastic zone size, specific energy consumed in plastic deformation within the plastic zone, and the average plastic strain within the plastic zone increases continuously with increasing values of depth of penetration normalized by projectile radius. Certain subtle differences regarding the nature of plastic deformation between indentation at large and shallow depths of penetration are presented. However, on a macroscopic scale, the indentation mechanisms and processes are broadly similar and show continuity in terms of behavior across the whole penetration depth range.
Contact area determination in indentation testing of elastomers
Authors: Deuschle Julia K. , Matthias Deuschle H. , Enders Susan , Arzt Eduard
Published: February 2009

To evaluate mechanical properties by means of nanoindentation, information on the contact area is crucial. However, the contact area is not directly accessible in experiments and is usually calculated according to the Oliver and Pharr procedure, which turned out to be unsatisfying when applied to viscoelastic materials like polymers. In this study, complementary in situ indentation testing and finite element analysis (FEA) were performed on silicone elastomers. Through this combination of techniques, several individual error sources in the conventional contact area determination have been identified and quantified. For shallow penetrations, contact areas after Oliver and Pharr were up to 40% smaller than the in situ testing results; for larger penetrations, the contact size was overestimated by approximately 6%. The deviations of the resulting mechanical properties were approximately 10%. Viscoelastic effects could be captured if dynamic indentation testing was performed.
Direct mapping of deformation in punch indentation and correlation with slip line fields
Authors: Murthy T.G. , Madariaga J. , Chandrasekar S.
Published: February 2009

Deformation field parameters in plane-strain indentation of a perfectly plastic solid with a punch have been mapped using particle image velocimetry, a correlation-based image analysis technique. Measurements of velocity and strain rate over a large area have shown that the deformation resembles that of the slip line field of Prandtl. A zone of dead metal is found to exist underneath the indenter adjoining which is a transition region of material flow similar to the centered-fan region in the slip line field. Shear bands demarcate the boundaries of these deformation regions. The observations suggest that a representative strain rate may be assigned to the indentation. By integrating the strain rate field along particle trajectories, the strains in the indentation region have been estimated. The strain values are seen to be large, 0.5 to 4, over a region extending to about twice the indenter half-width. A pocket of large strain, ∼4, is found to exist close to the edge of the indenter–specimen contact. Prandtl’s slip line field is modified based on the observations and used to estimate the strain field. The measurements of the deformation parameters are found to compare mostly favorably with the predictions of the slip line field and prior observations of indentation. The implications of these findings for analysis and interpretation of indentation hardness are briefly discussed.
Critical issues in making small-depth mechanical property measurements by nanoindentation with continuous stiffness measurement
Authors: Pharr G.M. , Strader J.H. , Oliver W.C.
Published: February 2009

Experiments were performed on a (100) copper single crystal to examine the influences that small displacement oscillations used in continuous stiffness measurement techniques have on hardness and elastic-modulus measurements in nanoindentation experiments. For the commonly used 2-nm oscillation, significant errors were observed in the measured properties, especially the hardness, at penetration depths as large as 100 nm. The errors originate from the large amount of dynamic unloading that occurs in materials like copper that have high contact stiffness resulting from their high modulus-to-hardness ratios. A simple model for the loading and unloading behavior of an elastic–plastic material is presented that quantitatively describes the errors and can be used to partially correct for them. By correcting the data in accordance with model and performing measurements at smaller displacement oscillation amplitudes, the errors can be reduced. The observations have important implications for the interpretation of the indentation size effect.
Strain gradient plasticity to study hardness behavior of magnetite (Fe3O4) under multicyclic indentation
Authors: Chicot D. , Roudet F. , Lepingle V. , Louis G.
Published: February 2009

The hardness of a material is generally affected by the indentation size effect. The strain gradient plasticity (SGP) theory is largely used to study this load dependence because it links the hardness to the intrinsic properties of the material. However, the characteristic scale-length is linked to the macrohardness, impeding any sound discussion. To find a relevant parameter, we suggest introducing a hardness length-scale factor that only depends on the shear modulus and the Burgers vector of the material and is easily calculable from the relation of the SGP theory. The variation of the hardness length-scale factor is thereafter used to discuss the hardness behavior of a magnetite crystal, the objective being to study the effect of the cumulative plasticity resulting from cyclic indentation. As a main result, the hardness length-scale factor is found to be constant by applying repeated cycles at a constant peak load whereas the macrohardness and the characteristic scale-length are both cycle dependent. When using incremental loads, the hardness length-scale factor monotonically decreases between two limits corresponding to those obtained at high and low loading rates, while the dwell-load duration increases. The physical meaning of such behavior is based on the modification of the dislocation network during the indentation process depending on the deformation rate.
Localized compression and shear tests on nanotargets with a Berkovich tip and a novel multifunctional tip
Authors: Rinaldi A. , Peralta P. , Friesen C. , Chawla N. , Traversa E. , Sieradzki K.
Published: February 2009

This article presents an experimental procedure to perform highly localized compression tests on nanoscale structures/features, such as nanospheres and nanopillars, via standard nanoindentation equipment. Current manufacturing capabilities, such as focused ion beam (FIB), lend themselves well to the creation of micron-spaced nanostructures, but it is fundamental to target an individual instance with little or no damage to the surrounding ones. The procedure successfully addresses the problem of locating and testing purposely designed nanostructures of order of 50 nm or less. The technique is illustrated for the case of closely spaced arrays of nanopillars, which were successfully manufactured, characterized, and tested through several pieces of equipment. For the purposes of compression, along with a traditional Berkovich tip, a new multifunctional (MF) tip was devised. This last tip is endowed with a complex contact geometry enabling both atomic force microscope (AFM) scanning and flat punch compression of the nanostructure. The levels of accuracy in tip positioning as well as robustness to alignment errors are unprecedented in comparison with previous in situ compression tests. As a consequence, the MF tip becomes a versatile tool that can be used beyond uniform compression. As an example, ancillary shear tests in controlled conditions are reported. Such results may lay the bases for metal-forming processes at the nanoscale, such as nanoforging or cutting operations, which are relevant to MEMS design and manufacturing.
Can indentation technique measure unique elastoplastic properties?
Authors: Liu Ling , Ogasawara Nagahisa , Chiba Norimasa , Chen Xi
Published: February 2009

Indentation is widely used to extract material elastoplastic properties from measured force-displacement curves. Many previous studies argued or implied that such a measurement is unique and the whole material stress-strain curve can be measured. Here we show that first, for a given indenter geometry, the indentation test cannot effectively probe material plastic behavior beyond a critical strain, and thus the solution of the reverse analysis of the indentation force-displacement curve is nonunique beyond such a critical strain. Secondly, even within the critical strain, pairs of mystical materials can exist that have essentially identical indentation responses (with differences below the resolution of published indentation techniques) even when the indenter angle is varied over a large range. Thus, fundamental elastoplastic behaviors, such as the yield stress and work hardening properties (functions), cannot be uniquely determined from the force-displacement curves of indentation analyses (including both plural sharp indentation and deep spherical indentation). Explicit algorithms of deriving the mystical materials are established, and we qualitatively correlate the sharp and spherical indentation analyses through the use of critical strain. The theoretical study in this paper addresses important questions of the application range, limitations, and uniqueness of the indentation test, as well as providing useful guidelines to properly use the indentation technique to measure material constitutive properties.