Tool Marks Research Articles

Fast-tool-servo-controlled shear-thickening micropolishing

Polishing-based post-processing is essential for removing the undesired surface diffraction on diamond-turned microstructured surfaces that is enhanced by periodic tool marks. To overcome challenges in existing micropolishing methods, a fast-tool-servo-controlled shear-thickening micropolishing method was proposed for the non-contact and controllable polishing of microstructured surfaces. The operating kinematics and material removal mechanism are modeled analytically and investigated experimentally. The comprehensive principal stress in front of the rake face of the tool is found to mainly contribute to the material removal. The fast tool servo can tune the principal stress and the viscosity of the slurry by flexibly adjusting the gap width between the surface and the tool edge. Thus, the material removal can be controlled at any operating position. Meanwhile, although the material removal rate is nonlinearly related to the rotation radius and gap width, the constraint between these two factors is linear for achieving a fixed material removal rate. Finally, the feasibility of the proposed micropolishing method is demonstrated by successfully polishing rotationally symmetric and asymmetric microstructured surfaces to achieve improved surface smoothness and conformal surface shapes.

A review of Scandinavian research on medieval church roofs

The remarkable clusters of preserved high medieval church roofs in Scandinavia have been known since the early 20th century but surveys aimed at mapping and document these structures began first around 2000. The author reviews the State of Scandinavian research and presents recent and ongoing survey projects in Swedish dioceses. These cross-disciplinary projects have enhanced the value of historic timber structures as archaeological source material. A reading of craft techniques and tool marks provides insight into the work of the medieval carpenters. An example is presented of how a structured survey followed by moderate cleaning shaped a basis for maintenance and restoration in compliance with international principles.

An Open-Source Implementation of the CMPS Algorithm for Assessing Similarity of Bullets

In this paper, we introduce the R package cmpsR, an open-source implementation of the Congruent Matching Profile Segments (CMPS) method developed at the National Institute of Standards and Technology (NIST) for objective comparison of striated tool marks. The functionality of the package is showcased by examples of bullet signatures that come with the package. Graphing tools are implemented in the package as well for users to assess and understand the CMPS results. Initial tests were performed on bullet signatures generated from two sets of 3D scans in the Hamby study under the framework suggested by the R package `bulletxtrctr`. New metrics based on CMPS scores are introduced and compared with existing metrics. A measure called sum of squares ratio is included, and how it can be used for evaluating different scans, metrics, or parameters is showcased with the Hamby study data sets. An open-source implementation of the CMPS algorithm makes the algorithm more accessible, generates reproducible results, and facilitates further studies of the algorithm such as method comparisons.

Turning/Shot peening of Nickel-based powder metallurgy superalloy: Effect on surface integrity and high-temperature low-cycle fatigue properties

In this study, a nickel-based powder metallurgy alloy was processed via turning, ceramic bead peening, and shot peening by high-intensity cast-iron shots and low-intensity ceramic beads (denoted as compound shot peening). We investigated the surface morphology (surface stress concentration factor, Kst), the surface residual stress profile, microstructure, and the hardness gradient of three surface states and compared the high-temperature low-cycle fatigue lives. The results showed that the surface stress concentration coefficients after turning, ceramic bead peening, and compound shot peening were 2.39, 1.98, and 2.12, respectively. The average surface roughness, Sa, after turning was low, but the bottom of the tool mark was sharp, so the Kst value was higher than that after shot peening, which formed a round bottom by bead blasting. Compared with ceramic bead peening, a surface structure with a deeper compressive residual stress profile and a higher hardness gradient was formed after compound shot peening, and nanostructured features appeared on the outermost surface. The estimated low-cycle fatigue lives after the ceramic bead peening and compound shot peening were 0.99 and 3.13 times longer than after the turning process respectively with strain amplitude 0.5% at 538℃. Moreover the gain of compound shot peening on low cycle fatigue performance gradually decreases with the increase of the strain amplitude.

Life and death at Dmanisi, Georgia: Taphonomic signals from the fossil mammals

There are many hypotheses regarding influences on the early hominin biogeographic spread into Eurasia; among them is increased meat-eating. Dmanisi in Georgia is one of the rare Early Pleistocene sites in Eurasia, and here we present primary information and analysis of the medium and large mammal taphonomy, contributing information about site formation and the hominins’ interaction with the fauna. Nearly 85% of the specimens come from the B1 stratum. Relative abundances of mammal families demonstrate some bias toward carnivores, especially Canis borjgali, and diverse Felidae species. Bones display little weathering. Post-depositional surface modifications and matrix obscure many bone surfaces, but carnivore tooth marking is the most common bone surface modification from the nutritive taphonomic phase. Tooth pits are large, in the size range of those made by modern Crocuta crocuta and Panthera leo. Breakage variables indicate most breaks occurred while the bones were still fresh, many by carnivore consumption. Fairly even limb bone representation of herbivores suggests carcasses were introduced to the site nearly whole. Hominin tool marks are present in low frequencies, but they suggest a variety of behaviors. These marks are found on Equus, Palaeotragus, Bison, large cervids, Pseudodama, Canis, and Mammuthus. Some were made by filleting proximal limb segments, and so are likely indicative of early access to carcasses, while other marks suggest scavenging. The Homo taphonomic variables resemble the rest of the taphonomic signatures from the site with little weathering, a slightly higher percentage of their bones are whole, but only a few have probable carnivore damage. The assemblage characteristics are compared to modern actualistic and experimental assemblages, and it is concluded that Dmanisi presents a palimpsest of hyena denning, felid activity, hominin meat-eating and likely natural deaths.

How to make better forensic decisions

Much of forensic practice today involves human decisions about the origins of patterned sensory evidence, such as tool marks and fingerprints discovered at a crime scene. These decisions are made by trained observers who compare the evidential pattern to an exemplar pattern produced by the suspected source of the evidence. The decision consists of a determination as to whether the two patterns are similar enough to have come from the same source. Although forensic pattern comparison disciplines have for decades played a valued role in criminal investigation and prosecution, the extremely high personal and societal costs of failure—the conviction of innocent people—has elicited calls for caution and for the development of better practices. These calls have been heard by the scientific community involved in the study of human information processing, which has begun to offer much-needed perspectives on sensory measurement, discrimination, and classification in a forensic context. Here I draw from a well-established theoretical and empirical approach in sensory science to illustrate the vulnerabilities of contemporary pattern comparison disciplines and to suggest specific strategies for improvement.

POLICING FORENSIC EVIDENCE

POLICING FORENSIC EVIDENCE

Achieving sub-nanometer roughness on aspheric optical mold by non-contact polishing using damping-clothed tool.

The surface quality of optical lenses is highly required in imaging functions. Normally, ultra-precision turning is employed to fabricate the optical lenses. However, ultra-precision turning cannot meet the surface quality demands due to the tool marks. In this study, a new damping-clothed (DC) tool and chemical enhanced non-Newtonian ultrafine (CNNU) slurry for non-contact polishing are proposed to achieve sub-nanometer roughness on aspherical optical molds. A material removal model based on the hydrodynamic pressure and velocity simulation was established to calculate the dwell time in curved surface machining. The formation mechanism of sub-nanometer roughness is clarified. The proposed method and slurry were verified by the experiments in processing NiP alloy aspheric optical mold. After the process, surface roughness Sa achieved 0.54 nm and the form accuracy is less than PV 600 nm.

Study of diffractive fringes caused by tool marks for fast axis collimators fabricated by precision glass molding.

Aspheric cylindrical lenses, including fast axis collimators (FACs), are commonly used to collimate laser beams in the fast axis direction. Precision glass molding (PGM) is applied in the production of these optical lenses due to its high accuracy and efficiency. However, the profile errors and surface topography transferred from the mold reduce the optical performance of aspheric cylindrical lenses. In this paper, the surface errors of a FAC fabricated by combining ultraprecision diamond cutting and precision glass molding are analyzed. An optical simulation model is then established to qualitatively analyze the effects of tool marks on the optical defects, and the numerical calculations are carried out to determine the relative intensity distribution of light spots. Experiments are conducted to verify the theoretical results, which prove that the tool marks cause diffractive fringes and that the geometric parameters of the tool marks that are caused by cutting conditions affect the distribution of the fringe line defects. Finally, the critical conditions to eliminate diffractive fringes and improve the optical performance of the FAC are determined based on the experimental results.

Structure and properties of friction stir welded joints made in 1565chН2 alloy sheets and plates

This paper describes the results of a study that looked at the mechanical properties of friction stir welded butt joints in 3 mm thick sheets and 15 mm thick plates made of aluminium alloy 1565chH2 (Н116). Tensile tests show that the weld tends to fracture in the heat impact zone on the tool retraction side. The tensile strength of the weld is 0.95–0.97 of the tensile strength of the base metal, which is significantly higher than the one achieved in fusion welds. The latter have the strength factor of 0.71–0.73. Together with high strength, the welded joints in 1565chH2 (Н116) alloy sheets and plates have high plasticity. When testing using a punch with the diameter equal to double thickness of the specimen, the bend angle of a sheet joint was found to be 145 degrees and that of a plate joint — 100 degrees, which is 30–68% more than in the case of the base metal. The impact strength of the weld metal is approximately 4 times higher than that of the base metal. The welded joints in 1565chH2 (Н116) alloy sheets and plates have maximum microhardness in the stir zone, whereas the heat impact zone on the tool retraction side, which is where fracture occured during the tensile tests, was found to have low microhardness. The average grain size of the weld was ~6 μm for sheets and ~8.5 μm for plates. The grain size was found to remain the same in the lap area of double-welded plate joints. The fatigue limit at the stress ratio R = –1 based on 107 cycles for welded joints in 1565chH2 (Н116) alloy sheets was 77 MPa, with the fatigue limit of the base metal being 116 MPa. Cyclic load tests showed that the fracture zone in friction stir welded joints made in 1565chH2 (Н116) alloy sheets and plates, starts from the periodic tool marks on the weld face. Fracture analysis of the specimens after the tests indicate that the welds tend to experience ductile fracture in multiple spots. The length of the heat impact zone in friction stir welded joints made in 1565chH2 (Н116) alloy sheets and plates is 3 and 10 mm, correspondingly.

Tracing the Oval—Characterisation and Construction of Original Danish Eighteenth-Century Strainers from Portraits by Jens Juel

Few examples of original strainers for paintings from the eighteenth century or earlier still exist as they have commonly been replaced due to their often-weak construction and inability to expand. Several original strainers, however, are still present in paintings by Danish portrait painter Jens Juel (1745–1802). These preserved strainers provide rare evidence of shape, construction, availability, format, and the production of strainers in the late eighteenth century. By visual analysis of twenty-two paintings, of which seven strainers are preserved, this study characterises the original strainers and their tool marks. Rare markings found on the surface hypothesised to be related to their construction is evaluated in relation to theory of polycentric ovals and layouts on the construction of oval shapes in treatises from the sixteenth to eighteenth centuries. The strainers are very similar and of simple construction with tool marks that correspond with the development in the late eighteenth century. The oval strainers are a construction with given symmetry axes, with two 60° equilateral triangles that the centres of the arcs form when aligned with the major axes. Such a layout would have been published by Christiaan Huygens (1629–1695) and Amédeé François Frézier (1682–1773) by the time of construction by someone in the wood working crafts in Copenhagen, who supplied strainers to Juel’s studio.

Manufacture and use: bone and tooth objects from the Late Bronze Age ‘shaman's grave’ at Przeczyce, Poland

The microscopic analysis of tool marks on objects from the Late Bronze Age ‘shaman's grave’ at Przeczyce, Poland, has demonstrated that two wild boar tusk pendants, a bone disc and a set of bone tubes were manufactured exclusively using metal tools. We argue that the tubes were a musical instrument that originally consisted of several separate pieces, rather than a pan flute, as has previously been suggested.

Parametric characterization of ground surfaces with laser speckles.

With well-known speckle measurement techniques, the root mean square height as well as the autocorrelation length of isotropic surfaces can be determined quickly and over a large area of interest. Beyond that, the present article studies the speckle-based measurement of anisotropic surfaces. For this purpose, a measurement setup and evaluation algorithm are presented that enable the characterization of unidirectionally anisotropic surfaces machined by grinding. As a result, four measurands are obtained from one speckle image: the machining direction, the autocorrelation length perpendicular to the machining direction, as well as two root mean square roughness parameters parallel and perpendicular to the machining direction. The first two measurands are obtained from a two-dimensional fast Fourier transform of the diffraction pattern resulting from the unidirectional tool marks and the latter two by a bidirectional evaluation of the speckle contrast. In addition to measurements on physical reference samples, a spatial light modulator is used to create a large number of surface topographies with known model parameters in order to quantify the measurement uncertainty.

Contextual bias on decision-making in forensic toxicology: First survey from China

In forensic science, contextual bias has been used to describe the tendency for a forensic analysis to be influenced by task-irrelevant background information. Contextual bias is not limited to subjective pattern matching disciplines based on visual recognition (e.g., fingerprints, handwritings, and tool marks), and has been demonstrated in objective analytical disciplines based on quantitative instruments (e.g., DNA typing). Recently, several publications suggested that contextual bias can even affect decision-makings in forensic toxicology. To obtain more extensive evidence of contextual bias, we surveyed 200 forensic toxicology practitioners from China for 1) unconscious bias in two hypothetical forensic toxicology cases with contextual information, 2) understanding of the concept and nature of contextual bias, 3) communication between investigators and forensic examiners, 4) and perception of the task-relevance of contextual information. The results revealed that 1) most of the participants made a decision deviating from standard processes under the potentially biasing context; 2) they also showed a low level of familiarity with the concept and nature of contextual bias; 3) they had a close contact with police investigators and even a dual role as a crime scene investigator and laboratory examiner, especially those affiliated with police departments; 4) and there was a general opinion that all available case information should be considered in the forensic toxicological analysis, even if the information should be specifically identified as task-irrelevant. As the first empirical work in China, this study attempted to draw more attention to the potential impact of Chinese forensic scientists’ lack of appreciation of cognitive factors in forensic practice, and promote more extensive empirical research in various forensic domains.

AN INVESTIGATION OF SURFACE ROUGHNESS ON AISI 1045 STEEL USING DEFORM 3-D AND ITS COMPARISION WITH THE EXPERIMENT

Conventional processes such as turning, and milling are often accompanied by defects such as tool marks and scratches on the final machined surface. This leads to tool wear and loss of energy which is quite undesired. This leads to poor product quality and a lowered tool life. Further, processes like honing and lapping can be used to improve the surface finish but the major drawback is the dependence on the skill of the workers involved. To overcome these issues, the burnishing operation is used for an adequate surface finish on the machined surface. The process is not only simple in operation but also chip less. In the current research work, turning operation is carried out on the ferrous material using an insert tipped tool in a CNC lathe machine. The operations are carried out at different machining parameters like speed, feed and depth of cut etc. Roughness patterns at various machining conditions are obtained and analysis was done to get the adequate machining parameters. The metal cutting process is analyzed with the FEM model for 3D simulation of the operation undertaken with a solid SPCT (single point cutting tool). This tool is modelled with CATIAV5, and exported STL files and imported in DEFORM 3D.

The Dual Space: Concept and Applications in Cultural Heritage

An important question in cultural heritage concerns the make process of an artifact. Understanding the make process provides insight related to the origin, techniques and craftsmanship used to make the artifact. Searching for tool marks or traces left by the artist's hand is one way of retrieving clues related to the make process. X-ray computed tomography (CT) is a non-destructive tool that produces volumetric images of structures inside an artifact. However, interactively searching in large volumetric images for tool marks is a difficult, tedious and time consuming task. In this article, we introduce the concept of a dual space. The governing idea is that the dual space represents the air in the interior of an object. In the context of cultural heritage, the dual space represents those materials that first belonged to the object but have been removed during the make process. Our main goal of creating the dual space is to facilitate searching, inspection and interpretation of tool marks. We provide two examples of how the dual space can be used to study the make process.

Art historical and archaeometric analyses of the ‘animal style’ gold and silver ornaments (fourth–third centuries bce) found in north‐west China

AbstractThe archaeological visibility of the production and consumption of gold and silver ornaments increased substantially during the Iron Age. A large number of precious metalworks rendered with distinctive ‘animal style’ motifs have been recovered from elite tombs in north‐west China, and have attracted great interest when investigating the dynamics of exchange, mobility and transcultural encounters in Eurasian antiquity. However, little scientific research has been undertaken to examine the manufacturing techniques and metal composition of such ‘animal style’ artefacts found in north‐west China and its neighbouring areas in a broader Eurasian context. Using multiple non‐invasive analytical methods, we conducted a detailed scientific analysis of two groups of precious metals excavated from Dongheigou Tomb 12 (fourth–second centuries bce) and Xigou Tomb 1 (third–second centuries bce) in present‐day Balikun county, Xinjiang Uygur Autonomous Region. The results suggest that mould‐pressing technology was employed for the production of the ‘animal style’ appliqués found in these two tombs. The current analysis provides a definitive explanation for the traces of superficial crafting through their specific microstructure and the tool marks of manufacturing, and will thus be of significant interest for further research concerning the metallurgic knowledge and technological practice of precious metalworking industry in north‐west China and Central Asia.

Fracture Analysis and Fatigue Strength Calculation of Anchor Bolt Used in Circulating Water Pump in Nuclear Power Plant.

A circulating water pump is a key equipment of cooling systems in nuclear power plants. Several anchor bolts were broken at the inlet rings of the same type of pumps. The bolts were turned by a special material for seawater corrosion protection. There were obvious turning tool marks at the root of the thread, which was considered as the source of the crack. The fatigue crack extended to the depth of the bolt, causing obvious radiation stripes on the fracture surface, which was a typical fatigue fracture. Obvious overtightening characteristics were found at the head of the broken bolt. Fracture and energy spectrum analysis showed that the bolt was not corroded. The axial vibration of the pump was measured. The static tensile stress along the bolt axis caused by the preload, the axial tensile stress caused by the axial vibration, and the torsional stress were calculated, respectively. According to the fatigue strength theory, the composite safety factor of the bolt fatigue strength was 1.37 when overtightening at 1.2 times the design torque, which was less than the allowable safety factor of 1.5-1.8, so the bolt was not safe, which further verified the conclusion of fracture analysis. The reason for the low safety factor was caused by the overtightening force. The improvement method was to control the bolt preload or increasing the bolt diameter.

Sole marks reveal deep-marine depositional process and environment: Implications for flow transformation and hybrid-event-bed models

ABSTRACTDeposits of sediment gravity flows in the Aberystwyth Grits Group (Silurian, west Wales, United Kingdom) display evidence that sole marks are suitable for reconstructing depositional processes and environments in deep-marine sedimentary successions. Based on drone imagery, 3D laser scanning, high-resolution sedimentary logging, and detailed descriptions of sole marks, an outcrop 1600 m long between the villages of Aberarth and Llannon was subdivided into seven lithological units, representing: a) mudstone-poor, coarse-grained and thick-bedded submarine channel fills, dominated by the deposits of erosive high-density turbidity currents with flute marks; b) mudstone-rich levee deposits with thin-bedded, fine-grained sandstones formed by low-density turbidity currents that scoured the bed to form flute marks; c) channel–lobe transition-zone deposits, dominated by thick beds, formed by weakly erosive, coarse-grained hybrid events, with pronounced mudstone-rich or sandstone-dominated debritic divisions and groove marks below basal turbiditic divisions, and with subordinate amounts of turbidites and debris-flow deposits; d) tabular, medium- to thick-bedded turbiditic sandstones with flute marks and mixed sandstone–mudstone hybrid event beds mainly with groove marks, interpreted as submarine lobe-axis (or off-axis) deposits; and e) tabular, thin- to medium-bedded, fine-grained, mainly turbiditic sandstones mostly with flute marks, formed in a lobe-fringe environment. Both lobe environments also comprised turbidites with low-amplitude bed waves and large ripples, which are interpreted to represent transient-turbulent flows. The strong relationship between flute marks and turbidites agrees with earlier predictions that turbulent shear flows are essential for the formation of flute marks. Moreover, the observation as part of this study that debris-flow deposits are exclusively associated with groove marks signifies that clay-charged, laminar flows are carriers for tools that are in continuous contact with the bed. A new process model for hybrid event beds, informed by the dominance of tool marks, in particular grooves, below the basal sand division (H1 division of Haughton et al. 2009) and by the rapid change from turbidites in the channel to hybrid event beds in the channel–lobe transition zone, is proposed. This model incorporates profound erosion of clay in the channel by the head of a high-density turbidity current and subsequent transformation of the head into a debris flow following rapid lateral flow expansion at the mouth of the channel. This debris flow forms the groove marks below the H1 division in hybrid event beds. A temporal increase in cohesivity in the body of the hybrid event is used to explain the generation of the H1, H2, and H3 divisions (sensuHaughton et al. 2009) on top of the groove surfaces, involving a combination of longitudinal segregation of bedload and vertical segregation of suspension load. This study thus demonstrates that sole marks can be an integral part of sedimentological studies at different scales, well beyond their traditional use as indicators of paleoflow direction or orientation.

Fringe analysis approach for imaging surface undulations on technical surfaces

Automated defect inspection is becoming increasingly important for advanced manufacturing. The ability to automatically inspect for critical defects early in the production cycle can reduce production costs and resources on unnecessary manufacturing steps. While there are many inspection techniques available, samples from early in a production workflow can prove challenging as they may still have systematic tooling marks, causing preferential scattering and hindering defect extraction. We propose a new imaging technique that exploits the preferential scattering from a technical surface to generate predictable fringe patterns on the sample's surface using only an array of LEDs. The patterns from this adapted fringe projection technique are imaged, and phase shifting algorithms are used to recover surface undulations on the sample. We implement this technique in the context of Hard Disk Drive platters that exhibit tooling marks from the lapping process and show that it is possible to image both highly scattering pits and scratches, as well as slow surface undulations with the same apparatus.