High-strain Environment Research Articles

Graphene-Based Flexible Strain Sensor Based on PDMS for Strain Detection of Steel Wire Core Conveyor Belt Joints.

Because of their superior performance, flexible strain sensors are used in a wide range of applications, including medicine and health, human-computer interaction, and precision manufacturing. Flexible strain sensors outperform conventional silicon-based sensors in high-strain environments. However, most current studies report complex flexible sensor preparation processes, and research focuses on enhancing and improving one parameter or property of the sensors, ignoring the feasibility of flexible strain sensors for applications in various fields. Since the mechanical properties of flexible sensors can be well combined with rubber conveyor belts, in this work polydimethylsiloxane (PDMS) was used as a flexible substrate by a simple way of multiple drop coating. Graphene-based flexible strain sensor films that can be used for strain detection at the joints of steel cord core conveyor belts were successfully fabricated. The results of the tests show that the sensor has a high sensitivity and can achieve a fast response (response time: 43 ms). Furthermore, the sensor can still capture the conveyor belt strain after withstanding high pressure (1.2-1.4 MPa) and high temperature (150 °C) during the belt vulcanization process. This validates the feasibility of using flexible strain sensors in steel wire core conveyor belts and has some potential for detecting abnormal strains in steel wire core conveyor belt, broadening the application field of flexible sensors.

Shear's role in non-union. Measuring mean angle of long bone multi-fragmentary non-unions

IntroductionBoth mechanical and biological theories have been proposed in the development of non-union. The mechanical theory suggests that a high strain environment in a fracture will predispose it to non-union. While in simple fractures and wedge fractures there are only one and two primary fracture planes respectively, in multi-fragmentary fractures there are many and a non-union may form along any of the original fracture lines, however the plane which experiences the highest strain is at 45O – the shear plane. We hypothesise that in multi-fragmentary fractures the initial fracture line that most often fails to unite will tend towards the plane with the highest strain. Objectives1) Define the mean non-union angle in a cohort of multi-fragmentary tibial and femoral fractures.2) In wedge-like fractures within the cohort, define and compare the mean angle of initial fracture planes which go on to form a non-union to those that unite3) In comminuted fractures within the cohort, define the mean non-union angle DesignRetrospective cohort study SettingLevel-1 trauma centre MethodologyFractures were categorised into wedge-like and comminuted. A published technique was utilised to measure fracture and non-union angles. In wedge-like fractures, united and non-united initial planes were compared. In comminuted fractures only the mean non-union angle was defined. Demographic patient data was also collected. Results183 non-unions were screened, 68 patients were included. The mean non-union angle was 56°(SD 18) across all fractures. In wedge-like fractures the mean non-union angle was 59°(SD 18). In comminuted fractures the mean non-union angle was 50°(SD 19). Non-united initial fracture planes in wedge-like fractures showed a peaked distribution about a mean of 58° while united fracture planes were distributed at the extremities of the range. ConclusionsIn patients with multi-fragmentary fractures resulting in non-union, the mean tibial non-union angle was 52° while the mean femoral non-union angle was 65°. In wedge-like fractures, non-unions occurred more commonly than appropriate union in fractures between 41°-80°. The non-union angle is closer to 45° in comminuted fractures than in wedge-like fractures. These results support the mechanical theory that strain from the shear plane is an important factor in the formation of non-unions. Level of EvidencePrognostic level 3.

An island-bridge packaging piezoelectric sensor for structural health monitoring in high-strain environments

Piezoelectric sensor failure triggered by high structural strain is a critical problem in structural health monitoring (SHM) that cannot be neglected. Thus, a novel island-bridge packaging piezoelectric sensor for SHM in high-strain environments is proposed in this paper. The trapezoidal-section island-bridge structure of the new sensor greatly optimizes the high-strain survivability of the piezoelectric layer. Additionally, good impedance matching characteristics between the monitored structure and the sensor guarantee the transmission strength of high-frequency dynamic sensing signals. The feasibility of the structure and the principle of operation for the novel sensor were demonstrated via theory, simulation and experiment. Besides, an established analytical model and its simulation and experimental verification results displayed that the structural parameters of the sensor could significantly adjust the strain-bearing capacity. Under a specific parameter configuration, the strain transfer coefficient of the novel sensor was only 0.087, which was 12.1% of the conventional sensor, thus could safely operate in the monitoring structure environment of 10,000 με. On the other hand, the proposed sensor’s impedance signal strength was satisfactory in the SHM frequency range of 10–110 kHz, where its average impedance value was as high as 397.7 Ω. Moreover, the optimized signal demonstrated very good stability, reliability, and strength in the test, thus ensuring the effective monitoring of crack propagation via the new sensor. Therefore, this work is a good complement to the existing piezoelectric sensors SHM technique.

Toluene addition to turbulent H2/natural gas flames in bluff-body burners

A key challenge in the transition towards using hydrogen as an alternative carbon-free fuel is the reduced thermal radiation due to the absence of soot. A novel solution to this may be doping with highly sooting bio-oils. This study investigates the efficacy of toluene as a prevapourised dopant in turbulent pure hydrogen and blended hydrogen/natural gas flames as a means of improving soot loading and radiant heat transfer. All flames are stabilised on bluff-body burners to emulate the recirculation component of many industrial combustors. Total heat flux and illuminance increase non-linearly with toluene concentration for fuel blends and bluff-body diameters. By reducing the bluff-body diameter from 64 mm to 50 mm, a 20/80 (vol%) H2/natural gas mixture produces a more radiative flame than a 10/90H2/natural gas mixture in the smaller bluff-body. Opposed-flow flame simulations of soot precursors indicate that as strain rate increases, although overall soot precursor concentration decreases, a 20 vol% hydrogen mixture will produce more soot than a 10 vol% mixture. This suggests the addition of hydrogen up to 20 vol% may be beneficial for soot production in high strain environments.

Power amplification via compliant layer interdigitation and dielectrophoretic structuring of PZT particle composites

The evolution of portable electronics has led to recent popularity of piezoelectric materials for energy harvesting, especially for devices deployed remotely or in vivo. The efficiency of piezoelectric generators harvesting energy from the human body is lacking due to off-resonance loading. Piezoelectric ceramics are expensive to manufacture and are dense, brittle, and difficult to use in high strain environments. Piezoelectric composites composed of ferroelectric particles distributed in a polymer matrix are desirable due to low cost and tunable properties. In this study, Compliant Layer Adaptive Composite Stacks (CLACS) made with thin piezoelectric composite layers structured by dielectrophoresis (DEP) were investigated to increase the energy harvesting efficiency at low frequency loading. To predict power generation capabilities, a theoretical model was developed by using established particle composite models in conjunction with a shear lag structural mechanics model for CLACS. Granular composite discs of lead zirconate titanate particles in an epoxy matrix were manufactured at a 50% volume fraction and structured by DEP, if applicable. CLACS were manufactured using composite discs and two compliant layer thicknesses. The stacks were electromechanically tested by varying load, frequency, and resistance. Experimental results showed a significant increase in power amplification with DEP structured discs and compliant layer interdigitation. In addition, the theoretical model accurately predicts power production for both 0–3 and 1–3 CLACS at low frequencies. DEP structured particle composite CLACS can provide a method of energy harvesting for devices in remote locations, especially in low frequency high strain environments.

The JDCS Model and Blue-Collar Bullying: Decent Working Conditions for a Healthy Environment.

Violence in the workplace and its health consequences still represent one of the main obstacles to obtaining decent working conditions. In particular, blue-collar workers run a greater risk of experiencing episodes of violence, also because of a lack of autonomy and fewer social interactions. According to the work environment hypothesis, factors such as high workload, lack of social support and lack of job control represent the antecedents of workplace bullying. Following the job demand-control-support model (JDCS), violence can be the symptom of a high-strain environment. Moreover, it is still unclear if workplace bullying can mediate the effects of work-related stress on workers’ health outcomes. The aim of the present study is to analyse the relationship between the components of the JDCS and the health of the workers considering workplace bullying as a mediating variable. By a cross sectional study design, we tested the following theoretical hypotheses: first, JDCS components (conceptualized as stress) are supposed to significantly predict the level of workers’ health. Second, workplace bullying is supposed to mediate the relationship between the JDCS components and the level of health. The sample consists of 400 blue-collars from three different Italian companies. Work-related stress, health outcomes and workplace bullying were measured by specific self-administered questionnaires and the relationships between the variables of interest were tested through a structural equation model (SEM) analysis. The results showed that while the direct relationship between the components of the JDCS and the level of psychological health is weaker (standardized path coefficients SPC = 0.21), the partial mediation hypothesis shows that workplace bullying mediate the relationship between JDCS components and health outcomes (χ2/df ratio = 2.70; path from stress to workplace bullying SPC = 0.78; path from workplace bullying to general health SPC = 0.51; p = 0.01). The JDCS components (workload, lack of control, lack of support) are useful predictors for workplace bullying. On the other hand, bullying plays a mediating role between the stress experienced and the health consequences. The present study adds new insights into the relationship between violence seen as a form of social behavioural strain and the psychological health of workers. The theoretical and practical implications are discussed. Future research on blue-collars could use longitudinal designs in order to analyse the relationship between social environment, job design and strain reactions.

Diamonds from Dachine, French Guiana: A unique record of early Proterozoic subduction

Diamonds from Dachine, French Guiana, are unique among worldwide diamond populations. The diamonds were transported to the surface in an unusual ultramafic extrusive magma with an affinity to boninite or komatiite, which was emplaced within an arc geological setting at ~2.2Ga. Dachine diamonds have internal and external morphologies indicative of relatively rapid growth from carbon oversaturated fluids or melts, and exhibit internal features consistent with residence in a high-strain environment. On the basis of nitrogen (N) defects the diamonds are categorized as Type Ib–IaA. The unusually low aggregation state of N places severe constraints on the thermal history of the diamonds, effectively ruling out derivation in convecting mantle. The carbon and N isotopic compositions of Dachine diamonds are consistent with a sedimentary source of carbon, with the majority of diamonds having δ13C values <−25‰ and δ15N values >+4‰. The primary carbon was presumably deposited on an early Proterozoic seafloor. Sulphide inclusions have low Ni and Cr and are comparable to lithospheric eclogitic-type sulphide inclusions. Three garnet and one clinopyroxene inclusion are also eclogitic in composition, and one garnet inclusion has a majorite component indicating an origin around 250km depth. The silicate inclusions are highly depleted in many incompatible trace elements (e.g. LREE, Nb, Hf, Zr), and modelling indicates an eclogitic source lithology that contained a LREE-enriched trace phase such as epidote or allanite, and an HFSE-rich phase such as rutile. Four of the five inclusions are unusually enriched in Mn, as well as Ni and Co, and modelling suggests a protolith with a bulk composition of subducted normal MORB plus about 10% ferromanganese crust component. We suggest a model wherein Dachine diamonds precipitated from remobilized sedimentary carbon at the slab–mantle interface from liquids derived ultimately by deserpentinization of slab peridotite at depths of ~200 to 250km. These fluids may also trigger melting in wedge peridotite, resulting in a volatile-rich ultramafic melt that transports the diamonds rapidly to the surface. The process of diamond formation and exhumation from the slab–mantle interface occurred in a Paleoproterozoic subduction zone and over a very limited timespan, likely less than a million years.

Bone remodeling is reduced in high stress regions of the cercopithecoid mandible

Independent lines of evidence suggest that osteonal bone remodeling is a function of both mechanical (i.e., changes in stress) and non-mechanical (i.e., metabolic needs related to calcium liberation) factors. The degree to which secondary bone reflects mechanical factors, however, is incompletely understood despite the common assumption that the stress environment mediates remodeling activity. Here, we investigate whether there are remodeling differences between regions of primate mandibular bone known to have distinct stress environments. Osteon density, osteon fragment density, and relative osteonal area are measured as indicators of remodeling activity from postcanine and symphyseal thin sections of four sympatric monkey species (N = 20 total) from Taï Forest, Côte d'Ivoire: Piliocolobus badius, Colobus polykomos, Cercocebus atys, Cercopithecus diana. Subfamily and regional effects were assessed by two-way ANOVA. Symphyseal bone has lower osteonal density, fragment density and relative osteonal area than postcanine bone in all species, indicating relatively low remodeling activity in symphyseal bone, despite the likelihood of relatively high stresses in its lingual cortex. Subfamily differences in postcanine remodeling are significant in that colobines exhibit greater remodeling than cercopithecines. The data suggest that high strains are not requisite for bone remodeling. How the lingual symphysis negotiates a high strain environment without the reparative benefit of remodeling is yet to be elucidated, but the data prompt reevaluation of the relationship of targeted remodeling to stress histories. Differences in osteonal bone density between taxa might reflect feeding or dietary influences on remodeling activity, but sample composition prevents parsing behavioral from other taxon-specific effects.

Robust piezoelectric composites for energy harvesting in high-strain environments

High-strain environments, such as are found in automobile tires, provide deformation energy that can be harvested using piezoelectric materials, for instance, for powering electronics such as wireless sensors. Despite numerous efforts, none of the present devices easily satisfy the stringent operating and lifetime requirements for use inside a car tire, such as mechanical (accelerations of up to 3000 m/s2) and thermal requirements (temperatures of −40°C to 120°C), often leading to complex and costly solutions. Polymer–piezoelectric ceramic composite properties can be designed to fulfill the operating requirements. Furthermore, these materials are suitable for low-cost mass production and easy integration in the tire itself. Composite materials with increased output can be manufactured using the dielectrophoretic processing technique, which causes the alignment of the piezoelectric particles inside the polymer matrix, to obtain materials with adequate flexibility combined with a high energy density. In this study, we present the design, synthesis, and integration of novel composite material foils in automobile tires. The advantage of these dielectrophoretically structured composite materials is demonstrated and their output is compared to conventional piezoelectric composites. Furthermore, the charge signal output of a number of foil-based prototypes tested using an automobile tire test rig is evaluated and discussed with respect to energy harvesting performance.

Decoding near-concordant U–Pb zircon ages spanning several hundred million years: recrystallisation, metamictisation or diffusion?

In situ isotopic (U–Pb, Lu–Hf) and trace element analyses of zircon populations in six samples of the intrusive Mawson Charnockite, east Antarctica, emphasise complex zircon behaviour during very high-grade metamorphism. The combination of geochemical data sets is used to distinguish xenocrysts and identify a population of primary igneous zircon in situations where U–Pb data spread close to concordia over a few hundred Myr. The population is filtered to exclude grains with: (1) U–Pb ages >2% discordant, (2) anomalous trace element-content (Th, U, Y, REE) and (3) outlying Hf-isotopic values. Rare metamorphic-type grains were also excluded. Upon filtering the population, minimum emplacement ages for each sample were determined using the oldest grain(s). This approach improves upon age determinations in complex data sets that use weighted mean or isochron methods. Our results suggest that the Mawson Charnockite was emplaced episodically at c. 1145–1140 Ma, c. 1080–1050 Ma and c. 985–960 Ma. Core-outer core-rim and core-rim textures were identified but are not correlated with U–Pb ages. We establish that recrystallisation (mainly of zircon rims) must have occurred shortly following igneous crystallisation and that metamictisation/cracking is a Paleozoic to Recent event. Therefore, intra-zircon diffusion in a high-T, high-strain environment during Meso-Neoproterozoic orogenesis is inferred to have caused the extensive U–Pb isotopic disturbance. Charnockitic magmatism prior to c. 1,000 Ma has not previously been recorded in the Mawson region and indicates that orogenesis may have commenced c. 150 Myr earlier than previously thought. Correlations with similar aged rocks in adjacent regions have implications for supercontinent reconstructions.

Explosion-mediated fracture patterns relate to environment: a forensic biomechanical approach

Introduction Civilian fractures have been extensively studied with in an attempt to develop classification systems, which guide optimal fracture management, predict outcome or facilitate communication. More recently, biomechanical analyses have been applied in order to suggest mechanism of injury after the traumatic insult, and predict injuries as a result of a mechanism of injury, with particular application to the field so forensics. However, little work has been carried out on military fractures, and the application of civilian fracture classification systems are fraught with error. Explosive injuries have been sub-divided into primary, secondary and tertiary effects. The aim of this study was to 1. determine which effects of the explosion are responsible for combat casualty extremity bone injury in 2 distinct environments; a) in the open and b) enclosed space (either in vehicle or in cover) 2. determine whether patterns of combat casualty bone injury differed between environments Invariably, this has implications for injury classification and the development of appropriate mitigation strategies. Method All ED records, case notes, and radiographs of patients admitted to the British military hospital in Afghanistan were reviewed over a 6 month period Apr 08-Sept 08 to identify any fracture caused by an explosive mechanism. Paediatric cases were excluded from the analysis. All radiographs were independently reviewed by a Radiologist, a team of Military Orthopaedic Surgeons and a team of academic Biomechanists, in order to determine the fracture classification and predict the mechanism of injury. Early in the study it became clear that due to the complexity of some of the injuries it was inappropriate to consider bones separately and the term ‘Zone of Insult’ (ZoI) was developed to identify separate areas of injury. Results 62 combat casualties with 115 ZoIs (mean 1.82 zones) were identified in this study. 34 casualties in the open sustained 56 ZoIs (mean 1.65); 28 casualties in the enclosed group sustained 59 ZoIs (mean 2.10). There was no statistical difference in the mean ZoIs per casualty in the open vs enclosed group (Student t-test, p=0.24). Open fractures were more prevalent in the open group compared to the enclosed group (48/59 vs 20/49, Chi-squared test p Conclusions This data clearly demonstrates two distinct injury groups based upon the casualties9 environment. The enclosed environment afforded by buildings and vehicles appears to mitigate the primary and secondary effects of the explosion. However, tertiary blast effects were the predominant mechanism of injury, with severe axial loading to the lower extremity being a characteristic of the fractures seen. In contrast, secondary fragments from the explosion were more likely to result in fractures of casualties caught in the open. The development of future mitigation strategies must be focused on reducing all the different mechanisms of injury caused by an explosion. This will require a better understanding on the effects of bone in high strain environments. This method of forensic biomechanics involving clinicians and engineers, combined with accurate physical and numerical simulations can form the basis in reducing the injury burden to the combat soldier.

Biomechanical Comparison of Four Soft Tissue Replacement Materials: An In Vitro Evaluation of Single and Multilaminate Porcine Small Intestinal Submucosa, Canine Fascia Lata, and Polypropylene Mesh

To compare mechanical performance of 4 soft tissue replacement materials. Experimental. Polypropylene mesh (PM), single-layer porcine small intestinal submucosa (SIS), multilaminate (4-layer) porcine small intestinal submucosa (MLSIS), and canine fascia lata (FL). The mechanical properties of each material were determined by testing to failure on a materials testing machine. Samples of each material (n=10) were tested in 3 different modes: resistance to suture pullout, tensile testing, and push-through testing. PM was tested both parallel (PMa) to and perpendicular (PMb) to its longitudinal cord orientation. SIS and FL were similarly tested in 2 orthogonal directions. With some exceptions, the following generalizations can be made regarding the mechanical performance of the materials tested: Suture pullout-FL>PMa=PMb>MLSIS>SIS (P< or =.04). Tensile testing-FL>PMa>PMb>MLSIS>SIS (P< or =.02). Push-through testing-FL>PM>MLSIS>SIS (P< or =.003). PM accommodated a significantly higher load and energy to yield when its longitudinal cords were oriented parallel with the tension axis (PMa). FL performed similarly to the PM, with the exception of limited elongation in tension. MLSIS had biomechanical characteristics that were inferior to FL and PM but superior to SIS. PM's orientation may need to be considered when used clinically. FL is a biomechanically suitable soft tissue replacement material but its use may be limited by currently available sizes. SIS cannot be recommended in high-strain environments.

Length-tension relationship of the feline thyroarytenoid muscle

Vocal fold tension during phonation is generated by coordinated contraction of the intrinsic laryngeal muscles. The thyroarytenoid muscle has been found to have increased stiffness at various levels of strain when compared with other intrinsic laryngeal muscles. The objective here is to test the hypothesis that the thyroarytenoid muscle exhibits high passive tension during maximal isometric tetanic force generation, and to test the hypothesis that the thyroarytenoid maintains the ability to generate contractile force at high levels of strain more effectively than other skeletal muscle. The thyroarytenoid muscles (n = 9) and digastric muscle strips (n = 7) were removed from adult random-bred cats. Maximal isometric tension and passive tension at optimum length were measured from each muscle in vitro. Active and passive length-tension curves were constructed for each muscle. The contractile properties of the thyroarytenoid group were compared with those of the digastric muscle group. The thyroarytenoid muscle group required on average 140 mN of passive tension to generate maximal isometric tetanic tension. This represented 39% of the average maximal isometric tetanic tension generated by the muscles. These results were significantly higher than the digastric muscle group, which required on average 28 mN of passive tension (9% of maximal isometric tetanic tension, p<0.05). At 110% of optimum length, the thyroarytenoid muscle maintained 89.8% of maximal isometric tetanic force, whereas the digastric muscle group maintained 67.7% of maximal isometric tetanic force ( p<0.05). The thyroarytenoid muscle exhibits higher passive tension when generating maximal isometric tension than the digastric muscle control group. The thyroarytenoid muscle maintains higher levels of active tension at high strain than the digastric muscle control group. We conclude that these findings are related to the ability of the thyroarytenoid muscle to function as a fine tensor of the vocal fold in a high strain environment.

The Crixas gold deposit, Brazil; thrust-related, postpeak metamorphic gold mineralization of possible Brasilino Cycle age

The Crixas gold deposit is located in central Goias State, approximately 400 km northwest of the capital Brasilia. It is owned in joint venture by INCO Gold Ltd. and Anglo American Ltd. The indicated reserves are 7 million metric tons with a grade of 10 to 12 g/metric ton. The discovery was made in the late 1970s with mining commencing in the fall of 1988.The hosting Crixas greenstone belt is underlain by a typical Archcan metamorphosed volcanic-sedimentary sequence and is surrounded by granite-granite gneiss terrane. The Crixas gold deposit is located at the contact of the metavolcanic and metasedimentary sequences. Gold ore occurs within an upper and lower ore zone. The upper ore zone consists of an outer shell of ferroan dolomite-chlorite-biotite schist, an inner shell of sericite-chlorite schist, and magnetite-chlorite schist which in turn surrounds a core of massive arsenopyrite-pyrrhotite-chalcopyrite. The lower ore zone consists of a quartz-cemented graphitic pelite breccia.The upper and lower ore zones are interpreted to represent metasomatically altered parent lithologies. Metasomatism postdates a maximum regional metamorphism of epidote-amphibolite facies or biotite-garnet grade. Carbonatization, sericitization (base leaching), silicification, and sulfidization are indicated to have operated during the development of the ore deposit. Gold deposition is believed to have occurred as the result of reduction of f (sub S 2 ) through the formation of Fe-rich carbonate, silicate, and sulfide phases.The style of deformation within the deposit is typical of a high-strain environment. Regional structural data provide strong evidence that the high strain is related to low-angle thrusting. The age of the thrusting or the time of mineralization is not known; however, low-angle thrusting is related to a Brasiliano cycle event (550-450 Ma).