High Rate Deformation Research Articles

Study of the permanent deformation of three soils employed in highway subgrades in the municipality of Santa Maria-RS, Brazil

Permanent deformation is associated with wheel track rutting (WTR) and is one of the main causes of defects in the pavements of Brazilian highways. Seeking to mitigate this situation, this paper presents a study about the permanent deformation of three typical subgrade soils of the Santa Maria region, Rio Grande do Sul (RS), located in the southern region of Brazil. In addition to the physical, chemical, and mechanical characterization of the materials, this research presents results from repeated load triaxial tests to obtain the resilient modulus (RM) and the permanent deformation (PD) parameters. The Compound model of the resilient modulus, posteriorly cited on the Petrobras Asphalt Thematic Network Project, showed the best results. The permanent deformation tests were conducted using a frequency of 2 Hz and 150,000 load application cycles and posteriorly adjusted to the Guimaraes Model, of which average statistical correlation was 0.91. However, the predominance of fine materials combined with low compaction energy resulted in high deformation rates and the occurrence of shakedown in domains: A (plastic shakedown), B (plastic creep) and C (incremental collapse).

On the influence of crossing angle on long-term rail damage evolution in railway crossings

ABSTRACT The rails in railway crossings are subjected to severe load environment leading to degradation of running surface due to wear and accumulated plastic deformation. To compare long-term degradation of three fixed crossings with different crossing angles, nominally designated 1:12, 1:15, and 1:18.5, a multidisciplinary simulation methodology is applied to predict damage of the crossing rail. For a given traffic scenario, including up to 65 MGT of facing move passenger traffic in through route, the results show that damage increases with increasing crossing angle. The ratio between the maximum damage for the crossings with the largest and smallest crossing angles is found to be about three in terms of wear and about two for plastic deformation. Initially high rate of plastic deformation reduces significantly after the first 2–5 MGT, and after 10–30 MGT it approaches a nearly constant value that is significantly lower than the wear rate.

Industrial Fe-Simulation of Roughing Using an Automatic Solver Shifting Technique

Roughing has been simulated with the Finite element software AbaqusTM to replicate an industrial-scale process. The model has been made to be as close as possible to its real counterpart. For this purpose, an automated controlling logic has been created to simulate the multiple passes as well as inter-pass times for roughing. Simulating multiple passes with FEM is computationally very demanding, so new methods to reduce computing times are worth considering. During a roll pass an explicit solver is necessary due to high deformation amounts and rates. An explicit solver is tied to a very small time increment, so it takes a long time. On the other hand, inter-pass periods do not include any deformation or roller contact, so an implicit solver is quite capable of computing this portion of the simulation. An implicit solver can speed up the time increment considerably when compared to the explicit solver, so using it potentially saves a significant amount of computing time. Unfortunately, Abaqus does not include any methods to change the solver during a single simulation. Instead it is possible to communicate between the two solver types by manually importing data from a completed simulation to a new simulation model. A new method to change solvers automatically using a self-made Python code is proposed in this paper.

Multi-crack formation in soft solids during high rate cavity expansion

The parameters governing failure in ultra soft solids can be difficult to quantify since traditional characterization techniques often cannot be implemented. The effects of increasing rate further complicate efforts. However soft solids, especially biological tissues, are frequently subjected to high rate deformation leading to damage and failure and should therefore be understood. We present results from high rate, needle-mediated cavity expansions in soft silicone and ballistic gelatin samples with moduli on the order of 10 kPa. We find that increasing rate of expansion increases the number of cracks initiated in the cavity surface, leading to multi-lobed as opposed to penny-shaped cracked cavities. Comparison of these experimental observations with an elastic wave speed-dependent fracture correlation model originally developed for hard materials suggests that counting the number of cracks may provide a measure of the soft solid’s fracture energy.

Growth, survival and reproduction of the Turkish medicinal leech, Hirudo sulukii

ABSTRACT The present study aimed to investigate growth, survival and reproduction of the Turkish medicinal leech, Hirudo sulukii, endemic to Southeastern Anatolia and whose biology is poorly understood. In comparison with the Southern medicinal leech, Hirudo verbana, which has a wide distribution throughout Eurasia, H. sulukii grew faster until the fourth month, then growth increased significantly in favour of H. verbana. At the beginning of gravidity, high mortality occurred in specimens of H. sulukii not transferred to moist peat, the cocoon deposition area. Gravidity occurred in almost all (98%) H. sulukii adults, but was detected in only 60% of H. verbana adults. Unlike the growing period, survival rate was greater in H. sulukii during the reproductive period. Gravidity and cocoon laying periods lasted longer in H. sulukii, which continued reproductive activity even in colder conditions. There were more and smaller sized cocoons having higher deformation rate in H. sulukii. Likewise, fewer and larger offspring having lower morphological abnormality were observed in cocoons having lower hatchling rates in H. sulukii. Collectively, our findings reveal that H. sulukii reaches adult size relatively early, continues its reproduction in cold conditions and displays high reproductive performance, thus making it a strong candidate for leech aquaculture.

Influence of Temperature in Front Face Flow Drilling and Thread Forming of Lightweight Cast Alloys

In face flow drilling of lightweight cast materials, the heat transfer makes a significant contribution to forming ability. Especially during processing of the magnesium alloy AZ91 and the aluminum alloy AlSi10Mg, microstructural mechanisms lead to in high rates of deformation, resulting in undesirable hardening of the marginal zones. During the subsequent thread forming process, the resulting microstructure leads to an inadequate forming of the internal thread. In order to improve the geometrical and mechanical thread quality, the influences of the initial tool temperatures and the heat input induced during the forming processes are analyzed within this paper.

Impact Failure of Polycrystalline Diamond Cutters

Polycrystalline Diamond (PCD) Cutters are ultra-hard tools used for oil and gas drilling. These tools can fail in the form of spalling due to impact. In this paper, direct impact and quasi-static loading are used to investigate the failure force for leached PCD cutters when loaded at an angle on the edge of their chamfer with a PCD striker or platen. Impact experiments were performed using an impedance match system which ensures the sample is only loaded once; this allows subsequent analysis of the failure surfaces. The failure force at high deformation rate is around 8 kN and at low deformation rate 6.3−+2.3 kN. The failure force required for spalling increases with increasing deformation rate. High speed imaging is also used to explore the failure history of the cutters.

Neural cell injury pathology due to high-rate mechanical loading

Successful detection and prevention of brain injuries relies on the quantitative identification of cellular injury thresholds associated with the underlying pathology. Here, by combining a recently developed inertial microcavitation rheology technique with a 3D in vitro neural tissue model, we quantify and resolve the structural pathology and critical injury strain thresholds of neural cells occurring at high loading rates such as encountered in blast, cavitation or directed energy exposures. We find that neuronal dendritic spines characterized by MAP2 displayed the lowest physical failure strain at 7.3%, whereas microtubules and filamentous actin were able to tolerate appreciably higher strains (14%) prior to injury. Interestingly, while these critical injury thresholds were similar to previous literature values reported for moderate and lower strain rates (<100 1/s), the pathology of primary injury reported here was distinctly different by being purely physical in nature as compared to biochemical activation during apoptosis or necrosis. Statement of SignificanceMitigation and prevention of cellular injury is challenging in part due to the lack of quantitative correlation between mechanical insult and cellular pathology, especially at high deformation rates (>104 s−1) that occur in blast and directed energy related brain injury, or laser and sonic-based medical procedures. By utilizing a recently developed inertial microcavitation rheology technique for generating high-rate deformations in a 3D in vitro neural tissue model, we quantitatively correlate critical stretch, strain and stress-based injury criteria to observed cell pathology. These quantitative experimental measurements provide unprecedented new detail into the cellular pathology of neural tissues affected by high-rate injury including the first quantitative high-rate injury threshold metrics.

An Evaluation on Fracture Toughness in SUS304 at High Strain Rate Considering Process Zone

Some research works report the relationships between transformation toughening and process zone. In SUS304, the reduction of transformation toughening at high strain rate is expected from the result of a small punch test. Currently, the process zone in SUS304 is fuzzily defined. Therefore, a consideration of damaging process is necessary in order to understand a fracture mechanism associated with transformation toughening and process zone. In this study, at first, tensile tests of pre-cracked sheet specimens made of SUS304 are conducted by the split Hopkinson pressure bar in order to understand the fracture mechanism phenomenologically at high deformation rate. During the test, a DC potential difference method is introduced to capture onset time of fracture.

Investigation of the Specific Energy Absorption of Triply Periodic Minimal Surfaces Subjected to Impact Loading

Triply periodic minimal surfaces (TPMS) have attracted tremendous research interest due to their lightweight and superior mechanical properties. In this study, two TPMS sheet-based structures (FRD and Neovius) are designed, fabricated, and tested under dynamic and quasistatic loading conditions. Selective laser melting (SLM) is employed to facilitate the fabrication of such complex structures out of stainless steel (SS316L). Scanning electron microscopy (SEM) is utilized to assess the quality of the printed structures. The dynamic compressive behaviour is investigated through performing a direct impact compression test via a Direct Impact Hopkinson Bar (DIHB) at a strain rate of 2000 s-1. Quasi-static tests are also performed at a strain rate of 0.005 s-1. The specific energy absorption (SEA) is compared under both loading conditions to investigate the performance of such structures under dynamic loading. Results show that both structures exhibit higher SEA values under high deformation rates. In fact, Neovius structures outperform FRD structures in terms of specific energy absorption as it exhibits a SEA value of 22.11 J/g and 24.8 J/g SEA in quasi-static and dynamic conditions, respectively.

Mechanical response of two different molecular weight polycarbonates at varying rates and temperatures

Polymers are widely used for lightweight design in industrial applications, such as helmets and car bumpers, where the most common causes of failure or damage are dynamic impact events. It is well known that the mechanical response of most polymers is highly dependent on the loading rate and temperature, and that it is not sufficient to use properties measured under static loads in the analysis of dynamic events. However, the time-temperature equivalence phenomenon offers the chance to predict high-rate performance using low-rate data. In this study, information about the constitutive behaviour of two different molecular weight polycarbonates, is obtained in low-rate experiments and then compared with the high-rate response. A master curve of storage modulus constructed from Dynamic Mechanical Analysis data is employed to understand the viscoelastic response under small-strain loading at various frequencies and temperatures. For the large-strain constitutive response, experiments at strain rates from 0.001 s-1 to 3000 s-1 are performed using a conventional crosshead device, hydraulic device, and split-Hopkinson pressure bar. Moreover, experiments at strain rates of 0.01 s-1 and temperatures from -60 to 120 °C are also performed, and the results are compared. This approach can distinguish ’constitutive’ rate dependence from the effects of specimen self-heating due to adiabatic heating under high-rate deformation. Meanwhile, the molecular weight effects on the mechanical response at varying rates and temperatures are also noted.

The two-level elastic-viscoplastic model: analysis of the influence of crystallite orientation distribution in the reference configuration and the complexity of loading on the behavior of polycrystalline materials

Components and structural elements used in modern technology are often exposed to significant loads in wide ranges of high and low temperature and deformation rates, high stresses and loading rates.. All these factors, as well as complex loading schemes that must be considered when designing structures of different sizes - from miniature to large-scale -, put forward increased requirements for the properties of materials. A significant part of the structures used in various industries are made of polycrystalline metals and alloys. The physical and mechanical properties of polycrystalline aggregates in finished products depend on their phase and component composition, meso- and microstructure, including the orientation of crystallites (grains, subgrains), symmetry properties of subgrains, and on the initial (residual) stresses that occur during their manufacturing. Experimenting with full-scale structures requires considerable material and time expenditures, therefore mathematical modeling approaches are applied, especially for designing structures and their manufacturing processes. Mathematical modelling provides an opportunity to describe processes in any materials with this or that degree of accuracy. Constitutive relations (or constitutive models) are the most important element of the mathematical models developed for solving these problems. Currently, the most promising among these models are multilevel models based on the introduction of internal variables and crystal plasticity. When analyzing the elastic-plastic deformation of various products, the isotropic constitutive relations are often used to simplify the analysis of the elastic component of deformations. The present work is devoted to the study of errors arising when the anisotropic elastic properties of crystallites are replaced by the corresponding isotropic properties of the materials with BCC, FCC and HCP lattices for different laws of orientation distribution of crystallites in a polycrystalline aggregate in the reference configuration. Using the two-level model based on the elastic-viscoplastic crystal plasticity, a series of numerical experiments on simple shear loading, sequences of two simple loads and cyclic deformation were performed to analyze the evolution of the stress-strain state and to estimate the residual stresses in crystallites.

Multifractal Formalism in Tasks of Dynamic Plasticity

The application of the multifractal parameterization method for comparing structural changes observed in an optical microscope on steel St.3 subjected to severe plastic deformation and high-rate superplastic deformation is investigated.

Some aspects of the behavior of metastable austenitic steels at high strain rates

Metastable austenite containing steels, i.e., steels capable of undergoing solid-state phase transformation from austenite to α´-martensite during plastic deformation, offer a very good combination of ductility, strength, and above all, exceptional strain hardening capability. In effect, in suitable plastic deformation conditions the relatively soft austenitic phase can transform to the harder α´-martensite, which increases the strain hardening rate of the material through various mechanisms. This special feature gives these kinds of alloys several beneficial properties, such as resistance against flow instabilities and increased capability to absorb deformation energy. For this reason, metastable austenite containing alloys have been extensively studied in the past. However, several open questions still remain, especially in the field of high rate deformation. This can be related to the great number and complexity of the related microstructural phenomena and their combined effects on the material response. The open questions affect both the metallurgy of the material and the numerical modeling of material behavior. The current contribution addresses some of these questions and their possible solutions, as well as gives an outlook on the possible future development directions.

Pattern evolution and interactions in subaqueous dune fields: North Loup River, Nebraska, U.S.A.

ABSTRACTA time series of aerial images of a dune field on a migrating free bar in the North Loup River, Nebraska, is used to generate a quantified dataset that allows analyses of crestline deformation, dune interaction type and spatial density, and impact of spurs. Measurement of dune parameters show that the dune field maintained a dynamic steady-state pattern, despite high rates of deformation, common interactions, and sediment bypassing. Mapped crestlines had a mean migration rate of 8 cm/min. The mean deformation rate, quantified using a partial Procrustes analysis, was 2 cm/min, indicating that along individual crestlines, local migration varied ± 25% from the bedform mean. Dune interactions caused the break-apart and recombination of crestline segments, thus limiting pattern variability caused by deformation. Although most of the 50 documented interactions are comparable to those observed in aeolian dune fields, defect-driven interactions are less common and interactions caused by migration of the convex-downstream nose of the dunes were observed, which has not been reported in aeolian dunes. The spatial density of interactions is consistent with that derived for aeolian crescentic-dune fields, in spite of differences in ambient fluid and dune size. Although spurs were ubiquitous, their presence did not have a quantifiable impact on deformation and interactions as compared to areas where spurs were absent, suggesting that these short-lived features affect instantaneous flux rates only.

Allometric and ontogenetic larval development of common barbel during rearing under optimal conditions

The rearing of finfish larvae is a key element in their further culture. Improper breeding protocols may result in high mortality rates, body deformation and growth rate decreases in both the larval and fattening periods. These errors can be avoided by thorough exploration of various aspects of early larvae biology, at least in model fish species. In this study, anatomical and morphological developments were analysed using allometric growth patterns of common barbel, Barbus barbus, larvae reared under optimal controlled conditions. Larvae of common barbel, which is a model species for fish of the genus Barbus, were reared for 30 days at 25 °C in the recirculated aquaculture system (RAS). Four periods of the barbel larval development were identified: pre-flexion (0–5 days post hatching – DPH; total length – TL: 9.5 ± 0.3 to 12.3 ± 0.3 mm), flexion (6–11 DPH; TL 12.4 ± 0.3–15.4 ± 0.3 mm), post-flexion (12–21 DPH; TL 16.1 ± 0.5–21.2 ± 0.8 mm) and juvenile (from 22 DPH; TL from 21.4 ± 1.7 mm). The largest changes in barbel growth were observed during the first two periods of their life (pre-flexion and flexion), which resulted in the frequency of noted flexion points (64.3% flexion points) and was also associated with intensive morphometric growth, primarily the head and tail parts of the body. Despite a low degree of growth progress upon hatching (e.g. no eye pigment, no distinct liver or pancreas, no unobstructed alimentary tract), barbel larvae pass through the larval periods very quickly in comparison to other cyprinids and enter the juvenile period (22 days).

Microstructure evolution and peculiarities of strain hardening in aluminum processed by dynamic channel angular pressing

A study of aluminum subjected to high-rate shear deformation via dynamic channel angular pressing (DCAP) has been performed to investigate the main patterns of microstructure evolution and the peculiarities of strain hardening. A principal feature of the microstructure formed during the first DCAP pass is the occurrence of large misorientation deformation bands. Examination of their constitution and crystallography showed that at least some of them appear to be a product of deformation twinning. No indications of twinning were however found in the microstructure after 4 DCAP passes. At this stage of the processing, grain refinement occurs mainly through ordinary fragmentation, namely, a subdivision of crystallites into regions, whose misorientations gradually increase from low-angle to high-angle ones, while the role of deformation bands becomes less distinct. Nevertheless, despite considerable grain refinement, about 80% of strengthening after 4 DCAP passes is provided by the dislocation substructure, while the contribution of high-angle boundaries to the strengthening remains low.

Assessment of Thorax Finite Element Model Response for Behind Armor Blunt Trauma Impact Loading Using an Epidemiological Database.

Nonperforating ballistic impacts on thoracic armor can cause blunt injuries, known as behind-armor blunt trauma (BABT). To evaluate the potential for this injury, the back face deformation (BFD) imprinted into a clay backing is measured; however, the link between BFD and potential for injury is uncertain. Computational human body models (HBMs) have the potential to provide an improved understanding of BABT injury risk to inform armor design but require assessment with relevant loading scenarios. In this study, a methodology was developed to apply BABT loading to a computational thorax model, enhanced with refined finite element mesh and high-deformation rate mechanical properties. The model was assessed using an epidemiological BABT survivor database. BABT impact boundary conditions for 10 cases from the database were recreated using experimentally measured deformation for specific armor/projectile combinations, and applied to the thorax model using a novel prescribed displacement methodology. The computational thorax model demonstrated numerical stability under BABT impact conditions. The predicted number of rib fractures, the magnitude of pulmonary contusion, and injury rank, increased with armor BFD, back face velocity, and input energy to the thorax. In three of the 10 cases, the model overpredicted the number of rib fractures, attributed to impact location positional sensitivity and limited details from the database. The integration of an HBM with the BABT loading method predicted rib fractures and injury ranks that were in good agreement with available medical records, providing a potential tool for future armor evaluation and injury assessment.

Land Deformation Monitoring in Lanzhou City Based on SBAS-InSAR Technology

With the continuous advancement of urban construction, the original natural landscapes such as wetlands, vegetation, and soil are converted into artificial landscapes such as buildings and roads, resulting in a wide range of changes in urban surface. Monitoring urban surface changes is of great significance to the healthy development of cities and the prevention of geological disasters. The traditional land deformation monitoring technology has the disadvantages of small monitoring range, large workload and low efficiency. Interferometric Synthetic Aperture Radar technology can effectively solve the defects in the traditional deformation monitoring technology. This paper takes Lanzhou as the research area, selects the Sentinel-1A data of 25 scenes from 2014 to 2016, and uses the Small Baseline Subset Interferometric Synthetic Aperture Radar (SBAS-InSAR) for land deformation monitoring. The sedimentation observation results obtained by the SBAS-InSAR technique was analyzed with the methods of statistical analysis and time series analysis. The results show that: (1) The overall urban area of Lanzhou City has been slightly sunk, and the funnel in the deformation area is mainly concentrated in the mountainous areas, new residential buildings and subway stations. (2) From the perspective of each region, Shajingyiin Anning District, near XuanshengRundi in Jiuzhou, near Xiaodaping Driving Test Center, and near Xuanmagou-Badaoping Village in Chengguan, near Donggang Cargo Center, near Fulongping, near Hendafeicuihuating in Qilihe District, near Lanzhou West Railway Station and other places all showed strong subsidence trends, and the area with the highest deformation rate is Xiaodaping, which maximum average annual deformation velocity can reach 30.8mm/a, and the cumulative deformation is as high as 65.9mm.(3) The land deformation of Lanzhou City shows a non-linear downward trend, and the deformation gradually spreads in the east-west direction. Eventually, deformation also occurred in some foothills in the north and south, and in some urban areas. (4) The main driving factors for settlement in the urban area of Lanzhou are loess soil, rail transportation and urbanization.

The Effect of Graphene Additives on the Structure and Properties of Aluminum

Using high-resolution scanning and transmission electron microscopy methods, the morphological and size characteristics of the structural components of the composites synthesized on the basis of aluminum with a graphene microadditive in a commercial aluminum melt under a layer of molten salt are studied. An experiment on the dynamic compression of a composite by the Kolsky method was performed, the evolution of a cast structure during high-rate deformation is studied, and mechanical characteristics in the range of deformation rates έ = 1.8–4.7 × 103 s–1 were measured. The dynamic characteristics of the composite were measured under conditions of loading with planar shock waves (έ = 5 × 105 s–1) for the first time. The dynamic properties of the composite are compared as functions of the graphene content in the aluminum matrix.