Residual Plastic Research Articles

Optometric Management of a Post-Concussion Patient: A Case Report

Over the past decade, there has been increased emphasis on the diagnosis and treatment of concussion, especially in the military and in sports. In this case report, the optometric management of a post-concussion, young-adult is described. He was diagnosed with low myopic astigmatism, convergence insufficiency, fusional instability, oculomotor dysfunction, and photosensitivity. Treatment included tinted spectacle correction for fulltime wear and conventional oculomotor-based vision therapy. At the cessation of the vision therapy, as well as three years later, he was effectively asymptomatic with normal clinical findings. These results demonstrate the efficacy of a comprehensive optometric approach in concussion, with evidence suggestive of considerable residual visual system plasticity.

Policy considerations for limiting unintended residual plastic in agricultural soils

Growing crops under high-intensity agriculture entails the use of numerous plastic products, especially polyethylene plastic films used as crop mulches. As a result, some of the world’s most productive agricultural soils are now being affected by plastic pollution, seriously threatening soil health and food security. Plastic film mulches designed to biodegrade in soil provide an appealing alternative to polyethylene films. What may be surprising, however, is that biodegradable plastic films do not necessarily represent a long-term solution to the problem of contaminating soil with plastic residues. Transformative science and policies are needed to mitigate uncertainty of biodegradable plastic residue accumulation in agricultural soils.

The Influence of Forming Effects on The Bending Crush Behavior of Top-Hat Thin–Walled Beams

This paper presents a study on the effects of forming process of a top–hat thin–walled beams to its bending crush resistance under dynamic bending load. The thin–walled beam was formed using a one step deep drawing. HyperForm software simulated the forming process and mapped its effects such as thickness variations and residual plastic strains in to the crash analysis models. Then the dynamic bending crush analysis was carried out using LS–DYNA by using the geometry and materials data obtained from the forming analysis results. For each material model, the analyses were carried out for model with and without the forming effects. The bending crush behavior of the top–hat thin–walled beams were then analyzed to compare between the simulations with and without forming effects. The results show that by incorporating the effect of forming process, the bending crush resistance of the thin–walled beams is increase by 4.7%. The introduction of strain rates to the material model increases even further on the bending crush resistance of the thin–walled beam.

Residual plastic mulch fragments effects on soil physical properties and water flow behavior in the Minqin Oasis, northwestern China

The covering of complete plastic films on soil would affect physical and biochemical properties of the soil microenvironment. Residual plastic film fragments (RPFF), which is left behind after retrieving the most of plastic films, could affect the flow behavior in the arable layer. This study was designed to assess the potential effects of RPFF on soil physical properties, water infiltration and distribution in the soil. Treatments with and without residual plastic film fragments (RPFF and NRPFF, respectively) were performed. A dye tracer was introduced to track the water movement, and the physical properties of the soil and the dynamic behavior of water transport in the soil column of the arable layer (0–20cm) were determined. The initial gravimetric water content, bulk density, total porosity in 0–20cm was significantly different between RPFF and NRPFF treatment. The dark blue area in maize root and densely rooted zones under RPFF decreased by 99% and 4%, respectively, relative to that under NRPFF. The sharply changing state of infiltration and outflow indicated that water flowed along a preferential path, e.g., macro-pores in NRPFF and residual plastic film pieces in RPFF. After clearing the RPFF, the time of equilibrium in 0–5, 5–10, 10–15, and 15–20cm soil columns decreased by 48%, 50%, 49%, and 45%, respectively. Our results highlighted that the presence of RPFF significantly influenced soil physical properties, altered soil water distribution, and decreased the matching degree of the flow distribution region and the maize root (densely rooted) zone. The present study demonstrated that the importance of clearing the RPFF for irrigation water management in agriculture produces.

The status and distribution characteristics of residual mulching film in Xinjiang, China

Pollution of residual plastic film in arable lands is a severe problem in China. In this study, the status of residual film and influential factors were investigated using the methods of farm survey in combination with questionnaires and quadrat sampling at a large number of field sites in Xinjiang Uygur Autonomous Region, China. The results showed that the amount of film utilization increased largely and reached to 1.8×105 t in 2013. Similarly, the mulching area also substantially increased in recent decades, and reached to 2.7×105 ha in the same year. According to the current survey, 60.7% of the sites presented a greater mulch residue than the national film residue standard (75 kg ha−1), and the maximum residual amount reached 502.2 kg ha−1 in Turpan, Xinjiang. The film thickness, the mulching time and the crop type all influenced mulch residue. The thickness of the film had significantly negative correlation with the amount of residual film (P<0.05), while the mulching years had significantly positive correlation with it (P<0.05). The total amount of residual film in Xinjiang was 3.43×105 t in 2011, which accounted for 15.3% of the cumulative dosage of mulching. Among all the crops, the cotton fields had the largest residual amount of mulch film (158.4 kg ha−1), and also the largest contribution (2.6×105 tons) to the total amount of residual film in Xinjiang.

Modeling plasticity by non-continuous deformation

Plasticity and failure theories are still subjects of intense research. Engineering constitutive models on the macroscale which are based on micro characteristics are very much in need. This study is motivated by the observation that continuum assumptions in plasticity in which neighbour material elements are inseparable at all-time are physically impossible, since local detachments, slips and neighbour switching must operate, i.e. non-continuous deformation. Material microstructure is modelled herein by a set of point elements (particles) interacting with their neighbours. Each particle can detach from and/or attach with its neighbours during deformation. Simulations on two- dimensional configurations subjected to uniaxial compression cycle are conducted. Stochastic heterogeneity is controlled by a single “disorder” parameter. It was found that (a) macro response resembles typical elasto–plastic behaviour; (b) plastic energy is proportional to the number of detachments; (c) residual plastic strain is proportional to the number of attachments, and (d) volume is preserved, which is consistent with macro plastic deformation. Rigid body displacements of local groups of elements are also observed. Higher disorder decreases the macro elastic moduli and increases plastic energy. Evolution of anisotropic effects is obtained with no additional parameters.

Proof stress measurement of die-cast magnesium alloys

Magnesium and its alloys exhibit not only elastic and plastic behaviour but also anelastic behaviour upon loading. The presence of anelastic strain poses a challenge to the measurement of proof stress using conventional methods. As such, the proof stress measurement methods specified by American Society for Testing and Materials (ASTM) and International Standards Organization (ISO) are reviewed and applied to three common die-cast magnesium alloys including AE44, AM60 and AZ91. The methods in the standards give inconsistent results due largely to the inherent anelastic behaviour of these alloys. The widely used 0.2% offset strain method tends to underestimate proof stress while the 0.2% permanent plastic strain method requires repeated loading and unloading. In view of the fact that the non-equivalence between the offset strain and the residual plastic strain for magnesium alloys is a key obstacle to the accurate proof stress measurement, a conversion chart is constructed to enable the determination of the appropriate offset strain for a desired residual plastic strain for a range of magnesium alloys. It is also shown that employing a higher offset strain than 0.2% has an advantage in reproducibility of proof stress measurement.

Pharmacogenetic reactivation of the original engram evokes an extinguished fear memory

Fear memory extinction has several characteristic behavioral features, such as spontaneous recovery, renewal, and reinstatement, suggesting that extinction training does not erase the original association between the conditioned stimulus (CS) and the unconditioned stimulus (US). However, it is unclear whether reactivation of the original physical record of memory (i.e., memory trace) is sufficient to produce conditioned fear response after extinction. Here, we performed pharmacogenetic neuronal activation using transgenic mice expressing hM3Dq DREADD (designer receptor exclusively activated by designer drug) under the control of the activity-dependent c-fos gene promoter. Neuronal ensembles activated during fear-conditioned learning were tagged with hM3Dq and subsequently reactivated after extinction training. The mice exhibited significant freezing, even when the fear memory was no longer triggered by external CS, indicating that the artificial reactivation of a specific neuronal ensemble was sufficient to evoke the extinguished fear response. This freezing was not observed in non-fear-conditioned mice expressing hM3dq in the same brain areas. These results directly demonstrated that at least part of the original fear memory trace remains after extinction, and such residual plasticity might reflect the persistent memory.

Molecular Dynamics Study of Superelastic Performance of a β-Si3N4 Nanohelical Coil.

Superealsticity behavior has been discovered for the β-Si3N4 nanohelical coil. By a series of cyclic loading and unloading simulation tests, the nanohelical coil could elastically recover its original shape after a relatively long axial tension far beyond the elastic limit, accompanying little residual plastic deformation. The spring constant is first a steady-state value of 0.72 N m-1 in the linear stage and then increases dramatically for up to 1.5 N m-1 in the nonlinear region. The fascinating performance of the nanocoil makes it stand out from its bulk counterparts in the development of future electronic devices such as nanoscale elastic energy storage.

Finite Element Analysis of Particle Impact on Substrates Using HVOF Thermal Spray Coating

Lower flame temperature characteristics of high velocity oxygen fuel (HVOF) flame spray process favor several surface coating applications. Simulation of HVOF coating is extremely complex to analyze, since its properties and microstructure depend on numerous processing parameters. Finite element analysis (FEA) is used in this paper to analyze the influence of particle heat input and impact velocity on HVOF coating on various substrates. HVOF thermal spray coating conditions, Tungsten Carbide Cobalt (WC-Co) particles and steel substrate were modeled using ANSYS 14.5. Droplets of different size were considered as particles in the numerical analysis to study their impact on the substrate. Thermal and residual stress analysis was done on both the particle and substrate during different stages of the high velocity impact process. Both rigid and soft conditions of the particle and substrate were simulated. Thermal stress of both the particle and substrate were found to increase rapidly very close to the impact process. Smaller sized particles had higher plastic strain when compared to larger sized particles. However, the residual stress and plastic strain of the substrate increased when impacted by larger sized particles. Residual stress of both particle and substrate were found to be influenced by the impact and thermal stress of each other. Higher velocity of the flame spray showed improved plastic strain and stress on individual particles, which is a major reason for the dense pattern of coating.

Effect of planting date and plant density on cotton traits as relating to mechanical harvesting in the Yellow River valley region of China

Previous studies have indicated that mechanical cotton harvesting requires a compact plant habit without fiber yield and quality reduction. The objective of this study was to determine the effects of planting date and plant density on plant habit, yield, early maturity, and fiber quality of cotton in the Yellow River valley region of China, and thus to identify the appropriate planting date and plant density suitable for its mechanical harvesting. Field experiments were conducted in 2013 and 2014 in Hejian, Hebei Province, using a split-plot design with planting date as the main plot and plant density as the subplot. The results indicated that moderately late planting in late April or early May (P2) was appropriate for mechanical harvesting of cotton as relative to P1 (local traditional planting date, 10 d earlier than P2) and P3 (10 d later than P2). P2 showed a 2.4–5.7cm greater height to the first fruiting branch (from the bottom) and a 4.7–11.3cm higher lowest boll (harvestable boll nearest to the ground) compared with P1, which is helpful for decreasing yield loss and reducing intake of residual plastic mulch. In addition, P2 produced slightly greater yield than P1 and P3, and the percentage of open bolls in late September for P2 was similar to that of P1 and greater than for P3, suggesting a low risk of late maturity. For plant density, 8.9plantsm−2 (D2) was appropriate for mechanical harvesting compared with 6.6 plants m−2 (D1), the local traditional density for manual harvesting, and 12.3plantsm−2 (D3). D2 showed a 2.5cm greater height to the first fruiting branch and a 4.2cm higher lowest boll, and exhibited 2.9–3.6 and 2.6–3.9cm shorter lengths of lower and middle fruiting branches than D1, respectively. This type of compact plant habit is conducive to efficient mechanical harvesting. Moreover, D2 produced a similar yield to D1 for both the rainy 2013 and the dry 2014, indicating yield stability. Although D3 had a more suitable plant habit for mechanical cotton harvesting, its yield level and maturity varied across years. There were no significant interactions between planting date and plant density in the majority of tested traits. The results will contribute to the development of integrated cotton management for upcoming mechanical harvesting in the Yellow River valley region of China.

Experiments on electrohydraulic forming and electromagnetic forming of aluminum tube

Electromagnetic forming (EMF) and electrohydraulic forming (EHF) are typical high speed forming technologies characterized with improved formability of sheet metal, single-sided die, and high precision deformation of parts. In this work, the bulging experiments of aluminum alloy tubes by EMF and EHF were performed to investigate the attaching-die capability, wall thickness, working hardness, and residual plasticity of deformed tubes. The results showed that the bulged tube by EMF is of low attaching-die capability, remarkable rebound, serious thinning of wall thickness, and prone to rupture in the outer corner. However, the parts by EHF process are of high attaching-die capability, almost no rebound, relatively uniform thickness, and remarkable fillet filling in the inner corner. The load mechanism contributes to the different deformation results of both processes. With the almost equivalent deformation, the tensile deformation ability of EHF part is better than that of EMF one, and the discharge energy efficiency of the former is higher than that of the latter.

Residual Stress Distribution in a Dissimilar Weld Joint by Experimental and Simulation Study

Dissimilar welding between carbon steel and stainless steel is widely used in power plant. A lot of stress corrosion cracking (SCC) have occurred in the weld joint, which are affected greatly by residual stresses. This paper presents a study of residual stress in a dissimilar weld between 0Cr18Ni9 steel and 20 low carbon steel with Inconel 182 weld metal, by using neutron diffraction, X-ray diffraction measurement and finite-element method (FEM). The residual stresses show asymmetric distribution due to the dissimilar materials. The maximum longitudinal (1.92ReL304) and transverse stresses (1.07ReL304) are presented in the weld metal and heat effected zone of 20 carbon steel, respectively. Through the thickness of weld metal, the average longitudinal stress is around 370 MPa. The weld root has a stress concentration, and the stresses near the weld root in the 20 steel are larger than those in 0Cr18Ni9 steel, making the weld root become the most risk zone for SCC. With the increase of heat input, the residual stress and plastic deformation around the weld root increase. Hence, low heat input is recommended for the welding between 0Cr18Ni9 steel and 20 carbon steel.

Laser welding of NiTi shape memory alloy wires and tubes for multi-functional design applications

Welding and joining of NiTi shape memory alloys is essential for their integration into an increasing variety of applications. Almost all manufacturers and a significant number of researchers focus their investigation on welding NiTi, which can present both pseudoelasticity (PE) and shape memory effect. Integration of these materials would provide increased flexibility in terms of smart design, in particular for multi-functional systems. The current work investigates the mechanical, physical and phase transformation properties of similar (base materials (BMs) with the same composition) and dissimilar (BMs with different compositions) NiTi welded shape memory wires. The similar and dissimilar welded joints were successfully achieved by laser welding, which can reach up to 88.4% and 67.5% of the wire BM ductility. The joint break force of the similar and dissimilar joints were of 77.2% and 71.4% of the wire BM, respectively. Moreover, laser welding was found to effectively preserve the PE on the similar welded structures. The residual plastic strain variation of the dissimilar welded specimens at different temperatures during the cycling test may be helpful for design of multi-functional or flexible monolithic structures.

Disproportionate Collapse Simulations

In recent years the ability to simulate and predict disproportionate collapse has seen growing interest among the scientific community. This is a challenging matter, since many authors have been dealing with the modeling of progressive collapse, and it is now well-established that such problem requires the use of many different non-standard modeling techniques together with extensive calibration. Despite the many papers in the literature, there is still a lack of methodologies tailored for the quantification of the structural robustness and its acceptable level, which clearly depends on the importance and function of the structure. Further, consideration of Performance Criteria as well as Decision Making Strategies, have to be supported by robust (but also efficient) modeling methods that have to include three-dimensional and geometrical non-linear effects. Some of the previously outlined principles about robustness will be discussed following which the authors present a methodology for taking into account that progressive collapse phenomena are governed not only by the dynamic response of the bays adjacent to the triggering event, but also by the residual plastic resources the structure conserves after the initial damage.

Welding distortion and inherent deformation under temporary tacking and its released states

In the present study, the detailed welding distortion of bead welded plates under temporary tacking state and released state was predicted by thermal elastic-plastic finite element model (FEM) and also measured by the digital image correlation (DIC) method. It was found that the residual welding angular distortion can be reduced to about 50–60% by temporary tacking, while the residual transverse shrinkage and longitudinal shrinkage are less affected. Further, the welding distortion with different ratios of temporary tacking length to weld length for various dimensions of bead welded plates was quantitatively investigated by FEM. The inherent deformations which are described by the integrated values of residual plastic strains were proved to be the same before and after releasing the temporary tacking. The effect of temporary tacking on the welding distortion and inherent deformation were analysed in details.

Dynamic mechanical behavior of foam-core composite sandwich structures subjected to low-velocity impact

The dynamic response of foam-core composite sandwich plates subjected to low-velocity impact is thoroughly investigated by means of drop-weight impact tests and numerical simulations in this paper. The influences of impact energy, foam-core thickness, and punch-head shape and size on the impact mechanical behavior including the impact force time history, the dynamic displacement time history, the residual plastic deformation, the energy absorption capacity, and the back plate deflection are contrastively studied through the control-variant approaches. Several conclusions drawn are useful and helpful to the related product design. The top faceplates of specimens with large foam-core thickness are demonstrated to be vulnerable to the low-velocity impact under stepped levels of impact energy, while large foam-core thickness can reduce deformation of the interior plates effectively. Moreover, among the three representative types of punch heads, the sharper hemispherical one is checked to be the most destructive with the lowest impact force peak. Besides, a finite element model was built to investigate the damage of faceplates and foam cores. The numerical method was proved to be accurate and efficient. A series of results were obtained revealing the damage mode of faceplates and cores under different impact energies.

Autoclave and ultra-sonication treatments of oil palm empty fruit bunch fibers for cellulose extraction and its polypropylene composite properties

Accumulation of residual plastics and the biomass wastes from agricultural sectors are causing serious global environmental problems if not addressed effectively. Cellulose with polypropylene as biocomposite material is an elegant strategy for value-added utilization of wastes. In this study, green isolation of cellulose from oil palm empty fruit bunches by autoclave-based and ultrasonication pre-treatments were developed to replace the non-green chlorite method. Ultrasonic treatment with hydrogen peroxide yielded 49% cellulose with 91.3% α-cellulose content and 68.7% crystallinity, as compared to 64% cellulose with autoclave treatment. Based on field emission scanning electron microscope, the ultrasonic and the autoclave-treated fibers showed complete separation of cellulose fibrils, with punctures and pores on the surface. High resolution transmission electron microscope and X-ray diffraction studies suggested monoclinic unitary crystal structure. The cellulose/polypropylene composite fabrications were achieved by using injection-molding technique where the composites with 25% cellulose loading gave high tensile strength of 27 MPa, without any addition of coupling agents. Thermogravimetric analysis study showed that the thermal stability of composites was enhanced by 150 °C as compared to singular cellulose and polypropylene. The low water and diesel uptake suggested the compact structure of the composites. This study has developed green techniques combining heat and eco-friendly chemical treatment for cellulose extraction from agro-lignocellulosic wastes. The cellulose/polypropylene composites developed with high tensile strength, high thermal stability, and low water and diesel sorption have great potentials for conversion into eco-composite products such as polymeric material insulated cables for high voltage engineering, automotive parts, sports tools and other household or office items.

Simulation of shot peening: From process parameters to residual stress fields in a structure

Manufacturing industries perform mechanical surface treatments like shot peening at the end of the manufacturing chain to protect important working parts. This treatment modifies the near surface of the treated part with the introduction of compressive residual stresses due to the repeated impacts of the shot. Then, the treated part exhibits, not only a longer life, but also a better fretting behavior, an improved resistance to corrosion… The objective of the present paper is first to study the relation between the process parameters and the material state (residual stress and plastic variables…) for a complex geometry. Next, a numerical tool is proposed, able to predict this material state in a time frame that is consistent with industrial constraints. The originality of the proposed approach thus consists in the chaining of the different steps. The first step is to choose the process parameters for the shot peening process considering conventional or ultrasonic shot peening and model the shot dynamics for a complex geometry. Once the impact velocity field is known, the objective is to compute the local incompatible plastic deformation field due to the repeated impacts using analytical methods. Then, a finite element model is used to compute the residual and deformation fields in the considered mechanical part. The complete method has been performed on the model of a gear, a mechanical part that is most often shot peened and exhibits a complex geometry.

Simulation of Plasto-Elastohydrodynamic Lubrication in a Rolling Contact

Surface plastic deformation due to contact (lubricated or dry) widely exists in many mechanical components, as subsurface stress caused by high-pressure concentrated in the contact zone often exceeds the material yielding limit, and the plastic strain accumulates when the load is increased and/or repeatedly applied to the surface in a rolling contact. However, previous plasto-elastohydrodynamic lubrication (PEHL) studies were mainly for the preliminary case of having a rigid ball (or roller) rotating on a stationary elastic–plastic flat with a fixed contact center, for which the numerical simulation is relatively simple. This paper presents an efficient method for simulating PEHL in a rolling contact. The von Mises yield criteria are used for determining the plastic zone, and the total computation domain is discretized into a number of cuboidal elements underneath the contacting surface, each one is considered as a cuboid with uniform plastic strain inside. The residual stress and surface plastic deformation resulted from the plastic strain can be solved as a half-space eigenstrain–eigenstress problem. A combination of three-dimensional (3D) and two-dimensional (2D) discrete convolution and fast Fourier transform (DC-FFT) techniques is used for accelerating the computation. It is observed that if a rigid ball rolls on an elastic–plastic surface, the characteristics of PEHL lubricant film thickness and pressure distribution are different from those of PEHL in the preliminary cases previously investigated. It is also found that with the increase of rolling cycles, the increment of plastic strain accumulation gradually approaches a stable value or drops down to zero, determined by the applied load and the material hardening properties, eventually causing a groove along the rolling direction. Simulation results for different material hardening properties are also compared to reveal the effect of body materials on the PEHL behaviors.