Plastic Material Properties Research Articles

Assessing Mechanochemical Properties of Acrylonitrile Butadiene Styrene (ABS) Items in Cultural Heritage Through a Multimodal Spectroscopic Approach.

A multimodal spectroscopic approach is proposed to correlate the mechanical and chemical properties of plastic materials in art and design objects, at both surface and subsurface levels, to obtain information about their conservation state and to monitor their degradation. The approach was used to investigate the photo-oxidation of acrylonitrile butadiene styrene (ABS), a plastic commonly found in many artistic and design applications, using ABS-based LEGO bricks as model samples. The modifications of the chemical and viscoelastic properties of ABS during photoaging were monitored by correlative Brillouin and Raman microspectroscopy (BRaMS), combined with portable and noninvasive broad-range external reflection infrared (IR) spectroscopy and nuclear magnetic resonance (NMR) relaxometry, directly applicable in museums. BRaMS enabled combined measurements of Brillouin light scattering and Raman spectroscopy in a microspectroscopic setup, providing for the coincident probe of the chemical and mechanical changes of ABS at the sample surface. NMR relaxometry allowed for noninvasive measurements of relaxation times and depth profiles which are directly related to the molecular mobility of the material. Complementary chemical information was acquired by external reflection IR spectroscopy. The simultaneous probe of the chemical and mechanical properties by this multimodal spectroscopic approach enabled us to define a decay model of ABS in terms of compositional changes and variation of stiffness and rigidity occurring with photodegradation. The knowledge acquired on LEGO samples has been used to rate the conservation state of ABS design objects noninvasively investigated by external reflection Fourier transform IR spectroscopy and NMR relaxometry offered by the MObile LABoratory (MOLAB) platform of the European Research Infrastructure of Heritage Science.

Size Dependency of Elastic and Plastic Properties of Metallic Polycrystals Using Statistical Volume Elements

We present an efficient approach to evaluate the size dependency of elastic and plastic properties of metallic polycrystalline materials. Specifically, we consider different volume fractions of ferrite and martensite phases for the construction of three macroscopic domains. Statistical Volume Elements (SVEs) of different sizes are extracted from these domains using the moving window method. Linear and Crystal Plasticity (CP) simulations provide elastic and plastic properties of the SVEs such as the bulk and shear moduli, yield strength, and hardening modulus. We use a variation-based criterion to determine the Representative Volume Element (RVE) size of these properties. This RVE size corresponds to a size beyond which the given property can be idealized as homogeneous. We also use anisotropy indices and an additional RVE size criterion to determine the size limits beyond which these properties can be idealized as isotropic. Numerical results show that the plastic properties often reach their homogeneity and isotropy limits at larger sizes compared to elastic properties. This effect is more pronounced for the hardening modulus compared to the yield strength.

A novel variable restitution coefficient model for sphere–substrate elastoplastic contact/impact process

The restitution coefficient serves as a critical parameter to evaluate the energy loss during the contact/impact process. Its in–depth researches are beneficial to accurately describing the contact/impact phenomenon. Given the limitations of existing restitution coefficient models, a novel variable restitution coefficient model, which considers the material properties and the initial relative contacting velocity between two colliding bodies, is proposed in this work. Firstly, the function relationship between the restitution coefficient and the equivalent plastic strain can be obtained based on the energy equivalence principle. After that, multi–condition FEM numerical simulation cases are conducted to explore the mapping relationship among the equivalent plastic strain, material properties and initial relative contacting velocity, with which the new normal variable restitution coefficient model can thus be established. Finally, various comparisons with several existing restitution coefficient models are conducted to showcase its superior performance, with the low–speed experimental data and high–speed FEM results acting as reference values. Furthermore, the new restitution coefficient model is extended to describe interaction process between two spheres, and also employed for the establishment of a new continuous contact force model.

Clarification of the plastic deformations zone borders for the fuel tank diaphragm

A relevant area of theoretical and practical research in the field of rocket science is ensuring the uninterrupted and reliable operation for liquid rocket engines. Reliable operation and engine start in zero gravity is impossible without guaranteed separation of the liquid and gas phases in the fuel tank. This problem is solved by the introduction of metallic reversible diaphragm separators. The eversion process research for the metal diaphragm separators allows you to design them for fuel tanks of various sizes and shapes according to the specified parameters of the displacement of the component. This is an actual object of research. The known mathematical dependencies do not have sufficient accuracy and correspondence to experi- mental results. To improve the quality of design when using any deformation-energy approach, it is necessary to increase the accuracy of determining the boundaries for plastic deformation zone of diaphragms at various stages of eversion. Clarification of the boundaries for this zone is possible using modern computer modeling tools. The article provides a descriptions and simulation result for metal diaphragms with different geometric parameters, loaded with uniform pressure, taking into account the plastic material properties in the MSC NASTRAN software package. As a result of the work, a refined zone of plastic deformation for fuel tanks metal eversible diaphragms was determined. We have introduced new angles to describe this zone. The dependences for these angles on the angle of the torus region, independent of the geometric parameters of the diaphragm, were obtained. We also identified the conditions under which the use of the energy principle equation is inappropriate due to the presence of membrane stresses.

Atomic-scale insights into grain boundary-mediated plasticity mechanisms in a magnesium alloy subjected to cyclic deformation

Sustaining grain boundary (GB) plasticity is important to prevent the premature GB cracking during plastic deformation of hexagonal-close-packed (HCP) materials. Here, we investigated atomic structures of GBs and their deformation modes in the form of motion, twin nucleation, dislocation emission, and dissociation in a HCP magnesium alloy subjected to cyclic deformation, according to atomic-resolution observations and crystallographic analyses. Besides migration and sliding, symmetric tilt GBs tended to move to form local facets, resulting in generation of asymmetric tilt low-angle GBs (LAGBs) parallel to {101¯2} lattice plane or serrated asymmetric tilt high-angle GBs (HAGBs). Crystallographic analyses indicated that local facets of the resultant asymmetric tilt GBs were often parallel to {101¯2} plane, basal and/or prismatic planes of adjacent grains. Interestingly, abundant {101¯2} twin embryos and recrysatllized nanograins nucleated from local facets of the asymmetric tilt GBs, accompanying with emission of arrays of basal 〈a〉 dislocations. A {101¯2} twin lamella along a tilt LAGB could be formed either by the coalescence of {101¯2} twin embryos, or by the combination of recrystallized nanograins, followed by {101¯2} twin nucleation from triple junctions of GBs and twin growth. Furthermore, the twin lamella could be formed through dissociation of one tilt LAGB into two tilt HAGBs, followed by {101¯2} twin nucleation from the HAGBs and triple junctions of GBs. Importantly, activation of GB deformation modes mentioned above can release local stress concentrations at GBs and sustain the ability of GB-mediated plasticity, playing important roles in plastic deformation and mechanical properties of HCP materials.

Characterization of Nano- and Microstructures of Native Potato Starch as Affected by Physical, Chemical, and Biological Treatments.

Modifying starch allows for improvements in its properties to enable improved uses in food matrices, bioplastics, and encapsulating agents. In this research, four varieties of native potato starch were modified by acid treatment, enzymatic treatment, and ethanol precipitation, and their physicochemical, structural, thermal, and techno-functional characteristics were analyzed. According to FT-IR analysis, no influence of the modified starches on the chemical groups was observed, and by scanning electron microscopy (SEM), spherical and oval shapes were observed in the acid and enzymatic treatments, with particle sizes between 27 and 36 μm. In particular, the ethanolic precipitation treatment yielded a different morphology with a particle size between 10.9 and 476.3 nm, resulting in a significant decrease in gelatinization temperature (DSC) and more pronounced crystallites (XRD). On the other hand, the enzymatic treatment showed higher values for z-potential (ζ), and the acid treatment showed lower mass loss (TGA). Acid and ethanolic treatments affected the dough properties compared to native starches. The techno-functional properties showed a decrease in the water absorption index, an increase in the water solubility index, and varied swelling power behaviors. In conclusion, the modification of potato starches through acid, enzymatic, and ethanolic precipitation treatments alters their physicochemical properties, such as swelling capacity, viscosity, and thermal stability. This in turn affects their molecular structure, modifying morphology and the ability to form gels, which expands their applications in the food industry to improve textures, stabilize emulsions, and thicken products. Furthermore, these modifications also open new opportunities for the development of bioplastics by improving the biodegradability and mechanical properties of starch-based plastic materials.

Effective Plastic Properties of Porous Materials with an Inverse Opal Structure

Effective Plastic Properties of Porous Materials with an Inverse Opal Structure

Simulation of fretting wear in steel wires under variable coefficient of friction and variable wear coefficient

In this paper, the fretting wear behaviour of steel wires working in coal mining technology is studied numerically. In past studies, the fretting process of steel wires was carried out numerically considering that the coefficient of friction (COF) and wear coefficient (WC) are constant parameters. However, it has been noticed experimentally that COF increases up to a certain number of fretting cycles and then becomes constant, i.e. a steady-state stage, depending on the loading conditions. This increase in COF during the fretting process is also known as the running-up stage. The fretting wear model is modified to evaluate the influence of the varying coefficient of friction (VCOF), which is associated with the variable wear coefficient (VWC), so the influence of VWC is also considered. The subroutine UMESHMOTION used to implement the wear law is also modified to study the effect of VCOF and VWC. Therefore, in this study, the numerical results of a three-dimensional finite element (FE) model are compared, with analytical results of contact area and contact stresses, and with experimental results of peak wear depth. After validating the FE model, the wear scar, the increasing wear depth, wear volume, and the decreasing contact stress with increasing fretting cycles are determined numerically considering VCOF and VWC using cycle jump approach. The energy dissipation effect of frictional force and fretting amplitude is also studied for varying interaction properties of fretting wear models. The numerical simulations are performed by considering both elastic and plastic material properties to analyse the influence of varying interaction properties on fretting wear models at the running-up stage. The results indicate that the VWC model exhibits comparable impacts on both the elastic and plastic models. The results also show that the VWC fretting wear model leads to higher wear scar, wear volume, and wear depth values at the running-up stage as well as at the steady state stage, which are close to the experimental data.

Revealing the percolation–agglomeration transition in polymer nanocomposites via MD-informed continuum RVEs with elastoplastic interphases

This contribution builds the concluding step of a multiscale approach to effectively capture the mechanical behavior of polymer nanocomposites (PNCs), in this case, silica-modified polystyrene. By introducing continuum-based representative volume elements (RVEs) that employ previously identified elastoplastic property gradients for the interphases surrounding the fillers, the effects of particle size, particle volume fraction, and agglomeration on the mechanical performance are investigated. Uniaxial tension tests are simulated with the respective finite-element RVEs, and stress–strain curves are derived. The elastic and plastic material properties of the RVE can then be extracted and analyzed quantitatively by fitting the stress–strain curves with a Voce-type elastoplasticity formulation.At small degrees of agglomeration, i.e., good particle dispersion, in combination with sufficiently large particle volume fraction, percolation bands form, leading to improved elastic and plastic properties. Higher degrees of agglomeration or particle clusters behave like large single particles, which has an adverse effect, i.e., the nanoscale size effect is thereby neutralized. Therefore, the precise MD-informed elastoplastic interphase representation of our RVEs enables the investigation of the transition from beneficial percolation to unfavorable agglomeration. Ultimately, this contribution establishes a link between the effects of particle size, particle volume fraction, agglomeration, and percolation, which have so far only been discussed separately in the literature.Our methodology offers new insights into the structure–property relations of PNCs and their resulting mechanical behavior. The underlying multiscale approach with a systematic transition from molecular to microscopic scales is required to complement experimental observations and exploit the full potential of PNCs.

Influence of Interface Type on Dynamic Deformation Behavior of 3D-Printed Heterogeneous Titanium Alloy Materials.

Using the Split Hopkinson Pressure Bar technique, strain-limited dynamic compressive loading experiments were performed on TA1/TA15 heterostructure (HS) materials. The plastic deformation mechanisms, fracture forms, and energy absorption properties of an HS material with a metallurgical bonding interface (MB) and an HS material without a metallurgical bonding interface (NMB) are compared and analyzed. The results show that there is no significant difference between the two deformation mechanisms. The fracture forms are all "V-shaped" fractures within the TA1 part. The NMB was carried for 57 μs before failure and absorbed 441 J/cm3 of energy. The MB was carried for 72 μs before failure and absorbed 495 J/cm3 of energy. Microstructure observations show that there is a coordinated deformation effect near the MB interface compared to the NMB, with both TA1 and TA15 near the interface carrying stresses. This causes an enhancement of the MB load-bearing time and a 12% increase in energy absorption.

An experimental study into the degradation of elastic, plastic and fracture properties of a pre-corroded ductile material at elevated temperatures

Carbon steel is one of the most commonly used engineering materials. However, the mechanical properties of steel deteriorates due to exposure to harsh environments like corrosive surroundings and high temperatures. Extensive studies have been done to understand the exclusive effect of corrosion and high temperatures on tensile and fracture properties, although their combined effect has not been addressed. The present work aims to experimentally investigate this by conducting tensile and fracture tests at elevated temperatures on pre-corroded ductile steel. Pre-corroded steel was considered with corrosion levels up to 55%. Empirical relationships were established to quantify the degradation in tensile and fracture properties. An unloading compliance approach using a single specimen was utilized to determine the J-integral fracture toughness and also establish traction separation relation for mode I. The results reveal that the combined influence increases the degradation in fracture toughness, but it restricts the degradation in tensile properties.

Consideration of Moisture Factor during Material Selection in Plastic Product Design

This research paper aims to investigate the significance of considering the humidity factor during material selection in plastic product design. Humidity is a crucial environmental parameter that can profoundly influence the properties and performance of plastic materials. To ensure the long-term performance and dependability of plastic products, it is essential to comprehend and take into consideration the impacts of moisture on plastics. Humidity plays a fundamental role in the degradation and functional changes of plastic materials. Moisture absorption can lead to reduced mechanical strength and accelerated degradation processes. The selection of appropriate materials that can withstand humid conditions becomes paramount in product design. For this reason it is important to evaluate the moisture absorption properties of plastic materials. Different polymers exhibit varying degrees of moisture diffusion rates that directly affect their performance in humid environments. Evaluation of moisture measurement results allows designers to make informed decisions during material selection. For this reason, we designed an experiment to investigate which material retains less moisture. In our research, we determined 2 different experimental groups. The first of these groups (type A) was kept under normal conditions by adding glass fiber additive at different rates to the PA66 material, and each product with 3 different additives was tested for moisture for 10 days and the results were recorded. In the second experimental group, type B, the products produced with the same material and additives at the same rate were kept in water for 24 hours, then they were removed from the water and moisture tests were performed. It is aimed to make material selection by interpreting the test results and thus to facilitate the making of designs suitable for use.

Solution to the problem of low sensitivity of crack closure models to material properties

The paper focuses on differences between crack closure obtained by numerical models and by experimental fatigue crack growth rates, namely for three different steels (bainitic steel, predominantly pearlitic steel and additively manufactured austenitic stainless steel). The experimental data revealed a load ratio effect different from that predicted by the most used plasticity-induced crack closure (PICC) models. The term “irreversibility of plastic deformation” was proposed in this work to be used as a material property to estimate how strong the PICC effect would be in a material. Two basic phenomena, which are usually omitted in other models, were considered in the explanation: (i) cyclic softening/hardening, (ii) brittle microcracking at the maximum load. The strip-yield model has the ability of conducting fast and accurate simulations under the variable-amplitude loading. It was demonstrated that the results of this model are practically independent of the material properties. This is caused by the consideration of only monotonic elastic–plastic material properties. To simulate real load ratio effects, the parameter β in the strip-yield model (constraint factor in compression) is proposed to be used as a variable. It enabled a generation of different ratios of monotonic and cyclic plastic zones, which in turn helped to reproduce the crack closure values observed experimentally. Discussion and explanations were provided regarding the material microstructure. The proposed approach considers unequal tensile and compressive yield stresses caused by the different irreversibility of plastic deformation, which explains the dissimilarities in the load ratio effect observed in the investigated materials. It can also improve the accuracy of residual fatigue life estimations.

The combined research of ultra-high vacuum CF flange joints' sealing parameters considering plastic properties of materials

Computer simulation and experimental research of the tightening processes of ultrahigh vacuum CF flange joints have been carried out. Finite element analyses were carried out considering the plastic properties of materials. The analysis variable parameters are flanges' knife edge angle between the shelves (Wheeler's and CERN's models), tip rounding radiuses, and gasket material state (annealed and hard). Curves of changes in the stress and strain intensities of the edge nodes of the flanges' knife edge were obtained. Essential sealing parameters of the ultrahigh vacuum system were also studied, such as the height of the knife edge, the length of the knife-edge trace on the gasket (in the radial direction), and the gap between two flanges. The mentioned sealing parameters' measurements were carried out by the combined method. The latter is a parameters' measurement of both computer simulation and experimental samples and a comparison of the obtained results. It should be noted that the sealing parameters were studied for several tightening cycles of the flanges to research their changes in case of multiple uses. The vital value of this research is obtained empirical functions for calculating the height of the flanges' knife edge based on the tightening cycles.

Probabilistic finite element-based reliability of corroded pipelines with interacting corrosion cluster defects

The random distribution of pitting corrosion defects in pipelines normally leads to interacting cluster defects that behave noticeably different from single metal loss defects. Generally, the probabilistic approaches employ explicit burst pressure limit states for corroded pipelines subjected to only internal pressure. However, a significant level of conservatism is typically associated with the probabilistic assessments of corroded pipelines using the closed-form explicit limit state functions, which presents considerable challenges in maintenance planning and risk management. Therefore, this paper proposes a pathway for developing efficient performance functions for the assessment of interacting pipeline corrosion clustering defects using probabilistic finite element-based reliability method. This seven-stage framework combines multiple uncertainty representation schemes to evaluate the probability of failure. The impact of the critical design variables such as the elastic and plastic material properties, corrosion features, and interacting cluster defect characterisations are identified to guide the burst pressure design, operations and maintenance optimisation. The employed surrogate-based active learning reliability approach yielded an efficient probability estimate at a lesser computational cost than the simulation-based reliability methods. The proposed framework reduces the conservatism and computational cost related with explicit burst pressure limit state functions for corroded pipelines and offers informed decision-making on risk and maintenance management.

INNOVATIONS FOR SUSTAINABLE PLASTIC WASTE MANAGEMENT IN NIGERIA

The use of plastic is increasing rapidly every year and this trend is likely to continue because of the extreme versatile nature of the properties of plastic materials which gives it use for wide range of purposes. This paper presents a current scenario of plastic consumption in Nigeria and also attempts to address the problem of plastic waste disposal and its attendant environmental hazards by discussing the various innovative ways of utilizing plastic wastes in order to promote a sustainable environment. The paper highlighted the challenges faced by the different innovative techniques and also the approaches that can be adopted to overcome the challenges for its survival in the circular economy. The literature review touched on works of related studies and discussed many innovative approaches for utilizing plastic waste. The key sources of literature in this review paper included peer-reviewed articles, news post, project briefs and professional reports. It is hoped that the implementation of the noble ideas and innovative technologies discussed in this work will enable proper and effective management of plastic waste in Nigeria.

Morphological, surface and thermal properties of polylactic acid foils, melamine-etherified resin, and polyethylene terephthalate fabric during (bio)degradation in soil

The (bio)degradation of plastics in soil is a complex process that depends on several factors, such as the type of plastic, environmental conditions, microbial activity, and the presence of other organic matter in the soil. Ageing in soil thus also influences the physicochemical properties of plastic materials. To understand the mechanisms and investigate the changes in plastic properties in soil due to decomposition and followed by fragmentation, the gravimetric, morphological, surface, and thermal properties of plastics were studied, some of them for the first time. The study was performed for three different plastics materials, polyethylene terephthalate (PET-fib) and melamine etherified resin (MER-fib) in the form of nonwoven fabrics and polylactic acid (PLA) in the form of foils. The materials were exposed to soil for one, three and six months, only in the case of PLA foil for final four months. The results show that remarkable changes were observed especially for MER-fib and PLA after exposure to soil, which is related to the bio and chemical degradation proceses. The biodegradation process was indicated with the soil microorganisms used in the study (lactic acid bacteria, photosynthetic organisms, yeasts, actinomycetes, and enzymatically active fungi), while chemical degradation showed that it may occur at the surface of the material with changes in elemental composition and chemical functionality. The microbial end products of biodegradation of MER-fib are presumably NH3 and CO2, while for PET-fib it is CO2 and for PLA it is CO2 and H2O, including several proposed conversion products in partial pathways. The study represent an important contribution to understanding the behaviour of the analysed (bio)plastics and the changes in their properties after exposure to natural systems for pollution countermeasures and cleaner production.

Determination on the fracture toughness of the welded joints of X80 pipeline steels based on small punch test

For the sake of design and integrity assessment of the fracture toughness of high-grade pipelines, it is necessary to carry out accurate fracture toughness assessment of the welded joints. The study of more concise and effective fracture toughness testing methods has important theoretical and engineering value. At present, the fracture control of girth welding joints is mainly based on J integral, CTOD and CTOA. However, it is hard to carry out standard fracture toughness tests at some local narrow areas of the welded joints such as the heat affected zone for the difficulty of sampling. On this basis, this paper aims to propose a method to determine the fracture initiation toughness JIC of the welded joints of high-grade pipeline steels based on the micro-sample test method - small punch test. Firstly, small punch specimen with through-thickness notch was designed. Secondly, the finite element model of the notched specimen was established, and verified by the notched specimen tests of X80 steel. Furthermore, the elastic–plastic material properties of different zones of the welded joint were obtained by the empirical correlation method of small punch test and further used for the determination of J contour integral. The GTN damage parameters were calibrated by the three-point bending tests and further used for the determination of the crack initiation displacement. Finally, the fracture initiation toughness JIC(SPT) of different zones of the welded joint were obtained by the SPT method and verified by the three-point bending test. The results show that the fracture initiation toughness JIC(SPT) of each region of the welded joint obtained by notched SPT specimen were all less than the SENB test results. But there is a good empirical correlation between the two results so that the SPT method can be further modified by establishing an empirical correlation model. The SPT method has good engineering application prospect for the accurately characterization of the different distribution of fracture toughness in different areas of the welded joints.

Analytical model for measurement of stresses using two-hole drilling

Residual stresses have a significant effect on the strength, deformation, plasticity, and fatigue properties of materials. In general, tensile residual stresses are adverse to material performance and component life, while compressive residual stresses can improve material fatigue strength. In this study, an analytical model employing two-hole drilling (THD) is proposed for the measurement of interior stresses. Firstly, the analytical solution for the distortion of the reference hole induced by drilling an adjacent hole is derived using the complex variable method. Based on the analytical solution, the reverse procedure is established to determine the original stress state. Then, the comparative validations of the THD method with the deep hole drilling (DHD) method are performed in conjunction with the finite element (FE) simulations for the beam subjected to bending, the unloaded elastoplastic beam, and the shrink fitted assembly. Finally, parametric analysis is conducted and the results show that: the influence of drilling an adjacent hole on the reference hole rises with the increase of the hole diameters or the decrease of the hole spacing; the THD method is able to give good estimations for the stresses with linear, parabolic, and sinusoidal distributions, although the accuracy is reduced for the prediction of the longitudinal residual stress in the cold-formed section; the uncertainties in evaluated stresses ascend linearly with the increase of the measurement error in the diameter of the reference hole. Relative to the DHD method, the THD method has the merits of less damage and less equipment required and can provide an effective approach for the measurement of stresses inside materials.

Influence of plasticity and vibration isolators on an underground floating slab track using finite element analysis

The floating slab track (FST) is largely viewed as the most efficient structure for mitigating the vibrations caused by underground railway systems. This paper presents a study on the dynamic behavior of the FST subjected to train-induced vibrations using a finite element approach. A three-dimensional simulation model of an FST was analyzed under a moving load. The effects of material plasticity of underground strata and concrete damaged plasticity of the floating slab were analyzed. A comparison between the vibration attenuation of the steel-spring isolator (SSI) and polyurethane pad (PUP) was performed. The load was moved at constant speeds ranging from 90 to 324 km/h using a pressure-loaded moving block. The results were analyzed in the form of four general output parameters. A slight vibration attenuation was observed when plastic material properties were included in the simulation model. The PUP was more effective in reducing vibrations at FST than SSI by a vibration transfer mechanism.