Plastic Metals Research Articles

Solid Waste Disposal Practices of the Atis (Aeta) of Boracay

The rising quality of life and high rates of resource consumption patterns had an unintended and negative impact both on the urban and rural environments and even on indigenous communities. Cities are now grappling with the problems of high volumes of waste, the costs involved, the disposal technologies and methodologies, and the impact of wastes on the local and global environment. This study is entitled Solid Waste Disposal Practices of the Atis (Aetas) of Boracay. The study was conducted to identify the Solid Waste Disposal Practices of the Atis in Boracay in terms of method of garbage storage and their methods of garbage disposal. It also seeks to identify activities/ programs implemented or practiced in the community to minimize improper waste disposal practices of every household in the community. The researcher to gather the information needed to be utilized a survey questionnaire. Interviews with 25 households and observations were conducted to further validate the authenticity of the data. Findings revealed that in terms of household garbage storage the respondents stored their garbage in a plastic bag, in an open container, and others pile it in the yard especially those biodegradable wastes. Concerning their garbage disposal practices, every household practiced proper segregation of waste. For their food waste, they put it in basket compost, while plastic containers, bottles, metals, and glass were segregated properly and disposed to a dumpsite through garbage collection. Trashes such as papers/cardboards were used for cooking by the Atis. Yard trimmings were used as compost as organic fertilizer. A once a week community cleaning is conducted by the Atis to maintain the cleanliness of their community where proper segregation of wastes was also monitored by the community organizer. In partnership with the Department of Agriculture Atis of Boracay were trained on basket composting to manage their biodegradable wastes. They were also guided by the policy of the Local Government Unit of Malay on proper wastes disposal.

ANALYSIS OF DOMESTIC SOLID WASTE MANAGEMENT STRATEGIES IN TUNGA, CHANCHAGA LOCAL GOVERNMENT AREA, NIGER STATE, NIGERIA

The management of solid wastes in Nigeria and other African Countries has become a very big challenge, t he problem of waste generation, handling and disposal has reached a disturbing level in Nigerian urban centers. The study analyzed domestic solid waste management strategies in Tunga, Niger State, Nigeria which was achieved through characterizing the types of domestic solid wastes generated, examining the domestic solid waste management strategies employed, identifying the key players in domestic solid waste management and ascertaining the effectiveness of the domestic solid waste management strategies employed in the study area. The primary data used in this study was obtained by direct field observations, questionnaire administration and oral interviews while the secondary data was obtained from books, journals, published and unpublished texts, documents, conference articles, government ministries and agencies. 327 out of 2040 households were sampled. The results showed that the nature of domestic solid wastes generated in the study area were mainly organic, paper, plastic, old and rusted metals and textile wastes while the domestic solid waste management strategies in place were burning, open dumping and burying, with open dumping being the most common domestic solid waste management strategy practiced in the study area. It was also observed that the key players involved in the management of solid wastes were the government and individual households and the rate of waste generation was found to exceed the rate of waste disposal in the study area. Also t he daily generation of waste (about 74%) exceeded the daily disposal of wastes (about 49%) in the study area. 63% of the respondents reported that burning of domestic solid waste is effective, 84% reported that burying domestic solid wastes is effective while 14% reported that open dumping of domestic solid wastes is effective. The C hi Square analysis showed a significant difference between the frequency of wastes generated and waste disposed in the study area with an alpha value of 0.01, while the Kruskal Wallis H test showed no significant difference in the effectiveness of the domestic solid waste management strategies in the study area (α= 0.646) .

Application of a nanosecond laser pulse to evaluate dynamic hardness under ultra-high strain rate

The paper presents results of experimental tests of plastic metals deformation generated by a shock wave induced by laser pulse. Tests were carried out on the Nd:YAG laser with a wavelength of 1064nm and the laser pulse of 10ns duration. The shock wave generate by the laser pulse was used to induced local plastic deformation of the material surface. The study examined the possibility of application the process to develop a new method of measuring the dynamic hardness of materials under ultra-high strain rate. It has been shown that the shock wave induced by the laser pulse with an energy of 0.35–1.22J causes a repeatable plastic deformation of surface of commercially available metals and alloys without thermal effects on the surfaces. Based on the knowledge of an imprint geometry, it is possible to evaluate the dynamic hardness of materials at strain rate in the range of 107s−1.

The evolution of pore shape and orientation in plastically deforming metals: Implications for macroscopic response and shear localization

A constitutive model is proposed for the macroscopic response of porous plastic metals at finite strains. Besides taking into account the porosity evolution, which leads to pressure sensitivity and dilatant response, the model can also account for changes in the average shape and orientation of the pores by means of suitable microstructural variables which play the role of internal variables and serve to characterize the evolving anisotropy of the material. In particular, the model is used to determine the evolution of the average shape and orientation of the voids under simple shear loading, as well as to explore the concomitant implications for the macroscopic response and shear localization. The intrinsic effect of the void rotations is deduced from comparisons with corresponding results for pure shear loading (where the voids change shape, but undergo no rotation on average), and found to be significant. In addition, more general loading conditions, involving combined tension and shear, are considered, and the effect of the stress triaxiality is investigated. For such more general plane strain conditions, it is found that there is an abrupt transition in the localization strain at a certain value of the triaxiality of about 0.3–0.4, with the localization strain dropping sharply both as the triaxiality increases, or decreases from this value. Furthermore, the results suggest that void rotations can dramatically enhance the susceptibility of the material to shear localization for a certain range of triaxiality values (between, approximately, 0.3 and 0.8).

Analytical elastic-plastic analyses of a spherical shell subjected to hydrostatic tension based on a strain gradient model for plastic metals

The problem of a spherical shell made of an elastic-plastic second gradient model for plastic materials and subjected to hydrostatic tension is considered. The elastic-plastic second gradient model is a simplified version (porosity neglected) of a second gradient model for plastic porous metals developed, some years ago, by Gologanu, Leblond, Perrin and Devaux, so-called GLPD model. The expressions of the velocity field as well as the ordinary and double stress components are determined for the cases where the spherical shell is modeled by a purely elastic, purely plastic, and elastic-plastic GLPD models. As expected, the solution developed in each case (elastic, ideal-plastic, and elastic-plastic) reduces to that of the first gradient as a special case when the characteristic length scale the GLPD model involves is negligible. Our results allow comparisons between the newly developed solution and the classical elastic-plastic solution for the same model problem; they also provide insights into the influence of the characteristic length scale on the newly developed solution.

Upper-bound analysis of die corner gap formation for strain-hardening materials in ECAP process

In this paper, the upper-bound solutions proposed by Eivani and Karimi Taheri (2008) to calculate processing force and evaluate die corner angle Ψ formation for distinct friction conditions and tooling geometry during single pass equal channels angular pressed perfectly plastic metals at room temperature were extended to work-hardening metals by using the Hollomon model combined to von Mises isotropic plasticity criterion. Also, plane strain finite-element models were developed to validate the proposed extended analytical solutions by comparing the predictions of angle Ψ, effective plastic strains and pressing force. Mechanical properties of an aluminum Al6070 alloy were considered and its behavior under pressing was evaluated to non-hardening and work-hardening conditions in all performed analyses. The theoretical predictions consistently showed that higher values of die corner angle Ψ and smaller predictions of both effective plastic strains and pressing force are obtained when the work-hardening behavior is included in the models independently of either tribology or tooling arrangements. These aspects were confirmed by comparison with the respective finite-element predictions. In addition, with the proposed upper-bound models it was possible to analyze the dependency of angle Ψ, effective plastic strain and pressing load with the instantaneous workpiece height at the entry surface of deformation zone.

Combined stretching and twisting of a circular thin-walled tube of second gradient plastic material

The objective of this work is to derive an analytical solution for the problem of a second gradient plastic circular thin-walled tube in combined tension and torsion loading conditions. Explicit expressions for the ordinary and higher-order stresses, strain rate and its gradient, and displacement are obtained. For comparison purpose, we also present the analytical solution for the same problem when the thin-walled tube is made of classical (von Mises) plastic metals. The newly micromorphic model based solution reduces to that of the (ordinary) von Mises one when the characteristic length scale approaches zero.

COMPARISON OF YIELD STRENGTH THEORIES WITH EXPERIMENTAL RESULTS

On the basis of the testing data of the yield strength of various types of plastic metals under biaxial and triaxial combined tensile-compressive principal stress, the relative errors calculated using Tresca strength theory, Mises strength theory, Mohr-Coulomb strength criterion, Beltrami's maximum energy theory and limiting strain energy strength theory (LSEST) are analyzed, respectively. The result shows that the errors according to LSEST are within 10%, being the minimum. The errors calculated by Tresca strength theory, Mises strength theory and Mohr-Coulomb strength criterion are -36%, -27% and -23%, respectively. The calculating results are on the conservative side compared with the test ones. For materials with equal tensile and compressive yield strength, Tresca strength theory and Mises strength theory could not be applied either, and the theoretical shear yield strength is times of the tensile yield strength. LSEST could be used to calculate the strength under biaxial and triaxial combined tensile-compressive principal stress, which is consistent with Rankine strength theory under a full tensile and a full compressive principal stress state, which suggests that LSEST has a prospect and value for engineering applications.

Fabrication and mechanical properties of ultrafine structured dissimilar laminated metal composite sheets (LMCS)

AbstractThe ultrafine grain structure is very difficult to fabricate by severe plastic deformation (SPD) for metals with poor formability. In this paper, a fabrication technology of ultrafine structured dissimilar laminated metal composite sheets (LMCS) was developed for poor plastic metals which have low elongation by hot accumulative roll bonding (ARB) in conjunction with cold rolling. The hot ARBed 1100/7075 LMCS was cold rolled at room temperature after recrystallization annealing treatment. An ultrafine structured dissimilar LMCS was obtained without undergoing severe cold rolled deformation. The mechanical properties were enhanced and optimized by using heat treatment technology. The accelerated refining mechanism of grain was revealed by microstructure characterization of the composite sheet. The enhanced strength was mainly derived from the fine layers, refined grains, increased dislocation accumulation, and abundant dispersoids. The results of the research are helpful in improving the mechanical properties of dissimilar LMCS and optimizing the preparation technology.

Configuration of the cutting-force vector in turning plastic metals

A method is proposed for determining the angle of the cutting-force vector in turning plastic metals by a hard-alloy tool at maximum productivity (maximum profit), on the basis of a mathematical model of the dissipation rate in chip formation as a function of the cutting parameters.

Evaluation of dry solid waste recycling from municipal solid waste: case of Mashhad city, Iran

The recycling for recovery and reuse of material and energy resources undoubtedly provides a substantial alternative supply of raw materials and reduces the dependence on virgin feedstock. The main objective of this study was to assess the potential of dry municipal solid waste recycling in Mashhad city, Iran. Several questionnaires were prepared and distributed among various branches of the municipality, related organizations and people. The total amount of solid waste generated in Mashhad in 2008 was 594, 800 tons with per capita solid waste generation rate of 0.609 kg person(-1) day(-1). Environmental educational programmes via mass media and direct education of civilians were implemented to publicize the advantages and necessity of recycling. The amount of recycled dry solid waste was increased from 2.42% of total dry solid waste (2588.36 ton year(-1)) in 1999 to 7.22% (10, 165 ton year(-1)) in 2008. The most important fractions of recycled dry solid waste in Mashhad included paper and board (51.33%), stale bread (14.59%), glass (9.73%), ferrous metals (9.73%), plastic (9.73%), polyethylene terephthalate (2.62%) and non-ferrous metals (0.97%). It can be concluded that unfortunately the potential of dry solid waste recycling in Mashhad has not been considered properly and there is a great effort to be made in order to achieve the desired conditions of recycling.

Analysis of complete plasticity assumption for solid circular shaft under pure torsion and calculation of shear stress

The distribution of shear stress on the cross-section of plastic metal solid circular shaft under pure torsion yielding, the applicability of complete plastic model assumption and the shear stress formula were researched. Based on the shear stress formula of circular shaft under pure torsion in elastic stage, the formula of torque in elastic stage and the definition of yield, it is obtained that the yielding stage of plastic metal shaft under pure torsion is only a surface phenomenon of torque-torsion angle relationship, and the distribution of shear stress is essentially different from that of tensile stress when yielding under uniaxial tension. The pure torsion platform-torsion angle and the shape of torque-torsion angle curve cannot change the distribution of shear stress on the shaft cross-section. The distribution of shear stress is still linear with the maximum shear stress τs. The complete plasticity model assumption is not in accordance with the actual situation of shaft under torsion. The experimental strength data of nine plastic metals are consistent with the calculated results of the new limiting strain energy strength theory (LSEST). The traditional yield stress formula for plastic shaft under torsion is reasonable. The shear stress formula based on the plane assumption in material mechanics is applicable for all loaded stages of torsion shaft.

Process Parameter Experiments on Vacuum Casting Using a Silicone Rubber Mold for ABS Plastic Parts

Silicone rubber mold is one of soft mold processes for rapid tooling. Based on a master pattern, it can be used for casting the materials of wax, plastic, and low-melting metals directly during a short developing time, very suitable for sample fabrications. This paper conducts vacuum casting experiments by Taguchi’s method to derive the optimal parameter selections on ABS plastic vacuum casting using a silicone rubber mold. The factor that affects pouring characteristics maximally is the mold vacuuming time.

A novel limiting strain energy strength theory

With applied dislocation theory, the effects of shear and normal stresses on the slide and climb motions at the same section of a crystal were analyzed. And, based on the synergetic effect of both normal and shear strain specific energies, the concept of the total equivalent strain specific energy (TESSE) at an oblique section and a new strength theory named as limiting strain energy strength theory (LSEST) were proposed. As for isotropic materials, the plastic yielding or brittle fracture of under uniaxial stress state would occur when the maximum TESSE reached the strain specific energy, also the expressions on the equivalent stresses and a function of failure of the LSEST under different principal stress states were obtained. Relationship formulas among the tensile, compressive and shear yield strengths for plastic metals were derived. These theoretical predictions, according to the LSEST, were consistent very well with experiment results of tensile, compressive and torsion tests of three plastic metals and other experiment results from open literatures. This novel LSEST might also help for strength calculation of other materials.

Predicting the rheological parameters of plastic metals with self-organization of the viscoplastic flow in the cut layer

The stress and strain, strain rate and loading rate, internal-friction coefficients (viscosity), and deformation time of the cut layer are predicted for structural carbon steels and alloy steels characterized by self-organization of the viscoplastic flow on turning. Physical models of the metal’s viscoplastic-flow parameters in the chip-formation zone are employed.

Mechanical and electrical properties of nanostructured ‘plastic metals’

Abstract Deformable, supraspherical (SS) aggregates of metal nanoparticles (NPs) connected by long-chain dithiol ligands self-assemble into nanostructured materials of macroscopic dimensions. These materials are both malleable/moldable at room temperature as well as electrically conductive. Upon gentle heating, they harden into polycrystalline metals. The paper discusses qualitative models that rationalize the mechanical and electrical properties of these unusual ‘plastic metals’.

Effect of mechanical activation on the characteristics of ruthenium and aluminum powder mixtures

The effect of treatment in a high-energy mill-attritor on the structure of RuAl-based alloy powder mixtures and the exothermic effects in them is studied. The mechanical activation (MA) of aluminum and ruthenium powder mixtures is found to mill the conglomerates of hard disperse (0.5–2 μm) ruthenium particles in the initial mixtures and to produce composite granules. These granules consist of hard disperse ruthenium particles connected by plastic fcc aluminum particles. The structure of these granules differs from that of the layered granules that form during the MA of powder mixtures of two plastic fcc metals (nickel, aluminum). The cold working of the hard ruthenium particles, which have the hcp lattice and are deformed via twinning, occurs due to a decrease in the coherent domain size (to 120–80 nm) rather than to an increase in the dislocation density (as in the case of the MA of Ni-Al powders). Every granule contains all alloy (composite) components, including disperse or nanosize oxide particles, bound to the components that form an intermetallic matrix during reaction sintering. In granules of both types, MA increases the contact area between both metals entering into the reaction of RuAl (NiAl) formation and sharply decreases the diffusion path length of Al in Ru (Ni). This results in a decrease in the temperature of the onset of reaction alloy formation, which begins now in a solid phase, and in a decrease in the exothermic effect of the monoaluminide formation with the participation of a liquid phase (Al). MA for 15–16 h of powder mixtures provides a microuniform distribution of base and alloying elements and phases in the deformable alloys with an intermetallic matrix that are produced by reaction sintering.

Thermo-mechanical and diffusion modelling in the process of ceramic–metal friction welding

In this paper a modelling of friction welding of elastic materials with elastic–plastic metals is presented. This model has been practically verified in the process of friction welding of corundum ceramic of 97.5% Al 2O 3 content and aluminium alloy 6061-T6 as well as in the same ceramic and electrolytic copper of 99.9% Cu content. Mechanical strength of the acquired welded joints was around 30 MPa. A simulation of the process was performed by means of the finite element method using two FEM systems, namely ADINA-T and ADINA. The simulations made it possible to observe the temperature distribution and thermo-mechanical fields that take place during the process. The obtained results show that the temperature, pressure and the deformation distribution near the contact surface are non-homogeneous. It causes not even conditions to create the bond and internal stresses generation. The agreement between the numerical geometry prediction and the experimental data proves the validity of the proposed model. The performed calculations and preliminary studies on the influence of the diffusion phenomena on the welding process showed that the diffusion depth is approximately 4 μm and the calculated diffusion coefficient of Al into Al 2O 3 is 1.8 × 10 −13 m 2/s. Numerical simulation of the friction welding process allows better understanding of the whole process, final products shape prediction and can be helpful during design of the process using other materials.

Observation of shear plane instability during microgrinding of plastic metals

The abnormal loads placed on the metal chip during the first encounter with the cutting tool manifest themselves as an unpredictable curl that forces the chip to distance itself from the surface of the rake face. Frictional interactions between a metal chip and the rake face of a virgin cutting tool reveal the complex nature of initial chip formation and shear plane instabilities during the first few seconds of intimate contact. The variation of the load causes a shear plane instability that is directly observed using a high-speed camera and a specially designed machining apparatus. As the variation of load progresses, the chip tends to curl away from the tool with varying radii until the apparently curved shear plane becomes linear. The results of initial chip formation demonstrate a very complex interaction between metal chip and rake face of the tool and the resulting development of the shear plane and its effect on chip formation.

Shear strain induced formation of nanostructured pure metals

Chip formation is of fundamental importance during the formation of nanostructured pure metals. Poor chip control leads to chip build-up and an uncontrollable surface roughness. The use of chip breaking is arbitrary because of the mechanics of chip curl is not well understood. The causes of chip curl and chip flow are still the subject of intense discussion and research among plasticity researchers. The subject originally focused on cutting forces and on the conditions at the chip-tool interface using soft plastic metals. The increasing speed of cutting has focused researchers to look at chip breaking after the chip has been cut. In the first instance, chips were considered to be continuous, discontinuous and continuous with a built-up edge. The theories of metal cutting allow one to predict the forces and stresses in the chip during formation but do not tell us anything about the strain within the chip, unless a computational approach is used. This paper describes the mechanics of chip formation using the grinding process at the microscale and explains how the deformation of the grinding grains affects shear strain rates and the average grain size in the cut chip.