Progressive Loss Of Material Research Articles

The Wear Rate Forecast of MgO-C Materials Type MC95/10 in the Slag Spout Zone of an Oxygen Converter in Terms of the Bayesian Estimation.

The ceramic–carbon refractory lining of an oxygen converter is subjected to variable thermochemical stresses, causing a progressive loss of material over time, which is expressed in a decreasing residual thickness of the lining. The forecasting method using Bayesian statistics has become a valuable skill in steel production planning and is one of the main conditions constituting the appropriate organization of steel and refractories production. This paper presents examples of Bayesian modelling of the unit wear rate value of the refractory materials for the zone with the highest wear in the refractory lining of a converter. From the experience gained during long-term operation of a steel-producing oxygen converter, it was found that the value of the unit wear rate of the refractory material in the slag spout zone of the steel-producing oxygen converter is subjected to an a posteriori normal distribution, with the following parameters: mean value µ = 401.23 µ heat−1, standard deviation σ = 13.74 µm heat−1. The forecasted mean value of the unit wear rate of the MC95/10 refractories lined in the slag spout zone of the oxygen converter used for steel production, and which operates in intensive exploitation conditions, was equal to µ = 420 µm heat−1.

Effect of Heat Treatment Methods on the Fatigue Behaviour of Hammermill: A Review

The production of reliable and sustainable hammermill involves heat treatment which is part of overall cost of production. Heat treatment has engrossed a lot of interests since it is one of the main production methods to improve corrosion resistance of coatings, enhancing malleability, hardness and strength to lessen mechanical or chemical damage. Nevertheless, various heat treatment procedures had resulted to hammermill failure as a result of material wear, erosive wear, impact wear, machine clogging and shock loading wear which eventually affects the efficiency of the hammermill. The study thus engrossed on some particular thermal treatment on mild steels and their impacts on hammermill applications. Progressive loss of material (wear) is a common failure that leads to hammermill fatigue due to cyclic stress posed on the hammers based on literature reviews. The mode of quenching and especially the discrepancy in the concentration affects the efficiency of the crushing unit. The fatigue performance of materials is being enhanced due to stress-relief heat treatment which makes it possible to increase the strength and ductility of the samples. However, the utilization of experimental model and simulation approach for stress prediction for the study is further recommended.

Thermal characterization of polyethersulfone composites filled with self lubricants

As of late, a lot of research has been performed on the thermal degradation of polymer matrix composites since this is a significant issue in the utilization of thermoplastic and thermoset polymers in various kinds of conditions that are exposed to temperature changes. These composite systems performance under various temperatures is a significant boundary to be considered on the grounds that it can, in many cases, decide the upper bound on the temperatures at which a material has reasonable properties. Relative motion between the two contact bodies always results in progressive loss of material from the less hardened surface by various modes of wear. Generally, Normal load establishing the contact, relative velocity, sliding distance and hardness of materials decide the amount of wear. In addition to these, temperature which arises due to friction at the interface of the contact surfaces significantly controls the wear. In order to consider the effect of contact temperature on the adhesive wear of polymeric composites, thermal parameters such as thermal conductivity, diffusivity and heat capacity are required. Therefore, in this work, the abovementioned thermal parameters were determined by flash method for short carbon fiber (SCF) reinforced polyethersulfone (PES) composites filled with two well known self lubricating materials, namely, potassium titanate whisker (PTW) and ultra high molecular weight polyethylene (UHMWPE). Thermal conductivity of SCF reinforced and PTW filled PES composites were improved whereas UHMWPE filled composites showed no significant change in their conductivity. In addition, numerical simulation was performed using the experimental results in Abaqus package. Simulated results were found aligned with experimentation results.

Wear Behaviour of Carbide Tool During Machining of Steel

Wear process takes predominant role in reducing the tool life during machining of steel. Tool wear is the progressive loss of material from the surface of the body of a tool. This occurs as a natural consequence when two surfaces with relative motion interact with each other. Challenges of wear mechanisms such as variation in chips, high pressure loads and spring back are responsible for tool wear. In addition the rate of tool wear depends on tool and work piece materials, tool shape, cutting fluids, process parameters (such as cutting speed, feed rate and depth of cut) and tool geometry and machine tool characteristics. The tool wear weight assesses real damage to the tool and is also based on blended wear of flank, crater, chip notching, primary and secondary grooving. This paper discusses the wear behavior of carbide tool utilizing response surface methodology. Machining tests were carried out by using EN-31 steel with tungsten carbide tools using soluble oil-water mixture lubricant under different machining variables. The study reveals that tool wear is mainly affected by cutting speed ,feed rate and tool nose radius whereas, depth of cut have negligible effect. However, response surface methodology combined with factorial design of experiments is a better alternative to the traditional one-variable- at –a-time approach for studying the effects of cutting variables on responses such as tool wear.

Design of a Testing Bench for Biomaterials Characterization According to Their Performance Under Tribocorrosion

The dynamic behavior of prosthetic devices and the existence of different types of aggressive environments, lead to consider the independent and synergic influence of mechanical and electrochemical disturbances during its operation, as they produce a progressive loss of material and finally a neglect of design requirements. In order to perform the needed tests for selecting materials depending of the minimum loss rate, it is necessary to build a device that allows implementing and supervising them in the three environments, due to the lack of standardized testing equipment and methods for biomedical researches. This paper describes the design methodology for a linear reciprocating Ball-on-Flat tribometer prototype, following the international standards and design criteria set by QFD, giving priority to manufacturing and assembling ease, low cost and structural stiffness (validated by means of finite elements analysis at a CAD software).

Molecular wear of microtubules propelled by surface-adhered kinesins.

Wear is the progressive loss of material from a body caused by contact and relative movement and is a major concern in both engineering and biology. Advances in nanotechnology have allowed the origins of wear processes to be studied at the atomic and molecular scale, but also demand that wear in nanoscale systems can be predicted and controlled. Biomolecular systems can undergo a range of active movements at the nanoscale, which are enabled by the transduction of chemical energy into mechanical work by polymerization processes and motor proteins. The active movements are accompanied by dissipative processes that can be conceptually understood as 'protein friction'. Here, we show that wear also occurs in an in vitro system consisting of microtubules gliding across a surface coated with kinesin-1 motor proteins, and that energetic considerations suggest a molecule-by-molecule removal of tubulin proteins. The rates of removal show a complex dependence on sliding velocity and kinesin density, which, in contrast to the friction behaviour between microtubules and kinesin-8, cannot be explained by simple chemical reaction kinetics.

The relationship between wear and dissipated energy in sliding systems

Wear is the progressive loss of material from the operating surface of a body occurring as a result of relative motion at the surface, while friction is the main means of controlling the input of energy in a system. The tribosystem approach proposes analysing the contact on both the material and the energetic planes, but the relationships between the different planes are not well established. In this paper, the basis of the energetic approach is discussed and the application of the model to experimental studies on bulk materials reveals a promising and powerful tool to analyse experimental results and to use in the mechanical design.

A nucleation-elongation mechanism for the self-assembly of side polar sheets of smooth muscle myosin.

Self-assembled filaments of smooth muscle myosin were observed by low dose electron microscopy to be flat side-polar sheets, in which the component molecules appeared straight and close-packed. Fraying experiments released small oligomers, in which molecules were staggered in parallel by about +/- 14 nm relative to two immediate neighbours, and were bound also to an antiparallel partner via a approximately 14 nm overlap at the very tip of the tail. We suggest a filament model which preserves these packing relationships. Adding stoichiometric amounts of MgATP to the filaments caused them to disassemble completely by progressive loss of material from their ends, at a limiting rate equivalent to about 2 monomers per second per end in physiological saline. The rate of the competing association reaction varied linearly with the monomer concentration, as determined in pressure-jump experiments. This suggests that myosin monomers, rather than dimers or higher oligomers, are the building blocks of these filaments. Shearing and annealing of assembled filaments appeared negligible on a time scale of a few hours. In consequence, filament number and filament length were dependent on the rate at which monomers were supplied to the assembly reaction, and on the number of filaments already present at the start of the assembly reaction.

The effects of drug and water incorporation upon some physical properties of cold cured acrylic.

The addition of drugs to the cold cured acrylics has been demonstrated to variably affect their mechanical properties. This study investigated the effects, to the mechanical properties of a cold cured denture base material, of the addition of drugs and water. Chlorhexidine acetate was incorporated into the denture reline material at 10% w/w in the polymer phase of the material. Specimens also contained 10, 20, or 30% water w/w in the monomer phase of the material with or without the drug. The hardness of the specimens decreased with the addition of water to drug containing or drug-free specimens. Furthermore, there was a significant reduction in the modulus of elasticity of the material with the addition of drugs and water or water alone, which was progressive as the amount of water increased. The load at fracture was similarly reduced as the water incorporation increased. The results demonstrated the considerable effects drug and water incorporation had upon the material. However, this would not negate the use of the material in the oral cavity in the reline or rebase situation employing existing prostheses. Moreover, the reduction in material strength may have the advantage of progressive loss of material with a resulting improved release pattern of the contained drug.