Load-carrying Layer Research Articles

Environmentally adaptive lubrication enabled by gradient structure design of TiN-MoS2/Ti

Molybdenum disulfide (MoS2) films have been widely employed as lubricants for mechanical components but continue to face significant engineering challenges including their low hardness, high humidity sensitivity and weak adhesion to substrates. Although the co-deposition of MoS2 with additives provides enhanced functionality in some cases, the weak adhesion of MoS2 to the substrate is the key to the localized delamination or even early failure of the film. Herein, a novel MoS2-based film is designed and fabricated by magnetron sputtering deposition technique, which consists of Ti bonding layer, TiN load-carrying layer, TiN/Ti/MoS2 gradient layer, and top layer of Ti-doped MoS2 lubricating film. Results demonstrate that the rationally gradient design not only improves the adhesion strength between MoS2 and substrate, but also promotes the preferential growth of MoS2 along [001] zone axis perpendicular to the (002) crystal plane. The 3.2 at.% Ti-doped MoS2 film exhibits a low friction coefficient and wear rate before and after salt spray test, which is ascribed to the formation of a continuous and dense MoS2 tribofilm. Additionally, Ti additive can preferentially absorb oxygen in air, thereby preserving the self-lubricating ability of MoS2. This novel structure design provides an example for obtaining functional lubricants with good mechanical properties and environmental adaptability.

Mechanical Properties of the Materials Making up the Conveyor Belt Structure

Belt conveyors, equipped with belts designed for transporting materials and finished products are used in many industries. They allow to transport delicate items, for example made of glass, heavy products, such as canned food products and lightweight items, such as cardboard boxes. For this reason, the conveyor belts must, besides transferring power, ensure adequate conditions of transport for the conveyed materials without compromising the service life of the belt. Homogenous belts may not be capable of meeting all these requirements at a time. Composite belts, composed of the load-bearing layers and covering materials adhered thereon with the purpose to modify the surface properties, can be an option of choice in such cases. The described experiments were carried out on the respective materials making up composite belt joints as part of the research efforts related to the PhD thesis on adhesive bonding of composite belting materials. The strength tests were carried out on dumbbell-shaped specimens that were prepared from the load-carrying layer of synchronous polyurethane belting, the facing materials, namely polyamide fabric and polyurethane foam and the polyurethane adhesive used to join these layers. The differences in the parameters describing the surface properties, i.e. hardness and roughness were also checked. The experimental results were used to determine the material and strength properties of the components and the resulting differences were analysed.

ПРОЕКТИРОВАНИЕ МНОГОСТЕНОЧНЫХ КОМПОЗИТНЫХ ОБОЛОЧЕК

This paper investigates a problem of optimal design of a multi-walled cylindrical shell under axial compressive loads. The multi-walled shell consists of two load-carrying layers connected by a set of composite walls. The main structural element of the load-carrying layer is a monolayer comprising parallel-laid fibers that are interconnected by a polymer binder – a matrix. The wall represents a unidirectional composite made from the same material as the load- carrying layers. Both strength and stability constraints are taken into account during mathematical modeling. The critical load corresponding to a general form of buckling is determined by a classical formula for an orthotropic shell with “reduced” stiffnesses. The critical load corresponding to a local form of buckling is calculated using the well-known formula for a smooth orthotropic plate. The target function is the mass of the structure. The solution to the problem of optimal design of a multi-walled structure is proved to be unique. The conditions ensuring the existence of the problem solution are formulated. The example of evaluating the efficiency of reinforcing elements in a shell structure is given. The presented research results can find application in design problems for modern composite structures in rocket and space industry.

A tri-layer thin film containing graphene oxide to protect zinc substrates from wear

Due to its excellent properties, Zn alloy is widely used in daily life. However, the poor wear-resisting properties of Zn alloys limits their application. In this paper, a tri-layer thin film consisting of 3-aminopropyltriethoxysilane (APS), graphene oxide (GO) and perfluoropolyethers (PFPE) were successfully prepared on the surface of Zn alloy to improve the wear-resisting properties. The as-prepared tri-layer thin films were characterized by atomic force microscopy, Raman spectroscopy, x-ray photoelectron spectroscopy and contact angle measurement. In addition, the tribological properties of the as-prepared tri-layer thin films were studied on a ball-on-plate tribometer and the morphologies of worn surfaces were observed using 3D noncontact interferometric microscope. Compared with the control samples, the tri-layer thin films showed excellent friction-reducing and wear-resisting properties, which was attributed to the synergistic effect of the GO as the load-carrying layer and the PFPE as the lubricating layer.

Increase of load bearing capacity of a square-form nanofilter

Square-form, multi-layered nanofilter membranes have been investigated experimentally and by numerical simulation to determine their load bearing capacity versus filtration ability. The effect of various topologies combining the thickness of a load-carrying layer and Si-reinforcement on the bursting pressure has been determined. Based upon the comparison of a performance index an optimal structure could be selected for later production.

Stress-Strain State of a Cylindrical Sandwich Shell in an Axisymmetric Temperature Field Inhomogeneous across the Thickness

Exact analytical solutions to the problems on the formation of an axisymmetric stress-strain state (SSS) in a circular cylindrical sandwich shell under the action of a temperature field inhomogeneous across its thickness are obtained. It is assumed that the end cross sections of the upper load-carrying layer are immobile in the axial direction, whereas those of the lower load-carrying layer are free. By virtue of the small relative thickness, the outer layers are assumed momentless. The transversely soft filler has an arbitrary thickness, and its SSS is described by equations of thermoelasticity simplified according to the model accepted for it. The boundary conditions stated for the transverse (radial) direction at shell ends correspond either to a free edge or to the presence of a diaphragm.

Long-Term Durability of Glass-Fiber-Reinforced Composites under Operation in Pulp and Reactant Pipelines

Composite pipes 215 mm in diameter with a 6-mm wall, 3-mm functional layer, and ±60° glass-fiber-reinforced plastic (GFRP) layers were examined by means of microstructural analysis and mechanical testing. Three types of pipes were considered: unused, after a five-year operation at a pressure of 0.6 MPa and temperature of 70°C, and after a five-year operation at 0.6 MPa and 20°C. The GFRP load-carrying layer and the interfaces were investigated by a metallographic optical microscope, a computerized microscanning equipment, and a software image processing package. The initial and accumulated damages in the microstructure of the composite and interfaces were examined. The mechanical properties of the pipes after a long-term operation were examined on two-layer specimens in three-point bending. The stiffness and strength characteristics were measured in the axial and circumferential directions under tensile and compressive loads at elevated temperatures. Composite pipes, 8 m in length and 215 mm in diameter, were simulated numerically as shells of revolution. The shell model was corrected by a refined Timoshenko theory and a dual-modulus temperature-dependent model of stiffness for the multilayer composite structure. The strength margin of the composite pipes was determined based on real strength properties.

Stability of a Circular Sandwich Ring under an Axially Symmetric Temperature Field Inhomogeneous across the Thickness

The linearized problems on the stability of a circular sandwich ring of symmetric structure under an axially symmetric temperature field inhomogeneous across the core thickness are stated and analytical solutions to them are given. The first problem deals with the mixed flexural buckling form (BF) of the ring as a whole, realized as a result of buckling in one of the load-carrying layers due to formation of precritical pressure stresses in the layer. The second problem considers purely shear BFs when one load-carrying layer is rotated relative to the other. The deformation processes for the load-carrying layers are described by the Kirchhoff-Love model, and for the core of arbitrary thickness - by two models, namely by the equations of the plane problem of elasticity theory and by the model of a transversely soft layer of arbitrary thickness (the same equations simplified by the assumption of zero circumferential normal stresses). Within the frames of the first model adopted for the core, the shear BF is theoretically possible but practically unrealizable, since the mixed flexural BF arises earlier than the shear BF.

Mechanical and tribological properties of vapour deposited low friction coatings on Ni plated substrates

Soft steel and aluminium substrates with load-carrying layers of electroplated nickel were coated with commercially available low friction vapour deposited coatings. The mechanical and tribological properties of the coating and substrate composites were evaluated with special emphasis on the influence of the nickel layer. Two different thicknesses of the intermediate load-carrying nickel layer were tested. The samples were evaluated regarding friction and sliding wear, abrasive wear, hardness and elastic modulus, morphology and coating thickness and adhesion between substrate and coating. It was found that all the evaluated low friction coatings were possible to be successfully deposited on the intermediate nickel layer. A relatively thick intermediate nickel layer is a promising candidate for improvement of the load-carrying capacity.

An experimental method for evaluation of the load-carrying capacity of coated aluminium: the influence of coating stiffness, hardness and thickness

If a brittle ceramic PVD coating is applied to a soft and compliant material such as aluminium, it might crack when the component is taken into use, i.e. when it is loaded. This means that the load-carrying capacity of the soft Al substrate has to be improved if a PVD coating should be applied successfully. One solution is to introduce a relatively thick intermediate load-carrying layer between the soft substrate and the thin ceramic PVD coating. This paper presents a new experimental test method to find the load-carrying layer thickness required to protect a soft substrate from plastic deformation. The method is evaluated, but also used to investigate different load-carrying layers on aluminium. In the experiment, rigid cemented carbide balls were used to indent aluminium coated with, compared with PVD coatings, relatively thick (50–150 μm) foils. The foils were firmly attached to the aluminium substrates using a fusible and strong adhesive. After indentation the foil/coating was detached and the amount of plastic deformation on the substrate surface was determined by measuring the depth of the residual indent. The influence of foil thickness, stiffness and hardness on the resistance to plastic substrate deformation was studied. It was found that the technique of gluing foils on Al well simulates the load-carrying properties of a traditionally deposited layer. The indentation experiments also showed that the load-carrying capacity of the coated aluminium increases with the thickness of the foil and the elastic modulus of the foil. No significant influence of the foil/coating hardness on the load-carrying capacity could be seen.

Biplastic pipes for high-pressure oil pipeline systems

A high-performance, corrosion-resistant biplastic pipe for high-pressure oil pipeline systems is presented. The pipe combines an outer load-carrying layer formed from unidirectionally glass-reinforced plastic (GRP) sublayers by wet multi-circuit winding and an inner sealing layer of high-density polyethylene. Both demountable and permanent joints, tees, and other parts are constructed for these pipes. The biplastic pipes ensure reliable operation of oil pipeline systems under a pressure of up to 200 bar. The experimental results and calculated estimates of the strength of biplastic pipes are presented. The results of using these pipes in oil pipeline systems in the Perm’ region are discussed.

Effect of the Thermosensitivity and Reinforcement Structure on the Load-Carrying Capacity of Metal-Composite Gas-Turbine Disks

The direct problem of calculating three-layered reinforced rotating disks with account of thermosensitivity of their substructural elements is formulated. Based on this problem and a strength criterion for the substructural elements of the disk, the inverse problem on determining its load-carrying capacity at a given profile of the disk and reinforcement structure of the load-carrying layer is stated. The calculation results for a magnesium-steel disk with a fixed geometry and different reinforcement structures are presented. It is shown that the thermosensitivity of the substructural elements lowers considerably the load-carrying capacity at elevated temperatures. The isotropic steel and quasi-isotropic reinforced disks, most often used in practice, are inefficient compared with spirally and radially reinforced ones; for magnesium-steel disks, the best are the structures with a radial and radially circumferential reinforcement.

Dynamic strength of spherical fiberglass shells under internal explosive loading

In this article, we determined experimentally the response and made an estimate of the strength of fiberglass spherical shells,500 mm in diameter of two types of winding under radial-symmetric internal explosive loading. The advantage of shells with a more uniform thickness (15–20mm) of the load-carrying fiberglass layer is shown. On explosion of a charge involving an energy equivalent to1.4 kg ofTNT, this layer has an approximately twofold strength factor. It is established that the change from uniaxial (cylindrical shells) to biaxial strain in spherical shells does not change the magnitude of total strain at failure.

Stress-strain state of the boundary-layer type in three-layer shells made of composite materials

The investigation of the nonaxisymmetric stress--strain state of three-layer cylindrical constructions has been reduced in [i] by means of semimomentum-free hypotheses to the solution of a differential equation of the fourth order, in which the transversal shears of the filler are taken into account parametrically. This equation describes the basic stress state and does not take into account the local effects near the fracture lines, due to stress transfer from one load-carrying layer to the other through the filler. The basic solution describes satisfactorily the shifts of the shell [2], but, as the analysis of real constructions has shown, it can lead to errors in the determination of bending and shear deformations. The present article investigates the nonaxisymmetric stress-strain state of three-layer shells with account of a quickly changing solution of the boundary-layer type.