Search

Surface wear is the main reason for the breaking failure of the wire rope in service, particularly in the multi-layer winding hoist system of a coal mine. Understanding the effect of wear scars on the failure and mechanical properties of the rope is the effective way to ensure the safety of multi-layer winding hoist. In this paper, the breaking failure characteristics of hoist ropes with different wear scars were investigated by the breaking tensile test. The temperature rise in the wear scar regions was obtained and analyzed. Additionally, the finite element method was used to simulate the mechanical properties of the wear-out strands subjected to tensile load. Results show that the severe plastic deformation and obvious temperature rise occur in the wear scar region. The temperature rise curves during the breaking tensile test can reflect the number and the order of the fractured strands. The wear-out outer wires fracture earlier than the internal wires, and the wires with irregular wear scar always fracture along the sliding wear direction at the location with the maximum wear depth. Additionally, the wear scar caused by left cross contact will cause stress concentration and uneven distribution, and the wear depth makes it more obvious.

Fretting wear among steel wires is one of the important factors for the wire rope fracture. The influence of the wire diameter and crossing angle on the fretting fatigue behaviors of steel wires under tensile-torsional coupling force was explored in the present study. The test principles and analysis methods were introduced. Result shows that the variation laws of the coefficient of friction (CoF) between steel wires with increasing crossing angle under different wire diameter contacts are the same. For the same crossing angle, the CoF under different test conditions increases in the following sequence: both with the diameter of 0.8 mm

Wear is one of the primary factors for the degradation of the wire rope used for multi-layer winding hoist. It decreases the carrying capacity and service life of the hoisting rope, which will affect the mine safety directly. In this paper, the effects of the wear scars caused by sliding friction under different crossing angles and cross directions on the mechanical response of the wire rope were investigated through the breaking tensile test. Additionally, the fracture failure mechanism of the rope samples was discussed. Results show that the surface wear decreases the breaking force of the wire rope. The distribution of wear region and the maximum wear depth of the wear scar are the major influence factors on the mechanical properties of the rope. The variation range of the breaking force is larger for the rope with the wear scar under the sliding condition of right cross contact and the damage is more serious for that in the condition of left cross contact. There is obvious plastic deformation and temperature rise near the wear scar before the rope breaks. The fracture failure mechanism is ductile fracture with necking and dimples on the surface.

The mineral particles in the mine air aggravate the wear of wire rope, which seriously threatens the lifespan of wire rope. Therefore, the wear test of steel wires with helical structure was performed by a homemade tester. Results show that the coefficient of friction (CoF) curve under the original grease condition presents a slight increasing trend, while the CoF decreases with increasing the cycles after adding ore particles. For the grease mixed with ore particles, as the loading force increases, the wear volume of steel wire increases, while the wear coefficient shows a decreasing trend. The wear mechanism of steel wire under the original grease condition shows obvious abrasive wear and fatigue wear, while the wear mechanism under the mixed grease condition includes abrasive wear, adhesive wear and fatigue wear. Additionally, the wear characteristics of the peak friction pair are more obvious and severe than that of the valley friction pair under the mixed grease condition.

The suspended mineral particles in the mine aggravate the wear of hoisting wire rope and seriously threaten the mine safety. In order to explore the effect of different mineral particles on the fretting behavior between steel wires, the wear test of steel wires under different contact forms was performed by a homemade tester. Results show that the coefficient of friction between steel wires decreases with increasing the concentrations of mineral particles (coal particles and ore particles). The wear coefficient of steel wire decreases with the increase of the coal particle concentration, while for the grease mixed with ore particles, the wear coefficient presents the opposite change rule. Compared with the original grease and the grease mixed with coal particles, the wear scars of steel wire under the grease mixed with ore particles condition show more serious furrows, micro cracks and pits. The wear mechanisms of steel wire lubricated by the grease mixed with different mineral particles are abrasive wear, adhesive wear and fatigue wear.

Friction and wear behavior exists between hoisting ropes that are wound around the drums of a multi-layer winding hoist. It decreases the service life of ropes and threatens mine safety. In this research, a series of experiments were conducted using a self-made test rig to study the effects of the strand lay direction and crossing angle on the winding rope's tribological behavior. Results show that the friction coefficient in the steady-state period shows a decreasing tendency with an increase of the crossing angle in both cross directions, but the variation range is different under different cross directions. Using thermal imaging, the high temperature regions always distribute along the strand lay direction in the gap between adjacent strands, as the cross direction is the same with the strand lay direction (right cross contact). Additionally, the temperature rise in the steady-state increases with the increase of the crossing angle in both cross directions. The differences of the wear scar morphology are obvious under different cross directions, especially for the large crossing angle tests. In the case of right cross, the variation range of wear mass loss is larger than that in left cross. The damage that forms on the wear surface is mainly ploughing, pits, plastic deformation, and fatigue fracture. The major wear mechanisms are adhesive wear, and abrasive and fatigue wear.

Rail end quenching temperature field calculation is quenched in the process of simulation of organization transformation and distribution of the foundation, the calculation for quality directly affects the organization field. As much as possible in order to make the temperature field of simulation accord with the facts, this chapter will give full consideration to the influence of the phase change latent heat on temperature field of heavy rail, under different heating time by comparing the different heavy rail track the hardening layer depth, it is concluded that heavy rail of the induction heating 40 s conform to the requirements of the project, made a theoretical support to practical production.

A new class of Epoxy Emulsion modified Engineered Cementitious Composite (EM-ECC) has been developed for enhanced pipeline protection. The performance of typical ECC materials, such as flexural strength, anti-corrosion and early strength, has been improved by the addition of epoxy emulsion and rapid hardening cement. Our results indicated that the flexural strength of as-made EM-ECC increases with the increase of the EM/cement ratio after curing for 28 days. The retention rate of flexural strength of specimens remains analogical after immersed in water, 5 wt% Na2SO4and 5 wt% NaCl solutions, respectively. The flexural strength reached ca. 16 MPa at 60 wt% replacement rate of rapid hardening cement after curing for 3 days. This new class of EM-ECC will shed light to the design of new applications for the oil and gas industry.

An engineered cementitious composite (ECC) is a micromechanically based designed high-performance fiber-reinforced cementitious composite with high ductility and durability, represented by strain-hardening behavior in uniaxial tension. However, the setting time of ECC is retarded and early strength is decreased due to the presence of high volume of fly ash (HVFA). Therefore, shortening the setting time and increasing flexural strength of HVFA-ECC will be of obvious economic importance. The experimental study on setting time and flexural strength of HVFA-ECC proved that the setting time can be shortened by adding alkali accelerator and the optimum content is 4.0%, while the flexural strength of HVFA-ECC can be increased by applying fine particles fly ash, modified fly ash or adding exciting agent of fly ash.

Friction and wear seriously affect the safety use of winding hoist wire rope and the damage is a gradual process in practical application. In this paper, the tribological properties of a wire rope under different sliding distances were investigated. The evolutions of the coefficient of friction (COF), temperature rise, and wear characteristics under different contact loads and strokes were analyzed by a series of experiments. The results show that fluctuation of the friction is large in the early stages (before 10 min) and the major peaks depend on the stroke. When the contact load is 150 N, the COF increases most rapidly. It grows from approximately 0.48 to approximately 0.61 with the sliding distance. Additionally, the temperature rise in the wear region is higher under the large stroke (30 mm) and contact load (150 N). The maximum temperature rises are approximately 7.5 °C and 7.1 °C, respectively. Furthermore, it is approximately after 7200 mm that the temperature rise reaches a relatively stable stage. The wear scar region increases with the sliding distance and the maximum wear loss is approximately 65.5 mg at a load of 150 N. The major wear mechanisms of the wire rope are fatigue and adhesion wear.

Nickel-based self-fluxing alloys (SFA) have been widely used as coatings in the light of their high levels of wear and corrosion resistance. However, their resistance to wear can be substantially improved by reinforcement with tungsten carbide–cobalt hardmetals. In this work, a range of coatings based on a nickel-based self-fluxing alloy has been produced by laser cladding. The coatings have been reinforced with both conventional and nanostructured WC–Co at a single level of 30 wt.%. The effect of ceria as a grain refiner has also been examined. The sliding wear behaviour of the coatings was examined in a block on ring apparatus and the temperature of the samples measured during the wear tests. In all cases, the addition of WC–Co to the base alloy resulted in a significant increase in wear resistance, with wear rates of the reinforced deposits being less than 10% of that of the unreinforced deposit. The coating reinforced with a mixture of conventional and nanostructured WC–Co exhibited the lowest rates of wear. The addition of ceria was shown to significantly refine the microstructure of the deposit; however, little change was observed in the wear behaviour of the resulting material.

The reasonable design of the temporary support of the continuous girder bridge is a safe guarantee for the smooth closing. According to the characteristics of temporary support of the closed section, the corresponding calculation method is put forward, and then several kinds of temporary support locking devices colmmonly used in engineering practice are discussed. Based on the engineering example, the paper discusses the selection and design of the temporary support form of the construction of the continuous girder bridge. The results show that the transition of the structural system has great influence on the temporary supporting force, and it is feasible to use the external rigid support when the long - span continuous girder bridge decouples the temporary fixed bearing restraint.