Analysis of finishing performance in rotating magnetorheological honing process with the effect of particles motion

The particles used in magnetorheological polishing (MRP) fluid are the key components of the magnetorheological (MR) finishing processes. The rotational magnetorheological honing (R-MRH) process is recently developed as a highly productive MR finishing process which is used for finishing the internal surface of the industrial cylindric components. The involvement of micron-sized abrasive particles of MRP fluid in the finishing operation results in the invisible observation of the finishing mechanism which enables the urge of analyzing the motion of the particles during the present R-MRH process. Therefore, the effect of motions of the MRP-fluid’s particles is analyzed for nano-finishing performance on the inside surface of the cylindric workpieces. The motions performed by active abrasive particles on the inside surface of the rotating hollow cylindric workpiece cause a higher finishing rate. The effects of particle motions on the reduction in surface roughness and improvement in surface morphology confirm the usefulness of the R-MRH process. The surface finish with the effect of the particles' motions of the MRP-fluid in the R-MRH process on the stationary workpiece’s inner surface is achieved upto 100 nm from 420 nm of the initial ground surface in 60 min of finishing. Whereas, the same aforementioned surface of the rotating workpiece is finished upto 50 nm from the same initial ground surface in only 40 min of finishing with the effect of the particles' motions of the MRP-fluid. The improvement in the surface finish is also noticed through the scanning electron micrographs in this work. The significant change in surface finish obtained in experimentations confirms the integrity of the analytical study conducted for understanding the effects of motions of particles while finishing with the R-MRH process.

Numerical Analysis of a Novel Shaft Lining Structure in Coal Mines Consisting of Hybrid-Fiber-Reinforced Concrete

To address the temperature cracking of concrete in frozen shaft linings in extra-thick alluvial layers in coal mines, a novel shaft lining structure of coal mines consisting of hybrid-fiber-reinforced concrete (HFRC) was developed. Using the Finite Element Method (FEM), a numerical simulation test of the HFRC shaft lining structure with four factors and three levels was carried out, and the mechanical characteristics of the shaft lining structure were obtained. The results show that under a uniform surface load, the maximum hoop stress position of the HFRC shaft lining presents a transition trend from the inside surface to the outside surface; the hoop strain of shaft lining concrete is always a compressive strain, and the inside surface is greater than the outside surface. The empirical formula for the ultimate capacity of this new type of shaft lining structure was obtained by fitting. Compared with the model test results, the maximum relative error of the calculated value is only 6.69%, which provides a certain reference value for designing this kind of shaft lining structure.

Impact of the Design of Walls Made of Compressed Earth Blocks on the Thermal Comfort of Housing in Hot Climate

This study investigated the impact of the design of wall systems, mainly made of compressed earth blocks (CEB), on the indoor thermal comfort of naturally ventilated housing in hot climates of Burkina Faso. Conventional housing was modeled and calibrated using the WUFI® Plus dynamic simulation tool based on typical field surveys and the literature. This allowed testing the ability of different wall designs to impact thermal comfort. Thermal discomfort was assessed through an adaptive approach and was based on the annual weighted exceedance hours of overheating. Six designs of walls made of CEB and other locally available materials were simulated and compared to those made of classical hollow concrete blocks. The results of the simulation reveal that the profiles of thermal discomfort vary depending on the wall designs and building spaces. Thus, the wall made, from the outside toward the inside surface, of plywood of 2 cm, an insulation layer of 5 cm and a CEB layer of 29 cm thickness is the most suitable for an annual reduction in overheating for the living room. Regarding the bedroom, the most suitable wall is made of a 14 cm CEB layer, 5 cm insulating layer and 2 cm wood layer from the outside toward the inside surface.

Study on Interfacial Surface in Modified Spray Tower

This paper presents an analysis of the changes in interfacial surface and the size of droplets formed in a spray tower. The interfacial surface and the size of droplets formed are of fundamental importance to the performance of the equipment, both in terms of pressure drop and process efficiency. Liquid film and droplet sizes were measured using a microphotography technique. The confusors studied were classical, with profiled inside surface, and with double profiled inside surface. The liquids studied were water and aqueous solutions of high-molecular polyacrylamide (PAA) of power-law characteristics. The ranges of process Reynolds number studied were as follows: ReG ∈ (42,700; 113,000), ReL ∈ (170; 15,200). A dimensionless correlation for reduced Sauter mean diameter is proposed.

Thin-Wall Pipeline Repair: Evaluation of Reinforcement Systems and Internal Temperature Monitoring During Maintenance Procedures

There are many options available to pipeline operators when addressing anomalies or integrity threats. Repairing integrity threats requires an understanding of both the anomaly to be repaired, and the repair system itself. This can be challenging as pipeline repair systems come in a wide variety of materials, application techniques, and designs. Operators have similar challenges when performing maintenance activities on operating pipelines. Maintenance activities can take many different forms and often involve welding or other high temperature processes on the outside pipe surface. These processes can result in elevated temperatures on the inside surface of the pipeline and must be seriously considered before undertaking to ensure the safety of personnel performing the tasks and to protect the integrity of the pipeline. This study aimed to provide a greater understanding of pipeline reinforcement systems and maintenance activities as they relate specifically to thin-walled pipelines. To evaluate systems reinforcing thin-wall pipes, five different repair systems were investigated using 12.75-inch × 0.219-inch, Gr. X65 pipe that had been removed from service. The systems included a Type B steel sleeve, an epoxy-filled, interference fit, Type A steel sleeve, a hybrid steel sleeve-fiberglass based composite repair system, epoxy-filled oversized Type A steel sleeves, and a rigid coil, pre-cured, fiberglass-based composite repair system. Each system was used to reinforce a simulated 50% wall loss anomaly and was installed with the pipe samples maintained at an internal pressure equal to 33% of the pipe’s specified minimum yield strength (SMYS). The samples underwent pressure cycling and hydrostatic testing while strains in the simulated wall loss region were continually monitored. As a final step, the samples were burst tested. Monitoring of strain gages installed in the simulated wall loss anomaly allowed for comparisons to be made between the tested repair systems. It was observed that the recorded strain magnitudes and strain ranges were higher in some samples than others during testing. This allowed the systems to be ranked according to the recorded strains. Although differences were observed in the recorded strains, burst testing showed that all reinforcement systems were able to force failure to the base pipe outside of the simulated wall loss region. Maintenance procedures were also evaluated to identify those that could produce unacceptable temperatures on the inside surface of the thin-wall pipe. The maintenance procedures included installation of Type A steel sleeves (non-pressure containing), Type B steel sleeves (pressure containing), cad welds, and pin brazing cathodic protection (CP) test leads. Temperatures were monitored on the internal pipe surface using thermocouples and an infrared (IR) camera while the maintenance procedures were being performed. An internal surface temperature of 500 °F (260 °C) was set as the threshold for suitability. Monitoring of the Type B steel sleeve installation showed temperatures on the inside surface of the pipe that exceeded 1,200 °F (648 °C) when performing the circumferential weld at each end of the steel sleeve. A maximum temperature of 280 °F (137 °C) was recorded when making the longitudinal welds that included a backing strip. For the application being considered, this indicated that Type A steel sleeves (longitudinal welds only) could be installed within the required temperature limits. A maximum internal temperature of 936 °F (502 °C) was recorded during cad-welding. Pin-brazing was slightly lower, but also exceeded the 500 °F threshold. This testing confirmed that the installation of Type B steel sleeves, cad welding, or pin brazing should receive scrutiny before being performed on operating thin-wall pipelines.