Modelling and Multi-objective Optimization of Elastic Abrasive Cutting of C45 and 42Cr4 Steels

Elastic abrasive cutting is a new high-performance method to produce workpieces made of materials of different hardness, which ensures lower wear of cut-off wheels and higher quality machined surfaces. However, the literature referring to elastic abrasive cutting is scarce; additional studies are thus needed. This paper proposes a new approach for modelling and optimizing the elastic abrasive cutting process, reflecting the specifics of its particular implementation. A generalized utility function has been chosen as an optimization parameter. It appears as a complex indicator characterizing the response variables of the elastic abrasive cutting process. The proposed approach has been applied to determine the optimum conditions of elastic abrasive cutting of С45 and 42Cr4 steels. To solve the optimization problem, a model of the generalized utility function reflecting the complex influence of the elastic abrasive cutting conditions has been developed. It is based on the findings of the complex study and modelling of the response variables of the elastic abrasive cutting process (cut-off wheel wear, time per cut, cut piece temperature, cut off wheel temperature and workpiece temperature) depending on the conditions of its implementation (compression force F exerted by the cut-off wheel on the workpiece, workpiece rotational frequency nw, cut off wheel diameter ds). By applying a genetic algorithm, the optimal conditions of elastic abrasive cutting of С45 and 42Cr4 steels: ds = 120 mm; F = 1 daN; nw = 63.7 min–1 and nw = 49.9 min–1, respectively for С45 and 42Cr4 steels, have been determined. They provide the best match between the response variables of the elastic abrasive cutting process.

Experience Study on Long-Life Microsurfacing with High Water Resistance Performance

Microsurfacing is a standard preventive maintenance technology developed on the basis of slurry sealing technology. However, the high temperature and rainy season in Guangdong Province affect its expanded application because of its low water resistance and short service life. So, high-performance microsurfacing, a new microsurfacing technology, has been developed. The key to this technique is an appropriate proportion of water-based epoxy resin and waterborne epoxy curing agent, which could generate a chemical reaction to form a high-performance bonding network structure of space. And indoor wet-wheel wear test shows that its antiwear ability and resistance to water damage are evidently increased (to over 50%) compared with the conventional microsurfacing. Furthermore, from the long-term road performance results, the antisliding and water resistance performance of high-performance microsurfacing is much higher than the conventional technique.

On the Grinding Performance of Alumina Wheels in Ultrasonic Vibration-Assisted Grinding of Hardened GCr15 Steel

Composite manufacturing with multiple energy fields is an important source of processing technology innovation. In this work, comparative experiments on the conventional grinding (CG) and ultrasonic vibration-assisted grinding (UVAG) of hardened GCr15 steel were conducted with WA wheel. The grinding wheel wear patterns and chips were characterized. In addition, grinding force, force ratio, and ground surface quality were investigated to evaluate wheel performance. Results illustrate that the interaction between abrasive grains and workpiece in UVAG process has the characteristics of high frequency and discontinuity. The wear property of abrasive grains is changed and the grinding force is decreased because the generation of micro-fracture in abrasive grains improves the grinding wheel self-sharpening. Better surface quality is obtained, the surface roughness is reduced by up to 18.96%, and the number of defects on the machined surface is reduced through the superior reciprocating ironing of UVAG. Accordingly, WA wheel performance is improved by UVAG.

Mechanical Wear Contact between the Wheel and Rail on a Turnout with Variable Stiffness

The operation and maintenance of railroad turnouts for rail vehicle traffic moving at speeds from 200 km/h to 350 km/h significantly differ from the processes of track operation without turnouts, curves, and crossings. Intensive wear of the railroad turnout components (switch blade, retaining rods, rails, and cross-brace) occurs. The movement of a rail vehicle on a switch causes high-dynamic impact, including vertical, normal, and lateral forces. This causes intensive rail and wheel wear. This paper presents the wear of rails and of the needle in a railroad turnout on a straight track. Geometrical irregularities of the track and the generation of vertical and normal forces occurring at the point of contact of the wheel with turnout elements are additionally considered in this study. To analyse the causes of rail wear in turnouts, selected technical–operational parameters were assumed, such as the type of rail vehicle, the type of turnout, and the maximum allowable axle load. The wear process of turnout elements (along its length) and wheel wear is presented. An important element, considering the occurrence of large vertical and normal forces affecting wear and tear, was the adoption of variable track stiffness along the switch. This stiffness is assumed according to the results of measurements on the real track. The wear processes were determined by using the work of Kalker and Chudzikiewicz as a basis. This paper presents results from simulation studies of wear and wear coefficients for different speeds. Wear results were compared with nominal rail and wheel shapes. Finally, conclusions from the tests are formulated.

Development of the Fog Seal Layer Characterized by Durability in Terms of Skid Resistance

In this paper, based on the thermosetting properties, bonding performance, high-temperature water damage resistance, and aging resistance properties of epoxy-emulsified asphalt, the best formulation of epoxy emulsified asphalt as a skid resistance fog sealing asphalt is studied. Through accelerated wheel wear and other tests, the effects of the ratio of the amount of skid resistance particles to the amount of epoxy emulsified asphalt, the total amount of skid resistance fog seal asphalt, and the construction process on the skid resistance durability of the skid resistance fog seal were studied. The results show that the epoxy emulsified asphalt formula code A80 (E2) (emulsified asphalt : water-based epoxy = 80 : 20) is the best formula; when the proportion of emery and epoxy emulsified asphalt is 1 : 1, the British Pendulum Number (BPN) reduction rate of the skid resistance fog seal-test piece worn 100,000 times was 27.4%. Compared with the same period, the reduction rate was reduced by 4.6% on average, with the smallest mass loss rate and the best skid resistance durability. When the total amount of skid resistance fog seal asphalt is 1.2 kg/m2, the BPN reduction rate of the skid resistance fog seal specimen worn 100,000 times was 27.4%, which is an average reduction of 5.8% over the same period, and the mass loss rate is the smallest, and the skid resistance durability optimal. When using the premixed process, the BPN of the specimen was reduced by 13.2% after abrasion of 100,000 times. Compared with the “one asphalt and one sand” and “double asphalt and one sand” molded specimens, the mass loss rate was reduced by 15.0%, 4eU&7.2%, showing the best skid resistance performance. The results can provide guidance for the design and construction of AC-13 and other pavement skid resistance fog seals.