Advanced Materials Research Vol. 871

Abstract: Detailed knowledge of particle-scale energy allocation behavior under the influence of particle breakage is of fundamental importance to the development of micromechanics-based constitutive models of sands. This paper reports original results of the energy input/dissipation of an idealized crushable soil using 3D DEM simulations. Particle breakage is modeled as the disintegration of synthetic agglomerate particles which are made up of parallel-bonded elementary spheres. Simulation results show that the initial specimen density and crushability strongly affect the energy allocation of the soil both at small and large strains. The major role of particle breakage, which itself only dissipates a negligible amount of input energy, is found to advance the soil fabric change and promote the interparticle friction dissipation. Particularly, at small strains, particle breakage disrupts the strain energy buildup and thus reduces the mobilized shear strength and dilatancy of a granular soil. At large strains where particle breakage is greatly reduced, a steady energy dissipation by interparticle friction and mechanical damping is observed. Furthermore, it is found that shear bands develop in most dense crushable specimens at large strains, but they are only weakly correlated to the anisotropy of the accumulated friction dissipation.

Abstract: The deformable behavior of ideal granular material under external loading, especially in monotonic condition, has always been of keen interest to geotechnical engineers. Earlier researchers have reproduced the fundamental stress-strain-dilation relationships at macro scale by distinct element method (DEM). Particle shape and servo controlled boundary are always assumed to be in regular and rigid conditions. In this paper, the elongated particles are prepared for generating loose and dense consolidated specimen. Meanwhile, lateral flexible boundary is applied for simulatingthe visualizedshear band, where the confining stress is fixed at 50kPa for loading procedure. The evaluations of macro qualities or micro statistical indexes are presented for finding the characteristic states of Quasi-static shear deformation. The results indicate that the initial particles internal contact and spatial arrangement would govern the followed shearing behavior.

Abstract: Based on the traditional mechanical model of thin-walled straight beam, the paper makes a systematic analysis and research on the pre-twisted thin-walled beam finite element numerical model. Firstly, based on the geometric deformation differential relationship, the paper deduces the pre-twisted thin-walled beam Saint-Venant warping strain. According to traditional thin-walled straight beam finite element mechanical model, the paper establishes its finite element stiffness matrix considering the Saint-Venant warping deformations. Finally, by calculating the pre-twisted elliptical section beam example, and contrasting three-dimensional solid finite element using ANSYS, the comparative analysis results show that pre-twisted thin-walled beam element stiffness matrix considering Saint-Venant warping deformation has good accuracy.

Abstract: In this paper, we propose a class of hybrid difference schemes combining the central difference scheme and the midpoint upwind scheme on the Bakhvalov-Shishkin mesh for solving quasi-linear singularly perturbed convection-diffusion boundary value problems. Point-wise second-order convergence uniform in the perturbation is proved clearly by using the-stability. The numerical experiments support the schemes and the uniform second-order estimate.

Abstract: Finite element simulation technology was applied to the steady heat transfer and thermo-mechanical coupling analysis in order to investigate the influence of thermal load on stress intensity and sealing performance. An finite element heat transfer model of cylinder head joint assembly was set up, based on which the steady heat transfer analysis was performed subsequently by applying reasonable boundary conditions and loads. The influence on cylinder head sealing performance due to thermal field under the thermal stress conditions was evaluated by using the finite element method. The results showed that the thermal load increases the bolt tensile force and the gasket pressure, which help to improve the sealing performance. Compared to the mechanical load case, the thermo-mechanical stress of the liner and the cylinder head is obviously increased, so the thermal load is not neglectable when calculating the stress intensity of the cylinder head and the cylinder liner.

Abstract: The HTS-42 (High Temperature Solder) properties in the liquid state have been studied. The optimal operating conditions for the solder melt time-temperature treatment, used for producing amorphous ribbons having the specified service properties, are recommended based on the analysis of the anomalies properties and temperature polytherms shape. The subsequent thermal treatment of soldered joints is not shown appropriate for soldering homogeneous melts not hardened by age (precipitation) hardening. The strength of such products can be improved by increasing the contact joint area. The HTS-42 solder amorphous ribbons enable, as compared to the powder semi-finished product, reducing its consumption by 2-3 times, improving the carrying capacity of soldered constructions by 20-40 %, which makes the soldering practice resource saving and significantly improves the product reliability.

Abstract: The MMS-2B wear machine was used to study abrasion wear of work rolls in cold rolling by simulating emulsion cooling during the cold rolling process. The work roll materials used were 4%Cr, same as those in industrial production. The surface SEM scanning photographs were taken every 30 minutes until the friction experiment finished, and erosive appearance of emulsion on the work roll surface could be seen in the photos. The corrosive wear of the work roll surface is discussed. Findings show that the main causes of stress corrosion and pitting corrosion are uneven microstructure on the work roll surface and a large number of dislocation accumulations, which form microscopic cells. Water in steel rolling emulsion is the main conductive medium of electrochemistry reaction, and this intensifies the corrosive wear.

Abstract: The purpose of the studies presented in this paper was to improve cutting properties of tool made of powder metal high-speed steel due to controlling the conditions of friction on contact areas of edgetools at cutting temperatures. Control of friction was carried out on the basis of alloying steel with 5% aluminum oxide (Al₂O₃), introducing 2% additive agent BN, and that allowed forming stable high-strength secondary structures, significantly extending the intervals of material self-organization. The use of both variants in alloying steel with 20% additive agent TiCN allowed significantly increasing lifetime of tool made of powder metal high-speed steel.

Abstract: The problem of increasing performance of carbide too lin machining hard-to-machine materials has been studied. Composite material was developed comprising carbide with heat-resistant bond Co-Re, significantly increasing resistance of carbide to thermoplastic deformation, and nanodispersed multilayer composite coating, significantly reducing thermomechanical impact on cutting part of tool.Studies to find the performance of tool made of developed composite material in turning hardened steel40H and heat-resistant nickel alloy HN77TYUR have shown its superiority compared to commercial carbides with coatings of modern generation.Studies have found out practicability of using VRK-13 cobalt-rhenium carbides with reduced content of expensive rhenium from 9% (weight) Re to 6% (weight), and it is highly competitive by heat resistance with VRK-15 carbide and is significantly superior to it by its strength.Results of cutting properties research forultra-dispersed Re-added WC-Co-carbides with Ti-TiN-TiCrAlNnano-dispersed multilayer composite coating are presented at longitudinal turning of constructional steels and hard-to-machine alloys. It is shown that the combination of ultra-dispersedheat-resistant WC-(Co,Re)-carbides and wear-resistant Ti-TiN-TiCrAlN coatings increase cutting properties of tool in some times.

Abstract: The effect of hydrothermal activation indifferent temperature and pressure conditions on the pozzolanic activity of waste glass powder was discussed. The waste glass powder was treated at 108°C, 0.15MPa, 116°C, 0.18MPa and 121°C, 0.2MPa for 2h in an autoclave respectively after milling to 4215cm2/g. Mortar was made with untreated and hydrothermal activated waste glass power replacement of cement at 20% respectively, then tested for compressive strength at 3, 7, 14 , 28 and 90 days. Results showed that compressive strength of cement mortar had varying degrees of decline when replacing cement with untreated waste glass powder, comparing to the control one. Decline amplitude was large at early age and small at late age. Activity of waste glass powder was significantly improved after hydrothermal treatment. Compressive strength of mortar improved as temperature and pressure elevated, obtaining optimal strength at 121°C, 0.2MPa. Compressive strength of mortar with hydrothermal activated glass powder was higher than that with untreated glass powder at all age with 20% cement replacement. Compressive strength increased 5.3% ~ 13.6% at 3 d, 6.8%~9.7% at 28 d, 9.7% ~ 17.7% at 90 d. The essence of hydrothermal activation was the corrosion of water in the glass.