Melting Erosion Research Articles

A tool for tillage in areas exposed to water erosion

Construction of a tool for the beardless ridge-coulisses tillage on sloping agricultural landscapes is given. The design of process of forming the ridge-stubbles coulisses, ensuring the reduction of melt water and erosion processes is described. New tool provides the high technological reliability during the tillage on various agricultural backgrounds when soil moisture in the plow layer is up to 25% and hardness is up to 3 MPa.

The Reaction between Alkali Vapor and the Theoretical Composition MgAl<sub>2</sub>O<sub>4</sub>

The theoretical composition was made from MgO-rich MgAl2O4 (MR66) and alumina powder. The static crucible method was used to study alkali-resistance of the block samples. It has been observed that alkali steam permeated into the hole and reacted with corundum particles that produced β-Al2O3 by means of XRD, SEM and EDS. It led to volume expansion, cracks and melting erosion of corundum particles. The specimen of the 32% content of MgO has good physical and chemical properties and excellent alkali erosion performance. So the specimen is suitable for oxy-fuel combustion for glass melting furnace.

The Resistance of SiC/Al Layered Composite to Ballistic Impacting

Ballistic impacting test has been conducted on laminated SiC/Al-Cu composite with three layers ceramic plates and metal multi-constrain, while the target sample was prepared through squeeze casting. The ballistic testing result showed that composite exhibited good structural integrity. Mass loss and length loss of projectile are 63.65% and 65.43% respectively, mainly resulted from abrasion of crushed ceramic particles and melting erosion itself. Multi-constrain of metal ensured to maximize the role of abrasion of crushed ceramic powder, in addition, the heat generated at instantaneous projectile-target contact led to partial corrosion on projectile. Subject to ballistic impacting, SiC ceramic was transgranularly fractured and crushed, metal lining was melt, deformed and destroyed, as well as the interface dissociation happened between ceramic and metal. These processes absorbed great kinetic energy of projectile, so as to stop the penetration of incident mass within the laminated structure. Layered composite failure was completed under synergistic effect of three fracture modes, including ceramic brittle fracture, interface debonding and metal fracture.

A Bond Graph Model of an Electromagnetic Launcher—Part 2: Simulation Results

An electromagnetic launcher (EML) or railgun is a complex dynamically coupled system, with interacting electric, magnetic, mechanical, and thermal subsystems. Part 1 of this paper formulated a bond graph model of an EML system, including power supply, dynamics of power cables, electric dynamics of armature and rails, magnetic containment of flux, electric contact resistance between sliding armature and rails, generation of forward longitudinal motion, transverse contact mechanics of armature sliding on rails, thermal analysis of armature heating, and model of armature melt wear and plasma erosion. Using state equations extracted from the Part 1 paper, numerical simulation results of the Institute of Advanced Technology's MCL EML are presented. Simulated are rail current, armature forward motions, armature-rail contact normal approach, armature and interface temperatures, and material loss. Results are compared to MCL shot 185. The results suggest interface temperatures of thousands of kelvins, which can exceed 15 000 K under certain conditions, and an armature-rail sliding contact separation due to accumulated melt erosion, consistent with transition.

Experience with bulk tungsten test-limiters under high heat loads: melting and melt layer propagation

The paper provides an overview of processes and underlying physics governing tungsten melt erosion in the fusion plasma environment. Experiments with three different bulk tungsten test-limiters were performed in TEXTOR: (i) thermally insulated solid plate fixed on a graphite roof-like limiter heated up by the plasma to the melting point, (ii) macro-brush of the ITER-relevant castellated structure and (iii) lamellae structure developed for the JET divertor. The main objectives were to determine the metal surface damage, the formation of the melt layer and its motion in the magnetic field. PHEMOBRID-3D and MEMOS-1.5D numerical codes were used to simulate the experiment with the roof-like test-limiter. Both experiments and simulation showed that the melting of tungsten can lead to a large material redistribution due to thermo-electron emission currents without ejection of molten material to the plasma.

Melt damage simulation of W-macrobrush and divertor gaps after multiple transient events in ITER

Tungsten in the form of macrobrush structure is foreseen as one of two candidate materials for the ITER divertor and dome. In ITER, even for moderate and weak ELMs when a thin shielding layer does not protect the armour surface from the dumped plasma, the main mechanisms of metallic target damage remain surface melting and melt motion erosion, which determines the lifetime of the plasma facing components. The melt erosion of W-macrobrush targets with different geometry of brush surface under the heat loads caused by weak ELMs is numerically investigated using the modified code MEMOS. The optimal angle of brush surface inclination that provides a minimum of surface roughness is estimated for given inclination angles of impacting plasma stream and given parameters of the macrobrush target. For multiple disruptions the damage of the dome gaps and the gaps between divertor cassettes caused by the radiation impact is estimated.

The EPQ Code System for Simulating the Thermal Response of Plasma-Facing Components to High-Energy Electron Impact

The generation of runaway electrons during a thermal plasma disruption is a concern for the safe and economical operation of a tokamak power system. Runaway electrons have high energy, 10 to 300 MeV, and may potentially cause extensive damage to plasma-facing components (PFCs) through large temperature increases, melting of metallic components, surface erosion, and possible burnout of coolant tubes. The EPQ code system was developed to simulate the thermal response of PFCs to a runaway electron impact. The EPQ code system consists of several parts: UNIX scripts that control the operation of an electron-photon Monte Carlo code to calculate the interaction of the runaway electrons with the plasma-facing materials; a finite difference code to calculate the thermal response, melting, and surface erosion of the materials; a code to process, scale, transform, and convert the electron Monte Carlo data to volumetric heating rates for use in the thermal code; and several minor and auxiliary codes for the manipulation and postprocessing of the data. The electron-photon Monte Carlo code used was Electron-Gamma-Shower (EGS), developed and maintained by the National Research Center of Canada. The Quick-Therm-Two-Dimensional-Nonlinear (QTTN) thermal code solves the two-dimensional cylindrical modified heat conduction equation using the Quickest third-order accurate and stable explicit finite difference method and is capable of tracking melting or surface erosion. The EPQ code system is validated using a series of analytical solutions and simulations of experiments. The verification of the QTTN thermal code with analytical solutions shows that the code with the Quickest method is better than 99.9% accurate. The benchmarking of the EPQ code system and QTTN versus experiments showed that QTTN’s erosion tracking method is accurate within 30% and that EPQ is able to predict the occurrence of melting within the proper time constraints. QTTN and EPQ are verified and validated as able to calculate the temperature distribution, phase change, and surface erosion successfully.