Polymorphic crystalline wetting layers on crystal surfaces

Analogous to surface premelting, we propose that a crystal surface can undergo a pre-solid-solid transition, i.e. developing a thin polymorphic crystalline layer before reaching the solid-solid transition temperature if two crystals can form a low-energy coherent interface. We confirm this in simulations and colloid experiments at single-particle resolution. The power-law increase of surface layer thickness is analogous to premelting. Different kinetics and reversibilities of surface-crystal growth are observed in various systems. Surface crystals exist not only under thermal equilibrium, but also during melting, crystallization, and grain coarsening. Furthermore, the premelting and pre-solid-solid transition can coexist, resulting double surface wetting layers. We hypothesize that such surface phenomena exist in atomic and molecular crystals, which provide a novel way to tune material properties.

Investigate Temperature Preheating on the Chill Plate to Identify Surface Characteristic on the Ductile Iron by Sand Casting

The chilled casting method is widely used in the metal casting industry to accelerate the mold's cooling rate. This method is very suitable for surface hardening by depositing the elements contained in the chill material onto the surface of the object being cast. One of the factors that influence surface hardness characteristics is the diffusion temperature. This study aims to determine the microhardness, surface layer thickness, and the element contained on the surface. The main material produced into Y-Block is ductile cast iron, the chill material is SS 304 plate with a thickness of 0.2mm. However, before the liquid material is poured into a mold, the chill plate is inserted into the surface of the pattern in the mold, then the plate was preheated. The result showed that the highest preheating temperature has produced microstructure around the surface area namely eutectic carbide of (FeCr)7C3, and (FeCr)3C. SEM-EDX analysis shows that 7.13%Cr is contained on the coating layer at a thickness of 0.020 mm and an average hardness of 700-900 HV.

The Effect of Surface Layer Thickness in a Wide-Area Simulation in Different Models: Susceptibility Mapping of Rainfall-Induced Landslide

In recent years, sediment disaster has frequently been caused by heavy rainfall and has cost many human lives and great property losses. To estimate such risks, Wakai et al. [1] proposed a simplified prediction method to calculate the variation of groundwater levels in natural slopes both at the time of rainfall in wide areas and in real time. To calculate the variation of groundwater levels using this method, the slope conditions (such as material constant and initial conditions) must be determined in advance. This study takes the 2017 heavy rainfall in Northern Kyushu as an example to analyze surface layer thickness, one of the slope conditions that most significantly influences slope stability, over wide areas. The findings reveal that the prediction of slope failure distribution differs depending on how the surface layer thickness and sliding surface are determined.

The impact of internal thermal regime of glaciers on climate caused advance and retreat

<p>Most glaciers in Sweden have polythermal temperature regimes, where a temperate core of ice is overlain by a cold surface layer. The cold surface layer prolongs the response time of a glacier, and therefore increases the time it takes for a glacier to start advancing during a cooling climate trend. In the late 1980s and 1990s, some glaciers in Sweden advanced due to prolonged periods of positive mass balance, for example Storglaciären. However, far from all glaciers advanced during this period, coincidentally relating to their cold surface layer thickness. This raises the question: what factors drive how and when a polythermal glacier advances, and what climatic signals can be read from traces of past advances and extents? Here, four polythermal glaciers are described in detail since the early 1900s, when they were close to, or at, their largest Holocene extents. These glaciers lie in relatively similar settings, and thus share many resemblances, but also show many differences. How these glaciers have changed since the early 1900s, how they look today, and what landforms they have left behind, provides an opportunity to explore factors behind their responses. The four studied glaciers are: Mikkaglaciären, Storglaciären, Rabots glaciär, and Mårmaglaciären. The dynamics of glaciers retreating are much better understood than glaciers advancing, as the overwhelming majority of existing data have been collected since the latter 1900s half, during a period of overall negative mass balance. The aim of the study is to describe the current properties of the studied glaciers. Using this knowledge and the landform assemblages in their glacier forefields, we suggest explanations to how they might have responded to climate change in the past and possible causes for differences in their response.</p>

Effects of the Face/Core Layer Ratio on the Mechanical Properties of 3D Printed Wood/Polylactic Acid (PLA) Green Biocomposite Panels with a Gyroid Core

Gyroid structured green biocomposites with different thickness face layers (0.5, 1, 2 and 2.5 mm) were additively manufactured from wood/ polylactic acid (PLA) filaments using a 3D printer. The mechanical properties of the composite panels, bending properties, compressive strength (parallel to the surface), Brinell hardness, and face screw withdrawal resistance, were determined. The surface layer thickness significantly affects the mechanical properties of the composite materials. As the surface layer thickness was increased from 0.5 to 2.5 mm, all the mechanical properties significantly improved. In particular, the Brinell hardness and face screw withdrawal resistance of the specimens improved sharply when the skin thickness was higher than 2 mm. The bending strength, bending modulus, compressive strength (parallel to the surface), Brinell hardness, and face screw withdrawal resistance of the specimens with a skin of 0.5 mm were found to be 8.10, 847.5, 3.52, 2.12 and 445 N, respectively, while they were found to be 65.8, 11.82, 2492.2, 14.62, 26 and 1475 N for the specimens with a 2.5 mm skin. Based on the findings from the present study, gyroid structured composites with a thickness of 2 mm or higher are recommended due to their better mechanical properties as compared to the composites with skins that are thinner.

Identification of surface-basement layer distribution of Wangi-Wangi Island based on HVSR method of microtremor data

<span class="jlqj4b"><span>To find out the distribution of the surface-basement layer of Wangi-Wangi Island, it can be done by calculating the surface layer thickness of each measurement point using microtremor data. The surface layer thickness (<em>h</em>) also indicates the position of the basement to the surface. The microtremor recording data used in this study were 47 data. Furthermore, the data were processed using the HVSR method to obtained the soil predominant frequencies which together with the <em>V</em>_s30 values were used to calculated the <em>h </em>values. The results showed that the thickness of the surface layer or sediment layer of Wangi-Wangi Island was in the range of 5.7339 to 241.2557 meters. Based on its distribution, the areas with a thick surface layer are in the areas of Sombu, North Wandoka, Wandoka, South Wandoka, Pada Raya Makmur and Wanci. In the case of a disaster, these areas are thought to have the most potential to experience damage if an earthquake shakes.</span></span>

THE INFLUENCE OF HYDRO BLASTING ON THE EN-DURANCE LIMIT OF SPECIMENS WITH A CUT UNDER BENDING AND STRETCHING-COMPRESSION

The hydro blasting influence on an endurance limit of cylindrical specimens with circular cuts of a semicircular profile of 0,3 mm radius under bending and stretching-compression in a case of symmetric cycle has been examined. Specimens of 10 mm diameter for fatigue tests were made of steels 30ХГСА, 12Х18Н10Т, ЭИ961,45 and aluminum alloys В93, Д16Т.The influence of surface hardening on an endurance limit of specimens with cuts was valuated by two criteria: residual stresses on the concentrator surface and the average integral residual stresses calculated through the part’s dangerous section surface layer thickness equal the critical depth of a non-propagating fatigue crack. On results of residual stresses and specimens with cuts endurance limits determination it’s been stated that coefficients of surface hardening influence on an endurance limit increase under bending and stretching-compression by two criteria are approximately equal. Besides, the coefficient of the influence by the average integral residual stresses criterion changes within essentially lesser limits than the coefficient of the influence by the residual stresses on the concentrator surface criterion. So the average integral residual stresses criterion should be used for the evaluation of a surface hardening influence on an endurance limit of parts with concentrators.On an example of specimens within and without peening in a dangerous section it’s been shown that peening doesn’t influence the endurance limit of a surface hardened part. The compressive residual stresses only influence the endurance limit of these parts.

THE ESTIMATION OF ROLLER STRENGTHENING INFLUENCE ON THE ENDURANCE LIMIT OF SHAFTS WITH PRESSURIZED HUB

The influence of roller strengthening on endurance limit under bending of the 25 mm and 50 mm diameter shafts made of steel 20 and 25 mm diameter shafts made of steel 40X with a pressurized hub has been examined. It’s been stated that the endurance limit of roller strengthened shafts with a pressurized hub depends not only on a value of compressive residual stresses in their dangerous section but on the character of its distribution. The valuation of a surface hardening influence on the endurance limit of shafts by the surface residual stresses criterion and the average integral residual stresses criterion has been shown that the average integral residual stresses criterion calculated through the part’s dangerous section surface layer thickness equal the critical depth of the non-propagating fatigue crack can be recommended for the hardened shafts with a pressurized hub endurance limit increase prediction. It’s been shown that on a diameter of a shaft with a pressurized hub raising it is necessary to increase a thickness of a hardened surface layer with compressive residual stresses.