Effect of surface treatment to inserted ring on Al–Fe bonding layer of aluminium piston with reinforced cast iron ring

In order to improve the bonding strength between piston alloys and cast iron ring of aluminum piston with reinforced cast iron ring,the different methods of the surface treatments(shot blasting and sand blasting) to the cast iron ring are experimented.The optical micrograph shows that an intermetallic layer and a ligulate shaped structure are formed between piston alloys and cast iron base ring.After sand blasting treatment,the ring surface is non-metal shiny,matte-like and has no obvious pits.The intermetallic layer thickness formed between piston alloys and cast iron is thinner and more equally distributed after sand blasting to the ring.The content of the graphite distributed the interfacial zone after the shot blasting treatment is little.With the increase of time by sand blasting,the hardness starts to slightly descend.The bonding strength of the sample by sand blasting is obviously higher than that by shot blasting and increases from 9.32 MPa to 19.53 MPa.

Investigations of Physical and Chemical Characteristics of Masonry Stones and Bricks during Building Cleaning： Part 1. Physical Testing

This series of study focused on analysing and assessing the changes of the physical and chemical characteristics of the surfaces of the masonrystones and bricks during the sandblasting cleaning process by conducting various physical and chemical tests. Seven masonry stones and bricks were adopted, including yellow sandstone, red sandstone, limestone, marble, granite, white clay brick and yellow clay brick. The physical testing included evaluating the cleaning degree, determining the Vickers hardness, and detecting the water absorption. Using a digital imaging analysis method, the greyscale and cleanness were introduced to quantitatively assess the effectiveness of masonry building cleaning and confirmed to be useful and appropriate. The cleanness analysis, together with the hardness and water absorption tests showed that a masonry stone or a brick with a higher cleaning degree corresponded to a brighter and harder stone surface. In general, the physical properties were found to vary largely during the building cleaning.

Investigations of Physical and Chemical Characteristics of Masonry Stones and Bricks during Building Cleaning： Part 2. Chemical Testing

This series of study focused on analysing and assessing the Changes of the physical and chemical characteristics of the stone surfaces during the sandblasting cleaning process by conducting various physical and chemical tests. Seven masonry stones and bricks were adopted, including yellow sandstone, red sandstone, limestone, marble, granite, white clay brick and yellow clay brick. The chemical investigations included the micrographing of the stone facade and the analysis of the chemical elements and compounds on four of the seven stones and bricks before and after the cleaning using the Scanning Electron Microscope （SEM） and Energy-Dispersive X-ray Spectroscopy （EDX） techniques. In general, the chemical properties were found to vary largely during the building cleaning. The chemical tests showed that the chemical elements and compounds on the stone facade significantly varied after long term exposures to the atmosphere, mainly due to the soiling on the building fagade caused by environmental erosion and weathering.

Sulfuric Acid Resistance of Concrete with Blast Furnace Slag Fine Aggregate

The deterioration of concrete by sulfuric acid attack in sewage environments has become a serious problem for many existing sewage structures. In this study, the properties of concrete using the blast furnace slag have been examined. It was shown that by using the blast furnace slag fine aggregate and blast furnace slag fine powder, it is possible to enhance the resistance of mortar and concrete to sulfuric acid. The resistance to sulfuric acid of mortar and concrete can be improved by using a blast-furnace slag fine aggregate in the total amount of fine aggregate. When mortar or concrete reacts to sulfuric acid, dihydrated gypsum film is formed around the particulate of the fine aggregate. This dihydrated gypsum film could retard the penetration of sulfuric acid, thus, improving the resistance to sulfuric acid. Furthermore, it has been proved that the relationship between the erosion depth by sulfuric acid attack and the product of immersion period and concentration of sulfuric acid can be expressed linearly. However, this relationship is dependent on the type of materials of concrete.

Dynamic response of ultralight all-metallic sandwich panel with 3D tube cellular core to shallow-buried explosives

The underbody of a vehicle system, either military or civil, is typically made of a relatively thin metallic plate, thus vulnerable to mine blast attacks. To improve the blast resistance, a multitude of protective structures have been proposed as attachments to the thin plate. In the present study, a novel ultralight all-metallic sandwich panel with three-dimensional(3D) tube cellular cores mounted to the vehicle underbody was envisioned as such a protective system. A metallic substrate(mimicking vehicle bottom)was placed above the proposed sandwich panel to construct a sandwich-substrate combinative structure. A series of sandwich panels having 3D tube cellular cores were fabricated via argon protected welding and laser welding. Mechanical responses of the combinative structure subjected to the denotation of 6 kg TNT explosives shallow-buried in dry sand were experimentally measured. Full numerical simulations with the method of finite elements(FE) were subsequently carried out to explore the physical mechanisms underlying the observed dynamic performance and quantify the effects of key geometrical parameters and connection conditions of the protective system. The performance of the proposed sandwich panel under shallow-buried explosives was also compared with competing sandwich constructions having equal mass. Finally, a preliminary optimal design of the 3D tube cellular core was carried out.

Particle Erosion Resistance of Bionic Samples Inspired from Skin Structure of Desert Lizard, Laudakin stoliczkana

In order to improve the particle erosion resistance of engineering surfaces, this paper proposed a bionic sample which is inspired from the skin structure of desert lizard, Laudakin stoliczkana. The bionic sample consists of a hard shell （aluminum） and a soft core （silicone rubber） which form a two-layer composite structure. The sand blast tests indicated that the bionic sample has better particle erosion resistance. In steady erosion period, the weight loss per unit time of the bionic sample is about 10% smaller than the contrast sample. The anti-erosion mechanism of the bionic sample was studied by single particle impact test. The results show that, after the impact, the kinetic energy of the particle is reduced by 56.5% on the bionic sample which is higher than that on the contrast sample （31.2%）. That means the bionic sample can partly convert the kinetic energy of the particle into the deformation energy of the silicone rubber layer, thus the erosion is reduced.