Surface Modification of Metallic Inserts for Enhancing Adhesion at the Metal–Polymer Interface

A combination of mechanical and chemical treatments was utilized to modify the surface textures of copper and duralumin inserts in order to enhance the adhesion at the metal–polymer interface and provide an adhesive joint with a high loadbearing capacity. Pretreatment of the surfaces with sandblasting was followed by etching with various chemical mixtures. The resulting surface textures were evaluated with a scanning electron microscope (SEM) and an optical confocal microscope. Surface geometry parameters (Sa, Sz, and Sdr) were measured and their relationships to the adhesion joint strength were studied. It was found that the virgin and purely mechanically treated inserts resulted in joints with poor loadbearing capacity, while a hundredfold (duralumin) and ninetyfold (copper) increase in the force to break was observed for some combinations of mechanical and chemical treatments. It was determined that the critical factor is overcoming a certain surface roughness threshold with the mechanical pretreatment to maximize the potential of the mechanical/chemical approach for the particular combination of material and etchant.

Improvement of load-bearing capacity of arched support using rolled steel reinforcement in mines

The economic efficiency of coal mining at the reduced cost is directly related with maintenance of operation conditions in temporary roadways. This article proposes a method of increasing the loadbearing capacity of the three-link arched support made of a special rolled profile (SRP) by increasing the stiffness moments of arched support sections subjected to the greatest bending moments. It is determined to be necessary to install the same size SPR in the support sections exposed to the greatest bending moments. Mathematical modeling of the reinforcement shows that the sufficient length of SRP segments is 30 cm. The calculations show that SRP 27 is replaceable by SRP 17 with the same size inserts, which allows saving of 10 kg of steel per each meter of the arched support. The proposed method of increasing the load-bearing capacity of the support will reduce the specific content of steel in the mine support manufacture and, thereby, will enable significant saving of material and labor resources. The studies conducted to substantiate the proposed solution include: determination of bending moments and normal forces in the three-link steel arched support by the computer-aided procedure of VNIMI (All Union Research Institute of Mining Geomechanics and Mine Surveying) for the specific existing conditions, with the subsequent choice of the required size of the support; stress–strain analysis of rock mass and mine support in ANSYS environment; economic calculation of the proposed solution effectiveness. The implemented researches give grounds to believe that the proposed variant of increasing the loadbearing capacity of the support made of the rolled steel profile can significantly improve stability of mine roadways. It is possible to strengthen the support without reducing the metal content in cases of expected deformation of the support under the influence of the confining pressure, when the other methods of maintenance-free support in roadways are ineffective or require a lot of time, materials and labor.

Synthesis and analysis of the spatial mechanism

Spatial mechanisms of various types are widely used in technology. Most of them have one or two ball pairs, the presence of which reduces the service life of the device (ball pairs are difficult to protect from dust and dirt. They are more difficult to manufacture and have a lower loadbearing capacity than rotational pairs). Replacing ball pairs with rotary ones, designed, for example, with standard bearings, will greatly simplify and reduce the cost of their manufacturing technology, increase the service life and expand the area of practical application. The difficulty and complexity of creating fivelink and six-link mechanisms and devices with a special structure lies in the fact that the usual combination of links fails to achieve their operability (with rotatable links). Theoretically, this mechanism has been studied by many foreign and Russian scientists. However, Kazan scientists were the first to form and put into practice spatial mechanisms with rotational pairs. The paper presents synthesis and analysis of the spatial five-link mechanism by the degree of irregularity, axial displacement, elliptical law and by the reproduction of a linear function. The mechanism provides intensification and energy saving of mixing, separation, torque transmission of various drives.

Road Design on Low Bearing Capacity Soils

Soil with weak bearing capacity, like peat and organic grounds, is widespread in Latvia. During the geotechnical investigation for road reconstruction projects, in many cases the discovered soils with low physical-mechanical properties are located below the existing road structure. It is a challenge for a road design engineer to find a way how to ensure road loadbearing capacity and prevent the occurrence of various deformations. Various methods and technologies for ground structure reinforcement and stabilization are being developed worldwide. During design of road structures, it is important to analyse the geotechnical situation and to identify the main reasons why deformations could occur in the ground layers under the road structure. Each of the developed technologies for weak and unstable soil reinforcement, stabilization is designed to solve a specific problem. Inaccurately and carelessly identifying the causes of problems, road deformations can affect the performance of the recently designed road and even make the existing problem worse. The aim of this paper is to show the soil strengthening methods used in Latvia and to analyse the benefits and disadvantages of these methods.

Improved ordering and lubricating properties using graphene in lamellar liquid crystals of Triton X-100/CnmimNTf2/H2O

The addition of a small amount of graphene into LLCs can increase the order of the amphiphilic molecules and the thickness of the amphiphilic bilayer, which could effectively reduce the friction coefficient and enhance the loadbearing capacity.

Method for optimizing the protecting pillars parameters in underground coal mining

A method for optimizing the protecting pillars parameters during the study of soft enclosing rocks (in Ukraine mines) is represented. The necessity of a differentiated approach has been substantiated when choosing the protecting pillar parameters based on the geomechanical factors analysis influencing the state of massif. Mining and geological situation was analysed. It has been studied a stress-strain state (SSS) along the protecting pillar width with account of the mined-out space on the basis of a computational experiment and is presented in the form of curves of vertical and horizontal stresses distribution, as well as stresses intensity distribution. The recommended engineering decisions have been substantiated and the SSS of fastening and security structures has been analysed. A certain reserve of the fastening structure loadbearing capacity as part of the frame support and the combined roof-bolting system has been revealed. An evidence base has been created for the measures development on conducting and maintaining mine workings in the zone of the stope works influence. The recommendations have been developed on the protecting pillar formation with a width of at least 40 – 45 m to exclude the stope works influence.

Reconstructing the Load-Bearing Capacity of Deteriorated, Concrete Airfield Pavements Using Prefabricated Slabs

The age of currently operated concrete airfield pavements in Poland exceeds 30 years operation period many times. Such a long working life of airfield pavements forced to search for the efficient and fast technologies of their reconstruction. The article described in detail the technologies of fast reconstruction of airfield concrete slabs using prefabricated slabs. The addressed technology guarantees the reconstruction and even the improvement of the condition of loadbearing capacity of mentioned airfield slabs which was confirmed during laboratory tests, field tests and practically verified in the real operation in the International Airport Kraków-Balice.