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Vol 3 No 2 (2021)

  • Joining of Aluminum and Steel using AlSi12 Brazing Filler in a Protective Atmosphere Furnace: Microstructure and Mechanical Properties

    Yijun Man, Dayou Pan, Shibo Liu

    Brazing of pure aluminum (Al) to steel using an Al-12 wt. %Si (AlSi12) filler metal and an Al brazing flux was performed in furnace filled with protective atmosphere. Microstructure characterizations of the full/fractured joints, tensile shear strength and micro-hardness tests were performed on the samples with holding time from 5-30 min at brazing temperature of 600 °C and additional thermal exposure of 30 min at temperature of 480 °C. It is found that the joint seam for all samples features roughly into four layers, among them, the layer adjacent to steel is an IMC layer and dominantly distributed with h phase. The tensile shear strength of joints is inversely proportional to the thickness of h phase layer and particularly governed by a specific zone which is located in the h phase layer, directly adjacent to the interface between h phase layer and steel and scattered with a lot of visible pores and cracks. Micro-hardness tests show the hardness of the h phase layer remains the highest for each holding time and increases with the increase of holding time. The higher hardness leads to the limited plasticity of the η phase and more fragile of this layer. Furthermore, great differences of hardness exist between the η phase layer and steel may also generate great stresses that induce the crack initiation in the specific zone and finally result in the failure of brazed joints.

  • Tape Casting Technique for Fabrication of Piezoelectric Ceramics and Other Multilayered Devices-A Review

    Prasanta Kumar Panda, Benudhar Sahoo

    Tape casting is a preferred technique for fabrication of micron sized thin sheets and multi-layered stacks. This technique can be used for all types of materials available in powder form. Therefore, this is a versatile technique used for fabrication of capacitors, piezoelectric multi-layered stacks, functional gradient materials, low temperature co-fired ceramics (LTCC) etc. involving all types of metals, ceramics and polymers. In this article, tape casting method is reviewed including the slurry preparation and role of various ingredients. This technique is widely used for fabrication of piezoelectric multi-layered stacks in order to reduce the “driving voltage” up to few volts for micro-meter sized thin layers. The preparation methodology of slurry making for tape casting and role of various ingredients are discussed in detail including multi-layered fabrication of devices. Typical tape casting examples of lead zirconate titanate (PZT) and barium strontium zirconate titanate (BSZT) lead free piezo materials are also presented. Various application of tape casting in recent years has been reviewed.

  • Experimental Study and Numerical Simulation Analysis of Geosynthetics Reinforced Bond Performance

    Pandu Praveen

    The test of bond performance of civil composite reinforcement is usually carried out by consolidation drainage triaxial shear test, which involves three aspects: the stress, strength and volume change of cohesive soil. If we want to increase the volume stability of the high-pressure compaction soil, we need to increase the way of reinforcement, but through the way of reinforcement, the shear swelling body of the soil will be reduced, while the shear shrinkage body of the soil will not be reduced or increased. The test pieces used in the experiment are reinforced specimen and plain soil specimen. The biggest difference between them is the axial strain. When the axial strain is low, the reinforced specimen is lower than the strength of plain soil specimen, and the plain soil specimen is slowly higher than the reinforced specimen, which requires the axial strain to increase to a certain extent, which also has the phenomenon that the reinforcement delays the soil strength, which also depends on the number of reinforcement layers and tension of the reinforcement materials with the increase of modulus of elongation, the phenomenon of delay will be more obvious. The peak strength of the soil is controlled by changing the number of layers of reinforcement and the tensile modulus of reinforcement. It shows that with the increase of the number of layers of reinforcement, the peak strength of the soil is increased in a certain range, but once the peak value is exceeded, the peak strength of the soil will not be greatly changed by changing the number of layers of reinforcement, except through by changing the number of reinforcement layers, the residual strength of soil can be controlled by changing the reinforcement material of tensile modulus, so that the stress-strain characteristics of soil will be greatly changed.

  • Research on the Application of Composite Materials in Building Reinforcement Engineering

    Mostafa Yadama

    The paper analyzes the development process and advantages of composite materials and finds that the use of composite materials in building reinforcement projects will have good application results. Then through experimental research, the application effects of glass fiber composite materials, carbon fiber composite materials and carbon fiber/glass fiber composite materials in building reinforcement engineering are analyzed. The experimental results show that: carbon fiber/glass fiber composite materials have better reinforcement effect; compared with carbon fiber composite materials, the cost of materials is lower.

  • Research on the Detection Countermeasures of Building Concrete Raw Materials

    Bogdan Gradinaru

    The quality of concrete directly determines the quality, service life and safety of the building, so it is necessary to use concrete materials of excellent quality and performance in the building construction process. In addition to the production process of concrete, which directly affects its performance, the influence of raw materials is very significant. Nowadays, the production process has become more standardised and mechanised, so special attention needs to be paid to the influence of raw materials in the process of making concrete.Based on this, the article will focus on the analysis of countermeasures for the testing of raw materials for construction concrete. By the testing of raw materials, the selection of more suitable raw materials for making concrete, helps to improve the strength and quality of the concrete.The article begins with an analysis of the key points of concrete raw material testing, analysing the considerations in the selection and testing of fly ash, water, stone, cement, sand and admixtures; then analyses several methods of testing raw materials for construction concrete, such as backfill method, ultra-deep rebound synthesis method, post-loading pull-out method and core drilling method, which have their own advantages and disadvantages and need to be selected reasonably according to the testing requirements; finally proposes a few measures to increase the quality of construction concrete.