This study aims to investigate the fatigue behaviour and determine the fatigue life prediction under biaxial loading. Fatigue tests were performed according to ASTM 2207-02 and the values of tensile stresses are selected from the ultimate tensile strength which is 0.5 Su, 0.6 Su, 0.7 Su, 0.8 Su and 0.9 Su, while the torsion angle representing the shear stresses acting was set at 15 degrees. The biaxial fatigue test was conducted using a combination of two types of stresses acting on the same frequency, namely 1 Hz, on smooth specimens made from medium carbon steel. The biaxial fatigue lives of the specimens are recorded when the specimen has completely fractured. The results indicate that the observed fatigue lives are in good agreement with the predicted lives by using the Coffin-Manson, Morrow, and Smith-Watson-Topper strain-based models. Mohr's circle approach was used to determine the maximum shear stress and principal normal stress. The maximum shear stress increased from 457 MPa to 486 MPa with the increment of principal normal stress from 612 MPa to 767 MPa. The principal stresses, maximum shear stresses, and energy dissipated were used to explain and describe the behaviour of biaxial fatigue. Both stresses are inversely proportional to the fatigue life. Meanwhile, the energy is linearly proportional to the stress applied, where the values increase in the range 500 kJ/m 3 to 605 kJ/m 3. Thus, the basic understanding of the material behaviour may be used in the processes of declaring component service lives and the fatigue life prediction of a particular automotive component. Therefore, the cost incurred can be reduced for the development process in material engineering.
Clay bricks are commonly used for building wall. One of the functions of a wall is to create a habitable internal environment, such as enabling internal temperature to be controlled at a human comfort level (~24°C) which is lower than the outside temperature for hot and humid climate countries. Thus, it is important for clay bricks to minimize heat flow into the building to reduce the energy consumption by air-conditioning system. The aim of this paper is to investigate the reduction of heat flow through hollow clay bricks relative to solid bricks. Finite element method was used to simulate steady-state heat transfer through solid and hollow clay bricks. Several arrangements of cavities filled with air, wool and expanded foam were simulated. It was found that the effective thermal conductivity reached almost a constant when the void volume and reduction in cross-sectional area exceeds 10%. Generally, heat transfer through hollow clay brick is expected to be significantly lower than the solid clay brick. It can be concluded that building wall made from hollow clay bricks could reduce the energy consumption by its air conditioning system. Future work is on the transient heat flow analysis and evaluation of mechanical properties of hollow clay bricks.
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