In the present study, a comparison of the thermal-insulation and mechanical performances of cement and heat-stabilized compressed earthen blocks (CEBs) was carried out to determine the factors which influence those properties. The raw clays used consist mainly of kaolinite, orthoclase and quartz. The mechanical strength increased with increase in both the amount of cement added and the firing temperature. However, the responses are better for cement-stabilized CEBs. The thermal insulation of fired bricks is greater than that of cement-stabilized bricks. This difference was related to the decrease in porosity and the formation of continuous-surface. The decrease in thermal insulation is mainly related to the formation of continuous-surface in cement-stabilized CEBs, whereas in the fired CEBs, it is due to the modification of pore volume. The mineralogy of the raw clays is statistically correlated to porosity and continuous-surface development that were confirmed as the main factors in the modification of both the mechanical strength and the thermal insulation. In cement-stabilization, the decrease in insulation is due to the development of continuous surface, while for heat-stabilization, mineral transformations during the sintering reduced continuous-surface formation and the insulation was controlled by both radiation and reduced surface conduction. The influence of the mineralogy of the raw material shows that clay content favours the insulation in fired bricks obtained at T ≤ 1000°C, while sand contents favour densification. In contrast, clay contents reduce the mechanical response of cement-stabilized material due to limited cement–clay interactions. In general, the mechanical response is more favourable in cement stabilization, while thermal insulation is better in fired bricks.

When a power module is under a continuous electrical load, a temperature effect is induced by the current load in the module configuration. The joint material therefore has long-term temperature and mechanical loadings under supplied power. A long-term temperature load can change the material and mechanical properties, including voiding, cracking, creeping and fracturing. Au/20Sn eutectic alloy, a highly temperature resistant material, is typically used for electric interconnections in high-power modules. The Au/20Sn is converted into AuSn and an Au5Sn intermetallic compound (IMC) by solid liquid inter-diffusion (SLID) bonding to form joints with high melting points. In this study, a test vehicle based on an actual power module was designed and fabricated to investigate and understand the material properties and mechanical behavior of Au/20Sn solder under a temperature load. The joint microstructure exhibited variation under different thermal treatment conditions such as temperature and load durations. The shear strength test was conducted to examine the mechanical strength of the joints under different thermal load conditions. The failure mode of the joint was further determined using fracture morphology after the shear test. Finally, the shear strength of Au/20Sn was identified to investigate the high temperature resistance of joints under different temperatures. The mechanical strengths of joints under different temperature loads are expressions of different mechanical characteristics and can be used to determine reliability at an intended high application temperature.

The effect of heating, to temperatures between 400 and 1200ºC, on the dehydroxylation of kaolin and the pozzolanic activity of the resulting amorphous material were determined by a variety of analytical techniques. Mixtures of concrete containing variable amounts of kaolin calcined at 700ºC were analysed and the results compared with those for concrete samples containing two different types of imported metakaolin. As shown in this work, Colombian kaolin can be used effectively as a raw material to obtain a highly active product (metakaolin). The optimum heating temperature for the kaolin is between 700 and 800ºC.

In recent years, the material Au-20Sn eutectic solder, which is resistant to high temperatures, is used for electric interconnections in high-power modules, the material properties such as temperature and strain rate dependent stress-strain curve are critically needed for reliability assessment of Au-20Sn solder joint. Thus, this study was performed to determine the material properties of Au-20Sn eutectic solder under various strain rates and temperature loads. Many researches using shear test to determine the shear resistance of solder joint, however, the mechanical strength as measured by the shear test is the maximum shear strength of the package joint, but this measurement does not represent the stress-strain behavior of Au-20Sn material. To identify the material properties of Au-20Sn eutectic solder, the tensile test was performed to measure its mechanical strength and nonlinear material properties. The strain rate effect was examined in terms of the influence of the mechanical strength on the Au-20Sn eutectic solder at different tensile rates. The temperature-dependent material properties of Au-20Sn solder were also measured under various thermal loadings, and material properties of Au-20Sn obtained in this research can be applied to the simulation model, the thermomechanical behavior and reliability of the power module can be further analyzed and evaluated.

We propose a new class of modular-robotic structures, intended to produce forces which scale with the number of modules. We adopt the concept of a spherical catom and extend it by a new connection type which is relatively strong but static. We examine analytically and numerically the mechanical properties of two collective-actuator designs. The simulations are based on the discrete element method (DEM), with friction and elastic deformations taken into account. One of the actuators is shown to generate forces proportional to its volume. This property seems necessary for building modular structures of useful strength and dimensions.