Temperature-dependent proportional limit stress of SiC/SiC fiber-reinforced ceramic-matrix composites

In this paper, the temperature-dependent proportional limit stress (PLS) of SiC/SiC fiber-reinforced ceramic-matrix composites (CMCs) is investigated using the micromechanical approach. The PLS of SiC/SiC is predicted using an energy balance approach considering the effect of environment temperature. The relation between the environment temperature, PLS, and composite damage state is established. The effects of the fiber volume, interface properties, and matrix properties on the temperature-dependent PLS and composite damage state of SiC/SiC composite are analyzed. The experimental PLS and interface debonding length of 2D SiC/SiC composites with the PyC and BN interphase at elevated temperatures are predicted. The temperature-dependent PLS of SiC/SiC composite increases with the fiber volume, interface shear stress and interface debonding energy, and the matrix fracture energy and decreases with the interface frictional coefficient at the same temperature.

PENGARUH TEMPERATUR ANELING TERHADAP KEKERASAN DAN KEKUATAN PIPA TEMBAGA AC BEKAS

During the installation process, copper pipes for air conditioning will experience a very large deformation due to straightening and bending following the installation path. Hardening strains occur that result in changes in mechanical properties in this case decreases ductility making it difficult to do the connecting process with flaring. Studies need to be carried out to restore the mechanical properties of copper pipes that have been used, including the heat treatment process on copper pipes, so that used copper pipes have a better benefit value than having to be recycled. The temperature of the heat treatment is varied from 400oC, 500 oC and 600 oC. Tensile test results show that at annealed temperature of 400 oC has the highest tensile strength of 125.81 N / mm2 and proportional limit stress of 40.52 N / mm2. Whereas in the microhardness test, the highest hardness occurs also at annealed temperature of 400 oC which is equal to 50.8 HV.

Effect of Volume Element Geometry on Convergence to a Representative Volume

To accurately simulate fracture, it is necessary to account for small-scale randomness in the properties of a material. Apparent properties of statistical volume element (SVE) can be characterized below the scale of a representative volume element (RVE). Apparent properties cannot be defined uniquely for an SVE, in the manner that unique effective properties can be defined for an RVE. Both constitutive behavior and material strength properties in SVE must be statistically characterized. The geometrical partitioning method can be critically important in affecting the probability distributions of mesoscale material property parameters. Here, a Voronoi tessellation-based partitioning scheme is applied to generate SVE. Resulting material property distributions are compared with those from SVE generated by square partitioning. The proportional limit stress of the SVE is used to approximate SVE strength. Superposition of elastic results is used to obtain failure strength distributions from boundary conditions at variable angles of loading.

Mesoscale Material Strength Characterization for Use in Fracture Modeling

To accurately simulate fracture, it is necessary to account for small-scale randomness in the properties of a material. Apparent properties of Statistical Volume Elements (SVE), can be characterized below the scale of a Representative Volume Element (RVE). Apparent properties cannot be defined uniquely for an SVE, in the manner that unique effective properties can be defined for an RVE. Both constitutive behavior and material strength properties in SVE must be statistically characterized. The geometrical partitioning method can be critically important in affecting the probability distributions of mesoscale material property parameters. Here, a Voronoi tessellation based partitioning scheme is applied to generate SVE. Resulting material property distributions are compared with those from SVE generated by square partitioning. The proportional limit stress of the SVE is used to approximate SVE strength. Superposition of elastic results is used to obtain failure strength distributions from boundary conditions at variable angles of loading.

Measurment of bending properties of rhizophora tropical wood

The Young’s modulus, load at the yield point and proportional limit stress from the compression bending (cb) test were compared with the four point bending tests (4pb). The theoretical Young’s modulus are larger than the real reading for 5mm and 10mm thick specimens, except for 200mm long specimens due to specimen nonlinearity. The experimental results for the short specimens are slightly high compared to the theory due to uniaxial compression in both tensile and compressive planes. Since the additional deflection produced by the shearing force and the stress concentration at the loading point was smaller with the compression bending test compared to the conventional four point bending test the values of Ecb are larger than E4pb. It is noted that when length/thickness (l/t)>80, the values of Ecb are scattered. In addition, Ecb decrease sharply when l/t<30. In order to obtain a stable Young’s modulus value, it is suggested that the l/t should be 30~80.

MEASURMENT OF BENDING PROPERTIES OF RHIZOPHORA TROPICAL WOOD

The Young’s modulus, load at the yield point and proportional limit stress from the compression bending (cb) test were compared with the four point bending tests (4pb). The theoretical Young’s modulus are larger than the real reading for 5mm and 10mm thick specimens, except for 200mm long specimens due to specimen nonlinearity. The experimental results for the short specimens are slightly high compared to the theory due to uniaxial compression in both tensile and compressive planes. Since the additional deflection produced by the shearing force and the stress concentration at the loading point was smaller with the compression bending test compared to the conventional four point bending test the values of Ecb are larger than E4pb. It is noted that when length/thickness (l/t)>80, the values of Ecb are scattered. In addition, Ecb decrease sharply when l/t<30. In order to obtain a stable Young’s modulus value, it is suggested that the l/t should be 30~80.