• Nuclear Engineering and Technology
• /
• v.52 no.7
• /
• pp.1486-1494
• /
• 2020

To evaluate transport-induced cladding embrittlement after interim-dry storage, ring compression tests were carried out at room temperature(RT) and 135 ℃. The ring compression test specimens were prepared by simulating the interim-dry storage conditions that include four peak cladding temperatures of 250, 300, 350 and 400 ℃, two tensile hoop stresses of 80 and 100 MPa, two hydrogen contents of 250 and 500 wt.ppm-H and a cooling rate of 0.3 ℃/min. Radial hydride fractions of the ring specimens vary depending on those interim-dry storage conditions. The RT compression tests generated lower offset strains than the 135 ℃ ones. In addition, the RT and 135 ℃ compression tests indicate that a higher peak cladding temperature, a higher tensile hoop stress and the lower hydrogen content generated a lower offset strain. Based on the embrittlement criterion of 2.0% offset strain, an allowable peak temperature during the interim-dry storage may be proposed to be less than 350 ℃ under the tensile hoop stress of 80 MPa at the terminal cool-down temperature of 135 ℃.

• Journal of Mechanical Science and Technology
• /
• v.14 no.5
• /
• pp.483-489
• /
• 2000

The purpose of this work is to investigate fatigue damage of quasi-isotropic laminates under tensile loading in different directions. Low cycle fatigue tests of $[0/-60/60]_s$ laminates and $[30/-30/90]_s$ laminates were carried out. Material systems used are AS4/Epoxy and AS4/PEEK. The fatigue damage of $[30/-30/90]_s$ is very different from that of $[0/-60/60]_s$. The experimental results are compared with the result obtained from the method for determining strain energy release rate components proposed by the authors. The analytical results were in good agreement with the experimental results. It is proved that the failure criterion based on the strain energy release rate is an appropriate approach to predict the initiation and growth of delaminations under cyclic loading.

• Transactions of Materials Processing
• /
• v.21 no.4
• /
• pp.258-264
• /
• 2012

The forming failure of AZ31 alloy sheet during deep drawing processes was predicted by the FEM and ductile fracture criteria. Uniaxial tensile tests of round-notched specimens and FE simulations were performed to calculate the critical damage values for three ductile fracture criteria. The critical damage values for each criterion were expressed as a function of strain rate at various temperatures. In order to determine the best criterion for failure prediction, Erichsen cupping test under isothermal conditions at $250^{\circ}C$ were conducted. Based on the plastic deformation histories obtained from the FE analysis of the Erichsen cupping tests and the critical damage value curves, the initiation time and location of fracture were predicted under bi-axial tension deformation. The results indicate that the Cockcroft-Latham criterion had good agreement with the experimental data. In addition, the FE analysis combined with the criterion was applied to another deep drawing process using an irregular shaped blank and these additional results were verified with experimental tests.

• Computers and Concrete
• /
• v.16 no.2
• /
• pp.209-222
• /
• 2015

This paper presents results of biaxial compressive tests and strength criterion on two replacement percentages of recycled coarse aggregate (RPRCA) by mass for plain structural recycled aggregate concrete (RAC) at all kinds of stress ratios. The failure mode characteristic of specimens and the direction of the cracks were observed and described. The two principally static strengths in the corresponding stress state were measured. The influence of the stress ratios on the biaxial strengths of RAC was also analyzed. The experimental results showed that the ratios of the biaxial compressive strength ${\sigma}_{3f}$ to the corresponding uniaxial compressive strength $f_c$ for the two RAC are higher than that of the conventional concrete (CC), and dependent on the replacement percentages of recycled coarse aggregate, stress states and stress ratios; however, the differences of tensile-compressive ratios for the two RAC and CC are smaller. On this basis, a new failure criterion with the stress ratios is proposed for plain RAC under biaxial compressive stress states. It provides the experimental and theoretical foundations for strength analysis of RAC structures subject to complex loads.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.32 no.6
• /
• pp.488-495
• /
• 2008

In order to achieve long fatigue lifetimes for cyclically pressurized thick cylinders, multi-layered compound cylinder has been proposed. Such compound cylinder involves a shrink-fit procedure incorporating a monobloc tube which has previously undergone autofrettage. The basic autofrettage theory assumes elastic-perfectly plastic behaviour. Because of the Bauschinger effect and strain-hardening, most materials do not display elastic-perfectly plastic properties and consequently various autofrettage mo dels are based on different simplified material strain-hardening models, which is assumed that combination of linear strain-hardenig and power strain-hardening model. This approach gives a more accurate prediction than the elastic-perfectly plastic model and is suitable for different strain-hardening materials. In this paper, a general autofrettage model that incorporates the material strain-hardening relationship and the Bauschinger effect, based upon the actual tensile-compressive stress-strain curve of a material was proposed. The model was obtained using the von Mises yield criterion and plane strain condition. The tensile-compressive stress-strain curve was obtained by experiment. The parameters needed in the model were determined by fitting the actual tensile-compressive curve of the material. Finally, strain- hardening model was compared with elastic-perfectly plastic model.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.20 no.5
• /
• pp.1543-1551
• /
• 1996

The static tensile load bearing capability of as adhesively-bonded tubular single lap jint that is calculated usign the linear mechanical properties of adhesive is usually far from the experimentally determined because the majority of the load transfer of the adhesively-bonded jointd is accomplished by the nonlinear behavior of the rubber-toughened eoxy adhesive. In this paper, both the nonlinear mechanical properties and the fabrication residual thermal stresses of adhesive were included in the calculation of the stresses of adhesively-bonded joints. The onlinear tensile properties of adhesive were approximated by an exponential form which was represented by the initial tensile modulus and ultimate tensile stength of adhesive. The stress distribution in the adhesive were calculated by applying the load obtained from the tensile tests. From the tensile tests and the stress analysis of adhesively-bonded hoints, the failure model for adhesively-bonded tubular single lap joints was proposed.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.14 no.4
• /
• pp.134-139
• /
• 2015

PolyJet technology is an additive manufacturing (AM) technology commonly used for modeling, prototyping, and production applications. It is one of the techniques used for 3D printing. The PolyJet technique is a process that joins materials to fabricate a product from 3D CAD data in a layer-by-layer manner. The orientation of a layer can affect the mechanical properties of the product manufactured by the PolyJet technique because of its anisotropy. In this paper, tensile and shearing tests of specimens were developed with the PolyJet technique in order to study the mechanical properties according to the orientation of a layer. The mechanical properties of the specimens were determined on the basis of true stress-strain curves from tensile and shearing tests. In addition, the tensile and shearing tests were simulated under the same conditions as those of experiment, and the experiment and simulated results were compared. Through this study, the fracture criteria could be established.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2009.05a
• /
• pp.158-163
• /
• 2009

Titanium alloy sheets have excellent specific strength and corrosion resistance as well as good performance at high temperature. Recently, titanium alloys are widely employed not only aerospace parts but also bio prothesis and motorcycle. However, due to the low formability and large spring back at room temperature, titanium alloy sheets were usually formed by slow forming or hot forming with heating die and specimen. In the sheet metal forming area, FE simulation technique to optimize forming process is widely used. To achieve high accuracy FE simulation results, Identification of material properties and deformation characteristic such as yield function are very important. In this study, uniaxial tensile and biaxial tensile test of Ti-6Al-4V alloy sheet with thickness of 1.0mm were performed at elevated temperature of 873k. Biaxial tensile tests with cruciform specimen were performed until the specimen was breakdown to characterize the yield locus of Ti-6Al-4V alloy sheet. The experimental results for yield locus are compared with the theoretical predictions based on Von Mises, Hill, Logan-Hosford, and Balat's model. Among these Logan-Hosford's yield criterion well predicts the experimental results.

• Geomechanics and Engineering
• /
• v.13 no.6
• /
• pp.1045-1055
• /
• 2017

Tensile strength is considered key properties for characterizing rock material in engineering project. It is determined by direct and indirect methods. Point load test is a useful testing method to estimate the tensile strengths of rocks. In this paper, the effects of rock shape on the point load index of gypsum are investigated by PFC2D simulation. For PFC simulating, initially calibration of PFC was performed with respect to the Brazilian experimental data to ensure the conformity of the simulated numerical models response. In second step, nineteen models with different shape were prepared and tested under point load test. According to the obtained results, as the size of the models increases, the point load strength index increases. It is also found that the shape of particles has no major effect on its tensile strength. Our findings show that the dominant failure pattern for numerical models is breaking the model into two pieces. Also a criterion was rendered numerically for determination of tensile strength of gypsum. The proposed criteria were cross checked with the results of experimental point load test.

• Steel and Composite Structures
• /
• v.15 no.2
• /
• pp.203-220
• /
• 2013

The study of the tensile strength of composite materials is far more complex than analysis of the properties of elasticity and plasticity. Indeed, during mechanical loading, micro-cracks in the matrix, the fibers break, debonding of the interfaces are created. The failure process of composites is of great diversity and cannot be described if even we know: the strength criterion of each individual component, the state of stress and strain in the material, the propagation phenomena cracks in the structure and nature of the interface between the matrix and the reinforcement. This information is only partially known and the obtained by the analysis of a stress limit beyond which there is destruction of the material is almost impossible. To partially process the issue, a solution lies in a mesoscopic approach of seeking a law to locate the ultimate strength of the material for a plane stress state. Tests on rectangular plates in bending PEEK/APC2 and T300/914 three were made and this in order to validate our approach, the calculation has been implemented in a nonlinear finite element code (Castem 2000), in order to make comparison with the numerical results. The results show good agreement between numerical simulation and the two materials; however, it would be interesting to consider other phenomena in the criterion.