Sharif Digital Repository

Thermal cracking is the prevalent type of distress experienced by asphalt pavements in cold regions. It is widely assumed that when thermal stresses induced in the pavement exceed the tensile strength of the asphalt surface layer, cracking occurs; however, the role of thermal fatigue should not be ignored. To better describe the low-temperature (LT) performance properties of modified asphalt binders, a new parameter, normalised tensile stress (NTS), was defined in this research. NTS values were compared with bending beam rheometer (BBR), direct tension (DT) and semi-circular bending (SCB) fracture test results. The m-value parameter of the BBR test specifies the type of asphalt binder. This... 

The critical strain energy release rate for crack initiation, J ci , was measured under mode I loading for SAC305 solder joints between two copper substrates. Fracture tests were performed using double cantilever beam specimens at a strain rate of 0.03 s −1 . Different bond-line widths (i.e., joint size in the out-of-plane dimension) and thicknesses, were examined. The fracture force per unit width and J ci (the average value of four J-integral contours encircling the crack tip) were relatively insensitive to the width of the joint ranging from 8 mm to 21 mm. Variations in bond-line thickness (i.e., 150 μm, 250 μm and 450 μm) also had an insignificant influence on the fracture energy of... 

The critical strain energy release rate for crack initiation, J ci , was measured under mode I loading for SAC305 solder joints between two copper substrates. Fracture tests were performed using double cantilever beam specimens at a strain rate of 0.03 s −1 . Different bond-line widths (i.e., joint size in the out-of-plane dimension) and thicknesses, were examined. The fracture force per unit width and J ci (the average value of four J-integral contours encircling the crack tip) were relatively insensitive to the width of the joint ranging from 8 mm to 21 mm. Variations in bond-line thickness (i.e., 150 μm, 250 μm and 450 μm) also had an insignificant influence on the fracture energy of... 

Steel plate shear walls (SPSWs) have shown a desirable performance in experimental studies and past earthquakes. The advantages of the SPSW and its good performance against lateral loads persuade designers to utilize the system in their practical projects. Some important aspects of the SPSW have remained unknown in spite of valuable experimental and numerical studies. One of these unknown characteristics is the effect of cracks on the SPSW behavior. Several experimental studies have reported fracture in SPSW due to crack propagation during testing, but the experimental studies have not investigated the crack effect. Due to low thickness of steel plate and inherence of crack, the crack... 

A new test specimen for a tensile test of industrial graphite is introduced using experiment and finite element results. The most influencing factors on the tensile strength of the test specimens are considered and the number of tests, which are necessary to optimize the tensile strengths are reduced based on the design of experiment using the Taguchi method and the effects of all factors on strength of test samples are studied. Comparison of the predicted strengths based on the Taguchi approach with the measured experimental results and finite element analysis shows a good correlation between them. In addition, results show that the new introduced specimen makes a 33% increase in the... 

The present work developed a mixed-mode cohesive zone model (CZM) with a mode I failure criterion to predict the delamination bending loads of multilayer, composite printed circuit boards (PCBs) assembled with soldered ball grid array (BGA) components that were reinforced with an underfill epoxy adhesive. Two different delamination modes were observed in these microelectronic assemblies: delamination at the interface between the solder mask and the first conducting layer of the PCB, and PCB subsurface delamination at the interface between the epoxy and glass fibers of one of the prepreg layers. The cohesive parameters for each of the two crack paths were obtained from fracture tests of... 

The present work developed a mixed-mode cohesive zone model (CZM) with a mode I failure criterion to predict the delamination bending loads of multilayer, composite printed circuit boards (PCBs) assembled with soldered ball grid array (BGA) components that were reinforced with an underfill epoxy adhesive. Two different delamination modes were observed in these microelectronic assemblies: delamination at the interface between the solder mask and the first conducting layer of the PCB, and PCB subsurface delamination at the interface between the epoxy and glass fibers of one of the prepreg layers. The cohesive parameters for each of the two crack paths were obtained from fracture tests of... 

A procedure based on the linear amplitude sweep (LAS) test has been developed to determine the optimum rejuvenator content for restoring the properties of aged asphalt binders. The LAS test was employed to assess the damage tolerance, fatigue resistance, and fracture behavior of rejuvenated aged binders. In case of fracture analysis, a crack-based indicator to govern the stable crack propagation was defined to characterize fracture resistance of asphalt binders. While rejuvenators improved all of these properties, higher contents were required to restore the cracking behavior of the original binder. The linear relationship between the integrated damage-fatigue-fracture indicator and... 

Fracture tests on Sn93Pb37 solder joints in a double cantilever beam (DCB) configuration were performed at two different strain rates of 10−5 and 0.03 s−1 under mode I loading conditions. In each case, the critical strain energy release rate for crack initiation, Jci, was obtained. Effects of storing specimens at a constant temperature of 75 °C and cyclic temperature varying between 32 and 75 °C were examined at these strain rates. In the strain rate of 0.03 s−1, storing samples in a constant or cyclic temperature caused the fracture energy to decrease significantly with respect to the specimens maintained in ambient temperature. The significant reduction in fracture energy by placing the... 

Considering the quasi-brittle mechanical properties of concrete, wedge-splitting tests are employed and improved in this paper to study the fracture behaviour of concrete. A novel wedge-splitting device is designed by fixing ten springs on the force transmission component. The adaptive spring force can be imposed on top of a concrete specimen to retard the brittle fracture process. With the proposed wedge-splitting test design for notched cuboid specimens, the complete load–strain/CMOD curves of concrete can be generated directly. The fracture toughness and the fracture energy can be calculated easily without numerical fitting using the double-K fracture model. The descending branch of the... 

It is vital to prevent brittle cracks in large structures. This is particularly important for a number of industry sectors including offshore wind, Oil & Gas, and shipbuilding where structural failure risks loss of human life and loss of expensive assets. Some modern steels exhibit high Charpy energy – i.e. high initiation fracture toughness, but poor resistance to crack propagation – i.e. low crack arrest toughness. The correlation between initiation and arrest toughness measured through small-scale testing is investigated in five different steels, which include S355 structural steel (with two different thicknesses), X65 pipeline steel, two high strength reactor pressure vessel steels and... 

Double cantilever beam (DCB) specimens were prepared according to standard surface mount technology (SMT). The samples were stored inside an environmental chamber at two different relative humidity values (i.e. 40 or 100%) for either 2 or 4 h. Then they were aged at 25 °C, 75 °C or 125℃ for the same time. Finally, after being cooled to room temperature, fracture tests were performed under mode-I loading conditions at a strain rate of 0.03 s−1 at room temperature. Storage time did not have a significant effect on the fracture behavior. The fracture load and energy of the solder joints decreased significantly when the temperature was increased from 25 to 75℃. By further increase in the... 

This paper investigates the effects of the first non-singular stress terms on the fracture assessment of sharp V-notches under mixed mode loading. First, numerical studies have been performed on a fracture test configuration called single V-notched ring (SVR) specimen. Then, the notch stress intensity factors as well as the coefficients of the first non-singular stress terms, which are vital parameters in brittle fracture of V-notched components, were calculated via a finite element over-deterministic algorithm for a wide range of loading and geometry conditions. The obtained results demonstrate that the SVR specimen is able to provide a complete range of mode mixities from pure mode I to... 

Thermal cracking is the prevalent type of distress experienced by asphalt pavements in cold regions. It is widely assumed that when thermal stresses induced in the pavement exceed the tensile strength of the asphalt surface layer, cracking occurs; however, the role of thermal fatigue should not be ignored. To better describe the low-temperature (LT) performance properties of modified asphalt binders, a new parameter, normalised tensile stress (NTS), was defined in this research. NTS values were compared with bending beam rheometer (BBR), direct tension (DT) and semi-circular bending (SCB) fracture test results. The m-value parameter of the BBR test specifies the type of asphalt binder. This...