Materialwissenschaft und Werkstofftechnik最新文献

Surface modification techniques play an important role in adjusting the physicochemical properties of titanium and its alloys. To reduce the penetration of alloying element ions into the body, various types of oxide coatings are used to protect it from the corrosive environment. Another important issue related to the surface layer requirement is ensuring an appropriate set of mechanical properties. Accordingly, in this study, the mechanical and electrochemical properties of the silicon dioxide layers formed by the deposition of nano physical vapor deposition on the surface of titanium and titanium 13-niobium 13-zirconium alloy samples were investigated. To evaluate the mechanical properties of the layers produced by this method, hardness tests were carried out, as well as tests on the adhesion of these layers to the metal substrate. On the other hand, electrochemical properties were studied using potentiodynamic measurements to assess the resistance to pitting corrosion, followed by impedance measurements to interpret the processes and phenomena occurring at the silicon dioxide layer/electrolyte interface. The data obtained showed different mechanical and electrochemical properties of the silicon dioxide layers generated with varying process parameters.

In the case of the Yeongdodaegyo bridge, abnormal noise occurred only in summer when it was opened, and the expected cause of noise was expected to be due to bearing damage or deformation friction. Therefore, a non-destructive test was performed around the spherical bearing, which is a major part of the drawbridge components connected to the rotating shaft girder. For the measurement to analyze the cause of noise, the real-time noise source was tracked during hoisting using an acoustic sensor according to the angular displacement of the rotating shaft. Through this, we tried to identify the noise source by identifying the left and right real-time deformation (torsion, deflection, inclination) and the friction part of the damaged bearing. As a result of the analysis, irregular noise was generated from the left and right sides, and noise was generated when the twist, deflection, or tilt of the rotation shaft occurred. The bottom of the left and right bearings was found to be the main source of noise, and the bearing contact during deformation is considered to be the cause of the noise.

Antibacterial properties of components are increasingly becoming an important challenge in material development especially in polymer technology. A well-known additive with which an antibacterial effect can be achieved is the metal oxide titanium dioxide. The aim of this research work was to investigate possible influences on the flexural properties of additively manufactured components resulting from the addition of titanium dioxide as an antimicrobial additive. Compounds with 5 %, 10 % and 15 % titanium dioxide and polyamide 12 as matrix material were produced. Three-point bending test specimens were fabricated out of these compounds, anaylsed and the results were compared with specimens made of virgin polyamide 12. The investigations show a general loss in ductility compared to the virgin polyamide 12. A comparison of the different titanium dioxide contents shows no clear change in the flexural stress at conventional bending. The flexural strain at break seems to decrease for higher titanium dioxide contents.

Copper of a high purity features excellent electric conductivity, but generally very low mechanical properties. Nevertheless, optimized deformation/thermomechanical treatment can introduce favorable combinations of both. The presented study characterizes the correlation of microstructure development and electric properties within copper processed by the severe plastic deformation method of high pressure torsion, the primary advantage of which is that it enables to achieve grains with the sizes in the ultra-fine, or even nano scales. The study investigates structure development during progressive deformation. In other words, samples processed by single and double high pressure torsion revolutions were evaluated from the viewpoints of grain sizes and grain boundaries, and the results were correlated with the experimentally measured electric conductivity. The single high pressure torsion revolution contributed to grain size decrease, while the structure after double revolution exhibited very fine grains, especially at the sample periphery featuring the highest imposed strain. Both the samples also exhibited increases in microhardness (especially after double revolution), and electric conductivity higher than 100 % IACS. The results confirmed that copper conductors featuring enhanced mechanical properties and favorable electric conductivity can be manufactured by severe plastic deformation.

The influence of the transition alloying element nickel and the alkaline earth element strontium on the microstructure and tensile properties of squeeze cast Al−Si-Cu alloy under as-cast condition at elevated temperature of 100 °C, 200 °C and 300 °C is investigated in comparison with the conventional Al−Si-Cu alloy (A380). Aluminum alloy A380 is alloyed and modified with 2 wt% additional nickel (Ni) and 0.02 wt% strontium (Sr). Squeeze casting is employed to cast the modified A380 under an applied pressure of 90 MPa. The results of tensile testing at the selected elevated temperatures indicate that the Ni and Sr containing A380 alloy exhibits a significantly improvement on tensile properties, specifically ultimate tensile strength and yield strength with 10 %-30 % increases. The as-cast microstructures of both the conventional and Ni and Sr-containing alloys are observed by an optical microscope and further analyzed with scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The presence of Ni-containing intermetallic phases with Ni addition, and the modified eutectic Si phase with refined morphologies due to the Sr addition should be responsible for the considerable enhancement on the as-cast strengths of the squeeze cast Ni- and Sr-containing alloy over those of the conventional A380 alloy.

Plastic ball-grid array (PBGA) package assembly comprises various materials with different thermo-mechanical properties, and the solder ball-grid patterns can significantly influence the package deformation and solder ball stress. This study utilizes moiré interferometry to investigate the deformation behavior of wire bonded plastic ball-grid array (WB-PBGA) packages under varying temperatures. Real-time moiré interferometry experiments were conducted to capture fringe patterns representing package deformation at different temperature stages. Experiments were conducted for three different wire bonded plastic ball-grid array packages with distinct solder ball array configurations: full grid patterns (WB-PBGA-FG) and perimeter patterns with/without central connections (WB-PBGA-PC/P). The analysis revealed considerable variations in thermal strain distribution and positioning of the critical solder ball within the package assembly, depending on the solder ball-grid pattern. Among these wire bonded plastic ball-grid array packages, WB-PBGA-P/C exhibited the most substantial bending deformation, experiencing the highest effective strain, which directly impacts solder ball failure. These findings emphasize the importance of solder ball-grid patterns in understanding the deformation behavior and reliability of WB-PBGA packages under varying temperature conditions.

The study focusses on a low-density polyethylene/isotactic polybutene-1 peel system with low-density polyethylene as matrix and isotactic polybutene-1 as peel component sealed against itself (cohesive peel system), and on an ethylene vinyl acetate/linear low-density polyethylene peel system with ethylene vinyl acetate as matrix and linear low-density polyethylene as peel component sealed against polyethylene terephthalate (adhesive peel system). Due to a new approach to estimate the true fracture surface using 3D reconstruction, it was possible to determine the true adhesive energy release rate, especially for cohesive peel systems. This enables a direct comparison of the fracture mechanics parameters determined from both types of peel systems. The results reveal that the recipe has a distinct influence on the peel behavior. An increasing amount of the used peel component leads in any case to a decrease of the peel force as well as of the energy release rate for both, sealed adhesive and cohesive peel systems. Using application engineering examples generalizable relationships between structure and properties of peel systems could be estimated and the structure sensitivity of the fracture mechanical parameters could be proven.

Mycelium materials represent a new class of environmentally friendly materials for structural applications that can grow on low-cost organic waste while achieving satisfactory thermal or acoustic insulation properties. The aim of this study is to grow a biocomposite of mycelium on flax tows and then use it as a reinforcement with a geopolymer matrix. To achieve this, three species of mycelium were selected, a culture process was carried out, and then samples of the composite were synthesized with a geopolymer matrix. To determine the utility in terms of structural applications, the density, compressive strength, and thermal conductivity of the samples were tested. Scanning electron microscope images were also taken to observe the microstructure. The results indicate that it is possible to produce a mycelium composite with a geopolymer matrix. A lower density was achieved for all samples than for the geopolymer without reinforcement. The coefficient of thermal conductivity was reduced only for the sample with one of the mycelia. The compressive strength for biocomposites was between 12.1 MPa–14.2 MPa, this value is enough for some engineering applications.