Materials Testing

doi: 10.3139/120.016112pmid: N/A

Czichos, Horst

doi: 10.3139/120.110943pmid: N/A

KurzfassungAnlässlich ihres 50-jährigen Bestehens wird die Tribologie – die Wissenschaft und Technik von Wirkflächen in Relativbewegung – in einer Übersicht dargestellt. Bei ingenieurwissenschaftlichen Anwendungen haben tribologische Systeme, die durch die Wirkflächen charakterisiert werden, einen dualen Charakter. Sie sind einerseits notwendig, um technische Aufgaben zu erfüllen, aber auf der anderen Seite sind sie zwangsläufig mit Reibungs- und Verschleißprozessen verbunden, die zu reibungsbedingtem Energieverlust und verschleißbedingter Materialdegradation führen können. Im vorliegenden Übersichtsbeitrag werden die Grundlagen von Reibung und Verschleiß von der Nano- bis zur Makroebene betrachtet und es werden die Basisparameter zur Modellierung tribologischer Systeme im Laborversuch beschrieben. Da tribologische Prozesse zu Fehlzuständen (fault) und Ausfällen (failure) führen können und damit die Funktionssicherheit und die Strukturintegrität negativ beeinflussen können, werden die Prinzipien der technischen Zuverlässigkeit und der Zustandsüberwachung ebenfalls kurz dargestellt.

Kaatz, Marcus; Meywerk, Martin; Spittler, Sven

doi: 10.3139/120.110940pmid: N/A

AbstractA synthetic test method is described which is capable of investigating various suspension fasteners on a dynamic half-axle test rig. This test method is advantageous compared to an expensive and time-consuming driving cycle. In advance vehicle specific measured values that serve as input parameters for the test rig experiments are required. This study shows how the adhesion limit influences the interdependencies between vertical load, side slip angle and longitudinal slip. By means of multibody systems and in consideration of the determined nonlinear tire characteristics, this method can be applied to investigate suspension fasteners of vehicles without expensive and time-consuming test drives. Validation results of different vehicles are given which demonstrate that the method is appropriate to a wide range of vehicles.

Thamilarasan, Kollapuri; Rajendraboopathy, Sadayan; Reddy, Gankidi Madhusudhan; Rao, Tadivaka Srinivasa; Rama, Sajja; Rao, Koteswara

doi: 10.3139/120.110941pmid: N/A

AbstractHigh strength aluminum alloys of type AA2014 are used in aerospace applications. This alloy is considered unweldable using fusion welding processes. Friction stir welding being a solid state process has been proved to be a suitable process for obtaining sound welds of these materials. In the current study, 8 mm thick rolled AA2014-T651 aluminum alloy plates were joined using friction stir welding. The corrosion behavior of base material and friction stir welds was investigated using the salt fog test (ASTM B117). The corrosion resistance of the welds and parent material in the basic solution was found to be better than that in acidic and neutral solutions. It was also found that the corrosion rate increases with increase in time of exposure. It has been observed that corrosion attack is greater in the weld region than in the parent material and within the weld, heat affected zone has been found to be more susceptible to corrosion compared to the weld nugget and thermomechanically affected zone regions. Transmission electron microscopy studies revealed coarser precipitates and precipitate-free zones in the heat affected zone which are concluded to be the reasons for more susceptibility to corrosion.

Asiri, Saeed A.; Hedia, Hassan S.; Fouda, Noha

doi: 10.3139/120.110942pmid: N/A

AbstractSurfaces are the primary place of contact a biomaterial and its host organism. Surface treatment or coating provides means to overcome the problem which appeared after knee replacement surgery. There are two main problems: stress shielding and subsequent bone remodeling cause bone resorption around the implant especially at the proximal part of the knee under the tibia tray. The other problem is stem tip pain. Therefore, the aim of this investigation is to find a new design of coating material of a cementless total knee replacement using functionally graded material (FGM). In particular, the objective of this research is to find the optimal material compositions as well as the optimal gradation direction. It has been found that using both vertical and horizontal FGM coatings increased the von Mises stress at the proximal part of the tibial cancellous bone. The von Mises stress in cancellous epiphyseal bone was increased by 77 % using vertical and horizontal FGM coating compared to HAP coating. It has been determined that this new coating design will improve the performance of a cementless tibia tray and will increase the life of the knee prosthesis.

Akçamlı, Nazlı; Gökçe, Hasan; Uzunsoy, Deniz

doi: 10.3139/120.110944pmid: N/A

AbstractAluminum matrix composites containing graphene nano-platelets (GNPs) as reinforcement additive were fabricated by a two-step process consisting of mechanical alloying and pressureless sintering. The effects of graphene nano-platelets amounts and mechanical alloying duration on the microstructural and mechanical properties of aluminum were investigated. The characterization studies were performed by X-ray diffractometry, Raman spectroscopy, scanning electron microscopy/energy dispersive spectrometry, particle size analysis, differential scanning calorimetry, Archimedes' density and microhardness test method. The microhardness of composites increased gradually by the addition of 0.5 and 1 wt.-% GNP, whereas an adverse effect was observed by the increment of the GNP amount to 2 wt.-%.

Kavitha, Ayyalu; Kannan, Raman; Loganathan, Subramani

doi: 10.3139/120.110945pmid: N/A

AbstractZirconium nitride (ZrN) thin films were prepared on stainless steel (SS) substrates by medium frequency (MF) reactive sputtering with gas ion source (GIS) by varying the deposition time and obtained thickness (tZrN) in the range of 1.25 to 3.24 μm. The effect of thickness on the structural and microstructural properties was studied using XRD and AFM. XRD characterization revealed that the texture of the ZrN thin films changes as a function of thickness. Both, the (111) and (200) peak, appear initially and (111) becomes more intense with increasing tZrN. AFM imaging revealed that the ZrN thin film coated with tZrN ≈ 3.24 μm shows larger grains that are uniformly distributed over the surface. An average hardness value of 19.79 GPa was observed for ZrN thin films having tZrN ≈ 3.24 μm. The ZrN thin films having tZrN ≈ 3.24 μm exhibits better adhesion strength up to 20 N. The electrochemical polarization studies indicated that the ZrN thin film having larger thickness shows improved corrosion resistance compared to SS in 3.5 % NaCl solution.

Çevik, Bekir

doi: 10.3139/120.110946pmid: N/A

AbstractIn this study, polyethylene specimens were welded by using friction stir spot welding (FSSW) technique. Welding process was carried out by a rotation of 460 and 900 rpm. Under constant friction force, five different dwell times (20, 40, 60, 80 and 100 s), four different delay times (15, 30, 45 and 60 s) and three different pin profiles (M6 × 1, M6 × 1.25 and M6 × 1.5) were used. During the welding process, temperature measurements under the welding cenetrs were performed using a four multichannel K type digital thermometer. Tensile shear tests were used to characterize the samples. Tensile performance of the samples was significantly affected by the welding parameters.

Köse, Ceyhun

doi: 10.3139/120.110947pmid: N/A

AbstractUse of laser welding is constantly increasing as it allows attainment of a high welding efficiency and weld quality. In this study, 5754 grade aluminum plates were joined on both sides by means of pulsed Nd:YAG power intensified micro scale laser welding method at three different laser powers in flat position by using supplemental welding wire. Mechanical properties of joints were examined by means of tensile and bending tests and by micro hardness measurements, and their structural changes were examined by means of optical microscope, SEM and EDS. As a result, it was determined that the welded joints could display an adequate tensile strength when exposed to tensile strain under action of static loads, but their bending strength remained relatively weaker. Mechanical properties of welded samples were observed to improve with increasing penetration depending on the increase in the laser power. It is believed that use of siliceous supplemental welding wire was also effective in strength improvement.

Shashev, Yury; Kupsch, Andreas; Lange, Axel; Müller, Bernd R.; Bruno, Giovanni

doi: 10.3139/120.110948pmid: N/A

AbstractTalbot-Lau interferometry provides X-ray imaging techniques with significant enhancement of the radiographic contrast of weakly absorbing objects. The grating based technique allows separation of absorption, refraction and small angle scattering effects. The different efficiency of rectangular and triangular shaped phase gratings at varying detector distances is investigated. The interference patterns (Talbot carpets) are modeled for parallel monochromatic radiation and measured by synchrotron radiation. In comparison to rectangular shapes of phase gratings much higher visibility is obtained for triangular shapes which yield enhanced contrast of a glass capillary test specimen.