Papers by Keyword: Reduced Modulus

Abstract: This study discussed the effect of blast exposure distance of lead-free solder on micromechanical properties. Sn-Ag-Cu solder samples were exposed to 1000 g of Plastic Explosive. The soldered samples were placed at a distance of 1 m, 2 m and 4 m distance from the blast source. In order to study micromechanical properties in localized and more details, the nanoindentation approach was used. The indentation was performed at the center of the solder to examine the hardness and reduced modulus properties. The load-depth curve of indentation for 1 m distance from the blast source has apparent the discontinuity during loading as compared to the control sample. The hardness value increased as the distance from the blast source increased. The shortest distance from the blast source gives a high impact on the degradation of hardness properties as compared to others. This result is important in assessing the effect of exposure distance from the blast source.

Abstract: Electronic packaging is the technology concerning to the establishment of electrical interconnections and it is a major discipline within the field of electronics engineering. Packaging of an electronics system should considered the protection from mechanical damage, cooling, radio frequency noise emission and protection from electrostatic charge. Solder alloys have been extensively used as interconnection materials for microelectronic package. Solder joint in radiation environment requires higher reliability and resistance to any damage caused by ionizing radiation. The electrical failure during radiation has proved that the reliability of solder joint is importance and sensitive to the service condition. In this study, a lead-free solder alloy, SAC305 (96.5Sn3.0Ag0.5Cu wt.%) were prepared into two batches, which are unirradiated and irradiated batches with the various doses 5, 50, 500 Gy of gamma radiation. Nanoindentation was used in order to investigate the effect of the radiation to micromechanical properties such as hardness, H and reduced modulus, E of the solder. The results showed that the SAC solder changed when exposed to gamma rays. The hardness of the specimens calculated from the nanoindentation were decreased to 195.4 from 279.6 MPa with the increasing of radiation dose. These values of hardness are also lower than the hardness of non-irradiated sample indicating possible radiation damage and needs further related atomic dislocation study. The reduced modulus for irradiated specimens significantly increased as well, with values from 25.6 to 123.9 GPa after exposure. The increment of the reduced modulus occurred as a result of strain hardening or softening of the solder.

Abstract: Civil engineers like to use complex construction systems which resist mechanical strain well. Complex material and structural arrangement is possible to see in biological materials as wood but as bone or dentin too. This paper deals with a property trend of biological material, dentin, and can serve as an inspiration for designing resistant constructions. The analysis was carried out by a method of nanoindentation. The differences of property values depending on location of indents in dentin structure were surveyed. Especially, the differences of hardness and reduced modulus were important. The huge number of indents was made during the experiment. The indents were divided into categories according to the distance from the nearest material interface. The upward trend was found out for both observed properties. The category which was the closest to the material interface showed the average value of hardness ~ 965 MPa, whereas the furthest ~ 1222 MPa. It was growth more than 20%. Reduced modulus showed similar trend. These results are different from these which have been performed by other authors so far.

Abstract: The aim of this work is the description of microstructure and comparison of micromechanical properties of cylindrical shaped intraosseous parts of dental implants with plasma modified surface and with threaded modification. Differences in elastic parameters (such as reduced modulus (E_r) and hardness (H)) of investigated implants within the supporting part of the shaft and surface layer in two different directions (proximal and lateral) are compared using experimental method of nanoindentation. Machined implants of titanium alloys Ti6Al4V with plasma modified surface of sprayed titanium with hydroxyapatit (HA) Ca₁₀(PO₄)₆(OH)₂ from different batches of product were available for measurements. SEM element analysis revealed a heterogeneous structure and various concentrations of the essential chemical elements (C, O, P, Ca) on the surface of implants. Results of elastic moduli and hardness was monitored in different locations. On a large statistical set of measurements was indicated that average reduced modulus of implant shafts of titanium alloy is approximately 126 GPa. Differences of E_r in case of peripheral hydroxyapatite layer are in range of ~145 GPa – ~163 GPa according to the exact composition of surface modification in the individual batches of the product. The difference of measured values on individual samples in a proximal/lateral direction is approximately 10%.

Abstract: The nanohardness of WC – Co hardmetals has been investigated using instrumented indentation and Berkovich tip indenter. The nanohardness, HIT, and indentation modulus, EIT, of Co phase and individual WC grains and the influence of their crystalographic orientation have been studied. SEM, AFM and EBSD methods were used for the characterization of the microstructures and indents and for the identification of crystallographic orientation of WC grains, respectively. Strong indentation load-size effect and significant influence of the crystallographic orientation of WC crystals on HIT and EIT have been found. The nanohardness of Co binder was approximately 10 GPa and that of WC grains varied between 25 and 50 GPa, depending on the grain orientation and load. The nanohardness values of the basal and prismatic planes of individual WC grains at load of 10 mN were 40.4 ± 1.6 GPa and 32.8 ± 2.0 GPa, respectively.

Abstract: In semiconductor packaging, conventional test procedures for evaluating mechanical properties of ball bonded gold wire bonding are well established. However these tests do not provide clear understanding related to the strength mechanism leading to improper reliability data. The nanoindentation approach, uses equipment called nanoindenter, gives advances mechanical (sub-micromechanical) characterization, particularly the combination effect of elastic and plastic deformation. Wire bonding process was prepared using thermosonic-wire bonding technology with 25m diameter gold wire and copper as substrate. To obtain mechanical properties, ball-bonded was cross-sectioned diagonally before indented at various locations. Results show that mechanical properties vary according the locations throughout the surface; at the centre, at the edge and at the area near intermetallics layer. This indicates test location plays important role in determining ‘meaningful’ mechanical properties.

Abstract: It is revealed that the conventional reduced modulus used in depth-sensing indentation tests is invalid for a flat-ended cylindrical indenter due to the fact that the contact area during the loading is a constant irrelative to load. The load-displacement curve of flat punch is related to the length of the punch and the ratio of the elastic modulus of the indenter to the specimen (the modulus ratio Ei/E). Furthermore, theoretic analysis and finite element simulation demonstrated that, for conical indenter, the measured hardness from depth-sensing indentation tests would increase with increasing modulus ratio because the load increased with the ratio for the same displacement.

Abstract: Human bone fracture associated with osteoporosis was hypothesized to be related to the alteration of mechanical properties in bones. In this work, cortical and trabecular bones from human femoral heads were studied. Bone samples of eight female and four male patients, with ages varying from 37 to 93 years, were collected from total hip replacement surgery. Reduced modulus (Er) and hardness (H) of osteons, interstitial lamellae and trabeculae were characterized by nanoindentation. The results showed both the reduced modulus and hardness of the interstitial lamellae were significant higher than those of osteons and trabeculae. Though there was no significant difference in microstructures in the Group A (age < 60 years) and B (age > 60 years), the Group B bones demonstrated to be stiffer.

Abstract: A simple and material-independent indentation technique is presented to determine the hardness and elastic modulus of solid materials. This method requires only three experimentally measured quantities to determining the material properties, i.e., the peak load, corresponding displacements and the depth of residual indent, without curve fitting process and regression analysis. The results obtained from this simple technique were consistent with those obtained by using the conventional method. Furthermore, energy dissipation and the ability of elastic recovery of the ceramic materials were evaluated from the measured indentation data.

Abstract: Although instrumented indentation machines have existed since the 1950s, it is only during the past 20 years or so that there has been a very rapid rise in their use and popularity for determining mechanical properties of bulk solids, thin films and biological materials. Nowadays, machines are available with which indentation experiments are conducted automatically and the data obtained are also analyzed automatically using software, which is based on certain hypotheses and simplifying assumptions. By carrying out several series of comprehensive experiments, using rigid and elastic indenters and elastic substrates, it is shown that the current methods of nanoindentation data analysis are fundamentally flawed, which can lead to incorrect and misleading results. A new experimental approach has been suggested here, which is free from such flaws.