Investigation of high strength steel connections with several bolts in double shear

A series of 26 tests on tension splices with three or four bolts positioned in the direction of bearing force are presented. Steel grade S690 was used for the fabrication of connection plates. The tests were also numerically simulated to obtain the distribution of forces between bolts. Tests on similar connections made of high strength steel were gathered from the literature. These tests were also numerically simulated. The numerical results agreed with experimental data very well, and were used to evaluate the bearing resistance formula according to EN 1993-1-8.     

双剪高强螺栓连接研究

对用3个或4个螺栓连接的受拉节点进行26组承载力试验,节点板所用钢材等级为S690。对试验进行数值模拟,研究螺栓间的剪力分布。对文献中由高强型钢制作的类似节点进行试验,并进行数值模拟。数值结果与试验数据非常吻合,以此对规范EN1993-1-8中的承载力公式进行评价。     

The optimization of material flow in production

Market demands are different: they tend to require individual, customized products of high reliability and high quality and also produced in right time. Material flow optimization is an indispensable step to be taken. The proposed optimization method is material flow analysis, which is giving an insight of the production organization of a company and its evaluation at different organizational levels. The analysis is based on a technological database and on the organization of individual departments of a company. It enables a material and information flow analysis as well as an analysis of the department and machines layout respectively. The result of the analysis is material flow rationalization, thus minimizing production costs.     

Early experience with in situ chip-to-chip alignment characterization of Proximity Communication flip-chip package

Proximity Communication (PxC) facilitates the integration of VLSI chips in a package using near-field capacitive coupling between chips, eliminating the need for solder or wires for I/O at the chip-to-chip interface. PxC provides chip-to-chip interconnect with bandwidth density and energy per bit similar to on-chip I/O, enabling system on a chip performance within a package. We have built early packages to explore assembly concepts and developed test methods for verification of the PxC design space. This package started with an adhesively-bonded three-chip subassembly of two Island chips and one Bridge chip. The two outer Island chips were reflowed to an alumina ceramic substrate. In the resulting package, communication between chips was achieved using PxC from Island to Bridge and then from the Bridge to the other Island. We demonstrated the ability to detect the X, Y, and Z chip-to-chip relative location and the ability to steer PxC data to optimize signal integrity within the package. This paper describes the first demonstration of active monitoring of chip-to-chip alignment during thermal cycling, in a PxC-enabled package. Leveraging this work, future packages will better exploit PxC benefits such as free-space electrical interconnect and re-workability of multi-chip modules.     

Investigation on electrical and microstructural properties of Thick Film Lead-Free resistor series under various firing conditions

The paper presents investigation of four lead free thick film resistor pastes, developed at ITME, denoted R-100, R-1k, R-10k and R-100k with sheet resistivities of 0.1, 1, 10 and 100 kΩ/□, respectively. The resistors were based on RuO₂ as the conductive phase. The aim of the work was to evaluate the influence of firing conditions of the resistive pastes on a sintering process. The pastes were screen printed onto alumina substrate with prefired AgPd lead-free terminations. They were fired at several temperatures from 750 to 950 °C for 10 min at peak temperature, as well as fired at the highest temperature for 6 h, in order to bring the sintering process into the equilibrium. The properties of the resistors, i.e , sheet resistivity and temperature coefficient of resistance (TCR), microstructure changes, glass crystallization upon firing, etc., were examined. Dried and fired resistor samples were evaluated by X-Ray diffraction analysis and by the scanning electron microscopy. The RuO₂ conductive phase maintained the same crystal structure regardless of the firing conditions. No devitrification was observed in lead-free resistors glasses. The lattice constants of RuO₂ were uniform after firing at temperatures over 800 °C. The resistors matched the desired resistivity and the TCR was the least temperature dependent at the firing temperatures around 850 °C.     

An investigation of thick PZT films for sensor applications: A case study with different electrode materials

Lead zirconate titanate (PZT) is a piezoelectric material that can sense or respond to mechanical deformations and can be used in ceramic micro-electro-mechanical systems (C-MEMS). A thick-film paste was prepared from a pre-reacted PZT powder (PbZr_0.53Ti_0.47O₃) and thick-film technology (screen-printing and firing) was used to deposit the PZT layers on LTCC tapes and on alumina substrates. The microstructural, electrical and piezoelectric characteristics of the thick PZT films on relatively inert alumina substrates and on LTCC tapes were studied. Preliminary experiments indicated that due to the interaction between the printed PZT layers and the LTCC substrates during firing the electrical characteristics deteriorate significantly. To minimise the influence of substrate-film interactions different electrode materials and the use of additional intermediate layers as a barrier were evaluated. The dielectric permittivities, dielectric losses, and piezoelectric coefficients (d ₃₃) were measured. The dielectric permittivities of the thick films fired on LTCC substrates were lower (210 with gold electrodes and 430 with silver electrodes) than those measured on alumina substrates (500). The piezoelectric coefficients d₃₃ were measured with a Berlincourt piezometer. The d ₃₃ values measured on the LTCC substrates were relatively low (60–80 pC/N) compared with the values obtained for the alumina substrates (around 140 pC/N). The lower dielectric constants and piezoelectric coefficients d ₃₃ of the films on LTCC substrates are attributed to the formation of phases with a lower permittivity. This was a result of the diffusion of SiO₂ from the LTCC into the active PZT layer. The diffusion of silica was confirmed by the SEM and EDS analyses.     

Numerical modelling of ceramic mems structures with piezoceramic thick films

The correctness of the material parameters that are used in numerical models is of key importance for any numerical analysis. Because of a lack of available material parameters and standard procedures for characterising piezoceramic thick films, special attention has to be paid to providing data for accurate material models. In the presented work, thick-film (TF) lead–zirconate–titanate (PZT) structures made on different ceramic substrates were considered. In order to obtain proper material parameters for TF PZT some unconventional characterisation approaches were used e.g. nano-indentation test for evaluation of the compliance of the piezo film. The results of characterising TF PZT structures on two different ceramic substrates, Al₂O₃ and pre-fired low temperature cofired ceramic (LTCC), are presented. For validation purposes simple cantilever-type actuators were modelled using the piezoelectric coupled-field capabilities of the finite-element (FE) package Ansys/Multiphysics and simulation results were compared with the measurements of the real structures.     

Telecommunication liberalization and economic development in European countries in transition

Developed and widely available telecommunications services are regarded as key enablers of a new economy. In Eastern European countries in transition, investment in telecommunications is generally perceived as a stimulus for economic growth. We investigate empirical correlation and Granger causality between certain indicators of telecommunications activity and economic growth. The indicators include total investment in the telecommunications sector and other parameters such as the penetration rate of services. We also propose additional indicators that may describe telecommunications sector development better than traditional, fixed, telephony-based measures. This is due to the migration of users from fixed to mobile networks, and from basic to broadband Internet access in the last few years. In the near future one also can expect broadband Internet users to move to mobile network infrastructure.     

Persistent Fibroadipogenic Progenitor Expansion Following Transient DUX4 Expression Provokes a Profibrotic State in a Mouse Model for FSHD

FSHD is caused by loss of silencing of the DUX4 gene, but the DUX4 protein has not yet been directly detected immunohistologically in affected muscle, raising the possibility that DUX4 expression may occur at time points prior to obtaining adult biopsies for analysis, with consequent perturbations of muscle being responsible for disease progression. To test the extent to which muscle can regenerate following DUX4-mediated degeneration, we employed an animal model with reversible DUX4 expression, the iDUX4pA;HSA mouse. We find that muscle histology does recover substantially after DUX4 expression is switched off, with the extent of recovery correlating inversely with the duration of prior DUX4 expression. However, despite fairly normal muscle histology, and recovery of most cytological parameters, the fibroadipogenic progenitor compartment, which is significantly elevated during bouts of fiber-specific DUX4 expression, does not return to basal levels, even many weeks after a single burst of DUX4 expression. We find that muscle that has recovered from a DUX4 burst acquires a propensity for severe fibrosis, which can be revealed by subsequent cardiotoxin injuries. These results suggest that a past history of DUX4 expression leads to maintained pro-fibrotic alterations in the cellular physiology of muscle, with potential implications for therapeutic approaches.     

Electrodeposition of copper: the nucleation mechanisms

The nucleation mechanisms of copper during electrodeposition of thin films from sulfate solutions were studied by utilizing the electrochemical techniques (cyclic voltammetry and chronoamperometry) and atomic force microscopy (AFM). Near atomically smooth glassy carbon was used as the deposition substrate (electrode). The copper nucleation mechanisms were examined as a function of solution pH, copper concentration, deposition potential, temperature, and background electrolyte. It was found that with pH and copper concentration increase, the nuclei size increased, while the nuclei population density decreased. An increase of deposition potential produced smaller nuclei and higher nuclei population density. Temperature affected the morphology of deposited copper. The presence of background electrolyte also influenced the morphology and population density of copper nuclei. The nucleation mechanisms were examined by fitting the experimental data (chronoamperometry) into the Scharifker-Hills nucleation models. It was found that at pH 1, in the absence of background electrolyte, copper nucleation was instantaneous. At pH 2 and 3, the mechanism was inconclusive. In the presence of background electrolyte, the mechanism at pH 1 and 2 was mixed, while at pH 3, the mechanism was progressive nucleation.