Fatigue of Joints with Staggered Holes

It is customary in contemporary design for fatigue resistance of bolted connections to use slip-critical joints. However, many existing bridges are more likely to have bearing-type joints that use either rivets or high-strength bolts. Moreover, in many of these cases, hole patterns are staggered. Fatigue fracture of tension members with bearing-type joints that use staggered holes is observed to take place on a plane perpendicular to the axis of the member. The s2/4g rule, commonly used for static strength design of bolted tension members, is not applicable for this case, and current design rules do not make it clear just what net section is to be used to calculate the stress range. The fatigue resistance of bearing-type shear splices was investigated to assess the effect of bolt-hole stagger and gauge distance on fatigue resistance. Thirty-one symmetrical bearing-type shear splices were tested at different stress ranges. Staggers varying from zero to 75?mm were investigated on four sets of three specimens, and two gauge dimensions were investigated at two stress range levels. The test results indicated that neither the stagger nor the gauge dimension significantly influenced the fatigue life. An analysis of the test results indicated that none of the commonly used cross-sectional area definitions is adequate for stress range calculations. An approach that accounts for stress concentration in the calculation of the effective stress range is proposed. This approach multiplies the gross cross-section stress range by a correction factor determined using finite-element analysis. Design recommendations include a fatigue resistance curve with a slope of 7.0 and stress correction factors for the most common flat plate geometries. The proposed approach was validated using test results of other researchers on flat plates and built-up sections.     

Lithium Cobalt Titanate with the Spinel Structure as an Anode Material for Lithium Ion Batteries

Inorganic Materials - Mesoporous lithium cobalt titanate powder with the spinel structure, potentially attractive as an anode material for lithium ion batteries, has been prepared by...     

Fuzzy multi-attribute selection among transportation companies using axiomatic design and analytic hierarchy process

The basic concept in axiomatic design (AD) is the existence of design axioms. First of these axioms is the independence axiom and the second one is the information axiom. Information axiom proposes the selection of the best alternative that has minimum information. Analytic hierarchy process (AHP) is another multi-attribute method which is a decision-making method for selecting the best among a set of alternatives, given some criteria. The method has been extensively applied, especially in large-scale problems where many criteria must be considered and where the evaluation of alternatives is mostly subjective. Multi-attribute transportation company selection is a very important activity for effective supply chain. Selection of the best company under determined criteria (such as cost, time, damage/loss, flexibility and documentation ability) using both multi-attribute AD and AHP will be realized in this study. The fuzzy multi-attribute AD approach is also developed and it is compared by one of fuzzy AHP methods in the literature. The selection process has been accomplished by aiding a software that includes crisp AD and fuzzy AD.     

Electron-beam-pumped laser emitters with microrelief mirrors based on II–VI semiconductors

The power characteristics of electron-beam-pumped emitters based on II–VI compounds have been stukdied. The use of a microrelief with direction-selective reflective properties instead of a totally reflecting miror has made it possible to provide effective sukppression of closed non-characteristics and efficiency of lasers and to make them suitable for obtaining generation with high efficiency in a number of media, in particular YAG:Nd³⁺, KGW:Nd³⁺ and Lif:F (OH), at room temperature.     

Exploiting Confinement to Study the Crystallization Pathway of Calcium Sulfate

Characterizing the pathways by which crystals form remains a significant challenge, particularly when multiple pathways operate simultaneously. Here, an imaging-based strategy is introduced that exploits confinement effects to track the evolution of a population of crystals in 3D and to characterize crystallization pathways. Focusing on calcium sulfate formation in aqueous solution at room temperature, precipitation is carried out within nanoporous media, which ensures that the crystals are fixed in position and develop slowly. The evolution of their size, shape, and polymorph can then be tracked in situ using synchrotron X-ray computed tomography and diffraction computed tomography without isolating and potentially altering the crystals. The study shows that bassanite (CaSO₄ 0.5H₂O) forms via an amorphous precursor phase and that it exhibits long-term stability in these nanoscale pores. Further, the thermodynamically stable phase gypsum (CaSO₄ 2H₂O) can precipitate by different pathways according to the local physical environment. Insight into crystallization in nanoconfinement is also gained, and the crystals are seen to grow throughout the nanoporous network without causing structural damage. This work therefore offers a novel strategy for studying crystallization pathways and demonstrates the significant impact of confinement on calcium sulfate precipitation, which is relevant to its formation in many real-world environments.     

Structure and properties of high-modulus alloys of the Ti-B system

We study the influence of alloying with Al, Zr, and Si on the structure and mechanical properties (including the modulus of elasticity) of cast and deformed alloys of the Ti-B system. It is shown that, by optimizing the compositions of titanium alloys subjected to combined silicoboride hardening and additionally alloyed with aluminum, it is possible to get the modulus of elasticity E as high as 160 MPa with a strength σ of 1500 MPa and a level of plasticity δ of 2–5% at room temperature. __________ Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 42, No. 3, pp. 27–32, May–June, 2006.     

Unified block shear equation for achieving consistent reliability

Equations in design standards for block shear vary widely and, when used for different types of connections, they provide significantly inconsistent levels of safety. In many cases reported in the literature, recommended changes are intended to address a specific deficiency without assessing the overall impact on design in a broader sense. Moreover, a reliability study is required to fully assess the level and consistency of resulting safety indices. To resolve these shortcomings and inconsistencies, a database of 205 block shear tests on gusset plates, angles, tees, and coped beams from 17 different research programs was compiled and a reliability study conducted. From this study, as well as from the failure modes observed in the tests, a unified block shear equation is proposed that provides much more consistent test-to-predicted block shear capacity ratios over a wide variety of connection types, geometries, and steel grades. The unified equation also results in consistent safety indices for gusset plates, angles, tees, and coped beams with either one or two lines of bolts, a goal that is not achieved by other methods available. A resistance factor is recommended for design that will achieve an appropriate level of safety.     

Osteoporosis: preventive strategies

We compared manual lymph drainage (MLD) with sequential pneumatic compression (SPC) for treatment of unilateral arm lymphedema in 28 women previously treated for breast cancer. After 2 weeks of therapy with a standard compression sleeve (Part I) with maintenance of a steady arm volume, each patient was randomly assigned to either one of two treatment regimens (Part II). MLD was performed according to the Vodder technique for 45 min/day and SPC was performed with a pressure of 40-60 mmHg for 2 hours/day. Both treatments were carried out for 2 weeks. Arm volume was measured by water displacement. Arm mobility, strength, and subjective assessments were also determined. Lymphedema was reduced by 49 ml (7% reduction) (p = 0.01) in the total group during Part I. During Part II, the MLD group decreased by 75 ml (15% reduction) (p < 0.001) and the SPC group by 28 ml (7% reduction) (p = 0.03). The total group reported a decrease of tension (p = 0.004) and heaviness (p = 0.01) during Part I. During Part II, only the MLD group reported a further decrease of tension (p = 0.01) and heaviness (p = 0.008). MLD and SPC each significantly decreased arm volume but no significant difference was detected between the two treatment methods.