Key Engineering Materials Vols. 348-349

Abstract: This study was carried out to investigate quantitatively the relationship between the degree of reinforcement corrosion and the mechanical properties of reinforcement. In the experiment, the tensile test of corroded reinforcement was conducted at the different stage of the degree of reinforcement corrosion. As a result, it was found that the chloride-induced corrosion induce the pitting and the corrosion using electrical current induce the uniform corrosion. As the degree of reinforcement corrosion increased, the nominal yield point and nominal elastic modulus both decreased. Also, there were very high correlations between the degree of reinforcement corrosion and the mechanical properties of reinforcement. We could make the material constitutive laws for the mechanical properties of reinforcement as a function of the degree of reinforcement corrosion to analyze the damaged RC members with reinforcement corrosion using finite element method.

Abstract: RC beam with corroded tension rebars were strengthened with carbon fiber sheets(CFS) and were subjected to static loading tests to investigate the flexural strengthening effect of CFS. The test results confirmed that CFS are effective in reducing stresses to be carried by tension rebars and increasing flexural strength. Since the deformation capacity of the strengthened specimens was increased by anchoring the CFS and since the maximum strength of the specimens was determined by detachment or rupture of CFS, the flexural strength of the strengthened specimens could be calculated from an existing formula. Experimentally determined load-deflection relationships for RC beams were reproduced accurately through a FEM analysis modeling the bond elements between the concrete and the CFS. Practical application of the CFS sheeting method to RC beams requires improvement of the strength of bond between CFS and concrete.

Abstract: In this study, an Ohno's anti-symmetric shear loading test was conducted after strengthening reinforced concrete (RC) beams damaged by corrosion of stirrup, with carbon fiber sheets (CFS) with a view to reviewing the effect of CFS on shear strengthening. As a result, it was found that CFS like stirrups could take shear stress, and that shear strength could be increased by using more CFS for reinforcement. It was also revealed that shear strength could be calculated by an existing evaluation equation by properly evaluating the effect of CFS on shear strengthening, based on the quantity of reinforcing CFS, ways of fixing the sheets and anchorage length as the effect on shear strengthening varied depending on the fixing method while sheet anchorage increased deformability.

Abstract: In this paper corrosion-fatigue failure of a roller in a cardboard production plant has been analyzed. The failure occurred at the bearing neck of the roller. Mechanical and chemical properties of the roller are determined and the fracture surface is investigated. Forces applied on the roller is examined, stress calculations are carried out and fatigue safety factor is calculated. Stress analysis is also applied to roller and bearing neck by using Finite Element Method (FEM) and the results are compared with the calculated values. Because of very high safety factor, reasons for failure are investigated and effects of fatigue failure are determined. These effects are corrosion-fatigue, working conditions and notch effect. In conclusion precautions which have to be taken to prevent a similar failure is explained by using FEM.

Abstract: The paper demonstrates the close correspondence between two local approaches to assess the fatigue strength of welded joints: Radaj’s approach based on fictitious notch rounding and a recently proposed approach based on the local strain energy density (SED) averaged over a given control volume. This volume surrounds the weld root or weld toe, both modelled as sharp (zero radius) V-notches with different opening angles. The two approaches are applied to load carrying and non-load carrying cruciform joints and the theoretical fatigue notch factors Kf are compared. The SED averaged over the control volume is determined from finite element models with very fine meshes, as typically designed to evaluate the intensity of the asymptotic stress distributions, and also from coarse meshes, showing a surprisingly good correspondence.

Abstract: This study performs an electrochemical experiment to quantitatively evaluate the corrosion resistance performance in a Zn-Al thermal metal spraying method and produces corrosion current density according to the type of corrosion resistance methods. In the results of the calculation, the corrosion membrane produced in a Zn-Al thermal metal spraying method showed voltage differences more than 300 mV and that demonstrated enough corrosion performance with the corrosion resistance reaction of base materials and proper Zn-Al ratio, such as 50:50. Also, the results exhibited that the corrosion speed in a Zn-Al thermal metal spraying method was 0.66 time faster than that of the zinc galvanizing method in the estimation based on the standard of corrosion resistance service years in a zinc galvanizing method (JIS H 8641).

Abstract: Electromechanical products such as electrical toothbrushes and robots carry multitechnological characteristics, and functional operation of these systems is depended on the successful operation of all system components. There are interactions between electronic and mechanical components, software and other systems in complex products. These interactions such as heat, vibration, gravity, corrosion and electromagnetism can lead to functional and financial losses and failures of these kinds of products. The physical arrangement and mutual relation of subsystems and parts are very important to design reliable and robust systems. However, designing these products is complicated and time-consuming due to limitations on available expertise, tools, and methods. This paper presents a new product development approach proposed for integrating mechanical design with electronic design to improve design and manufacture of electromechanical products in terms of customer requirements, reliability, structural integrity, weight, cost and time. This approach has been implemented in a Delphi based environment integrated with a CAD system. It assists in evaluating complex systems as far as parts relation and their possible effects on each other, costs, weight and physical constraints are concerned in the early design process. This helps the designers to avoid design iterations, and minimize the likelihood of failures and rapidly develop reliable complex products subject to given constraints.

Abstract: The present paper is aimed at investigating the behaviour of fatigue cracks emanating from sharp V-shaped notches. To this purpose, several tests has been conducted on Al-7075-T651 notched specimens using a servohydraulic machine by changing the directions and levels of the applied load. The crack growth have been interpreted on the basis of a linear elastic fracture mechanics approach by adopting a weight function derived by the authors for the calculation of the stress intensity factors (SIFs) of inclined edge-cracks emanating from V-shaped notches.

Abstract: In recent years, the friction coefficient decline in the joints of steel structures caused by corrosion has drawn public attention. Therefore, this study investigated the friction coefficient and surface roughness of high tension bolt joints using a Zn/Al metal spraying corrosion resistance method to estimate the application possibility of the Zn/Al metal spraying corrosion resistance method on the joints of steel structures. According to results, the friction coefficient of Zn/Al metal spraying was 0.50 or more. In addition, the friction coefficient increased according to the decrease in surface roughness (Sm/Rz). Therefore, the Zn/Al metal spraying is applicable to a corrosion resistance method for high tension bolt joints.

Abstract: The purpose of this study is to obtain basic data on the properties of the development of lightweight concrete containing a foam agent for various applications. This experiment confirmed that compressive strength increased specific gravity, by changing the foam agent into a variable and measuring the compressive strength of concrete.