Key Engineering Materials Vols. 385-387

Abstract: It is well known that carbonation will result corrosion of steel reinforcement in reinforced concrete structures. To reduce the rate of carbonation, the surface coatings, such as mortar finish, has been used widely to concrete. This paper presents a numerical procedure about carbonation of the coating-concrete system. This numerical procedure starts with a multi-component hydration model. By hydration model which considers both and Portland cement and pozzolanic reaction, the amount of hydration products which are susceptible to carbonate as well as porosity is obtained as function of age. Furthermore, the diffusivity of CO2 is determined and carbonation depth of concrete is predicted. Parameter studies are performed to show the influence of composition and application time of mortar finish on carbonation depth of substrate concrete.

Abstract: Titanium has widely been used as a biomaterial because of its excellent corrosion resistance and biocompatibility. However, problems with respect to biological reaction and fitness of elastic modulus for human bone or tooth have yet to be solved. Porous titanium is expected to be a promising material to solve these problems. The aim of this study is to clarify the effect of the porous structure of this material on the biomechanical compatibility. The spherical pure titanium powder, with an average particle size of 100 µm, was sintered by spark plasma sintering. The sintered porous titanium compacts had a porosity of 33 %. The specimens were machined from the sintered compacts for the evaluation of the mechanical properties. The elastic modulus indicated a value close to human bone, while the tensile and compressive strengths showed lower values than those of human bone.

Abstract: The plastic zone size (PZS) at the tip of a crack emanating from stress concentrators subjected to uniform tension was calculated based upon the Dugdale model. A method was proposed for the prediction of fatigue notch effects in terms of the McEvily method that has widely been used for the analysis of small fatigue crack growth. In modifying this method, the elastic-plastic effects due to stress concentration were taken into account using the values of PZS calculated in this study. The results predicted by this method accounted successfully for the behavior of small fatigue cracks near the threshold levels observed in the fatigue tests conducted using notched steel specimens.

Abstract: This paper describes the results of structural analysis and loading test of a bogie frame. The purpose of the analysis and test is to evaluate the safety and functionality of the bogie frame under maximum load. The bogie system consist of the bogie frame, suspensions, wheel-sets, a brake system and a transmission system. Of these components, the bogie frame is the major component subjected to the vehicle and passenger loads. The evaluation method used the JIS E 4207 specifications throughout the FEM analysis and static load test. The test results have shown the bogie frame to be safe and stable under design load conditions.

Abstract: Fatigue life of automotive engine mount insulator made of natural rubber was evaluated. In order to develop an appropriate fatigue damage parameter of the rubber material, a series of displacement controlled fatigue tests was conducted using 3-dimensional dumbbell specimens with different levels of mean displacement. It was shown that the maximum Green-Lagrange strain was a proper damage parameter, taking the mean displacement effects into account. Nonlinear finite element analyses of the rubber engine mount insulator and 3D dumbbell specimen were performed based on a hyper-elastic material model determined from the simple and equi-biaxial tension tests. Fatigue life prediction of the engine mount insulator was made by incorporating the maximum Green-Lagrange strain values, which was evaluated from the finite element analysis and fatigue tests, respectively. Predicted fatigue lives of the engine mount insulator showed a fairly good agreement with the experimental fatigue lives.

Abstract: The structural strength during static loadings for a carbody of railway container freight car was evaluated to verify the structural strength of newly manufactured carbody. The carbody of freight car was designed with SM490YA steel and stainless steel for the general railway transportation. Prior to the assessment of structural strength, finite element method (FEM) characterization was used for the stress and structural analyses on stress distribution in a carbody of container freight car. The strain gages were attached on the carbody based on the FEM results in order to measure structural strength during static loadings such as vertical and compression loadings. The actual vertical loading test and horizontal compression loading test were conducted, and the results were compared with the previous FEM results. In this investigation, the evaluation method for the structural strength in a structural component has been introduced using several engineering techniques, and experimental and theoretical results were compared.

Abstract: To develop a durability design procedure based on lifetime safety factor method, different dose-response functions based on both ISO standards and the literature are presented for the prediction of the thickness loss due to atmospheric corrosion in metal structures. Finally, serviceability and ultimate limit states are defined for the durability design against corrosion.

Abstract: This paper presents a model for chloride diffusion in cracked concrete. This numerical model includes two parts: hydration model and chloride diffusion model. The hydration model starts with mix proportion of concrete and considers both Portland cement hydration and pozzolanic activity. By hydration model, the evolution of properties of cement paste is described as function of curing age. Furthermore, based on general effective media theory and composite spheres assemblage model, the effective diffusivity of chloride ions in concrete without crack is obtained. Finally based on crack distribution in cracked concrete and finite element methods, the diffusion of chloride ions in cracked concrete is predicted. The prediction results agree well with experiment results.

Abstract: Cathodic Protection Method was introduced as a corrosion protection method of metals under the ground or sea. Since 1970, it was applied to corrosion protection method of reinforced concrete structures. After 1990, this method has been used around the world, and its usability was proved. But this method has some problems on the aspect of construction and economy. In order to solve these problems, Cathodic Protection Method by using high durable metal spray was developed. First, the specimen was covered with anodic materials (Zn, Al) by using metal spray. And a performance of corrosion protection was confirmed by measuring corrosion current and halfcell potential of specimen. Through the result of experiment, it is possible to know that Cathodic Protection Method by using high metal spray is good protect to corrosion on reinforced concrete structures.

Abstract: Damage evolution due to generation of hot spots on railway brake disc was investigated using the infrared thermography method. A brake disc with gray cast iron, which is currently used in Korea, was employed for this investigation. A high-speed infrared camera was used to measure the surface temperature of brake disc as well as for in-situ monitoring of hot spot evolution. From the thermographic images, the observed hot spots and thermal damage of railway brake disc during braking operation were qualitatively analyzed. Moreover, in this investigation, the previous experimental and theoretical studies on hot spots phenomenon were reviewed, and the current experimental results were introduced and compared with theoretical prediction.