Advanced Materials Research Vols. 538-541

Abstract: Increasing demand for reliable design of all kinds of structures requires materials properties evaluated under the conditions as close to real service conditions as possible. Presently resolved project dealing with development of new turbine blades geometry requires better understanding of the material behavior under service conditions. Service conditions of turbine blades are cyclic loading at high temperatures under superheated steam conditions. There are not commercially available testing systems providing such functionality and the system allowing samples loading under considered conditions is to be proposed. The paper deals with development of the testing equipment and testing procedure for high cycle fatigue tests in superheated steam corrosive environment. The system allowing cyclic loading at temperatures up to 650°C under superheated steam conditions was successfully designed, assembled and tested on series of testing samples.

Abstract: In this paper a 2D boundary element model is used to characterize the transient response of a piezoelectric based structural health monitoring system for cracked beam. The BE model is written for piezoelectric non-homogeneous problem employing generalized displacements. The dual reciprocity method is used to write the mass matrix in terms of boundary parameters only. The multidomain boundary element technique is implemented to model non-homogeneous and cracked configuration, unilateral interface conditions are also considered to prevent the physical inconsistence of the overlapping between interface nodes belonging to the crack surfaces. To assess the reliability and the effectiveness of the model numerical analyses are carried out on the modal and dynamic response of undamaged beam and results are compared with finite element calculations. Electrical response of piezoelectric sensors are then reported for different crack configurations in comparison with the undamaged case.

Abstract: This study deals with effects depending on skew angles in skewed-laminated composite materials in macroscopic point of view. Based on higher-order approximation of displacements, subparametric layer-wise finite elements are used to analyze skewed-laminated composite systems. The elements have higher-order shape functions derived from the Lobatto shape functions. The modes of the elements are classified into three groups such as vertex, side, and internal modes. The vertex modes have physical meaning, while side and internal modes with respect to the increase of order of the Lobatto shape functions do not have physical meaning but improve accuracy of analysis. Therefore, fixing mesh arrangement of present analysis, the quality of the analysis can be enhanced without re-meshing work. The approach based on p-version of finite element method is implemented with three-dimensional elasticity theory, while shape functions are developed by combination of one- and two-dimensional shape functions, not using three-dimensional shape functions. Using the accurate and practical proposed technique, macroscopic behavior of skewed-laminated composite materials is investigated.

Abstract: In the heavy machinery and energy industry, forged connecting rods have been used more and more widely. Due to the complex process and large-size, it is a challenge to ensure the quality of large forgings. Different kinds of defects were produced during forming process. In this study, the forming process of S20S forged connecting rod was first analyzed. Then SEM and energy spectrum were conducted. The results showed that inclusions of sulfide and oxide were the main defects during forging of S20S connecting rod.

Abstract: In this paper, three-dimensional finite-element model for the skew rolling (helical-groove rolling) process has been used to characterize the workpiece material stress,strain and deformation behavior. Particular attention has been paid to representative cross section and the center, edge and mid-radius points of the billet

Abstract: The paper analyzed the key points in design of partially prestressed concrete pier cap beam. Design ideal and design method of partially prestressed concrete pier cap beam were elaborated. Results between deformation and stress were compared. Which shows that partially prestressed is more excellent than fully prestressed in long-span concrete pier cap beam.

Abstract: In this paper, the deformation characteristics of workpiece of different deformation parts was experimented in multi-dimensional loading conditions, The research shows that the metal around active mode follows priority deformation principle when selectable multi-dimensional flowing. Through the analysis of deformation resistance and driving force, the influence factors of selectable multi-dimensional flowing was determined, and the mathematical model of selectable multi-dimensional flowing was established, the theoretical basis of priority deformation in local loading area was provided, a powerful guarantee was provided for precise design multi-dimensional process.

Abstract: Based on measurement data and the specific morphology of corrosion pit, three-dimensional finite element model of the corrosion damage specimen is established. Then the local stress condition of corrosion pits is given making use of finite element method, the results of stress concentration due to corrosion pits are also obtained, we can compare the stress concentration arised from the corrosion pit on aluminum alloy specimens in different corrosion time. Results show that the corrosion pits produce stress concentration and become the source of fatigue crack initiation and propagation. With the increasing of corrosion time, the pits get deeper and deeper, and the stress concentration gets more serious near the pits.

Abstract: Four different heat treatment routes which were called step quenching were taken and accordingly different morphology dual-phase samples have been obtained. It is found that Maximum shear stress increases with martensite volume increases. They have the following relationship: Maximum shear stress = 1.14(MVF)2 – 90.7(MVF) + 24266 MPa. Adiabatic shear bands and cracks led by them are important signs during the dynamic torsional tests

Abstract: The relation between the microstructure, precipitates and the longitudinal mechanical properties of high strength hot strip was studied by optical microscope (OM), scanning electron microscope (SEM) and transmission electron microscope (TEM). The results showed that the yield strengths of the coil outer and middle parts were higher than that of inner part by 65MPa, and the tensile strength of the coil outer part was higher than that of middle part and inner part by about 50MPa. The number of subgrain with small size and that of dispersion distribution precipitates less than 30nm in outer part and middle part were more than that in inner part, which resulted that subgrain and precipitation strengthening were larger than that of inner part. For the coil inner part, the strengthening effects were made of fine-grained strengthening and M/A islands strengthening. The contribution of subgrain and precipitation strengthening to intensity is larger than that of fine-grained strengthening, which is the main reason causing the outer and middle parts having higher yield strength. The least tensile strength of middle part is related to the many blocky ferrites.