Progresses in Fracture and Strength of Materials and Structures

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Authors: Xin Ling Liu, Wei Fang Zhang, Chun Hu Tao
Abstract: Twelve transmission shafts were developed unilateralism torsion fatigue tests. Macroscopic and microscopic fracture features of transmission shafts were observed and analyzed. No defect was found in the origin which was usually located at the bolt bores or nearby the bolt bores because of the stress concentration. Using the fractography quantitative analysis technology the propagation life, the origination life and the relation curve between the crack length and the cycle numbers for all of the twelve shafts were estimated. For only one origin on the fracture surface the total life of the shaft with two expanding directions is usually obvious longer than that with one expanding direction, but the main propagation life is obvious smaller. However for two origins and two expanding directions on the fracture surface the total life of the shaft is usually shorter.
Authors: Xiao Qiang Du, Zhe He Yao, Zi Chen Chen
Abstract: Wavelet denoising method was introduced to improve the validity of identifying the guide rail irregularity in elevator. The horizontal acceleration signal measured from a test elevator was processed by wavelet denoising. Then the denoised signal was decomposed up to four levels using Daubechies 4 mother wavelet to identify the guide rail irregularity. The results indicate that the impulses due to the guide rail irregularity are prominent in wavelet decompositions. And the causes resulting in those characteristics of the vibration signal can be well revealed. So discrete wavelet transform (DWT) can be used as an effective tool for denoising the horizontal vibration signal of elevator and diagnosing faults in the guide rail.
Authors: Dae Seock Shin, Heung Shik Lee, Chong Du Cho, Jong Ho Shin
Abstract: An enhancement to pre & post processing techniques, which is encapsulated in ‘Tunnel Modelling Wizard (TMW)’ for three dimensional tunnel analysis, is developed and described in this paper. The techniques include geometry modelling, mesh generation, virtual transformation, flying view and utilization and interpretation of analysis results. The TMW automatically generates full analysis data including mesh, loads, boundary conditions and construction stages from the user-defined parameters. The TMW also provides its own file I/O service to help users expedite modelling tasks for similar models and build their own tunnel templates. Implementation of the TMW into a FE Program is described, and applications of the TMW to practical tunnel problems will be demonstrated.
Authors: Jun Hyub Park, Sung Il Chu, Hyeon Chang Choi
Abstract: This paper represents the development of 3-axises loadcell for measuring the side-force of the suspension module of MPV (Multi Purposed Vehicle). The side force causes the failure of damper, such as leakage. The loadcell was developed using strain gauges, and the Wheastone bridge circuit to compensate for the cross-talk between each axises and the measurement error by temperature. Structure analysis of loadcell was accomplished with FEM (Finite Element Method) to optimize the location of strain gages. The design optimization for the important factors that have effects on performance of loadcell was accomplished by using DOE (Design of Experiment). Loadcell was produced and successfully tested, showing good sensitivity and low cross-talk. The cross-talk of the developed loadcell is below 2%. The measured history using the manufactured load cell will be utilized in the vibration, and fatigue analysis in the future.
Authors: Dong Ho Bae, Yeong Sin Kim, Gyu Young Lee
Abstract: In order to establish a reasonable and integrated fatigue design criterion for the long life design of the gas welded body structure, stress distribution around the gas welded joints subjected to tensile load was numerically analyzed. And also, the P-Nf curves were obtained by fatigue tests. By using these results, P-Nf curves were rearranged in the σ-Nf relation with the hot spot stress at the welded joint. And a guideline for fatigue design of gas welded joints was proposed.
Authors: Dong Ho Bae, Sol Bin Lee, Sun Kyu Park
Abstract: In order to develop a fatigue design method for the actual railroad car body structures using the fatigue data on simulated single spot welded lap joints, firstly, evaluated fatigue strength on the spot welded t-type member which is a component of the actual railroad car body structure. And next, possibility of fatigue design for spot welded T-type member using the fatigue data of single spot welded lap joints was investigated. From the results, it was found that, even though there is some difference in fatigue strength between single spot welded joint and the actual members under the same fatigue life, the fatigue design criterion could be predicted by correction between them.
Authors: Yong Hong, Byeong Hee Han, Dong Pyo Hong, Sung Mo Yang, Young Moon Kim, Kyeong Suk Kim
Abstract: This paper describes a primary study for a new method of enhancing measurement with using an impedance analysis method that is applied to structural health monitoring. The goal of this research is to show basic information that is used to evaluate the structural health condition with using piezoelectric sensors. We present a study for the development of a practical and quantitative technique for the assessment of the structural health condition with using a piezoelectric impedance-based technique that is associated with longitudinal wave propagation. The natural frequency has a tendency of frequency shifting with respect to the hole size that corresponds to the real structure’s crack size. To numerically estimate the damage condition, we suggest the Cov (Covariance) and CC (Correlation Coefficient) evaluation methods.
Authors: Yong Hong, Su Hyun Han, Jae Jung Lee, Dong Pyo Hong, Young Moon Kim
Abstract: In the study, the development of aerial platform truck of 42m boom system has been completed to be satisfied with working in much higher place. To avoid the rollover accident of vehicles while working, 3D FEA is applied to verify the 3D design, stress concentration, stress distribution, deflection, natural frequencies etc. In these analyses, traction load of Boom System, 700 Kg and traction degree analyzed to 0° ~ 85°. Analysis result, when Boom System's angle is 0°, could know that stress concentration and deflection are obtained to maximum. We could predict that maximum point of Stress concentration is 3.275 as safety factor and deflection of Boom system end part is max. 78.5Cm. Also could know that natural frequency and mode shape of boom system are stable in correlation with aerial platform truck's operation area. With these results, the structural stability of boom system in 42m aerial platform truck is obtained, then finally trying to find an optimum design of aerial platform truck.
Authors: Byung Tak Kim, Seon Jin Kim, Sung Wi Koh, H.J. Kim
Abstract: In this study, finite element analyses for the mechanical behaviors of a power steering hose assembly during the swaging process were performed in order to investigate the stress level of hose components according to jaw strokes, and to examine the effect of friction coefficient on the contact force. The physical properties such as Mooney-Rivlin constants of rubber materials and the work-hardening data of the steel were obtained through the experiments, and the contact conditions identical to the swaging process were taken into account. Two reinforced layers included in the hose were modeled with axisymmetric rebar elements in the general-purpose program, MSC MARC2000. The updated Lagrange formulation and the large displacement option were employed in the analysis. The result interpretations were focused on the rubber components which are in contact with the metal components, because of their important roles in the hose efficiency.
Authors: Haruo Sakamoto
Abstract: This paper describes codes and practice for designing welded structures such as railroad truck frames. For designing an initial configuration, rather simple criteria are desired, although most codes such as AWS, AISC, etc. are complex. They consist of a variety of welded joint categories, which make a designer feel difficult when deciding the initial configuration. Therefore, such codes are considered to be mainly used for the evaluation of designed and constructed structures, and not to be used for deciding the initial configuration. The JIS (Japanese Industrial Standard) for a railroad truck frame is explained as an example of a simple code, and is compared with some fatigue data. This standard is thought to be useful for a designer. However, the result of this investigation suggests a modification of the JIS for obtaining more reasonable criteria. Desirable criteria should be simple for a designer and sufficiently safe for structures. Additional fatigue data of welded joints, a statistical study for desirable non-fracture probability, and methods of structural stress analysis are to be researched in the future. A practical fatigue testing method is also needed for investigating the strength in a high cycle region such as 108.

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