Applied Mechanics and Materials Vol. 786

Abstract: The heat-resistant, copper-alloyed ferritic steel 15NiCuMoNb5 (EN-WB36, material number 1.6368) has been widely used in European nuclear and conventional power plants for decades for feed water system. This widespread application is due to the toughness and strength, caused by the precipitation of copper, that are exhibited even at elevated temperatures which other fine-grained structural steels have at room temperature. The common problem faced on the construction sites is the embrittlement due to Cu-rich precipitates and the high hardness in welded joints that affect the weld quality and the premature joint failure can occur in service. Weld hardness has close relationship with the strength and ductility of the welded structures. Hence it is important for any weld to achieve certain level of weld hardness. The aim of this study is to see the impact of the impact of post weld heat treatment (PWHT) on the welded joints of WB 36 and find the optimal PWHT conditions that will produce the required hardness to overcome the problem of embrittlement in the welded material. Samples of different thicknesses were welded, keeping all the parameters same, PWHT carried out with induction heating equipment, joints were radiographed for any defect, macro-etched to confirm complete fusion and joint free from crack, and the hardness values were measured in base metals, heat affected zones and weld metal. It was found out that the embrittlement of WB-36, due to Cu-rich precipitates and high hardness, in welded joints can be brought into the lower and safer limits by applying PWHT at 570 °C for 1 hour min. This, for sure, will reduce the risk of premature joint failure and will have, comparatively, safer weld joint.

Abstract: The low-cycle fatigue (LCF) behavior specially the fracture initiation mechanism in a cast hybrid metal matrix composite (MMC) was investigated in this research. Conventional three point bending fatigue test was carried out on a rectangular bar smooth specimen. Factographic analysis was conducted to observe the fracture initiation site. Experimental results showed that microcracks in LCF initiated at the particle–matrix interface which was located in the hybrid clustering region. Due to continued fatigue cycling, the interface debonding occurred, created additional secondary microcracks and the microcrack coalesced with other nearby microcracks caused the final fracture.

Abstract: The mechanical properties of weld joints in Friction Stir Welding (FSW) are influenced by the welding parameters such as rotational speed, tool geometry and welding speed. In the present study, three different tool profiles have been used to weld the joints with three different rotational speed and two welding speeds. Full factorial experiments have been conducted using DoE. The mechanical properties of weld joint were evaluated by means of tensile tests and hardness test at room temperature. The experiment result shows that the average highest number of hardness was 40.06 HRB with square tool at a rotational speed of 2000rpm while lowest hardness was 30.84 HRB with cylindrical threaded tool at rotational speed of 1800rpm. The maximum tensile strength of the joint obtained is 265 M Pa which is close to base material strength. It is observed from experimental results that joints made by square tool yield more strength compared to other tool profiles.

Abstract: The fatigue strength on small-specimen of mild steel material subjected to rotating bending load has been investigated. Specimen materials were used AISI 3140 steel. The tests were carried out the specimen diameter of 2 and 1 mm at laboratory air. The results obtained can be summarized that fatigue strength of diameter 2 mm was higher than that of diameter 8 and 1 mm for AISI 3140 steel material. Assessment of fatigue strength in small-specimen of carbon steel material has been done based on experimental and the cross-sectional analysis. Fatigue strength of AISI 3140 steel was lower than that of SS400 and S45C steels. The size effect concentration were determined the ratio of fatigue strength small-specimen to the normative specimen. The cross-sectional A was decrease with increasing coefficient of cross-section size. These results were significant impact of the size effect on fatigue strength on metal materials.

Abstract: The main objective of this experimental study was to investigate the effects of low velocity impact loading on the pressure bearing capacity of the E-glass/epoxy composite pipes. The pipes were produced by the conventional filament winding technique comprises of six axisymmetric layers with (±55°)₃ winding angles. The specimens were impacted at three different energy levels which are 5 J, 7.5 J, and 10 J using an instrumented drop weight impact testing machine (IMATEK IM10). The samples were then filled with water and subjected to burst test until distinct leakage failure is observed. The results indicate that the peak force and contact time increases with increased of impact energy. For impacted samples, the pressure tests show that the burst strength of the pipes decreases with increase in energy levels during impact loading. During the burst tests, several damage types named leakage and eruption were observed.

Abstract: This research discussed on the determination of the appropriate fatigue damage parameter to predict the fatigue life when material subjected to the biaxial loading condition with the consideration of the energy dissipated. Servo-hydraulic machine is used for the constant amplitude cyclic testing on smooth solid mild steel. The results showed that in the low cycle fatigue, the total strain energy density can represent the accumulative of fatigue damage and characterize on the damage parameters. The relationship has been proposed which the data satisfactorily correlated for the R² is 0.8656. In addition, the hysteresis loop represent the area under the graph was the energy stored in the material during the loading and unloading condition. Hence the circumstances showed the deformation process governing the nucleation and propagation of fatigue cracks associated with the energy dissipated.

Abstract: Solder joints failure due to thermal loads and mechanical loads is a significant reliability concern in electronic devices. From literatures, little attention is paid to the development of methods on predicting fracture behavior of solder joint under mixed-mode loading. This paper presents a finite element modeling of intermetallic compounds solder joints failure based on displacement extrapolation method (DEM). Conceptual study on single edge crack on intermetallic IMC solder joints is presented.

Abstract: Solder joints are exposed to drop impact, vibration loading, bending, and twisting of PCBs. Study on this matter will lead to prediction of fracture load, prevalent fracture mode, exact joint interconnect size and life of joints under brittle and fatigue failure. This paper presents a finite element modeling of intermetallic compounds solder joints failure based on displacement extrapolation method. Based on conceptual FE model of intermetallic IMC solder joints, this paper present the full model of IMC model for intermetallic Mode I and Mode II fracture prediction.

Abstract: Bone fracture can occur in all parts of human skeletal cortical bone including phalanx bone of finger bone. Sometime, it leaves permanent damage and a long period of recovery. This situation can be prevented if we understand the mechanics and the process of the bone fracture. This study aims is to evaluate stress shielding induced by crack interaction using a simple model on Linear Elastic Fracture Mechanics (LEFM). Numerical simulation had been carried out in this study to understand the stress shielding induced by crack interaction. The results revealed that the interaction of two cracks is directly proportional to the stress intensity factor (SIF) magnitude at crack tips. Finally, as the crack-to-width ratio increase and the strain energy release rate also increased.

Abstract: Fabrication of an impedance tube for measuring sound absorption coefficient is presented in this paper. Transfer-function method is chosen for the sound absorption analysis. The impedance tube is designed and fabricated in accordance with ISO 10534-2. The tube is made from brass with diameter of 114.3 mm and length of 1.42 m. It is designed for the frequency range 60 Hz to 1800Hz. Three microphone positions are installed to achieve the frequency range with a single tube. The theoretical background of transfer-function method between two microphones is discussed. Initially, impedance tube is characterized by the measurement without testing material in the tube. Micro-perforated panel (MPP) with 50 mm and 100 mm of cavity depth are used for measurement. The sound absorption coefficient measurement of the MPP is compared with theory and good agreement is achieved. Various problems related to design and construction is addressed and the optimal configuration is presented.