Papers by Keyword: Stress Relief

Abstract: We investigated the effect of Si wet etching on the vertical step at wafer edge. We found that the concave-convex shape appeared at the wafer edge after Si etching by the Atomic Force Microscopy analysis. From the liquid simulation and the detailed evaluation of Si etching rate, we revealed that the concave-convex shape was formed by the distribution of the fluid velocity at the wafer edge.

Abstract: Residual stresses developed after quenching of high-strength aluminum alloy ultra-thick plates have an important effect on the quality and reliability of parts, and should be reduction to meet the requirement. In this investigation, numerical techniques of SIMUFACT software are used to simulate residual stresses in quenched 340mm×127mm×124mm Al-Zn-Mg-Cu high-strength aluminum alloy ultra-thick plate, and the results have been verified. On the basis of verified simulation parameters, residual stresses in quenched 4000mm×720mm×285mm ultra-thick plate and their reduction through single-side cold compression method were simulated by SIMUFACT software. After quenching, the value of maximum tension stress located at the interior center of the plate is 200MPa, and the value of maximum compression stress located on the surface of the plate is-169MPa. Through analysis of single-side cold compression processes, it can be concluded that more than 90% quenching residual stresses can be reduced by 1% upsetting ratio and 75% feed of the top die. Residual stresses after compression can be reduced down to the range of-25~9MPa. Mean residual stress values of simulation after compression are identical to the XRD testing data.

Abstract: Nowadays, electroencephalogram (EEG) is widely used in medical applications. Besides the examination for brain diseases, EEG is used to observe how the surroundings affect peoples emotion. There are many essential oils, and most claim that they are effective in soothing soul and calming. Currently, there is no related EEG scientific experiment to verify this claim, This study attempted to understand whether common essential oils for stress relief have actual emotional relaxation effects on the human brain by EEG observation; the level of efficacy was also observed. From the results of this study, rose essential oil had the best effect of stress relief and relaxation in both genders (P<0.05). It suggested that peppermint essential oil had the best effect of relaxation in male (P<0.05) and rose essential oil had the best effect of relaxation in females (P<0.05) when it was analyzed by gender.

Abstract: The paper discusses the contributing factors of dike failure occurred during construction of the diversion ditch. It is concluded that composition of ground and effect of the groundwater are physical element of slide, soil from ditch excavation placed on the top of flanking slopes for embankment and stress-relief at the foot of flanking slope by excavation are induced factors.

Abstract: In recent semiconductor industry, production of ever flatter, thinner and larger Si wafer are required to fulfill the demands in high integration and cost reduction. A severe problem encountered in wafer thinning process is the warp and distortion of wafer induced by the residual stress and subsurface damage. Chemo-mechanical grinding (CMG) process is emerging process which combines the advantages of fixed abrasive machining and chemical mechanical polishing (CMP), offers a potential alternative for stress relief. This paper studies the influence of the wheel manufacturing process on the wheel physical properties. Three-factor two-level full factorial designs of experiment are employed to reveal the main effects and interacted effects of mixing method and filtration of raw materials on the bending strength and elastic modulus of CMG wheel. The difference in wheel properties is discussed by association with CMG performance including wheel wear, grinding force and surface roughness.

Abstract: Simultaneous saccharification and fermentation is an attractive process configuration for bioethanol. However, the process cost in SSF is still high. Further reductions in cost are expected with reduction of enzyme addition and the use of waste agricultural or industrial materials as feedstock. Surfactant addition is a simple method to reduce the amount of enzyme loading. In the present work we explore the effect of Gleditsia Saponin, an inexpensive and natural surfactant, on SSF of furfural residue, a main waste of furfural industry in China, for ethanol production. Gleditsia Saponin addition even at low concentration, 0.04 g/l, increased the ethanol yield by 9.9%. Meanwhile, when Gleditsia Saponin addition was 0.16 g/l, the yield was increased by 22.8% and the enzyme activity significantly increased in the liquid fraction at the end of SSF, which would contribute to recover and recycle enzyme. Gleditsia Saponin addition at 1.25 g/l had a better performance in improving SSF efficiency than that of 2.5 g/l Tween-20 addition. The positive effects of Gleditsia Saponin addition on SSF, such as less enzyme loading and shorter residence time could also been observed.

Abstract: Corn stover was pretreated using different soaking conditions at mild temperature. Among the tested conditions, the best was 1% NaOH+8% NH4OH，50°C，48 h, Solid-to-liquid ratio 1:10. The results showed that soaking pretreatment achieved 63.6% delignification, retained the xylan and glucan. After enzymatic hydrolysis, conversion rates of xylan and glucan were 70.9% and 78.5%, respectively. The pretreated filtration re-soaking cause 52.7% xylan and 65.0% glucan conversion. NaOH+NH4OH treatment can be performed under mild conditions, gives a good buffering effect, low carbohydates degradation and extensive removal of lignin. Additionally, simultaneous saccharification and fermentation was conducted with pretreated corn stover to assess the ethanol production. For the whole process, 0.15g ethanol /g corn stover was achieved using Saccharomyces cerevisiae Y5, and 0.19g ethanol /g corn stover when using Pichia stipitis.

Abstract: In this study, research work on the effects of vibrational energy on the microstructure of welds and Charpy toughness is performed. The results show that vibration during welding exhibits positive effects on the microstructure constituent formation by reducing the amount and thickness of grain boundary ferrite and suppressing the formation of the Widmanstatten structure. And also due to the finer microstructure developed by the vibration, toughness value of the weld metal increases.

Abstract: ASTM A106/B is commonly used for pressure piping in alumina refineries. Due to the problem of caustic cracking in alumina refineries, piping must be stress relieved after welding, usually through a post-weld heat treatment (PWHT) process at a temperature of 635°C. However, multiple PWHT procedures tend to degrade the mechanical properties of steel and design standards have set limits on the length of time PWHT can be carried out before steel should be replaced. In this study, the effect of PWHT time on the properties of A106/B parent metal was examined, with particular emphasis on the effect on toughness. PWHT was carried out for 1, 8 and 40 hours and the results were compared with those for as-received material. Impact transition temperature and room-temperature tensile results were determined using standard tests. The reference temperature, To, was determined using ASTM E1921 with arc-shaped tension specimens. The results showed that the ductile-to-brittle transition temperature increased significantly as PWHT time increased and the implications of this to a fracture mechanics analysis of plant operations are discussed.

Abstract: Neutron scattering using diffraction techniques is now recognised as the most precise and reliable method of mapping sub-surface residual stresses in materials and industrial devices. It was therefore decided to build the dedicated strain scanner KOWARI among the first suite of instruments for the new Australian Replacement Research Reactor OPAL. In order to support the new instrument and familiarize the Australian user community with the technique a „Neutrons for Engineering“ project has been established to provide a fully integrated residual stress service. To make use of the neutrons at Australias HIFAR reactor the existing three-axis spectrometer has been refurbished and modified to allow strain measurements. The Australian Strain Scanner (TASS) will operate until the new strain scanner becomes operational in 2006. Apart from giving an overview about the technique and properties of the new strain scanner we would like to present and discuss two case studies: a) residual-stresses obtained from a break-disc of a car and b) residual-stresses within a flash-butt welded plate cut out of a railway.