Effect of Electroless Ni-P Plating on the Fatigue Strength of Dilute Al-Si Alloys

In this study, the effect of electroless Ni-P plating on the fatigue strength of dilute Al-Si alloys was investigated. As results, the following points were clarified. Fatigue strength of the specimen subjected to zincate treatment only after furnace cooling treatment was almost the same as the furnace cooling only. Fatigue strength of the specimen subjected to Ni-P plating after furnace cooling treatment, was reduced overall, except for high-stress region, rather than one of non-processing materials. Fatigue strength of the specimen subjected to Ni-P plating after aging treatment showed a clear increase in comparison with one of non-processing materials. Breaking elongation of the specimen subjected to Ni-P plating after aging treatment showed no significant changes in comparison with one of non-processing materials. On the other hand, breaking elongation of the specimen subjected to Ni-P plating after furnace cooling treatment reduced by half in comparison with one of non-processing materials. Especially, it seems that poor fatigue strength and ductility of plating materials are mainly caused due to interaction between surface precipitates and hydrogen gas.

Optimization of the Compositions of PEG/PMMA Binder System in Ceramic Injection Moulding via Water-Debinding

In this study, we have made a comprehensive investigation on optimization of the compositions of PEG/PMMA binder system for water-debinding. An orthogonal test was designed and L9(33) table was chosen to investigate the influence of the molecular weight of low molecular PEG (L-PEG), high molecular PEG (H-PEG) and the percentage of L-PEG in PEGs on flaws of the injection moulded compacts after water-debinding. In addition, the ratio of PMMA content to PEGs content on flaws is also investigated. Four regions were defined as high stress region, safe debinding region, low binder removal rate region and unavailable injection region respectively. It is believed that our work could provide comprehensive and convincing principles for the manufacturing of injection-moulded ceramic parts via water-debinding.

Texture Formation by the Compression Deformation of AA5182 Aluminum Alloy at High Temperatures

Texture formation of AA5182 for compressive deformation with a range of temperatures from 673K to 823K and strain rates from 5.0×10-4to 5.0×10-2s-1is experimentally investigated by EBSD technique and X-ray diffraction. Fiber textures are observed in all deformation conditions. Stress regions are divided into a low stress region (10~55MPa) and a high stress region (above 55MPa) on the basis of the relationship between stress and grain size. In the low stress region, it is found that the main component of the fiber texture is {001}(compression plane). In this case, the pole density at {001} is increased with increasing temperature at the same stress level. It is concluded that development of {001} component is attributed to grain boundary migration. For the high stress region, the main component of the fiber texture is {011}. It is considered that the formation of {011} component is attributed to the slip deformation by {111}<110> system.

Effects of Organophosphate Insecticides on Mechanical Properties of Rat Aorta

The present study was carried out to search whether organophosphate pesticides affect the mechanical properties of the thoracic aorta. Wistar female rats (aged 6-8 weeks) were assigned randomly to a control group and groups treated with either dichlorvos or chlorpyriphos for 90 days at a dose of 5 mg/kg/day. After that period, animals were killed and thoracic aorta strips in longitudinal direction were isolated. The stress, strain and elastic modulus were obtained from the strips. Our results showed that chronic administration of chlorpyriphos and dichlorvos caused downward shift of the stress-strain relations compared to the control curve. The elastic modulus-stress curve revealed distinct characteristics in the low and high stress regions. A power function was used to simulate the low stress region while a line was fit to the high stress region. Curve fitting procedure illustrated that both pesticides influenced mainly the high stress region, but they had diverse effects at the low stress region. The results also imply that chlorpyriphos and dichlorvos decrease the strength of the aorta and therefore might influence the response of the aorta to mechanical loading induced by blood pressure.

The Effect of Adhesive for Fillet on Stress in Weld-Bonded Joints

The influence of the fillet with different elastic modulus on the stress distributed in weld-bonded aluminum alloy single lap joint was investigated using elasto-plastic finite element method. The results show that the peak values of the stress along the mid-bondline at the points near the fillet edge were increased as the elastic modulus of the fillet increased. But at points near the both ends of the adherend in over lap zone as well as in the region of the nugget the peak stresses were decreased except longitudinal stress Sx. The peak value of Seqv decreased first, and then it increased again as the elastic modulus in fillet increased. The load-bearing capacity of the whole weld-bonded joints may be improved for the fillet with Adhesive B (825 MPa) for the relative high stress region in nugget was wider and the stress distribution in overlap zone was more uniform.

Effect of Boron Addition on Creep Strength in 9Cr-3W-3Co-V-Nb Steels

Recently, boron is being added to high-strength steels for boilers and turbines in order to raise creep strength. However, there are various points that are not yet fully understood with regard to the creep-strengthening mechanism of boron addition. In order to investigate the influence of boron addition on creep strength, varying the amounts of boron and nitrogen were added in 9Cr-3W-3Co-V-Nb steels tempered two different conditions and investigated. Although creep strengths of all materials converged to become similar in the low-stress region, the materials tempering at 780°C with boron addition which exhibited the lowest strength on the high-stress region is seen to have slightly greater strength on the low-stress region. In analysis of the precipitates and grain boundary of creepruptured material conducted using TEM-EDS and Auger diffraction analysis equipment, the presence of boron could not be detected.