In the present paper, the aluminum alloy i.e. LM6 based composites reinforced with different weight fraction of SiC particles was produced by stir cast technique and the effect of reinforced ratios on the forgeability...In the present paper, the aluminum alloy i.e. LM6 based composites reinforced with different weight fraction of SiC particles was produced by stir cast technique and the effect of reinforced ratios on the forgeability and the machinability was examined. The test results show that the increment in weight fraction of reinforcement particles in the matrix metal produced better mechanical property like hardness but the forgeability of the cast MMCs decreases. The forgeability of the as cast MMCs were also varied with the change in thickness of the casting. The results show that the forgeability of cast metal matrix composites at the mid section of the casting is minimum compared to both end section of a three-step casting. The effect of machining parameters, e.g. cutting speed and depth of cut on the surface roughness and cutting forces at constant feed rate was investigated during experimentation. The results show that higher weight percentage of SiCp reinforcement produced a higher surface roughness and needs higher cutting forces during machining operation. It has also observed that the depth of cut and the cutting speed at constant feed rate affected the surface roughness and the cutting forces. This practical research analysis and test results on the forgeability and machinability of Al/SiC-MMC will provide useful guidelines to the present day manufacturing engineers.展开更多
In order to realize cold forging of magnesium alloys in practical application,some methods for ductility improvement of a commercial wrought AZ31B magnesium alloy(Mg-3%Al-1%Zn,mass fraction) at room temperature were s...In order to realize cold forging of magnesium alloys in practical application,some methods for ductility improvement of a commercial wrought AZ31B magnesium alloy(Mg-3%Al-1%Zn,mass fraction) at room temperature were suggested.The effects of heat treatment before forging and hydrostatic pressure during forging on the ductility were investigated in cold upsetting and cup forging.High-temperature annealing was effective to reduce the degree of the texture anisotropy of the specimen,and it was found that the forging limit of the annealed specimen was improved in cold forging.On the other hand,cold cup forging of the annealed specimen was carried out with applying counter pressure.By applying counter pressures of 100-200 MPa during forging,the critical punch stroke for forging limit of the specimen without crack was improved by 25%in punch stroke.展开更多
The security of Canard-Traore fair e-cash system scheme was believed to depend on the strong-RSA assumption and the Decision Diffie-Hellman assumption in groups of unknown order. But it is not the case. The cryptanaly...The security of Canard-Traore fair e-cash system scheme was believed to depend on the strong-RSA assumption and the Decision Diffie-Hellman assumption in groups of unknown order. But it is not the case. The cryptanalysis on Canard-Traore fair e-cash system was presented. An algorithm was designed to show that Canard-Traore fair e-cash system is insecure: It is forgeability. Further, two drawbacks on Canard-Traore fair e-cash system scheme were pointed out. One is that those integer intervals for si（i=1,…,9） are unappropriate. The other is that the datum s3 in signature data is redundant. Moreover, a minute description of the technique to shun the challenge in the scheme was presented. The technique is helpful for designing new group signature schemes in the future.展开更多
文摘In the present paper, the aluminum alloy i.e. LM6 based composites reinforced with different weight fraction of SiC particles was produced by stir cast technique and the effect of reinforced ratios on the forgeability and the machinability was examined. The test results show that the increment in weight fraction of reinforcement particles in the matrix metal produced better mechanical property like hardness but the forgeability of the cast MMCs decreases. The forgeability of the as cast MMCs were also varied with the change in thickness of the casting. The results show that the forgeability of cast metal matrix composites at the mid section of the casting is minimum compared to both end section of a three-step casting. The effect of machining parameters, e.g. cutting speed and depth of cut on the surface roughness and cutting forces at constant feed rate was investigated during experimentation. The results show that higher weight percentage of SiCp reinforcement produced a higher surface roughness and needs higher cutting forces during machining operation. It has also observed that the depth of cut and the cutting speed at constant feed rate affected the surface roughness and the cutting forces. This practical research analysis and test results on the forgeability and machinability of Al/SiC-MMC will provide useful guidelines to the present day manufacturing engineers.
基金supported in part by the Japan Ministry of Education,Culture,Sports,Science and Technology,with Grant-in-Aid for Young Scientists(B)
文摘In order to realize cold forging of magnesium alloys in practical application,some methods for ductility improvement of a commercial wrought AZ31B magnesium alloy(Mg-3%Al-1%Zn,mass fraction) at room temperature were suggested.The effects of heat treatment before forging and hydrostatic pressure during forging on the ductility were investigated in cold upsetting and cup forging.High-temperature annealing was effective to reduce the degree of the texture anisotropy of the specimen,and it was found that the forging limit of the annealed specimen was improved in cold forging.On the other hand,cold cup forging of the annealed specimen was carried out with applying counter pressure.By applying counter pressures of 100-200 MPa during forging,the critical punch stroke for forging limit of the specimen without crack was improved by 25%in punch stroke.
文摘The security of Canard-Traore fair e-cash system scheme was believed to depend on the strong-RSA assumption and the Decision Diffie-Hellman assumption in groups of unknown order. But it is not the case. The cryptanalysis on Canard-Traore fair e-cash system was presented. An algorithm was designed to show that Canard-Traore fair e-cash system is insecure: It is forgeability. Further, two drawbacks on Canard-Traore fair e-cash system scheme were pointed out. One is that those integer intervals for si（i=1,…,9） are unappropriate. The other is that the datum s3 in signature data is redundant. Moreover, a minute description of the technique to shun the challenge in the scheme was presented. The technique is helpful for designing new group signature schemes in the future.
