FeNiCrCoSi_(x) and FeNiCrCoTi_(x)(x=0,0.3,0.6,and 0.9 wt.%)high entropy alloys(HEAs)were prepared via the powder metallurgy technique.A homogenous distribution of the elements in all alloys due to the formation of a s...FeNiCrCoSi_(x) and FeNiCrCoTi_(x)(x=0,0.3,0.6,and 0.9 wt.%)high entropy alloys(HEAs)were prepared via the powder metallurgy technique.A homogenous distribution of the elements in all alloys due to the formation of a solid solution phase is observed.The density and hardness of the prepared HEAs are improved by Si and Ti additions,compared to FeNiCrCo HEA.The wear rate of the prepared alloys was studied at different loads and the results indicate that the alloys that contain 0.3 wt.%Si and 0.9 wt.%Ti have the lowest wear rates.X-ray diffraction,SEM,and EDX were used to understand the phases,grain sizes,and microstructures in different investigated HEAs.The effects of Si and Ti content on the corrosion behavior and surface morphologies of sintered FeNiCrCoSi_(x) and FeNiCrCoTi_(x) HEAs were studied by immersion in H_(2)SO_(4),HNO_(3),and HCl solutions.Uniform corrosion and localized pitting are observed in different sizes in the corrosive media used.Because of the smaller pit size and the reduced pit density,the FeNiCrCoSi_(0.3) HEA has an excellent microstructure.展开更多
Due to high competition of the agriculture machines sector, the auto parts suppliers are investing in research to promote the development and reduce the costs of the products, passing these results to their clients wh...Due to high competition of the agriculture machines sector, the auto parts suppliers are investing in research to promote the development and reduce the costs of the products, passing these results to their clients who are the automakers. It was identified the need to redesign the regulation sieve system harvester, which is a compound assembly in the harvester＇s grain cleaning system, with the objective to reduce the costs and improve the ergonomic aspect, keeping the same efficiency from the original project. The improvement was developed by studying the original design and identifying possible project fails, such as components and manufacturing process which could be eliminated. For this, it was needed to do a research about rules and project considerations that must be applied in the products development and ergonomic too, specifically about geometric forms and anthropometric measures. From the redesign of this system, it is verified that it is possible by a study to identify possible improvements, and to develop a new system by a simple project, improving the ergonomic, reducing the cost and keeping the same efficacy from the original project.展开更多
In this research study,Bambusa ssp,the utilized species of bamboo,was rendered into a more versatile construction material in the form of laminates.The laminated specimens were manufactured using simplified processing...In this research study,Bambusa ssp,the utilized species of bamboo,was rendered into a more versatile construction material in the form of laminates.The laminated specimens were manufactured using simplified processing methods according to the ASTM D3039 and ASTM D143 standards.Polyvinyl acetate was the adhesive used between the 2-ply laminate.The mechanical properties of the specimens were evaluated through tensile,compressive and bending strength tests according to set standards on the Testometric M500-50AT Universal Testing Machine.The tensile strength of laminated bamboo was comparable to that of redwood,spruce,cedar and pine.The ratio of compressive strength of parallel to perpendicularfibers in compressive tests was in a close range to that of poplar,fir and pine.The correlation in compressive strength values between bamboo and wood confirmed the inherent anisotropic nature of both plant materials.展开更多
Bamboo in its raw state is difficult to incorporate in complex structures due to its tubular shape. In this research article, a novel approach to connect bamboo was designed and evaluated in order to integrate sustain...Bamboo in its raw state is difficult to incorporate in complex structures due to its tubular shape. In this research article, a novel approach to connect bamboo was designed and evaluated in order to integrate sustainable material into modern structures. Several bamboo joints for culm connection were designed based on strength and durability under various loading capacity. The conceptual joints were manufactured and subjected to destructive testing on the Universal Testing Machine, Testometric M500-50AT. From the mechanical properties generated, final modifications and refinements were incorporated into the joint design. Self-drilling metal screw joints were found to be the strongest with a maximum resisting force of around 11 kN in compression and 10 kN in tension. Riveted joints were the second strongest joint, while tightening ring joints, the weakest among the three, could only resist a peak load of 747 N in tension. The joints, designed with metal fittings, proved to be more practical for utilization in assembly design.展开更多
Form error measurement is a critical exercise in providing measures for the quality control in the precision manufacturing industry.Coordinate measuring machine （CMM） is one of the automated systems used in the accu...Form error measurement is a critical exercise in providing measures for the quality control in the precision manufacturing industry.Coordinate measuring machine （CMM） is one of the automated systems used in the accurate and precise dimensional measurements and geometrical form.This paper aims to study the effect of dynamic original unforeseeable errors at different undulations per revolution （UPR） of standard artifact measurement using selected two types of CMM touchtriggering stylus.Stylus-type and stylus-speed parameters were adopted and utilized throughout the course of experiment.The results are analyzed using fast Fourier transformation to obtain foreseeable geometrical errors due to CMM machine structure and stylus scanning speeds.The results of experiment successfully indicate that the number of UPR plays an important role in determining the CMM accuracy level of the roundness measurement result.Some specific error equations for stylus system and machine structure responses have been postulated and analysed to empirically predict the accuracy of PRISMOBridge-CMM-type at National Institute for Standards （NIS） in egypt.展开更多
Power ultrasound is finding widespread applications in assisting conventional processes yielding products of better quality at lower processing power and temperature. Transmission of ultrasound is known to be affected...Power ultrasound is finding widespread applications in assisting conventional processes yielding products of better quality at lower processing power and temperature. Transmission of ultrasound is known to be affected by the boundaries between layers of different materials or same material but in different states （solid or liquid or gas）. This paper investigates the effects of ultrasound （US） on the surface of the solidified weld which has been subjected to ultrasonic vibrations of 20 kHz frequency during laser welding. Vibrations due to ultrasound normally exert a very high force which is usually hundred or thousand times the gravity. The transverse waves will also cause movement of molten material in the weld. As the surface of the weld beads were of interest and not the mechanical properties and the microstructure, investigation of bead on plate welds were found to be sufficient. High carbon steel plate was held at one end by the ultrasonic horn through which ultrasound was injected. A bead on plate weld using a CO2 laser （1 kW） was then performed along the center of the plate using three different welding speeds namely, 400, 1200 and 2000 mm per minute. The ultrasonic powers selected were 3 W and 6 W respectively for each welding speed as higher acoustical power was causing ejection of molten metal from the pool during welding. 3D surface measurements and analysis were then made on a section of length 20 mm using a Talysurf machine. The results show that the surface of the weld was affected to different extent depending on the positions being considered in the weld. Some regions were similar to the reference weld whereas some specific regions were heavily disrupted with deep valleys followed by high peak/s. This shows that US vibration of weld pools, even at very small acoustical power, is a more complex problem than other similar processes such as casting because of the very small volume of molten metal involved.展开更多
Hydroxyapatite （HA） nano-powder was synthesized via wet chemical technique in a used precipitation reaction, in which Ca（OH）2 and H3PO4 were used as precursors. Deionised water was used as a diluting media for the...Hydroxyapatite （HA） nano-powder was synthesized via wet chemical technique in a used precipitation reaction, in which Ca（OH）2 and H3PO4 were used as precursors. Deionised water was used as a diluting media for the reaction and ammonia was used to adjust the pH. The synthetic HA nano-powder has some medical applications such as a coating material in orthopaedic implants and in dental. HA powder has been studied at different temperatures from 100 to 800 ℃ to achieve the stoichiometric Ca/P ratio 1.667. The optimum temperature was found to be 600 ℃. Above this temperature, the HA powder decomposed to CaO. The crystallite size of HA powder was found to be in the range of 8.47-24.47 nm. The crystallographic properties were evaluated by X-ray diffraction, Fourier transform infrared spectroscopy, energy dispersive X- ray spectroscopy and scanning electron microscopy. The results show that, high purity of nano-hydroxyapatite powders could be obtained at low temperatures, and the crystallinity, crystallite size and Ca/P ratio of the resulting nanoparticles were found to be dependent on the calcination temperature. When Ca/P ratio exceeded 1.75, formation of CaO phase was observed.展开更多
文摘FeNiCrCoSi_(x) and FeNiCrCoTi_(x)(x=0,0.3,0.6,and 0.9 wt.%)high entropy alloys(HEAs)were prepared via the powder metallurgy technique.A homogenous distribution of the elements in all alloys due to the formation of a solid solution phase is observed.The density and hardness of the prepared HEAs are improved by Si and Ti additions,compared to FeNiCrCo HEA.The wear rate of the prepared alloys was studied at different loads and the results indicate that the alloys that contain 0.3 wt.%Si and 0.9 wt.%Ti have the lowest wear rates.X-ray diffraction,SEM,and EDX were used to understand the phases,grain sizes,and microstructures in different investigated HEAs.The effects of Si and Ti content on the corrosion behavior and surface morphologies of sintered FeNiCrCoSi_(x) and FeNiCrCoTi_(x) HEAs were studied by immersion in H_(2)SO_(4),HNO_(3),and HCl solutions.Uniform corrosion and localized pitting are observed in different sizes in the corrosive media used.Because of the smaller pit size and the reduced pit density,the FeNiCrCoSi_(0.3) HEA has an excellent microstructure.
文摘Due to high competition of the agriculture machines sector, the auto parts suppliers are investing in research to promote the development and reduce the costs of the products, passing these results to their clients who are the automakers. It was identified the need to redesign the regulation sieve system harvester, which is a compound assembly in the harvester＇s grain cleaning system, with the objective to reduce the costs and improve the ergonomic aspect, keeping the same efficiency from the original project. The improvement was developed by studying the original design and identifying possible project fails, such as components and manufacturing process which could be eliminated. For this, it was needed to do a research about rules and project considerations that must be applied in the products development and ergonomic too, specifically about geometric forms and anthropometric measures. From the redesign of this system, it is verified that it is possible by a study to identify possible improvements, and to develop a new system by a simple project, improving the ergonomic, reducing the cost and keeping the same efficacy from the original project.
文摘In this research study,Bambusa ssp,the utilized species of bamboo,was rendered into a more versatile construction material in the form of laminates.The laminated specimens were manufactured using simplified processing methods according to the ASTM D3039 and ASTM D143 standards.Polyvinyl acetate was the adhesive used between the 2-ply laminate.The mechanical properties of the specimens were evaluated through tensile,compressive and bending strength tests according to set standards on the Testometric M500-50AT Universal Testing Machine.The tensile strength of laminated bamboo was comparable to that of redwood,spruce,cedar and pine.The ratio of compressive strength of parallel to perpendicularfibers in compressive tests was in a close range to that of poplar,fir and pine.The correlation in compressive strength values between bamboo and wood confirmed the inherent anisotropic nature of both plant materials.
文摘Bamboo in its raw state is difficult to incorporate in complex structures due to its tubular shape. In this research article, a novel approach to connect bamboo was designed and evaluated in order to integrate sustainable material into modern structures. Several bamboo joints for culm connection were designed based on strength and durability under various loading capacity. The conceptual joints were manufactured and subjected to destructive testing on the Universal Testing Machine, Testometric M500-50AT. From the mechanical properties generated, final modifications and refinements were incorporated into the joint design. Self-drilling metal screw joints were found to be the strongest with a maximum resisting force of around 11 kN in compression and 10 kN in tension. Riveted joints were the second strongest joint, while tightening ring joints, the weakest among the three, could only resist a peak load of 747 N in tension. The joints, designed with metal fittings, proved to be more practical for utilization in assembly design.
文摘Form error measurement is a critical exercise in providing measures for the quality control in the precision manufacturing industry.Coordinate measuring machine （CMM） is one of the automated systems used in the accurate and precise dimensional measurements and geometrical form.This paper aims to study the effect of dynamic original unforeseeable errors at different undulations per revolution （UPR） of standard artifact measurement using selected two types of CMM touchtriggering stylus.Stylus-type and stylus-speed parameters were adopted and utilized throughout the course of experiment.The results are analyzed using fast Fourier transformation to obtain foreseeable geometrical errors due to CMM machine structure and stylus scanning speeds.The results of experiment successfully indicate that the number of UPR plays an important role in determining the CMM accuracy level of the roundness measurement result.Some specific error equations for stylus system and machine structure responses have been postulated and analysed to empirically predict the accuracy of PRISMOBridge-CMM-type at National Institute for Standards （NIS） in egypt.
文摘Power ultrasound is finding widespread applications in assisting conventional processes yielding products of better quality at lower processing power and temperature. Transmission of ultrasound is known to be affected by the boundaries between layers of different materials or same material but in different states （solid or liquid or gas）. This paper investigates the effects of ultrasound （US） on the surface of the solidified weld which has been subjected to ultrasonic vibrations of 20 kHz frequency during laser welding. Vibrations due to ultrasound normally exert a very high force which is usually hundred or thousand times the gravity. The transverse waves will also cause movement of molten material in the weld. As the surface of the weld beads were of interest and not the mechanical properties and the microstructure, investigation of bead on plate welds were found to be sufficient. High carbon steel plate was held at one end by the ultrasonic horn through which ultrasound was injected. A bead on plate weld using a CO2 laser （1 kW） was then performed along the center of the plate using three different welding speeds namely, 400, 1200 and 2000 mm per minute. The ultrasonic powers selected were 3 W and 6 W respectively for each welding speed as higher acoustical power was causing ejection of molten metal from the pool during welding. 3D surface measurements and analysis were then made on a section of length 20 mm using a Talysurf machine. The results show that the surface of the weld was affected to different extent depending on the positions being considered in the weld. Some regions were similar to the reference weld whereas some specific regions were heavily disrupted with deep valleys followed by high peak/s. This shows that US vibration of weld pools, even at very small acoustical power, is a more complex problem than other similar processes such as casting because of the very small volume of molten metal involved.
文摘Hydroxyapatite （HA） nano-powder was synthesized via wet chemical technique in a used precipitation reaction, in which Ca（OH）2 and H3PO4 were used as precursors. Deionised water was used as a diluting media for the reaction and ammonia was used to adjust the pH. The synthetic HA nano-powder has some medical applications such as a coating material in orthopaedic implants and in dental. HA powder has been studied at different temperatures from 100 to 800 ℃ to achieve the stoichiometric Ca/P ratio 1.667. The optimum temperature was found to be 600 ℃. Above this temperature, the HA powder decomposed to CaO. The crystallite size of HA powder was found to be in the range of 8.47-24.47 nm. The crystallographic properties were evaluated by X-ray diffraction, Fourier transform infrared spectroscopy, energy dispersive X- ray spectroscopy and scanning electron microscopy. The results show that, high purity of nano-hydroxyapatite powders could be obtained at low temperatures, and the crystallinity, crystallite size and Ca/P ratio of the resulting nanoparticles were found to be dependent on the calcination temperature. When Ca/P ratio exceeded 1.75, formation of CaO phase was observed.
