A qualitative and quantitative workplace assessment was carried out to determine naphtha exposure in a tyre manufacturing industry. A qualitative chemical health risk assessment was conducted to identify naphtha hazar...A qualitative and quantitative workplace assessment was carried out to determine naphtha exposure in a tyre manufacturing industry. A qualitative chemical health risk assessment was conducted to identify naphtha hazard at the workplace. Quantitative assessment using Portable VOC Monitor, Automatic Sampling Pump and personal air sampling pump was used to determine VOC concentrations, organic solvents, and individual air naphtha respectively. The risk rating of naphtha was estimated to be 5. The mean VOC concentration was in the range of 2.43 to 92.93 ppm. Repair area had the highest VOC concentration while the lowest was in the moulding area. Each work station had significant differences for VOC concentrations （p 〈 0.001）. Laboratory analysis found various solvents including 2-methyl pentane, hexane, methyl cyclopentane, heptane, cyclohexane and toluene which were present in the liquid naphtha. Only xylene has been detected in the making and moulding areas with a range of 2 to 5 ppm. Meanwhile, the air naphtha concentrations of the exposed workers were significantly higher than those unexposed. The risk of naphtha exposure was qualitatively significant and not adequately controlled. Naphtha was detected in all work stations since it is the main solvent used. The ＂Repair Area＂ was significantly more contaminated than the other area.展开更多
The effects of Cu content on the microstructure and mechanical properties of thixoformed Al-6Si-xCu-0.3Mg(x= 3,4,5and 6,mass fraction,%) alloys were studied.The samples were thixoformed at 50%liquid content and severa...The effects of Cu content on the microstructure and mechanical properties of thixoformed Al-6Si-xCu-0.3Mg(x= 3,4,5and 6,mass fraction,%) alloys were studied.The samples were thixoformed at 50%liquid content and several of the samples were treated with the T6 heat treatment.The samples were then examined by optical microscopy(OM),scanning electron microscopy(SEM),energy dispersive X-ray(EDX) spectroscopy and X-ray diffraction(XRD) analysis,as well as hardness and tensile tests.The results show that the cooling slope casting and thixoforming process promote the formation of very fine and well distributed intermetallic compounds in the aluminium matrix and the mechanical properties of the alloys increase considerably compared with the permanent mould casting.The results also reveal that as the Cu content in the alloy increases,the hardness and tensile strength of the thixoformed alloys also increase.The ultimate tensile strength,yield strength and elongation to fracture of the thixoformed heat-treated Al-6Si-3Cu-0.3Mg alloy are 298 MPa,201 MPa and 4.5%,respectively,whereas the values of the thixoformed heat-treated alloy with high Cu content(6%) are 361 MPa,274 MPa and 1.1%,respectively.The fracture of the thixoformed Al-6Si-3Cu-0.3Mg alloy shows a dimple rupture,whereas in the alloy that contains the highest Cu content(6%),a cleavage fracture is observed.展开更多
A series of Al-6Si-3Cu-(0.3-2)Mg alloys were produced by a conventional casting process.Cooling slope technique wasemployed to produce feedstocks before they were thixoformed at50%liquid fraction.The effect of Mg on t...A series of Al-6Si-3Cu-(0.3-2)Mg alloys were produced by a conventional casting process.Cooling slope technique wasemployed to produce feedstocks before they were thixoformed at50%liquid fraction.The effect of Mg on the microstructure ofAl-Si-Cu aluminium alloys under as-cast and semisolid conditions was investigated.It was found that by adding Mg to Al-Si-Cualloy,some of the Al2Cu phase and silicon were consumed to form Al5Cu2Mg3Si5and Mg2Si phases.The needle-likeβ-Al5FeSi phasetransformed to Chinese-script-likeπ-Al8Mg3FeSi6with the addition of Mg.In the as-cast alloys,the primaryα(Al)was dendritic,butas the Mg content increased,the phase became less dendritic.Moreover,the Mg addition considerably modified the size of theα(Al)phase,but it had no significant effect on the silicon morphology.In the thixoformed alloys,the microstructure showed a fine globularprimary phase surrounded by uniformly distributed silicon and fragmented intermetallic phases.The eutectic silicon was modifiedfrom a flaky and acicular shape to fine fibrous particles.The effect of Mg on eutectic silicon during semisolid processing wasevident.The primary Mg2Si particles were modified from big polygonal particles to become smaller and more globular,whereas themorphology of the Chinese-script-likeπ-Al8Mg3FeSi6changed to a compact shape.The results also exhibit that as the Mg content inthe A319alloy increased,the hardness,yield strength and ultimate tensile strength of the thixoformed alloys significantly improved,but the elongation to fracture dropped.展开更多
Thixoforming is a processing method that deforms metal in a semisolid state.The advantages of this process include the production of parts with good surface finish,fine microstructures and superior mechanical properti...Thixoforming is a processing method that deforms metal in a semisolid state.The advantages of this process include the production of parts with good surface finish,fine microstructures and superior mechanical properties.However,the process mostly produces parts from aluminium cast grades,thereby not fully utilising the true potential of this method.Hence,thermodynamic modelling can be used to formulate alloy compositions that favour this processing method.Here,the effects of reducing copper content and increasing silicon and magnesium contents on the thixoformability of aluminium alloy 2014 were presented.The work consists of both the modelling and experimental validation.Results showed that by increasing Si and decreasing Cu content in the alloy,the solidification interval temperature was decreased and the temperature working window between the stipulated liquid fractions was widened,two of the characteristics favouring the process.A high solid-solution temperature employed resulted in the dissolution of unfavourable Mg2Si compound.An increase in Mg content used also resulted in the formation of the compactπ-Al8FeMg3Si6 phase and the decrease in the amount of the sharp and plate-like structure of theβ-Al5FeSi phase,improving the strength of the modified alloy.Subsequent T6 heat treatment successfully further increased the strength of the modified alloy.展开更多
This paper has been done on study kinematic problem of Persian joint in a general way. In this study, instead of using simulation analysis method as in the previous researches, the 3D rotation matrix method is applied...This paper has been done on study kinematic problem of Persian joint in a general way. In this study, instead of using simulation analysis method as in the previous researches, the 3D rotation matrix method is applied to present the relationship of angular velocities of input shaft and output shaft. The result shows that when the angle between intersecting shafts changes from 0 to 135°, the angular velocity is maintained constant. This new result completely matches with analysis from kinematic simulation of this mechanism. The obtained result is an important base to solve dynamic problem in order to develop the applicability of this joint in reality.展开更多
Designing reliable flight control for an autonomous helicopter requires a high performance dynamics model.In this paper,a nonlinear autoregressive with exogenous inputs (NLARX) model is selected as the mathematical st...Designing reliable flight control for an autonomous helicopter requires a high performance dynamics model.In this paper,a nonlinear autoregressive with exogenous inputs (NLARX) model is selected as the mathematical structure for identifying and controlling the flight of a small-scale helicopter.A neural network learning algorithm is combined with the NLARX model to identify the dynamic component of the rotorcraft unmanned aerial vehicle (RUAV).This identification process is based on the well-known gradient descent learning algorithm.As a case study,the multiple-input multiple-output (MIMO) model predictive control (MPC) is applied to control the pitch motion of the helicopter.Results of the neural network output model are closely match with the real flight data.The MPC also shows good performance under various conditions.展开更多
The effects of Mg content on the microstructure and tensile properties of thixoformed A319 alloys were studied. The samples were thixoformed at 50% liquid content and some of the thixoformed samples were subjected to ...The effects of Mg content on the microstructure and tensile properties of thixoformed A319 alloys were studied. The samples were thixoformed at 50% liquid content and some of the thixoformed samples were subjected to the T6 heat treatment. The samples were then examined by optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive X-ray (EDX) spectroscopy and X-ray diffraction (XRD) analysis as well as tensile tests. The results showed that magnesium was able to refine the eutectic silicon in the samples. It was also observed that a compact Al9FeMg3Si5 phase was formed when the magnesium content was 1.0% and 1.5%. The results also revealed that as the magnesium content in the alloy increases, the tensile strengths of the thixoformed alloys also increase. The ultimate tensile strength, yield strength and elongation to fracture of the thixoformed A319 heat treated alloy were 298 MPa, 201 MPa and 4.5%, respectively, whereas the values of the thixoformed heat treated alloy with 1.5% Mg content were 325 MPa, 251 MPa and 1.4%, respectively. Thixoformed A319 alloy showed a dimple fracture behaviour, while thixoformed A319 alloys with 1.5% Mg showed a mixed mode fracture behaviour, where dimple and cleavage ruptures were seen on the fracture surface of the samples.展开更多
Various 3D modeling software has been developed for design and manufacturing. Most of the commercially available software uses native file formats, which may not be able to be read or understood by other software. Thi...Various 3D modeling software has been developed for design and manufacturing. Most of the commercially available software uses native file formats, which may not be able to be read or understood by other software. This paper deals with the development of a generic approach of a 3D model conversion program for virtual manufacturing （VM）, using a lexical analyzer generator Lex and the Open Graphic Library （OpenGL）. The program is able to convert 3D mesh data between four universal file formats, i.e., Stereolithography （STL）, Virtual Reality Modeling Language （VRML）, eXtensible Markup Language （XML）, and Object （OBJ）. Simple assembly functions can be applied to the imported models. The quaternion angle is used for object rotation to overcome the problem of gimbal lock or a loss of one degree of rotational freedom. The program has been validated by importing the neutral format models into the program, applying the transformation, saving the new models with a new coordinate system, and lastly exporting into other commercial software. The results showed that the program is able to render and re-arrange accurately the geometry data from the different universal file formats and that it can be used in VM. Therefore, the output models from a VM system can be transferred or imported to another VM system in a universal file format.展开更多
This paper presents a development of a novel path planning algorithm, called Generalized Laser simulator (GLS), for solving the mobilerobot path planning problem in a two-dimensional map with the presence ofconstraint...This paper presents a development of a novel path planning algorithm, called Generalized Laser simulator (GLS), for solving the mobilerobot path planning problem in a two-dimensional map with the presence ofconstraints. This approach gives the possibility to find the path for a wheelmobile robot considering some constraints during the robot movement inboth known and unknown environments. The feasible path is determinedbetween the start and goal positions by generating wave of points in alldirection towards the goal point with adhering to constraints. In simulation,the proposed method has been tested in several working environments withdifferent degrees of complexity. The results demonstrated that the proposedmethod is able to generate efficiently an optimal collision-free path. Moreover,the performance of the proposed method was compared with the A-star andlaser simulator (LS) algorithms in terms of path length, computational timeand path smoothness. The results revealed that the proposed method hasshortest path length, less computational time and the best smooth path. Asan average, GLS is faster than A∗ and LS by 7.8 and 5.5 times, respectivelyand presents a path shorter than A∗ and LS by 1.2 and 1.5 times. In orderto verify the performance of the developed method in dealing with constraints, an experimental study was carried out using a Wheeled Mobile Robot(WMR) platform in labs and roads. The experimental work investigates acomplete autonomous WMR path planning in the lab and road environmentsusing a live video streaming. Local maps were built using data from a live video streaming with real-time image processing to detect segments of theanalogous-road in lab or real-road environments. The study shows that theproposed method is able to generate shortest path and best smooth trajectoryfrom start to goal points in comparison with laser simulator.展开更多
The thermal shock and fatigue behavior of pressureless sintered Al_(2)O_(3)-SiO_(2)-ZrO_(2)(ASZ)composites was studied.The influence of the thermal shock and fatigue on the strengthening response of ASZ has been inves...The thermal shock and fatigue behavior of pressureless sintered Al_(2)O_(3)-SiO_(2)-ZrO_(2)(ASZ)composites was studied.The influence of the thermal shock and fatigue on the strengthening response of ASZ has been investigated by measuring the strength retention and microstructural changes.The magnitude of the flexural strength and fracture of the ASZ has been compared with that of the monolithic Al_(2)O_(3)(A)and Al_(2)O_(3)-SiO_(2)-ZrO_(2)(AZ)composites under the same experimental conditions.Results indicated that the ASZ composites possess the highest resistance against thermal shock and fatigue,in comparison with A and AZ.The improvements were attributed to the enhancement in the fracture toughness of ASZ and the presence of multi-phase reinforcement.展开更多
文摘A qualitative and quantitative workplace assessment was carried out to determine naphtha exposure in a tyre manufacturing industry. A qualitative chemical health risk assessment was conducted to identify naphtha hazard at the workplace. Quantitative assessment using Portable VOC Monitor, Automatic Sampling Pump and personal air sampling pump was used to determine VOC concentrations, organic solvents, and individual air naphtha respectively. The risk rating of naphtha was estimated to be 5. The mean VOC concentration was in the range of 2.43 to 92.93 ppm. Repair area had the highest VOC concentration while the lowest was in the moulding area. Each work station had significant differences for VOC concentrations （p 〈 0.001）. Laboratory analysis found various solvents including 2-methyl pentane, hexane, methyl cyclopentane, heptane, cyclohexane and toluene which were present in the liquid naphtha. Only xylene has been detected in the making and moulding areas with a range of 2 to 5 ppm. Meanwhile, the air naphtha concentrations of the exposed workers were significantly higher than those unexposed. The risk of naphtha exposure was qualitatively significant and not adequately controlled. Naphtha was detected in all work stations since it is the main solvent used. The ＂Repair Area＂ was significantly more contaminated than the other area.
基金Universiti Teknikal Malaysia Melaka (UTeM) and the Ministry of Education Malaysia for financial support of this studyUniversiti Kebangsaan Malaysia (UKM) for the financial support under research grants GUP-2012-040 and AP-2012-014
文摘The effects of Cu content on the microstructure and mechanical properties of thixoformed Al-6Si-xCu-0.3Mg(x= 3,4,5and 6,mass fraction,%) alloys were studied.The samples were thixoformed at 50%liquid content and several of the samples were treated with the T6 heat treatment.The samples were then examined by optical microscopy(OM),scanning electron microscopy(SEM),energy dispersive X-ray(EDX) spectroscopy and X-ray diffraction(XRD) analysis,as well as hardness and tensile tests.The results show that the cooling slope casting and thixoforming process promote the formation of very fine and well distributed intermetallic compounds in the aluminium matrix and the mechanical properties of the alloys increase considerably compared with the permanent mould casting.The results also reveal that as the Cu content in the alloy increases,the hardness and tensile strength of the thixoformed alloys also increase.The ultimate tensile strength,yield strength and elongation to fracture of the thixoformed heat-treated Al-6Si-3Cu-0.3Mg alloy are 298 MPa,201 MPa and 4.5%,respectively,whereas the values of the thixoformed heat-treated alloy with high Cu content(6%) are 361 MPa,274 MPa and 1.1%,respectively.The fracture of the thixoformed Al-6Si-3Cu-0.3Mg alloy shows a dimple rupture,whereas in the alloy that contains the highest Cu content(6%),a cleavage fracture is observed.
基金Universiti Kebangsaan Malaysia(UKM)and the Ministry of Higher Education(MOHE),Malaysia,for financial support under research grants AP-2012-014 and FRGS/1/2014/TK01/UKM/01/2
文摘A series of Al-6Si-3Cu-(0.3-2)Mg alloys were produced by a conventional casting process.Cooling slope technique wasemployed to produce feedstocks before they were thixoformed at50%liquid fraction.The effect of Mg on the microstructure ofAl-Si-Cu aluminium alloys under as-cast and semisolid conditions was investigated.It was found that by adding Mg to Al-Si-Cualloy,some of the Al2Cu phase and silicon were consumed to form Al5Cu2Mg3Si5and Mg2Si phases.The needle-likeβ-Al5FeSi phasetransformed to Chinese-script-likeπ-Al8Mg3FeSi6with the addition of Mg.In the as-cast alloys,the primaryα(Al)was dendritic,butas the Mg content increased,the phase became less dendritic.Moreover,the Mg addition considerably modified the size of theα(Al)phase,but it had no significant effect on the silicon morphology.In the thixoformed alloys,the microstructure showed a fine globularprimary phase surrounded by uniformly distributed silicon and fragmented intermetallic phases.The eutectic silicon was modifiedfrom a flaky and acicular shape to fine fibrous particles.The effect of Mg on eutectic silicon during semisolid processing wasevident.The primary Mg2Si particles were modified from big polygonal particles to become smaller and more globular,whereas themorphology of the Chinese-script-likeπ-Al8Mg3FeSi6changed to a compact shape.The results also exhibit that as the Mg content inthe A319alloy increased,the hardness,yield strength and ultimate tensile strength of the thixoformed alloys significantly improved,but the elongation to fracture dropped.
基金the National University of Malaysia (Universiti Kebangsaan Malaysia, UKM)the Ministry of Education (MOE) of Malaysia for the financial support received under research grant DIP-2016-007
文摘Thixoforming is a processing method that deforms metal in a semisolid state.The advantages of this process include the production of parts with good surface finish,fine microstructures and superior mechanical properties.However,the process mostly produces parts from aluminium cast grades,thereby not fully utilising the true potential of this method.Hence,thermodynamic modelling can be used to formulate alloy compositions that favour this processing method.Here,the effects of reducing copper content and increasing silicon and magnesium contents on the thixoformability of aluminium alloy 2014 were presented.The work consists of both the modelling and experimental validation.Results showed that by increasing Si and decreasing Cu content in the alloy,the solidification interval temperature was decreased and the temperature working window between the stipulated liquid fractions was widened,two of the characteristics favouring the process.A high solid-solution temperature employed resulted in the dissolution of unfavourable Mg2Si compound.An increase in Mg content used also resulted in the formation of the compactπ-Al8FeMg3Si6 phase and the decrease in the amount of the sharp and plate-like structure of theβ-Al5FeSi phase,improving the strength of the modified alloy.Subsequent T6 heat treatment successfully further increased the strength of the modified alloy.
文摘This paper has been done on study kinematic problem of Persian joint in a general way. In this study, instead of using simulation analysis method as in the previous researches, the 3D rotation matrix method is applied to present the relationship of angular velocities of input shaft and output shaft. The result shows that when the angle between intersecting shafts changes from 0 to 135°, the angular velocity is maintained constant. This new result completely matches with analysis from kinematic simulation of this mechanism. The obtained result is an important base to solve dynamic problem in order to develop the applicability of this joint in reality.
基金Project (No.13-01-03-SF0024) supported by the MOSTI (Malaysia) Sciencefund: Hardware-in-the-Loop Simulation for Control System of Mini Scale Rotorcraft
文摘Designing reliable flight control for an autonomous helicopter requires a high performance dynamics model.In this paper,a nonlinear autoregressive with exogenous inputs (NLARX) model is selected as the mathematical structure for identifying and controlling the flight of a small-scale helicopter.A neural network learning algorithm is combined with the NLARX model to identify the dynamic component of the rotorcraft unmanned aerial vehicle (RUAV).This identification process is based on the well-known gradient descent learning algorithm.As a case study,the multiple-input multiple-output (MIMO) model predictive control (MPC) is applied to control the pitch motion of the helicopter.Results of the neural network output model are closely match with the real flight data.The MPC also shows good performance under various conditions.
基金the Universiti Teknikal Malaysia Melaka (UTeM)the Ministry of Education, Malaysia for being financial sponsorsUniversiti Kebangsaan Malaysia (UKM) for the financial support under research grants GUP-2012-040 and AP-2012-014
文摘The effects of Mg content on the microstructure and tensile properties of thixoformed A319 alloys were studied. The samples were thixoformed at 50% liquid content and some of the thixoformed samples were subjected to the T6 heat treatment. The samples were then examined by optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive X-ray (EDX) spectroscopy and X-ray diffraction (XRD) analysis as well as tensile tests. The results showed that magnesium was able to refine the eutectic silicon in the samples. It was also observed that a compact Al9FeMg3Si5 phase was formed when the magnesium content was 1.0% and 1.5%. The results also revealed that as the magnesium content in the alloy increases, the tensile strengths of the thixoformed alloys also increase. The ultimate tensile strength, yield strength and elongation to fracture of the thixoformed A319 heat treated alloy were 298 MPa, 201 MPa and 4.5%, respectively, whereas the values of the thixoformed heat treated alloy with 1.5% Mg content were 325 MPa, 251 MPa and 1.4%, respectively. Thixoformed A319 alloy showed a dimple fracture behaviour, while thixoformed A319 alloys with 1.5% Mg showed a mixed mode fracture behaviour, where dimple and cleavage ruptures were seen on the fracture surface of the samples.
基金Project （No. RG060/09AET） supported by the University of Malaya Research Grant （UMRG）
文摘Various 3D modeling software has been developed for design and manufacturing. Most of the commercially available software uses native file formats, which may not be able to be read or understood by other software. This paper deals with the development of a generic approach of a 3D model conversion program for virtual manufacturing （VM）, using a lexical analyzer generator Lex and the Open Graphic Library （OpenGL）. The program is able to convert 3D mesh data between four universal file formats, i.e., Stereolithography （STL）, Virtual Reality Modeling Language （VRML）, eXtensible Markup Language （XML）, and Object （OBJ）. Simple assembly functions can be applied to the imported models. The quaternion angle is used for object rotation to overcome the problem of gimbal lock or a loss of one degree of rotational freedom. The program has been validated by importing the neutral format models into the program, applying the transformation, saving the new models with a new coordinate system, and lastly exporting into other commercial software. The results showed that the program is able to render and re-arrange accurately the geometry data from the different universal file formats and that it can be used in VM. Therefore, the output models from a VM system can be transferred or imported to another VM system in a universal file format.
基金The authors would like to thank the United Arab Emirates University for funding this work under Start-Up grant[G00003321].
文摘This paper presents a development of a novel path planning algorithm, called Generalized Laser simulator (GLS), for solving the mobilerobot path planning problem in a two-dimensional map with the presence ofconstraints. This approach gives the possibility to find the path for a wheelmobile robot considering some constraints during the robot movement inboth known and unknown environments. The feasible path is determinedbetween the start and goal positions by generating wave of points in alldirection towards the goal point with adhering to constraints. In simulation,the proposed method has been tested in several working environments withdifferent degrees of complexity. The results demonstrated that the proposedmethod is able to generate efficiently an optimal collision-free path. Moreover,the performance of the proposed method was compared with the A-star andlaser simulator (LS) algorithms in terms of path length, computational timeand path smoothness. The results revealed that the proposed method hasshortest path length, less computational time and the best smooth path. Asan average, GLS is faster than A∗ and LS by 7.8 and 5.5 times, respectivelyand presents a path shorter than A∗ and LS by 1.2 and 1.5 times. In orderto verify the performance of the developed method in dealing with constraints, an experimental study was carried out using a Wheeled Mobile Robot(WMR) platform in labs and roads. The experimental work investigates acomplete autonomous WMR path planning in the lab and road environmentsusing a live video streaming. Local maps were built using data from a live video streaming with real-time image processing to detect segments of theanalogous-road in lab or real-road environments. The study shows that theproposed method is able to generate shortest path and best smooth trajectoryfrom start to goal points in comparison with laser simulator.
文摘The thermal shock and fatigue behavior of pressureless sintered Al_(2)O_(3)-SiO_(2)-ZrO_(2)(ASZ)composites was studied.The influence of the thermal shock and fatigue on the strengthening response of ASZ has been investigated by measuring the strength retention and microstructural changes.The magnitude of the flexural strength and fracture of the ASZ has been compared with that of the monolithic Al_(2)O_(3)(A)and Al_(2)O_(3)-SiO_(2)-ZrO_(2)(AZ)composites under the same experimental conditions.Results indicated that the ASZ composites possess the highest resistance against thermal shock and fatigue,in comparison with A and AZ.The improvements were attributed to the enhancement in the fracture toughness of ASZ and the presence of multi-phase reinforcement.
