Porosity is reported to be a major issue when welding cast magnesium. Therefore, it is important to understand the pore formation mechanisms and find procedures that could be used to reduce porosity. This study invest...Porosity is reported to be a major issue when welding cast magnesium. Therefore, it is important to understand the pore formation mechanisms and find procedures that could be used to reduce porosity. This study investigated the possibility of using twin-spot optics for reducing the porosity in laser welded cast magnesium. Two twin-spot welding setups were compared using either a beam splitter or twin-spot welding with primary and secondary (placed in front of the primary optic) optics. The results showed that welding with a dual optic setup with a defocused secondary beam reduced the volumetric porosity in the weld to 5%. The highest levels of volumetric porosity were 30%, and were a result of using the dual optic setup, but with a defocused primary beam. No clear relation between the level of porosity and power or welding speed was found. It was found that the amount of porosity depended on the balance of the energy input (controlled by defocusing) between the two beams. Porosity formation can be reduced if the energy from the first beam results in the nucleation and initial growth of pores. Reheating by the second beam then allows the pores to grow and escape from the molten material without melting additional base material. Furthermore, twin-spot welding is shown to be a promising combination of a production friendly solution and high quality welding.展开更多
We sincerely thank the authors of the commentary1 for their thoughtful analysis and constructive critique of our systematic review on ischemic preconditioning(IPC)and placebo effects in exercise capacity and athletic ...We sincerely thank the authors of the commentary1 for their thoughtful analysis and constructive critique of our systematic review on ischemic preconditioning(IPC)and placebo effects in exercise capacity and athletic performance.2Their attention to methodological details,particularly concerning the inclusion and timing of warm-up protocols across studies,is commendable and contributes meaningfully to the ongoing refinement of IPC research in sports science.展开更多
Recent efforts and advances in additive manufacturing(AM) on different types of new materials are presented and reviewed. Special attention is paid to the material design of cladding layers, the choice of feedstock ma...Recent efforts and advances in additive manufacturing(AM) on different types of new materials are presented and reviewed. Special attention is paid to the material design of cladding layers, the choice of feedstock materials, the metallurgical behavior and synthesis principle during the AM process, and the resulted microstructures and properties, as well as the relationship between these factors. Thereafter,the trend of development in the future is forecasted, including: Effects of the particles size and size distribution of powders; Approaches for producing fine microstructures; Opportunities for creating new materials by AM; Wide applications in reconditioning of damaged components; Challenges for deep understanding and applications of the AMed new materials. The idea of "Develop Materials" or "Create Materials" by AM is highlighted, but a series of scientific, technological and engineering problems remain to be solved in future.展开更多
The ability to control the structure of a surface offers benefits in a wide range of aerospace applications.A novel EB (Electron Beam) materials processing technology developed at TWI,Surfi-Sculpt,addresses this nee...The ability to control the structure of a surface offers benefits in a wide range of aerospace applications.A novel EB (Electron Beam) materials processing technology developed at TWI,Surfi-Sculpt,addresses this need by using an electron beam to generate precisely defined textured surfaces.Surfi-Sculpt offers improved mechanical keying with adjoining parts and consequently has generated interest as a preparation technique for surface coatings and for the joining of composite to metal.It has the potential to create customised aerodynamically and hydrodynamically enhanced surfaces and appears suitable for the manufacture of novel bearing and seal surfaces.The Surfi-Sculpt process has also showed promise in increasing the efficiency of heat exchange surfaces.This paper describes the background of the Surfi-Sculpt process and showcases a range of surfaces that have been produced with the technique.The results of a range of feasibility studies are presented to demonstrate the potential of the technology within the aerospace展开更多
Electron beam surfi-sculpt is a new metal surface processing technology,which is widely used in the areas of materials surface treatment,composite materials manufacturing,and so on.In this paper,comeld technology,whic...Electron beam surfi-sculpt is a new metal surface processing technology,which is widely used in the areas of materials surface treatment,composite materials manufacturing,and so on.In this paper,comeld technology,which was an application technology of electron beam surfi-sculpt during composite materials area,was introduced.And tensile experiments results and failure forms of Ti6Al4V/Carbon fibre single step joints were compared with different joining methods,such as slick embedding,adhesive bonding,riveting and comeld.It was found that comeld joint had more advantage of tensile property than other joining methods.At the same time,tensile process of comeld joint was analyzed with numerical simulation,and key factors of protrusions influenced tensile property were obtained,which was of importance to structure design and joint property improvement.展开更多
The functional properties of materials can be enhanced using surface features,for instance;to improve the thermal properties of heat exchangers.The development of the laser Surfi-Sculpt process over the past decade ...The functional properties of materials can be enhanced using surface features,for instance;to improve the thermal properties of heat exchangers.The development of the laser Surfi-Sculpt process over the past decade has resulted in a technology capable of producing a wide variety of features in metallic substrates.Furthermore,the potential for producing similar features in polymeric and ceramic substrates also exists.Recently the potential for utilizing high power focused laser beams to produce surface features using this process has been demonstrated.This paper details the results of recent trials performed with a 200 Yb-fibre laser and a galvanometer driven beam scanner for producing surface features using the Surfi-Sculpt process.A compact,cheap,easily robotically automated,laser Surfi-Sculpt machine,being able to operate at atmospheric pressure may have potential in a range of industry sectors.展开更多
The continuous growth in the manufacture of aerospace components such as blisks has led to an increase in the application of different hybrid materials fabricating methods,and thus the requirements for joining and str...The continuous growth in the manufacture of aerospace components such as blisks has led to an increase in the application of different hybrid materials fabricating methods,and thus the requirements for joining and strengthening of dissimilar welds.According to this goal,selective laser melted(SLM)Inconel718 was joined with forged AD730^(TM)Nickel-based superalloy through linear friction welding(LFW)in this study.Microstructure variation,specifically with respect to secondary phases precipitation was investigated.The microhardness and strengthening mechanisms of the weldment were also studied.The precipitation(volume fraction and size of particles)at different regions of both sides of the weld line was characterized.Close to the weld line,the dissolution ofγ’/γ"and Laves phases and grain refinement occurred which reveals the effects of both compression strain and high temperature on recrystallization and high degree of elemental diffusion in the weld zone(WZ).It is shown that the size,volume fraction,and shape of secondary phases increased and changed(from spherical to long-striped for Laves particles)as we went from the WZ toward the base metal.However,the measured microhardness indicated that the strength of AD730^(TM)alloy depends significantly on the grain size,while strength in SLM Inconel 718 was dominated by shape(or size)and the presence of secondary phases(γ’/γ"and Laves).展开更多
Hybrid laser-MAG welding with real-time adaptive control has been demonstrated.Hybrid welding conditions have been developed to produce ISO 13919-1 class B (stringent) quality butt welds between 8mm thickness steel pl...Hybrid laser-MAG welding with real-time adaptive control has been demonstrated.Hybrid welding conditions have been developed to produce ISO 13919-1 class B (stringent) quality butt welds between 8mm thickness steel plates,using a 5kW 6mm.mrad Yb fibre laser combined with conventional arc welding equipment.A laser vision seam tracking system has enabled a 7-axis robot,manipulating the hybrid welding head,to track butt joints in real time during welding.The laser vision system has also provided information on the variations in joint fit-up,in particular the width of any gaps,or height of any mismatches present.This information has then been used to automatically adjust the robot position or speed,or arc welding parameters,depending on the fit-up detected.In this way,the tolerance of the hybrid process has been augmented,producing stringent quality welds over a wider range of joint fit-up cases than when using fixed conditions alone.展开更多
Electron beam welding is recognized as an attractive method for minimizing distortion during welding,and is used frequently to join parts which are already finally machined or close to finished size.In such cases,befo...Electron beam welding is recognized as an attractive method for minimizing distortion during welding,and is used frequently to join parts which are already finally machined or close to finished size.In such cases,before EB welding,it is of great value to be able to estimate the level of accuracy that will be achieved and the dimensional stability of the assembly throughout its service life.This presentation describes the development of a finite element (FE) modelling technique,validated by experiment,for predicting and understanding the development of residual stresses and distortion during EB welding,particularly in circular components.The use of this method for optimization of welding procedures and residual stress mitigation methods is described and illustrated through a number of practical examples.展开更多
Petrochemical storage tanks are generally inspected when the tank is offline mostly to assess the extent of underside corrosion on the tank floor. Emptying, cleaning and opening a tank for inspection take many months ...Petrochemical storage tanks are generally inspected when the tank is offline mostly to assess the extent of underside corrosion on the tank floor. Emptying, cleaning and opening a tank for inspection take many months and are very expensive. Inspection costs can be reduced significantly by inserting robots through manholes on the tank roof to pertbrm non-destructive testing （NDT）. The challenge is to develop robots that can operate safely in explosive and hazardous environments and measure the thickness of floor plates using ultrasound sensors. This paper reports on the development of a small and inexpensive prototype robot （NDTBOT） which is designed to be intrinsically safe for zone zero operation. The robot ＂hops＂ across the floor to make measurements, without any external moving parts. The paper describes the design, experimental testing of the NDTBOT and presents results of steel plate thickness measurements made under water.展开更多
Contaminated concrete and metal pipework presents a major nuclear decommissioning challenge in terms of the total volumes of material to be treated,the radiation levels present and the number of facilities affected.Un...Contaminated concrete and metal pipework presents a major nuclear decommissioning challenge in terms of the total volumes of material to be treated,the radiation levels present and the number of facilities affected.Until recently,industrial lasers have often been seen as too unreliable for use in nuclear decommissioning environments and hence their usage has been limited.The advent of solid state 'fibre' lasers has,however,provided a robust and reliable industrial tool,capable of performing not only concrete scabbling but other laser based decommissioning processes,such as cutting.Whilst concrete scabbling has been demonstrated in the laboratory,to date,no representative scale demonstration has been provided which would give industry confidence in the technique.This paper will describe the development of a laser scabbling process head,equipped with an integrated debris collection device and adaptive control system for automatic maintenance of the attitude and stand off distance of the head from the concrete surface.The results of using optical fibre delivered laser power to remove the surface of a range of representative and large scale concrete samples will be described.Using 5kW of laser power,removal rates up to 7000 cc of concrete per hour have been recorded at a removal depth of the order 10mm.The paper will also report on the results of using the same laser source,for single-sided cutting of various 304L stainless steel tubes,of diameter up to 170mm and wall thickness up to 11mm.The results show that with the right optical configuration,it is entirely possible to laser cut tubes from one side,at extremely long and safe standoff distances,if the main objective is simply to sever the tube.展开更多
It is crucial to maintain wind turbine blades regularly, due to the high stress leading to defects or damage. Conventional methods require shipping the blades to a workshop for off-site inspection, which is extremely ...It is crucial to maintain wind turbine blades regularly, due to the high stress leading to defects or damage. Conventional methods require shipping the blades to a workshop for off-site inspection, which is extremely time-consuming and very costly. This work investigates the use of pulse-echo ultrasound to detect internal damages in wind turbine blades without the necessity to ship the blades off-site. A prototype 2D ultrasonic NDT （non-destructive testing） system has been developed and optimised for in-situ wind turbine blade inspection. The system is designed to be light weight so it can be easily carried by an inspector onto the wind turbine blade for in-situ inspection. It can be operated in 1D A-scan, 2D C-scan or 3D volume scan. A software system has been developed to control the automated scanning and show the damage areas in a 2D/3D map with different colours so that the inspector can easily identify the defective areas. Experiments on GFRP （glass fibre reinforced plastics） and wind turbine blades （made of GFRP） samples showed that internal defects can be detected. The main advantages of this system are fully automated 2D spatial scanning and the ability to alert the user to the damage of the inspected sample. It is intended to be used for in-situ inspection to save maintenance time and hence considered to be economically beneficial for the wind energy industry.展开更多
Shearography is an optical technique in the field of nondestructive evaluation(NDE)of various materials.Its main advantages are that it is noncontact type and can cover a large area in a single inspection.As a result,...Shearography is an optical technique in the field of nondestructive evaluation(NDE)of various materials.Its main advantages are that it is noncontact type and can cover a large area in a single inspection.As a result,although it has been widely acknowledged as an effective technique particularly for NDE of composite materials to detect subsurface defects such as delamination,disbond,cracks,and impact damages,the use of shearography for on-site inspection of wind turbine blades(WTBs)has not been reported.This is due to wind causing structural vibration in the WTB.The solution in this paper is to make the shearography sit on the WTB during inspection when the WTB is parked,so that the relative motion between the shearography and the WTB is minimized within the tolerance of the shearography system.The ultimate goal of the solution is to enable a robot-assisted shearography system to inspect the WTB on-site.This paper presents the research work on a new shearography design for integration with a robotic climber for on-site WTB inspection.The approach is tested and evaluated in experimental settings,and a comparative assessment of the approach with other robotic NDE techniques is carried out.The results demonstrate the potential benefits and suitability of the approach for on-site robotic inspection of WTBs.展开更多
文摘Porosity is reported to be a major issue when welding cast magnesium. Therefore, it is important to understand the pore formation mechanisms and find procedures that could be used to reduce porosity. This study investigated the possibility of using twin-spot optics for reducing the porosity in laser welded cast magnesium. Two twin-spot welding setups were compared using either a beam splitter or twin-spot welding with primary and secondary (placed in front of the primary optic) optics. The results showed that welding with a dual optic setup with a defocused secondary beam reduced the volumetric porosity in the weld to 5%. The highest levels of volumetric porosity were 30%, and were a result of using the dual optic setup, but with a defocused primary beam. No clear relation between the level of porosity and power or welding speed was found. It was found that the amount of porosity depended on the balance of the energy input (controlled by defocusing) between the two beams. Porosity formation can be reduced if the energy from the first beam results in the nucleation and initial growth of pores. Reheating by the second beam then allows the pores to grow and escape from the molten material without melting additional base material. Furthermore, twin-spot welding is shown to be a promising combination of a production friendly solution and high quality welding.
文摘We sincerely thank the authors of the commentary1 for their thoughtful analysis and constructive critique of our systematic review on ischemic preconditioning(IPC)and placebo effects in exercise capacity and athletic performance.2Their attention to methodological details,particularly concerning the inclusion and timing of warm-up protocols across studies,is commendable and contributes meaningfully to the ongoing refinement of IPC research in sports science.
基金financially supported by the National Natural Science Foundation of China (Grant Nos. 51775525, 51605456 and 51701198)
文摘Recent efforts and advances in additive manufacturing(AM) on different types of new materials are presented and reviewed. Special attention is paid to the material design of cladding layers, the choice of feedstock materials, the metallurgical behavior and synthesis principle during the AM process, and the resulted microstructures and properties, as well as the relationship between these factors. Thereafter,the trend of development in the future is forecasted, including: Effects of the particles size and size distribution of powders; Approaches for producing fine microstructures; Opportunities for creating new materials by AM; Wide applications in reconditioning of damaged components; Challenges for deep understanding and applications of the AMed new materials. The idea of "Develop Materials" or "Create Materials" by AM is highlighted, but a series of scientific, technological and engineering problems remain to be solved in future.
文摘The ability to control the structure of a surface offers benefits in a wide range of aerospace applications.A novel EB (Electron Beam) materials processing technology developed at TWI,Surfi-Sculpt,addresses this need by using an electron beam to generate precisely defined textured surfaces.Surfi-Sculpt offers improved mechanical keying with adjoining parts and consequently has generated interest as a preparation technique for surface coatings and for the joining of composite to metal.It has the potential to create customised aerodynamically and hydrodynamically enhanced surfaces and appears suitable for the manufacture of novel bearing and seal surfaces.The Surfi-Sculpt process has also showed promise in increasing the efficiency of heat exchange surfaces.This paper describes the background of the Surfi-Sculpt process and showcases a range of surfaces that have been produced with the technique.The results of a range of feasibility studies are presented to demonstrate the potential of the technology within the aerospace
基金Project50975268,supported by the National Natural Science Foundation of ChinaProject2008ZE25010,supported byAeronautical Science Foundation of China
文摘Electron beam surfi-sculpt is a new metal surface processing technology,which is widely used in the areas of materials surface treatment,composite materials manufacturing,and so on.In this paper,comeld technology,which was an application technology of electron beam surfi-sculpt during composite materials area,was introduced.And tensile experiments results and failure forms of Ti6Al4V/Carbon fibre single step joints were compared with different joining methods,such as slick embedding,adhesive bonding,riveting and comeld.It was found that comeld joint had more advantage of tensile property than other joining methods.At the same time,tensile process of comeld joint was analyzed with numerical simulation,and key factors of protrusions influenced tensile property were obtained,which was of importance to structure design and joint property improvement.
基金supported by the Natural Science Foundation of Hunan Province,China(No.2021JJ30672)the Science and Technology Project of Education Department of Hunan Province,China(No.22A0100)+1 种基金the National Natural Science Foundation of China(No.51627802)Xiangtan University Scientific Research Start-up Fund。
文摘The functional properties of materials can be enhanced using surface features,for instance;to improve the thermal properties of heat exchangers.The development of the laser Surfi-Sculpt process over the past decade has resulted in a technology capable of producing a wide variety of features in metallic substrates.Furthermore,the potential for producing similar features in polymeric and ceramic substrates also exists.Recently the potential for utilizing high power focused laser beams to produce surface features using this process has been demonstrated.This paper details the results of recent trials performed with a 200 Yb-fibre laser and a galvanometer driven beam scanner for producing surface features using the Surfi-Sculpt process.A compact,cheap,easily robotically automated,laser Surfi-Sculpt machine,being able to operate at atmospheric pressure may have potential in a range of industry sectors.
基金The authors gratefully acknowledge the support from the Natural Sciences and Engineering Research Council of Canada(NSERC)2018–03889 through a Discovery Grant.Thanks to Mr.Adrien Lieurey(IMT-Mines Albi ICA-site Albi)for his involvement and fabrication of SLM parts.They would also like to express their gratitude to Aubert&Duval Co.,Dr.Alexandre Devaux,and Prof.Cormier for providing forged AD730™samples and discussions on the definition of the scope of the project.Special thanks to TWI Ltd.for carrying out the LFW of the samples.
文摘The continuous growth in the manufacture of aerospace components such as blisks has led to an increase in the application of different hybrid materials fabricating methods,and thus the requirements for joining and strengthening of dissimilar welds.According to this goal,selective laser melted(SLM)Inconel718 was joined with forged AD730^(TM)Nickel-based superalloy through linear friction welding(LFW)in this study.Microstructure variation,specifically with respect to secondary phases precipitation was investigated.The microhardness and strengthening mechanisms of the weldment were also studied.The precipitation(volume fraction and size of particles)at different regions of both sides of the weld line was characterized.Close to the weld line,the dissolution ofγ’/γ"and Laves phases and grain refinement occurred which reveals the effects of both compression strain and high temperature on recrystallization and high degree of elemental diffusion in the weld zone(WZ).It is shown that the size,volume fraction,and shape of secondary phases increased and changed(from spherical to long-striped for Laves particles)as we went from the WZ toward the base metal.However,the measured microhardness indicated that the strength of AD730^(TM)alloy depends significantly on the grain size,while strength in SLM Inconel 718 was dominated by shape(or size)and the presence of secondary phases(γ’/γ"and Laves).
基金funding from the European Community's Seventh Framework Programme(FP7/2007-2013)under grant agreement n°222289
文摘Hybrid laser-MAG welding with real-time adaptive control has been demonstrated.Hybrid welding conditions have been developed to produce ISO 13919-1 class B (stringent) quality butt welds between 8mm thickness steel plates,using a 5kW 6mm.mrad Yb fibre laser combined with conventional arc welding equipment.A laser vision seam tracking system has enabled a 7-axis robot,manipulating the hybrid welding head,to track butt joints in real time during welding.The laser vision system has also provided information on the variations in joint fit-up,in particular the width of any gaps,or height of any mismatches present.This information has then been used to automatically adjust the robot position or speed,or arc welding parameters,depending on the fit-up detected.In this way,the tolerance of the hybrid process has been augmented,producing stringent quality welds over a wider range of joint fit-up cases than when using fixed conditions alone.
文摘Electron beam welding is recognized as an attractive method for minimizing distortion during welding,and is used frequently to join parts which are already finally machined or close to finished size.In such cases,before EB welding,it is of great value to be able to estimate the level of accuracy that will be achieved and the dimensional stability of the assembly throughout its service life.This presentation describes the development of a finite element (FE) modelling technique,validated by experiment,for predicting and understanding the development of residual stresses and distortion during EB welding,particularly in circular components.The use of this method for optimization of welding procedures and residual stress mitigation methods is described and illustrated through a number of practical examples.
文摘Petrochemical storage tanks are generally inspected when the tank is offline mostly to assess the extent of underside corrosion on the tank floor. Emptying, cleaning and opening a tank for inspection take many months and are very expensive. Inspection costs can be reduced significantly by inserting robots through manholes on the tank roof to pertbrm non-destructive testing （NDT）. The challenge is to develop robots that can operate safely in explosive and hazardous environments and measure the thickness of floor plates using ultrasound sensors. This paper reports on the development of a small and inexpensive prototype robot （NDTBOT） which is designed to be intrinsically safe for zone zero operation. The robot ＂hops＂ across the floor to make measurements, without any external moving parts. The paper describes the design, experimental testing of the NDTBOT and presents results of steel plate thickness measurements made under water.
文摘Contaminated concrete and metal pipework presents a major nuclear decommissioning challenge in terms of the total volumes of material to be treated,the radiation levels present and the number of facilities affected.Until recently,industrial lasers have often been seen as too unreliable for use in nuclear decommissioning environments and hence their usage has been limited.The advent of solid state 'fibre' lasers has,however,provided a robust and reliable industrial tool,capable of performing not only concrete scabbling but other laser based decommissioning processes,such as cutting.Whilst concrete scabbling has been demonstrated in the laboratory,to date,no representative scale demonstration has been provided which would give industry confidence in the technique.This paper will describe the development of a laser scabbling process head,equipped with an integrated debris collection device and adaptive control system for automatic maintenance of the attitude and stand off distance of the head from the concrete surface.The results of using optical fibre delivered laser power to remove the surface of a range of representative and large scale concrete samples will be described.Using 5kW of laser power,removal rates up to 7000 cc of concrete per hour have been recorded at a removal depth of the order 10mm.The paper will also report on the results of using the same laser source,for single-sided cutting of various 304L stainless steel tubes,of diameter up to 170mm and wall thickness up to 11mm.The results show that with the right optical configuration,it is entirely possible to laser cut tubes from one side,at extremely long and safe standoff distances,if the main objective is simply to sever the tube.
文摘It is crucial to maintain wind turbine blades regularly, due to the high stress leading to defects or damage. Conventional methods require shipping the blades to a workshop for off-site inspection, which is extremely time-consuming and very costly. This work investigates the use of pulse-echo ultrasound to detect internal damages in wind turbine blades without the necessity to ship the blades off-site. A prototype 2D ultrasonic NDT （non-destructive testing） system has been developed and optimised for in-situ wind turbine blade inspection. The system is designed to be light weight so it can be easily carried by an inspector onto the wind turbine blade for in-situ inspection. It can be operated in 1D A-scan, 2D C-scan or 3D volume scan. A software system has been developed to control the automated scanning and show the damage areas in a 2D/3D map with different colours so that the inspector can easily identify the defective areas. Experiments on GFRP （glass fibre reinforced plastics） and wind turbine blades （made of GFRP） samples showed that internal defects can be detected. The main advantages of this system are fully automated 2D spatial scanning and the ability to alert the user to the damage of the inspected sample. It is intended to be used for in-situ inspection to save maintenance time and hence considered to be economically beneficial for the wind energy industry.
基金The work reported in this paper has been receiving funding from EU H2020 research and innovation programme under grant agreement No.780662.
文摘Shearography is an optical technique in the field of nondestructive evaluation(NDE)of various materials.Its main advantages are that it is noncontact type and can cover a large area in a single inspection.As a result,although it has been widely acknowledged as an effective technique particularly for NDE of composite materials to detect subsurface defects such as delamination,disbond,cracks,and impact damages,the use of shearography for on-site inspection of wind turbine blades(WTBs)has not been reported.This is due to wind causing structural vibration in the WTB.The solution in this paper is to make the shearography sit on the WTB during inspection when the WTB is parked,so that the relative motion between the shearography and the WTB is minimized within the tolerance of the shearography system.The ultimate goal of the solution is to enable a robot-assisted shearography system to inspect the WTB on-site.This paper presents the research work on a new shearography design for integration with a robotic climber for on-site WTB inspection.The approach is tested and evaluated in experimental settings,and a comparative assessment of the approach with other robotic NDE techniques is carried out.The results demonstrate the potential benefits and suitability of the approach for on-site robotic inspection of WTBs.
