The experimental investigations of the effect of contact time/temperature on initiating the cook-off using 7.62 mm calibre cartridge cases(CC) were conducted previously.These cartridges were hlled with commercial off-...The experimental investigations of the effect of contact time/temperature on initiating the cook-off using 7.62 mm calibre cartridge cases(CC) were conducted previously.These cartridges were hlled with commercial off-the-shelf(COTS) double based(DB) propellant(Bulls Eye)and were loaded in a hot chamber.The thermal explosion temperature is of great significance to both weapon designers and safety inspectors as it provides the operational limit and safe operating temperature.For CC under test,it was found that the cook-off temperatures of this propellant were encountered with the heat transfer profile of the simulated gun barrel between 151.4 ℃ and 153.4 ℃,with a reaction occurring in less than300 s after the round was chambered.Usefully,each experiment was found to be consistent and repeatable.展开更多
This paper gives a succinct review of dual-spinprojectile stability and some technologies relating to them.It describes how the traditional stability factors from linear projectile theory are modified to better descri...This paper gives a succinct review of dual-spinprojectile stability and some technologies relating to them.It describes how the traditional stability factors from linear projectile theory are modified to better describe a controlled dual-spin projectile.Finally,it reviews works which have investigated how different aspects of a controlled dual-spin design can affect flight stability,primarily airframe structure and canard properties.A conclusion is given,highlighting important guidelines from the enclosed discussions.展开更多
Occasionally, the Whipple shields are used for the protection of a space station and a satellite against the meteoroids and orbital debris. In the Whipple shields each layer of the shield depletes part of high speed p...Occasionally, the Whipple shields are used for the protection of a space station and a satellite against the meteoroids and orbital debris. In the Whipple shields each layer of the shield depletes part of high speed projectile en- ergy either by breaking the projectile or absorbing its energy. Similarly, this investigation uses the Whipple shields against the shaped charge to protect the light armour such as infantry fighting vehicles with a little modification in their design. The unsteady multiple interactions of shaped charge jet with the Whipple shield package against the steady homogeneous target is scrutinized to optimize the shield thickness. Sim- ulations indicate that the shield thickness of 0.75 mm offers an optimum configuration against the shaped charge. Exper- iments also support this evidence.展开更多
This study investigates the ricochet behaviour of three different small-arms projectile types using a novel ricochet measuring device.The results can be used to estimate the danger potential of ricochets on shooting r...This study investigates the ricochet behaviour of three different small-arms projectile types using a novel ricochet measuring device.The results can be used to estimate the danger potential of ricochets on shooting ranges.A ricochet is the change of direction and velocity of a projectile after impacting an oblique surface.This impact produces strong vibrations on a rigid plate.During this impact,flexural waves travel radially outwards from the point of impact.These waves are used to determine the properties of the impactor with accelerometers situated on the target surface.With the use of two measurement plates,one can produce a ricochet and detect the velocity at the same time.Accelerometers are suitable for accurate momentum measurements of single impacts.However,depending upon strike velocity and the impact angle,a ricochet can separate in multiple fragments after being deflected.From the operational safety perspective,these fragments need to be detected,as well.The approach of a coupled sensor concept was chosen to solve this problem.Thermographic sensors were additionally used to visualise the heat which is produced after penetrating a rubber layer pasted in front of the steel target plate.With this approach one was able to detect the position of impact.The investigations showed that the measurement system performance is better with a multiple sensor design,which includes accelerometers for the velocity,impact strength and partly the position measurement,while the thermographic sensor was used for the position measurement and partly the momentum measurement.The investigated ammunition showed plausible fragmentation behaviour,and the results can already be used to estimate the danger potential of different ammunition types.Frangible projectiles fragment to small particles already after being deflected under a small angle.However,Full Metal Jacket projectiles with or without a steel core do not fragment under angles which are less than 5.The objective of the paper is to demonstrate the possibility of measuring the complex ricochet mechanics of small projectiles using standard accelerometers with the adequate signal processing approach.This measuring system is supported by an off the shelf thermographic camera.展开更多
Production of ceramic armour solutions on-demand/in-theatre would have significant logistical and military advantages.However,even assuming that such technologies could be successfully deployed in the field,such near ...Production of ceramic armour solutions on-demand/in-theatre would have significant logistical and military advantages.However,even assuming that such technologies could be successfully deployed in the field,such near net-shape manufacturing technology is relatively immature compared to conventional sintering of ceramics.In this study,the ballistic performance of a series of additively manufactured(AM)/rapidly-prototyped(RP)alumina tiles of 97.2%of the density of Sintox FATM were investigated using both forward-and reverse-ballistic experiments.These experiments,undertaken with compressed gasguns,employed the depth-of-penetration technique and flash X-ray as primary diagnostics to interrogate both efficiency of penetration and projectile-target interaction,respectively.The RP alumina was found to exhibit useful ballistic properties,successfully defeating steel-cored(AP)7.62×39 mm BXN rounds at velocities of up-to c.a.850 m/s,while exhibiting comparable failure modes to conventionally sintered armour-grade Sintox FATM.However,where a<1%by vol.Cu dopant was introduced into the RP material failure modes changed dramatically with performance dropping below that of conventionally sintered alumina.Overall,the results from both sets of experiments were complimentary and clearly indicated the potential of such RP materials to play an active role in provision of real-world body armour solutions provided quality control of the RP material can be maintained.展开更多
Most commercially available spine analogues are not intended for biomechanical testing,and the few that are suitable for using in conjunction with implants and devices to allow a hands-on practice on operative procedu...Most commercially available spine analogues are not intended for biomechanical testing,and the few that are suitable for using in conjunction with implants and devices to allow a hands-on practice on operative procedures are very expensive and still none of these offers patient-specific analogues that can be accessed within reasonable time and price range.Man-made spine analogues would also avoid the ethical restrictions surrounding the use of biological specimens and complications arising from their inherent biological variability.Here we sought to improve the biofidelity and accuracy of a patient-specific motion segment analogue that we presented recently.These models were made by acrylonitrile butadiene styrene(ABS)in 3D printing of porcine spine segments(T12-L5)from microCT scan data,and were tested in axial loading at 0.6 mm.min-1(strain rate range 6×10^-4 s^-1-10×10^-4 s^-1).In this paper we have sought to improve the biofidelity of these analogue models by concentrating in improving the two most critical aspects of the mechanical behaviour:the material used for the intervertebral disc and the influence of the facet joints.The deformations were followed by use of Digital Image Correlation(DIC)and consequently different scanning resolutions and data acquisition techniques were also explored and compared to determine their effect.We found that the selection of an appropriate intervertebral disc simulant(PT Flex 85)achieved a realistic force/displacement response and also that the facet joints play a key role in achieving a biofidelic behaviour for the entire motion segment.We have therefore overall confirmed the feasibility of producing,by rapid and inexpensive 3D-printing methods,high-quality patient-specific spine analogue models suitable for biomechanical testing and practice.展开更多
Most commercial spine analogues are not intended for biomechanical testing,and those developed for this purpose are expensive and yet still fail to replicate the mechanical performance of biological specimens.Patient-...Most commercial spine analogues are not intended for biomechanical testing,and those developed for this purpose are expensive and yet still fail to replicate the mechanical performance of biological specimens.Patient-specific analogues that address these limitations and avoid the ethical restrictions surrounding the use of human cadavers are therefore required.We present a method for the production and characterisation of biofidelic,patient-specific,Spine Motion Segment(SMS=2 vertebrae and the disk in between)analogues that allow for the biological variability encountered when dealing with real patients.Porcine spine segments(L1-LA)were scanned by computed tomography,and 3D models were printed in acrylonitrile butadiene styrene(ABS).Four biological specimens and four ABS motion segments were tested,three of which were further segmented into two Vertebral Bodies(VBs)with their intervertebral disc(IVD).All segments were loaded axially at 0.6 mm·min-1(strain-rate range 6×10-4 s-1-10×10-4 s-1).The artificial VBs behaved like biological segments within the elastic region,but the best two-part artificial IVD were^15%less stiffthan the biological IVDs.High-speed images recorded during compressive loading allowed full-field strains to be produced.During compression of the spine motion segments,IVDs experienced higher strains than VBs as expected.Our method allows the rapid,inexpensive and reliable production of patient-specific 3D-printed analogues,which morphologically resemble the real ones,and whose mechanical behaviour is comparable to real biological spine motion segments and this is their biggest asset.展开更多
文摘The experimental investigations of the effect of contact time/temperature on initiating the cook-off using 7.62 mm calibre cartridge cases(CC) were conducted previously.These cartridges were hlled with commercial off-the-shelf(COTS) double based(DB) propellant(Bulls Eye)and were loaded in a hot chamber.The thermal explosion temperature is of great significance to both weapon designers and safety inspectors as it provides the operational limit and safe operating temperature.For CC under test,it was found that the cook-off temperatures of this propellant were encountered with the heat transfer profile of the simulated gun barrel between 151.4 ℃ and 153.4 ℃,with a reaction occurring in less than300 s after the round was chambered.Usefully,each experiment was found to be consistent and repeatable.
基金sponsored by EPSRC ICASE Grant reference 1700064BAE Systems。
文摘This paper gives a succinct review of dual-spinprojectile stability and some technologies relating to them.It describes how the traditional stability factors from linear projectile theory are modified to better describe a controlled dual-spin projectile.Finally,it reviews works which have investigated how different aspects of a controlled dual-spin design can affect flight stability,primarily airframe structure and canard properties.A conclusion is given,highlighting important guidelines from the enclosed discussions.
文摘Occasionally, the Whipple shields are used for the protection of a space station and a satellite against the meteoroids and orbital debris. In the Whipple shields each layer of the shield depletes part of high speed projectile en- ergy either by breaking the projectile or absorbing its energy. Similarly, this investigation uses the Whipple shields against the shaped charge to protect the light armour such as infantry fighting vehicles with a little modification in their design. The unsteady multiple interactions of shaped charge jet with the Whipple shield package against the steady homogeneous target is scrutinized to optimize the shield thickness. Sim- ulations indicate that the shield thickness of 0.75 mm offers an optimum configuration against the shaped charge. Exper- iments also support this evidence.
文摘This study investigates the ricochet behaviour of three different small-arms projectile types using a novel ricochet measuring device.The results can be used to estimate the danger potential of ricochets on shooting ranges.A ricochet is the change of direction and velocity of a projectile after impacting an oblique surface.This impact produces strong vibrations on a rigid plate.During this impact,flexural waves travel radially outwards from the point of impact.These waves are used to determine the properties of the impactor with accelerometers situated on the target surface.With the use of two measurement plates,one can produce a ricochet and detect the velocity at the same time.Accelerometers are suitable for accurate momentum measurements of single impacts.However,depending upon strike velocity and the impact angle,a ricochet can separate in multiple fragments after being deflected.From the operational safety perspective,these fragments need to be detected,as well.The approach of a coupled sensor concept was chosen to solve this problem.Thermographic sensors were additionally used to visualise the heat which is produced after penetrating a rubber layer pasted in front of the steel target plate.With this approach one was able to detect the position of impact.The investigations showed that the measurement system performance is better with a multiple sensor design,which includes accelerometers for the velocity,impact strength and partly the position measurement,while the thermographic sensor was used for the position measurement and partly the momentum measurement.The investigated ammunition showed plausible fragmentation behaviour,and the results can already be used to estimate the danger potential of different ammunition types.Frangible projectiles fragment to small particles already after being deflected under a small angle.However,Full Metal Jacket projectiles with or without a steel core do not fragment under angles which are less than 5.The objective of the paper is to demonstrate the possibility of measuring the complex ricochet mechanics of small projectiles using standard accelerometers with the adequate signal processing approach.This measuring system is supported by an off the shelf thermographic camera.
文摘Production of ceramic armour solutions on-demand/in-theatre would have significant logistical and military advantages.However,even assuming that such technologies could be successfully deployed in the field,such near net-shape manufacturing technology is relatively immature compared to conventional sintering of ceramics.In this study,the ballistic performance of a series of additively manufactured(AM)/rapidly-prototyped(RP)alumina tiles of 97.2%of the density of Sintox FATM were investigated using both forward-and reverse-ballistic experiments.These experiments,undertaken with compressed gasguns,employed the depth-of-penetration technique and flash X-ray as primary diagnostics to interrogate both efficiency of penetration and projectile-target interaction,respectively.The RP alumina was found to exhibit useful ballistic properties,successfully defeating steel-cored(AP)7.62×39 mm BXN rounds at velocities of up-to c.a.850 m/s,while exhibiting comparable failure modes to conventionally sintered armour-grade Sintox FATM.However,where a<1%by vol.Cu dopant was introduced into the RP material failure modes changed dramatically with performance dropping below that of conventionally sintered alumina.Overall,the results from both sets of experiments were complimentary and clearly indicated the potential of such RP materials to play an active role in provision of real-world body armour solutions provided quality control of the RP material can be maintained.
基金We acknowledge the work,skill and expertise of Karl Norris and the mechanical workshop of Cranfield University,Shrivenham,and Jolyon Cleaves of Vision Research for providing the high-speed cameras.Ethical approval was granted by the Cranfield University Research and Ethics committee(CURES).This paper is dedicated to our friend and colleague Dr Mike Gibson,whose untimely death is a great loss to us all.
文摘Most commercially available spine analogues are not intended for biomechanical testing,and the few that are suitable for using in conjunction with implants and devices to allow a hands-on practice on operative procedures are very expensive and still none of these offers patient-specific analogues that can be accessed within reasonable time and price range.Man-made spine analogues would also avoid the ethical restrictions surrounding the use of biological specimens and complications arising from their inherent biological variability.Here we sought to improve the biofidelity and accuracy of a patient-specific motion segment analogue that we presented recently.These models were made by acrylonitrile butadiene styrene(ABS)in 3D printing of porcine spine segments(T12-L5)from microCT scan data,and were tested in axial loading at 0.6 mm.min-1(strain rate range 6×10^-4 s^-1-10×10^-4 s^-1).In this paper we have sought to improve the biofidelity of these analogue models by concentrating in improving the two most critical aspects of the mechanical behaviour:the material used for the intervertebral disc and the influence of the facet joints.The deformations were followed by use of Digital Image Correlation(DIC)and consequently different scanning resolutions and data acquisition techniques were also explored and compared to determine their effect.We found that the selection of an appropriate intervertebral disc simulant(PT Flex 85)achieved a realistic force/displacement response and also that the facet joints play a key role in achieving a biofidelic behaviour for the entire motion segment.We have therefore overall confirmed the feasibility of producing,by rapid and inexpensive 3D-printing methods,high-quality patient-specific spine analogue models suitable for biomechanical testing and practice.
基金an internal grant from Cranfield University(CF)a project grant from the Royal Centre for Defence Medicine(RCDM)Birming-ham(PZ)by in kind support from Vision Research.The authors have no conflicts of interest to declare.We acknowledge the work,skill and expertise offered by Karl Norris in the mechanical workshop of Cranfield University,and Jolyon Cleaves of Vision Research for providing the high-speed cameras.Ethical approval was granted by Cranfield University Research and Ethics committee(CURES)approval reference CURES/1014/2016.This paper is dedicated to one of the authors,Dr Mike Gjbson,whose untimely death is a great loss to us all.
文摘Most commercial spine analogues are not intended for biomechanical testing,and those developed for this purpose are expensive and yet still fail to replicate the mechanical performance of biological specimens.Patient-specific analogues that address these limitations and avoid the ethical restrictions surrounding the use of human cadavers are therefore required.We present a method for the production and characterisation of biofidelic,patient-specific,Spine Motion Segment(SMS=2 vertebrae and the disk in between)analogues that allow for the biological variability encountered when dealing with real patients.Porcine spine segments(L1-LA)were scanned by computed tomography,and 3D models were printed in acrylonitrile butadiene styrene(ABS).Four biological specimens and four ABS motion segments were tested,three of which were further segmented into two Vertebral Bodies(VBs)with their intervertebral disc(IVD).All segments were loaded axially at 0.6 mm·min-1(strain-rate range 6×10-4 s-1-10×10-4 s-1).The artificial VBs behaved like biological segments within the elastic region,but the best two-part artificial IVD were^15%less stiffthan the biological IVDs.High-speed images recorded during compressive loading allowed full-field strains to be produced.During compression of the spine motion segments,IVDs experienced higher strains than VBs as expected.Our method allows the rapid,inexpensive and reliable production of patient-specific 3D-printed analogues,which morphologically resemble the real ones,and whose mechanical behaviour is comparable to real biological spine motion segments and this is their biggest asset.
