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
The debris from exploded buildings can ricochet after colliding with the ground,thus increasing the debris travel distance and danger from any associated impacts or collisions.To reduce this danger,the travel distance...The debris from exploded buildings can ricochet after colliding with the ground,thus increasing the debris travel distance and danger from any associated impacts or collisions.To reduce this danger,the travel distance of ricocheted debris must be accurately predicted.This study analyzed the change in the travel distance of ricocheted concrete debris relative to changes in the properties of a sand medium.Direct shear tests were conducted to measure the change in internal friction angle as a function of temperature and water content of the sand.Finite element analysis(FEA)was then applied to these variables to predict the speed and angle of the debris after ricochet.The FEA results were compared with results of low-speed ricochet experiments,which employed variable temperature and water content.The travel distance of the debris was calculated using MATLAB,via trajectory equations considering the drag coefficient.As the internal friction angle decreased,the shear stress decreased,leading to deeper penetration of the debris into the sand.As the loss of kinetic energy increased,the velocity and travel distance of the ricocheted debris decreased.Changes in the ricochet velocity and travel distance of the debris,according to changes in the internal friction angle,indicated that the debris was affected by the environment.展开更多
The impact of a bullet by firearm is a mortal entity that in recent years has been on the rise due to the increase in crime,confrontations,among other acts of violence.Brain injuries by firearm account for 33.3% of al...The impact of a bullet by firearm is a mortal entity that in recent years has been on the rise due to the increase in crime,confrontations,among other acts of violence.Brain injuries by firearm account for 33.3% of all fatal injuries from this type of weapon.This resulted in a significant number of disabilities with its burden cost at a global level.The types of bullet injuries to the head include:penetrating (inlet without outlet),perforating (through and through),tangential (not enter the skull,causing coupe injury),ricochet (intracranial bouncing of bullet) and careening (rare.enter skull but not brain,runs in the subdural space).There are several situations that can occur once the bullet enters the body or into the intracranial cavity.Unmatched association of the bullet trajectory with the final position of the bullet within the body raise the suspicion for additional phenomena involvement,this can be explained by either internal bullet ricochet or internal bullet migration.The former usually represents an active movement and the latter is a passive movement.Intracranial ricocheting of bullets forms up to 25% of all penetrating bullet injuries to the skull.Such bullets types are commonly tumbling and have an unpredictable trajectory.The surgical management for intracranial bullet injury developed over decades from the time of Harvey Cushing and the World War I till the present.Now,the accepted intervention ranges from simple wound care to a proper surgery that includes hematoma evacuation,removal of only accessible bone fragments and foreign bodies,dural repair and wound debridement with or without decompressive craniectomy.Also.intracranial pressure monitoring is generally indicated.We reported a thirty-three years old male.victim of homicidal bullet injury to the head.presented with Glasgow Coma Scale score of 8 (best eye response:2.best motor response:4,best verbal response:2),upon examination a right parietal (near vertex) inlet without outlet was found.The poor prognostic factors in this patient included bi-hemispheric involvement,associated acute subdural hematoma with interhemispheric extension,ricochet type of injury and effacement of sulci.Intracranial ricocheted-bullet injury is a special entity of bullet injury to the head with its particular ballistics and management that deserve highlighting by the trauma team to gain fluent treatment and better outcome.展开更多
We examine the ricochet and penetration behavior in sand, water and gelatin by steel spheres, 7.62 mm APM2 and 25 mm projectiles. A threshold impact angle(critical angle) exists beyond which ricochet cannot occur. The...We examine the ricochet and penetration behavior in sand, water and gelatin by steel spheres, 7.62 mm APM2 and 25 mm projectiles. A threshold impact angle(critical angle) exists beyond which ricochet cannot occur. The Autodyn simulation code with the smooth particle hydrodynamic(SPH) method and Impetus Afea Solver with the corpuscular model are used and the results are compared with experimental and analytical results. The resistance force in sand for spheres was proportional to a term quadratic in velocity plus a term linear in velocity. The drag coefficient for the quadratic term was 0.65. The Autodyn and Impetus Afea codes simulate too large penetration due to the lack of a linear velocity resistance force. Critical ricochet angles were consistent with analytical results in the literature. In ballistic gelatin at velocities of 50–850 m/s a drag coefficient of 0.30 fits the high speed camera recordings if a linear velocity resistance term is included. However, only a quadratic velocity resistance force with drag coefficient that varies with the Reynolds number also fits the measurements. The simulation of a sphere in water with Autodyn showed too large drag coefficient. The 7.62 mm APM2 core simulations in sand fit reasonable well for both codes. The 25 mm projectile ricochet simulations in sand show consistency with the high speed camera recordings. Computer time was reduced by one to two orders of magnitudes when applying the Impetus Afea Solver compared to Autodyn code due to the use of the graphics processing units(GPU).展开更多
为研究钨合金长杆体在侵彻薄装甲钢靶板上的跳飞特性，在1300~1700 m/s 速度范围，利用 LS-DYNA对6~14 mm厚度靶板进行了数值模拟，采用每次调整0.5＆#176;着角逐步趋近的方法得出相应的跳飞角。不同靶板厚度仿真结果表明：长杆体在斜...为研究钨合金长杆体在侵彻薄装甲钢靶板上的跳飞特性，在1300~1700 m/s 速度范围，利用 LS-DYNA对6~14 mm厚度靶板进行了数值模拟，采用每次调整0.5＆#176;着角逐步趋近的方法得出相应的跳飞角。不同靶板厚度仿真结果表明：长杆体在斜侵彻薄装甲钢靶板的过程中形成了连接点向前推进的塑性铰链，且随着靶板厚度的均匀增加，着角因素对跳飞影响呈强化趋势，而靶板厚度因素呈弱化趋势。加入靶板厚度因素对 Tate跳飞模型进行了修正，并进行相应的验证试验，二者所得结果均与数值模拟结果吻合得较好。展开更多
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.
基金This study was financially supported by the Foundation Research Program[grant number UD170027GD]of the Agency for Defense Development and the Defense Acquisition Program Administration of the Republic of Korea.
文摘The debris from exploded buildings can ricochet after colliding with the ground,thus increasing the debris travel distance and danger from any associated impacts or collisions.To reduce this danger,the travel distance of ricocheted debris must be accurately predicted.This study analyzed the change in the travel distance of ricocheted concrete debris relative to changes in the properties of a sand medium.Direct shear tests were conducted to measure the change in internal friction angle as a function of temperature and water content of the sand.Finite element analysis(FEA)was then applied to these variables to predict the speed and angle of the debris after ricochet.The FEA results were compared with results of low-speed ricochet experiments,which employed variable temperature and water content.The travel distance of the debris was calculated using MATLAB,via trajectory equations considering the drag coefficient.As the internal friction angle decreased,the shear stress decreased,leading to deeper penetration of the debris into the sand.As the loss of kinetic energy increased,the velocity and travel distance of the ricocheted debris decreased.Changes in the ricochet velocity and travel distance of the debris,according to changes in the internal friction angle,indicated that the debris was affected by the environment.
文摘The impact of a bullet by firearm is a mortal entity that in recent years has been on the rise due to the increase in crime,confrontations,among other acts of violence.Brain injuries by firearm account for 33.3% of all fatal injuries from this type of weapon.This resulted in a significant number of disabilities with its burden cost at a global level.The types of bullet injuries to the head include:penetrating (inlet without outlet),perforating (through and through),tangential (not enter the skull,causing coupe injury),ricochet (intracranial bouncing of bullet) and careening (rare.enter skull but not brain,runs in the subdural space).There are several situations that can occur once the bullet enters the body or into the intracranial cavity.Unmatched association of the bullet trajectory with the final position of the bullet within the body raise the suspicion for additional phenomena involvement,this can be explained by either internal bullet ricochet or internal bullet migration.The former usually represents an active movement and the latter is a passive movement.Intracranial ricocheting of bullets forms up to 25% of all penetrating bullet injuries to the skull.Such bullets types are commonly tumbling and have an unpredictable trajectory.The surgical management for intracranial bullet injury developed over decades from the time of Harvey Cushing and the World War I till the present.Now,the accepted intervention ranges from simple wound care to a proper surgery that includes hematoma evacuation,removal of only accessible bone fragments and foreign bodies,dural repair and wound debridement with or without decompressive craniectomy.Also.intracranial pressure monitoring is generally indicated.We reported a thirty-three years old male.victim of homicidal bullet injury to the head.presented with Glasgow Coma Scale score of 8 (best eye response:2.best motor response:4,best verbal response:2),upon examination a right parietal (near vertex) inlet without outlet was found.The poor prognostic factors in this patient included bi-hemispheric involvement,associated acute subdural hematoma with interhemispheric extension,ricochet type of injury and effacement of sulci.Intracranial ricocheted-bullet injury is a special entity of bullet injury to the head with its particular ballistics and management that deserve highlighting by the trauma team to gain fluent treatment and better outcome.
文摘We examine the ricochet and penetration behavior in sand, water and gelatin by steel spheres, 7.62 mm APM2 and 25 mm projectiles. A threshold impact angle(critical angle) exists beyond which ricochet cannot occur. The Autodyn simulation code with the smooth particle hydrodynamic(SPH) method and Impetus Afea Solver with the corpuscular model are used and the results are compared with experimental and analytical results. The resistance force in sand for spheres was proportional to a term quadratic in velocity plus a term linear in velocity. The drag coefficient for the quadratic term was 0.65. The Autodyn and Impetus Afea codes simulate too large penetration due to the lack of a linear velocity resistance force. Critical ricochet angles were consistent with analytical results in the literature. In ballistic gelatin at velocities of 50–850 m/s a drag coefficient of 0.30 fits the high speed camera recordings if a linear velocity resistance term is included. However, only a quadratic velocity resistance force with drag coefficient that varies with the Reynolds number also fits the measurements. The simulation of a sphere in water with Autodyn showed too large drag coefficient. The 7.62 mm APM2 core simulations in sand fit reasonable well for both codes. The 25 mm projectile ricochet simulations in sand show consistency with the high speed camera recordings. Computer time was reduced by one to two orders of magnitudes when applying the Impetus Afea Solver compared to Autodyn code due to the use of the graphics processing units(GPU).
