Ballistic experiments were conducted on thin steel plates that are normally impacted by hemisphericalnosed projectiles at velocities higher than their ballistic limits. The deformation and failure modes of the thin st...Ballistic experiments were conducted on thin steel plates that are normally impacted by hemisphericalnosed projectiles at velocities higher than their ballistic limits. The deformation and failure modes of the thin steel plates were analyzed. A new method was proposed according to the experimental results and the perforation phenomenon of the thin steel plates to determine the radius of the bulging region. In establishing this new method, a dynamic method combined with the plastic wave propagation concept based on the rigid plastic assumption was adopted. The whole perforation process was divided into four consecutive stages, namely, bulging deformation, dishing deformation, ductile hole enlargement, and projectile exit. On the basis of the energy conservation principle, a new model was developed to predict the residual velocities of hemispherical-nosed projectiles that perforate thin steel plates at low velocities.The results obtained from the theoretical calculations by the present model were compared with the experimental results. Theoretical predictions were in good agreement with the experimental results in terms of both the radius of the bulging region and the residual velocity of the projectile when the strain rate effects of the target material during each stage were considered.展开更多
The paper describes field test results of 7.62×51 mm M61 AP(armour piercing) ammunition fired into mild steel targets at an outdoor range.The targets varied from 10 mm to 32 mm in thickness.The tests recorded pen...The paper describes field test results of 7.62×51 mm M61 AP(armour piercing) ammunition fired into mild steel targets at an outdoor range.The targets varied from 10 mm to 32 mm in thickness.The tests recorded penetration depth,probability of perforation(i.e.,complete penetration),muzzle and impact velocities,bullet mass,and plate yield strength and hardness.The measured penetration depth exhibited a variability of approximately±12%.The paper then compared ballistic test results with predictive models of steel penetration depth and thickness to prevent perforation.Statistical parameters were derived for muzzle and impact velocity,bullet mass,plate thickness,plate hardness,and model error.A Monte-Carlo probabilistic analysis was then developed to estimate the probability of plate perforation of 7.62 mm M61 AP ammunition for a range of impact velocities,and for mild steels,and High Hardness Armour(HHA) plates.This perforation fragility analysis considered the random variability of impact velocity,bullet mass,plate thickness,plate hardness,and model error.Such a probabilistic analysis allows for reliability-based design,where,for example,the plate thickness with 95% reliability(i.e.only 1 in 20 shots will penetrate the wall) can be estimated knowing the probabilistic distribution of perforation.Hence,it was found that the plate thickness to ensure a low 5% probability of perforation needs to be 11-15% thicker than required to have a 50/50 chance of perforation for mild steel plates.Plates would need to be 20-30% thicker if probability of perforation is reduced to zero.展开更多
The construction of grouting butt joints of bamboo tubes is simple and efficient.However,when the joint is bent,the low tensile strength of the mortar easily leads to cracking of the mortar prior to the failure of the...The construction of grouting butt joints of bamboo tubes is simple and efficient.However,when the joint is bent,the low tensile strength of the mortar easily leads to cracking of the mortar prior to the failure of the bamboo tube.In this paper,a comparative test of the bending capacity was performed on grouting butt joints reinforced by nonperforated,fully perforated,and semiperforated steel plates embedded in bamboo tubes to obtain the loaddisplacement curves and ultimate bearing capacity of various specimens.The strengthening effect of CFRP pasted on bamboo tubes was also studied.The results show that the opening at the end of the steel plate is beneficial to resist the slip between the mortar and steel plate,while the complete section in the middle of the steel plate is conducive to making full use of the tensile strength of the steel plate.Therefore,it is best to insert the semiperforated steel plate with openings in the end and without openings in the middle into the mortar to enhance the bending properties of the grouting butt joint,which can make the failure mode of the joint change from brittle failure of mortar to ductile compression failure of bamboo tube.In addition,pasting CFRP sheets on the external wall of the bamboo tube helps to reduce the tensile stress of the mortar,while increasing the width of the steel plate can increase the bending moment of inertia of the mixture of the steel plate and mortar.These two complementary measures are very effective in delaying the cracking of the bamboo tube and improving the bending capacity of the joint.展开更多
Conventional fusion arc welding of high-strength quenched and tempered steel can be improved through the use of non-conventional laser beam welding. This article presents the investigations of autogenous bead on plate...Conventional fusion arc welding of high-strength quenched and tempered steel can be improved through the use of non-conventional laser beam welding. This article presents the investigations of autogenous bead on plate and butt CO<sub>2</sub> Laser Welding (LW) of 7 mm thick high-strength quenched and tempered low alloy SM570 (JIS) steel plates. The influence of laser welding parameters, mainly welding speed, defocusing distance and shielding gas flow rate on the weld profile, i.e., weld zone penetration depth and width, microstructure and mechanical properties of welded joints was determined. All welded joints showed smooth and uniform weld beads free from superficial porosity and undercuts. The selected best welding conditions were a laser power of 5.0 kW, welding speed of 500 mm/min, argon gas shielding flow rate of 30 L/min and a defocusing distance of -0.5 mm. It was observed that these conditions gave complete penetration and minimized the width of the weld bead. The microstructure of the welded joints was evaluated by light optical microscopy. The weld metal (WM) and heat-affected zone (HAZ) near weld metal achieved maximum hardness (355 HV). The tensile fractured samples showed the ductile mode of failure and ultimate tensile strength of 580 MPa.展开更多
基金financially supported by the National Security Major Foundation Research Project(973)of China(6133050102)the National Natural Science Foundation of China(Grant No.51409253)
文摘Ballistic experiments were conducted on thin steel plates that are normally impacted by hemisphericalnosed projectiles at velocities higher than their ballistic limits. The deformation and failure modes of the thin steel plates were analyzed. A new method was proposed according to the experimental results and the perforation phenomenon of the thin steel plates to determine the radius of the bulging region. In establishing this new method, a dynamic method combined with the plastic wave propagation concept based on the rigid plastic assumption was adopted. The whole perforation process was divided into four consecutive stages, namely, bulging deformation, dishing deformation, ductile hole enlargement, and projectile exit. On the basis of the energy conservation principle, a new model was developed to predict the residual velocities of hemispherical-nosed projectiles that perforate thin steel plates at low velocities.The results obtained from the theoretical calculations by the present model were compared with the experimental results. Theoretical predictions were in good agreement with the experimental results in terms of both the radius of the bulging region and the residual velocity of the projectile when the strain rate effects of the target material during each stage were considered.
基金The authors appreciate the laboratory assistance of Goran Simundic and Michael Goodwin for assistance with measurement of the field test results The assistance of final year honours student Richard Szlicht is gratefully acknowledged.
文摘The paper describes field test results of 7.62×51 mm M61 AP(armour piercing) ammunition fired into mild steel targets at an outdoor range.The targets varied from 10 mm to 32 mm in thickness.The tests recorded penetration depth,probability of perforation(i.e.,complete penetration),muzzle and impact velocities,bullet mass,and plate yield strength and hardness.The measured penetration depth exhibited a variability of approximately±12%.The paper then compared ballistic test results with predictive models of steel penetration depth and thickness to prevent perforation.Statistical parameters were derived for muzzle and impact velocity,bullet mass,plate thickness,plate hardness,and model error.A Monte-Carlo probabilistic analysis was then developed to estimate the probability of plate perforation of 7.62 mm M61 AP ammunition for a range of impact velocities,and for mild steels,and High Hardness Armour(HHA) plates.This perforation fragility analysis considered the random variability of impact velocity,bullet mass,plate thickness,plate hardness,and model error.Such a probabilistic analysis allows for reliability-based design,where,for example,the plate thickness with 95% reliability(i.e.only 1 in 20 shots will penetrate the wall) can be estimated knowing the probabilistic distribution of perforation.Hence,it was found that the plate thickness to ensure a low 5% probability of perforation needs to be 11-15% thicker than required to have a 50/50 chance of perforation for mild steel plates.Plates would need to be 20-30% thicker if probability of perforation is reduced to zero.
基金The authors are grateful for the financial support of the National Key Research and Development Program of China(2017YFC0703500).
文摘The construction of grouting butt joints of bamboo tubes is simple and efficient.However,when the joint is bent,the low tensile strength of the mortar easily leads to cracking of the mortar prior to the failure of the bamboo tube.In this paper,a comparative test of the bending capacity was performed on grouting butt joints reinforced by nonperforated,fully perforated,and semiperforated steel plates embedded in bamboo tubes to obtain the loaddisplacement curves and ultimate bearing capacity of various specimens.The strengthening effect of CFRP pasted on bamboo tubes was also studied.The results show that the opening at the end of the steel plate is beneficial to resist the slip between the mortar and steel plate,while the complete section in the middle of the steel plate is conducive to making full use of the tensile strength of the steel plate.Therefore,it is best to insert the semiperforated steel plate with openings in the end and without openings in the middle into the mortar to enhance the bending properties of the grouting butt joint,which can make the failure mode of the joint change from brittle failure of mortar to ductile compression failure of bamboo tube.In addition,pasting CFRP sheets on the external wall of the bamboo tube helps to reduce the tensile stress of the mortar,while increasing the width of the steel plate can increase the bending moment of inertia of the mixture of the steel plate and mortar.These two complementary measures are very effective in delaying the cracking of the bamboo tube and improving the bending capacity of the joint.
文摘Conventional fusion arc welding of high-strength quenched and tempered steel can be improved through the use of non-conventional laser beam welding. This article presents the investigations of autogenous bead on plate and butt CO<sub>2</sub> Laser Welding (LW) of 7 mm thick high-strength quenched and tempered low alloy SM570 (JIS) steel plates. The influence of laser welding parameters, mainly welding speed, defocusing distance and shielding gas flow rate on the weld profile, i.e., weld zone penetration depth and width, microstructure and mechanical properties of welded joints was determined. All welded joints showed smooth and uniform weld beads free from superficial porosity and undercuts. The selected best welding conditions were a laser power of 5.0 kW, welding speed of 500 mm/min, argon gas shielding flow rate of 30 L/min and a defocusing distance of -0.5 mm. It was observed that these conditions gave complete penetration and minimized the width of the weld bead. The microstructure of the welded joints was evaluated by light optical microscopy. The weld metal (WM) and heat-affected zone (HAZ) near weld metal achieved maximum hardness (355 HV). The tensile fractured samples showed the ductile mode of failure and ultimate tensile strength of 580 MPa.
