CERES :: Browsing by Author "Wood, David C."

Browsing by Author "Wood, David C."

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Open Access
The bactericidal effect of shock waves
(Institute of Physics, 2014-05-07) Leighs, James Allen; Appleby-Thomas, Gareth J.; Wood, David C.; Goff, Michael J.; Hameed, Amer; Hazell, Paul J.
There are a variety of theories relating to the origins of life on our home planet, some of which discuss the possibility that life may have been spread via inter-planetary bodies. There have been a number of investigations into the ability of life to withstand the likely conditions generated by asteroid impact (both contained in the impactor and buried beneath the planet surface). Previously published data regarding the ability of bacteria to survive such applied shockwaves has produced conflicting conclusions. The work presented here used an established and published technique in combination with a single stage gas gun, to shock and subsequently recover Escherichia coli populations suspended in a phosphate buffered saline solution. Peak pressure across the sample region was calculated via numerical modelling. Survival data against peak sample pressure for recovered samples is presented alongside control tests. SEM micrographs of shocked samples are presented alongside control sets to highlight key differences between cells in each case.
Open Access
Ballistic behaviour of explosively shattered alumina and silicon carbide targets
(Maney Publishing, 2011-12-31T00:00:00Z) Nanda, H.; Appleby-Thomas, Gareth J.; Wood, David C.; Hazell, Paul J.
The resistance offered by three ceramic materials of varying strength that have been subjected to explosive loading has been investigated by depth-of-penetration testing. Each material was completely penetrated by a tungsten carbide cored projectile and the residual penetration into a ductile aluminium alloy backing material was measured. The resulting ballistic performance of each damaged ceramic was found to be similar implying that the resistance offered to the projectile by the damaged ceramic is not dependent on the intrinsic strength properties of the intact material. This was taken as evidence that the important controlling parameter for enhancing the ballistic performance of a damaged ceramic material was not the strength of the ceramic but rather the fragment morphology.
Open Access
Blast mitigation using polymeric 3D printed auxetic lattice structures - a preliminary study
(SAGE, 2021-10-18) Critchley, Richard; Hazael, Rachael; Bhatti, Kamran; Wood, David C.; Peare, Alan; Johnson, Stephen; Temple, Tracey J.
Protection of critical infrastructure in an urban environment is a challenging task, specifically against the vehicle bourne improvised explosive device threat. To design infrastructure to withstand this evolving threat, novel solutions and advanced materials need to be developed. One such material of interest are auxetics. This study experimentally analysed the mitigation of blast response of auxetic re-entrant honeycomb structures, with geometries varying between −ve 30° and +ve 30° using additive manufacturing (3D printing) techniques and non-explosive loading via shock tube. Re-entrant auxetic structures (−ve 15°) exhibited repeatable blast mitigation of 23% and reduced the transmitted pressure and impulse of the blast wave. Further highlighting their potential application as a protective measure to enhance a structures blast survivability.
Open Access
Damping of post-impact vibrations
(Elsevier, 2019-08-22) Muster, Michael; Amer, Hameed; Wood, David C.; Appleby-Thomas, Gareth J.; Wasmer, Kilian
During the impact of a body on a plate, flexural waves are set which travel circularly outwards from the point of impact. These waves can be used to determine the properties of the impacting body. For accurate measurements, it is advantageous if both the flexural and compression waves pass the sensor just once without being backscattered or reflected from the boundaries. In this paper, various plate shapes are analysed to evaluate the shape which offers the best damping properties against an impact. Experimental analysis indicated that the reflection of the flexural waves can be halved using a plate with star-shaped 60° edges with a damping layer. The damping properties can be further doubled by using a star-shaped plate with power law edges in combination with a damping layer which is attached to the edges. The work reported here offers a possible solution to get significant damping properties. This is achieved by combining a damping layer with edge shaping against a strong single excitation event. The results demonstrate that it is a promising approach for an impact detection systems which could be equally applicable to acoustic damping applications.
Open Access
Dynamic qualitative bolt force measurements for investigating influence factors on the pushout effect of small calibre ammunition
(AIP Publishing, 2019-06-25) Muster, Michael; Hameed, Amer; Wood, David C.
A small calibre weapon system consists of the weapon and the ammunition. In the case of bolt action rifles during the process of firing, the breech is a rigid bearing which prevents the casing from being pushed out. However, not the whole pushout force is taken by the bolt. Due to friction forces at the casing boundary, the chamber of the weapon can absorb a significant part of the pushout force. The duration of the pushout force is in the order of milliseconds. Piezoelectric strain gauges are capable of recording such short time events qualitatively. To increase the measurability of force obtained from raw signal, is filtered using a bandpass filter and applying a signal envelope. The results from the strain gauges are verified by a piezoelectric force washer. In this paper, two different lubrication states and two different casing materials are analysed to evaluate their influences on the force absorbed by the bolt. The analysis indicated that lubricated casings lead to bolt forces which are more than three times higher when compared unlubricated casings. The unlubricated steel casing also showed a significant lower bolt force when compared with the regular brass casing. However, this effect is reversed, if the casing is lubricated. This work demonstrates how to measure highly dynamic events. The acquired results can be directly applied to 5.56x45 bolt action rifles. These measurements may also have a significant influence on self-loading rifles, since the process of reloading is also dependent on the pushout force. The general application area is target competitive shooting and military purposes.
Open Access
The dynamic response of dense 3 dimensionally printed polylactic acid
(Springer, 2019-05-22) Agu, Henry; Hameed, Amer; Appleby-Thomas, Gareth J.; Wood, David C.
Polylactic acid (PLA) is commonly used as a feedstock material for commercial 3D printing. As components manufactured from such material become more commonplace, it is inevitable that some of the resultant systems will be exposed to high strain-rate/impact events during their design-life (for example, components being dropped or even involved in a high-speed crash). To this end, understanding the shock properties of polylactic acid, in its role as a major raw material for 3D printed components, is of particular importance. In this work, printed samples of PLA were deformed by one-dimensional shock waves generated via the plate impact technique, allowing determination of both the Hugoniot Equation of State (EOS) and shear strength of the material. Both linear and non-linear EOS forms were considered in the US-Up plane, with the best-fit found to take the general form US=1.28+3.06−1.09Up2" role="presentation" style="display: inline-table; line-height: normal; letter-spacing: normal; word-spacing: normal; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border-width: 0px; border-style: initial; position: relative;">US=1.28+3.06−1.09U2pUS=1.28+3.06−1.09Up2 in the Us−Up" role="presentation" style="display: inline-table; line-height: normal; letter-spacing: normal; word-spacing: normal; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border-width: 0px; border-style: initial; position: relative;">Us−UpUs−Up plane, consistent with other polymers. Use of lateral Manganin gauges embedded in the material flow allowed consideration of lateral stress evolution at impact pressures ranging from 0.3 to 4.0 GPa. Shear strength was observed to increase with impact stress, however, with minimal strengthening behind the shock front. Deviation of the measured stress from the predicted elastic measurement (corresponding to the PLA’s Hugoniot Elastic Limit) was observed at longitudinal stress of 0.90 ± 0.05 GPa, within range of polymeric materials of similar characteristics—the first time this important parameter has been measured for PLA. As a result, this material characterisation will allow numerical modellers to accurately predict the structural response of PLA-based components/structures against high strain rates such as impacts or drops.
Open Access
The effects of changing chemistry on the shock response of basic polymers
(Springer, 2016-07-11) Millett, Jeremy C. F.; Brown, Eric N.; Gray III, George T.; Bourne, Neil K.; Wood, David C.; Appleby-Thomas, Gareth J.
The shock response of four common semicrystalline thermoplastic polymers—polyethylene (PE), polyvinylchloride (PVC), polytetrafluoroethylene (PTFE) and polychlorotrifluoroethylene (PCTFE)—have been studied in terms of their Hugoniots, release velocities and shear strengths. Through the variations in behaviour caused by changes to the attached atoms to the carbon backbone, it has been possible to suggest that there are two main factors in play. The first is an electrostatic repulsion between adjacent polymer chains. Where this force is large, for example in PTFE with highly electronegative fluorine atoms, this results in this force dominating the shock response, with low shock velocities, high release velocities and little if no hardening behind the shock front. In contrast, in materials such as PE, this force is now weaker, due to the lower electronegativity of hydrogen, and hence this force is easier to overcome by the applied shock stress. Now the main factor affecting shock behaviour is controlled by the shape of the polymer chain allowing inter chain tangling (tacticity). This results in higher shock velocities, lower release speeds and significant hardening behind the shock front as the chains are forced together. This is prevalent in materials with a relatively open structure such as PE and is enhanced with the presence of large side groups or atoms off the main polymer chain.
Open Access
The effects of quasi-one-dimensional shock on Escherichia coli while controlling pressure and temperature
(Elsevier, 2020-11-28) Fitzmaurice, Brianna C.; Appleby-Thomas, Gareth J.; Painter, Jonathan; Wood, David C.; Hazael, Rachael
The response of microorganisms to high pressures is of growing interest in the literature, regarding areas of research including the sterilisation of foodstuffs, panspermia and, more generally, the study of extremophiles. When examining organisms under shock pressure, there are a number of caveats that need to be considered, including temperature and the nature of the shock wave front. Both of these caveats have been explored in this study through the application of the plate impact technique to create quasi-one-dimensional shock waves with controlled shock fronts through bacterial targets. This was achieved using typical planar flyer plates to study the dynamic pressure response of the bacterium, Escherichia coli NCTC 10538. Additionally, in order to create an adiabatic, off-Hugoniot loading path, a novel graded areal density flyer produced by the Surfi-Sculpt® approach was used to assess the effects of lowering temperature during shock on E. coli growth rates. The maximum temperature generated by a Surfi-Sculpt® flyer impact was 5 K less than that produced by the planar flyer analogue. Higher growth rates of bacterial colonies post-impact by the Surfi-Sculpt® flyer compared to those by the planar flyer were observed, with this behaviour determined to be a possible function of the nature, although temperature was also decreased with the use of this adiabatic ramp loading technique. In an effort to purposefully increase pressure and temperature for the E. coli samples, a modified form of a previously developed bacterial encapsulation system was also employed in this study, allowing pressures of up to 10 GPa and growth rates of up to 0.09% to be reached.
Open Access
Fragmentation studies by non-explosive cylinder expansion technique
(Elsevier, 2020-09-04) Rao, Prakash; Painter, Jonathan; Appleby-Thomas, Gareth J.; Critchley, Richard; Wood, David C.; Roberts, Andrew; Hazael, Rachael
Expansion and fragmentation of metallic cylinders is an important area of study both for designing munitions and mitigation techniques against fragments as well as in the failure of pressurised pipes in industry. Most of the reported studies on fragmentation have been carried out by detonating explosively filled metallic cylinders. However, this approach has inherent limitations in terms of both safety and repeatability – not least due to packing issues with explosive fills. Fragmentation studies on hollow metallic cylinders of both mild and stainless steel of various thicknesses (2–4 mm) were carried out by firing a polycarbonate projectile from a single-stage light gas gun. Strain rates of the order of 2 × 104 s−1 were observed at cylinder expansion velocities of 400–450 m s−1, calculated from flash X-ray radiographs. The differences in fragmentation behaviour of both materials was observed, attributed to their different response to high strain-rate loadings. Microscopic analysis of mild steel fragments showed interesting alignment of ferrite and pearlite grains, similar to reported effects of explosive loading. This suggests the potential to employ this technique to simulate explosive cylinder expansion in a non-explosive laboratory environment enabling a convenient recovery of fragments. Numerical modelling with using ANSYS AUTODYN® allowed for a better understanding of the various parameters controlling expansion and fragmentation. Analysis of recovered fragments by a Fragment Weight Distribution Map (FWDM), a method generally used for characterising pipe bombs, could clearly demonstrate the effect of casing material and thickness.
Open Access
Gas gun ramp loading of Kel-F 81 targets using a ceramic graded areal density flyer system
(Elsevier, 2015-03-06) Goff, Michael J.; Hazell, Paul J.; Appleby-Thomas, Gareth J.; Wood, David C.; Stennett, Christopher
Kel-F 81 (PCTFE/Polychlorotrifluoroethylene) polymer targets were subjected to ramp loadings generated by a ceramic flyer accelerated into the targets by a gas gun in the plate impact configuration. This approach used a ceramic graded areal density flyer in conjunction with a ceramic buffer plate to induce a ramp loading in the target. The flyer was comprised of a rapid prototyped alumina ceramic. The loading was observed with embedded electromagnetic particle velocity gauges (PV gauges) with the results compared with ANSYS Autodyn™ hydrocode simulations. Experimental results show that ramp loadings of varying duration and magnitude were induced into the target. These loadings can be described as shockless compressions leading to shocked states within the material. In addition, numerical simulations provided further insight into the loading approach – with good agreement found with experimental data, opening the potential to design more complex loading systems in future.
Open Access
Investigation of the high-strain rate (shock and ballistic) response of the elastomeric tissue simulant Perma-Gel®
(Elsevier, 2016-04-01) Appleby-Thomas, Gareth J.; Wood, David C.; Hameed, Amer; Painter, Jonathan; Le-Seelleur, Victoria; Fitzmaurice, Brianna C.
For both ethical and practical reasons accurate tissue simulant materials are essential for ballistic testing applications. A wide variety of different materials have been previously adopted for such roles, ranging from gelatin to ballistics soap. However, while often well characterised quasi-statically, there is typically a paucity of information on the high strain-rate response of such materials in the literature. Here, building on previous studies by the authors on other tissue analogues, equation-of-state data for the elastomeric epithelial/muscular simulant material Perma-Gel® is presented, along with results from a series of ballistic tests designed to illustrate its impact-related behaviour. Comparison of both hydrodynamic and ballistic behaviour to that of comparable epithelial tissues/analogues (Sylgard® and porcine muscle tissue) has provided an insight into the applicability of both Perma-Gel® and, more generally, monolithic simulants for ballistic testing purposes. Of particular note was an apparent link between the high strain-rate compressibility (evidenced in the Hugoniot relationship in the Us-up plane) and subsequent ballistic response of these materials. Overall, work conducted in this study highlighted the importance of fully characterising tissue analogues – with particular emphasis on the requirement to understand the behaviour of such analogues under impact as part of a system as well as individually.
Open Access
Lateral stress evolution in chromium sulfide cermets with varying excess chromium
(2016-07-01) Petel, Oren E.; Appleby-Thomas, Gareth J.; Wood, David C.; Capozzi, Alexander; Nabavi, Seyed Ali; Goroshin, Samuel; Frost, David L.; Hazell, Paul J.
The shock response of chromium sulfide-chromium, a cermet of potential interest as a matrix material for ballistic applications, has been investigated at two molar ratios. Using a combustion synthesis technique allowed for control of the molar ratio of the material, which was investigated under near-stoichiometric (cermet) and excess chromium (interpenetrating composite) conditions, representing chromium:sulfur molar ratios of 1.15:1 and 4:1, respectively. The compacts were investigated via the plate-impact technique, which allowed the material to be loaded under a onedimensional state of strain. Embedded manganin stress gauges were employed to monitor the temporal evolution of longitudinal and lateral components of stress in both materials. Comparison of these two components has allowed assessment of the variation of material shear strength both with impact pressure/strain-rate and time for the two molar ratio conditions. The two materials exhibited identical material strength despite variations in their excess chromium contents
Open Access
Material strength evolution of FCC metals under high strain rates
(2020-12) Gilroy-Hirst, Caitlin; Hazael, Rachael; Wood, David C.; Akhavan, Jacqueline
Copper and stainless steel 21-6-9, two face-centred cubic (FCC) materials, were shock loaded in partially recovered uniaxial strain flyer-plate impact experiments at varying impact pressures (6 GPa - 16 GPa). These samples were collected post impact via three differing recovery configurations: (1) standard or ‘free boundary’; (2) partial shock recovery, i.e. using both ‘momentum trapping’ and ‘soft recovery’ techniques but with a flyer plate thickness of 10 mm to see the effects on partial tensile release in the rear spall plates of an established recovery target design; finally (3) a traditional full recovery comparison with a 2 mm flyer impact. These samples were then analysed using a suite of analytical techniques including X ray diffraction, optical microscopy, hardness testing and compression after impact testing, to observe the material deformation characteristics in the simplified partially recovered shock and release condition compared to the more complex ‘standard’ release wave situation. A control sample of a ‘ fully recovered’ sample was also carried out for comparative purposes. The rear spall plates were modified on these partially recovered samples to see the effect that this had on the tensile release waves and how this changed the material deformation properties overall. Results for the stainless steel 21-6-9 demonstrated the ability of the partial shock recovery technique (hereafter called ‘partial-recovery’) to mitigate the reverberations compared to that of the standard samples. Upon analysis of the targets, it was observed that the dislocation density was generally lower for the partially recovered samples but varied with impact pressure for both the standard and recovered configuration. For the stainless steel recovery experiments an increasing dislocation density from 4 x 1015 m-2 at 6 GPa to 6.5 x 1015 m-2 at 12 GPa was observed which then decreased to 5.5 x 1015 m-2 at 16 GPa. The twinning density to grain ratio obtained from optical microscopy showed a linear increase (y= 1.5345x - 8.3508) with an R2 value of 0.8295 from 7 GPa at 4 twins per grain to 17 twins per grain at 16 GPa. Twinning density is indicative of a successful recovery, where a successful recovery is a reduction in reverberations in the sample and in a full recovery is a 1D shock. The dataset both verifies the use and success of the recovery technique as well as demonstrating the materials characteristics under partial-recovery, while observing reverberation effects.
Open Access
Novel approaches to breech force and bullet ricochet measurement for small arms fire
(2020-04) Muster, Michael; Hameed, Amer; Wood, David C.; Wasmer, Kilian
Small arms ammunition measurements are difficult to conduct. This is especially true in the field of internal and terminal ballistics. However, accurate measurements are important for safety considerations. Danger zones are defined as an area on shooting ranges in which there is a high risk of harm. Risk driving factor for the size of the danger zone is the ammunition used, properties and ricochet behaviour of the specific ammunition design. The danger zone is of interest because a wrong estimation may lead to unwanted damage to the shooter’s far environment. The distant environment is less affected when it comes to weapon breech damage. However, the internal ballistic breech investigation during the process of firing is of high relevance for the safety considerations of the shooter. The purpose of this study is to show the influence of novel ballistic measurement devices on recent safety considerations. It is an experimental research study that looks at internal and terminal ballistic effects. The pushout force was investigated with a separately developed weapon breech, capable of measuring loads in a dynamic manner. The other investigated parameter was the ricochet danger which was also investigated with a device developed during the project. Both parameters lead to new safety considerations. During this thesis it became evident that the most relevant parameter for an accurate ricochet quantification is the momentum of the fragment. This measurement is possible thanks to a novel type of accelerometer equipped sensor plates developed in this work. The other main finding of this thesis is the fact that lubricated ammunition casings, irrespective of whether with water or oil lubrication, leads to a significant rise in pushout force. This pushout force is taken up by the breech and leads to safetyrelevant rises of internal forces on the breech. Both measurement approaches need to be taken into account when it comes to future safety considerations of small arms fire.
Open Access
On differences in the equation-of-state for a selection of seven representative mammalian tissue analogue materials
(Elsevier, 2017-10-10) Appleby-Thomas, Gareth J.; Fitzmaurice, Brianna; Hameed, Amer; Painter, Jonathan; Gibson, Michael C.; Wood, David C.; Hazael, Rachael; Hazell, Paul J.
Tissue analogues employed for ballistic purposes are often monolithic in nature, e.g. ballistic gelatin and soap, etc. However, such constructs are not representative of real-world biological systems. Further, ethical considerations limit the ability to test with real-world tissues. This means that availability and understanding of accurate tissue simulants is of key importance. Here, the shock response of a wide range of ballistic simulants (ranging from dermal (protective / bulk) through to skeletal simulant materials) determined via plate-impact experiments are discussed, with a particular focus on the classification of the behaviour of differing simulants into groups that exhibit a similar response under high strain-rate loading. Resultant Hugoniot equation-of-state data (Us-up; P-v) provides appropriate feedstock materials data for future hydrocode simulations of ballistic impact events.
Open Access
On the dynamic behavior of three readily available soft tissue simulants
(American Institute of Physics (AIP), 2011-12-31) Appleby-Thomas, Gareth J.; Hazell, Paul J.; Wilgeroth, James Michael; Shepherd, C. J.; Wood, David C.; Roberts, A.
Plate-impact experiments have been employed to investigate the dynamic response of three readily available tissue simulants for ballistic purposes: gelatin, ballistic soap (both subdermal tissue simulants), and lard (adipose layers). All three materials exhibited linear Hugoniot equations-of-state in the US-uP plane. While gelatin behaved hydrodynamically under shock, soap and lard appeared to strengthen under increased loading. Interestingly, the simulants under test appeared to strengthen in a material-independent manner on shock arrival (tentatively attributed to a rearrangement of the amorphous molecular chains under loading). However, material-specific behavior was apparent behind the shock. This behavior appeared to correlate with microstructural complexity, suggesting a steric hindrance effect.
Open Access
On the effects of powder morphology on the post-comminution ballistic strength of ceramics
(Elsevier, 2016-10-29) Appleby-Thomas, Gareth J.; Wood, David C.; Hameed, Amer; Painter, Jonathan; Fitzmaurice, Brianna C.
In this paper in order to try and elucidate the effects of particle morphology on ballistic response of comminuted systems, a series of experiments were carried out via the use of powder compacts with differing initial particle morphologies. This approach provided a route to readily manufacture comminuted armour analogues with significantly different microstructural compositions. In this study pre-formed `fragmented-ceramic' analogues were cold-pressed using plasma-spray alumina powders with two differing initial morphologies (angular and spherical). These compacts were then impacted using 7.62-mm FFV AP (Förenade Fabriksverken Armour Piercing) rounds with the subsequent depth-of-penetration of the impacting projectile into backing Al 6082 blocks used to provide a measure of pressed ceramic ballistic response. When material areal density was accounted for via differing ballistic efficiency calculations a strong indication of particle morphology influence on post-impact ceramic properties was apparent. These results were reinforced by a separate small series of plate-impact experiments, whose results indicated that powder morphology had a strong influence on the nature of compact collapse.
Open Access
On the interpretation of lateral manganin gauge stress measurements in polymers
(American Institute of Physics (AIP), 2010-12-31) Appleby-Thomas, Gareth J.; Hazell, Paul J.; Wilgeroth, James Michael; Wood, David C.
Encapsulated wire-element stress gauges enable changes in lateral stress during shock loading to be directly monitored. However, there is substantial debate with regards to interpretation of observed changes in stress behind the shock front; a phenomenon attributed both to changes in material strength and shock- dispersion within the gauge-encapsulation. Here, a pair of novel techniques which both modify or remove the embedding medium where such stress gauges are placed within target materials have been used to try and inform this debate. The behavior of three polymeric materials of differing complexity was considered, namely polystyrene, the commercially important resin transfer moulding RTM 6 resin and a commercially available fat lard. Comparison to the response of embedded gauges has suggested a possible slight decrease in the absolute magnitude of stress. However, changing the encapsulation has no detectable effect on the gradient behind the shock in such polymeric systems.
Open Access
On the shock behaviour and response of Ovis Aries vertebrae
(European Society of Biomechanics, 2016-07-10) Wood, David C.; Appleby-Thomas, Gareth J.; Fitzmaurice, Brianna; Franceskides, Constantinos; Shanker, Tobias; Zioupos, Peter; Samra, Amarjit
When investigating a biological system during shock loading, it is best practice to isolate different components to fully comprehend each individual part [1,2] before building up the system as a whole. Due to the high acoustic impedance of bone in comparison to other biological tissues [3] the majority of the shock will be transmitted into this medium, and as such can cause large amounts of damage to other parts of the body potentially away from the impact area.
Open Access
Push-out force and impulse measurement of seven types of small arms ammunition with three different surface states
(AIP, 2019-11-18) Muster, Michael; Hameed, Amer; Wood, David C.; Wasmer, Kilian
This study analyzes the influence of lubrication treatments on the force absorbed by the breech bolt called push-out force. The results are of high interest for weapon-safety and durability studies, especially when it comes to weapon maintenance. A barrel-ammunition combination represents an expanding vessel under high pressure. The pressure rises from ambient up to 420 MPa in less than a millisecond. During such a highly dynamic process, purely static equations, describing the problem of the casing push-out force, may not be applied. Besides the dynamic behavior, the surface properties and geometry also play an important role. To investigate the push-out force, a measurement system based on a force washer was built. This system was validated using a crusher method and finite element analysis. The impulse was calculated using the data of the measured force to obtain additional information about the force-time properties of the push-out behavior. Untreated ammunition and two lubrication systems: “ice layer” and “oil lubricated,” as well as seven different ammunition sizes ranging from 5.56 to 12.7 mm were considered. The response was the force absorbed by the bolt while the cartridge provides rear obturation to the combustion gases. It was found that both the casing geometry and its treatments have a significant influence on the push-out force.