Browsing by Author "Muster, Michael"

Now showing 1 - 6 of 6
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    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.
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    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
    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.
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    Novel approaches to breech force and bullet ricochet measurement for small arms fire
    (2020-04) Muster, Michael; Ameed, A; Wood, D; Wasmer, K
    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.
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    Push out Measurements of Ammunition under Dynamic Conditions
    (Cranfield University, 2020-01-07 15:18) Muster, Michael
    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. The analysis presented in this poster indicated that different lubricated or wet casing surfaces lead to bolt forces which are more than three times higher when compared unlubricated casings. This poster shows also how to measure highly dynamic events. The acquired results can be directly applied to 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
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    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; 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.
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    Ricochet quantification using a multiple sensor approach
    (Elsevier, 2020-02-20) Muster, Michael; Hameed, Amer; Wood, David
    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.