Browsing by Author "Wasmer, Kilian"

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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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    Novel approaches to breech force and bullet ricochet measurement for small arms fire
    (2020-04) Mister, Michael; Hameed, Amer; Wasmer, Kilian
    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 safety-relevant 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 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.