Nonlinear Material Behavior Analysis under High Compression Pressure in Dynamic Conditions

Muhammad Zubair Zahid,Tauqeer Iqbal,Zhang Faping,Shahid Ikramullah Butt,Syed Zohaib Ejaz

doi:10.1155/2017/3616932

Abstract

Gun chamber pressure is an important parameter in proofing of ammunition to ensure safety and reliability. It can be measured using copper crushers or piezoelectric sensor. Pressure calculations in copper crusher method are based on linear plastic deformation of copper after firing. However, crusher pressure deformation at high pressures deviates from the corresponding values measured by piezoelectric pressure transducers due to strain rate dependence of copper. The nonlinear deformation rate of copper at high pressure measurements causes actual readings from copper crusher gauge to deviate from true pressure values. Comparative analysis of gun chamber pressure was conducted for 7.62 × 51 mm ammunition using Electronic Pressure, Velocity, and Action Time (EPVAT) system with piezoelectric pressure transducers and conventional crusher gauge. Ammunitions of two different brands were used to measure chamber pressure, namely, NATO standard ammunition and non-NATO standard ammunition. The deformation of copper crushers has also been simulated to compare its deformation with real time firing. The results indicate erratic behavior for chamber pressure by copper crusher as per standard deviation and relative spread and thus prove piezo sensor as more reliable and consistent mode of peak pressure measurement. The results from simulation, cost benefit analysis, and accuracy clearly provide piezo sensors with an edge over conventional, inaccurate, and costly method of copper crusher for ballistic measurements due to its nonlinear behavior.

Highlights

Proof is a destructive test in which small numbers of proof samples are selected as representative of a large group known as lot or batch of the ammunition by the same manufacturer and process
In order to validate pressure values obtained from copper crushers through series of real time firing of ammunition, the pressure obtained through deformation of copper crusher was taken as reference and validated through ANSYS workbench
Based on experimental and numerical analysis, it is evident that the piezo pressure observed is higher than copper crusher pressure at 25 mm distance from chamber end

Summary

Introduction

Proof is a destructive test in which small numbers of proof samples are selected as representative of a large group known as lot or batch of the ammunition by the same manufacturer and process. Proofing of ammunition is important to ensure the safety, reliability, and operational effectiveness of conventional ammunition. The importance of proofing is often poorly understood, leading to failure in ammunition safety and stability. Proof of ammunition is a systematic method of evaluating the properties, characteristics, and performance capabilities of ammunition throughout its life cycle. It is used to assess the reliability, safety, and operational effectiveness of stocks. Proof is the functional testing or firing of ammunition and explosives to ensure safety and stability in storage and intended use. In-service proof and the surveillance of ammunition are undertaken to ensure that the ammunition continues to meet the required quality standards throughout its life [1]

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Discussion

Conclusion