br Experimental tests and results

Experimental tests and results
Discussion Table 8 shows the success of the geometric similarity measured by means of the peak pressures for the open-end blast chamber. The pressure time history ibotenic acid manufacturer invariant by geometric similarity. One of the series of tests confirmed geometric similarity between Emily and SEmily, namely the 5 kg and 40 g Comp B charges. The similarity for the 3 kg and 24 g Comp B charges is not confirmed to the same accuracy.
Conclusion Despite the differences noted in the previous section, the use of ANSYS AUTODYN to calculate the pressure reflections due to the pendulum door (Sections 3 and 5.3) was helpful and contributed to the understanding of the problem during the design phase. Pointing out the shortcomings of the hydrocode may lead to improvements in the material modelling of explosives in confined spaces.
Acknowledgement The authors would like to thank the staff in the workshop at LS, CSIR under the leadership of Mr L Broodryk for their support in manufacturing SEmily and the staff at DBEL for support during the experimental tests. The financial support from ARMSCOR is acknowledged.
Introduction Ricochet occurs when the final velocity vector of the center of mass of a projectile is oriented away from the target and is associated with small impact angles or high obliquity (obliquity is defined as the angle between the normal surface vector and the velocity vector of the center of mass of the projectile). The ricochet angle and the ricochet velocity are dependent on the impact velocity, obliquity angle, yaw, mass of the projectile, geometry, moment of inertia and target properties. A threshold impact angle (critical angle) exists beyond which ricochet cannot occur. However, the relationship between critical impact angle, projectile nose shape, amount of water, mineralogy and impact velocity is still not fully understood [1].
Penetration and ricochet in sand by spheres and 7.62 APM2 projectiles
Conclusions and discussion
Acknowledgment
Introduction Many parameters determine the outcome of a ballistic test. Even for depth-of-penetration experiments with tungsten-heavy-alloy (WHA) rod penetrators against semi-infinite rolled-homogeneous-armor (RHA) steel targets, a variety of parameters come into play. Examples are impact velocity, yaw angle, target obliquity and material properties [1–6]. Some of those parameter variations are of statistical nature and controllable in an experiment within some scatter. Others are rather systematic types of error, such as variations between material lots that could occur, e.g. if the quality of a reference target material changes over time. The target material hardness class is known to have a strong effect on penetration results. A number of investigations are published addressing Figure eight issue. For example, the work done by Rapacki et al. [7] analyzes the coarse effects of hardness for large variations of the full relevant armor steel hardness range from below 200 BHN up to 600 BHN. Penetration formulae, e.g. by Lanz and Odermatt [8], take care of those dependencies, too. We address the case of relatively small variations that are within the range of a single target material hardness class, i.e. that are compatible with the same specification. This is of relevance as often ballistic results obtained with material of different origin in different series are compared or combined rather than repeating expensive tests with same-grade material. From the data correction for hardness effects done by Rosenberg et al. in [9], the significance of this problem for such small hardness differences emerges implicitly. However, we are not aware of a publicly available data set allowing for a more systematic analysis of such effects within a narrow hardness regime.
Experimental parameters
Results
Analysis
Conclusions For material class hardness variations from 280 BHN to 330 BHN, the semi-infinite penetration depths of a length L = 90 mm rod penetrator, a decrease of penetration depth of about −6 mm can be attributed to hardness variation (neglecting yaw influence). At 1250 m/s this is equal to around −12% of the reference penetration. At 1780 m/s the relative change diminishes to −6%.