Darcie Dennis Koller

Low Pressure Hugoniot for U‐Nb (6 wt.%)

Over the last several years, many experiments have been conducted to study the dynamic response of U‐Nb (6 wt.%) alloy. An understanding of the physical mechanisms governing the behavior of this material is necessary to develop robust physical models for today’s hydrocodes. Previous experiments indicate that the dynamic response of this alloy is strongly dependant on the initial microstructure of the material. Using a well characterized material, a series of low pressure shock experiments were conducted at the single stage light gas gun facility at Los Alamos National Laboratory. Time resolved particle velocity measurements were made using VISAR. Absolute VISAR system timing was measured and cross correlated to shock breakout time to allow hugoniot points to be calculated. These shots provide both low pressure Hugoniot points for U‐Nb (6 wt.%) alloy and a better constraint on the dynamic material response.

The influence of shock loading on material properties and dynamic damage evolution.

Many commercial and defense applications require structural metals for extreme environments. Specifically, automotive, aerospace, and infrastructure applications need materials with damage tolerance during dynamic loading. To this end, many studies have examined dynamic deformation and damage evolution. These studies have shown that kinetics of loading are critically important to damage evolution of bulk metals. Particularly, in dynamic loading environments in which a shock wave is imparted to the metal, kinetic and spatial effects based on shock wave shape play important roles in damage. These studies also show that depending on crystal structure, shock loading can alter the subsequent properties of a material significantly. However, while these phenomena are gaining acceptance in the dynamic damage community, the ability to predict these phenomena is limited. Here, the influence of dynamic loading across strain rates 103–106/s will be discussed. The role of test platforms and crystallography to examine ...

TRIDENT flyer plate Impact technique: comparison to gas gun plate impact technique

This report describes the details of a series of plate impact experiments that were conducted on a gas gun in an effort to validate a new technique for plate impact using the TRIDENT laser to launch thin flyers. The diagnostics fielded were VISAR and identical samples and impactors were used on both platforms. All experimenters agree that the VISAR results should have agreed between the two experimental platforms. The VISAR results did not agree across the platforms and experimenters offer explanations and implications for this outcome.

DYNAMIC PROPERTIES OF A PB‐SB ALLOY

Lead is a material of fundamental scientific interest because of its relatively low melting point and ductility. Alloys of lead are used for practical reasons which include the desire to have a slightly harder form of the metal to be able to handle without damage. A practical question is how lead and alloys with small amounts of alloying element respond to dynamic loading. Here we report the results of fundamental shock wave compression experiments on an alloy of lead that contains approximately 3.5 wt.% antimony. Good results for several dynamic properties have been obtained, and are reported here.

INFLUENCE OF MICROSTRUCTURE ON THE BAUSCHINGER EFFECT AND THE SHOCK HARDENING IN 1080 HIGH‐CARBON STEEL

The importance of a microstructurally‐controlled Bauschinger component to defect storage during the shock loading process has been shown to be correlated to both quasi‐elastic release effects and reduced shock hardening in materials. In the current study shock recovery experiments have been conducted on a high‐carbon 1080 steel as a function of three microstructural states; pearlitic, partially‐spheriodized, and where the cementite has been fully spheriodized. The 1080 steel in the pearlitic condition is shown to exhibit a significant Bauschinger effect while the fully spheriodized microstructure is observed to display significantly higher shock hardening when shock prestrained to an equivalent 12.8 GPa. The shock hardening response of 1080 steel is discussed in terms of the micromechanisms controlling defect generation and storage during shock loading in materials and the importance of the Bauschinger effect on modeling shock hardening in some materials.

SHOCKWAVE PROFILE AND BAUSCHINGER EFFECT IN DEPLETED URANIUM

Dynamic damage evolution in materials is of growing interest, in particular, the role of defect structure on material strength during a dynamic experiment. Many studies in the past have seen strong correlations between the shockwave profile and the defect structure during dynamic experiments, such as quasi‐elastic release behavior. Bauschinger effect is a microstructurally controlled process in which a material displays a change in stress‐strain characterisitics due to a change in the defect structure. Studies on depleted uranium have revealed indications of Bauschinger effect being a mechanism present during quasi‐static experiments, which could be a result of the large amount of twinning observed in these materials. As work continues to improve strength models, it becomes imperitive to understand the role of defect structure on the properties of materials under dynamic conditions. The study reported here is an observation of the release wave behavior in depleted uranium that first undergoes compressive ...