Shot-By-Shot Erosion Modeling of Retired 120mm M256 Gun Tube #1988
Abstract
As our gun erosion database increases for in-service and out-of-service 120mm M256 tubes with M829Ax series rounds, distinct erosion patterns and mechanisms are emerging. Variability exists for M256 guns with M829Ax series rounds depending on round count, round type, round conditioning temperature, and their order. Our Materials Ablation Conduction Erosion (MACE) M256/M829A2 gun system erosion model, with its interior ballistics, thermochemistry, and boundary layer components, is constantly being refined by this erosion data. A recent refinement includes the improvement of the gun steel subsurface exposure model due to high quality-difficult to obtain data from in-service M256 tubes. Another recent refinement includes the improvement-incorporation of case gas laminar cooling-turbuluent mixing effects and forcing cone induced vena contracts effects into the boundary layer heat transfer model based on thermal data from M236 tubes. This second refinement is calibrated as a function of axial position by chromium- plate-recrystallization and gun steel-transformation temperature depths. A comprehensive gun erosion model is described for the 120mm M256 gun with its M829Ax series rounds. In addition, a detailed shot-by- shot erosion modeling prediction is described for retired 120mm M256 gun tube serial number 1988. For this gun tube, the erosion prediction includes the two types of rounds fired (M829, M829A2) and the three conditioning temperatures for each round (hot, ambient, cold). The gun erosion mechanism consists of heat checking of the inert chromium plate, subsequent interfacial degradation of the subsurface gun steel substrate at the chromium crack bases, subsequent chromium platelet spalling, and subsequent bare gun steel gas wash. This gun erosion model correctly predicts that the worst eroded region (3 mm deep) is at 1.2 - 2.4 meters RFT and that the excessive muzzle wear (chromium loss without gun steel gas wash) is by a different purely mechanical mechani7
Document Details
- Document Type
- Technical Report
- Publication Date
- Jul 15, 1998
- Accession Number
- ADA420114
Entities
People
- C. Rickard
- G. Pflegi
- P. O’hara
- P. Vottis
- S. Sopok