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Understanding Your Accident Model
Published in Sidney Dekker, The Field Guide to Understanding ‘Human Error’, 2017
A barrier model can faithfully explain the last few minutes (or seconds, or perhaps hours, depending on the time constants in your domain) before an accident. One reason for this is that it might make sense, in many domains, to see risk during those final minutes or seconds as energy that is not contained (a drug with a high therapeutic index, for example, or two aircraft that come too close to each other in the sky). The “physical cause” of the loss of the Space Shuttle Columbia in February 2003 was “a breach in the Thermal Protection System on the leading edgeof the left wing. The breach was initiated by a piece of insulating foam that separated from the left bipod ramp of the External Tank and struck the wing in the vicinity of the lower half of Reinforced Carbon-Carbon panel 8 at 81.9 seconds after launch. During re-entry, this breach in the Thermal Protection System allowed superheated air to penetrate the leading-edge insulation and progressively melt the aluminum structure of the left wing, resulting in a weakening of the structure until increasing aerodynamic forces caused loss of control, failure of the wing, and breakup of the Orbiter.”5
The space shuttle
Published in Jonathan Allday, Apollo in Perspective, 2019
In essence, Columbia was lost on re-entry due to a breach in the Thermal Protection System (TPS) during launch. A piece of thermal insulation foam broke off the external tank some 82 s into the launch sequence and struck the left wing of the orbiter near the area where the leading edge curves away from the main body (Figure 8.17). The impact damaged the Reinforced Carbon−Carbon (RCC) panels on the lower leading edge of the wing.
Response Surface Modelling and Effective Application of Adaptive Neuro-Fuzzy Inference System to Analyze Surface Roughness of Al/Gr/Cp5 MMC Machined using WEDM
Published in Australian Journal of Mechanical Engineering, 2023
Mangesh Phate, Shraddha Toney, Vikas Phate
The matrix material used in the present study was Aluminium 2124 whose chemical composition consists of 92.2–94.7% aluminium, 3.8–4.9% copper, 0.1% chromium, 0.3% Iron, 1.2–1.8% magnesium, 0.3–0.9% manganese, 0.15% titanium, 0.25% zinc, 0.2% silicon, while graphite powder was used as reinforcing material with chemical composition of 95% carbon, 0.5% iron and 0.4% sulphur. The mechanical properties of Al/Gr/Cp5 MMC are ultimate tensile strength (145.27 MPa), BHN (27), the density of 2.7 g/cc3, and Poisson’s ratio 0.33. The melting point is 5100 ℃ and the elastic modulus is within 70–80 GPa. Graphite is used in carbon fibre reinforced plastics and in heat-resistant composites such as reinforced carbon–carbon (RCC). The graphite density is between 1.3 and 1.95 g/, and the elastic modulus is 8–15 GPa. The microscopic structure of the Al/Gr/Cp5 MMC is as shown in Figures 2.