Muzzleloading rifles (also known as “muzzleloaders”) can be safe and enjoyable firearms for shooting and hunting if handled properly. There are a number of muzzleloader constructs such as inline, flint lock and percussion. These firearms operate on the ignition of black powder propellant or approved substitute charge. There are a number of mechanisms that can be utilized to ignite the powder (e.g. primers, percussion caps, etc.); once the powder is ignited, the pressure builds up rapidly and then decreases as the projectile moves down the barrel and the volume of the gas behind the projectile increases. If circumstances arise that impede the motion of the projectile, such as an obstruction, then a marked over-pressurization event may occur causing ductile fracture of the barrel. Often, the location of the fracture(s) and the deformation of the barrel provide clues as to the type of obstruction. In this study, we investigate several examples of obstructions causing over-pressurization events that led to ductile fracture of the barrels.
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On early morning of July 30, 2004, in GHISLENGHIEN’s industrial area, Belgium, a worker of one of the industry field company informs the Fire Department (FD) of a potential gaz-leak problem within the fully new company’s building. FD and the Gaz Distribution Company arrive quickly on site for checking any potential leakages … at 8h56 AM, a large explosion occurs spreading a 120 [m] height fire gerb, visible 15 [km] away, blasting building’s debris over 6 [km] all around, leading to shock wave felt 20[km] farer. A large heavy portion (~11 [m], many tons) of 1 of the 2 large scale (DN 800 and DN 1000), 80 bars high pressure natural gaz pipeline bridging the gas terminal of ZEEBRUGGE (100 [km] more in the North) to France has just been blown out nearly 200[m] away … the intense heat felt up to 2 [km] around subsequent to the explosion makes 23 deaths & 132 injuries (mainly burned at different degrees)… This talk reviews the events and main probable disaster’s causes (2nd-most critical accident in Belgium after the 1956’s “Le bois du Cazier” (262 deaths). The speech wants also to put in evidence the “human factor” in terms of communication.
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Polymethylmethacrylate (PMMA) or acrylic transparencies are extensively used for commercial and military aircraft throughout the world. The sudden, mid-flight fractures of acrylic transparencies necessitated the imposition of crippling flight limitations on an entire fleet of jet fighters. This presentation will discuss the failure analysis performed on the jet fighter canopy failures including fractographic analysis, materials testing, stress analysis, and fracture mechanics assessment.
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Several inhibitors extracted from medicinal plants were analyzed. The results showed that the green inhibitor based on some plants is the better anti-corrosion product for API X52 and X70 steels in the 1M solution of hydrochloric acid compared to commercial inhibitors used by oil companies in transport and storage. In this new project, we set the following objectives: to provide sufficient convincing scientific evidence to replace synthetic inhibitors that are very expensive and toxic to humans and the environment; to open a new line of research, promising to develop a new family of inexpensive inhibitors from bio-sources, and to offer the new products for protection against corrosion in different branch of industry. This project has a triple result: to fight against corrosion, to valorise the natural resource and to propose an effective product against corrosion at very competitive cost. Creating an enterprise to make the inhibitor is an evident sequel”
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On July 28, 2012, a Boeing 787-8 airplane experienced a loss of thrust in the right GEnx turbofan engine during a pre-flight, low speed taxi test at Charleston International Airport in Charleston, South Carolina. Inspection of the engine revealed the forward end of the fan midshaft had separated, causing the low-pressure turbine rotor to shift aft, damaging that section of the engine. A detailed investigation performed by the NTSB and General Electric found the fan midshaft on the GEnx engine had separated from an environmentally assisted cracking mechanism under static load. Cracking was predicated by an intricate and previously undetected reaction between the fan midshaft ultra-high strength steel, the dry film lubricant, and the assembly aid. This investigation explored multiple and fundamental aspects of the fan midshaft, including manufacturing, assembly, design, and loading. From the investigation, a non-destructive inspection was developed and employed throughout the fleet with multiple changes to the assembly of the GEnx engine to prevent future reoccurrences.
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Traditional classical design methodologies consider (or do not consider at all) the question of the “delivery” at the latest stages of the overall machine design project. Most of the machine design projects are nowadays highly time-dependent, volatile and uncertain. Due to the nature of the design process itself (Inverse iterative problem with a large number of constraints to be satisfied) a new form of “design failure” occurs : the come up with a given satisfactory design iteration that is not available within the requested delivery time intervals of the overall project.
The current article intends to present a design methodology in 8 steps that organizes the overall machine design process in a way to avoid this problem.
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Fractographic assessment of fatigue fractures may be difficult if they occur in metallic components characterized by low ductility complex microstructures. In these cases, reconciliation of known fatigue rupture mechanisms with fractographic appearance of fatigue-fractured surfaces is challenging. Special techniques assisted by theory development may be necessary. Fatigue failures in pearlitic steels, such as rail steels, are difficult to analyze and interpret, due to the metallographic microstructure that shows alternate lamellae of ductile ferrite and brittle cementite. Moreover, the task is challenging since their fracture surfaces at room temperature have ductile features, more characteristic of high temperature ruptures. In fact, a brittle to ductile Charpy-V transition curve for rail steels (≈ 0.7% C)indicates that brittle rupture predominates at the lower shelf, which extends up to 40°C ca. Fully ductile upper shelf fracture is reached only at 220°C. Features of their fatigue surfaces are clearly not brittle, but rather ductile, although not fully ductile. Thus, striations, that usually characterize ductile fatigue failures, are not clearly visible because they cannot appear on the brittle carbides, but only on the ductile ferrite lamellae. The examined fatigue fracture surfaces show striations on top of broken, previously necked, ferrite lamellae only at very high magnification.
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Statistical fractography is a new engineering technique, halfway between data science and failure analysis, that extracts mechanics data encrypted in the fracture surfaces from the statistical analysis of their roughness. Like standard fractographic tools, it provides the failure history (crack direction and initiation, failure mode…) and thus assists traditional expertise. More remarkably, it also measures previously inaccessible data, like (i) the applied mechanical load at failure (stress at initiation, quasi-static and fatigue load amplitude…) as well as (ii) the in-service mechanical properties of the failed material (toughness, failure strength, fatigue resistance…). This information, complementary to the classical metallurgic analysis, are precious to determine the failure root causes, but also for redesigning the failed part. As a result, the technique has now been used for a few years in Europe for determining the root causes of critical in-service failure in the aeronautics, train, automotive and energy sector.
In this presentation, I will show, through use cases, how statistical fractography changes the scope of failure analysis by providing not only the root causes of failure events with unprecedented details but also key information that make failure a keystone for corrective action, (re)design and development of new and more reliable products.
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The U. S. National Transportation Safety Board has investigated accidents involving fatigue fractures that initiated at subsurface anomalies including (1) a fatigue fracture that initiated from a ceramic inclusion in a turbocharger turbine wheel from a Piper PA-46-350P airplane which contributed to a forced landing, (2) a fatigue fracture of a railcar axle that initiated from a casting void that resulted in a derailment and crude oil explosion, and (3) a fatigue fracture of a high-pressure turbine stage 2 disk on a Boeing 767-300 airplane that initiated from a discrete dirty white spot and resulted in an uncontained engine failure, engine fire, and aborted takeoff. Processes used by the NTSB Materials Laboratory to analyze the fracture mechanisms and characterize the initiating defects will be discussed.
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