Crack Forge 2007 Crack |VERIFIED|
Go beyond the iconic crack to learn how this State House bell was transformed into an extraordinary symbol. Abolitionists, women's suffrage advocates and Civil Rights leaders took inspiration from the inscription on this bell. Plan your visit to the Liberty Bell Center to allow time to view the exhibits, see the film, and gaze upon the famous cracked bell. No tickets are required and hours vary seasonally.
Crack Forge 2007 Crack
From Signal to Symbol The State House bell, now known as the Liberty Bell, rang in the tower of the Pennsylvania State House. Today, we call that building Independence Hall. Speaker of the Pennsylvania Assembly Isaac Norris first ordered a bell for the bell tower in 1751 from the Whitechapel Foundry in London. That bell cracked on the first test ring. Local metalworkers John Pass and John Stow melted down that bell and cast a new one right here in Philadelphia. It's this bell that would ring to call lawmakers to their meetings and the townspeople together to hear the reading of the news. Benjamin Franklin wrote to Catherine Ray in 1755, "Adieu, the Bell rings, and I must go among the Grave ones and talk Politicks." It's not until the 1830s that the old State House bell would begin to take on significance as a symbol of liberty.
The Crack No one recorded when or why the Liberty Bell first cracked, but the most likely explanation is that a narrow split developed in the early 1840s after nearly 90 years of hard use. In 1846, when the city decided to repair the bell prior to George Washington's birthday holiday (February 23), metal workers widened the thin crack to prevent its farther spread and restore the tone of the bell using a technique called "stop drilling". The wide "crack" in the Liberty Bell is actually the repair job! Look carefully and you'll see over 40 drill bit marks in that wide "crack". But, the repair was not successful. The Public Ledger newspaper reported that the repair failed when another fissure developed. This second crack, running from the abbreviation for "Philadelphia" up through the word "Liberty", silenced the bell forever. No one living today has heard the bell ring freely with its clapper, but computer modeling provides some clues into the sound of the Liberty Bell.
Leaded brass is the material that is primarily used to manufacture gas valves, the production process of which is rather complicated (consisting of casting, followed by extrusion, hot forging, cold drawing, and finally, machining). The deformation behaviour of leaded brasses has been investigated by several research teams, e.g., Suárez et al.  analysed the deformation behaviour of a Cu40Zn2Pb brass at high temperatures; Zhu et al.  optimized the processing conditions via analysis of processing maps for a Cu25Zn brass; and Mapelli et al.  documented the relationships between the textures and morphologies of the present phases and the mechanical properties within a hot-extruded Cu39Zn2.6Pb biphasic brass. Nevertheless, the complicated production process, consisting of multiple steps, can lead to the introduction of undesirable structural defects, which can eventually result in failure (i.e., occurrence of cracking) and decreased longevity of the final product. For example, casting can impart pores, cavities, surface defects, and segregations; extrusion and cold drawing can induce tearing or chevron cracking; hot forging can lead to hot forging laps or flash cracking; and last, but not least, machining can result in lathe jaw marks or thin surface deflection steps . Studies focusing on the elimination of the risk of crack formation during processing of brasses have been published. The Pb content has been found to affect chip formation during machining, as lead forms islands of precipitates at the interfaces of both the alpha and beta phases . Heat treatment at 775 C for 60 min was shown to improve the fracture toughness of lead-free brasses . Other studies used heat treatment to optimize the structure parameters, in order to favourably affect the morphology of the grains and the final properties of a 60/40 brass , and investigated the relationship between the processing technology of a leaded brass and its final mechanical properties and structures .
Numerical model of the investigated brass fitting (a); real cut through the brass fitting, with the location of cracking marked (b); lamella of the cracked region (before final milling), acquired using FIB (c).
The structure study was supplemented with measurements of Vickers microhardness (in HV, Zwick/Roell testing machine, Zwick Roell CZ s.r.o., Brno, Czech Republic) along the cracked surface and in the vicinity of the cracked area, as well as in the die-forged material exhibiting no failure (the internal area and surface area of the fitting exhibiting no defects). The loading time for the measurements was 10 s, and the load for each indent was 200 gf. To analyse the microhardness in the internal and surface areas with no failures, 10 indents were randomly executed in particular locations of the brass component, the average values of which were subsequently calculated.
Plastic flow along the axial longitudinal cut through the brass fitting acquired via numerical simulation (a); detailed OM view of plastic flow in the vicinity of the crack within the real component (b).
Figure 3a depicts the numerically predicted stress distribution in the location in which the crack occurred on the axial longitudinal cut through the fitting during hot forging. The prevailing stress in the cylindrical part of the fitting was of a compressive character. However, the part of the fitting featuring complex geometry exhibited the majority of the tensile stress, the value of which generally increased towards the shaped areas of the brass component. Nevertheless, certain locations on the fitting featured local stress inhomogeneities and combinations of compressive and tensile stresses, as can be seen in the circle in Figure 3a.
OM did not reveal any essential information about structural anomalies; in other words, no evident differences in the grain sizes were detected. The primary hypothesis was thus that the cracking occurred due to local changes in the phase composition or chemical composition. Therefore, SEM-EBSD was further applied in order to acquire detailed information about the present phases in the cracked location of the fitting.
Figure 4b shows an SEM-EBSD scan depicting the phases present in the cracked area of the fitting; the FCC (face-centred cubic) alpha phase is depicted in red, whereas the BCC (body-centred cubic) beta phase is depicted in yellow. The figure clearly shows that the surface of the fitting, as well as the entire cracked area, were depleted of the beta phase, as only the alpha phase was detected at the surface of the die-forged component.
The structure analyses performed via SEM showed differences in the phase composition (see Figure 4b). Nevertheless, they did not reveal detailed information about the presence of possible precipitates or intermetallic phases in the vicinity of the crack. For this purpose, we prepared a lamella via FIB (see Figure 1c for the lamella and Figure 4b for the location from which the lamella was collected) and applied TEM. Firstly, we used TEM-EDS mapping to characterize the overall presence and distribution of the individual elements in the vicinity of the crack. The scanned area is depicted in Figure 5a, and the corresponding EDS maps for the individual elements are depicted in Figure 5b. As can be seen from the maps, the area surrounding the crack consisted mostly of Cu, with additional Zn and Pb, as expected. The area of the crack then exhibited negligible Cu content, but increased concentrations of Zn, Pb, O, C and, locally, Fe. Subsequent investigations were focused on detailed examinations of the locations (particles) of interest.
Before forging, the brass semi-product was heated via induction. Based on the conclusions of published studies documenting the importance of having optimized the parameters of induction heating before the actual heating preceding the plastic deformation , we performed numerical simulations, with the focus on prediction of the selected parameters, in order to evaluate the suitability of the designed production process. The predicted stress distribution revealed that the die-forged brass did not exhibit any significant local peaks of either tensile or compressive stress values. On the other hand, the stress distribution exhibited local inhomogeneities, one of which was evident in the location of the crack. The stress inhomogeneity, as well as the inhomogeneity of the imposed energy, can be primarily attributed to the geometry of the forging die.
Now, in 1976, my grandfather stood crying in our American house. I did not understand his tears. Was he homesick, longing for his town in Russia? Maybe he could not tolerate Chicago any longer with its dirty, cracked sidewalks and its ugly, scar-faced criminals.
a password recovery file could be hazardous to the future of keepass. I'd personally be careful with that, and instead have him send you the data file, and you personally get his password for him, as you have a company, an identity, and are liable, and more than likely trustworthy. a keepass cracker is a bad idea.
It would not be very difficult to develop a program for the purpose of cracking the KeePass master password, even if you're a not-very-talented C++ programmer. Such a program could unlock a database protected by a weak master password and a known keyfile, but would be ineffective against a strong master password or an unknown keyfile.
Note that the database security in KeePass (and any other good encryption scheme) lies completely in the key (password and/or key file). As Bill said already, if you got a weak master password, a recovery software could crack your database. But if the master password is strong or the key file is unknown to the attacker, there's no chance for any recovery.