Investment Casting Core
Investment Casting Core : Moore Global Investments.
Investment Casting Core
- Investment casting is an industrial process based on and also called lost-wax casting, one of the oldest known metal-forming techniques.
- (investment cast) a cast made of a material that will withstand high temperature without disintegration—compREFRACTORY CAST
- A technique for making small, accurate castings in refractory alloys using a mold formed around a pattern of wax or similar material which is then removed by melting
- (investment cast) Clubs made from a mold.
investment casting
- The part of something that is central to its existence or character
- a small group of indispensable persons or things; “five periodicals make up the core of their publishing program”
- remove the core or center from; “core an apple”
- The tough central part of various fruits, containing the seeds
- The central or most important part of something, in particular
- the center of an object; “the ball has a titanium core”
core
Civil Engineering, October 1998
By applying modem testing and rehabilitation techniques to a structure more than 160 years old, engineers have ensured the historic Canton Viaduct’s place in the high-speed rail service of the future.
Custom-designed scaffolding over the Neponset River allowed workers to repair masonry and replace cast-in-place arches without closing the railway on the Canton Viaduct.
The Canton Viaduct in Canton, Mass., built in 1835 and in continuous service ever since, is the second-oldest multiple-arch masonry viaduct in the country. Serious deterioration had slowed the movement of trains over the viaduct and threatened the viability of the historic structure. A fast-track restoration that included arch replacements and a new, independent superstructure has helped save it from further deterioration and ensure its place along Amtrak’s upcoming high-speed rail line through the Northeast.
The Canton Viaduct carries more than 50 trains daily, including Amtrak’s Northeast Corridor trains, Massachusetts Bay Transportation Authority (MBTA) commuter service and occasional Conrail freight trains. Located on the main line between Boston and New York, the bridge was built in the 19th century by the Boston & Providence Railroad and in 1984 was placed on the National Register of Historic Places. Although the structure was serviceable, there were a number of physical limitations. These included substandard horizontal clearances between the two tracks that forced severe speed restrictions; inadequate ballast shoulders to contain the thermal effects from continuous welded rail; and an inability to accommodate the high-speed rail tracks. In addition, there were cracked granite blocks, deteriorated masonry joints and badly spalled concrete spandrel arches.
VIADUCT HISTORY
When constructed in 1834-35, the viaduct was the last link in the railroad from Boston to Providence, R.I. It spanned the Neponset River valley, one of the largest geologic depressions traversed by a railroad at that time. For this major undertaking, the railroad hired Captain William Gibbs McNeill as chief engineer and Major George Washington Whistler, both noted engineers and West Point graduates. Constructed entirely of locally quarried granite, the viaduct was built with one track and carried significantly lighter railroad equipment than today.
Increased traffic caused the railroad to double the track in 1860. The railroad installed transverse wood floor beams that supported a continuous wood fence at the face of the deck. This assembly retained the ballast on the structure. In 1880, steel beams and a heavy steel railing replaced the wood floor and rail systems.
In 1910, cracks appeared in the masonry spandrel arches. Workers cast secondary concrete arches just below the masonry arches. In 1952, a second roadway arch was cut into the structure. There is evidence of various masonry repairs over the years, but it appears that detailed inspections were conducted only in 1912 and 1980.
Although MBTA owns the Canton Viaduct, Amtrak has operating rights for its Northeast Corridor service (Boston-New York-Washington) and is making capital investments to implement new, high-speed rail service between Washington and Boston. This system includes an overhead catenary along the right-of-way. Amtrak is paying SO% of the cost for the $10 million Canton Viaduct Rehabilitation Project.
STRUCTURE DESCRIPTION
The viaduct is 188 m long and follows a 1 deg. curve. It is 6.7 m wide and the deck is approximately 18 m above the Neponset River. There are 21 spandrel arches, which spring from solid granite masonry piers spaced 8.4 m on center. A unique aspect of the viaduct is that the space between the piers contains longitudinal granite walls. Two parallel, 1.5 m thick walls separated by a 1.2 m wide chamber fill the space between the piers.
Where the viaduct spans the river, six smaller arches penetrate the longitudinal walls and allow the river to flow beneath. There are also two roadway arches: one that was part of the original construction and one added in 1952. The viaduct deck is ballasted to support two railroad tracks.
Three key project objectives of the design and construction of the track upgrade were strengthening and widening the structure for future high-speed rail service; restoring and preserving the historic fabric of the structure; and facilitating fast-track construction without hampering railroad operations.
The rehabilitation design focused on supporting an accelerated construction schedule while working adjacent to high-density railroad operations. Only one track could be taken out of service at a time, and the second track could be worked on only from 2 a.m. to 5 a.m. Both tracks had to be operational within 17 months.
To widen the structure for high-speed rail service, the distance between the two sets of tracks ("track center") was increased from 3.6 m, which was less than current railroad stand
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