Bond Strength Characteristic of Concrete Patch Repair Material Made from Unsaturated Polyester Resin (UPR)-Mortar

Patch repair materials made from unsaturated polyester resin (UPR)-mortar have been investigated to determine their bond strength characteristic by slant shear test method. The relative mechanical properties of UPR-mortar and substrate concrete for composing the specimens are: lower modular and high strength ratio. The experimental results show that the combination of materials causes the observed bond strength are dictated by failure of substrate concrete. The actual bond strength could be higher as most of the specimens fail without separation of the UPR-mortar and substrate concrete at the bond plane.

A Scientific Approach to the Process Development of Bonded Attachments for High Speed Rotor Application

The quest for increased work per stage of compression to reduce overall gas turbine engine system cost has placed extreme demands on the high-pressure turbine (HPT) system. As an example, the HPT is required to operate at unprecedented levels of AN2 (the product of turbine annulus area and mechanical speed squared) to enable compressor performance goals to be met. The typical approach of mechanically attaching blades via firtree or dovetail configured mechanical attachments, limits rotor speed because of the life limiting broach slots (stress concentrators) in the disk rim. Exacerbating this problem is the fact that the disk lugs, which react the blade loading, impose a dead load. Higher disk speed results in higher blade loading requiring a deeper or wider lug to support the blade. This in turn results in a wider disk bore to support the deeper, dead load lug region. The dilemma is that higher speed results in larger stress concentrations at the rim and a wider disk bore to support the added parasitic rim load. The answer to this dilemma lies in creating an Integrally Bladed Rotor (IBR) in which the blades are integral with the disk. Since typically, for an HPT, the blades are single crystal and the disk equiaxed nickel alloys, the IBR design suggested precludes absolute machining as the fabrication approach. A solution lies in metallurgically bonding the blades to the disk rim. Bonded airfoil attachments have the potential to increase AN2 and component life by 9–10% by eliminating broach induced stress concentrations as noted. Moreover, bonded attachments can reduce external rim loading by upward of 15% with a corresponding reduction in disk weight. The key to the solution is a controlled, economical process to concurrently join a full complement of HPT blades in a repeatable manner. This paper discusses how a scientific approach and creative design practice can lead to such a process. Three alternative tooling concepts, and one universal tool that allows independent use of two of these concepts, were developed. Tool stresses and deflections, tool load paths, and bond pressure profiles were all quantified through ANSYS Finite Element Analyses and closed form analytical solutions. Prior experience has shown that joint strength is sensitive to the bond pressure level. Therefore, the tool materials and geometry were iterated upon until the pressure applied to the blade bond plane was as uniform as possible. Since absolute uniformity is elusive when deformable bodies are part of the bond load train, accurately determining the maximum and minimum bond plane pressure is absolutely essential for subsequent joint characterization and design allowable determination. This allows localized working stresses in the designed attachment to be compared to specific, bond pressure driven, allowable strengths rather than an average strength. This paper will show how applying a scientific approach to the development of a critical technology process can reduce both the cost and risk of process development.

A Scientific Approach to the Process Development Bonded Attachments for High-Speed Rotor Application

The quest for increased work per stage of compression to reduce overall gas turbine engine system cost has placed extreme demands on the high-pressure turbine (HPT) system. As an example, the HPT is required to operate at unprecedented levels of AN2 (the product of turbine annulus area and mechanical speed squared) to enable compressor performance goals to be met. The typical approach of mechanically attaching blades via firtree or dovetail configured mechanical attachments, limits rotor speed because of the life limiting broach slots (stress concentrators) in the disk rim. Exacerbating this problem is the fact that the disk lugs, which react the blade loading, impose a dead load. Higher disk speed results in higher blade loading requiring a deeper or wider lug to support the blade. This in turn results in a wider disk bore to support the deeper, dead load lug region. The dilemma is that higher speed results in larger stress concentrations at the rim and a wider disk bore to support the added parasitic rim load. The answer to this dilemma lies in creating an integrally bladed rotor (IBR) in which the blades are integral with the disk. Since typically, for an HPT, the blades are single crystal and the disk equiaxed nickel alloys, the IBR design suggested precludes absolute machining as the fabrication approach. A solution lies in metallurgically bonding the blades to the disk rim. Bonded airfoil attachments have the potential to increase AN2 and component life by 9–10 percent by eliminating broach induced stress concentrations as noted. Moreover, bonded attachments can reduce external rim loading by upward of 15 percent with a corresponding reduction in disk weight. The key to the solution is a controlled, economical process to concurrently join a full complement of HPT blades in a repeatable manner. This paper discusses how a scientific approach and creative design practice can lead to such a process. Three alternative tooling concepts, and one universal tool that allows independent use of two of these concepts, were developed. Tool stresses and deflections, tool load paths, and bond pressure profiles were all quantified through ANSYS finite element analyses and closed-form analytical solutions. Prior experience has shown that joint strength is sensitive to the bond pressure level. Therefore, the tool materials and geometry were iterated upon until the pressure applied to the blade bond plane was as uniform as possible. Since absolute uniformity is elusive when deformable bodies are part of the bond load train, accurately determining the maximum and minimum bond plane pressure is absolutely essential for subsequent joint characterization and design allowable determination. This allows localized working stresses in the designed attachment to be compared to specific, bond pressure driven, allowable strengths rather than an average strength. This paper will show how applying a scientific approach to the development of a critical technology process can reduce both the cost and risk of process development.

NMR spectra (29Si and 13C) of trimethylsilylated cyclic acyloins and ketones

13C and 29Si NMR chemical shifts are reported for several 1-trimethylsiloxycycloalkenes and 1,2-bis(trimethylsiloxy)cycloalkenes, (CH3)3SiO)xCnH2n-2-x (x = 1,2), dissolved in hexadeuterioacetone. Several correlations of the chemical shifts with structural parameters (ring size, interatomic distances etc.) are noted and an attempt is made to explain the found strong dependence of the 29Si chemical shifts on the ring size. Steric crowding with the nearest CH2 group drives the trimethylsilyl group out of the double bond plane and thus causes steric inhibition of the resonance of unshered oxygen electron pairs with electrons of the double bond. Since the crowding becomes more accute with increasing ring size, the ring size is in this way projected into the chemical shifts of silicon and olefinic carbons. This mechanism provides a united interpretation of all observed NMR chemical shifts.