Tie bars

An alloy tie bar in a chemical plant has been designed to withstand a stress, ct, of 25 MN m at 620°C. Creep tests carried out on specimens of the alloy under... 

Find the depth of metal lost from the surface of a mild steel tie bar in a furnace at 500°C after 1 year. You may assume that the oxide scale is predominantly FeO. The atomic weight and density of iron are 55.9 kg kmoL and 7.87Mgm" the atomic weight of oxygen is 16 kg kmol F What would be the loss at 600°C ... 

Slides Pitting corrosion on a marine turbine blade [4] corroded tie bars, etc., in furnaces, heat exchangers, etc. oxidised cermets. 

Figure 10-20D. RODbaffle layout details. Key elements are support rods, circumferential baffle rings, cross-support strips, and longitudinal tie bars. Four different RODbaffle configurations are used to form a set baffles W, X, Y, and Z. (Used by permission Phillips Petroleum Company, Licensing Div., Bui. 1114-94-A-01.)...

As Colin Russell has noted in his History of Valency (1971), a straight line is a much "more tangible symbol,. . . like rods, tie-bars, and so on."79 With the "bond," the pictorial or structural formula had made its debut. 

Most steatite ceramics are either dry mixed and pressed, or wet-mixed, spray-dried and pressed, but they can also be wet-mixed and extruded. Typical firing temperatures lie close to 1300 °C. Many small parts are made for the electronics components industry where low dielectric losses are required, for example for tie-bars and other parts for ganged capacitors, small trimmer capacitors, high-power capacitors (see Section 5.6.3), coil formers, lead-throughs and substrates for... 

In use are retractable tiebars. Different designs are used to unlock a tie bar. Principle reason is to permit installing molds that would occupy the complete platen minus the tie rod areas. Thus the mold literally has holes. Very popular are tiebarless systems which are also used. Without the tiebars, larger molds can reduce IMM cost, mount larger molds in a smaller IMM, permit quicker to easier mold mounting, no holes in molds, simpler part handling automation, etc. 

Using an instrument (such as strain gauges) that is mounted on or at the end of tie bars to measure any pressure imbalance on the mold due to imbalance in apphed clamping pressures via the tie bars. See measurement strain gauge. 

The immediate technical cause of the collapse of Sea Gem was the breaking of tie bars. Many of the factors needed to induce brittle fracture were present, stress concentrations, weld defects, residual stresses, vibrations and low temperatures. The operational problem in December 1965 was the final trigger that caused the actual collapse. 

The report of the inquiry [111] criticised the design and fabrication of the alterations made to the original pontoon. The actual cause of the accident was the failure of some tie bars in the detail around the jacking points. The failure was due to brittle fracture which initiated from severe notches such as a small radius curve at the fillet between the spade end and the shank of the tie bar. Weld defects and fatigue cracks were also present in tie bars subsequently recovered from the sea bed. The tie bars had been flame cut to shape and had weld repairs visible to the eye. There had been no post welding heat treatment of the steel. The steel complied with the original specification but tests showed low Charpy V notch impact values. Photo elastic tests indicated a stress concentration factor of 7 at the fillet between the spade end and the shank. The fracture was initiated in the opinion of the inquiry tribunal by the low ambient temperature of around 3°C. 

One problem that most controls do not consider involves the effect of heat on tie-bars, which can directly influence mold performance, particularly at start-up. If the heat differs from top and bottom bars, it is necessary to insulate the mold from the platens. The insulator pad used also confines heat more to the mold, producing savings in heat and/or better heat control. The following paragraphs describe calculation of the elongation of these usually evenly heated bars, and of thermal mold growth (1). 

---