Linear Expansion Values Research Articles

Contact Interaction of Steam Turbine Inner Casing Elements During Plastic Deformation

A structure’s material plasticity influence on the pattern of contact interaction of its elements during operation is studied. The stress-strain state problem for the inner casing of a steam turbine high-pressure cylinder operating at supercritical steam parameters (over 240 atm and 565 °C) is solved. The problem is solved by using a finite-element software package. A model of thermoplasticity with kinematic and isotropic hardening is considered. In carrying out the study, experimental strain curves were used for the materials of the connection. The main dependencies used in solving the problem are given. The method of solving the thermal contact problem of interaction of flange connector elements in the conditions of plasticity is based on the application of a contact layer model. To be able to take into account changes in the load from the fastening in the process of combined strain of both the fastening and the casing, first proposed is a method of the three-dimensional modeling of the thermal tightening of the fastening of the horizontal casing connector by applying the linear coefficient of linear expansion of the material. The proposed approach allows modeling the stress of the initial tightening of studs by specifying a fictitious change (decrease) of the coefficient of linear expansion of a stud given as a separate body in the calculation scheme. The magnitude of the specified change in the coefficient of linear expansion is determined from the relationship between the stress of the initial tightening in the stud and the required, for its creation, elongation, which is implemented in the calculation scheme in the presence of different values of linear expansion of both the stud and the casing. To conduct the numerical experiment, an ordered finite-element grid of the casing design was constructed. A 20-node finite element was used in the construction of the casing grid and the fastening. The effect of force loads and the temperature field, in which the structural element under consideration is operated, is taken into account. An analysis of the results of distribution of equivalent stresses and contact pressure during operation is carried out. The difference between the obtained results and the results of solving the problem in the elastic formulation is noted.

Aluminum-laminated Panels: Physical and Mechanical Properties

Aluminum lamination was performed to improve the physical and mechanical properties of several wood-based composite panels. The panels were aluminum-laminated on two faces in a hot press at 689 kPa and 120 °C for 6 min. Four types of wood-based composites were used as cores, and aluminum 3003 alloy sheets were used for face laminations. Polyurethane adhesive ensured bonding strength between the wood-based composite and the aluminum sheets. The objective was to assess sandwich composite panels made of wood-based composites as a core layer with aluminum-laminated faces. This study evaluated the physical and mechanical properties of these panels. The results show that aluminum-laminated panels had higher dimensional stability (thickness swelling and linear expansion values). Bending properties such as the apparent modulus of elasticity (Eapp) and the modulus of rupture (MOR) were significantly increased with face-lamination. Medium-density fiberboard (MDF) laminate presented an increase of 554% for Eapp and 570% for MOR in comparison with non-laminated MDF panels. The shear edgewise strength for oriented strand board and plywood increased by 44% and 77%, respectively. The results confirm that aluminum-laminated panels have the potential to be used as structural panels in future applications.

各種配向性ファイバーボードをコアにしたサンドイッチパネルの寸法安定性能の解析的研究

The observed values of dimensional stabilities(thickness swelling (TS) or linear expansion (LE)) for sandwich panels with veneer or paper as the faces and various oriented fiberboards as the core were compared with the values calculated by the properties of veneer, paper or various oriented fiberboards. As a result, observed TS or LE values agreed basically well with calculated ones , however, it was important for calculated value of higher precision to consider the effect of adhesive properties between face and core. Dimensional stabilities of sandwich panel could be estimated by the properties of face and core materials of composites. If face material had high Young's modulus and great dimensional stabilities like the veneer in fiber direction with the poor dimensional stabilities of core material, sandwich panel would have great dimensional stabilities.

The influence of wax-sizing on dimension stability and mechanical properties of bagasse particleboard

Bagasse particleboards (BPBs) were made using polymeric methylene diphenyl diisocyanate (pMDI) resin as binder and wax emulsion as dimension stabilizer. A factorial experiment was conducted to measure the effects of wax and pMDI resin content on particleboard dimension stability and mechanical properties. The data were compared with respective properties specified in the ANSI A208.1 standard for commercial M3 grade wood-based particleboard. Wax-sizing improved the linear expansion (LE) of the particleboards under both pMDI resin contents used in this research and all LE values were controlled under the critical value of 0.35%. The use of wax significantly reduced 24-h water absorption and thickness swelling compared to the control panels without wax. Wax-sizing at the moderate levels also showed positive influence on long-term water absorption and thickness swelling properties. Wax content levels, however, did not significantly influence water absorption and thickness swelling behavior. Wax-sizing had no evident negative effects on the bending properties of MDI-bonded bagasse particleboards under both resin contents, while it caused slightly negative effect on internal bond strength. Mechanical properties of all boards far exceeded the minimum values specified in ANSI A208.1 standard. The entire properties of the 5% pMDI BPBs were better than those of the 3% pMDI panels as expected.

Spinellisation Study of Three Different MgO-Al2O3 Compositions Using a Dilatometer

Three different MgO-Al2O3 spinel compositions having MgO: Al2O3 molar ratios 2: 1, 1: 1 and 1: 2 have been studied. Isostatically pressed green compacts of oxide mixtures were used for the dilatometric study and a maximum temperature of 1400°C was used. Dilatometric study reveals that the formation of spinel starts above 1000°C for all the compositions and the linear expansion values are in good agreement with their expected values considering theoretically possible (maximum) spinel content. The fall in expansion values was also observed at and above 1350°C due to greater shrinkage rate (from sintering) than the rate of expansion from spinellisation. The phase analyses of the final products showed spinel as the major phase with some free oxides due to incomplete spinellisation reaction.

木質材料 パーティクルボードの寸法安定性に及ぼす製造因子の影響

The object of this study was to investigate the dimensional stability (DS) for particleboards (PBs) made by changing factors of board preparation, this is, density of boards, resin content, adhesives, particle size and wood species. The measurement of moisture absorption, in-plane linear expansion (LE) and thickness swelling (TS) were done to evaluate DS of PBs.The results are summarized as follows: It was clear that the values of LE and TS were decreased with decreasing density of boards and increasing resin content. DS of adhesives used was superior in order of phenolic resin (PF)>Isocyanate resin (IC)>Urea resin (UF). The oriented boards prepared from birch and Hinoki showed excellent resistance against moisture absorption, and anti-swelling efficiency on their LE values (L-ASE) in 50% and 35%, respectively.