Transactions of the Canadian Society for Mechanical Engineering
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Volume 39 (2015), Issue 1
Influences of train speed and axle loads on life cycle of rail fastening clips
Javad Sadeghi, Mohammad Fesharaki, Amin Khajehdezfuly
Railway fastening clips play an important role in the stability and safety of railway track systems. There are various studies conducted on fastening clip failure mechanism. Although the majority of these studies indicate that fatigue is the main cause of clip failure, little attentions has been paid to parameters influencing clip fatigue characteristics. In response to this need, a new testing machine was developed by which the structural and loading conditions of fastening clips are simulated in a laboratory. Clip permanent deformations were measured for various track operational conditions, and consequently correlations were developed between clip plastic defamations and track axle loads as well as train speeds. The results obtained pave the way of determining the required clip maintenance cycles for various track loading conditions.
Geometric constraints and interference-proof conditions of helix-curve meshing-wheel mechanism
Yangzhi Chen, Jiang Ding, Yueling Lv
In some recent publications, a gear mechanism named Space-Curve Meshing-Wheel (SCMW) has been proposed by the present authors. This paper presents the geometry of the Helix-Curve Meshing-Wheel (HCMW), the most common SCMW at present. The driven contact curve equation is optimized by removing a redundant length parameter. Then, both geometric constraints and interference-proof conditions are calculated in the following three aspects: contact curves, HCMW pair and HCMW train. A parameter selection of a novel reducer with HCMW trains is shown as a practical example. The theories in this paper are mainly applied to determine the feasibility range of the geometric parameters within the HCMW, and provide foundation to its industrial standardized production.
Modified electrically heated hot water storage tank: experimental investigation
Hot water in residential buildings accounts for 37% of the energy used. In hot water storage tanks (HWST) the average water temperature decreases due to turbulent mixing. A modified design of HWSTs to extend hot water availability is proposed and tested. For this purpose two electrically heated 50 litre commercial tanks were obtained. One was equipped with a semidome to inhibit turbulent mixing. The unmodified was used for comparison. These were tested for three flow rates: 6, 8, and 10 L/min. Higher flow rates of hot water temperatures were obtained from the modified tank. To increase the heating transfer rate fins were added to the electrical heater. Water supply temperature of (60°C) was achieved 12 minutes earlier in the modified tank due to extended heat transfer area.
Stiffness and dynamic analysis of a planar class-2 tensegrity mechanism
Zhifei Ji, Tuanjie Li, Min Lin
Tensegrity mechanisms have several attractive characteristics such as light-weight, deployable and easily modeled. In this paper, the stiffness and dynamics of a planar class-2 tensegrity mechanism are studied. Firstly, the solutions to the kinematic problems are found by using a method of reduced coordinates. Then, the stiffness of the mechanism is investigated on the basis of a stiffness matrix. The mechanismís stiffnesses along directions defined nodal coordinates are computed. Finally, a dynamic model is derived and the motions of the mechanism are simulated.
A theoretical and experimental study for the load optimization of gear-like profiles by using forward and lateral extrusion
Tahir Altinbalik, Önder Ayer
The main purpose of this research is to investigate the minimum deformation load by selecting a suitable forming method for manufacturing of gear-like sections and to compare the load estimation methods between Upper Bound Analysis and DEFORM-3D. Forward and lateral extrusion were chosen as two different forming methods. The effect of die transition geometry on deformation load was also investigated by straight tapered and cosine profiles. A newly kinematical admissible velocity field to analyze different profiles of extrusion dies was proposed by upper bound analysis. Al 1070 was used as working material. Experiments using five sets of dies with gear-like form were performed, and the measured forming load results were compared with the predictions of the theoretical solutions. Experiments were carried out on the 150 metric ton hydraulic press.
Extended nonlinear analytical models of compliant parallelogram mechanisms: third-order models
This paper proposes extended nonlinear analytical models, third-order models, of compliant parallelogram mechanisms. These models are capable of capturing the accurate effects from the very large axial force within the transverse motion range of 10% of the beam length through incorporating the terms associated with the high-order (up to third-order) axial force. A case study of the compound compliant parallelogram mechanism, composed of two basic compliant parallelogram mechanisms in symmetry, is also implemented. It is shown that in the case study the slenderness ratio affects the result discrepancy between the third-order model and the first-order model significantly, and the third-order model can illustrate a non-monotonic transverse stiffness curve if the beam is thin enough.
Manufacturing tolerance design based on fuzzy binary approach
J. John Martin, K.P. Padmanaban, K. Thiagarajan
In this paper, the concept of binary, fuzzy systems has been applied. These concepts optimize tolerance as a percentage through the fuzzy approach (based on binary values 0 and 1). Finally, the tolerance fit into six different levels along with optimized cost has been characterized, namely, best fit with minimum cost, better fit with minimum cost, good fit with minimum cost, acceptable range for minimum required fit with minimum cost, non acceptable range, and worst fit range.
Vibration modeling of parallel kinematic mechanisms (PKMs) with flexible links: Admissible shape functions
Masih Mahmoodi, James K. Mills, Beno Benhabib
The accuracy of various admissible shape functions, for vibration modeling of flexible links of Parallel Kinematic Mechanisms (PKMs), is investigated as a function of the ratio of the mass of the moving platform to the mass of the link. Knowing that the commonly used shape functions based on "pinned", "fixed", or "free" boundary conditions do not incorporate the moving platform mass, "pinned-mass" and "fixed-mass" shape functions are presented herein, and are compared with finite-element based results for various mass ratios. The closest shape functions to the finite-element results are, then, utilized and compared with other shape functions in the subsequent vibration modeling to predict the tooltip response.
Suction inlet vortex investigation at low Reynolds numbers
Wei Hua Ho, Omar Faruq bin Idris, Tze How New
Under certain flow conditions, when an inlet is aspirated in close proximity to a solid boundary, a vortex will form between the surface and the inlet. The formation and ingestion of such vortices could potentially lead to inefficient fluid suction by pumps or catastrophic damages in high-speed jet engines. Previous studies established the basic relationship of such inlet vortices formation threshold and geometry and flow conditions, though they were typically considered at significantly high Reynolds numbers. It remains unclear if there is a lower limit to the Reynolds number at which this phenomenon ceases to exist. This study shows that this phenomenon exists even at low Reynolds number of Re = 160. In particular, the results are generally in agreement with the previously established relationships at much higher Reynolds numbers but certain correlations are not as significant. This suggests that formation of inlet vortices may be less sensitive to Reynolds numbers effects than previously thought.
Improving industrial energy efficiency through the implementation of waste heat recovery systems
Kristine O'Rielly, Jack Jeswiet
Improving the energy efficiency of industrial processes and the facilities in which they are carried out is often considered to be one of the most promising ways to begin reducing global greenhouse gas emissions. One of the best ways for organizations to reduce their energy consumption without having to carry out extensive equipment and facility overhauls is waste heat recovery or energy recycling. Waste heat recovery involves tapping into previously discarded thermal energy streams and reusing it for various purposes within a facility (space heating or cooling) or within the process itself (pre-heating air and boiler makeup water). Despite the numerous social and economic benefits that are available through waste heat recovery, several economic and technical barriers still exist to its wide-scale implementation. This paper provides an overview of the current state of waste heat recovery systems available in industry, offers a discussion of the major barriers to their wide-spread implementation, and lastly concludes with new data with several new case studies from Canadian manufacturers which have successfully harnessed waste heat within their facilities.
Full journal title: Transactions of the Canadian Society for Mechanical Engineering
Abreviated journal title: Trans. Can. Soc. Mech. Eng.
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