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Fatigue analysis of Package Terminal Air Conditioner motor bracket under dynamic loading

materials & DESIGN 2009年第8期30卷 3206-3216页

作者： Loh, S. K. Chin, W. M. Faris, Waleed F. IIUM Dept Mech Coll Engn Kuala Lumpur 53100 Malaysia

Motor bracket has been designed as a framework to support motor and fan in air conditioning products. Vibration and fatigue of motor bracket has been continuously a concern which may lead to structural failure if the resulting vibration and stresses are severe and excessive. It is a significant study which requires in-depth investigation to understand the structural characteristics and its dynamic behavior. This paper presents and focuses on some Finite Element (FE) analyses performed such as frequency analysis to determine the structural response due to harmonic excitation over a frequency range. The resonant frequency can be predicted based on the responses in frequency domain. Besides that, the static and dynamic vibration analyses give the maximum structural stress condition under static loading and dynamic condition. The predicted maximum stresses are compared with inherent material yield strength. The plastic deformation is not covered in the study as only elastic property is defined. A fatigue failure prediction of the current P-TAC motor bracket using FE simulation and fatigue failure criteria approach has also been studied. The dynamic stress curve giving mean stress and alternating stress has been applied in the established fatigue failure criteria such as Yield Criteria and Fracture Criteria to predict the possibility of fatigue occurrence. This approach is considered a conservative prediction approach to prevent structural fatigue which is best suited and safe for certain design applications. In the effort to strengthen the motor bracket, different modifications of the motor bracket geometry have been investigated and the comparison of results of each analysis is presented. The rib support, edge radius and thickness have been modified and added to examine the effect to the overall static and dynamic behavior. It is found that the rib-support addition and the increase of edge radius can effectively improve the structural performance based on the analyses

关键词： STRUCTURAL failures BRACKETS materials -- Fatigue AIR conditioning materials -- dynamic testing STRAINS & stresses (Mechanics) FINITE element method

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dynamic compressive response of intact and damaged AD995 alumina

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INTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY 2004年第3期1卷 254-260页

作者： Luo, HY Chen, WN Univ Arizona Dept Aerosp & Mech Engn Tucson AZ 85721 USA

To determine the dynamic properties under loading conditions simulating those encountered in ceramic armors subjected to impact, a novel dynamic compressive experimental technique modified from a split Hopkinson pressure bar (SHPB) was employed to load the ceramic specimen by two consecutive stress pulses. The first pulse determines the dynamic response of the intact ceramic material and then crushes the specimen. Before the specimen disintegrates, the second pulse determines the dynamic compressive constitutive behavior of the ceramic rubble that is still interlocked. The results show that the compressive strengths of damaged ceramics are insensitive to strain rates once the damage level exceeds a critical value.

关键词： ALUMINUM oxide materials -- dynamic testing CERAMICS CERAMIC materials PULSE (Heart beat) ARMOR TECHNICAL chemistry

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Mixed-mode failure of graphite/epoxy composites

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JOURNAL OF ENGINEERING materials AND TECHNOLOGY-TRANSACTIONS OF THE ASME 2001年第3期123卷 371-376页

作者： Seif, MA Shahjahan, M No Illinois Univ Dept Mech Engn De Kalb IL 60115 USA

An experimental study of the crack displacement and failure modes of graphite epoxy-plates, having central cracks at different angle with the loading axis, was conducted. Due to this type of loading arrangement, the material was under mixed-mode loading condition (Mode I and mode II). IN this investigation, Moire Interferometry technique was employed to measure Crack Opening Displacement (COD) and Crack Shearing Displacement CSD). Detailed studies were performed to investigate the effect of the crack angle on the strength reduction ratio, the damage zone, and the critical stress intensity factors. The comparison between the Linear Elastic Fracture Mechanics (LEFM) solution and the results obtained from this investigation showed a fair agreement between the theoretical data and the experimental ones. This confirms the validity of implementing the LEF model for this type of materials.

关键词： DEFORMATIONS (Mechanics) FRACTURE mechanics materials -- dynamic testing SHEAR (Mechanics)

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Elastodynamic fracture analysis of multiple cracks by laplace finite element alternating method

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JOURNAL OF APPLIED MECHANICS-TRANSACTIONS OF THE ASME 2000年第3期67卷 606-615页

作者： Chen, WH Chang, CL Tsai, CH Natl Tsing Hua Univ Dept Power Mech Engn Hsinchu 30043 Taiwan

The Laplace finite element alternating method, which combines the Laplace transform technique and the finite element alternating method, is developed to deal with the elastodynamic analysis of a finite plate with multiple cracks. By the Laplace transform technique, the complicated elastodynamic fracture problem is first transformed into an equivalent static fracture problem in the Laplace transform domain and then solved by the finite element alternating method developed. To do this, an analytical solution by Tsai and Ma for an infinite plate with a semi-infinite crack subjected to exponentially distributed loadings on crack surfaces in the Laplace transform domain is adopted Finally, the real-time response can he computed by a numerical Laplace inversion algorithm, The technique established is applicable to the calculation of dynamic stress intensity factors of a finite plate with arbitrarily distributed edge cracks or symmetrically distributed central cracks. Only a simple finite element mesh with very limited number of regular elements is necessary. Since the solutions are independent of the size of time increment taken, the dynamic stress intensity factors at any specific instant can even be computed by a single time-step instead of step-by-step computations. The interaction among the cracks and finite geometrical boundaries on the dynamic stress intensity factors is also discussed in detail.

关键词： FINITE element method materials -- dynamic testing

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