Life Prediction of V-Belts Related to Fatigue Mechanisms

1989 ◽  
Vol 111 (3) ◽  
pp. 424-432 ◽  
Author(s):  
D. Fritzson
Keyword(s):  
Fatigue Life ◽  
Life Prediction ◽  
Development Process ◽  
Failure Modes ◽  
Theory Development ◽  
Product Development Process ◽  
Short Life ◽  
Test Conditions ◽  
Fatigue Data ◽  
Radial Cracks

Next to gear transmissions, belt transmissions are the most important mechanical transmissions. Today, belt design and development is based on extensive application tests of belts in the product development process. There is a need for theory development and design support systems. This would enable simulation for prediction and optimization of fatigue life. The aim of this work is to study certain parts of the belt in detail when the belt is running under loaded conditions. The areas of special interest are those which can be related to failure mechanisms. Thus the model can be used for calculations to predict service life. Here, the attention is focused on V-belts. Several different failure modes can be identified in V-belt fatigue. Here it is shown that the failure modes thus defined occur for such test conditions that long life can be associated with radial cracks, medium life with separation, and cord break with short life. In order to monitor the stress-strain state at any location in the belt, while simulating a running belt, “the parametric belt segment model” has been developed. Correlation with V-belt fatigue data for 11 different load cases have been made. The conclusion is that both failure mode and fatigue life can be predicted using computer simulations.

TTK Chitra tilting disc heart valve model TC2: An assessment of fatigue life and durability

2017 ◽  
Vol 231 (8) ◽  
pp. 758-765 ◽  
Author(s):  
NN Subhash ◽  
Adathala Rajeev ◽  
Sreedharan Sujesh ◽  
CV Muraleedharan
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Fatigue Life ◽  
Heart Valve ◽  
Life Prediction ◽  
Heart Valves ◽  
Failure Modes ◽  
Fatigue Life Prediction ◽  
Element Analysis ◽  
Valve Model

Average age group of heart valve replacement in India and most of the Third World countries is below 30 years. Hence, the valve for such patients need to be designed to have a service life of 50 years or more which corresponds to 2000 million cycles of operation. The purpose of this study was to assess the structural performance of the TTK Chitra tilting disc heart valve model TC2 and thereby address its durability. The TC2 model tilting disc heart valves were assessed to evaluate the risks connected with potential structural failure modes. To be more specific, the studies covered the finite element analysis–based fatigue life prediction and accelerated durability testing of the tilting disc heart valves for nine different valve sizes. First, finite element analysis–based fatigue life prediction showed that all nine valve sizes were in the infinite life region. Second, accelerated durability test showed that all nine valve sizes remained functional for 400 million cycles under experimental conditions. The study ensures the continued function of TC2 model tilting disc heart valves over duration in excess of 50 years. The results imply that the TC2 model valve designs are structurally safe, reliable and durable.

Folding-Reliability of Flexible Electronics in Wearable Applications

2019 ◽  
Author(s):  
Pradeep Lall ◽  
Hyesoo Jang ◽  
Ben Leever ◽  
Scott Miller
Keyword(s):  
Fatigue Life ◽  
Strain Rate ◽  
Failure Mechanism ◽  
Flexible Electronics ◽  
Experimental Analysis ◽  
Failure Modes ◽  
Failure Mechanisms ◽  
Mechanism Analysis ◽  
Accelerated Test ◽  
Test Conditions

Abstract There is a growing need for flexible hybrid electronics solutions for wearable applications, in which the user may often wear electronics on body, on fabric or on skin. Electronics in wearable application may be subjected to stresses of daily motion including bending, twisting and stretching. Thus, there is need for technologies capable of flexibility, robustness and small size while being lightweight. Existing standards for focus on rigid electronics and there is scarcity of guidance for test-levels needed to assure reliability of flexible electronics. There is need for studies focused on the development of accelerated test conditions representative of field applications and the identification of failure mechanisms for test levels. In this study, experimental analysis on fatigue life of the PCB in cyclical folding load is conducted. A folding test-stand capable of replicating the stresses of daily motion in a lab-environment has been developed for the test. For the better understanding of the failure mechanism, analysis of failure modes is carried out. Consequently, it is found that fatigue life of the PCB is related to the several conditions: folding direction, moving distance, folding diameter and strain rate.

Fatigue Life Prediction for Complex Load Versus Time Histories

1983 ◽  
Vol 105 (3) ◽  
pp. 206-214 ◽  
Author(s):  
N. E. Dowling
Keyword(s):  
Fatigue Life ◽  
Life Prediction ◽  
Fatigue Life Prediction ◽  
Constant Amplitude ◽  
Discrete Events ◽  
Complex Load ◽  
Stress Effects ◽  
Fatigue Data ◽  
Time Histories ◽  
Damage Type

Fatigue life prediction for complex load versus time histories is considered from the viewpoint of separating the history into discrete events, or cycles, which may then be used with constant amplitude fatigue data in a cumulative damage type of analysis. Highly irregular histories require special attention, with minor load excursions being considered in cycle counting as temporary interruptions of larger load cycles. Local notch plasticity and mean stress effects are interrelated, and such effects are most rationally accounted for in terms of local notch stresses and strains. The paper describes and discusses a life prediction procedure for notched members which is based on modeling of the stresses and strains occurring locally at the notch.

Fatigue Modulus Concept and Life Prediction of Thick-Section S2-Glass/Vinylester Composites Under Flexural Loading

1999 ◽  
Author(s):  
Hassan Mahfuz ◽  
Kamruz Zaman ◽  
Anwarul Haque ◽  
Uday Vaidya ◽  
Hisham Mohamed ◽  
...  
Keyword(s):  
Fatigue Life ◽  
Applied Stress ◽  
Life Prediction ◽  
Fatigue Tests ◽  
Fatigue Life Prediction ◽  
Analytical Prediction ◽  
Thick Section ◽  
Cycle Number ◽  
Material Constants ◽  
Fatigue Data

Abstract Fatigue life prediction of thick-section S2-Glass fiber reinforced Vinylester composites has been studied analytically using fatigue modulus concept. Flexural fatigue tests were conducted under three point bend configuration. A stress ratio of R = 0.1 and a frequency of 3 Hz has been used for the fatigue tests. Fatigue data have been generated at five load levels; 85%, 80%, 70%, 60% and 55% of the ultimate flexural strength. Using these fatigue data, S-N diagram has been generated. Fatigue modulus has been determined by the slope of the line drawn on a plot of applied stress vs. resultant strain at specific loading cycle. Since fatigue modulus degrades with cycle number, it was assumed that the degradation rate follows a power function of fatigue cycle. Using this concept, a practical and applicable equation for predicting fatigue life is established. The Fatigue Life Prediction method used in this investigation requires two distinct parameters, namely applied stress level and two material constants. These material constants have been determined from the fatigue test data. A comparison has been made between the analytical prediction and the experimentally obtained S-N curve. The correlation between the two has been observed to be excellent. Flexural failure modes have also been identified as extensive delamination, fiber fracture and fiber kinking. Microscopic observation shows that all failures are predominantly on the tensile side with slight fiber kinking and matrix crushing on the compression side.

Review and Consideration of Unsettled Problems on Evaluation of Fatigue Damage in LWR Water

2006 ◽  
Vol 129 (1) ◽  
pp. 186-194
Author(s):  
Makoto Higuchi ◽  
Katsumi Sakaguchi
Keyword(s):  
Fatigue Life ◽  
Mechanical Test ◽  
Low Alloy Steels ◽  
Test Results ◽  
Considerable Effort ◽  
Test Conditions ◽  
Fatigue Data ◽  
Alloy Steels ◽  
Fatigue Life Reduction ◽  
Year 2000

Reduction in the fatigue life of structural materials of nuclear components in Light Water Reactor (LWR) water was initially detected and examined by the authors in the 1980s, who subsequently directed considerable effort to the development of a method for evaluating this reduction quantitatively. Since the first proposal of equations to calculate environmental fatigue life reduction for carbon and low-alloy steels was published in 1985 by Higuchi and Sakamoto (J. Iron Steel Inst. Jpn. 71, pp. 101–107), many revisions were made based on a lot of additional fatigue data in various environmental and mechanical test conditions. The latest models for evaluation using Fen of the environmental fatigue life correction factor were proposed for carbon and low alloy steels in the year 2000 and for austenitic stainless steel, in 2002. Fen depends on some essential variables such as material, strain rate, temperature, dissolved oxygen and sulfur concentration in steel. The equation for determining Fen is given by each parameter for each material. These models, having been developed three to five years ago, should be properly revised based on new test results. This paper reviews and discusses five major topics pertinent to such revision.

An Efficient Methodology for Fatigue Reliability Analysis of Mechanical Components Based on the Stress-Life Prediction Approach

2003 ◽  
Author(s):  
Jun Tang ◽  
Young Ho Park
Keyword(s):  
Fatigue Life ◽  
Reliability Analysis ◽  
Life Prediction ◽  
Failure Modes ◽  
Theoretical Background ◽  
Fatigue Reliability ◽  
Integrated Method ◽  
Reliability Method ◽  
Mechanical Components ◽  
Prediction Approach

An efficient methodology for fatigue reliability assessment and its corresponding fatigue life prediction of mechanical components using the First-Order Reliability Method (FORM) is developed in this paper. Using the proposed method, a family of reliability defined S-N curves, called R-S-N curves, can be constructed. In exploring the ability to predict spectral fatigue life and assessing the corresponding reliability under a specified dynamics environment, the theoretical background and the algorithm of a simple approach for reliability analysis will first be introduced based on fatigue failure modes of mechanical components. It will then be explained how this integrated method will carry out the spectral fatigue damage and failure reliability analysis. By using this proposed methodology, mechanical component fatigue reliability can be predicted according to different mission requirements.

PROBABILITY VERSUS STATISTICAL MODELING: EXAMPLES FROM FATIGUE LIFE PREDICTION

2005 ◽  
Vol 12 (06) ◽  
pp. 535-550 ◽  
Author(s):  
D. GARY HARLOW
Keyword(s):  
Fatigue Life ◽  
Crack Growth ◽  
Life Prediction ◽  
Failure Modes ◽  
Growth Models ◽  
Operating Conditions ◽  
Fatigue Life Prediction ◽  
Probability Modeling ◽  
Probability Analyses

Probability analyses are increasingly being used for reliability and durability assessments for life prediction of engineered components and systems. Nevertheless, many of the current analyses are predominately statistical rather than probabilistic. Fatigue life prediction has historically been based on the safe-life or the crack growth approaches, both of which are empirically based. Consequently, they do not adequately reflect long-term operating conditions, or identify the sources and extent of their contributions to variability. A comparison between probability and statistical approaches for fatigue life prediction is developed herein. Using simple crack growth models, the variability inherent in S-N response can be related to key random variables that are readily identified in the models. The identification and quantification of these variables are paramount for predicting fatigue lives. The effectiveness of probability modeling compared to statistical methodologies is shown through the analysis of an extensive set of S-N data for 2024-T4 aluminum alloy. Subsequently, the probability approach is demonstrated with S-N data for SUJ2 steel, in which two distinct failure modes are operative. Variability associated with manufacturing and material variables are considered. The adoption of this technique to put life prediction on a sound scientific and probabilistic basis is recommended.

Review and Consideration of Unsettled Problems on Evaluation of Fatigue Damage in LWR Water

2005 ◽  
Author(s):  
Makoto Higuchi ◽  
Katsumi Sakaguchi
Keyword(s):  
Fatigue Life ◽  
Mechanical Test ◽  
Low Alloy Steels ◽  
Test Results ◽  
Considerable Effort ◽  
Test Conditions ◽  
Fatigue Data ◽  
Alloy Steels ◽  
Fatigue Life Reduction ◽  
Year 2000

Reduction in the fatigue life reduction of structural materials of nuclear components in LWR water was initially detected and examined by the authors in the 1980s, who subsequently directed considerable effort to the development of a method for evaluating this reduction quantitatively. Following the establishment of equations to calculate environmental fatigue life reduction for carbon and low alloy steels in 1985 by Higuchi and Sakamoto [1], appeared based on numerous new fatigue data obtained under various environmental and mechanical test conditions. The latest models for evaluation using Fen of the environmental fatigue life correction factor were proposed for carbon and low alloy steels in the year 2000 and for austenitic stainless steel, in 2002. Fen depends on some essential variables such as material, strain rate, temperature, dissolved oxygen and sulfur concentration in steel. The equation for determining Fen is given by each parameter for each material. These models, having been developed three to five years ago, should be properly revised based on new test results. This paper reviews and discusses five major topics pertinent to such revision.

Multi-Axial Fatigue Life Prediction of a Composite Structural Component

2010 ◽  
Author(s):  
Laura Vergani ◽  
Chiara Colombo
Keyword(s):  
Fatigue Life ◽  
Structural Component ◽  
Life Prediction ◽  
Failure Modes ◽  
Glass Fibers ◽  
Axial Loading ◽  
Experimental Tests ◽  
Fatigue Life Prediction ◽  
The Matrix ◽  
Fibers Orientation

Aim of this work is to test and understand the mechanical behavior of a composite material used to build a structural component, in particular a corner beam of a bus cabin. This component is obtained by means of the pultrusion technique and presents random and longitudinal E-glass fibers as reinforce, while the matrix is a vinyl-ester resin. A series of experimental tests was performed on specimens cut out from this beam. Different fibers orientation with respect to the direction of load application were considered: longitudinal (0°), normal (90°) and inclined (45°), thus both in uni-axial and multi-axial loading conditions. A static and fatigue characterization was carried out to identify the mechanical behaviors and the failure modes in these directions. Obtained fatigue data are then interpolated by fitting parameters required for models of fatigue life prediction.

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