Page 1. FATIGUE TESTING Theory and Practice Page 2. Fatigue Testing and Analysis (Theory and Practice) Page 3. Page 4. Fatigue Testing and Analysis (Theory and Practice) Yung-Li Lee DaimlerChrysler Jwo Pan University ...
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This presentation will focus on the reliability design validation process. The definitions of fatigue, durability and reliability will be first introduced. The method to acquire customer usage information for durability design was... more
This presentation will focus on the reliability design validation process. The definitions of fatigue, durability and reliability will be first introduced. The method to acquire customer usage information for durability design was conceptually discussed. The accelerated durability test development technologies at Proving Grounds and Labs will be presented. Finally, the reliability demonstration test
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Why should wait for some days to get or receive the fatigue testing and analysis book that you order? Why should you take it if you can get the faster one? You can find the same book that you order right here. This is it the book that you... more
Why should wait for some days to get or receive the fatigue testing and analysis book that you order? Why should you take it if you can get the faster one? You can find the same book that you order right here. This is it the book that you can receive directly after purchasing. This fatigue testing and analysis is well known book in the world, of course many people will try to own it. Why don't you become the first? Still confused with the way?
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The bolt joint design and analysis is surprisingly complicated and has been the most important and challenging element in a complex bolted structure. Even though there are many approaches ( Norton, 1996 ; Brickford and Nassar, 1998 ;... more
The bolt joint design and analysis is surprisingly complicated and has been the most important and challenging element in a complex bolted structure. Even though there are many approaches ( Norton, 1996 ; Brickford and Nassar, 1998 ; Juvinall and Marshek, 2000 ; Shigley and Mischke, 2001 ; VDI, 2003 ) that have been proposed, there is no universally accepted calculation model that is best in all design situations. Among all the methods, the VDI 2230 (Systematic Calculation of High Duty Bolted Joints—Joints with One Cylindrical Bolt) has been recognized as a standard work for calculating bolted joints around the world.
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Fatigue failure under out-of-phase loading is a fairly common type of damage mode. For the reliable design of mechanical components under such loading, there is a strong need for the development of a compatible fatigue life prediction... more
Fatigue failure under out-of-phase loading is a fairly common type of damage mode. For the reliable design of mechanical components under such loading, there is a strong need for the development of a compatible fatigue life prediction criterion. Many multiaxial fatigue theories have been developed since the early 1900s, and most of them are limited to proportional loading cases. Although some can be extended for out-of-phase loading, additional work must be done for general applicability. In this paper, data are correlated using an empirically modified approach which attempts to be more general. Modified from Findley's formula, this approach incorporates three mathematical expressions for the effects of out-of-phase loading, mean bending stress, and mean torsional stress on fatigue behavior. The reliability of this approach is evaluated by comparing analytically predicted results with experimental data from various publications.
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Experimental fatigue techniques provide the most accurate means of determining the crankshaft operating loads and fatigue strength. A safety factor is then calculated by comparing the two variables. Inadequate values indicate the need for... more
Experimental fatigue techniques provide the most accurate means of determining the crankshaft operating loads and fatigue strength. A safety factor is then calculated by comparing the two variables. Inadequate values indicate the need for crankshaft redesign. ...
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There are many existing test methods and data reduction techniques for statistical properties of fatigue strength at a specific fatigue life, but none of them have been validated by experiment and simulation. Validation by simulation is... more
There are many existing test methods and data reduction techniques for statistical properties of fatigue strength at a specific fatigue life, but none of them have been validated by experiment and simulation. Validation by simulation is preferable because high cycle ...
Research Interests: Engineering, Mechanical Engineering, Civil Engineering, Structural Engineering, Fatigue, and 15 moreComputer Simulation, Data Reduction, Coefficient of Variation, Statistical Properties, Limit Distribution, Fatigue Life, Projection Method, Low Cycle Fatigue, Extrapolation, Accelerated Testing, Fatigue Strength, Data Reduction Techniques, Statistical distribution theory, Fatigue Limit, and Statistical evaluation
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Vehicle bracket components, such as engine motor mounts, transmission mounts, and differential pinion nose damper brackets, are widely used in the automotive industry for structural support and noise reduction. Load acquisition is often... more
Vehicle bracket components, such as engine motor mounts, transmission mounts, and differential pinion nose damper brackets, are widely used in the automotive industry for structural support and noise reduction. Load acquisition is often required for design and weight optimisation, while damage assessment is used to assure the reliability of a product. This paper presents a complete process for load acquisition and reliability–based damage assessment, with which engineers may evaluate the strength of the prototype in an up–front design stage. Design of Experiments (DOE) is incorporated to minimise the number of strain gages used in a matrix–formed multiaxial load transducer. The effect of driver variability on the damage levels is also demonstrated.
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A suspension design process for passenger vehicles is demonstrated to meet the vehicle directional control response parameters. This process has been proved to be a satisfactory proactive design tool for suspension engineers to minimize... more
A suspension design process for passenger vehicles is demonstrated to meet the vehicle directional control response parameters. This process has been proved to be a satisfactory proactive design tool for suspension engineers to minimize time and cost at up–front design stage. The whole process consists of three phases: (1) identifying the sensitive suspension parameters affecting vehicle handling; (2) selecting the appropriate suspension parameters to meet target handling values; and (3) evaluating proposed suspension alternatives in different handling conditions such as cornering at high lateral acceleration, braking/thrust in a turn and step–steer transient analysis. Based on Taguchi's orthogonal fractional factorials, a 10–degree–of–freedom vehicle simulation model is used to rank the severity of the input suspension factors to the selected output handling parameters and to evaluate the handling performance of different suspension alternatives. Moreover, a case study is perfo...
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This paper evaluates the effect of different Poisson's ratios and an equivalent Poisson's ratio formula on the crack initiation angle and life estimation by using the three shear-strain based fatigue damage models (Brown–Miller,... more
This paper evaluates the effect of different Poisson's ratios and an equivalent Poisson's ratio formula on the crack initiation angle and life estimation by using the three shear-strain based fatigue damage models (Brown–Miller, Fatemi–Socie, and Liu's Virtual Energy) on strain-controlled biaxial cyclic loading tests of specific tubular material specimens. The four shear failure mode materials studied were Inconel 718, 304L stainless steel, normalized 1050, and quenched/tempered 1050 steels. This study was motivated by the fact that for all the strain-controlled fatigue testing, the induced transverse strain was not measured, but assumed to be a negative product of the axial strain and the Poisson ratio, where the axial strain was known and given, and the Poisson ratio was either assumed to be a constant or a variable represented by a function of elastic and plastic equivalent strains. Therefore, the assumption of a Poisson's ratio in the transverse strain calculation was assessed in this study. It is concluded that the use of different Poisson's ratios in the three fatigue damage models would have some effects on the crack angle prediction, depending on the material type, and little effect on the fatigue life estimation for all materials investigated in this study.
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Among the causes for the breaking down of mechanical components, fatigue damage under cyclic stresses is by far the most common. Since this kind of damage is located in areas subject to the maximum cyclic stress amplitude, geometrical... more
Among the causes for the breaking down of mechanical components, fatigue damage under cyclic stresses is by far the most common. Since this kind of damage is located in areas subject to the maximum cyclic stress amplitude, geometrical notches appear to be the most important site for fatigue failure. Understanding of the stress concentrators (notches) is an important element in the prevention of component failure, and is commonly assessed by a finite element analysis (FEA). In this research, it is intended to develop a methodology to automate the strain-based fatigue analysis in the FEA where the stress gradient and local plasticity effects are taken into account. The stress gradient effect is included by an empirical model to correlate the relative stress gradient (RSG) due to a stress raiser Kf, and the local notch plasticity with the fatigue notch factor is approximated by the modified Neuber rule. The FEA modelling guidelines to extract the RSG value are then proposed for improved accuracy.
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Resistance spot-welding technology has been widely employed in joining thin sheet metals in the automotive industry for decades. During the service life of structures, the resistance spot-welded joints are frequently exposed to various... more
Resistance spot-welding technology has been widely employed in joining thin sheet metals in the automotive industry for decades. During the service life of structures, the resistance spot-welded joints are frequently exposed to various services’ loading conditions that could result in potential fatigue failure. Thus, design engineers are always interested in understanding fatigue behavior of the spot-welded joints and in predicting fatigue life of the spot-welded joints. However, the fatigue life prediction of resistance spot-welded joints is often complicated and inaccurate because many parameters can affect the fatigue life of welded joints.
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... are directly included in the large empirical database for structural steels, but the residual stresseffect due to ... Here C is a fitting material coefficient; AK,,/, 50_1 and AK,,),> 0_, are the stress intensity factor ... a... more
... are directly included in the large empirical database for structural steels, but the residual stresseffect due to ... Here C is a fitting material coefficient; AK,,/, 50_1 and AK,,),> 0_, are the stress intensity factor ... a m.(10.42) 6/1-991 (M9) lfmlzi-rlfmlzi-fblziil I (r) is a dimensionless function ...
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The resistance spot welding process has been widely used in the automotive industry for decades. Once the vehicle weight reduction by down-gaging sheet metal and down-sizing reinforcements becomes of importance, the fatigue performance of... more
The resistance spot welding process has been widely used in the automotive industry for decades. Once the vehicle weight reduction by down-gaging sheet metal and down-sizing reinforcements becomes of importance, the fatigue performance of spot welds will be a critical factor in design and analysis. Since most of the existing analytical approaches are still deterministic and too complicated to use,
Research Interests: Computer Science, Structural Engineering, Automotive Industry, Welding, Reliability Analysis, and 11 moreReliability, Resistance Spot Welding, Weight Reduction, Sheet Metal, Weibull distribution, Fatigue Life, Spot Welding, Probability of Failure, Beta Distribution, cross sectional area, and RESISTANCE WELDING
Laboratory testing is a critical step in the development of vehicle components or systems. It allows the design engineer to evaluate the design early in the reliability development phase. A good lab test will shorten the product... more
Laboratory testing is a critical step in the development of vehicle components or systems. It allows the design engineer to evaluate the design early in the reliability development phase. A good lab test will shorten the product development cycles and minimizes cost and part failures at the proving ground (PG) testing before the vehicle volume production. In this paper, reliability-based
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This report explores the relationship of different failure criteria - specifically, surface cracks, stiffness changes, and two-piece failures - on rolled, ductile, cast-iron crankshafts. Crankshaft samples were closely monitored... more
This report explores the relationship of different failure criteria - specifically, surface cracks, stiffness changes, and two-piece failures - on rolled, ductile, cast-iron crankshafts. Crankshaft samples were closely monitored throughout resonant bending fatigue testing and were taken to near complete fracture. By monitoring resonance shifts of the samples during testing, stiffness changes and cracks were monitored. These data showed that an accelerating frequency shift was sufficient to indicate imminent two-piece failure and that this condition can be used as a failure criterion. Fatigue studies on two different crankshafts using this failure criterion were compared to those using a surface crack failure criterion. This comparison showed that using the surface crack failure criterion erroneously decreased the apparent fatigue life of the crankshaft significantly. These results support the theory of crack arrest in the fillet area of rolled crankshafts and raise a significant challenge in the use of the surface crack failure criterion due to its inconsistent correlation to two-piece failure.
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There are two commonly used vibration test methods in the engineering industry to validate a product to meet its durability and design life requirements, sinusoidal vibration and random vibration. The choice of the test method depends on... more
There are two commonly used vibration test methods in the engineering industry to validate a product to meet its durability and design life requirements, sinusoidal vibration and random vibration. The choice of the test method depends on the source of the dominant forcing input. For example, sinusoidal vibration is often used for testing engine accessories, manifolds, and components mounted on manifolds that are primarily experienced engine firing loads. Random vibration is usually applied to vehicle body, frame, and chassis subjected to random road load inputs.
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Cyclic plasticity deals with nonlinear stress–strain responses of a material subjected to external cyclic loading. The theory of plasticity is a part of the broad and fascinating subject of mechanics of materials or continuum mechanics,... more
Cyclic plasticity deals with nonlinear stress–strain responses of a material subjected to external cyclic loading. The theory of plasticity is a part of the broad and fascinating subject of mechanics of materials or continuum mechanics, which spans the spectrum from the fundamental aspects of elastic and inelastic behavior to the practical solution of engineering problems. The impact of cyclic plasticity on the design and analysis of mechanical systems and its role in assessing integrity of structures are well recognized because plastic deformation is almost inevitable to avoid in many design situations and plays a pivotal role in the design and failure analyses of many mechanical components.