Showing papers in "Transactions of The Korean Society of Mechanical Engineers A in 2000"
TL;DR: An analytical method based on modal analysis has been proposed for the transformation of dynamic loads into equivalent static load sets, which has the same effect as the dynamic optimization which uses the dynamic loads directly.
Abstract: All the loads in the real world act dynamically on structures. Since dynamic loads are extremely difficult to handle in analysis and design, static loads are utilized with dynamic factors. The dyna mic factors are generally determined based on experiences. Therefore, the static loads can cause problems in precise analysis and design. An analytical method based on modal analysis has been proposed for the transformation of dynamic loads into equivalent static load sets. Equivalent static load sets are calculated to generate an identical displacement field in a structure with that from dynamic loads at a certain time. The process is derived and evaluated mathematically. The method is verified through numerical tests. Various characteristics are identified to match the dynamic and the static behaviors. For example, the opposite direction of a dynamic load should be considered due to the vibration response. A dynamic bad is transformed to multiple equivalent static loads according to the number of the critical times. The places of the equivalent static load can be different from those of the dynamic load. An optimization method is defined to use the equivalent static loads. The developed optimization process has the same effect as the dynamic optimization which uses the dynamic loads directly. Standard examples are solved and the results are discussed
37Â citations
TL;DR: In this paper, an active steering control method is proposed such that the vehicles in slippery roads are steered as if they are driven on the normal roads, where the estimated lateral forces acting on the steering tires are compared with the reference values and the difference is compensated by the active steering method.
Abstract: Steering of the vehicles on a slippery highway is a difficult task for most passenger car drivers. The steering vehicles on slippery roads tend to slide outward with less lateral forces than on nor mal roads. When the drivers notice that their vehicles on a slippery highway start to depart from the cornering lane, most of them make a sudden steering and/or braking, which in turn may induce spin-out and instability on their vehicles. In this paper, an active steering control method is proposed such that the vehicles in slippery roads are steered as if they are driven on the normal roads. In the proposed method, the estimated lateral forces acting on the steering tires are compared with the reference values and the difference is compensated by the active steering method. A fuzzy logic controller is designed for this purpose and evaluated on a steering Hardware-In-the-Loop Simulation (HILS) system. Steering performance results on the slippery curved and sinus roads demonstrate the effectiveness of the proposed controller. This method can be realized with the steer-by-wire concept and is promising as an active safety technology.
35Â citations
TL;DR: In this research an optimization program based on a response surface method has been developed to overcome the aforementioned difficulties of gradient-based optimization.
Abstract: Gradient-based optimization methods are inefficient in applications which require expensive function evaluations, and useless in applications where objective and/or constraint functions are 'noisy' due to modeling and cumulative numerical inaccuracy since gradient evaluation results cannot be reliable. Moreover, it is difficult to be integrated with commercial analysis software, and they cannot be employed when only experimental analysis results are available. In this research an optimization program based on a response surface method has been developed to overcome the aforementioned difficulties. Various methods for design of experiments and new proposed approximation models are implemented in the program. The effectiveness of the optimization program is tested on several test problems and results are discussed.
19Â citations
TL;DR: In this paper, an efficient quad ratic approximation method is proposed in the context of trust region model management strategy, although only the linear and quadratic terms are uniquely determined using 2n+1 design points, the two-factor interaction terms are mathematically updated by normalized quasi-Newton formula.
Abstract: For effective construction of second-order response surface models, an efficient quad ratic approximation method is proposed in the context of trust region model management strategy. In the proposed method, although only the linear and quadratic terms are uniquely determined using 2n+1 design points, the two-factor interaction terms are mathematically updated by normalized quasi-Newton formula. In order to show the numerical performance of the proposed approximation method, a sequential approximate optimizer is developed and solves a typical unconstrained optimization problem having 2, 6, 10, 15, 30 and 50 design variables, a gear reducer system design problem and two dynamic response optimization problems with multiple objectives, five objectives for one and two objectives for the other. Finally, their optimization results are compared with those of the CCD or the 50% over-determined D-optimal design combined with the same trust region sequential approximate optimizer. These comparisons show that the proposed method gives more efficient than others.
17Â citations
TL;DR: In this paper, the behavior of a diaphragm spring is analyzed by finite element method to calculate sensitivity of design parameters, which is used to perform optimal design of diaphrasm spring shape.
Abstract: A diaphragm spring is an important component of a clutch assembly, characteristics of which depends largely on that of a diaphragm spring. A diaphragm spring is subject to high stress concentration in driving condition, which frequently causes cracks and fracture around finger area. In this paper, behavior of a diaphragm spring is analysed by finite element method to calculate sensitivity of design parameters, which is used to perform optimal design of diaphragm spring shape. As an object function, hoop stresses are taken and minimized to improve durability. Characteristics of the diaphragm is used as equality constraint to maintain the original design purpose and sequential linear programming(SLP) is utilized as an optimization tool. With optimized design, it is verified that concentrated stress is decreased maintaining release load characteristic.
14Â citations
7Â citations
TL;DR: In this article, the shape optimization is performed to minimize the judder of ventilated disc brake rotor that is induced by the thermal deformation of the disc, and an optimum design is then performed minimizing the deformation factor with the design variables of the shape of disc.
Abstract: The shape optimization is performed to minimize the judder of ventilated disc brake rotor that is induced by the thermal deformation of the disc. A three-dimensional finite element is developed to analyze the coupled system of temperature and displacement field, and the thermal conductivity and mechanical stiffness matrices are simultaneously taken into account. To reduce computing time, an equivalent heat transfer rate is introduced approximating the heat transfer rate on the disc surface. A deformation factor is introduced to describe the thermal deformation causing the judder. The deformation factor is chosen as an objective function in the optimization process. Consequently an optimum design is then performed minimizing the deformation factor with the design variables of the shape of the disc. The optimum design procedure presented in this study is proven to be an effective method of minimizing the judder, and it reduces the thermal deformation by 23% of the initial geometry.
7Â citations
TL;DR: In this paper, the densification behavior of mixed copper and tool steel powder under cold compaction was investigated, by mixing the yield functions proposed by Fleck et al. and by Gurson for pure powder in terms o f volume fractions and contact numbers of Cu powder.
Abstract: Densification behavior of mixed copper and tool steel powder under cold compaction- was investigated. By mixing the yield functions proposed by Fleck et al. and by Gurson for pure powder in terms o f volume fractions and contact numbers of Cu powder, new mixed yield functions were employed for densification of powder composites under cold compaction. The constitutive equations were implemented into a finite element program (ABAQUS) to compare with experimental data and with calculated results from the model of Kim et al. for densification of mixed powder under cold isostatic pressing and cold die compaction. Finite element calculations by using the yield functions mixed by contact numbers of Cu powder agreed better with experimental data than those by volume fractions of Cu powder.
7Â citations
TL;DR: In this article, the authors investigated the energy absorption characteristics of CFRP (Carbon Fiber Reinforced Plastics) tubes on static and impact tests and found that the response is complex and depends on the interaction between the different mechanisms that control the crushing process.
Abstract: Because of the inherent flexibility in their design for improved material properties, composites have wide applications in aerospace vehicles and automobiles. The purpose of this study is to investigate the energy absorption characteristics of CFRP( Carbon Fiber Reinforced Plastics); tubes on static and impact tests. Static compression tests have been carried out using the static testing machine(Shin-gang buckling testing machine)and impact compression tests have been carried out using the vertival crushing testing machine. When such tubes were subjected to crushing loads, the response is complex and depends on the interaction between the different mechanisms that control the crushing process. The collapse characteristics and energy absorption were examined. Trigger and interlaminar number affect energy absorption capability of CFRP tubes.
7Â citations
TL;DR: In this paper, a new tester that uses magnetism was devised to acquire data of the change of glass transition temperature and made Cha-Yoon model that can predict the change.
Abstract: The industries use polymer materials for many purposes because they have many merits. But these materials' costs take up too much proportion in overall cost of products that use these materials as their major material. So it is very economical for polymer industries to reduce these costs. Microcellular foaming process appeared in 1980's to solve this problem and it proved to be quite successful. This process uses inert gases such as CO2, N2. As these gases are dissolved into polymer matrices. many properties are changed. Glass transition temperature is one of these properties. DSC, DMA are devices that measures this temperature, but these are not sufficient to measure the temperature of polymer containing gas. In this paper, we devised a new tester that uses magnetism. We used this device to acquire data of the change of glass transition temperature and made Cha-Yoon model that can predict the change of glass transition temperature. Using this model, the change of this temperature can be estimated as a function of weight gain of gas. Cha-Yoon model proved that Chow's model is inappropriate to predict the change of glass transition temperature of polymer matrices containing gas.
6Â citations
TL;DR: The model of a thermal error using fuzzy logic strategy overcomes limitation of accuracy in the linear regression model or the engineering judgment model and shows that the fuzzy model has more better performance thanlinear regression model, though it has less number of thermal variables than the other.
Abstract: As current manufacturing processes require high spindle speed and precise machining, increasing accuracy by reducing volumetric errors of the machine itself, particularly thermal errors, is very important. Thermal errors can be estimated by many empirical models, for example, an FEM model, a neural network model, a linear regression model, an engineering judgment model, etc. This paper discusses to make a modeling of thermal errors efficiently through backward elimination and fuzzy logic strategy. The model of a thermal error using fuzzy logic strategy overcomes limitation of accuracy in the linear regression model or the engineering judgment model. It shows that the fuzzy model has more better performance than linear regression model, though it has less number of thermal variables than the other. The fuzzy model does not need to have complex procedure such like multi-regression and to know the characteristics of the plant, and the parameters of the model can be mathematically calculated. Also, the fuzzy model can be applied to any machine, but it delivers greater accuracy and robustness.
TL;DR: In this paper, the relationship between axiomatic design and structural optimization is investigated and Logical Decomposition method is developed for a systematic structural optimization, the entire optimization process is decomposed to satisfy the Independence axiom.
Abstract: The Design Axioms provide a general framework for design methodologies. The axiomatic design framework has been successfully applied to various design tasks. However, the axiomatic design has been rarely utilized in the detailed design process of structures where the optimization technology is generally carried out. The relationship between the axiomatic design and the optimization is investigated and Logical Decomposition method is developed for a systematic structural optimization. The entire optimization process is decomposed to satisfy the Independence Axiom. In the decomposition process, design variables are grouped according to sensitivities. The sensitivities are evaluated by the Analysis of Variance(ANOVA) to avoid considering only local values. The developed method is verified through examples such as the twenty -five members transmission tower and the two -bay-six-story frame.
TL;DR: In this article, a generalized integration method applicable for various types of constitutive equations is developed and implemented into ABAQUS by means of UMAT subroutine, and the solution of the non-linear system of algebraic equations arising from time discretization with the generalized midpoint rule is determined using line-search technique in combination with Newton method.
Abstract: The prediction of the inelastic behavior of the structure is an essential part of reliability assessment procedure, because most of the failures are induced by the inelastic deformation, such as creep and plastic deformation. During decades, there has been much progress in understanding of the inelastic behavior of the materials and a lot of inelastic constitutive equations have been developed. These equations consist of the definition of inelastic strain and the evolution of the state variables introduced to quantify the irreversible processes occurred in the material. With respect to the definition of the inelastic strain, the inelastic constitutive models can be categorized into elastoplastic model, unified viscoplastic model and separated viscoplastic model and the different integration methods have been applied to each category. In the present investigation, the generalized integration method applicable for various types of constitutive equations is developed and implemented into ABAQUS by means of UMAT subroutine. The solution of the non-linear system of algebraic equations arising from time discretization with the generalized midpoint rule is determined using line-search technique in combination with Newton method. The strategy to control the time increment for the improvement of the accuracy of the numerical integration is proposed. Several numerical examples are considered to demonstrate the efficiency and applicability of the present method. The prediction of the inelastic behavior of the structure is an essential part of reliability assessment procedure, because most of the failures are induced by the inelastic deformation, such as creep and plastic deformation. During decades, there has been much progress in understanding of the inelastic behavior of the materials and a lot of inelastic constitutive equations have been developed. These equations consist of the definition of inelastic strain and the evolution of the state variables introduced to quantify the irreversible processes occurred in the material. With respect to the definition of the inelastic strain, the inelastic constitutive models can be categorized into elastoplastic model, unified viscoplastic model and separated viscoplastic model and the different integration methods have been applied to each category. In the present investigation, the generalized integration method applicable for various types of constitutive equations is developed and implemented into ABAQUS by means of UMAT subroutine. The solution of the non-linear system of algebraic equations arising from time discretization with the generalized midpoint rule is determined using line-search technique in combination with Newton method. The strategy to control the time increment for the improvement of the accuracy of the numerical integration is proposed. Several numerical examples are considered to demonstrate the efficiency and applicability of the present method.
TL;DR: The HILs system will useful for developing the control logic for the EPS system and could by used to analyze control-parameters of a EPS that contributes to the maneuverability and stability of a vehicle.
Abstract: In this study, a Hardware-In-The-Loop-Simulation(HILS) system for developing a Electric-Power-Steering(EPS) system is designed. To test a EPS by HILS system, a mathematical vehicle model with a steering system model has been constructed. This mathematical model has been constructed. This mathematical model has been downloaded to the Digital-Signal-Processor(DSP) board. To realize the lateral force acting on the front wheel in a real car. the steering wheel angle sensor and vehicle velocity have been used for input signal. The force sensor has been used for a feedback signal. The full vehicle states could by simulated by the HILS system. Consequently, the HILS system could by used to analyze control-parameters of a EPS that contributes to the maneuverability and stability of a vehicle. At the same time, the HILS system can evaluate the whole performance of the vehicle-steering system. Also the HILS system could do test could not be executed in real vehicle. The HILs system will useful for developing the control logic for the EPS system.
TL;DR: In this paper, a new particle tracing algorithm is presented in order to describe the advancement of core polymer melt during filling stage, which is the main advantage of this algorithm is the use of identity field information rather than tracking a set of fluid particles.
Abstract: Recently, the sandwich injection molding has drawn attention because it offers the flexibility of using the optimal properties of two different but compatible polymers and is also one of the most p romising methods in connection with recycling of thermoplastics. In this paper, a new particle tracing algorithm is presented in order to describe the advancement of core polymer melt during filling stage. The main advantage of this algorithm is the use of identity field information rather than tracking a set of fluid particles. In addition, to model the process accurately, especially to detect the possible
TL;DR: In this paper, the split Hopkinson pressure bar (SHPB) technique with a special experimental apparatus can be used to obtain the material properties under high strain rate loading condition and tensile loading condition.
Abstract: Mechanical properties of the materials used for transportations and industrial machinery under high stain rate loading conditions have been required to provide appropriate safety assessment to these mechanical structures The Split Hopkinson Pressure Bar(SHPB) technique with a special experimental apparatus can be used to obtain the material properties under high strain rate loading condition There have been many studies on the material behavior under high strain rate compressive loading compared to those under tensile loading In this paper, mechanical properties of the aluminum alloy, Al6061-T6, under high strain rate tensile loading were determined using SHPB technique
TL;DR: In this paper, the static and cyclic behavior of single overlap AI-alloy and steel (SPCC) joints was investigated and relationships were developed to estimate the strength of the joint taking into consideration base metal strength properties and the geometry of a joint.
Abstract: Mechanical press joining technique has been used in sheet metal joining processes because of its simple process and possibility of joining dissimiliar metals, such as steel and aluminum. The static and cyclic behavior of single overlap AI-alloy and steel(SPCC) joints has been investigate. Relationships were developed to estimate the strength of the joint taking into consideration base metal strength properties and the geometry of the joint. Fatigue test results have shown that fatigue resistance of the SPCC mechanical press joints is almost equal to that of the spot weld at the life of cycles. Also, the dissimilar material jointed specimen with upper SPCC plate and button diameter corresponding to the nugget diameter of the spot welded specimen has almost same strength as the same material jointed specimen and as the spot welded specimen.
TL;DR: In this paper, neural networks on the basis of X-ray half breadth ratio B/ fractal dimension and fracture mechanical parameters can predict fatigue crack growth rate da/dN and cycle ratioN/ at the same time within engineering estimated mean error(5%).
Abstract: Fatigue crack growth and life is estimated by various fracture mechanical parameters but affected by load, material and environment. Fatigue character of component without surface notch cannot be e valuated by above-mentioned parameters due to microstructure of in-service material. Single fracture mechanical parameter or nondestructive parameter cannot predict fatigue damage in arbitrary boundary condition but multiple fracture mechanical parameters or nondestructive parameters can Fatigue crack growth modelling with three point representation scheme uses this merit but has limit on real-time monitoring. Therefore, this study shows fatigue damage model using backpropagatior. neural networks on the basis of X-ray half breadth ratio B/ fractal dimension and fracture mechanical parameters can predict fatigue crack growth rate da/dN and cycle ratioN/ at the same time within engineering estimated mean error(5%).
TL;DR: In this article, wear tests were conducted with reciprocating motion under dry sliding conditions, and specific wear rate was measured as a function of sliding distance, and the dominant wear mechanism found were adhesion and abrasion.
Abstract: Nylon, Polyacetal and PTFE were studied to gain a better understanding of their tribological behavior. Wear tests were conducted with reciprocating motion under dry sliding conditions. Friction coefficient and specific wear rate were measured as a function of sliding distance. The worn surfaces were examined with a Scanning Electron Microscope(SEM). Polyacetal showed lowest specific wear rates and PTFE exhibited lowest friction coefficient. The dominant wear mechanism found were adhesion and abrasion
TL;DR: Even though the global convergence cannot be guaranteed, the proposed technique makes it possible to optimize the structures under dynamic loads and has also applicability, flexibility, and reliability.
Abstract: This paper presents a quasi-static optimization technique for elastic structures under dynamic loads. An equivalent static load (ESL) set is defined as a static load set which generates the same displacement field as that from a dynamic load at a certain time. Multiple ESL sets calculated at every time step are employed to represent the various states of the structure under the dynamic load. They can cover every critical state that might happen at an arbitrary time. Continuous characteristics of dynamic load are simulated by multiple discontinuous ones of static loads. The calculated sets of ESLs are applied as a multiple loading condition in the optimization process. A design cycle is defined as a circulated process between an analysis domain and a design domain. Design cycles are repeated until a design converges. The analysis domain gives a loading condition necessary for the design domain. The design domain gives a new updated design to be verified by the analysis domain in the next design cycle. This iterative process is quite similar to that of the multidisciplinary optimization technique. Even though the global convergence cannot be guaranteed, the proposed technique makes it possible to optimize the structures under dynamic loads. It has also applicability, flexibility, and reliability
TL;DR: In this paper, the authors investigated the temperature, degree of cure and consolidation of a 20 mm thick unidirectional glass/epoxy laminate using an experiment and a 3-dimentional numerical analysis.
Abstract: During the curing process of thick glass/epoxy laminates, a substantial amount of temperature lag and overshoot at the center of the laminates is usually experienced due to the large thickness and low thermal conductivity of the glass/epoxy composites. Also, it takes a longer time for full and uniform consolidation. In this work, temperature, degree of cure and consolidation of a 20 mm thick unidirectional glass/epoxy laminate were investigated using an experiment and a 3-dimentional numerical analysis. From the experimental and numerical results, it was found that the experimentally obtained temperature profile agreed well with the numerical one, and the cure cycle recommended by the prepreg manufacturer should be modified to prevent a temperature overshoot and to obtain full consolidation.
TL;DR: In this article, the authors assess safety at the cracked AI-plate repaired by Br/Epoxy composite patch using elastic analysis and finite element analysis, and the problem of how to optimize the geometric configurations of the patch has been discussed.
Abstract: Adhesive bonding repair methods has been used for a number of decades for construction of damaged structures. In order to evaluate the life of cracked aging aircraft structures, the repair technique which uses adhesively bonded boron/epoxy composite patches is being widely considered as a cost-effective and reliable method. But, this repair method contains many shortcomings. One of these shortcomings, debonding is major issue. When the adhesive shear stress increases, debonding is caused at the end of patch and plate interface. And this debonding is another defect except cracks propagation. In this paper, we assess safety at the cracked AI-plate repaired by Br/Epoxy composite patch. Firstly, from the view of fracture mechanics, reduction of stress intensity factors is determined by the variety of patch feature. Secondly, using the elastic analysis and finite element analysis, the distribution of adhesive shear stresses is acquired. Finally, The problem of how to optimize the geometric configurations of the patch has been discussed.
TL;DR: In this article, a genetic algorithm was used to obtain the optimal processing conditions for minimizing the volumetric shrinkage of molded parts, which served as analysis tool for the capability of searching optimal processing condition but also greatly reduced the calculation time by utilizing the information of searching area.
Abstract: Precision injection molding is an important technology for improving productivity and lowering costs in the fields of medical components, lenses and electrical connectors. The quality of injection molded parts is affected by various processing conditions such as filling time and packing pressure profile. It is difficult to consider all the variables at the same time for prediction of the quality. In this study, the genetic algorithm was used to obtain the optimal processing conditions for minimizing the volumetric shrinkage of molded parts. For a higher convergence rate, the method of design of experiments was used to analyze the relationship between processing conditions and volumetric shrinkage of molded parts, which served as analysis tool for the capability of searching optimal processing conditions but also greatly reduces the calculation time by utilizing the information of searching area. As a practical example, compact disks that require micron-level precision were chosen for the study.
TL;DR: In this paper, a finite crack with free surface traction and surface charge under anti-plane shear is considered and Fourier transforms are used to reduce the problem to two pairs of dual integral equations, which are then expressed in terms of Fredholm integral equations of the second kind.
Abstract: Using the theory of linear piezoelectricity, we consider the problem of piezoelectric ceramic infinite strip containing a finite crack with free surface traction and surface charge under anti-plane shear. The crack is symmetrically parallel to the edges of infinite strip. Fourier transforms are used to reduce the problem to two pairs of dual integral equations, which are then expressed in terms of Fredholm integral equations of the second kind. Numerical results for PZT-5H ceramic are obtained and discussed.
TL;DR: In this article, a finite element analysis of the influence of misalignment between the drilling hole and the strain gage center is presented, and the correction equations which easily obtain the residual stress taking account of the hole eccentricity are derived.
Abstract: The measurement of residual stresses by the hole-drilling method has been commonly used to evaluate residual stresses in structural members. In this method, one of the source of error is due to the misalignment between the drilling hole and strain gage center. This paper presents a finite element analysis of the influence of such misalignment for the uniaxial residual stress field. The stress error increases proportionally to hole eccentricity. The correction equations which easily obtain the residual stress taking account of the hole eccentricity are derived. The stress error due to the hole eccentricity decreases by approximately one percent using this equations.
TL;DR: In this paper, a new design method of prosthetic foot was suggested which can evaluate the performance by implementing amputee's gait simulation using the finite element analysis, and the performance evaluations were performed using the Taguchi method with orthogonal array L25.
Abstract: In this study, new design method of prosthetic foot was suggested which can evaluate the performance of prosthetic foot by implementing amputee's gait simulation using the finite element analysis. The basic shape of ESPF(Energy Storing Prosthetic Foot) was designed which is suitable for the below-knee amputee considering mechanical properties and kinematic properties. And, the performance evaluations were performed using the Taguchi method with orthogonal array L25. As a result, average main effect of factors for the ESPF's performance were calculated and then optimum condition of given shape was selected. Essential particulars for the performance evaluation from the simulation result were the quantity of external work needed in stance phase, the quantity of transferred energy from the ESPF through the knee, and the vertical displacement of knee at toe-off. Reasonable optimum condition was obtained from the using performance index. From this study, it was found that it is necessary for the design of ESPF to consider the geometrical data related to the magnitude of load on elastic material.
TL;DR: In this paper, a finite element interface system for the design of optimal spot welding locations has been developed, where quadrilateral shell elements are automatically generated for finite element analysis of spot welded structured, which employs a domain decomposition method and adaptive mesh(h-method).
Abstract: A finite element interface system for the design of optimal spot welding locations has been developed. In order to find out the optimal locations of spot welding points, iterative finite element an alyses are necessary, and thus automatic generation of finite element model for the structures with spot welded pointsis required. In this interface system, quadrilateral shell elements are automatically generated for finite element analysis of spot welded structured, which employs a domain decomposition methodand adaptive mesh(h-method).
TL;DR: In this article, an integrated approach, which is independent of specimen geometry and loading type, is proposed for predicting the fatigue life of spot welded specimens, based on finite element models.
Abstract: This paper proposes an integrated approach, which is independent of specimen geometry and loading type, for predicting the fatigue life of spot welded specimens. We first establish finite element models reflecting the actual specimen behaviors observed on the experimental load-deflection curves of 4 types of single spot welded specimens. Using finite element models elaborately established, we then evaluate fracture parameter J-integral to describe the effects of specimen geometry and loading type on the fatigue life in a comprehensive manner. It is confirmed, however, that J-integral concept alone is insufficient to clearly explain the generalized relationship between load and fatigue life of spot welded specimens. On this ground, we introduce another effective parameter composed of , , , which has been demonstrated here to more sharply define the relationship between load and fatigue life of 4 types of spot welded specimens. The crack surface displacement method is adopted for decomposition of J, and the mechanism of the mixed mode fracture is also discussed in detail as a motivation of using
TL;DR: In this article, the hysteresis phenomena of the hunting motion in a railway passenger car having a bolster has been revealed and bifurcation analysis is used to predict its outbreak velocities.
Abstract: This research has been performed to reveal the hysteresis phenomena of the hunting motion in a railway passenger car having a bolster Since linear analysis can not explain them, bifurcation analysis is used to predict its outbreak velocities in this paper However bifurcation analysis is attended with huge computing time, thus this research proposes more effective numerical algorithm to reduce it than previous researches Stability of periodic solution is obtained by adapting of Floquet theory while stability of equilibrium solutions is obtained by eigen-value analysis As a result, linear and nonlinear critical speed are acquired Full scale roller rig test is carried out for the validation of the numerical result Finally, it is certified that there are many similarities between numerical and test results