• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2003.06a
• /
• pp.1270-1274
• /
• 2003

The objective of this paper is to introduce the standard of evaluation methods and fatigue test for linear motion rolling bearing. In particular, attention well be given to the list of evaluation and fatigue results in this paper. The life of a linear motion rolling bearing is given by the length of distance covered between the connection parts before the first evidence of fatigue develops in the material of one of the raceways of rolling elements. The main factors that contribute to fatigue failures include: Number of load cycles experienced; Range of stress experienced in each load cycle; Mean stress experienced in each toad cycle; Presence of local stress concentrations.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.33 no.11
• /
• pp.1341-1346
• /
• 2009

In this paper, the technique to reinforce the durability performance of structure using the sensitivity information for the frame structure is applied. The fatigue life calculation for the frame structure is performed from the quasi-static and transient analysis and the characteristics of two methods are compared for the fatigue analysis. Then the reinforcement technique is applied. First, some design variables related to the locations of fatigue failure is selected. Then sensitivities of fatigue life at fracture points with respect to the variation of design variables are calculated and the vector composed of gaps between the target life and initial life cycles is calculated. If the number of fatigue fracture points is same as the number of design variables, the variations of the design variables are calculated from the linear algebraic equation. If not, the variations of the design variables are calculated from the optimization formulation with the constraints.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
• /
• 1998.10a
• /
• pp.115-120
• /
• 1998

This paper is especially concerned with the weldment between support beam and square bar that plays important roles in control box of Expansion Joint as a bridge structure. Fatigue strength of the weldment is dependent on notch radius from welding defects and material properties. From which, tensile strength($\sigma$ult) and fatigue notch factor(Kf) become important factors to predict fatigue life. The fatigue notch sensitivity(η) for metals can be divided into two types : high and low notch sensitivity. In this work, the Expansion Joint weldment was found to have low notch sensitivity. Fatigue test of real structure was performed up to 106cycles to be compared with predicted endurance limit.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.12 no.4
• /
• pp.85-93
• /
• 2004

The variable fatigue load is simulated in this study, The stability and the life of the material are analyzed theoretically by the program of Ansys workbench. These results are successfully applied to the practical structures to predict the prevention of fracture and the endurance, The life and the damage on the every part of the fatigue specimen can be predicted. As the available lives are compared for every loading variation, the rainflow and damage matrix results can be helpful in determining the effects of small stress cycles in any loading history. The rainflow and damage matrices illustrate the possible effects of infinite life. The safety and stability of fatigue specimen according to the variable load can be estimated by using the results of this study.

• Journal of Welding and Joining
• /
• v.16 no.4
• /
• pp.73-82
• /
• 1998

This paper is especially concerned with the weldment between support beam and square bar that plays important roles in control box of Expansion Joint as a brdige structure. Fatigue strength ({TEX}$$\sigma$_{ult}${/TEX}) of the weldment is dependent on notch factor ({TEX}$K_{f}${/TEX}) become important factors to predict fatigue life. The fatigue notch sensitivity (η) for metals can be divided into two types ; high and low notch sensitivity. In this work, the Expansion Joint weldment was found to have low notch sensitivity. The maximum strain distribution during static loading is similar to the FEM analysis. Fatigue test of real structure was performed up to {TEX}$10^{6}${/TEX} cycles to be compared with predicted endurance limit.

• Journal of Welding and Joining
• /
• v.20 no.3
• /
• pp.84-90
• /
• 2002

The strength and the life of welded components are affected extensively by the residual stresses distributed around their weldments not only under static loads, but also fatigue loads. The residual stress can be superimposed with externally applied loads, so that unexpected deformations and failures of members will be occurred. These residual stresses are not kept constant, but relaxed or redistributed during in service. Under static loads the relaxation takes place when the external stress superimposed with the residual stress exceeds locally the yield stress of material used. It is shown that under fatigue loads the residual stress is considerably relieved by the first or flew cycle loading, and then gradually relaxed with increasing loading cycles. In this study the phenomenon and mechanism of the stress relaxation by mechanical means were investigated and a model to predict quantitatively the residual stress relaxation for the case of static and fatigue loading condition was proposed.

• Magazine of the Korean Society of Agricultural Engineers
• /
• v.41 no.4
• /
• pp.92-103
• /
• 1999

Recently structural damage has been frequently observed in reinforced concrete brdiges due to repeated loads such as vehicular traffic an due to continual overloads by heavy duty trucks. Therefore, the purpose of this experimental stduy is to investigate the damage mechanism due to fatigue behavior of high-strength reinforced concrete beams under repeated loads. From the test results, the relation of cycle loading to deflection is on the mid-span , the crack growth and the modes of failure according to cycle number, fatigue life and S-N curve were observed through the fatigue test. Based on the fatigue test results , high-strength reinforced concrete beams failed to 57 ∼66 percent of the static ultimate strength . Fatigue strength aobut two million cycles from S-N curves was certified by 60 percent of static ultimate strength.

• Journal of the Korean Society of Safety
• /
• v.8 no.2
• /
• pp.51-57
• /
• 1993

This study was done by ultrasonic testing. The proves used in this study were 5Z10$\times$10A70. The useful fatigue life of structural components is determined by the sum of the elapsed load cycles required to initiate a fatigue crack and to propagate the crack from subcritical size to critical dimensions. Thus, to predict the service life of many steel structures and to establish safe inspection intervals, an understanding of the Fatigue Crack Initiation and Fatigue Crack Propagation behavior in the steel is required. In the present study, the Fatigue Crack Initiation Life in SPS 5A steel was investigated by testing specimens having widely varying notch acuities. The variation in the notch acuity covered the range from notch root raidus 0.5mm to 2.5mm, and Fatigue Crack Initiation Life data were obtained in that range.

• Journal of the Korean Society for Heat Treatment
• /
• v.19 no.3
• /
• pp.163-169
• /
• 2006

Fretting is a kind of surface degradation mechanism observed in mechanical components and structures. The fretting damage decreases into 50-70% of the plain fatigue strength. The connecting rod for automobile has been used in special environments and various loading conditions. Failure of connecting rod in automotive engine may cause catastrophic situation. In this study, we investigated the fatigue characteristic of connecting rod material for an automobile. Fatigue life is defined as the number of cyclic stress to failure by regular cyclic stress. Fatigue life of C70S6 specimen was obtained from 134,000 to 147,000 cycles. Fatigue limit showed 432MPa by normal fatigue test. The other hands, it was 96MPa in the case of fretting fatigue test. It was extremely lower than that of a normal fatigue test. From observation of fracture surface, it was confirmed that the fatigue crack was initiated at the boundary of a specimen and bridge pad.

• The Journal of Korean Academy of Prosthodontics
• /
• v.45 no.6
• /
• pp.780-786
• /
• 2007

Statement of problem. The performance and maintenance of implant-supported prostheses are primarily dependent upon load transmission both at the bone-to-implant interface and within the implant-abutment-prosthesis complex. The design of the interface between components has been shown to have a profound influence on the stability of screw joints. Purpose. The Purpose of this study was to compare the strength and the fatigue resistance of 1-piece and 2-piece abutment connected to oral implant, utilizing an internal conical interface. Material and methods. Twenty $Implatium^{(R)}$ tapered implants were embedded to the top of the fixture in acrylic resin blocks. Ten $Combi^{(R)}$(1-piece) and $Dual^{(R)}$(2-piece) abutments of the same dimension were assembled to the implant, respectively. The assembled units were mounted in a testing machine. A load was applied perpendicular to the long axis of the assemblies and the loading points was at the distance of 7mm from the block surface. Half of 1-piece and 2-piece abutment-implant units were tested for the evaluation of the bending strength, and the others were cyclically loaded for the evaluation of the fatigue resistance until plastic deformation occurred. Nonparametric statistical analysis was performed for the results. Results. Mean plastic and maximum bending moment were $1,900{\pm}18Nmm,\;3,609{\pm}106Nmm$ for the 1-piece abutment, and $1,250{\pm}31Nmm,\;2,688{\pm}166Nmm$ for the 2-piece abutment, respectively. Mean cycles and standard deviation when implant-abutment joint showed a first plastic deformation were $238,610{\pm}44,891$. cycles for the 1-piece abutment and $9,476{\pm}3,541$ cycles for the 2-piece abutment. A 1-piece abutment showed significantly higher value than a 2-piece abutment in the first plastic bending moment (p<.05), maximum bending moment (p<.05) and fatigue strength (p<.05). Conclusion. Both 1-piece and 2-piece conical abutment had high strength and fatigue resistance and this suggests long-term durability without mechanical complication. However, the 1-piece conical abutment was more stable than the 2-piece conical abutment in the strength and the fatigue resistance.