A Study on the Dynamic Load Simulation for a Crawler Excavator Considering Ground Effect

2012 ◽  
Author(s):  
Seongpil Yang ◽  
Mooseung Kim ◽  
Donghyeon Hwang ◽  
Panyoung Kim
Keyword(s):  
Fatigue Life ◽  
Dynamic Load ◽  
Ground Effect ◽  
Fatigue Load ◽  
Track System ◽  
Multibody Dynamic ◽  
Reaction Forces ◽  
Fatigue Loads ◽  
Load Simulation ◽  
Design Factors

A fatigue life is one of the key design factors for crawler excavators because they are usually operated in a very harsh working condition. In order to evaluate the fatigue life, the fatigue loads in various working conditions should be decided in advance. In case of the attachments such as boom and arm, the forces at the bucket tip due to digging and lifting are primary fatigue loads, which can be calculated relatively easily using design specifications. However, the forces at the track need to be considered additionally for the upper and lower frames. And it is almost impossible to measure the forces at track in a field test. In this study, a dynamic model of excavator including track system is implemented and dynamic load simulations are carried out to investigate the distribution of the reaction forces at each roller for the typical working scenarios. The model and the simulation technique are verified by comparison with the results of measurement in view of weight balance, cylinder forces, accelerations of counter weight and stresses at concerned points. The normalized distribution of the reaction forces at each roller in digging and lifting working mode are presented and the distribution is expected to be used as the baseline of fatigue load estimation for the upper and lower frames of various class crawler excavators. To get the multibody dynamic simulation results by the excavator motion, we used the commercial software such as Recurdyn for kinematic and dynamic modeling. Especially the track modeling of the excavator is composed using Track_LM module of the Recurdyn. And stress analysis of the frame is carried out using the NX-Nastran program.

scholarly journals Modification of Zenner and Liu Criterion due to Non-Proportionality of Fatigue Load by Means of MCE Approach

2014 ◽  
Vol 598 ◽  
pp. 201-206 ◽  
Author(s):  
Łukasz Pejkowski ◽  
Dariusz Skibicki
Keyword(s):  
Fatigue Life ◽  
Experimental Verification ◽  
Band 3 ◽  
Damage Parameter ◽  
Fatigue Load ◽  
Proportional Loading ◽  
Ellipse Method ◽  
Multiple Materials

The results of experimental verification of Zenner and Lius criterion confirm its efficiency in the case of estimation of fatigue life for proportional loading. Due to application of general damage parameter, the criterion is useful in case of various types of proportional loading and for multiple materials. However, for non-proportional loadings, of high non-proportionality level, the error of estimation of fatigue lives often exceeds scatter band 3. The hereby work presents a proposal for Zenner and Lius criterion modification based upon introduction of loading non-proportionality measure with minimum circumscribed ellipse method (MCE).

scholarly journals Fatigue Behaviors of Resistance Spot Welds for 980 MPa Grade TRIP Steel

Metals ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 1086
Author(s):  
Heewon Cho ◽  
Sangwoo Nam ◽  
Insung Hwang ◽  
Je Hoon Oh ◽  
Munjin Kang ◽  
...  
Keyword(s):  
Fatigue Life ◽  
Failure Mode ◽  
Trip Steel ◽  
Failure Modes ◽  
Propagation Speed ◽  
Outer Edge ◽  
Fatigue Load ◽  
Resistance Spot ◽  
Fracture Surfaces ◽  
Pull Out

The fatigue life of the resistance spot weld of 980 MPa grade transformation induced plasticity (TRIP) steel was investigated and failure modes and fracture surfaces according to the fatigue load were analyzed. The fatigue life according to the nugget size was observed by using two electrodes with face diameters of 8 mm and 10 mm. When an electrode face diameter with 10 mm was used, the nugget size was large, and the fatigue life was further increased. After the fatigue test, three types of failure modes were observed, namely pull-out, plug, and heat affected zone (HAZ) failure, depending on the fatigue load. The fracture surfaces in each failure mode were analyzed. In all failure modes, a crack was initiated in the HAZ region, which is the interface between the two materials in all failure modes. In the case of pull-out failure, the crack propagates as if it surrounds the nugget at the outer edge of the nugget. In the case of HAZ failure, the crack propagates in the thickness direction of the material and outward in the nugget shell. Plug failure occurs with pull-out failure and HAZ failure mixed. The propagation patterns of cracks were different for each failure mode. The reason why the failure mode and the fracture surface are different according to the fatigue load is that the propagation speed of the fatigue crack is fast when the fatigue load is relatively large and is slow when the fatigue load is low.

Research on the Influence of Tension and Compressive Fatigue Load on the Corrosion Coefficient of Parking on the Ground

2015 ◽  
Vol 741 ◽  
pp. 155-158
Author(s):  
Xiao Hua Yang ◽  
Xue Jun Liu ◽  
Tai Feng Zhang ◽  
Zhi Dong Xin
Keyword(s):  
Fatigue Life ◽  
Normal Distribution ◽  
Fatigue Loading ◽  
Test Sample ◽  
Fatigue Load ◽  
Corrosion Coefficient

To ascertain the grounding corrosion coefficient parking on the ground is the key to evaluate the airframe calendar life. The influence of pull and press load on the grounding corrosion coefficient was evaluated in this paper. The main results are as follows. First, the fatigue life always follows the logarithmic normal distribution after pre-corrosion for pull fatigue loading and press fatigue loading. But the scatter of fatigue life for the wing down-panels is reduced with the fatigue life, and the scatter of fatigue life for the wing up-panels is not changed. The second, the coefficient of the wing up-panels test sample is not changed with the increase of the corrosion calendar life. But, the coefficient of the wing down-panels test sample descends with the increase of the corrosion calendar life.

Fatigue Performance of Concrete with Pre-Cracks in Tension-Compression Cycles

2014 ◽  
Vol 584-586 ◽  
pp. 1054-1061
Author(s):  
Jian Shen ◽  
Xiao Yun Liu ◽  
Lang Wu
Keyword(s):  
Fatigue Life ◽  
Fatigue Strength ◽  
Cyclic Loading ◽  
Fatigue Test ◽  
Stress Ratio ◽  
Fatigue Property ◽  
Fatigue Performance ◽  
Cycle Fatigue ◽  
Fatigue Load ◽  
Compression Cycle

A tension-compression cycle fatigue test was performed in order to study the fatigue property of C50 concrete with pre-cracks in cyclic loading. The stress ratio was-1 and the amplitude was 0.2 MPa ~1.30 MPa. The results show that the modified coefficient of fatigue strength is 0.198~0.265 and the infinite life fatigue strength is below 0.45MPa. While the log value of fatigue life is approximately linear with the amplitude of fatigue load stress, the discreteness of fatigue life, the particularity of concrete, has little to do with the amplitude. The S-N, P-N fatigue life curves and the constant fatigue life diagram of pre-crack concrete are obtained.

scholarly journals A Computer Program for Dynamic Load Simulation of Spur Gears with Asymmetric and Symmetric Teeth

2012 ◽  
Vol 02 (05) ◽  
pp. 239-245
Author(s):  
Fatih Karpat ◽  
Stephen Ekwaro-Osire ◽  
Esin Karpat
Keyword(s):  
Computer Program ◽  
Dynamic Load ◽  
Spur Gears ◽  
Load Simulation

scholarly journals Fatigue Life Characteristics of Segmental Lining Structure for the Shallow Buried Metro Tunnel under the Dynamic Load of a High-Speed Railway

2018 ◽  
Vol 2018 ◽  
pp. 1-13 ◽  
Author(s):  
Wangping Qian ◽  
Taiyue Qi ◽  
Qing Zhao ◽  
Bingrong Pu ◽  
Jin Zhang ◽  
...  
Keyword(s):  
Fatigue Life ◽  
Fatigue Failure ◽  
Dynamic Load ◽  
High Speed ◽  
Dynamic Loads ◽  
High Speed Railway ◽  
Segmental Lining ◽  
Lining Structure ◽  
Metro Tunnel

Shallow buried shield metro tunnels constructed underneath subgrade project of high-speed railways are becoming increasingly common in China, but the lower metro tunnel bears the fatigue effect of dynamic load induced by the upper high-speed railway, so the long-term durability of segmental lining is a nonnegligible problem. The segmental lining structure of metro tunnel is in a state of static-dynamic loads for a long time, especially when a high-speed railway passes above the metro line, and the long-term durability of segmental lining needs further research. Based on theoretical analysis, the effect of different forms of loads on the fatigue life was analyzed, the change law of the static-dynamic loads on segmental lining was summarized, and the method was put forward to evaluate the fatigue life characteristics of segmental lining. The research results reveal that the additional dynamic load is the fundamental reason for the fatigue failure of the structure, and the existence of static load can cause and accelerate the occurrence of structural fatigue failure simultaneously. The results indicate that the fatigue life decreases gradually with the increase of static-dynamic load. Based on coupling analysis of static-dynamic loads of segmental lining, the fatigue life increases first and then decreases with the increase of buried depth of metro tunnel, and it remains unchanged when the depth exceeds a certain value. According to the actual metro tunnel engineering, by using ABAQUS software, a three-dimensional numerical simulation was carried out to analyze the characteristics of the fatigue life and evolution rules of segmental lining. Based on the modified fatigue life formula and metro service life, the optimization design of the buried depth was carried out to determine the most reasonable range of the buried depth. This study provides a valuable reference for safe operation and long-term durability of metro tunnels under high-speed railways.

scholarly journals Flexural Fatigue Performance of Steel Fiber Reinforced Expanded-Shales Lightweight Concrete Superposed Beams with Initial Static-Load Cracks

Materials ◽  
2019 ◽  
Vol 12 (19) ◽  
pp. 3261
Author(s):  
Fulai Qu ◽  
Changyong Li ◽  
Chao Peng ◽  
Xinxin Ding ◽  
Xiaowu Hu ◽  
...  
Keyword(s):  
Fatigue Life ◽  
Static Load ◽  
Steel Fiber ◽  
Lightweight Concrete ◽  
Volume Fraction ◽  
Stress Amplitude ◽  
Flexural Stiffness ◽  
Compression Zone ◽  
Fatigue Load ◽  
Upper Limit

Concerning the structural applications of steel fiber reinforced expanded-shales lightweight concrete (SFRELC), the present study focuses on the flexural fatigue performance of SFRELC superposed beams with initial static-load cracks. Nine SFRELC superposed beams were fabricated with the SFRELC depth varying from 50% to 70% of the whole sectional depth, and the volume fraction of steel fiber ranged from 0.8% to 1.6%. The fatigue load exerted on the beams was a constant amplitude sinusoid with a frequency of 10 Hz and a fatigue characteristic value of 0.10; the upper limit was taken as the load corresponded to the maximum crack width of 0.20 mm at the barycenter of the longitudinal rebars. The results showed that with the increase of SFRELC depth and the volume fraction of steel fiber, the fatigue life of the test beams was prolonged with three altered failure modes due to the crush of conventional concrete in the compression zone and/or the fracture of the tensile rebar; the failure pattern could be more ductile by the prevention of fatigue fracture by the longitudinal tensile rebar when the volume fraction of steel fiber was 1.6% and the reduction of crack growth and concrete strain in the compression zone; the fatigue life of test beams was sensitive to the upper-limit of the fatigue load, a short fatigue life appeared from the higher stress level and larger stress amplitude of the longitudinal rebar due to the higher upper-limit of the fatigue load. The methods for predicting the stress level, the stress amplitude of the longitudinal tensile rebar, and the degenerated flexural stiffness of SFRELC superposed beams with fatigue life are proposed. With the optimal composites of the SFRELC depth ratio and the volume fraction of steel fiber, the controllable failure of reinforced SFRELC superposed beams could be a good prospect with the trend curves of fatigue flexural stiffness.

Analysis on Influence of Effective Turbulence Intensity on Blade Root Fatigue Load of WTGS

2012 ◽  
Vol 538-541 ◽  
pp. 605-609
Author(s):  
Feng Gai ◽  
An Min Cai ◽  
Da Tong Zhang ◽  
Li Xiang Sun
Keyword(s):  
Wind Speed ◽  
Turbulence Intensity ◽  
Theoretical Basis ◽  
Fatigue Load ◽  
Blade Root ◽  
Type Selection ◽  
Air Density ◽  
Damage Theory ◽  
Fatigue Loads ◽  
Cumulative Fatigue Damage

Based on the Palmgren-Miner linear cumulative fatigue damage theory, the blade root fatigue loads in different effective turbulence intensities were calculated and analysed. The results show that when the air density and the wind speed are constant, the blade root fatigue loads increase linearly with the effective turbulence intensity increasing, and the slopes increase linearly with the wind speed increasing. According to these results, the main source of the blade root fatigue loads under different wind conditions can be estimated to provide a theoretical basis for WTGS type selection in the special sites.

The Research on the Effect of the Height of Free Span on Fatigue Life of Submarine Pipeline due to Vortex-Induced Vibration

2016 ◽  
Author(s):  
Jie Dong ◽  
Chen Xuedong ◽  
Bing Wang ◽  
Weihe Guan ◽  
Zhichao Fan ◽  
...  
Keyword(s):  
Fatigue Life ◽  
Lift Coefficient ◽  
Structural Response ◽  
Life Assessment ◽  
Submarine Pipeline ◽  
The Finite Element Method ◽  
Fatigue Load ◽  
Critical Height ◽  
Vortex Induced Vibration ◽  
Fatigue Life Assessment

Free span is a risk of security of submarine pipelines. Fatigue caused by vortex-induced vibration (VIV) is a main failure mode of free spans. The height of free span which influences the VIV fatigue load is an important factor for the fatigue life assessment. In this paper, taking an in-service submarine pipeline as an example, the relation between the height and the fluctuating lift coefficient was firstly investigated by the method of computational fluid dynamics, and the critical height which can neglect its effect on the coefficient was obtained. The VIV structural response of free span with different height and length was analyzed with the finite element method. Furthermore, considering the in-service environment of the submarine pipeline, fatigue life of free span was evaluated numerically with reference to the measured data of flow velocity and its variation with time. Those results provide technical support for the maintenance of free span for the submarine pipeline.

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