Fatigue Strength Of Crankshafts Research Articles

Failure Analysis of a Diesel Engine Crankshaft based on Finite Element Modeling

The crankshaft is one of the essential components of an internal combustion engine that converts the piston's linear motion into the crank's rotary motion. This research has been carried out to study the failure analysis of diesel engine crankshafts, and forged steel material is selected. A crankshaft's geometry is relatively complex compared to other parts; its working conditions are critical, and the stress concentration areas are very complicated. While considering all these phenomena, it is significant that a crankshaft's fatigue strength, stiffness, durability, and wear resistance should be checked and analyzed properly. Firstly, a 3D model of the crankshaft is designed using SolidWorks 2022 software. After that, the Model is imported to ANSYS software 2022 R2 student version. However, using ANSYS (finite element method) is carried out on the crankshaft’s Model. This research aims to obtain the variation in stress magnitude at critical locations of the crankshaft by applying variable loads and boundary conditions. Simulation techniques were conducted for both static and dynamic analysis. The total deformation observed at the critical area of the crank pin is 1.3488e-8. The corresponding equivalent stress is 318.37, and the crankshaft's safety factor is 15.

船舶用ディーゼル機関向けクランク軸の高設計疲労強度化に向けた取り組み

船舶用ディーゼル機関向けクランク軸の高設計疲労強度化に向けた取り組み

Fatigue strength analysis of crankshaft based on RULES FOR CLASSIFICATION OF SEA-GOING STEEL SHIPS

Based on the force analysis of a high strength marine diesel engine crankshaft in one cycle, the crankshaft fatigue strength checking method of Classification Society was used to check the crankshaft. It can be known that the empirical formula method is more conservative according to comparing the acceptability factor which are calculated by empirical formula method and finite element method. The nominal alternating torsional stress is determined by the inverse method of crankshaft fatigue strength checking method, which is the criterion of fatigue strength of the crankshaft. The fatigue strength of crankshaft can be improved by increasing fillet radius, web thickness or web width.

Determination of the fatigue behavior of mechanical components through infrared thermography

The determination of the fatigue behavior at a component level usually requires dedicated test rigs and an expressive amount of time. The hours spent on such machinery are expensive; therefore, solutions to reduce experimentation time are most welcomed. In this context, this investigation aims at developing a procedure for rapid determination of the fatigue strength of crankshafts by means of a thermographic methodology. The use of infrared cameras for fatigue strength analysis was first assessed in standard dog-bone specimens. Crankshafts were then tested in an in-house fatigue test rig using the conventional staircase method and the thermographic method. Sample batches with different manufacturing parameters were produced and tested to assess the robustness of the proposed alternative technique. Results of the dog-bone test campaign revealed a good correlation between fatigue strength estimates obtained with the conventional Wöhler curve and the thermographic methodology. Finally, the thermographic technique also delivered results in close agreement with the staircase method for all crankshaft batches. The proposed procedure was found to be a viable, rapid alternative to conventional fatigue test programs, with potential application for complex structural components such as crankshafts, among others.

Fatigue Strength Detection Method for Crankshaft of Vehicle Internal Combustion Engine Based on Dynamics

To accurately determine the load boundary conditions required for the finite element calculation of crankshaft fatigue strength, a dynamic-based fatigue strength detection method for the crankshaft of the automotive internal combustion engine is proposed. Taking a certain type of automotive internal combustion engine as the research object, the multi-body system dynamics model of crank-connecting rod mechanism is established and the dynamic load spectrum of a crankshaft in a working cycle of the internal combustion engine is obtained through dynamic simulation analysis. The load boundary conditions of crankshaft finite element analysis are obtained and the finite element model which can simulate the contact state between crankshaft and bearing is established. The crankshaft fatigue strength is based on the dynamic load spectrum. Degree detection provides load boundary, the fillet sub-model is constructed and the stress distribution of the fillet sub-model under 12-unit displacement loads is obtained by calculating the stress field. The working fatigue safety factor of the crankshaft under dynamic stress is calculated. The analysis results show that the detection error of the proposed method is less than 5% under different noise intensities and the average energy consumption is lower than that of the comparative detection methods, which are 251.37 J and 617.37 J respectively and shows that the proposed method has strong anti-interference and low energy consumption.

Assessment of Bending Fatigue Strength of Crankshaft Sections with Consideration of Quenching Residual Stress

High-cycle bending fatigue is the primary failure mode of crankshafts in engines. Compressive residual stresses are often introduced by induction quenching to improve the fatigue strength of crankshafts. The residual stresses, which are commonly obtained by numerical methods, such as the finite element method (FEM), should be included in fatigue failure analysis to predict the fatigue strength of crankshafts accurately. In this study, the simulation method and theory of quenching process are presented and applied to investigate the residual stresses of a diesel engine crankshaft. The coupling calculation of temperature, microstructure, and stress fields of the crankshaft section is conducted by FEM. Then, the fatigue strength of the crankshaft section is analytically assessed by Susmel and Lazzarin’s criterion based on the critical plane approach that superimposes the residual stresses onto the bending stresses. The resonant bending fatigue tests of the crankshaft sections are conducted, and the tests and analytical assessments yield consistent results.

Dynamic Crankshaft Strength Calculation of Diesel Engine Using Simulation Techniques

Crankshaft is one of the most important parts in diesel engine. The fatigue failure and fracture of crankshaft may lead to damage to the other parts, even some accidents. Recently with the increasing requirement of engine power and engine reliability, the investigation of the crankshaft strength becomes more important. Since during the engine work process, the extremely complicated force are loaded on the crankshaft and different vibration caused by torque, bending, etc., the crankshaft may create the resonance and appended dynamic stress in the working frequency range, which will be easy to bring about the bending and torsion damage after short work period. In this paper, the traditional algorithm on the basis of MATLAB/SIMULINK software is used to carry out the dynamic calculation and analysis for a certain type of diesel engine crankshaft. The crankshaft stress state and its variation are analyzed, and the results of the bending moment, torsion versus crank angle are obtained. Finally, the fatigue strength of crankshaft is checked and the safety factor is calculated to verify the crankshaft reliability.

Crankshaft Fatigue Test and Statistical Distribution of Fatigue Experimental Data

This study has finished the crankshaft fatigue strength test by the rational experimental method. And based on the experimental data, the statistical regression analysis of eight commonly used hypothesis distributions, namely Weibull (two-and three-parameter), normal, lognormal, extreme minimum value, extreme maximum value, and exponential (one-and two-parameter), are developed. Then the degree of fitting effect between the experimental data with the eight statistical distributions is evaluated. The result shows that six kinds of statistical distributions, including Weibull (two-and three-parameter), normal, lognormal, extreme minimum value, extreme maximum value, have good fitting effect. In all distributions, the best one is three-parameter Weibull distribution.

The Research on Fatigue of Crankshaft with the Method of Explicit Dynamic

The crankshaft fillet rolling process is one of the commonly adopted methods in engineering to improve fatigue life of the crankshaft. The crankshaft fillet rolling process was simulated based on the explicit dynamic calculation in this paper. After the data acquisition program was compiled, the distribution of the crankshaft surface stress could be obtained. Coupling calculation between the operating stress at different bending moments and the rolling residual stress was based on the Smith-Watson-Topper (SWT) modle. After the simulation on the crankshaft fillet rolling process was carried out, which was based on optimization rolling parameters, the crankshaft fatigue strength was improved by 8.6%.

The Research on Regularity of Residual Stress Distribution of Engine Crankshaft Fillet Rolling

The paper sets up the Finite Element Model on the basis of crankshaft fillet rolling experiment and its mechanism. And then the paper shows the distribution of the residual stress in different depths of rolled crankshaft fillet through numerical simulation. It is found that the fatigue strength can greatly be produced by the method of the engine crankshaft fillet rolling in most of fillet areas; Simultaneously, two strips of tensile stress which is related to reduce the crankshaft fatigue strength will be generated in the peripheries. The tensile stress strips only emerge in the surface layer of the fillet, and then mainly disappear in the depths of 0.4mm below the surface layer. The paper concludes that the main reason of strips of tensile stress lies on the transition between the deformed region and the non-deformed reformed region after trolley wheel pressure is imposed on through a further research.

Analysis of Surface Rolling Process Impact on Crankshaft Fatigue Strength

In this paper, the fatigue comparative test includes two groups of crankshafts, one group with surface rolling process and the other not, has been finished. And the test results are analyzed. The parent standard deviation test shows that there is not effect of surface rolling process impact on the uniformity of crankshaft fatigue strength. But it is sure that there is the impact of surface rolling process impact on the average of crankshaft fatigue strength by the average maternal test. So the surface rolling process can be used to improve crankshaft fatigue strength.

FEM Analysis of Engine Crankshaft Static and Dynamic Behaviour Using ANSYS

By means of FEM using ANSYS, this paper set up a three–dimensional model by using Pro/E for model S195 diesel engine’s crankshaft corresponding to practical conditions . The distortion and stress of the crankshaft was investigated . The fatigue strength of crankshaft was verified under changing load . The rationality of crank stress analysis method, which is in current widely used, was discussed . The model analysis was made for the crankshaft , and provide the valuable theory basis for engine design optimizing and improving .

Analysis of Crankshaft Fatigue Strength Based on Integrated Finite Element Model

Aiming at the complex mechanical systems for the prediction of the fatigue limit load requirements, this paper examines the relationship among finite element analysis model and the performance models. And a finite element modeling method for fatigue analysis is proposed. The finite element model can support static, modal, fatigue, and multi-body dynamic response analysis in parallel and collaboration. This method helps improve the fatigue limit load analysis.

Numerical fatigue strength assessment for crankshafts

Experimental assessment of the fatigue strength of crankshafts in large-bore four-stroke diesel engines is very expensive and time-consuming. Available theoretical methods are often based on analytical methods and simplified equivalent stress hypotheses, which can result in conservative designs. There are also limitations in determination of time-dependent stress distribution. In order to overcome these restrictions, the development and implementation of a numerical procedure at MAN Diesel & Turbo SE has been carried out for assessing operational reliability. Due to increasingly demanding performance specifications, this method is playing a crucial role in the design and rating process.

Calculation of Dynamic Stress and Fatigue Strength of Crankshaft with Bush Deformation Included

Dynamic stress and fatigue strength of a crankshaft of diesel engine with four cylinders is studied with consideration of the elastic deformation of bush. Special software ADAMS and ANSYS, assisted by self-designed programs, are adopted to solve the problem. The dynamic pressures of oil film in the bearings are obtained by analysis of dynamics and tribology of the crankshaft-bearing system with consideration of bush deformation. Programming language APDL in ANSYS is adopted to compile program for realizing the force boundary condition, then the dynamic stress on crankshaft journal surfaces is calculated. The fatigue strength of crankshaft is calculated by using damage accumulation theory. It is shown that the minimum thickness of oil film decreases and the maximum pressure of oil film increases to a great extent if the elastic deformation of bush is taken into consideration. The dynamic response and stress of crankshaft vary and the fatigue life of crankshaft decreases by 15.6%.

Residual fatigue strength of 48MnV crankshaft based on safety factor

Residual fatigue strength of 48MnV crankshaft was studied and analyzed based on safety factor. Three different status crankshafts were used to the hop-up tests, which maintain new after 500 h hop-up tests and after 1 000 h hop-up tests. Then, crankshafts were cut into unit cranks. The unit cranks were used to do endurance bending tests to get the residual fatigue strength. Finally, the results were analyzed based on safety factor. The results show that safety factor of crankshaft descends a little with the increase of the running time, and the residual safety factor is still much bigger than the endurable safety factor. Furthermore, after the crankshaft accomplishes a full life cycle, the residual fatigue strength of the crankshaft is enough to remanufacture and fulfill the next life cycle.

Procedure and results of investigation into fatigue strength characteristics of motorcycle engine crankshafts

We present a procedure of studying the fatigue strength of crankshafts of a two-cylinder motorcycle engine. The use of a unique loading scheme provided obtaining patterns of in-service fracture of the tested crankshafts. The results of comparative fatigue tests of some series of crankshafts of various design and technological versions, namely, nonhardened crankshafts with a fillet and hardened and nonhardened crankshafts without a fillet (zero fillet) are given and analyzed.

Uncertainties of experimental crankshaft fatigue strength assessment

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. In some instances, the test results showed that some engines with a safety factor below 1.0 do not crack and fail during engine dynamometer tests, which implies that the testing method and the safety factor may be overly conservative. What factors are built into the conservative output? What is the right way of conducting this type of component bending fatigue test? What is the acceptable bogey based on the current testing method or the "right" method? This paper describes the laboratory procedures for crankshaft load acquisition and fatigue strength evaluation. Moreover, this paper documents the authors' studies and thoughts on the factors that may contribute to the conservative safety factor. The factors to be addressed are the risk associated with the safety factor chosen, the ray-projected test method, the failure criterion, and definition of the fatigue limit.

Comparison between the strength of steel and cast iron crankshafts in large-scale routine fatigue bending tests

1. We have developed and verified under fatigue-test conditions a constructionally simple and technological efficient model of a crankshaft, manufactured from circular cylindrical blanks by simple machining. 2. The bending fatigue strength of crankshafts with SPD-strengthened hollow chamfers of small radius (r:d=0.02) equals that of crankshafts with chamfers of large radius (r:d≥0.040–0.09). 3. The high efficiency of the technological process for strengthening chamfers of small radii by SPD is confirmed by a statistical analysis of the results of fatigue tests at a reliability level of 95%. 4. The efficiency of the SPD strengthening of small-radius chamfers will in 95 cases out of 100 lie in the range 272–346 and 240–309% for steel 45 and HTI crankshafts respectively. 5. The strength procedures and the geometry of the chamfers before and after strengthening here assumed ensure a very efficient strengthening process, i.e., stress concentrations in the chamfer junction are almost completely eliminated. 6. Engine crankshafts may be designed with small-radius chamfers (r:d=0.02) instead of those with large radii (r:d≥0.04–0.09) recommended in the corresponding engineering standards; this allows the support surface of the pivots to be increased by up to 8%, so reducing the wear on the shaft pivots and bearings, i.e., increasing the life of the engines.

Closure to “Discussions of ‘Influence of Geometrical Design Factors on the Bending Fatigue Strength of Crankshafts’” (1963, ASME J. Eng. Power, 85, pp. 179–181)

Closure to “Discussions of ‘Influence of Geometrical Design Factors on the Bending Fatigue Strength of Crankshafts’” (1963, ASME J. Eng. Power, 85, pp. 179–181)