Considering bearing failure of crank and assuming empirical relations. Optimizing the design of connecting rod under static and. Fatigue behavior and life predictions of forged steel and. Fatigue life was defined as the sum of crack initiation and crack growth lives, with crack growth life obtained using fracture mechanics. The service stresses were simulated by pushing the pin against the connecting rod. It is a very different case when fluctuating loads are applied, such as those in a hydraulic cylinder or in an automotive connecting rod.
A comparison between different failure criteria in crankshaft showed that using surface crack initiation criterion compared to resonant shift or two pieces failure criterion decreased the apparent fatigue limit 10. Original research article fatigue and structural analysis. More considerations design is another important element in producing a quality fastener. The connecting rod is the intermediate member between the piston and the crankshaft. While investigating a connecting rod failure that led to a disastrous failure of an engine, rabb 1996 performed a. The occurrence of an abnormal load in operation and the presence of a thick. Check for parallelism between the large and small ends of rod.
Fatigue on engine pistons a compendium of case studies. If the engine is operating, connecting rod fails, this could cause a critical situation. The occurrence of an abnormal load in operation and the presence of a thick decarburization layer on the external surface of the rodbody are, respectively, responsible for the fatigue failure of the two connectingrods. A failure analysis investigation of a connecting rod was conducted. If this pin snaps the connecting rod is no longer connected to the engine. Fatigue on engine pistons a compendium of case studies f. Heads must be designed with proper bearing area, correct upset and controlled fillet radius. Together with the crank, the connecting rod converts the reciprocating motion of the piston into the rotation of the crankshaft. Visual and scanning electron microscopy observations show that a lot of axial grooves appear on the internal surface close to the fracture and the fatigue cracks initiated from the axial grooves.
Root cause failure analysis understanding mechanical. Due to cyclic loading and presence of stress concentrations at the critical areas, fatigue becomes the primary cause of failure of connecting rods. Causes of failure with a connecting rod it still runs. The difficulties in making a sufficiently good fe model with exact geometry of fine details and with all important nonlinearities are explained. The origin of the fracture was located at the conrod lubrication channel. Socket depth and drive lengths must conform to dimensional requirements in order. Section v illustrates and compares the results with existing design i. Failure analysis of a diesel engine connecting rod. Based on these assumptions the manufacturing processes effects have a tremendous influence on the fatigue life of connecting rod. Service loads and failures experienced by connecting rods. Crack in the connecting rod due to excessive fatigue, causes uneven distribution of the stress over growth mechanism, there are various reasons for that. It is caused by running the bearing at load above the fatigue limit.
Fatigue limit of an overlay is determined by the strength of the material and the thickness of the overlay. Yield, fatigue and buckling characteristics are often used as evaluation indexes for the performance of engine connecting rods in mass reduction design to optimize vibration. Fatigue fracture examples shigleys mechanical engineering design fatigue failure of a 200mm diameter piston rod of an alloy steel steam hammer. This is why the connecting rod is the most stressed part of an engine system. Fatigue analysis of connecting rod using finite element. In general, the failure occurs at the big end of connecting rod. A schematic of connecting rod geometry is shown in figure 1. Mae 322 machine design lecture 5 fatigue mercer university. The major type of engine bearing failure is material fatigue. Fatigue behavior and life predictions of forged steel and powder metal connecting rods adila afzal submitted as partial fulfillment of the requirements for the master of science in mechanical engineering the university of toledo may 2004 this study investigates and compares fatigue behavior of forged steel and powder metal connecting rods.
Analysis and optimization of connecting rod used in heavy. The symptoms associated with valve problems include the following. Finite element analysis of the fatigue life for the. The focus of fatigue in ansys is to provide useful information to the design engineer when fatigue failure may be a concern. Fatigue fracture examples shigleys mechanical engineering design fatigue failure of a 200mm diameter piston rod of an alloy steel steam hammer loaded axially crack initiated at a forging flake internal to the part internal crack grew outward symmetrically fig. One important technical issue is whether the residual fatigue life of products meeting the needs of its next life cycle. It is estimated that 5090% of structural failure is due to fatigue. Fatigue failure of a connecting rod, engineering failure. It is a part of the engine, which is subjected to millions of repetitive cyclic loadings. The thinner the overlay the higher its fatigue strength. The first picture is a digital photo of such a failure with the bolt still in the rod.
Existing connecting rod is manufactured by using carbon steel. Fatigue and structural analysis of connecting rods material due to c. A connecting rod works in variably complicated conditions, and is subjected to not only the pressure due to the connecting rod. This study analyzes the failure mechanism of the connecting rod, establishes its three dimensional model, uses dynamic simulation software adams to calculate its timeload spectrum of the connecting rod. Wbased material acted as nucleation site for cracks that propagated by.
Fatigue analysis of connecting rod of samand engine by finite. A connecting rod, also called a con rod, is the part of a piston engine which connects the piston to the crankshaft. Its primary function is to transmit the push and pull from the piston pin to the crank pin, thus converting the reciprocating motion of the piston into rotary motion of the crank. Yield, fatigue and buckling characteristics are often used as evaluation indexes for the performance of engine connecting rods in mass reduction design to. Engine bearing failure analysis guide edge wear due to distorted connecting rod imperfect journal geometry cavitation erosion spinning of the bearing in the housing. Pdf fatigue fracture of truck diesel engine connectingrods. The connecting rod is required to transmit the compressive and tensile forces from the piston, and rotate at both ends. Journal of asian scientific research failure analysis of a.
Fatigue failure of a connecting rod fatigue failure of a connecting rod rabb, roger 19960301 00. The function of connecting rod is to translate the transverse motion to rotational motion. Select a bearing material with higher load capacity check. Check main bearing bores for alignment, taper, roundness and size. Connecting rod materials must have good fatigue and shock resistances. A connecting rod works in variably complicated conditions, and is subjected to not only the pressure due to the connecting rod mechanism, but also due to the inertia forces. Fatigue is the dominant failure mode of the two connectingrods. It is estimated that 90% of all fastener failures in motorsports are fatigue related.
Pdf design, buckling and fatigue failure analysis of connecting. Therefore, the connecting rod should be able to withstand tremendous load and transmit a great deal of power smoothly. Its behavior is affected by the fatigue phenomenon due to the reversible cyclic loadings. Many connecting rod bolt failures are caused by insufficient preload. Design and analysis of connecting rod using forged steel. In this paper, two case studies regarding the failure of truck diesel engine connectingrods are presented. Parkash and vikas gupta and vinod kumar mittal, year20. Failures of engine bearings and their prevention substech. Fatigue in engine connecting rod bolt due to forming laps article pdf available in engineering failure analysis 165. Pdf fatigue in engine connecting rod bolt due to forming.
Pdf design, buckling and fatigue failure analysis of. Probabilistic analysis for resolving fatigue failures of. Contact elements were placed between the rod and the pin. A failure investigation has been conducted on a diesel engine connecting rod. When the repetitive stresses are developed in the connecting rod it leads to fatigue phenomenon which can cause dangerous ruptures. This paper describes the analysis of a fatigue failure of a connecting rod in a mediumspeed diesel engine. Fatigue fracture of truck diesel engine connectingrods.
These fluctuating loads are called fatigue loads, and when the fatigue strength is exceeded, a crack can develop. If the reliability is not strong enough, fatigue failure of the cr would occur, thereby leading to component fracture and engine failure. With fatigue analysis we can determine the lifetime of the connecting rod. Pdf failure of any component in a vehicle, even a small part, may result in an out of control vehicle and possible catastrophic accident. For assessment of a crankshaft fatigue life, one has to determine the stress state first. Failure analysis of a diesel generator connecting rod. Stress analysis of connecting rod for weight reduction a. A parametric 3d finite element model of the connecting rod with a hollow wrist pin was developed to study the fatigue stress. When a fastener is insufficiently preloaded during installation the dynamic load may exceed the clamping load resulting in cyclic tensile stress and eventual failure.
The case encircling the rod body diameter carries the load for this high tensile strength sucker rod and if you penetrate the case, you effectively destroy the loadcarrying capability of this type of manufactured sucker rod. If load acting to the bearing is higher than the fatigue strength of the material, fatigue cracks form on the bearing surface, spread towards the back layer and may result in peeling off the bearing material. The fracture occurred at the small head of the connecting rod. Design and analysis of connecting rod using forged steel leela krishna vegi1, venu gopal vegi2. When the repetitive stresses are developed in the connecting rod it leads to fatigue phenomenon which can cause dangerous ruptures and damage. They reported that the factors which affect fatigue strength in. Design of connecting rod for weight reduction using c70s6. Its behavior is affected by the fatigue phenomenon due to the reversible. Failure of any component in a vehicle, even a small part, may result in an out of control vehicle and possible catastrophic accident. Fatigue as well as static stresses are mainly responsible for failure of a connecting rod. Every stroke in the engine is need to have to its nearby components to cyclic loading that push and pulls the crankshaft and connecting rod. For some engines this results in catastrophic engine failurethe connecting rod goes through the engine block or the crankshaft is bentbut for some engines it just causes a dramatic loss of power.
The proposed design explores weight reduction opportunities for a production forged steel connecting rod. When the repetitive stresses are developed in the connecting rod it leads to. Design of connecting rod for weight reduction using. Design, buckling and fatigue failure analysis of connecting rod. Fatigue of an overlay appears in form of a network of thin cracks. As per the graph shown above for small end failure, considering fos as 2, the life ranging from 0. Fatigue analysis of connecting rod using finite element analysis 789 the stress at any point on the connecting rod at this axial load can be interpolated from the axial stress analysis results. Fatigue tests of the material in the connecting rod were also carried out. Finally the paper is concluded and recommendations are proposed in section vi. Check all connecting rod housing bores for taper, roundness and size, using a bore gauge or inside micrometer.
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