Engine Valve Springs Research Articles

Influence of the surface flaws in oil-tempered wires on the fatigue life of automotive engine valve springs

The purpose of this study is to evaluate the fatigue life of an automotive engine valve spring when the micro defect is applied to a 2300 MPa-class oil-tempered wire (OT wire) with 2.5 mm of diameter as the critical flaw depth. First, the deformation of the surface flaws in the OT wire during the valve spring manufacturing processes was derived via FE analysis using the sub-modeling technique, and the residual stress of the final spring was measured and applied to the spring stress analysis model. Second, the strength of the valve spring was analyzed to examine the presence of residual stress and compare the applied stress levels by the surface flaw. Third, the influence of micro defects on the fatigue life of the spring was evaluated by applying the stress on the surface flaw derived through the spring strength analysis to the S–N curve derived through a rotary bending fatigue test with the OT wire. The flaw depth of 40 µm, which is the existing criterion for surface flaw management, does not reduce the fatigue life.

Multi-Objective Optimization of Internal Combustion Engine Valve Springs Based on NSGA-II

The design of engine valve spring generally belongs to multi-objective optimum design. The traditional trying means and the graphical methods are difficult to solve the multi-objective optimization problem, and the traditional multi-objective algorithms have certain defects. The elitist non-dominated sorting genetic algorithm (NSGA-II) is an excellent multi-objective algorithm, which is widely used to solve problems of multi-objective optimization. This method can improve the design quality and efficiency, and it has much more engineering practical value.

Immune Optimization Design of Diesel Engine Valve Spring Based on the Artificial Fish Swarm

In order to improve the reliability of the structure design of the diesel engine valve spring and its working performance, an artificial fish swarm-based immune genetic algorithm (AFS-IGA) is proposed. After the mutation operation of the immune genetic algorithm (IGA), the train operator and foraging operator of the artificial fish algorithm are added to improve the convergence speed and strengthen the optimal performance of the basic immune genetic algorithm. Compared with genetic algorithm (GA) and the IGA, the function testing results show that the convergence speed of the AFS-IGA is faster, the optimization ability of the AFS-IGA is stronger, and the optimization precision is higher. Furthermore, the optimization design results of the diesel engine valve spring show that the optimization performance of the proposed algorithm is optimal, which verifies the robustness of the AFS-IGA.

Natural Frequency Study of Automotive Engine Valve Spring by Experimental Method

This paper presents a frequency response function method to measure the natural frequency of automotive engine valve springs with respect to different spring height. A new apparatus is developed for changing the spring height within the range of valve lift. The test results indicate that the natural frequency changing highly depends on the different pitch type of the spring. The measured natural frequencies of valve spring can be direct applied to the estimation of valve spring surge characteristics.

Effects of end coils on the natural frequency of automotive engine valve springs

In this paper, we present a method for estimating the natural frequencies of various engine valve springs such as constant pitch, two-step variable pitch, three-step variable pitch, and progressive springs. Since a valve spring’s surging amplitude is magnified when the spring’s natural frequency coincides with the frequency of the cam profile harmonic components, estimating the natural frequency of the spring is the first step in predicting valve spring surging phenomena. A new method for calculating the valve spring’s natural frequency is proposed in this paper that considers the end coil effect. This method predicts not only the natural frequency of a helical spring at a fixed number of active turns, but also the change in the natural frequency as the spring is compressed. The experimental results demonstrate that nonlinear characteristics of engine valve springs can be predicted from the given initial pitch curves.

Analyzing Field Failures of Engine Valve Springs in Presence of Non Metallic Inclusions by Applying Statistical and Fracture Mechanics Models

An Engine valve spring, which is made of high strength, clean steel, is a very important component in an engine for controlling the movement of exhaust and the intake valve. It is designed to survive an infinite life under high cyclic stress. Hence, the reliability of engine valve spring is a very important issue from the warranty point of view. The relationship between the stresses applied on the valve spring during operation of an engine and the number of cycles (S-N) curve, is strongly influenced by the presence of inclusions which are microscopic particles of extraneous material within the metal matrix. This implies that the fatigue strength of the material will experience a drop and shift in the endurance and consequently a decrease in the Reliability level of the valve spring. Field and experimental data of engine valve springs failed due to inclusions will be utilized for predicting the fatigue strength of valve spring material by applying extreme value statistics and fracture mechanics models.Copyright © 2009 by ASME

Effect of Chemical Composition to <I>φ</I> splitting in 2<I>θ</I>-sin<I>φ</I><sup>2</sup> Diagram on Residual Stress Measurement of Shot Peening material

High durability is required for automotive engine valve springs. To ensure the performance of springs, it is necessary to evaluate and measure the residual stress distribution on surface and inner direction of the spring. Theoretically, it is used to be treated that the residual stress of a shot-peened material surface is uniform. However, the shape of a coil spring causes various peening angles corresponding to the surface location, so the uneven shot peening angles may leads to a non-uniform residual stress on the coil spring surface. On the other hand, an analysis method of non-liner 2θ-sin2 φdiagram (or φ-splitting analysis) is well known to directionally deformed material such as ground, planed or rolled materials. Recently, an φ-splitting analysis has been reported for the shot-peened materials. In this study, the residual stress distribution of slant shot-peened spring material was measured and, φ-splitting (non-linear 2θ-sin2 φdiagram) was studied in the view of chemical compositions and microstructures. As a results, the extent of φ-splitting was mainly affected by the distribution of carbide particles, not the kind of carbide particles itself.

Influence of Work Condition and Microstructure on the Directionally Deformed Surface by Shot Peening

High durability is required for automotive engine valve springs. To ensure the performance of spring, it is necessary to evaluate and measure the residual stress distribution of spring surface and inward direction. Generally, it has been assumed that the residual stress of a material surface treated by the shot peening is uniform. However, the round and spiral shape of a coil spring brings various peening angles corresponding to the surface location, then the uneven peening angles may leads to a non-uniform residual stress on the coil spring surface. In the meanwhile, an analysis method of non-liner sin2 φ diagram, or φ-split analysis, is well known to directionally deformed material. In this study, residual stress distribution of spring material deformed by the shot peening from the different angles was measured and, non-linearity of sin2 φ diagram was studied. In addition, the relationship between microstructure and residual stress was studied by using field emission type scanning electron microscope (FE-SEM). The result reveals that the non-linearity in the sin2 φ diagram for the shot peening samples. The extent of φ-split became larger with the increasing shot peening angle and was dependent not only on the mass fraction of carbide particles but also on the carbide particles size distribution.

408 自動車用弁ばねの動的強度に関する特性

Role of engine valve spring is to rightly turn intake air and exhaust valve for engine for automobile in cam profile way on and off. Surging phenomenon of valve spring becomes a problem with speedup of the engine as jump of valve and cause of bounce. However, analysis case is little for the dynamic behavior, since it is complicated. In this study, the model which measured the actual valve spring is used. It is recognized that the form of the seat end of the spring changes the stress state in a valve spring. Static, dynamic behavior and stress state of valve spring are examined using the finite element method.

Development and introduction of wire for engine valve springs in VAZ

Valve springs (inner and outer) are critical parts of a car and therefore should meet stringent requirements with respect to their endurance and elastic properties. Results of work on introducing wire for valve springs of steel 70KhFA-Sh instead of Oteva-60 (68CrV2) are described.

The Fatigue Fracture Progress of Valve Springs

By using new technique which enables us to measure the depth of initial fatigue cracks in springs, the mechanism of fatigue on engine valve springs was made clear:(1) The initial cracks on non-electropolished springs start from the surface of wire. By contraries, on electropolished springs, they start from inside of wire.(2) On non-electropolished spring, the depth of initial cracks has certain critical values, which probably depend on applied stress.(3) When the initial crack on non-electropolished springs reaches the critical depth, failure occurs suddenly. On the other hands, when the initial crack on electropolished springs comes to surface, sudden failure takes place.

Development of electropolished steel wires with high fatigue strength for engine valve springs

Development of electropolished steel wires with high fatigue strength for engine valve springs

Optimal Design of Resonance Suppression Helical Springs

Based on a previously developed and verified helical spring dynamic model, optimization and FFT subroutines have been added to the spring dynamic model as controlling and postprocessing units to form a computer-based optimal design tool. The objective function minimized is the amplitude of spring resonance. Design variables are the coefficients of a polynomial which describes the variation of the diameter of the spring wire along the spring helix. Constraints are the maximum fatigue stress at any location of the spring wire, the minimum and maximum wire diameter, and the maximum required spring force. In a case study for an automobile engine valve spring, resonant harmonic power has been reduced by 47 percent, given the newly designed spring a potential to be used at 8.3 percent higher engine speed before potential valve toss occurs.

VALVE‐SPRING MATERIALS AND DESIGN

The function of an internal combustion engine valve spring is to provide sufficient force throughout the engine cycle to maintain the tappet in contact with the cam at all speeds within the engine speed range. However, it must not exert such force that will produce unacceptable contact stresses between tappet and cam. The performance requirements of a valve spring are that it must not fail by fracture or, by load relaxation, lose so much of its controlling force that it fails to maintain control between tappet and cam.

An Experiment on Surging of Engine Valve Spring

An Experiment on Surging of Engine Valve Spring