Spring Failure Research Articles

The Study of Premature Failure of Springs Used In Railway Coaches

The springs used in the bogie suspension of railway coaches are compression springs. They are made of an elastic wire material formed into the shape of a helix. They are commonly referred to as a coil spring or a helical spring. They are used to store energy and subsequently release it to absorb shock or to maintain a force between contact surfaces. The spring returns to its natural length or position when unloaded. Springs used in railway coaches have been failing prematurely much before their intended service life. The springs are made with quality materials. Before being put to service, the springs are tested with extensive Non Destructive Testing Methods which are approved by ISO standards to make sure that quality parts are used. However the springs still fail before their service life ends.

Failure Analysis on Spring of Boiler Drum Safety Valve

Safety valve is an important component of a boiler. The failure of its spring will bring hidden trouble to the boiler operation. The fracture failure of a drum safety valve spring of a power plant boiler was discussed based on chemical composition analysis, hardness test, metallurgical microstructure observation and SEM. Results showed that improper material selection and improper heat treatment process which led to temper brittleness contributes to the fracture. In addition, oxygen corrosion pit on the surface of the spring play an important role in promoting the cracking.

Analysis of a sliding mechanism using spiral springs in mobile products

Spiral springs are widely used in sliding mechanisms because they can store a large amount of elastic energy within a limited space. In mobile products, spiral springs behave in a non-linear fashion. Due to the lack of appropriate analysis methods, spiral springs are currently designed based on experience. Unfortunately, spiral springs can become damaged within a warranty period, indicating that the design strategy needs improvement. Existing analysis methods are limited by excessive simplification or they do not consider the full range of the sliding mechanism. In an effort to identify the causes of spiral spring failure in sliding mechanisms and to establish design guidelines for spiral springs, we developed a finite element procedure for analyzing full sliding mechanisms. The proposed analysis method was verified by comparing the simulated finite element results with those of actual experiments. The simulation results show that the regions of a spiral spring that experience the maximum stress are the same regions in the spring that become damaged during use. The predicted reaction force curves of a spiral spring experienced during operation resemble those measured experimentally. The proposed analysis method is useful for designing spiral springs, with particular consideration for the initial angle of a spiral spring in the sliding mechanism and the cross-sectional thickness and width of the spring itself. The modeling and analysis method used to mimic the spiral spring-based sliding mechanism permits the design of thinner sliding mechanisms with thinner spiral springs. This design may be suitable for use in mobile products.

Failure analysis of PSV spring in off shore gas production pipeline

Pressure safety valves (PSVs) are often used to protect pipes, valves and pressure vessels in industrial plants. In off shore oil and gas production and storing platforms these equipments are subjected to aggressive environmental conditions. High chloride atmosphere and the possibility of H2S contamination are the main concerns about the equipments operation. In this work, the failure of a small spring from a PSV used in gas production line in an off shore platform was investigated. The material was identified as UNS S17700 precipitation hardening stainless steel heat treated to the peak of hardness. The analysis of surface of fracture revealed that the material has failed due an environment assisted cracking, facilitated by the low ductility of the material.

Effects of hypoxia on benthic organisms in Tokyo Bay, Japan: A review

Bottom hypoxia (dissolved oxygen concentration ≤2 ml l(-1)) from anthropogenic eutrophication is a growing global concern. Here, we summarized characteristics of hypoxia and its effects on benthic organisms in Tokyo Bay. Despite recent decreases in nutrient inputs, hypoxia has been increasing in duration and spatial extent, suggesting that the substantial loss of tidal flats from reclamation is contributing to a decrease in the ability of Tokyo Bay to recycle nutrients. Hypoxia develops in the central to northern part of the bay and persists from spring to autumn, causing defaunation of benthic organisms. After the abatement of hypoxia in autumn, the defaunated area is recolonized, either through migration or larval settlement. Some megabenthic species with a spawning peak in spring and summer experience failure of larval settlement, which is probably due to hypoxia. The adverse effects of hypoxia are an impediment to recovery of benthic organisms in Tokyo Bay.

Fatigue performance of discontinuous fibre-reinforced thermoplastic leaf spring

The present work investigates the fatigue performance of fibre-reinforced injection-moulded leaf springs. Twenty per cent discontinuous long, short glass fibre-reinforced polypropylene (SFPP) and unreinforced polypropylene (UFPP) materials are used for manufacturing constant-thickness, varying-width, mono leaf spring. Fatigue tests are performed on moulded leaf springs at various alternating loads under the pulsating compression mode at 0.5Hz frequency with the aid of in-house developed fixtures integrated with the servo-hydraulic fatigue machine. During fatigue testing, cyclic load—deflection of the test leaf spring of each and every cycle is measured; the energy dissipation ratio and spring rate of the test leaf springs are reported as an index for the accumulated damage at various stages of its life. Test leaf springs are subjected to fatigue load up to 2×105 cycles or failure, whichever is earlier. SFPP and UFPP leaf springs exhibited drops in the spring rate, whereas long glass fibre-reinforced polypropylene exhibited fracture as leaf spring failure. Fatigue performance as well as failure morphology of the leaf springs confirmed the role of reinforced fibre length in the thermoplastic composite leaf spring.

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

Design and failure modes of automotive suspension springs

This paper is a discussion about automotive suspension coil springs, their fundamental stress distribution, materials characteristic, manufacturing and common failures. An in depth discussion on the parameters influencing the quality of coil springs is also presented. Following the trend of the auto industry to continuously achieve weight reduction, coil springs are not exempt. A consequence of the weight reduction effort is the need to employ spring materials with significantly larger stresses compared to similar designs decades ago. Utilizing a higher strength of steel possesses both advantages and disadvantages. The advantages include the freedom to design coil springs at higher levels of stress and more complex stresses. Disadvantages of employing materials with higher levels of stress come from the stresses themselves. A coil’s failure to perform its function properly can be more catastrophic than if the coil springs are used in lower stress. As the stress level is increased, material and manufacturing quality becomes more critical. Material cleanliness that was not a major issue decades ago now becomes significant. Decarburization that was not a major issue in the past now becomes essential. To assure that a coil spring serves its design, failure analysis of broken coil springs is valuable both for the short and long term agenda of car manufacturer and parts suppliers. This paper discusses several case studies of suspension spring failures. The failures presented range from the very basic including insufficient load carrying capacity, raw material defects such as excessive inclusion levels, and manufacturing defects such as delayed quench cracking, to failures due to complex stress usage and chemically induced failure. FEA of stress distributions around typical failure initiation sites are also presented.

Overview of factors contributing to steel spring performance and failure

Leaf springs and coil springs are commonly used in the motor vehicle industry. Premature fatigue failure is a common failure mode. However, the reasons for these failures may be more complex and include: design deficiencies, heat treatment, steel alloy chemistry, intergranular cracking, presence of Fe-S inclusions, and grain boundary embrittlement. This paper will provide an overview of spring steel: chemistry, heat treatment, residual stress, fatigue failure, and failure analysis of leaf and coil springs.

Light composite elliptic springs for vehicle suspension

For composites to compete in vehicle suspension applications, it is essential to control their failure by utilising their strength in principal direction instead of shear. This can be achieved efficiently by employing a new configuration instead of existing one. This study marries between an elliptical configuration and the woven roving composites. In this paper, the influence of ellipticity ratio on performance of woven roving wrapped composite elliptical springs has been investigated both experimentally and numerically. A series of experiments was conducted for composite elliptical springs with ellipticity ratios ( a/ b) ranging from one to two. Typical failure histories of their failure mechanism are presented and discussed. In general, this study demonstrated that composites elliptical spring can be used for light and heavy trucks and meet the requirements, together with substantial weight saving. The results showed that the ellipticity ratio significantly influenced the spring rate and failure loads. Composite elliptic spring with ellipticity ratios of a/ b 2.0 displayed the highest spring rate.

Failure analysis of a passenger car coil spring

Investigation on the premature failure of suspension coil spring of a passenger car, which failed within few months after being put into service, has been carried out. Besides visual examination, other experimental techniques used for the investigation were (a) microstructural analysis and fractography by scanning electron microscopy (SEM), (b) inclusion rating by optical microscopy, (c) hardness testing, (d) residual stress measurement by X-Ray diffraction (XRD) and (e) instrumental chemical analysis. Inherent material defect in association with deficient processing led to the failure of the spring.

Failure analysis of the suspension spring of a light duty truck

In this paper the failure of the rear suspension spring is analyzed in detail. The rear axle suspension system of the truck and fractured flat spring is investigated. Fracture surface, mechanical and chemical properties and microstructure of the spring material is analyzed. Forces acting on the spring is determined and strength calculations are carried out. Later, failure behaviour and cause of fracture is revealed after carefully analysis of microstructure and results of calculations. At the end precautions to be taken to prevent a similar failure is recommended.

Evaluation of a leaf spring failure

The determination of the point of failure during an accident sequence of a rear leaf spring in a sport utility vehicle is presented in terms of fracture surface analysis and residual-strength estimates. Marks at the scene of the accident pointed to two possibilities for the point of failure: marks in the roadway at the start of the accident sequence and a rock strike near the end of the sequence. Evidence from rust and chemical contamination on the fracture pointed to the spring having been cracked in half prior to the accident. Extensive woody fracture and secondary cracking at the midplane of the spring was evidence for segregation and weakness in the spring. Stress estimates for the effect of both the weakness and prior cracking on the residual strength of the spring revealed reductions in strength of the spring that could produce fracture at the start of the accident sequence. The point of failure of the spring was placed at the start of the accident sequence.

회전 핀의 종동 하중에 따른 박판 스프링의 대변형에 대한 연구

The mechanical spring is one of widely used machine elements. Among various kinds, flat-type spring loaded by a rotating pin was studied. A flat spring was simplified to a cantilever beam, and numerical analysis was attempted. Since the loading pin rotates about a separate axis from the fixed spring or vice versa, the location, direction, and magnitude of the contact force including normal contact and friction loads vary accordingly. Meanwhile, the spring is deformed substantially as the relative motion progresses. Therefore, this problem needs to be formulated taking the follower loading characteristics and geometrical non-linearity into account. Derived nonlinear differential equation was solved to yield the spring deflection, contact force and the torque to rotate the pin, and the result was compared with a finite element solution. Also, the influences of principal design parameters were studied. The proposed methodology is expected to be useful for the design of pin-loaded flat spring and the prevention of mechanical failures in the form of yielding or fatigue failure of spring or severe wear of the components.

Bifurcation and Chaos Research on Dry Friction System in the Spring Fault Condition

In this paper, the periodic solutions and stability in the dry friction dynamic system are researched by two-dimensional Poincaremap when the fault has happened in the system because of the spring failure. As a result of numerical computation and theoretical analysis, the bifurcation and chaos will arise when the parameters of system are changed. It is very important to analyze the dynamic behavior to conduct fault diagnosis.

Korrosionsschutz für Parabelfedern umweltfreundlich verbessern - Untersuchungen an Prüfblechen und bauteilähnlichen Proben

Failures of parabolic leaf springs for trucks are caused by the effect of corrosion to a considerable portion. In order to minimize those corrosion damages by means of improved corrosion protection, systematical and detailed investigations are necessary taking into account the recent developments of corrosion protection systems. The paper presented here reports on results of an actual research program with the aim to investigate the complex connections in the failure mechanisms of corrosion protection systems on spring steel with high strength under high loading in order to achieve an improved corrosion protection.

Fatigue failure of helical compression spring in coke oven batteries

The failure of a helical compression spring employed in coke oven batteries was analysed. Microstructural analysis and hardness measurements did not show any degradation of the spring material. Surface corrosion product was analysed by XRD and SEM–EDS. Sulphur and chlorine bearing compounds were detected. Macrofractography of the fracture surface revealed beach marks, indicating fatigue as the mode of fracture and surface pits. It was established that the spring failed due to corrosion fatigue.

Premature fatigue failure of a spring due to quench cracks

The premature fatigue failure of a compression spring during service has been analysed. Optical and scanning electron microscopy, hardness and tensile testing and X-ray diffraction techniques were employed. Quench cracks, presumably due to improper quenching, were observed across the cross-section of the spring. It is established theoretically that the diameter of the spring rod was smaller than the critical diameter for this composition of steel. X-ray diffraction showed the presence of a small amount of retained austenite (average grain size of 2 μm).

1535 カルバック識別情報量を用いた設備診断 : 相関関数法との比較

This paper concerns on detection and classification of machinery conditions by the application of patter recognition. In previous paper, the Kullback discrimination information with AR model has been applied to detect the pre-assumed conditions of a compressor, (1) normal, (2) suction filter choking, (3) suction valve spring failure, (4) piston ring wear, (5) suction valve failure and combination of (2)-(5). This method could classify these conditions. In this paper, this method is compared with another similar pattern recognition method, correlation function method, from the point of anti-noise characteristics.

Premature failure of a leaf spring due to improper materials processing

Failure analysis of a leaf spring which failed prematurely during service was carried out using optical and scanning electron microscopy, hardness and tensile testing, and residual stress evaluation by X-ray diffraction. Quench cracks, which are aligned normal to the length of the leaf, have been identified in shot peened and polished surfaces. These cracks have been attributed to an improper quenching process. It is established by theoretical analysis that the leaf thickness is smaller than the critical plate thickness required for this composition of steel, and that leads to an increase in quench severity. It appears that some of these quench cracks have propagated by a fatigue mode which is confirmed by the presence of beach marks on the fractures surface. Observation of intergranular cracking and the presence of FeS inclusions at the prior austenite rain boundaries implies that some sort of grain boundary embrittlement might have facilitated crack growth and led to failure. It has been suggested that quenching should be carried out by recommended procedures guided by the thickness of the component and chemical composition of the steel. Careful inspection of the surface after quenching must also be carried out to maintain quality assurance in order to avoid premature failure.