Brita Pyttel

Investigation of probable failure position in helical compression springs used in fuel injection system of diesel engines

Helical compression springs are used generally in fuel injection system of diesel engines, where it undergoes cyclic loading for more than 10 8 numbers of cycles. In order to predict probable failure positions in helical compression springs, used in fuel injection system, along the length of the spring at inner side, finite element analyses was carried out, using ABAQUS 6.10. The simulation results show an oscillatory behaviour of stresses along the length at inner side. It was confirmed that the oscillation was due to bending involved with compression. It was also revealed that the bending was due to the geometry of springs. Shear stresses along the length of the spring were found to be asymmetrical and with local maxims at starting of each middle coil. The asymmetry was due to the end coil smaller than 360 degrees. Keywords- Helical compression springs, Maximum shear stress, Finite element analysis

Influence of Frequency and Testing Technique on the Fatigue Behaviour of Quenched and Tempered Steel in the VHCF-Regime

Today in many cases ultrasonic testing machines with a frequency of f ≈ 20 kHz are used for investigations of the fatigue behaviour up to the very high cycle regime (VHCF-regime). A question that arises is if the results of these high frequency fatigue tests are comparable to conventional fatigue tests. This paper compares the fatigue behaviour of a quenched and tempered steel 50CrMo4 in two different tempered conditions investigated at low frequencies (f ≤ 400 Hz) on a servohydraulic testing machine and at a high frequency (f ≈ 20 kHz) on an ultrasonic fatigue testing machine. Effects which can occur because of the different testing techniques and testing frequencies are investigated. A concept is derived to describe the frequency effect caused by the strain rate. The estimations are compared with results of the fatigue tests.

FKM - GUIDELINE FRACTURE MECHANICS PROOF OF STRENGTH FOR ENGINEERING COMPONENTS - PROCEDURES, COMPENDIUMS, EXAMPLES

The German guideline “Fracture Mechanics Proof of Strength for Engineering Components” has been released in 2001 as a result of activities sponsored by the Research Committee on Mechanical Engineering (FKM), task group “Component Strength”. The guideline compiles basics for the integrity assessment of cracked components subjected to static or cyclic loading and provides a step-by-step computational procedure for the use in engineering practice. The paper gives an overview of the guideline, describes its specific features, contents and some new topics included in the last 3rd edition (2006).Copyright

FKM Guideline “Fracture Mechanics Proof of Strength for Engineering Components” — Overview and Extension Topics

The German guideline “Fracture Mechanics Proof of Strength for Engineering Components” has been released in 2001 as a result of activities sponsored by the Research Committee on Mechanical Engineering (FKM), task group “Component Strength”. The guideline describes basics for the integrity assessment of cracked components subjected to static or cyclic loading and provides a step-by-step computational procedure for the use in engineering practice. The guideline was formulated based on a number of national and international reference documents, in particular SINTAP, R6, BS 7910 and DVS-2401, recent research results and some own key aspects. Since 2004 it is also available in English. The procedures and solutions of the guideline are implemented in the computer program FracSafe. The latest 3rd edition of the guideline (2005) includes several new topics. These allow for the consideration of special effects at cyclic loading, mixed mode loading, dynamic (impact) loading, stress corrosion cracking, probabilistic aspects in fracture mechanics calculations. In addition, the compendium of the stress intensity factor and limit load solutions is extended and adjusted according to the state-of-the-art. Some new examples and case studies are included to demonstrate the application of the procedure to engineering problems. This paper gives an overview of the guideline and describes new features available since its 1st edition.

Anhang E: Diagramme und Tabellen

Im British Standard 7910 [16] werden folgende Kennwerte fur die Fehlerbewertung in metallischen geschweisten sowie nicht geschweisten Bauteilen angegeben.