Characterization of hot forged P285NH steel by metallurgical investigation and reliability analysis

An extensive study was carried out to investigate the effect of cooling rate after hot forging process and normalization step on the hardness, strength and impact toughness and microstructure of P285NH steel. Understanding of the combined effect of cooling rate and normalization on the mechanical and microstructural properties of the steel would help to select conditions required to achieve optimum mechanical properties. The results indicated that the microstructures of all forging and cooling conditions were dominated by ferrite and pearlite phases with different morphologies and grain sizes according to various cooling rates. Conveyor cooling led to a formation of relatively fine acicular ferrite and pearlite grains in comparison to batch cooling which presented coarse polygonal ferrite with pearlite. Based on the data fluctuation of Charpy tests, the normal distribution provided a statistical analysis method for assessing the reliability. Through the statistical analysis of the distribution function, it can be concluded that normalization step is necessary for higher reliability. Both batch cooling and conveyor cooling did not give the required reliability level for safety components due to heterogeneities in the microstructure.     

Numerical and analytical calculation of the orthotropic heat transfer properties of fibre reinforced materials

This paper is on the investigation of the orthotropic heat transfer properties of unidirectional fibre reinforced materials. The orthotropic effective thermal conductivity of such composite materials is investigated based on two different approaches: the finite element method as a representative for numerical approximation methods and an analytical method for homogenised models based on the solution of the respective boundary value problem. It is found that fibre reinforced composites possess strong orthotropic heat transfer properties, which are getting more distinctive with increasing deviation of the thermal conductivities of matrix and reinforcements. Furthermore, the effect of small perturbations of the periodic configuration of fibres in the matrix on the thermal conductivity is investigated.     

Konstruktive Gestaltung der Gewindetragfähigkeit bei leichten Bauteilen

Loading Capacity of Engaged Thread Flanks – Considerations of Engineering Design for light components The loading capacity of engaged thread flanks plays an important role in the field of light weight design. Therefore, this contribution deals with a related analytic calculation for the design of high duty bolted joints. For typical exemplary applications the results of calculation are verified with experimental behaviour. Examples refer to components made of light metal with aluminium screws, components made of heat treated alloyed steels with very high strength steel screws, direct tapping into sheet metals and significant reduction of minimum required length of thread engagement by usage of threaded inserts.