Automotive Engineering

Using blends of natural gas (NG) and hydrogen as an alternative to gasoline in Internal Combustion Engines (ICEs) has the potential of a major reduction in CO2 and other harmful emissions, besides giving insight into the use of gaseous biofuels, rich in methane and hydrogen, and offering a transition scenario towards a hydrogen economy. To investigate the consequences of using blends, the performance of a 240cc stationary ICE and a Yamaha Majesty YP125FI scooter, converted to run on a large variety of blends of hydrogen and NG, have been investigated at HAN University, Netherlands, The effect of the air-to-fuel ratio and the composition of the blend on the performance and the emissions have been studied. This paper gives insight into those effects. Main conclusions: With only minor modifications a large variety of blends can be used. And by adding H2 to NG: CO2, CO, and HC emissions are reduced; NOx emission is increased; high l is possible, which can eliminate high NOx ; power and efficiency drop approx. 10%

M. Amirthalingam, E.M. van der Aa, N. den Uijl, M.J.M. Hermans & I.M. Richardson: Phosphorous and boron segregation during resistance spot welding of advanced high strength steels; 9th International Conference on Trends in Welding Research; Chicago, Illinois, USA; June 4-8 2012.

The mechanical properties of advanced high strength steels (AHSS) are sensitive to their multi-phase microstructures.
Phosphorous is added in AHSS mainly as a solid solution strengthener and to suppress the formation of cementite, thereby enhancing the room temperature stabilisation of austenite in transformation induced plasticity (TRIP) and quench and partitioning (Q&P) steels. However, the weldability of phosphorous containing steels is poorer than conventional low carbon steels due to embrittlement resulting from the segregation of phosphorus to grain boundaries during solidification of the weld pool. In order to reduce the grain boundary embrittlement, the addition of boron has been suggested; however, this also increases hardenability and the ratio of boron to other alloying elements present in the steels also affect the mechanical properties of the welds.
In this work, the partitioning behaviour of phosphorous and boron during the solidification of weld pools under various weld thermal cycles has been studied using experimental simulations and a DictraTM based diffusional model. Steels with varying carbon, phosphorous and boron contents were designed and subjected to various welding thermal cycles.
Mechanical properties were evaluated by hardness, cross tension tests and correlated with the weld microstructure. Diffusion calculations show that the phosphorus concentration in the last area in the weld pool to solidify can reach about 0.38 wt. % for a steel with a bulk concentration of 0.08 wt. %. Elemental analysis indicates that in the absence of boron, the grain boundaries of columnar grains in the weld pool are decorated with phosphorous. As a result, a complete interface failure occurs during cross tension testing. With the addition of boron, apart from an increase in weld strength, the failure mode switches to a complete plug mode.