Very important property of powder metallurgy parts is ability to join to components produced by different manufacturing technologies or dissimilar materials. Properties of powder metallurgy Nb modified HK30 components are highly influenced by conditions applied during sintering. Weldability of sintered components can be improved using favorable sintering conditions. In this regard, effect of sintering parameters on fusion weldability of Nb modified HK30 is presented in this paper. Investigation of weld joints between HK30, produced by different sintering conditions, and cast HK30 stainless steel is performed. In addition, examination of welds between sintered HK30 and wrought 304 stainless steel is also performed. Microstructural examination and hardness testing of fusion zones and heat affected zones were done for different combinations of base material.

Metal injection molding technology is commonly used in production of small and very complex parts. Residual porosity is unavoidable characteristic of P/M parts, affecting their final properties. During injection molding phase powder-binder separation can occur, causing green density variation through cross section of the part. This behaviour is particularly pronounced as complexity of the parts increases. As a consequence, zones with different density and residual porosity can be seen after sintering. In this regard, porosity and hardness distribution of the sintered ring-shaped part is analysed and presented in the paper.

The volumetric flow rate (injection velocity) and the holding pressure are metal injection molding (MIM) parameters that have a strong influence on the green parts density and density homogeneity, but their effect on sintered dimensions after sintering is still to a large extent unexplored. To reveal the relationship between the injection molding parameters and sintered dimensions, ring-shaped components were injection molded by using different values of injection velocities in combination with a rump-down and rumpup holding pressure profile. Afterwards, the green components were catalytically debound and sintered in the nitrogen (N2) atmosphere. Finally, the component dimensions: the height, inner and outer diameter were measured by using a coordinate measuring machine. The ready-to-mold granules Catamold 310N made of heat resistant stainless steel X40CrNiSi 25-20 (according to the EN standard) powder and polyacetal based binder were used. The results showed that the interaction between the injection velocity and the holding pressure profile can be used to systematically adjust shrinkage after sintering. This approach is based on the dependence of the binder crystallization temperature on pressure, when the powder/binder proportion changes with the injection velocity.

The weld line is an inevitable defect in the most injection molded components. It is a zone with reduced mechanical properties negatively influencing on the molding behavior in exploitation. The effect of: melt temperature, holding pressure and time, injection velocity and cooling time on the weld line tensile strength is analyzed in this paper. The material of the moldings was high density polyethylene (HDPE). The results showed that the holding pressure, injection velocity, melt temperature and cooling time have significant influence on tensile strength.

The weld line is an inevitable defect in the most injection molded components. It is a zone with reduced mechanical properties negatively influencing on the molding behavior in exploitation. The effect of: melt temperature, holding pressure and time, injection velocity and cooling time on the weld line tensile strength is analyzed in this paper. The material of the moldings was high density polyethylene (HDPE). The results showed that the holding pressure, injection velocity, melt temperature and cooling time have significant influence on tensile strength.

The weld line is an inevitable defect in the most injection molded components. It is a zone with reduced mechanical properties negatively influencing on the molding behavior in exploitation. The effect of: melt temperature, holding pressure and time, injection velocity and cooling time on the weld line tensile strength is analyzed in this paper. The material of the moldings was high density polyethylene (HDPE). The results showed that the holding pressure, injection velocity, melt temperature and cooling time have significant influence on tensile strength.

Production of nickel-free austenitic stainless steels is usually performed using sintering or melting in nitrogen atmosphere, where nitrogen as austenite forming element replaces nickel. These steels can also be produced by additional nitriding in solid state of final ferritic stainless steel components. In this case, properties of the steel do not depend only on casting or sintering parameters, but also on nitriding and post sintering heat treatment parameters. In this regard, effect of subsequent heat treatment parameters on properties of the sintered austenitic nickel-free stainless steel were analysed in this work. Post sintering heat treatments, in nitrogen atmosphere, were performed using dilatometer DIL 402/C/7. Microstructural changes after heat treatment and dilatometer test results are presented in the paper.

This paper presents effect of the cavity position on green mass of metal injection (MIM) parts molded in a four-cavity split mold for different values of injection velocity, holding pressure profile and mold temperature. Test components where ring-shaped containing an external groove at the middle of height. It was found that the parameters that have greatest influence on part mass in single cavity are mold temperature folowed by holding pressure and injection velocity. Obtained experimental results also addres that the main source of variation in verticaly positioned runner system becomes cavity to cavity variation. In this case cavity to cavity variation increase is caused by separation and segregation supported by gravity effect.It was also found that in binder rich upper-cavity zone at sufficiently low mold temperature packing pressure increase cause decreasing of green part mass due to shift of glass transition temperature toward higher values.

Increased use and production of sintered stainless steel components require more intense investigation of their weldability. Weldability of P/M parts requires additional analysis compared to wrought or cast metals due to their specificities in physical properties. Residual porosity and sintering parameters of the heat resistant stainless steels are factors that mostly affect not only properties of sintered parts, but also their weldability. In this regard, effect of sintering parameters on the weldability of the Nb-modified heat resistant stainless steel HK 30 is discussed in this paper. Comparison of solid state and fusion welding of sintered components was performed using sinterjoining and plasma welding. Microstructure of sinter joined area, solidification structure of melting zone and microstructure changes in heat affected zone were explored using metallographic techniques. Hardness distribution through fusion zone and heat affected zone was also analysed and presented in the paper.

This paper presents non-cooperative game-theoretic transmission power control algorithm to optimize network-wide communication performances for homogeneous competitive vehicle nodes in interference-limited vehicular ad hoc network (VANET) with limited inter-node feedback signaling channels. Based on a class of self-incentive convex payoff functions, vehicular nodes employ the proposed Feedback-free Adaptive Self-regulating (FAS) control algorithm to select optimal strategies that converge to Nash equilibrium (NE) whenever system changes occur. The control algorithm is characterized with the following features: (1) it does not require inter-node feedback signaling and messaging controls; (2) each transmitting node only needs to observe the aggregate interference in the environment; (3) the game is formulated to enable self-enforcement guided by rational self-incentive. System simulation of an interference-limited VANET with a realistic vehicular mobility model is developed to evaluate NE convergence performance of the game-theoretic FAS control algorithm.

The success of air bending process depends on ability to accurately determine the punch displacement for desired bend angle after unloading. Punch displacement in the air bending is a complex function of tool and part geometry, mechanical properties of sheet and their changes during bending. The aim of this research was to develop the FE models for punch displacement and springback prediction using LS-Dyna. In order to validate results of the FE simulation, five bending experimets for materials S355MC and DD13 were conducted. It was found that FE springback predictions for microalloyed S355 MC steel are significantly lower compared to experimental data, while predictions for mild DD13 steel can be reliably used.

This paper considers the problem of competitive sharing of open spectrum resources between collocated spread spectrum based secondary systems. The problem is formulated as a strategic form game where the objective of each player (secondary system) is to maximize its own payoff defined in terms of resource utilizations. The necessary and sufficient conditions for the existence of the optimal Nash equilibrium solution are derived for the specified payoff functions. Using tools of the non-cooperative game theory, the Payoff-Enriched Adaptive Learning (PEAL) methodology is proposed to enable each secondary system to iteratively adapt spectrum access strategy in response to the observed interference from other secondary systems. The self-learning adaptations of PEAL require neither signaling nor time synchronization between autonomous secondary systems. It is shown through extensive numerical evaluations that the PEAL adaptations converge to the theoretical Nash equilibrium in a finite numbers of trials.

The paper discusses a generalized design of employing a Back-Propagation (BP) neural network (NN) as an intelligent controller that requires no identifier, to control time-varying and nonlinear (NL) possibly unstable systems of unknown parameters, stable or unstable, for achieving self-adaptive model reference control (MRC) or target-tracking control (TTC). Certain theoretical difficulties are discussed and some questions are left unanswered. However, it is shown that certain inevitable assumptions must be made, due to the impossibility of incorporating and awaiting convergence of an identifier if stabilization of an unknown nonlinear unstable system is to be expected, and regardless of the status of global nonlinear controllability theory. Algorithm designs are given for the BP-based control of SISO unstable time-varying and nonlinear systems when no identifier is employed, as is a computed example. Still, the weight initialization problem remains unsolved, as it presently requires several trials.