Advanced Materials Research Vols. 418-420

Abstract: The characteristics of welding current in rotational arc GMAW were analyzed in this paper. It was found that the compulsively short circuiting transfer would take place when the electrode rotating to the sides of V groove. During the period of short circuiting transfer, the welding currents would sharply increase, so as to affect the average value of welding current in one rotational cycle. A novel method was proposed to detect the height of welding gun in this paper. The method use of least-square fitting method to fit the welding currents into a plane in three dimensions, and then through compute the distance between origin of coordinates and the plane to detect the height of welding gun. In the last, the validity of the method was proved through experiments.

Abstract: One of the major applications for cold formed carbon steel ‘C’ sections is through load carrying structural frame side members in heavy road vehicles. Though it is expected that forming operations would enhance the mechanical properties of sections as a whole by strain-hardening, it leaves certain amount of residual stresses throughout the sections. It is thus necessary to account for the effect of residual stresses remaining from cold forming operations accurately, while assessing the mechanical behavior of truck side frame rail sections. In this work, an experimental investigation was carried out to assess residual stresses induced by cold forming operation of truck frame rail sections through X-ray diffraction method. Also an attempt was made to study the effect of shot-peening operation employed as a surface enhancement method on frame rail residual stresses.

Abstract: The effect of compound modification and various kinds of heat treatment on microstructure and mechanical properties of the low chromium white cast iron was studied.The results showed that,after modification,the carbide morphology in cast iron has been greatly improved;the annealed modified cast iron is suitable for machining;both martensitic quenching and austempering can cause the hardness and the impact toughness of modified cast iron increase greatly.

Abstract: Combined shape and gauge control is a hot issue in continuous hot plate and strip rolling field. Due to the coupled function of shape and gauge control in rolling process, mutual effects must be considered when shape control is carried out. Traditional shape and gauge control theories are of independent and the control systems are also separated, so it is difficult to ensure the quality of shape and gauge simultaneously. Based on the shape theory of shape and gauge control and function Φ derived from the load distribution method of Ichiro Imai , a combined shape and gauge control scheme was developed, which can adjust rolling regulations on-line according to the deviation of strip crown measured at the exit of the rolling mill. The method can ensure gauge precision while strip crown is adjusted and the purpose of combined shape and gauge control is reached.

Abstract: Chassis frame rails in a truck are load bearing structural members that integrate vehicle power train with superstructure to form a complete vehicle. Large numbers of bolt holes that are cut into these frame side members act as joineries and points of attachments for various sub systems of the truck. While bolt holes are unavoidable due to its primary functional importance, the near hole residual stresses remaining from hole cutting operations may play a significant role in deciding the life of frame rail sections as they lead to early initiation of fatigue cracks around bolt hole surface. In order to assess the extent of plastic deformation and resulting residual stress pattern in near hole areas of bolt holes, experimental investigation through microstructure analysis, micro-hardness and X-ray diffraction measurements has been taken up. The hole cutting operations considered for this exercise are drilling, punching, laser cutting and water jet cutting used to cut holes on truck frame rail sections. Apart from this, an assessment of shot-peened hole surface was also taken up to understand the effect of shot-peening on structural behavior of frame rail bolt hole sections. The experimentally measured near hole residual stress profiles can be considered as initial conditions for further numerical analysis to study the influence of bolt hole residual stresses on fatigue life of frame rail sections.

Abstract: High efficiency and high surface integrity grinding of fused silica lens used in the ultraviolet (UV) laser transmission equipments is highly demanded. It is necessary to decrease the undeformed chip thickness for producing better surface integrity. We conducted creep feed grinding (CFG) and conventional shallow cut grinding (SCG) experiments of fused silica with a resin bond diamond wheel. Experiment results shows that owing to thinner undeformed chip thickness, the normal grinding force, radial wheel wear and P-V value of surface roughness of CFG are smaller than those of SCG at the same MRR. At the same table speed, surface roughness decreased with the increase of MRR in both CFG and SCG as a result of decreased undeformed chip thickness which is attributed to the elasticity of resin bond.

Abstract: A measuring system of dynamic resistance in resistance microwelding (RMW) of insulated copper wire was developed. The system included a computer, data acquisition (DAQ) card, current sensor, digital trigger circuit and analysis software. Dynamic resistance patterns at the secondary circuit under both normal and abnormal welding conditions were successfully monitored by this system. The results show that the dynamic resistance during the RMW of insulated copper wire is a monotonously decreasing curve; a wave crest will appear when surface splash occurred. This peak characteristic can provide a sound approach to in-process monitor weld quality for RMW of the insulated copper wire.

Abstract: High-speed milling is recognized as one of rapidly development machining methods. The article gives details of machining experiments with different aluminum alloys. Through a lot of single factor experiments and the orthogonal multi-factor experiments, and also use method of semi-artificial thermocouple. This paper mainly studies influence of surface roughness and residual stress with changed rotate speed, tooth load and radial depth of cut, and changed law of processing temperature for rotate speed. Though experiments shows that enhancing rotate speed may reduce surface roughness and residual stress within certain limits and the result of experiments is not agree with Carl Salomon’s theory.

Abstract: Based on the theory of adiabatic shearing, the forming process of a serrated chip during cutting Ti-6Al-4V titanium alloy was analyzed by comparing the results of the finite element (FE) calculations with the cutting experiments. The results show that the equivalent stress, equivalent strain and equivalent strain rate within a ribbon chip varied a little, but they varied a lot within a serrated chip. Moreover, the effect of cutting speed on equivalent strain rate is greater than on the equivalent stress and equivalent strain within a serrated chip. It can also be found from the results that there are small gaps between the simulation results and experimental results for the chip thickness and sawtooth height, while there is a big gap for saw-tooth pitch. This means that the simulation model has its limitations for accurate simulation of micro-geometric shape of a chip during cutting the Ti-6Al-4V titanium alloy, and further research remains to be done.

Abstract: A combined numerical and experimental study is performed to analyze the feasibility of using heat pipe cooling in milling applications. In this model, it is assumed that the end mill is subjected to a static heat source which verifies the analysis and feasibility of using heat pipe cooling in milling operations. The performance of heat pipe mill model is approximated using a solid cylinder model of pure conduction. Both the numerical and experimental studies show that the use of a heat pipe in a mill can reduce the temperature field significantly.