Effect of selective laser heat treatment on geometrical variation in boron steel components: An experimental investigation

Selective laser heat treatment is a well-known process for its ability to produce tailor heat treated blanks (THTB). Specifically, ultra high strength boron steels with tailored material properties can be produced. However, this process generates unwanted distortion and influences geometrical variation. This in turn can affect functionality, aesthetics, and performance of the final product. Understanding the effects on geometrical variation in the final product or the assembly will enable in designing and producing geometry assured products. In this paper, boron steel blanks were selectively laser heat treated with a specific heat treatment pattern and laser heating direction sequence. These heat treated blanks were then cold formed. Further on, spot welding simulation of the cold formed parts was performed to assess the effect on geometrical variation at the assembly level. The results show that the effect of selective laser heat treatment on geometrical variation at part level propagates further to the assembly level. It implies that the effect on geometrical variation should be minimized at part level, when the blanks are laser heat treated. Hence, the sources that influence geometrical variation at part level when employing selective laser heat treatment are presented and discussed. The motivation and possibilities to minimize the effects in the early design concept stages is provided.

Fabrication of Stretchable Transparent Electrode by Utilizing Self-Induced Vacuum Force

The key challenge in fabricating a stretchable transparent electrode is the effective transfer of an electric conductor to a stretchable substrate. To this end, we used vacuum force to fully permeate the elastomer substrate into the electric conductor. The vacuum force was self-induced from the evaporation of the solvent in the electric conductor. Hence, a solvent, having a high evaporation rate, is postulated to exhibit superior fabrication quality. To demonstrate this, three different solvents were tested for preparation of the conductor slurry. In the test, the high-vapor-pressure solvents resulted in the superior quality of the fabricated stretchable electrode. Furthermore, the heating direction was changed during thermal curing to maximize the self-induced vacuum force. The plate-heating curing exhibited better transferring efficiency of the electric conductor because the evaporation of the solvent in the conductor slurry was accelerated faster than that of the thermal curing of the elastomer substrate. Besides the achieved high quality of the electrode, the fabrication cost can be drastically reduced because the extra process required to dry the electric conductor is omitted by simultaneous curing of the electric conductor and the stretchable elastomer substrate.

Effects of inductor patterns on temperature and deformation behavior of ship hull plate by induction heating

This paper mainly investigated the effects of different inductor patterns on thermal forming behavior of ship hull plate by moving induction heating. Alternately-coupled electromagnetic-thermal analysis procedure considering temperature-dependent material properties was firstly implemented at each moving step of inductor, followed with uncoupled thermal-mechanical transient analysis to obtain corresponding thermal deformation. Then temperature distribution, dimensions (breadth b and depth h) of heat-affected zone, and deformation obtained from codirectional current-carrying inductor with no gap and opposite-direction current-carrying inductor with gap were compared, respectively. And effects of heating directions and distance T2 of ODIG were also analyzed. It turns out that codirectional current-carrying inductor with no gap can generate much larger transverse shrinkage at 1.8–2.5 mm/s than opposite-direction current-carrying inductor with gap, otherwise smaller at 3.2–4.0 mm/s, likewise larger temperature gradient at 1.8–4.0 mm/s and thus larger bending angular deformation. Besides, heating direction “Out” can generate larger deformation than “In” and deformation for opposite-direction current-carrying inductor with gap can be effectively improved through adjusting distance T2 until 13 mm. These indicate that adopting appropriate inductor patterns, heating direction and distance T2 of opposite-direction current-carrying inductor with gap can significantly improve thermal forming behavior.

Interface Separation Detection of Concrete-Filled Steel Tube Using a Distributed Temperature Measuring System

In recent years, concrete-filled steel tubular (CFST) bridges have been widely used in bridge construction. However, interface disengaging is one of the bridges’ most common defects. It affects not only the confinement of the steel tube to the core concrete, but also the bearing capacity and the structure durability. In order to solve the problem of disengaging at the interface of steel tube-confined concrete and ensure the integrity of the structure, a new method based on a distributed temperature detection system is proposed to identify disengaging at the interface between steel tube and concrete. Through the analysis of experiments and numerical simulation, it was found that when the structure surface was heated, the temperature of the void area was higher than that of the solid area. The temperature of the maximum void height was the highest, the temperature increase rate was the fastest, and the cooling rate was the slowest. The boundary of the void suffered from sudden changes in temperature. The more serious the void, the greater was the temperature difference between the void and the solid. After changing the heating direction, the temperature distribution could still be identified. This study achieved simplicity and efficiency with respect to the detection of interface separation.

The Structure of Overionized Plasma in SNR IC 443

During the last few years, overionized (recombining) plasmas were unexpectedly discovered in a few supernova remnants, but the origin is still unclear. In this contribution, we present a preliminary spectroscopic analysis of the X-ray emission from the north central region of IC443, one of the “recombining” remnants. An overionized NEI plasma model can reproduce well the Ly-alpha lines and the recombination edges in the spectrum. The ionization temperatures for the metals Mg, Si and S are much higher than the electron temperatures. which is a strong indication of overionization of these elements. The different spectral features of the recombining plasma are characterized on scales of a few arcmin, such as the increasing trend of the pre-cooling temperature and the ionization time from south to north, which may imply a pre-heating direction.