Numerical and Experimental Validation of the Prototype of A Bio-Inspired Piping Inspection Robot

Piping inspection robots are of greater importance for industries such as nuclear, chemical and sewage. Mechanisms having closed loop or tree-like structures can be employed in such pipelines owing to their adaptable structures. A bio-inspired caterpillar type piping inspection robot was developed at Laboratoire des Sciences du Num&eacute rique de Nantes (LS2N), France. Using DC motors and leg mechanisms, the robot accomplishes the locomotion of a caterpillar in six-steps. With the help of Coulomb&rsquo s law of dry friction, a static force model was written and the contact forces between legs of robot and pipeline walls were determined. The actuator forces of the DC motors were then estimated under static phases for horizontal and vertical orientations of the pipeline. Experiments were then conducted on the prototype where the peak results of static force analysis for a given pipe diameter were set as threshold limits to attain static phases inside a test pipeline. The real-time actuator forces were estimated in experiments for similar orientations of the pipeline of static force models and they were found to be higher when compared to the numerical model. Document type: Articl

DEVELOPMENT OF A SOFT PNEUMATIC ACTUATOR FOR MODULAR ROBOTIC MECHANISMS

Soft robotics is a widely and rapidly growing field of research today. Soft pneumatic actuators, as a fundamental element in soft robotics, have gained huge popularity and are being employed for the development of soft robots. During the last decade, a variety of hyper-elastic robotic systems have been realized. As the name suggests, such robots are made up of soft materials, and do not have any underlying rigid mechanical structure. These robots are actuated employing various methods like pneumatic, electroactive, jamming etc. Generally, in order to achieve a desired mechanical response to produce required actuation or manipulation, two or more materials having different stiffness are utilized to develop a soft robot. However, this method introduces complications in the fabrication process as well as in further design flexibility and modifications. The current work presents a design scheme of a soft robotic actuator adapting an easier fabrication approach, which is economical and environment friendly as well. The purpose is the realization of a soft pneumatic actuator having functional ability to produce effective actuation, and which is further employable to develop modular and scalable mechanisms. That infers to scrutinize the profile and orientation of the internal actuation cavity and the outer shape of viii the actuator. Utilization of a single material for this actuator has been considered to make this design scheme convenient. A commercial silicone rubber was selected which served for an economical process both in terms of the cost as well as its accommodating fabrication process through molding. In order to obtain the material behavior, \u2018Ansys Workbench 17.1 R \u2019 has been used. Cubic outline for the actuator aided towards the realization of a body shape which can easily be engaged for the development of modular mechanisms employing multiple units. This outer body shape further facilitates to achieve the stability and portability of the actuator. The soft actuator has been named \u2018Soft Cubic Module\u2019 based on its external cubic shape. For the internal actuation cavity design, various shapes, such as spherical, elliptical and cylindrical, were examined considering their different sizes and orientations within the cubic module. These internal cavities were simulated in order to achieve single degree of freedom actuation. That means, only one face of the cube is principally required to produce effective deformation. \u2018Creo Perametric 3.0 M 130\u2019 has been used to design the model and to evaluate the performance of actuation cavities in terms of effective deformation and the resulting von-mises stress. Out of the simulated profiles, cylindrical cavity with desired outcomes has been further considered to design the soft actuator. \u2018Ansys Workbench 17.1 R \u2019 environment was further used to assess the performance of cylindrical actuation cavity. Evaluation in two different simulation environments helped to validate the initially achieved results. The developed soft cubic actuator was then employed to develop different mechanisms in a single unit configuration as well as multi-unit robotic system developments. This design scheme is considered as the first tool to investigate its capacity to perform certain given tasks in various configurations. Alongside its application as a single unit gripper and a two unit bio-mimetic crawling mechanism, this soft actuator has been employed to realize a four degree ix of freedom robotic mechanism. The formation of this primitive soft robotic four axis mechanism is being further considered to develop an equivalent mechanism similar to the well known Stewart platform, with advantages of compactness, simpler kinematics design, easier control, and lesser cost. Overall, the accomplished results indicate that the design scheme of Soft Cubic Module is helpful in realizing a simple and cost-effective soft pneumatic actuator which is modular and scalable. Another favourable point of this scheme is the use of a single material with convenient fabrication and handling

Experimental Study and Numerical Simulation of Heat Transfer and Fluid Flow in Laser Welded and Brazed Joints

Laser joining with advantages of high power density and high processing speed is becoming a dominant process for joining parts of the body in white (BIW) in automotive manufacturing. Aluminum alloys and new generations of advanced high strength steels (AHSS) are of great value for the automotive industry to build light weight, environmentally-friendly, high-quality, and durable vehicles. Their usage in body structure is increasing due to high strength-to-weight ratio and good formability. Lap and coach-peel joints are the most commonly used type of joints in assembly of the body components manufactured with each of these two alloys. Laser brazing is a widely used process for joining closure panels in automotive manufacturing exemplified by joints such as the upper to lower panels of a liftgate or the roof to body side outer panels. Laser brazed seams are in visible areas and require a high quality surface and seam characteristics. Therefore, in this study novel techniques were studied to develop a robust welding and brazing processes of similar and dissimilar materials. Experimental studies as well as the numerical modeling and high-speed imaging approaches were used to gain a deeper understanding of the laser welding-brazing process, determine the effect of process parameters on weld dimensions, and analyze the dynamics of possible imperfections during the process. In dissimilar application, a feasibility study was conducted on laser joining of aluminum alloy to galvanized steel by means of twin-spot laser beams. Twin-spot mode was introduced to heat up a large surface area with less reduction in energy density for coach-peel joints with a wider geometry. The filler material was brazed on the steel side and partially fusion-welded on the aluminum side. The brazed results were investigated from the perspectives of microstructure evolution, tensile strength, surface roughness, edge straightness, and fracture mechanism. The generation of intermetallic compound (IMC) at the steel/seam interface was optimized by introducing a validated finite element thermal model to obtain the temperature history during the process and predict the thickness of a possible IMC layer. A multi-response optimization approach based on response surface methodology (RSM) was developed to find the fit model that correlated the main process parameters (laser power, wire feed speed, and scanning speed) and their interactions to surface roughness and mechanical strength. Under optimum processing condition the effects of alloying elements were also investigated on the performance of resultant joints. Different percentages of Si, Mn and Zn were introduced into the weld through three Al-based (AlSi12, AlSi5, and AlSi3Mn) and one Zn-based (ZnAl15) filler wires. Joint mechanical properties were examined in terms of monotonic loading circumstance. Microstructural properties were evaluated in terms of the IMC layer thickness and composition. In laser brazing of galvanized steels, the effect of laser beam inclination angle was investigated on process stability and spatter occurrence. Steel outer panels in automotive application are zinc coated for improved corrosion protection; however, the existence of low boiling element in coating has made the laser brazing process more challenging. Zinc has a boiling point of 907 °C which is lower than the melting range of copper-based filler wire, 965 – 1032 °C and as such is the predominant cause of laser brazing process instability and spattering for zinc coated steels. Therefore, experimental and numerical methods were applied to investigate the effect of laser beam inclination angle on laser braze quality of galvanized steels. High-speed videography revealed that spatter mostly occurred at the wetting line and melt pool front where the escaping zinc vapor came into interaction with the melt material. Application of a developed thermo-fluid simulation model considering laser-material interaction, wetting dynamics, material melting, and solidification, resulted in temperature profiles during the brazing processes for given beam angles as well as both the positions of the zinc evaporation front and wetting front. It was found that negative travel angles helped to move the zinc evaporation front ahead of the wetting front and reduce the interaction between the zinc vapor and melt pool. Experimental observations confirmed that partially removing and/or evaporating the zinc layer ahead of the wetting zone contributed to a stable process and good braze quality