List of Tables
Chapter 1 Introduction, Literature Review, Significance and Objective of Work
1.2 Literature review
1.2.1.4 Influencing parameters in joining by tube end forming
Tube end forming has been utilized in formation of a new product. Few research highlights in this field have been discussed here. Alves et al. (2011a) introduced an innovative manufacturing process for shaping of seamless tubes into small size reservoirs.
For the special case of spherical reservoir, they found that the internal mandrel which is basic component of the reservoir forming process plays a key role. Alves et al. (2010) proposed a new method of producing gas and liquid storage reservoirs that ensures a better utilization of raw materials as compared to currently available technologies to fabricate reservoirs. Tan et al. (2013) proposed a two-stage end expansion of round tube into a square section which has two main advantages over other conventional processes.
The first advantage is the possibility of forming small corner radii and the second advantage is an improved square look around corners of the square section. Alves and Martins (2010) proposed an innovative forming process for shaping of thin walled industrial tubes into toroidal shells in a single-stage operation. Xia et al. (2014) proposed a new method of manufacturing tubes with nano/ultrafine grain structure by stagger spinning and recrystallization annealing. Here two experimental procedures are designed to refine the grains by considering material phase transformation, process optimization and heat treatment. The first method consists of five pass backward spinning where in the total thinning ratio of tubular blank achieved is 90 %. In the second phase, three pass
Chapter 1 spinning followed by 580°C × 0.5 h static recrystallization, and 2 pass spinning and a
580°C × 1h static recrystallization have been followed. The second method provided good surface smoothness and an improved spin-formability of spun parts.
Fundamentals of tube end forming such as tube curling, bead formation, upsetting of tube wall, end expansion etc. has been utilized by researchers for joining of a tube to a tube or with a sheet. These end formed joints are found to be suitable in domestic as well industrial applications. The tube-sheet joints have found their applicability in the assembly of stair cases, roofs and floors made from sheet panels or simply the attachment of tubular posts to base support members in barriers for controlling and managing queues and safety auto part from the braking system (Alves et al. 2011b). One classical example of end formed tube to tube joints is exhaust pipe such that it can eliminate leakage of gases and other fluids at the joint cross-section as welded tube to tube joints are not appropriate for such application. In this context, Heidler et al. (2012) and Turk et al.
(1991) emphasized a leak free exhaust system in a vacuum compatible gas bearing guide and radon control techniques in seven New Jersey houses with basements. Some critical findings in the field of mechanical joining using tube end forming have been addressed here. Alves et al. (2018a) joined a tube to a sheet in two stages. In the first stage, an annular flange is produced by partial compression of tube wall thickness along the longitudinal direction. In the second stage, the upsetting of tube‟s free end against a sheet with a beveled hole is done to lock the two parts together physically. Alves et al. (2011b) suggested a novel approach of joining a sheet to a tube which is accomplished by compression beading and external inversion. The load-displacement behaviour showed a sharp rise at the end of the joining process which is due to the result of compression of sheet panel against lower bead and upper external inverted end. Goncalves et al. (2014) investigated the deformation mechanics of inclined tube-sheet joints for a wide range of operating parameters. It is observed that slenderness ratio (lgap/ro) of the tube and inclination angle α of dies play a vital role in the formation of sound inclined tube-sheet joints. Here lgap is the initial gap between the tubes and ro is the reference radius of the tube. Zhang et al. (2014) used the principle of rotary swaging to join copper tubes having different diameters. The tensile strength of the joint made with different cases confirmed that the joint strength increases with increase in radial movement of the swaging die.
Alves at al. (2014) joined two tubes at their ends using expansion and beading. Good joints are obtained when the slenderness ratio of tubes (lgap/ro) lies between 1.25 and
Chapter 1 3.125. Later, Alves et al. (2017c) joined two tubes of different types namely S460MC
(carbon steel) and AISI304 (stainless steel) welded tubes using the same technique. This time the range of acceptable slenderness ratio is found to be between 1.25 and 2.5 for a successful joint formation. Kitamura et al. (2012) developed a cold joining method for joining of a rotor shaft with a disc. Successful joining is possible when the hardness of the disc is less than nearly 1/3rd of the hardness of the shaft material. Alves et al. (2017a) utilized localized thickening of the tube wall for subsequent joining of function element (sheet) by forming. The deformation mechanics is limited by the occurrence of plastic instability for lgap/t >10 between the initial gap length lgap and finalwall thickness t.
Alves et al. (2017d) joined two tubes at their ends, and the process consists of reduction, rounding and clamping by internal mechanical locking and the experiments were conducted on S460MC welded steel tubes. Later they performed the tensile test of newly formed joint and found that the maximum load the joint can withstand without failing is 30 kN. Silva et al. (2015) proposed a new process of joining two tubes which is based on the formation of lap joints by axisymmetric compression beading. The lap joints are capable of withstanding 64 MPa before sudden failure and a sharp spray of water is sent out during water tigntness test. Alves et al. (2018b) proposed a new joining by forming processes which involves forming an annular part with rectangular cross-section and performing the mechanical interlocking by upsetting the free tube end against the sandwich composite with a flaring punch. Destructive pull out tests have been performed upwards and not downwards because downward pull-out tests would provide larger pull- out forces and, therefore, would overestimate the performance of the joint. Alves et al.
(2018c) illustrated the potential of mechanical joining by plastic buckling. It was observed that wrinkling formed in circular, hexagonal and square PVC profiles with a slenderness ratio lgap/ro= 0.94 are successfully utilized to produce a connection with a polycarbonate sheet of 3 mm thickness at room temperature. Alves and Martins (2013) fixed sheet panels against tubular profiles using fundamental modes of tube deformation such as flaring and compression beading. The raw material utilized in the investigation consisted of commercial S460MC (carbon steel) welded tubes and DC04 (carbon steel) sheet plates. They observed that under torsional testing conditions the joints made through proposed joining method and welding performed identically.
Chapter 1 These studies reveal that, wherever compression beading is involved in joining
process, the parameter lgap/ro plays an important role. Further it is also revealed that joints made using plastic deformation have strength equivalent to joints made through conventional joining processes. Tube end forming is capable of manufacturing products which have industrial as well as domestic applications.