PSI - Issue 60

A. Bhardwaj et al. / Procedia Structural Integrity 60 (2024) 723–734 Abhimanyu Bhardwaj/ Structural Integrity Procedia 00 (2019) 000 – 000

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isotopes, material irradiation, sterilization, and nuclear waste transmutation, as explained by Sun An et al. (2005), H. Padamsee (2001), and N. Nigam (2015). Typically, particle accelerators are fabricated using vacuum compatible and thermally conductive materials like stainless-steel, aluminium, and copper. To leverage the distinct properties of these various metals, compound metallic structures are frequently employed for vacuum chambers, beam-line, and front-end components. However, due to notable differences in the thermal and mechanical characteristics of these metals, conventional joining techniques, such as welding, prove ineffective. This can be seen in the work performed by M. Gallilee et al. (2014), T. Murakami et al. (2003), J.L. Song et al. (2010), H.T. Zhang et al. (2007), H. He et al. (2019), S. Babu et al. (2018), M. Zhao et al. (2023), C. Muralimohan et al. (2018), and H. Dong et al.(2012). As a result, vacuum brazing is commonly employed to create transition joints between dis-similar metals. To facilitate this process, RRCAT has a cold-walled, dry-pumped, controlled atmosphere furnace, as illustrated in Fig. 1. The furnace has a work zone with a diameter of 500 mm and a length of 1.5 m, with operating temperature of 1100 deg C. In order to maximize the utilization of the furnace's work zone, a titanium-zirconium-molybdenum (TZM) alloy job-carrier has been designed and developed. TZM alloy has emerged as a prominent high-temperature material in various applications owing to its exceptional combination of properties. Its high melting point, remarkable strength, high elastic modulus, minimal linear expansion coefficient, low vapour pressure, excellent electrical and thermal conductivity, robust corrosion resistance, and high-temperature mechanical characteristics make it highly desirable in military, aerospace, high temperature structures, and other related fields, as explained by B. Apt et al. (2019) and R.L. Ammon et al. (1980). Chemical composition and properties of TZM alloy are illustrated in Table 1 and 2, respectively.

Table 1 TZM alloy chemical composition. C H Fe

Mo 99.4

Ni

N

O

Si

Ti

Zr

0.010-0.040

<0.00050

<0.010

<0.0050

<0.0020

<0.030

<0.0050

0.40-0.55

0.060-0.12

Table 2 TZM alloy properties. Property

Value

10220 Kg/m 3

Density

Coefficient of thermal expansion

6.1 e-6 /K @ 25-1200 deg C

Melting Point Young’s Modulus

2623 deg C

325 GPa @ 25 deg C 100 GPa @ 1200 deg C 62 MPa @ 1650 deg C 400 MPa @1200 deg C 860 MPa @ 25 deg C 0.3

Poisson’s ratio

Tensile strength, Yield

Thermal conductivity

118 W/m.K

The typical preparation methods for TZM alloy include arc melting-casting and powder metallurgy. In the arc melting-casting method, pure molybdenum is melted using an arc, and precise amounts of Tungsten (T), Zirconium (Zr), and other alloying elements are added based on weight percentages to obtain the TZM alloy using conventional casting techniques. On the other hand, the powder metallurgy approach involves uniformly mixing high-purity molybdenum powder with TH2 powder, ZH2 powder, and graphite powder, followed by cold isostatic pressing and sintering at high temperatures under a protective atmosphere to produce TZM alloy blanks, as explained by C. Tuzemen et al. (2019). These manufacturing processes make welding of TZM alloy challenging. As a result, the present job-carrier design relies solely on standard structural components, such as U-rails and plates connected using cotter pins. In addition to ensure structural integrity and withstanding thermal cycles, the design of a lightweight and demountable job-carrier is of paramount importance. This stems from the limited load carrying capacity of 500 kg inside the furnace, making it essential to keep the job-carrier's weight to a minimum while ensuring its ease of disassembly and reassembly as well. Firstly, the design methodology for the TZM alloy job-carrier is thoroughly discussed, outlining the considerations and decisions made in its conceptualization and development. Secondly, the application of finite element analysis (FEA) to compute stresses, deformations and limit load. This section delves into the numerical simulations to evaluate the structural performance under loading and thermal conditions.