טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentNoam Broitman
SubjectFatigue Investigation on Additive Manufacturing Products
DepartmentDepartment of Design and Manufacturing Management
Supervisors Professor Abramovich Haim
Dr. Shirizly Amnon
Full Thesis text - in Hebrew Full thesis text - Hebrew Version


Abstract

Additive Manufacturing (AM) is a field of manufacturing which began its first steps two decades ago.

The basic idea behind this technology is manufacturing solid parts by adding material versus more conventional manufacturing process which removes material (e.g. machining) or changes the shape of a solid material (e.g. forging).

This research focus on a process called SLM (Selective Laser Melting) which applies for metal parts.

SLM is a process in which a laser beam selectively melts desired areas in a layer of metal powder. After melting the desired areas in a specific layer, another layer of metal powder is being leveled above it and, again, a laser beam is selectively melting the desired areas. 

In this way a solid part is being built layer by layer until a desired geometry appears.

As mentioned, this manufacturing method is in its initial steps and the structural integrity must be examined. A few researches have been conducted on products of this process such as strength tests and fewer has been done in the field of fatigue. For the time of writing those lines, the author has no information regarding another research on crack propagation on products of additive manufacturing process being published in the professional literature, thus the present thesis can be regarded as innovative and breakthrough research.

The research presented in the thesis defines the crack propagation properties of Ti-6Al-4V which has been manufactured by selective laser sintering and compares it to wrought Ti-6Al-4V samples.

The results include monitoring of crack propagation behavior of Ti-6Al-4V manufactured by SLM in a two directions of manufacturing (x and y) as well as a few thermal treatments which the samples has been processed.     

The main conclusion from the present research is that the crack propagation properties of specimen which has been produced by SLM are as good as a wrought specimen.

One of the biggest advantages of additive manufacturing is the ability to create with the same effort a very complex geometry which in some cases are impossible to create by other manufacturing methods. A common geometry used for its added value (such as: weight to strength advantage, controlling heat transfer properties etc?) is a grid (lattice) structure.

Based on the knowledge which has been acquired during the first stage of this research, two lattice structures had been suggested and tested showing a significantly better fatigue behavior.