How to get a better critique between students?

As the title suggests, I am not sure how to go about this topic.  The problem is that many students are afraid to give strong art critiques for a myriad of reasons, but I suspect the most prevalent is fear of others not liking them.  Vicarious modeling a term used by Psychologist Albert Bandura, is an important part of bringing up a persons self-efficacy (self efficacy is one's perceived ability to accomplish a goal). Vicarious modeling is how one sees themselves as compared to others. On one hand if someone sees themselves as being at the top of the group, they will tend to go further, try harder and persevere in the face of adversity, while on the other hand perceiving one is at the bottom of the group one can lower their belief in their abilities having a reverse effect.  How can I have vicarious modeling within the classroom without lowering self efficacy?  Perhaps it is not possible to accomplish this goal, as it is not possible to program every reactive thought and processing of information within the students mind.  But perhaps social hierarchies can be limited by anonymous artistic critique.  While this process is likely to fail due to students noticing other students work in their common space; it may be possible to get a more honest participatory critique if names are not eluded to during class critiques.   But the students still know that the assignments are done by their peers, so critiques might not take a different shape.  In fact because students don't know whose work they are looking at they might even be more reserved.  Perhaps an online anonymous critique done outside of class would yield better results?

Below is a description of an assignment I would like to test this on:
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Assignment: Create 5 PBR materials from a professors list.
A list with a great number of possible materials is presented to the class. 
There are many categories of materials and each student is to go to the list and pick 5 materials from 5 different categories (Ex. Rock, sand, scratched metal, snow, glass).
Students go up one at a time and pick one material from one category, scratches it off the list, then sit down (in order of the room). The last student picks 2 materials and then the reverse order commences until everyone has 5 materials. 
Critique: Students hand in their assignments as an Unreal 4 (UE4) material to a folder on the schools network. 
The assignment will be entered into an online database that allows for voting and tracking of results.
Desired outcome: Students will critique more objectively and hopefully without reservation without knowing who did what.


 
On another topic, how might this assignment be Spiraled 4 times to keep ramping up the difficulty throughout a semester? 
Level 1: make 5 materials, tiled using Bitmap 2 Material (B2M)
Level 2: Make 4 materials: 1) brick tiled 2) one a leaf with opacity 3) one of your choice using multiple blended layers at least 3 layers; a base layer and two additional layers Ex. Metal panel with with scratches and dirt. 4) texture that has multiple layers using masks e.g. wood with paint.
Level 3: make 3 materials, tiled using Substance Designer (SD) 1) organic 2) sci-fi 3) your choice
Level 4: make a material using ZBrush