Analysis of premature failure of a tie bar in an injection molding machine

Sasikumar, C and Srikanth, S and Das, S K (2006) Analysis of premature failure of a tie bar in an injection molding machine. Engineering Failure Analysis, 13 (8). pp. 1246-1259.

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Premature failure of a tie bar made of AISI 4140 steel in a 150 tonne plastic injection-molding machine has been analyzed. Although the nominal tensile stress acting on the tie bars (95.5 MPa) is far lower than the yield strength of this material (750–900 MPa), the tie bars are subjected to a pulsating cyclic loading during the plastic molding process. The failure was found to occur at the root of the first thread by transverse fatigue fracture induced by a pulsating tensile stress with multiple points of high stress concentration. The high stress concentrations appear to have been introduced by a combination of improper molding parameters resulting in uneven tensions in the four tie bars and aggravated by the presence of some material defects. The material defects observed are inclusions, presence of some retained austenite and fine cracks. A hydraulic clamping mechanism rather than a toggle clamp mechanism for the mould will minimize the cyclic strain on the tie rods.

Item Type:Article
Official URL/DOI:
Uncontrolled Keywords:Failure analysis; Fatigue fracture; Transverse fatigue strength; Inclusions
Divisions:NML Chennai
ID Code:205
Deposited On:28 Oct 2009 15:22
Last Modified:30 Nov 2011 09:41
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