Analysis of the weld strength of the High Density Polyethylene (HDPE) dam liner
An analysis was carried out to determine the strength of welded joints in High Density Polyethylene (HDPE) dam liners. Samples were collected of welded joints and subjected to tensile tests and creep test. It was observed that the welded joints from field welded samples were much weaker and had a very low straining capacity than the un-welded material. The field welded specimens registered average strengths of 5 MPa as compared to 12 MPa of un-welded specimens and a maximum strain at fracture of 0.5 as compared to 3.5 of un-welded specimens. As a result of the weak welds it was found necessary to conduct further research into the best welds possible and a protocol for hot air and hot knife welding was developed. It was shown that for hot air welding while holding the width of the weld, applied pressure and dwell time of the pressure constant at 2.6cm, 0.3 MPa and 60 s, the recommended temperature of the hot air to achieve the strongest weld was 176 and for hot knife welding the recommended temperature of the knife was 400°C.