Approach for testing the material behavior in roll forming in a small scale

Roll forming of ultra-high strength steels (UHSS) and other high strength alloys is an advanced manufacturing methodology with the ability of cold forming those materials to complex three-dimensional shapes for lightweight structural applications. Due to their high strength, most of these materials have a reduced ductility which excludes conventional sheet forming methods under cold forming conditions. Roll forming is possible due to its low strains and incremental forming characteristic. Recent research investigates the development of high strength nano-structured aluminum sheet and titanium alloys, as well as their behaviour in roll forming with regard to formability, material behaviour and shape defects. The development of new materials is often limited to small scale samples due to the high preparation costs. In contrast, industrial application needs larger scale tests for validation, especially in roll forming where a minimum sheet length is required to feed the sample trough the roll forming machine. This work describes a novel technique for studying roll forming of a short length of experimental material. DP780 steel strips (500mm &ndash; 1300mm length) were welded between two mild steel carrier sheets of similar width and thickness giving an overall strip length of 2m. Roll forming trials were performed and longitudinal edge strain, bow and springback determined on the welded samples and samples formed of full length DP780 strip before and after cut off. The experimental results of this work show that this method gives a reasonable approach for predicting material behavior in roll forming transverse to the rolling direction. In contrast to that significant differences in longitudinal bow were observed between the welded sections and the sections formed of full length DP780 strip; this indicates that the applicability of this method is limited with regard to predicting longitudinal material behavior in roll forming.<br /

DESIGN AND DEVELOPMENT OF A LOW COST MOUNTED TYPE SINGLE LEG SUBSOILER

Free movement of air in the soil and good drainage are necessary for good crop yields.Modem tractors and machinery are partly responsible for soil compaction and soil pans.Subsoilers are used to break compacted soil, allowing free passage of air and water. Forconducting this important operation in crop production, suitable Subsoiler does not existin Sri Lanka. However without proper land preparation, higher yield of crop productionby applying other input cannot be expected. Therefore fields should be subsoiled time totime at right angles to the intended direction of ploughing. Sometimes fanners useexpensive, un tested, imported Ploughs for this purpose. The commercial ploughs used inmany developed countries, are beyond the financial capabilities of local paddy farmers.Properly designed subsoilers are usually mounted on the tractor and consist of a strongframe with one or more legs. Each leg has a replaceable point. Working depth isnormally from 30 to SOcmand spacing between passes is from 0.5 to 2m. Subsoiling isbest carried out after the cereal harvest when the soil is dry.Considering the above facts, a low cost suitable Subsoiler for four wheel tractors wasdesigned and constructed after testing first model Subsoiler in the field and implementingnecessary modificationsAn experiment was conducted in the paddy field to compare the performances of thedeveloped Subsoiler. The result shows that the effective field capacity, effective workingwidth, ploughing depth, travel reduction. average operation speed, and Cost ofproduction of Subsoiler were 0.2 ha/hr, O.Sm,0.3m, 60/0, 1.6 km/hr, SOOORsrespectively.The result shows that the overall field performances of designed Subsoiler wassatisfactory.