tailieunhanh - Manufacturing Processes phần 5

Nếu cường độ dòng điện được sử dụng để thiết lập các thủ tục hàn, một phần mở rộng điện cực không chính xác có thể không bị phát hiện. FCAW tự che chắn và khí-Shielded Trong danh mục của FCAW, có hai tập con cụ thể: thông lượng nòng cốt bảo vệ tự hàn hồ quang (FCAW-S) (Hình ) và cốt lõi thông lượng khí được che chắn hàn hồ quang (FCAW G) (Hình ). | DESIGN OF WELDED CONNECTIONS 13-41 Table Length and Spacing of Intermittent Welds Continuous weld Length of intermittent welds and distance between centers in 75 3-4 66 4-6 60 3-5 57 4-7 50 2-4 3-6 4 8 44 4-9 43 3-7 40 2-5 4-10 37 3-8 33 2-6 3-9 4-12 30 3-10 25 2-8 3-12 20 2-10 16 2-12 length of weld to be used per unit length. For convenience Table lists various intermittent weld lengths and distances between centers for given percentages of continuous welds or calculated leg size continuous actual leg size used intermittent Connections Subject to Bending or Twisting The problem here is to determine the properties of the welded connection in order to check the stress in the weld without first knowing its leg size. One approach suggests assuming a certain weld leg size and then calculating the stress in the weld to see if it is over- or understressed. If the result is too far off the assumed weld leg size is adjusted and the calculations repeated. This iterative method has the following disadvantages 1. A decision must be made as to throat section size to be used to determine the property of the weld. Usually some objection can be raised to any throat section chosen. 2. The resulting stresses must be combined and for several types of loading this can become rather complicated. Proposed Method The following is a simple method used to determine the correct amount of welding required to provide adequate strength for either a bending or a torsion load. In this method the weld is treated as a line having no area but having a definite length and cross section. This method offers the following advantages 1. It is not necessary to consider throat areas. 2. Properties of the weld are easily found from a table without knowledge of weld leg size. 3. Forces are considered per unit length of weld rather than converted to stresses. This facilitates dealing with combined-stress problems. 4. Actual values of welds are given as force per unit length of weld instead of