Photosynthesis

• The light-dependent reactions take place in the thylakoid membranes of the chloroplasts.
• Welding defects can be defined as weld surface irregularities, discontinuities, imperfections, or inconsistencies that occur in welded parts
• Effect of Heat Input:

  • Arc Blow: The movement of uneven flux line that causes an arc to move during a weld
• Ways of Controlling Arc Blow:

  • Connect two leads to the end of the weld joint
  • Connect the work lead to the end of the joint
  • Use a large tack weld or change in electrode angle
• Electrode Angle:

  • The angle that the electrode departs from the surface of the metal
  • Leading angle pushes the molten metal and slag ahead of the weld
  • Trailing angle pushes the molten metal away from the leading edges of the molten weld pool toward the back where it is solidified
• Common Causes and Remedies for Weld Defects:

  1. Arc Blow:

  • Caused by magnetic forces present in DC building up lines of magnetism around the arc, causing it to blow wildly forward or outside and spatter badly
  • Major problem areas: thick plates, corners, deep groove, start, and finish of joints
  • Reduce current or change to suitable polarity
  • Change current to AC
• 2. Pinholes and Porosity:

  • Caused by long arc length and traveling too fast
  • Other causes: faulty electrodes, incorrect polarity, base metal surface conditions, high sulphur, and impurities
  • Use shorter arc length and keep the puddle molten for a longer period
  • Use dry electrode and clean the base metal surface
• 3. Undercutting:

  • Caused by too high current, too long arc length, improper electrode angle manipulation, or too fast welding speed
  • Reduce current and shorten arc length
  • Use smaller diameter electrode
  • Change electrode angle
• 4. Spatter:

  • Caused by too high current or too long arc length
  • Reduce current
  • Shorten arc length
• 5. Incomplete Penetration:

  • Caused by faulty joint design, insufficient welding current, large electrode used, or too fast welding speed
  • Check the joint carefully, including root opening, root face dimension, and groove force angle
  • Increase weld current
  • Reduce welding speed
  • Use smaller diameter electrode
• Electrons from water molecules are excited to higher energy levels during photosystem II (PSII) and then transferred through an electron transport chain.
• This process generates ATP and NADPH, which are used in the Calvin cycle.