General Properties of Titanium Alloys

Titanium, though discovered as an element in 1791, commercially produced titanium has been available only since the 1940s, so it is among the newest of engineering metals. Titanium can be the answer to an engineer’s prayer in some cases. It has an upper service temperature limit of 1200 to 1400°F (650 to 750°C), weighs half as much as steel (0.16 lb/in3 {4429 kg/m3}), and is as strong as a medium-strength steel (135 kpsi {930 MPa} typical). Its Young’s modulus is 16 to 18 Mpsi (110 to 124 GPa), or about 60% that of steel. Its specific strength approaches that of the strongest alloy steels and exceeds that of medium-strength steels by a factor of 2. Its specific stiffness is greater than that of steel, making it as good or better in limiting deflections. It is also nonmagnetic.

Some Commonly Used Terminology for Six Sigma (A - L) - 1

This introductory article provides just a glimpse of Six Sigma and it is not a comprehensive one. It is recommended for the readers to explore other resources available on the web to collect more information on Six Sigma.

"As Is" Process Map - It depicts a process as it is, currently. "As is" process maps are usually characterized by several input options, bottlenecks and multiple handoffs, inspections and rework loops.

"Should be" Process Map - A depiction of a new and improved version of a process, used in DMAIC and iDMAIC projects, where all non-value-added steps are removed.

General Properties of Aluminum and Aluminum Alloys


Aluminum is the most widely used nonferrous metal, being second only to steel in world consumption. Aluminum is produced in both “pure” and alloyed forms. Aluminum is commercially available up to 99.8% pure. The most common alloying elements are copper, silicon, magnesium, manganese, and zinc, in varying amounts up to about 5%. The principal advantages of aluminum are its low density, good strength-to-weight ratio (SWR), ductility, excellent workability, castability, and weldability, corrosion resistance, high conductivity, and reasonable cost. Compared to steel it is 1/3 as dense (0.10 lb/in3 versus 0.28 lb/in3), about 1/3 as stiff (E = 10.3 Mpsi {71 GPa} versus 30 Mpsi {207 GPa}), and generally less strong. If you compare the strengths of low-carbon steel and pure aluminum, the steel is about three times as strong. Thus the specific strength is approximately the same in that comparison. However, pure aluminum is seldom used in engineering applications. It is too soft and weak. Pure aluminum’s principal advantages are its bright finish and good corrosion resistance. It is used mainly in decorative applications.

General Properties of Steel Alloys

Cast Steels

Cast steel is similar to wrought steel in terms of its chemical content, i.e., it has much less carbon than cast iron. The mechanical properties of cast steel are superior to cast iron but inferior to wrought steel. Its principal advantage is ease of fabrication by sand or investment (lost wax) casting. Cast steel is classed according to its carbon content into low carbon (< 0.2%), medium carbon (0.2–0.5%) and high carbon (> 0.5%). Alloy cast steels are also made containing other elements for high strength and heat resistance. The tensile strengths of cast steel alloys range from about 65 to 200 kpsi (450 to 1380 MPa).

General Properties of Cast Iron Alloys

Cast Iron

Cast irons constitute a whole family of materials. Their main advantages are relatively low cost and ease of fabrication. Some are weak in tension compared to steels but, like most cast materials, have high compressive strengths. Their densities are slightly lower than steel at about 0.25 lb/in3 (6920 kg/m3). Most cast irons do not exhibit a linear stress-strain relationship below the elastic limit; they do not obey Hooke’s law. Their modulus of elasticity E is estimated by drawing a line from the origin through a point on the curve at 1/4 the ultimate tensile strength and is in the range of 14–25 Mpsi (97– 172 MPa). Cast iron’s chemical composition differs from steel principally in its higher carbon content, being between 2 and 4.5%. The large amount of carbon, present in some cast irons as graphite, makes some of these alloys easy to pour as a casting liquid and also easy to machine as a solid. The most common means of fabrication is sand casting with subsequent machining operations. Cast irons are not easily welded, however.

Some Important Concepts in Mechanics of Material

Mechanics of material, also known as strength of material, is a subject which deals with the behavior of solid objects subject to stresses and strains. The complete theory began with the consideration of the behavior of one and two-dimensional members of structures, whose states of stress can be approximated as two dimensional, and was then generalized to three dimensions to develop a more complete theory of the elastic and plastic behavior of materials. An important founding pioneer in mechanics of materials was Stephen Timoshenko.

Defect Metrics - Six Sigma Concept

Lets define two terms before going forward:
  • In Six Sigma, a defect is defined as anything outside of customer specifications.
  • In Six Sigma, an opportunity is the total quantity of chances for a defect.
This article provides a list formula normally used to measure different metrics related to Six Sigma defects.

Types of Heat Exchangers

heat exchanger is a system used to transfer heat between two or more fluids. Heat exchangers are used in both cooling and heating processes. There are different types of heat exchangers

1. Double-pipe (pipe-in-pipe) heat exchanger - simplest type of heat exchanger consists of two concentric pipes of different diameters. Following two types of flow arrangement are possible

Types of Steel and its Manufacturing

Steel is an alloy of iron and carbon, with carbon content up to a maximum of 1.5%. Most of the steel produced now-a-days is plain carbon steel or simply carbon steel. Steel is divided into the following types depending upon the carbon content:
  • Dead mild steel — up to 0.15% Carbon
  • Low carbon or mild steel — 0.15% to 0.45% Carbon
  • Medium carbon steel — 0.45% to 0.8% Carbon
  • High carbon steel — 0.8% to 1.5% Carbon

Inspection Methods to Find Defects in Casting

In casting process, first few castings will be inspected dimensionally and the pattern is qualified afterwards, only few random inspection will be done. Every casting must be inspected to find out the defects in casting process.

Different methods of inspection to find out defects in casting process are discussed below

  • Radiographic Examination
  • Ultrasonic inspection
  • Visual Inspection
  • Hydrostatic Pressure Test
  • Magnetic Particle Inspection
  • Dye Penetrant Inspection
  • Coin Testing