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 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.

Effects of Welding on Your Eyes?

Between UV radiation and flying debris, welding can certainly cause damage to your eyes, but only if you don’t observe the correct safety protocol. Since 25% of all welding injuries are eye-related, proper eye protection on the job is a serious issue.

The good news, though, is that most of these eye injuries are preventable, and the bulk are also reversible. To put that into perspective, fully 95% of welders sustaining eye injuries are back at work within a week, while over 50% return within two days.

Type of Loads used in Engineering Mechanics

Different types of loads  in engineering mechanics are compression, tension, torsion and bending.

Compression:

Compression loading is an effect in which the component reduces it size. During compression load there is reduction in volume and increase in density of a component.

Tension:

Tension is the act of stretching rod, bar, spring, wire, cable etc. that is being pulled from the either ends.

Torsion:

Torsion is the act of twisting of a rod, wire, spring etc. about an axis due to applied couple (torque).

Bending:

Bending is act of changing component from straight form into a curved or angular form.

Types of Mechanical Forces

A force exerted on a body can cause a change in either the shape or the motion of the body. The unit of force in SI system is the newton (N) and Dyne. The unit of force in USCS is pound-force. No solid body is perfectly rigid and when forces are applied to it, changes in dimensions occur. Such changes are not always perceptible to the human eye since they are negligible. For example, the span of a bridge will sag under the weight of a vehicle and a spanner will bend slightly when tightening a nut. It is important for civil engineers and designers to appreciate the effects of forces on materials, together with their mechanical properties of materials.

Application of Superchargers

Super charger acts as an air compressor. It is used to increase the density and pressure of the air that is supplied to the internal combustion engine. In the engine, during the intake of the cycle it takes more oxygen and burn more fuel to accomplish the work. This is due the power increase.

By using the belts, gears, shafts, chains all of these are connected to the engines crank shaft to produce super charge.

We can see two types of the super chargers. To that matter after super charging, the air enters into the engine. After compression the pressure in the air is compressed and it super charges the system by 1.5 to 2 times to increase the entry of the pressure.

Forging Process

 Forging process is perhaps the oldest metal working process and was known even during prehistoric days when metallic tools were made by heating and hammering.

Forging is basically involves plastic deformation of material between two dies to achieve desired configuration. Forging is carried out as open die forging and closed die forging depending upon complexity of the part.

In open die forging process, the metal is compressed by repeated blows by a mechanical hammer and shape is manipulated manually.

In closed die forging, the desired configuration is obtained by squeezing the work-piece between two shaped and closed dies.

In forging process the forces are applied on the raw material such that the stresses induced are greater than yield and less than ultimate so that material is experiencing permanent deformation (plastic) to get required shape. But in forging operation force applied can be either continuous or intermittent impact loads.

Types of forging methods:

1. Based on the method of force application

1.      Hand forging (Drop hammer type)

2.      Machine forging (Mechanical or hydro-static forging)

A summary review of "Plastic Strength of Connection Elements" by Dowswell, B. (2015)

1. Abstract:

Many connection elements are modeled as rectangular members under various combinations of loads. The traditional method of combing loads using beam theory needs to be updated to fulfill the strength design philosophy due to the fact that the strength design is now used for steel members and connections. This paper has reviewed existing equations on the plastic interaction of rectangular members and has also provided new derivations where existing research is not available. Under any possible loading combination, an interaction equation is developed for strength design of rectangular connection elements.

Lateral torsional buckling of anisotropic laminated composite beams subjected to various loading and boundary conditions

H. Ahmadi

Abstract

Thin-walled structures are major components in many engineering applications. When a thin-walled slender beam is subjected to lateral loads, causing moments, the beam may buckle by a combined lateral bending and twisting of cross-section, which is called lateral-torsional buckling. A generalized analytical approach for lateral-torsional buckling of anisotropic laminated, thin-walled, rectangular cross-section composite beams under various loading conditions (namely, pure bending and concentrated load) and boundary conditions (namely, simply supported and cantilever) was developed using the classical laminated plate theory (CLPT), with all considered assumptions, as a basis for the constitutive equations.

Buckling of such type of members has not been addressed in the literature. Closed form buckling expressions were derived in terms of the lateral, torsional and coupling stiffness coefficients of the overall composite. These coefficients were obtained through dimensional reduction by static condensation of the 6x6 constitutive matrix mapped into an effective 2x2 coupled weak axis bending-twisting relationship. The stability of the beam under different geometric and material parameters, like length/height ratio, ply thickness, and ply orientation, was investigated. The analytical formulas were verified against finite element buckling solutions using ABAQUS for different lamination orientations showing excellent accuracy. Link to the source.

Adhesion evaluation of glass fiber-PDMS interface by means of microdroplet technique

H. Ahmadi

Abstract

This research was intended to measure the interfacial shear strength between fiber/ matrix

systems and to investigate the relation between structure-mechanical properties and performance

of fiber/matrix systems. This work conducted a systematic study on model fiber/matrix systems

to enhance the fundamental understanding on how variation of polymeric compositions (and

hence, different structures), different curing conditions, and fiber surface treatments influence the

interactions between the fiber and matrix.

In order to measure the interfacial shear strength of fiber/matrix systems, the microdroplet

technique was used. In this technique a polymer droplet was deposited on a fiber in the

liquid state. Once the droplet was cured a shear force was applied to the droplet in order to

detach the droplet from the fiber. The amount of the force needed to de-bond the droplet was

directly related to the strength of the bonds formed between the fiber and matrix during the

curing process.

In addition, the micro-droplet technique was used to evaluate effects of different

crosslinker ratio of fiber/ matrix system and also to see if different curing conditions affect the

interfacial shear strength of fiber/ matrix system. Surface treatment was also conducted to

evaluate its effects on the interfacial shear strength of the fiber/ matrix system using microdroplet

technique.

The interfacial shear strength of fiber/ matrix system increased along with the increase of

crosslinker ratio to a limiting value, and it decreased as long as the crosslinker ratio increased.

Curing condition also caused the interfacial shear strength of fiber/ matrix system to increase

when it was cured at higher temperature. Fiber surface treatment exhibited a significant effect to

the interfacial shear strength as well as the fiber/ matrix contact angle measurement.

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